Title of Invention	" A METHOD FOR EXTENDING VLAN BRIDGING SEMANTICS AND AN APPARTUS FOR SENDING FRAMES IN BRIDGED, CRYPTOGRAPHIC VLANS"
Abstract	The invention comprises there extention of the XXXX VLAN bridge moded. The first ectention is the cryXXX graphic separation of VLANs over XXX links. A LAN segment type reffered XXX as an encapXXX LAN segment is introduced. An. frames or sucha segment are encapsulated according to an encryption and XXX scheme. The second extention is the: division of a trunk port into inbound and outbound ports. The third extention is a protocol that automatically XXX for each outbound port in a bridge VLAN. a set of LAN segment types for the port that minimizes the number of transfer between encapsulated and unencapsulated segments required to transport a frame in the bridge VLAN.

Title of Invention

" A METHOD FOR EXTENDING VLAN BRIDGING SEMANTICS AND AN APPARTUS FOR SENDING FRAMES IN BRIDGED, CRYPTOGRAPHIC VLANS"

Abstract

The invention comprises there extention of the XXXX VLAN bridge moded. The first ectention is the cryXXX graphic separation of VLANs over XXX links. A LAN segment type reffered XXX as an encapXXX LAN segment is introduced. An. frames or sucha segment are encapsulated according to an encryption and XXX scheme. The second extention is the: division of a trunk port into inbound and outbound ports. The third extention is a protocol that automatically XXX for each outbound port in a bridge VLAN. a set of LAN segment types for the port that minimizes the number of transfer between encapsulated and unencapsulated segments required to transport a frame in the bridge VLAN.

Full Text	Bridged Cryptographic VLAN BACKGROUND OF THE INVENTION TECHNICAL FIELD 5 The invention relates to VLANs, More particularly, the invention relates to a bridged cryptographic VLAN. DESCRIPTION OF THE PRIOR ART 10 Basic VLAN concepts Figure 1 shows a simple port-based VLAN 10, comprised of two VLANs, i.e. VLAN A 13 and VLAN B 15. The VLAN to which an unteggsd frame rceived at a port belongs is determined by the Port VLAN ID (PVID) assigned to the receiving port, or 15 by the VLAN ID (VID) associated with the link-layer protocol carried in the frame (see IEEE Std 802.1v-2001, Virtual Bridged Local Area Networks Amendmert 2: VLAN Classification by Protocol and Port). There must be a way lo convey VLAN information between the bridges 12, 14 because they are connected by a trunk link 16 Ihat can carry frames from more than one VLAN, A VLAN tag is added to every 20 frame lor this purpose. Such frames are called VLAN-tagged frames Trunk links A trunk link is a LAW segment used for VLAN multiplexing between VLAN bridges (see IEEE Std 802.1V-2001, Virtual Bridged Local Area Networks—Amendment 2: WO 2004/042984 PCT/US2003/034855 VLAN Classification by Protocol and Port). Every device attached to a trunk link must be VLAN-aware. This means that they understand VLAN rnembership and VLAN frame formats. All frames, including end station frames, on a trunk link are VLAN-tagged, meaning that they carry a non-null VID. There can be no VLAN- 5 unaware end stations on a trunk link. The trunk link 16 in Figure 1 is a multiplexed LAN segment shared by two bridges 12, 14. in general, many VLAN-aware bridges may be attached to a trunk link. 10 The access links 11 are LAN segments that do not multiplex VLANs. Instead, each access Jink carries untagged frames of VLAN-tagged frames belonging to a single VLAN. If frames are tagged then all frames on the segment carry the same V\|D and end stations on the LAN segment must be VLAN aware. 15 Various limitations are encountered with the current state of VLAN art. One problem is that of cryptographic separation of VLANs over trunk finks. The Introduction of a schema to solve such probiem Use If raises the issue of efficient frame transfer between encrypted and unencrypted LAN segments which represent a stngle VLAN, 20 SUMMARY Of THE INVENTION The invention comprises Tnree extensions of Ihe IEEE 8D2.1Q VLAN bridge model (see IEEE Sto 802.1Q-1998, IEEE Standards for Local and Metropolitan Area Networks; Virtual Bridged Local Area Networks) . The first extension is the 2 WO 2004/042984 PCT/US20O3/034855 Cryptographic separation of VLANs over trunk links, A new LAN segment typer referred to herein as the encapsulated segment type, is introduced. Air frames on such a segment ars encapsulated according lo an encryption and authentication- code scheme. The second extension is the division of a trunk port into inbound and 5 outbound tranks ports. Thethird extension is a protocol, referred to herein as the Transfer Point Protocol (TPP), that automatically infers for each outbound trunk port in a bridged VLAN, a set of LAN segment types for the port that minimizes the number of transfers between encapsulated and unencapsulated segments required to transport a frame in the bridge VLAN, 10 BRIEF DESCRlPTION OF THE DRAWINGS Figure 1 is a block schematic diagram showing a port-basert VLAN; 15 Figure 2 is a block schematic diagram showing a bridged cryptographta VLAN according to the invention; Figure 3 is a flow diagram showing construction of a forwarding set according to the invention; 20 Figure 4 is a block schematic diagram showing a bridged cryptographic VLAN wrth two wireless trunk links according to the invention; Figure 5 is a block schemattc diagram showing a symmetric labeling of outbound ports in a bridged cryptographic VLAN according to the invention; 3 WO 2004/042984 PCT/CA2003/034855 Figure 6 is a block schematic diagram showing an asymmetric labeling of outbound ports in a bridged cryptographic VLAN according to the invention; Figure 7 is a block schematic diagram showing a purely encapsulated trunk in a bridged cryptograph VLAN according to the invention; 5 Figure 6 is a flow diagram showing JPP message exchange when Bridge 1 of Figure 7 initiates an announce frame for the VLAN according to the invention; Figure 9 is a block schematic diagram showing a labeling of the outbound ports according \o the invention, after swapping Bridges 1 and 2 in Figure 7; and Figure lo is a biock schematic diagram showing a lebeling of the outbound ports, 10 according to the invention, in a bridged cryptographic VLAN containing a bridge with three trunk ports. DETAILED DESCRIPTION OF THE INVENTION 15 LAN segment types Tnree types of LAN segments represent a VLAN: untagged, tagged, and encapsulated segments. The IEEE 802 to standard addresses only tagged and uritaggecf segment types (sea IEEE Std 802.1Q-1998, IEEE Standards for Local and 20 Metropolitan Area Networks: Virtual Bridged Local Area Networks). The standard specifies bridging semantics only for the transfer of traffic between tagged and untagged segments representing the same VLAN. The invention provides a technique that extends the bridging semantics to include transferring traffic between 4 WO 2004/042984 PCT/US2003/034555 an unencapsulated segment (tajgged or untagged ) and an encapsulated segment of the same VLAN, In general, arty number of LAW segment types can be introduced, There is one frame type for each type of segment representing a VLAN. There are 5 three kinds of frames tn a bridged, cryptographic VLAMi untamed, VLAN-tagged also referred to as tagged), and encapsulated. Thefirst two frarne types are those of the IEEE 802,1Q standard (see IEEE Sid 802,1 Q-1998, IEEE Standards tor Local and Metropolitan Area Networks; Virtual Bridged Local Area Networks). An encapsulated frame is cryptographioaily encapsulated. Every eneapsulated frame 10 also has a VLAN teg. The tag, however. is different from the tag used within tagged frames belonging to the VLAN. Associated with every VLAN are two unique VLAN tags, ViD-T (used within lagged frames of the VLAN) and VID-E (used within encapsulated frams of the VLAN). 15 For each VLAN, there is a unique security association comprising a cryptographic authentication code key for checking the integrity and authenticity of frames that are tagged as belonging to the VLAN, and a cryptographic key for ensuring the privacy of all frames belonging to the VLAM, 20 The preferred encapsulation scheme Is an "encrypt-then-MAC" scheme, In this scheme, the data pay load ot a frame Is encrypted and then a message authentication code is computed over the restating ciphertexl and the frame's sequence number- This schema has two major advantages: It facilitates forward error correction when used with certain block ciphers and modes Of operation and it 25 permits frame authentication without decryption, 5 WO 2004/042984 PCT/CA2003/034855 A tagged sel, an untagged set. and an encapsulated set of parts is associated with each VLAN, The security association for a VLAN may be used to verify the authenticity and integrity of every trame tagged as belonging to the VLAN, and 5 received at a porr in the VLAN's encapsulated set. The ingress-filtering rule for the port determines whether verification occurs. The association may also be used to encapsutete lagged and untged frames belonging to the & VLAN cryptographically before sending them from a port in the VLAN's encapsulated set, 10 Trunk ports Every trunk port has an Inbound and an outbound port. A trunk link between two trunk ports P1 and P2 connects the inbound port of P1 to the outbound port of P2, and the outbound port of P1 to the inbound port of P2. Therefore 'he sets of LAN 15 segment types to which an inbound port betongs are exactly those of the outbound port lo which it is connected. So, if is sufficient to assign only outbound parts to sets ot LAN segment types in order to completely assign alt trunk ports in a bridged VLAN to sets of LAN segment types 20 The inbound an outbound ports of a trunk pon can belong to different sets of LAN segment types. For instance, the outbound port of a trunk can belong to a VLAN's tagged set, antf the inbound port to its encapsulated sei, tn which case, only encapsulated frames of the VLAN are received on the inbound port, and onty tagged frames are ever sent from the outbound port, 6 WO 2004/042984 PCT/US2003/034855 Unlike an access port the inbound of outbound port of a trunk port can belong to both the tagged and encapsulated sets of a VLAN simultaneously. The division of a trunk port into inbound and outbound ports is absent in the 802- 1Q 5 standard (see IEEE Std 802.1 Q-1993, IEEE Standards for Local and Metropolitan Area Networks: Virtual Bridged Local Area Networks) where, in effect, the inbound and outbound ports are the same port. Inbound and outbound frame types are therefore always the same for a given trunk port in 802.1Q. 10 Figure 2 illustrates a bridged cryptographic VLAN. Ports P1 (20) and P2 (21) are access ports, one for VLAN A 26. ancf the other for VLAN B 29, VLANs A and B having access links 30, 31. A trunk link 16 connects the two bridges 12a, 14a via trunk ports P3 (22) and P4 (23). P3 has inbound port P3, and outbound port P3a P4 has inbound port P4, and outbound port P40 . P4, is connected to P3XXX and P40 is 15 connected to P31. Frames received at P4 arrive on inbound port P41 and those sent out P4 leave via outbound port P4O. Frames received at P3 arrive on inbound port P3i arrd those sent out P3 leave via outbound port P3 Ports P5 (24) and P6 (25) are attached to wireless access links 30. In the preferred 20 embodiment, they are actually virtual ports that share a single radio interface (access point) through which frames are sent and received via RF. VLANs A 28 and B 29 can be represented by different encapsulated segments even though they share the same RF medium. An end station in VLAN; for exampleT can receive but not decipher any frame belonging to VLAN 8. Therefore, distinct access links 32, 33 are 25 shown for A and 6 even though their physical separation is only cryptographic. 7 WO 2004/042984 PCT/US2003/034855 Suppose P1 receives only unissued frames, and P2 only tagged frames. Further, suppose the trunk link carries tagged frames in both directions, and the wireless access links only encapsulated frames, Then for VLAN A, the untagged set is {Pi}, 5 the tagged set Is {P30 P30 P40 P4, } and the encapsulated set is {P5}: and for B the sets are { } { P2, P30 P3r, P40, P4,}, and { P6 } reapectively. In the ingress filtering rule at P5 specifies authenticity checking, then a frame received at P5 is authenticated using the security association for VLAN A. If 10 successful, then the frame is determined to be a member Of the encapsutated segment for A. Suppose the frame must be forwarded to P4, Then Bridge 2: decapsulates the frame using the same security association. The bridge forwards the decapsulated frame to P40 with its tag repraced by A-T, thereby transferring the frame frorn A's encapsulated segment to its tagged segment. Conversely, frames 15 arriving at P4: and destined tor P5 are encapsulated using the security association for A. Tag A-T is replaced by A-E, which transfer the frame from As tagged segment to its encapsulated segment. There are many variations of the example in Figure 2, For instance, it may be 20 desirable to protect traffic on VLAN B only. In this case, P5 does not belong to the encapsulated set for A, Only frames received at P6, i.e. frames tagged with B-E, are authenticated, and only B-tagged frames received at P4i and destined for P6 are encapsulated. 8 WO 2004/042984 PCT/US2003/034855 Bridging semantics Consider a VLAN bridge having multiple ports. Suppose a frame is received at port P- It is assigned 1o a VLAN In one of several ways. If P is a trunk port, then the 5 franw must carry a VLAN tag of the form VID-T or VlD-E, each of which identities, a VLAN, namely VID. Otherwiser the frame is diseased. If P is not a trunk port, then either port or protocol-based VLAN classification can be used to assign the frame to a VLAN (see IEEE Std 802.1v-2001, Virtual Bridged Local Area Networks—Amendment 2: VLAN Classification by Protocol and Port). 10 Ingress filtering If P is a trunk port and is not in the tagged or encapsulated sets for VID, then the frame is discarded. The ingress-filter rule for a port may specify authentication and integrity checking for certain VLANS. If P is a port whose ingress filter rule requires 15 authentication and integrity checking for the VLAN VlD, then the frame received at P must have a VLAN tag VID-E. Otherwise, the frame is discarded. In 1he preferred emboiment, an authentication code is computed over the received frame's ciphertext and sequence number using the security association for VID. If it does not match, the received authentication code In the frame, then the frarm Is discarded. 20 otherwise, tha frame is judged to belong to the encapsulated segment for VlD. If P is not in the tagged set for VlD, but it is attached to a VLAN-iagged access link, then the received frame is discarded. 9 WO 2004/042984 PCT/US2003/034855 Forwarding process The forwarding process begins by corisvutf ing the target port set O. This is the set of ports to whicn a frame belonging to a particular VLAN rnust be forwarded. 5 Suppose a if farm received al port P belongs to the VLAN SAD. tf the fams must be flooded then Q contains any ou(bound or access port that is a member of the tagged, untagged or encapsulated sets for VID. The next step is to shrink Q if. and only if. P is an inbound port of a trunk that belongs to both the tagged and encapsulated sats of VID. In this case, every port in the encapsulated set of VID that does not belorig 10 to the tagged set of VID is ramovecf from a if the received frame is a tagged (name, or every port in ttre tagged or untagged set of VID that does not be!ong to the encapsulated set of VID is removed from Q if the received frame is encapsulated. Bacause the inbound port belongs to both sets of LAN segmenrt types fO VlDr the inbound port must receive a frame of each LAN segment type, and therefore 15 shriking the target port set is justified. The Transfer Point Protocol has the property that it guarantees shrinking never results in an empty target port set. Shrinking to an emptytarget set implies the bridge received a fram that it has no reason to receive. The next step in the forwarding process is to construct a forwarding set for the 20 received frame. This is the set of frames to be forwarded as a result ot receiving the frame belonging to VID at port P, These are tne frames necessary lo transfer traffic from one LAN segment of the VLAN to another. Tne table shown in Figure 3 Is used to construct forwarding sets. The frame received at P belongs to a Kind K of LAN segment for VID (tagged, untagged, of encapsulated). Likewise, every pont in Q 25 belongs to a kind at LAN sggment, the kind of port set to which it belongs for VID. 10 WO 2004/042984 PCT/US2003/034855 Trunk ports may have two KINDS OF sets: tagged and encapsulated, For every port q in Q, add a frame to the forwarding set according to rule (K, K) in me table of Figure 3, where K' is a kind of port set to which q belongs for VID. 5 The rules for constructing the forwarding set for a received frame are as follows: (1) Add received frame to forwording set. (2) Add VLAN tag VlD-T to received frame. add the result to forwarding set. 10 (3) Received frame is cryptographteally encapsulated using the security association for VlD resulting frame is VLAN tagged with VID-E and added to forwording set 15 (4) Remove VID-T fromreceived frame; add urtagged frame to forwording set (5) Receded frame's ciphertext is decrypted using the securty association for VID; resulting frame is untagged and added to forwarding set. 20 (6) Received frame's ciphertext is decrypted using the security association for VID; resulting frame is tagged wilh VID-T and added to forwarding set. 11 WO 2004/042984 PCT/US2003/034855 In the presently preferred embodiment there can be at most three frames in any forwarding set, corresponding to me three different kinds of LAN segment that can represent a VLAN. The forwarding process forwards the frames of the forwarding set as follows 5 • The forwarding process queues for transmission at each port in Q that belongs to the untagged set for VID, the untagged frame, if any, in the forwarding SET. • The forwarding process queues for transmission at each port in Q lhaf belongs to 10 the tagged set for VID, the VLAN -tagged frame, if any, in the forwarding set • The forwarding process queues tor transmission at each port in Q that belongs to the encapsulated set for VID, the encapsulated frame, if any, in the forwarding set 15 Frame transfer Within a bridged, cryptographic VLAN. steps are taken to eliminate redundant transfers between LAN segments representing the same VLAN. For instance, it is desirable to avoid transfeming an unencapsulated frame to a VLAN's encapsulated 20 segment more than once in a bridged VLAN because each transfer requires encryption. Encapsulation should be done once and shared by all egress ports that belong to the VLAN's encapsulated set across ad bridges. Similarly, it is desirable to avoid repeated decapsulation across bridges because each calls for decryption 12 WO 2004/042984 PCT/US2003/034855 For instance, consider the bridged LAN in Figure 4. Suppose the ports of Bridges 1 (41) and 2 (42) to which the wireless trunk links 43 are attached belong to the encapsulated set for VLAN & 44. if the trunk link 45 carries only VLAN-tagged 5 frames, then frames belonging to VLAN B that are received at Bridge 1 rnust be encapsulated at Bridges 1 and 2. However, if the trunk link carries encapsulated frames then encapsulation need only be done at Bridge 1 and shared with Bridge 2. There are also situations where ancapsulaiion can be done too early in a bridged 10 LAN, forcing encapsulated frames to be sent over trunk links unnecessarily. There Is a transfer point for encapsulation and (decapsulation for each VLAN that.minimizes cryptographic operations. The Transfer Point Protocol (discussed below) infers this transfer point between segments. Transfer Point Protocol 15 A minimum spanning tree algorithm can reduce any bridged LAN to a spanning tree whose nodes are the bridges and whose edges are trunk links. A spanning tree induces a partial order or bridges. For instance, we can taka as the partial order B1 20 the root of the spanning tree. The set of bridges together with the partial order defines a complete, partially ordered set. Every nonempty subset of bridges has a least upper bound. 13 WO 2004/042984 PCT/US2003/034855 Consider frames received at the root of the spanning tree. The least upper bound of all bridges requiring a received frame of a VLAN to belong to one of iha LAN segments representing the VLAN is the transfer point for converting received frames to frames for that LAN segment 5 The Transfer Point Protocol (TPP) comprises two link-layer protocols, TPP-T for adding outbound Trunk ports to thh tagged set of a VLAN, and TPP-E for adding outbound trunk ports to the encapsulated set of a VLAN. The trunk ports are across al lbridges that bridge the VLAN- For example, TPP-E determines that the outbound 10 trunk port connecting Bridge 1 to Bridge 2 in Figure 4 must be a member of the ancapsulated set for VLAN B. That way the wireless trunk port at Bridge 2 can share encapsulations pefformed by Bridge 1 for its outbound wireless trunk port. TPP assumes that every access link port has been assigned to the tagged, 15 uataggad, or encapsulated set tor a VLAN prior to execution because it uses this infortnation to infer the sets to which outboond trunk ports in the bridged VLAN belong. TPP-E can assign an outbound trunk port to the encapsulated se oi a VLAN, while TPF'-T can assign the same outbound port to the tagged set of the VLAM. 20 TPP has two frams types, the announce frame, and the reply frame. Each ct these frames contains a VLAN ID and a source bridge routing path, where each entry in the path is a unique pair containing a bridge MAC adress and three bits, one bit for each LAN segment type, i.e. tagged, untagged, and encapsulated. The tagged bit is 25 high It and only if ihe bridge addressed in the pair has an access port in the tagged 14 WO 2004/042981 PCT/US2003/034855 set of the VLAN named in the frame. Tire untagged and encapsulated bits ars set likewise, A bridge sends a TPP announce frame, e.g a GARP POU, to a TPP group address, 5 e.g, a GARP application address, through each of its outbound trunk ports for every VLAN known to it. When a bridge receives an announce frame, it appends to the right of the path the pair for itself regarding the named VLAN received, and forwards the frame to each of its enabled, outbound trunk ports except the receiving trunk port, if it has no other such ports, then il sends the final routing path and received 10 VID in a TPP reply frame to the MAC address thai precedes it jn ihe routing path. The originating bridge of an announce frame creates a path consisting only of a pair for itself. When a bridge receives a TPP reply frame on an inbound trunk port, it forwards the reply frame to the bridge MAC address thai precedes it in the path. If ihere is none, the frame is discarded. 15 TPP-E When a bridge receives a TPP reply frame on a trunk port, it adds the trunk's outbound port to the encapsulated set for the VID in the frame if, and only if, it is followed by a bridge B in the routing path whose encapsulated bit is high, and either 20 a) the receiving bridge has a tagged or untagged access port for the VID and no bridge after it in the routing path, up to and including B, has a high tagged or untagged bit; or b) the receiving bridge has an encapsulated access port for the VID, or is preceded by a bridge in the routing path with a high encapsulated bil. 15 WO 2004/042984 PCT/US2003/034855 TPP-T When a bridge receives a TPP reply frame on a trunk port, it adds the trunk's outbound part lo the togged set tot the VlD in tine frame if, and only if it is fallowed 5 by a bridge B in the routing path whose tagged or urrtagged bit is high, and either a) the receiving bridge has an encapsulated access port for the VlD and no bridge after it in the routing path, up to and including B, has a high encapsulated bit; or 10 b) the receiving bridge has a tagged or untagged access port lor the VlD, or is preceded by a bridge in the routing path with a high tagged or untagged bit Example 15 Example 1 Consider bridging a single VLAN- Each access porttherefore is assumed to belong to this VLAN, Thus, VLAN labeling of ports is omitted in the examples. Instead, the 20 outbound trunk ports are labeled with LAN segment types, i.e. T (tagged), U (untagged). and E (encapsulated), U an outbound port is labeled with U, for example, then the port belongs to the untagged set of ihe VLAN, 16 WO 2004/042984 PCT/US2003/034855 initially, every access part, is labeled according to the kindof set to which the port belongs for the VLAN. Trunk ports are initially unlabeled. jt is the job of TPP ro infer labels for them. Figure 5 shows a bridging of a VLAN 50 where two bridges 51, 52 are connected by a trunk 53. Each bridge has two access ports. Because each 5 Bridge has both jntagged and encapsulated access ports, TPP infers that both outbound ports of the trunk belong to the tagged and encapsulated sets of the VLAN. Each inbound port also belongs to these sets. 10 Each outbound port is a member of the tagged set per rule TPP-T (b). Each bridge infers this fact when it initiates a TPP announce frame. Therefore, both the encryption and decryption done by each bridge is shared with the other. Example 2 15 In Figure 6, Bridge 1 (61) has an untagged access port and Bridge 2 (62) has an encapsulated access port. Therefore, the outbound port 63 of Bridge 1 is a member of the encapsulated set per rule TPP-E (a) whereas the outbound port 64 of Bridge 2 is a member of the tagged set per rule TPP-T (a), 20 Example 3 Figure 7 illustrates a purely encapsulated trunk link. All frames over the link are 25 encapsulated, however, no encryption is done at Bridges 2 or 3, 17 WO 2004/042984 PCT/US2003/034855 Figure 8 shows the TPP message exchange between Bridges t (71), 2 (72), and 3 (73) when Bridge 1 (71) Of Figure 7 initiates an annouce frame for the VLAN, which we assume for the example is named "B" 5 Example 4 If Bridges 1 (71) and 2 (72) in figure 7 are interchanged, me result is the bridged cryptographic VLAN of Figure 9. 10 Example 5 Figure 10 shows a bridge 82 with three trunk ports, each connected to another bridge 81, 83, 84. The outbound port of the trunk from Bridge 4 (84) belongs to the tagged and encapsutated sets, whereas the outbound port of Bridge 2 (82) that is 15 connected to the inbound port of Bridge 4 is only a member of the encapsulated set TPP may run repeatedly to inter changes in transfer points, How frequently it runs and the number of bridges it affects depends on the displacement of access links, For example, it an end station is wireless, then movement of the station with respect 20 to the bridged LAN can result in its encapsulated access link being relocated. Unti\| TPP is rerun, there may be redundant transfers for a VLAN. A bridged VLAN may consist of bridges that do not participate in TPP. !n general, there may be one or more cryptographic VLAN bridges with trunk ports connected to 25 legacy VLAN bridges. If each such itrunk port is viewed instead as a coflection of virtual, tagged access ports, one port tor each VLAN tag that can be sent over the 18 WO 2004/042984 PCT/US2003/034855 trunk, then TPP can still be run to infer transfer points among participating bridges. However, there may be redundant transfers across the entire bridged LAN. For exampler if a nonparticipating core switch were to separate two cryptographic VLAN bridges, each having an access port in the encapsulated set ot the same VLAN, then 5 traffic between these encapsulated segments would be decrypted upon entry 16 the core and then re-encrypted after exiting. Observe that no encryption or decryption is needed if there are no access ports in the core that belong to the tagged or urnagged sets of the VLAN. In this case, TPP can treat the virtual access port for each VLAN Tag as an encapsulated access port rather than a tagged access port, Then all traffic 10 between the two encapsulated segments can traverse the core transparently as encapsulated frames because every encapsulated frame is a VLAN-tagged frame. Group security A cryptographic VLAN v is defined by a group of m stations in at has a unique security 15 association The association consisists of the following: a) an encryption Key Kv1 b) an authentication code key K' v1 c) a distribution key K"V1 and d) m random values RTL R2.....RXXX 20 The encryption key is a symmetric key used by v-aware bridges and stations of v to encrypt and decrypt frames belonging to v. All v-aware bridges, and stations of v, compute and verify authentication codes over encrypted frames of v using K'v There is one random value for each of the m stations. The /1h station of the group ' knows all m random values except RXXX. The m - 1 random values it knows are 19 WO 2004/042984 PCT/US2003/034855 communicated to it by a v-aware bridge. Privacy ot me random values is ensured by encryption using distribution key K"XXX while their authenticity is ensured by an authentication code computed over the resulting ciphertext using authentication code key K'v 5 Joining a cryptographic VLAN Joining a cryptographic VLAN is done with a two-step protocol: adding a new Station to tte group, and enabling all other stations in the group to eliminate the new station later A user's station joins a cryptographic VLAN v through a mutual authentication 10 protocol executed between the user, via the station, and an authenticates residing on a v-aWare bridge. If mutuat authentication succeeds, A secure eprremeral channel is created between the bridge and the new station to transfer Kv K'v and R1. R2 Rm securely trom the bridge to the station. Then the second step of the Join protocol executes, Otherwise, the protocol terminates immediately. In the second step, the 15 same v-aware bridge chooses a new random value Rm+1 for the new station. and distributes it to all v-aware bridges, and station comprising v, in a broadcast frame that is encrypted under K" v and carries an aulhentication code computed over the ciphertext using K'v The bridge then creates a new distribution key for v and distributes it to all v-aware bridges and to members of v, including the new station, in 20 a broadcast frame that is encrypted under K v and carries an authentication code computed over the ciphertext uaing K'v Although the new station can verify the authenticity of the broadcast containing its own random value Rm+1 it is unabfe to decrypt it because ft does not hold key K"v 20 WO 2004/042984 PCT/US22003/034855 Leaving a cryptographic VLAN A. subgroup of stations can simultaneously leave a cryptographic VLAN v, perhaps involuntary. Suppose stations 1....it of a group leave. When this happens, it is detected by a v-awara bridge which then announces the departure of stations 1,..., k 5 via a single broadcast frame that includes an authentication code computed over the frama using K'y The broadcast will notify every v-aware bridge and station in the group that stations 1,,,., k have left. Each such bnd§a and station then attempts to re key the encryption, authentication code, and distribution keys for vT each as a fundion of the old key and the random values R,,.,., Rk'. Every v-aware bridge and 10 all remaininig stations in v will share a now eecwity aesoiciation as a result, indudiifiig K fewer random vslues. Every v-aware bridge always has the current distribution key for v' unlika a station. So every such bridge always has the complete set of random values for any 15 subgroup that leaves v, thereby allowing it to always re key the keys for v. The Situation Is different for stations however Rekeying is a function of the random values for departing stations, values thai these stations do not have. Therefore, they are unable to rekey. Furthermore, forward secrecy is guaranteed, A departed station can never become a rnernber of v again as a result of subsequent rekey ings, 20 This is because rekeyiag is a function of ttis currerrt keys which means. that all Keys arrived at thereafter will always be a function of a random value unknown to the station. Only through rejoining vcan the station ever become a member of v again. Although the invention is described herein with reference to the preferred 25 embodiment, one skilled in the art will readiiy appreciate that other applications may 21 WO 2004/042984 PCT/US2003/034855 be substituted for those set forth here in without departing from Ihe split and scope of the present invention. Accordingly, the invention should only be limited by the Claims included below. AMENDED PAGE REPLACEMENT CLAIMS 5 1, A method for extending VLAM bridging semantics, comprising the steps of: providing an untagged frame and a tagged Frame in accorttence with tho IEEE 302 1Q VLAN bridge model; providing a cryptagraphlcally encapsulated frame, wherein every encapsulated frame has a VLAN tag that is different from a teg used within tagged 10 frames belonging to said VLAN; providing a. trunk port divided into inbound and! outbound trunk ports; providing one of said untagged. tagged, and encapsulated frame lype for each segment representing a bridged, cryptographic VLAN; and transfenring traffic between an unerrcapsulated segment (tagged or untagged) 15 and an encapsulated segment of a same VLAN. 2. The method of Claim 1, further comprising the step of: associating with every VLAN two unique VLAN tags, said two unique VLAN tags comprising VlO-T, which is used within tagged frame of said VLAN, and VID-E. 20 which Is used within encapsulated ffames of said VLAN. 3. The method of Claim 1. wherein for each VLAM, there is a unique security association comprising a comptographic authentication code key tor checking integrity and authenticity of frames that are tagged as belonging to sard VLAN, and a 25 cryptographic key for ensuring privacy of all frames belonging to said VLAN. 25 AMENDED PAGE 4, The method of Claim 1, wherein said encapsulated frame is encapsulated in accordance with an encrypt-then-MAC method, which com prises tho steps of: encrypting a data paytoad of a frame; and eorciputinig a message authentication code ovet a resulting dphedett. and said 5 frame's sequence number. 5. The method of Claim 1, wherein a tagged set, an untagged set, and an encapsulated set of ports ts associated with each VLAN. 10 6, The method of Claim 1, further comprising the step of: using a security association for a VLAN to verify authenticity aad integrity of every frame tagged as betonging to said VLAN, and received at a port in said VLAN's encapsutated set. 15 7. The method of Claim 6, further comprising the step of: providing an ingress-filtertng rule for said port to determine whether verification occurs. 8. The method of Claim 6, further comprising the step of, 20 using said association to encapsulate tagged and untagged frames bebng'ing to paid VLAN cryptographfcally before sending them from a port In said VLAN's eneapsulated set, 9. An apparatus for sending frames in bridged, crypto graphic VLANs, comprising: 25 at least two bridges 24 AMENDED PAGE a plurality of trunklinks wherein every trunk link of said trunk links is associated With the inbound trunk port of one bridge of said at least two bridges and the outbound trunk port of another bridge of said at feast two bridges; a plurality of access porte; 5 a plurality of access links wherein every access link of said access links is associated with one access port of said access ports; and means for nepreserting said VLANs by different encapsulated segments even though thay share a same medium, wherein physical separation of said VLANs is cryptographic 10 10. The apparatus of Claim 9, further comprising: an ingress-filtering rule associated with alt least one of said access ports for specifying authenticity checking,, wherein a frame received at said one of sard access ports is authenticated using a securty association for an associated VLAN; 15 wherein, if authentication successful, then said frame is determined to be a member of an encapsulated segment for said associated VLAM. 11. The apparatus of Claim 10, wherein said ingress -filterr ule associated with at least one of said access ports specifies authentication and Integrity checking for 20 certain of said VLANs. 12. The apparatus of Claim 11 r further comprising; an authentication code that is computed over a received frame's ciphertext end sequance number using said security association; 25 AMENDED PAGE wherein, ifsaid authenticate code does not match a received authentication code in said frame, then said frame is discarded; and wherein said frame is otherwise determined to belong to an encapsulated segment for an associated VLAN. 5 13, The apparatus of Claim 9, further comprising: one or more rules for constructing a target port set for a frame received at an inbound pert that belongs to the tagged and encapsulated sets off a VLAN; wherein , every port in the encapsulated set of said VLAN that is not a member 10 of trie tagged set of said VLAN is removed If satd frame is tagged; and wherein, every port in either the tagged or untaggod sets of said VLAN that is not a member of the encapsulated set of said VLAN is removed if said frame is encapsulated. 15 j4.The apparatus of Claim 9, further comprising; one or more rules for constructing a forwarding set for a received frame, which rules may comprise any of Ihe following: add a received frame to said forwarding set; add a VLAN lag to a received frame; add the resuft to said forwarding set; 20 a received frame is cryptographically encapsulated using a security association; a resulting frame is VLAN taggedand added to said forwarding set; remove a VLAN tag from a received frame; add an untagged frame to said Forwarding set; a veceived frame's ciphertext is decrypted using 3 security assciation: a 25 resulting frame is untagged and added to said forwarding set; and 26 AMENDED PAGE a received frame's ciphertext is decrypted using a security association; a resulting frame is tagged and added to said forwording set. 15, A method for forwarding frames of a forwardlag set that ia defined with respect to 5 the target port set far a received frame of a VLAN, comprising the steps of: queuing an untagged frame, if any, in said forwarding set. for transmission at every port in said target set that belongs to the untaggecf set for said VLAN; queuing an VLAN-tagged frame, if any, in said forwarding set. for transmission at every port in said target set that belongs to the tagged set for said VLAN; and 10 queuing an encapsulated frams, if any, in said forwarding set. for transmission at every port in said target set that belongs lo the encapsulated set for sprd VLAN. 16, A method for eliminating redundant transfers between LAN segments in a bridged, cryptographic VLAN, comprising the STEPS of: 15 avoiding transfer of an unencapsulated frame to a VLAN's encapsulated segment more than once in a bridged VLAN where each transfer requires ervcrypton; perforrnirig encapsufatbn once, said encapsulation being shared by all egress ports that belong to said VLAN's encapsulated set across all bridges; and 20 avoiding repeated decapsulation across bridges in said bridged VLAN where each requires decryption. 17 A method for determining optima transfer points between LAN segments representing a bridged, cryptographic VLAN, comprising the steps of: 27 AMENDED PAGE reducing any bridged LAN to a spanning tree whose nodes are said bridges and whose edges are trunk links 10 induce a partial order on sard bridges: wherein a least bridge is the root of said spanning tree; wherein the set of bridges together with a partial order define a complete, partsaily ordered set; and wherein every nonempty 5 subset of said bridges has a least upper bound; wherein said least upper bound of aJI bridges requiring a received frame of a VLAN to belong to one of said LAN segments representing said VLAN is an optimal transfer point for converting received frames to frames for that LAN segment; and deducing automatically, from an assignment of bridge access ports in said 10 bridged VLAN to said LAN segments, the smallest set of LAN segments that must be associated with a given outbound trunk port in order to bridge said VLAN. 18. An apparatus for implementing a transfer point protocol (TPP) in a bridged, cryptographic VLANT comprising: 15 at least two brid ges: a plurality of trunk links wherein every trunk link of said trunk links is associated with an inbound trunk port of one bridge of said at least two bridges and an outbound trunk port of-another bridge of said at least two bridges; a plurality of access ports; 20 a plurality ol accesslinks wherein every access Iink of said access links is associated with one access port of said access ports: and means for representing said VLANs by different entapsutated sertjmentes even though they share a same medium, wbere in physicaf separation of said VLANs is cryptographic, 28 AMENDED PAGE two Iink-layef protocols, a first link-layer protocol (TPP-T) for adding outbound ports to the tagged set of a VLAN. and a second link-layer protocol (TPP-E) for adding outbound ports to tfte encapsulated set of a VLAN; and wherein every access port is assigned to a tagged, untagged, or encapsulated 5 set for a VLAM prior to sxecution. 19. The apparatus of Claim 18, said transfer point protocol (TPP) further comprising: two frames types, one of said frame types comprising an announce frame. and a second of said frame types comprising a reply frame wherein each of said 10 frames contains a VLAN ID and a source bridge routing palh, where each entry in said path is a unique pair containig a bridge MAC address and three bits, one bit for each LAN segment type. wherein said tagged bit is high if andt only if a bridge addressed in, said pair has an access port in a tagged set of said VLAN named in said frame, and wherein said untagged and encapsulated bits are set likewise. 15 20. A transfer point protocol (TPP) in a bridged, cryptographic VLAN, comprising the steps of a bridge sending a TPP announce frame to a TPP group address through each of its trunk ports for every VLAN known to it 20 when a bridge receives an announce frame, said bridge appending to reserved routing path an entry for itself regarding the received VLAN ID. nnd forwarding said frame to each of its enabled, outbound Irunk ports except the receiving trunk port: wherein it said bridge has no other such trunk ports, then said bridge sending a final routing path and said received VLAN ID in a TPP reply frame 25 to the MAC address that precedes said bridge in said routing path: 29 AMENDED PAGE an originating bridge of an announce frame creating a path consisting only of an entry for itselt; when a bridge receives a TPP reply frame, said bridge forwarding said reply frame to the bridge MAC add ness that precedes said bridge ia said routing path; and 5 if there is none, discarding said frame. 21. The protocol of Claim 20, wherein when a bridge receives a TPP reply frame on an inbound trunk port, said bridge acids the outbound port corresponding to said inbound trunk port to line encapsulated set for the VLAN 10 to said frame if, and only 10 if, said bridge is followed by another bridge in said routing path with an encapsulated access port, and either: said bridge has a tagged or untagged access port for said VLAN ID and no bridge after ft in said routing path, up lo an including said other bridge, has a tagged or untegged access port; or 15 said bridge has an encapsutated access port for said VLAN ID, or said bridge is preceded by another bridge In said routing path with art encapsulated access port. 22. The protocol of Claim 20, wherein when a bridge receives a TPP reply frame on an in bound trunK port, said bridge adds the outbound port corresponding to said 23 inbound trunk port to the tagged set for the VLAN ID in said frame if, and only if. said bridge is followed by another bridge m said routing path with a tagged or untagged access port, and either, said bridge has an encapsulated access port for said VLAN ID and no bridge after it in said routing path, up to an including, said oiher bridge, has an encapsulated 25 access port; or 30 AMENDED PAGE said bridge has a lagged or untagged access port for said VLAN ID, or said bridge is preceded by another bridge rn said routing path with a tagged or untagged access port 5 23. The protocol of Claim 20, wherein the outbound port of a trunk port is treated as: a set of virtual, tagged access ports with one said tagged access port for each VLAN supported by said trunk port; a set of virtual, encapsulated success ports with ane said encapsulated access port for each VLAN supported by said trunk port; or 10 a set of virtual, encapsulated or virtual, tagged access ports with one said, ragged or encapsulated access port for each VLAN supported dy said trunk port. 24. A protocol or access link displacement In a bridged, cryptographic VLAN, comprising bridges that support encapsulated segments, said protocol comprising 15 the steps of: rccoyriizing an access port of a bridge of said bridged VLAN with which a displaced access link can be associated, wherein said access port may be, virtual and created automatically; automatically assigning said access port In a LAN segment type based an a 30 segment type of said displaced access link; and executing a transfer port protocol (TPP) for said bridged VLAN with said access port belonging to said assigned LJ\N segment type, 25. A method for establishing a group security association for a cryptographic VLAN 25 comprising m stations, comprising the steps.of: 31 AMENDED PAGE providing an encryption key K v, wherein said encryption key is a symmetric key useti by v-aware bridges and station of v to encrypt and decrypt frames belonging to v1 providing an authentication code key K¢ v, wherein all unaware bridges, and 5 station of v, compile and verify authemication codes over encrypted frames of v using K¢ v, providing a distribution key K¢¢ v; and providing m random values R1, R2,.... Rm, wherein there is one random value for each of said fn stations, wherein an ith station of said group knows all m 10 random values except Ri, wherein said m - 1 random vafyea that said ith station knows are communicated to it by a v-aware bridge; wherein privacy of said random values is ensured by errayption using said distribution Key K¢¢ v, while their authenticity is ensured by an authentication code computed over a resulting clphertext using said authentication code key K¢ v. 15 26. A method for joining an encapsulated segment of a cryptographic VLAN, compnsing the steps of: addivig a new statort to a group; and enabling all other stations in said group to eliminate said new station later 20 27, The method of Claim 26, said step of adding a new station to a group further comprisingthe step of: a user' s station joining a cryptographic VLAN v through a mutual authemication protocol executed between said user, via said user's station, and an 25 authentication residing on a v-aware bridge; 32 AMENDED PAGE wherein if mutual authentication succeeds, a SECURE ephemeral channel is created between said v-aware bridge and said new station to transfer an encryption key K v, an authentication code key K¢ v, and m random values R1, R2, ..., Rm securely from said v-aware bridge to said new station, in which case sard enabling 5 step executes."'. otherwise, said protocol terminates immediately. 23. The method of Claim 27, said sfep of enabling all other stations in said group to elimanate said new station later further comprising the steps of; 10 said v-aware bridge choosing a new random value Rrn+1 for said new station and distributing said new random value Rm+1 to all v-aware bridges, and stations comprising v, jn a broadcast frame that is encrypted under a distribution key K¢¢ v and that carries an airthentication code computed over ciphertext using K¢ v; said bridge then greatinig a new distribution key for v and ditributing said new 15 distribution key to all v-aware bridges and to members of vr including said new station, in a broadcast frama that is encrypted under K v and thai carries an authentication code computed over said crphertext using K¢v. 29, The method of Claim 281 wherein said new station can verify authenticity of a 20 broadcast containing its own random value Rm+1, but is unable to decrypt said broadcast because it does not hold key K¢¢v. 30. A method for leaving a cryptographic VLAN, comprising the steps of: detecting with a v-aware bridge a subgroup of stations 1...k simultaneously 25 leaving a cryptographic VLAN v XXX 33 AMENDED PAGE said bridge v-aware announcing the departure of said stations 1,.,., k via a single broadcast frame that comprises an authenlication code computed over said frame using an authentication code key K¢ v, wherein said broadcast notifies every v-aware bridge and station in group v that stations 1,..,k have left; 5 each such bridge and station then attempting to rakey encryption, authentication code, and distribution keys for v, each as a function ot an old key and random values R1...., Rk, and every v-aware bridge and all remaining stations in group v sharing a new security association as a result, comprising k fewer random values. 10 31 The method of Claim 30, wherein every v-aware bridge atways has a current distribution key for v, and wherein every v-aware bridge always has a complete set cf random values for any subgroup that leaves group v, thereby allowing it to always rekey the keys for 15 group v. 32. The method of Claim 30,wherein for station rekeying is a function of random values for departing stations that these stations do not have wherein said stations are unable to rekey, 20 33. The method of Claim 30, wherein a departed station can never become a member of group vagain as a rasult of subsequent rekeyings because rekeying is a function of current keys, and all keys arrived at there after are always a function or a random value unknown to said departed station. 25 34 AMENDED PAGE 34. The method of Claim 30, wherein a departed station can only become a member of v again by rejoining v, 5 35 The invention comprises there extention of the XXXX VLAN bridge moded. The first ectention is the cryXXX graphic separation of VLANs over XXX links. A LAN segment type reffered XXX as an encapXXX LAN segment is introduced. An. frames or sucha segment are encapsulated according to an encryption and XXX scheme. The second extention is the: division of a trunk port into inbound and outbound ports. The third extention is a protocol that automatically XXX for each outbound port in a bridge VLAN. a set of LAN segment types for the port that minimizes the number of transfer between encapsulated and unencapsulated segments required to transport a frame in the bridge VLAN.

Full Text

Bridged Cryptographic VLAN
BACKGROUND OF THE INVENTION
TECHNICAL FIELD
5
The invention relates to VLANs, More particularly, the invention relates to a bridged
cryptographic VLAN.
DESCRIPTION OF THE PRIOR ART
10 Basic VLAN concepts
Figure 1 shows a simple port-based VLAN 10, comprised of two VLANs, i.e. VLAN A
13 and VLAN B 15. The VLAN to which an unteggsd frame rceived at a port
belongs is determined by the Port VLAN ID (PVID) assigned to the receiving port, or
15 by the VLAN ID (VID) associated with the link-layer protocol carried in the frame (see
IEEE Std 802.1v-2001, Virtual Bridged Local Area Networks Amendmert 2: VLAN
Classification by Protocol and Port). There must be a way lo convey VLAN
information between the bridges 12, 14 because they are connected by a trunk link
16 Ihat can carry frames from more than one VLAN, A VLAN tag is added to every
20 frame lor this purpose. Such frames are called VLAN-tagged frames
Trunk links
A trunk link is a LAW segment used for VLAN multiplexing between VLAN bridges
(see IEEE Std 802.1V-2001, Virtual Bridged Local Area Networks—Amendment 2:

WO 2004/042984 PCT/US2003/034855
VLAN Classification by Protocol and Port). Every device attached to a trunk link
must be VLAN-aware. This means that they understand VLAN rnembership and
VLAN frame formats. All frames, including end station frames, on a trunk link are
VLAN-tagged, meaning that they carry a non-null VID. There can be no VLAN-
5 unaware end stations on a trunk link.
The trunk link 16 in Figure 1 is a multiplexed LAN segment shared by two bridges
12, 14. in general, many VLAN-aware bridges may be attached to a trunk link.
10 The access links 11 are LAN segments that do not multiplex VLANs. Instead, each
access Jink carries untagged frames of VLAN-tagged frames belonging to a single
VLAN. If frames are tagged then all frames on the segment carry the same V|D and
end stations on the LAN segment must be VLAN aware.
15 Various limitations are encountered with the current state of VLAN art. One problem
is that of cryptographic separation of VLANs over trunk finks. The Introduction of a
schema to solve such probiem Use If raises the issue of efficient frame transfer
between encrypted and unencrypted LAN segments which represent a stngle VLAN,
20 SUMMARY Of THE INVENTION
The invention comprises Tnree extensions of Ihe IEEE 8D2.1Q VLAN bridge model
(see IEEE Sto 802.1Q-1998, IEEE Standards for Local and Metropolitan Area
Networks; Virtual Bridged Local Area Networks) . The first extension is the
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Cryptographic separation of VLANs over trunk links, A new LAN segment typer
referred to herein as the encapsulated segment type, is introduced. Air frames on
such a segment ars encapsulated according lo an encryption and authentication-
code scheme. The second extension is the division of a trunk port into inbound and
5 outbound tranks ports. Thethird extension is a protocol, referred to herein as the
Transfer Point Protocol (TPP), that automatically infers for each outbound trunk port
in a bridged VLAN, a set of LAN segment types for the port that minimizes the
number of transfers between encapsulated and unencapsulated segments required
to transport a frame in the bridge VLAN,
10
BRIEF DESCRlPTION OF THE DRAWINGS
Figure 1 is a block schematic diagram showing a port-basert VLAN;
15
Figure 2 is a block schematic diagram showing a bridged cryptographta VLAN
according to the invention;
Figure 3 is a flow diagram showing construction of a forwarding set according to the
invention;
20 Figure 4 is a block schematic diagram showing a bridged cryptographic VLAN wrth
two wireless trunk links according to the invention;
Figure 5 is a block schemattc diagram showing a symmetric labeling of outbound
ports in a bridged cryptographic VLAN according to the invention;
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Figure 6 is a block schematic diagram showing an asymmetric labeling of outbound
ports in a bridged cryptographic VLAN according to the invention;
Figure 7 is a block schematic diagram showing a purely encapsulated trunk in a
bridged cryptograph VLAN according to the invention;
5 Figure 6 is a flow diagram showing JPP message exchange when Bridge 1 of Figure
7 initiates an announce frame for the VLAN according to the invention;
Figure 9 is a block schematic diagram showing a labeling of the outbound ports
according \o the invention, after swapping Bridges 1 and 2 in Figure 7; and
Figure lo is a biock schematic diagram showing a lebeling of the outbound ports,
10 according to the invention, in a bridged cryptographic VLAN containing a bridge with
three trunk ports.
DETAILED DESCRIPTION OF THE INVENTION
15 LAN segment types
Tnree types of LAN segments represent a VLAN: untagged, tagged, and
encapsulated segments. The IEEE 802 to standard addresses only tagged and
uritaggecf segment types (sea IEEE Std 802.1Q-1998, IEEE Standards for Local and
20 Metropolitan Area Networks: Virtual Bridged Local Area Networks). The standard
specifies bridging semantics only for the transfer of traffic between tagged and
untagged segments representing the same VLAN. The invention provides a
technique that extends the bridging semantics to include transferring traffic between
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an unencapsulated segment (tajgged or untagged ) and an encapsulated segment of
the same VLAN, In general, arty number of LAW segment types can be introduced,
There is one frame type for each type of segment representing a VLAN. There are
5 three kinds of frames tn a bridged, cryptographic VLAMi untamed, VLAN-tagged
also referred to as tagged), and encapsulated. Thefirst two frarne types are those
of the IEEE 802,1Q standard (see IEEE Sid 802,1 Q-1998, IEEE Standards tor Local
and Metropolitan Area Networks; Virtual Bridged Local Area Networks). An
encapsulated frame is cryptographioaily encapsulated. Every eneapsulated frame
10 also has a VLAN teg. The tag, however. is different from the tag used within tagged
frames belonging to the VLAN. Associated with every VLAN are two unique VLAN
tags, ViD-T (used within lagged frames of the VLAN) and VID-E (used within
encapsulated frams of the VLAN).
15 For each VLAN, there is a unique security association comprising a cryptographic
authentication code key for checking the integrity and authenticity of frames that are
tagged as belonging to the VLAN, and a cryptographic key for ensuring the privacy
of all frames belonging to the VLAM,
20 The preferred encapsulation scheme Is an "encrypt-then-MAC" scheme, In this
scheme, the data pay load ot a frame Is encrypted and then a message
authentication code is computed over the restating ciphertexl and the frame's
sequence number- This schema has two major advantages: It facilitates forward
error correction when used with certain block ciphers and modes Of operation and it
25 permits frame authentication without decryption,
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A tagged sel, an untagged set. and an encapsulated set of parts is associated with
each VLAN, The security association for a VLAN may be used to verify the
authenticity and integrity of every trame tagged as belonging to the VLAN, and
5 received at a porr in the VLAN's encapsulated set. The ingress-filtering rule for the
port determines whether verification occurs. The association may also be used to
encapsutete lagged and untged frames belonging to the & VLAN cryptographically
before sending them from a port in the VLAN's encapsulated set,
10 Trunk ports
Every trunk port has an Inbound and an outbound port. A trunk link between two
trunk ports P1 and P2 connects the inbound port of P1 to the outbound port of P2,
and the outbound port of P1 to the inbound port of P2. Therefore 'he sets of LAN
15 segment types to which an inbound port betongs are exactly those of the outbound
port lo which it is connected. So, if is sufficient to assign only outbound parts to sets
ot LAN segment types in order to completely assign alt trunk ports in a bridged VLAN
to sets of LAN segment types
20 The inbound an outbound ports of a trunk pon can belong to different sets of LAN
segment types. For instance, the outbound port of a trunk can belong to a VLAN's
tagged set, antf the inbound port to its encapsulated sei, tn which case, only
encapsulated frames of the VLAN are received on the inbound port, and onty tagged
frames are ever sent from the outbound port,
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Unlike an access port the inbound of outbound port of a trunk port can belong to
both the tagged and encapsulated sets of a VLAN simultaneously.
The division of a trunk port into inbound and outbound ports is absent in the 802- 1Q
5 standard (see IEEE Std 802.1 Q-1993, IEEE Standards for Local and Metropolitan
Area Networks: Virtual Bridged Local Area Networks) where, in effect, the inbound
and outbound ports are the same port. Inbound and outbound frame types are
therefore always the same for a given trunk port in 802.1Q.
10 Figure 2 illustrates a bridged cryptographic VLAN. Ports P1 (20) and P2 (21) are
access ports, one for VLAN A 26. ancf the other for VLAN B 29, VLANs A and B
having access links 30, 31. A trunk link 16 connects the two bridges 12a, 14a via
trunk ports P3 (22) and P4 (23). P3 has inbound port P3, and outbound port P3a P4
has inbound port P4, and outbound port P40 . P4, is connected to P3XXX and P40 is
15 connected to P31. Frames received at P4 arrive on inbound port P41 and those sent
out P4 leave via outbound port P4O. Frames received at P3 arrive on inbound port
P3i arrd those sent out P3 leave via outbound port P3
Ports P5 (24) and P6 (25) are attached to wireless access links 30. In the preferred
20 embodiment, they are actually virtual ports that share a single radio interface (access
point) through which frames are sent and received via RF. VLANs A 28 and B 29
can be represented by different encapsulated segments even though they share the
same RF medium. An end station in VLAN; for exampleT can receive but not
decipher any frame belonging to VLAN 8. Therefore, distinct access links 32, 33 are
25 shown for A and 6 even though their physical separation is only cryptographic.
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Suppose P1 receives only unissued frames, and P2 only tagged frames. Further,
suppose the trunk link carries tagged frames in both directions, and the wireless
access links only encapsulated frames, Then for VLAN A, the untagged set is {Pi},
5 the tagged set Is {P30 P30 P40 P4, } and the encapsulated set is {P5}: and for B the
sets are { } { P2, P30 P3r, P40, P4,}, and { P6 } reapectively.
In the ingress filtering rule at P5 specifies authenticity checking, then a frame
received at P5 is authenticated using the security association for VLAN A. If
10 successful, then the frame is determined to be a member Of the encapsutated
segment for A. Suppose the frame must be forwarded to P4, Then Bridge 2:
decapsulates the frame using the same security association. The bridge forwards
the decapsulated frame to P40 with its tag repraced by A-T, thereby transferring the
frame frorn A's encapsulated segment to its tagged segment. Conversely, frames
15 arriving at P4: and destined tor P5 are encapsulated using the security association
for A. Tag A-T is replaced by A-E, which transfer the frame from As tagged
segment to its encapsulated segment.
There are many variations of the example in Figure 2, For instance, it may be
20 desirable to protect traffic on VLAN B only. In this case, P5 does not belong to the
encapsulated set for A, Only frames received at P6, i.e. frames tagged with B-E, are
authenticated, and only B-tagged frames received at P4i and destined for P6 are
encapsulated.
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Bridging semantics
Consider a VLAN bridge having multiple ports. Suppose a frame is received at port
P- It is assigned 1o a VLAN In one of several ways. If P is a trunk port, then the
5 franw must carry a VLAN tag of the form VID-T or VlD-E, each of which identities, a
VLAN, namely VID. Otherwiser the frame is diseased. If P is not a trunk port, then
either port or protocol-based VLAN classification can be used to assign the frame to
a VLAN (see IEEE Std 802.1v-2001, Virtual Bridged Local Area
Networks—Amendment 2: VLAN Classification by Protocol and Port).
10 Ingress filtering
If P is a trunk port and is not in the tagged or encapsulated sets for VID, then the
frame is discarded. The ingress-filter rule for a port may specify authentication and
integrity checking for certain VLANS. If P is a port whose ingress filter rule requires
15 authentication and integrity checking for the VLAN VlD, then the frame received at P
must have a VLAN tag VID-E. Otherwise, the frame is discarded. In 1he preferred
emboiment, an authentication code is computed over the received frame's
ciphertext and sequence number using the security association for VID. If it does not
match, the received authentication code In the frame, then the frarm Is discarded.
20 otherwise, tha frame is judged to belong to the encapsulated segment for VlD.
If P is not in the tagged set for VlD, but it is attached to a VLAN-iagged access link,
then the received frame is discarded.
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Forwarding process
The forwarding process begins by corisvutf ing the target port set O. This is the set
of ports to whicn a frame belonging to a particular VLAN rnust be forwarded.
5 Suppose a if farm received al port P belongs to the VLAN SAD. tf the fams must be
flooded then Q contains any ou(bound or access port that is a member of the tagged,
untagged or encapsulated sets for VID. The next step is to shrink Q if. and only if. P
is an inbound port of a trunk that belongs to both the tagged and encapsulated sats
of VID. In this case, every port in the encapsulated set of VID that does not belorig
10 to the tagged set of VID is ramovecf from a if the received frame is a tagged (name,
or every port in ttre tagged or untagged set of VID that does not be!ong to the
encapsulated set of VID is removed from Q if the received frame is encapsulated.
Bacause the inbound port belongs to both sets of LAN segmenrt types fO VlDr the
inbound port must receive a frame of each LAN segment type, and therefore
15 shriking the target port set is justified. The Transfer Point Protocol has the property
that it guarantees shrinking never results in an empty target port set. Shrinking to an
emptytarget set implies the bridge received a fram that it has no reason to receive.
The next step in the forwarding process is to construct a forwarding set for the
20 received frame. This is the set of frames to be forwarded as a result ot receiving the
frame belonging to VID at port P, These are tne frames necessary lo transfer traffic
from one LAN segment of the VLAN to another. Tne table shown in Figure 3 Is used
to construct forwarding sets. The frame received at P belongs to a Kind K of LAN
segment for VID (tagged, untagged, of encapsulated). Likewise, every pont in Q
25 belongs to a kind at LAN sggment, the kind of port set to which it belongs for VID.
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Trunk ports may have two KINDS OF sets: tagged and encapsulated, For every port q
in Q, add a frame to the forwarding set according to rule (K, K) in me table of Figure
3, where K' is a kind of port set to which q belongs for VID.
5 The rules for constructing the forwarding set for a received frame are as follows:
(1) Add received frame to forwording set.
(2) Add VLAN tag VlD-T to received frame. add the result to forwarding set.
10
(3) Received frame is cryptographteally encapsulated using the security
association for VlD resulting frame is VLAN tagged with VID-E and added
to forwording set
15 (4) Remove VID-T fromreceived frame; add urtagged frame to forwording
set
(5) Receded frame's ciphertext is decrypted using the securty association for
VID; resulting frame is untagged and added to forwarding set.
20
(6) Received frame's ciphertext is decrypted using the security association for
VID; resulting frame is tagged wilh VID-T and added to forwarding set.
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WO 2004/042984 PCT/US2003/034855
In the presently preferred embodiment there can be at most three frames in any
forwarding set, corresponding to me three different kinds of LAN segment that can
represent a VLAN. The forwarding process forwards the frames of the forwarding
set as follows
5
• The forwarding process queues for transmission at each port in Q that belongs to
the untagged set for VID, the untagged frame, if any, in the forwarding SET.
• The forwarding process queues for transmission at each port in Q lhaf belongs to
10 the tagged set for VID, the VLAN -tagged frame, if any, in the forwarding set
• The forwarding process queues tor transmission at each port in Q that belongs to
the encapsulated set for VID, the encapsulated frame, if any, in the forwarding
set
15 Frame transfer
Within a bridged, cryptographic VLAN. steps are taken to eliminate redundant
transfers between LAN segments representing the same VLAN. For instance, it is
desirable to avoid transfeming an unencapsulated frame to a VLAN's encapsulated
20 segment more than once in a bridged VLAN because each transfer requires
encryption. Encapsulation should be done once and shared by all egress ports that
belong to the VLAN's encapsulated set across ad bridges. Similarly, it is desirable to
avoid repeated decapsulation across bridges because each calls for decryption
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WO 2004/042984 PCT/US2003/034855
For instance, consider the bridged LAN in Figure 4. Suppose the ports of Bridges 1
(41) and 2 (42) to which the wireless trunk links 43 are attached belong to the
encapsulated set for VLAN & 44. if the trunk link 45 carries only VLAN-tagged
5 frames, then frames belonging to VLAN B that are received at Bridge 1 rnust be
encapsulated at Bridges 1 and 2. However, if the trunk link carries encapsulated
frames then encapsulation need only be done at Bridge 1 and shared with Bridge 2.
There are also situations where ancapsulaiion can be done too early in a bridged
10 LAN, forcing encapsulated frames to be sent over trunk links unnecessarily. There Is
a transfer point for encapsulation and (decapsulation for each VLAN that.minimizes
cryptographic operations. The Transfer Point Protocol (discussed below) infers this
transfer point between segments.
Transfer Point Protocol
15
A minimum spanning tree algorithm can reduce any bridged LAN to a spanning tree
whose nodes are the bridges and whose edges are trunk links. A spanning tree
induces a partial order or bridges. For instance, we can taka as the partial order B1
20 the root of the spanning tree. The set of bridges together with the partial order
defines a complete, partially ordered set. Every nonempty subset of bridges has a
least upper bound.
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WO 2004/042984 PCT/US2003/034855
Consider frames received at the root of the spanning tree. The least upper bound of
all bridges requiring a received frame of a VLAN to belong to one of iha LAN
segments representing the VLAN is the transfer point for converting received frames
to frames for that LAN segment
5
The Transfer Point Protocol (TPP) comprises two link-layer protocols, TPP-T for
adding outbound Trunk ports to thh tagged set of a VLAN, and TPP-E for adding
outbound trunk ports to the encapsulated set of a VLAN. The trunk ports are across
al lbridges that bridge the VLAN- For example, TPP-E determines that the outbound
10 trunk port connecting Bridge 1 to Bridge 2 in Figure 4 must be a member of the
ancapsulated set for VLAN B. That way the wireless trunk port at Bridge 2 can
share encapsulations pefformed by Bridge 1 for its outbound wireless trunk port.
TPP assumes that every access link port has been assigned to the tagged,
15 uataggad, or encapsulated set tor a VLAN prior to execution because it uses this
infortnation to infer the sets to which outboond trunk ports in the bridged VLAN
belong. TPP-E can assign an outbound trunk port to the encapsulated se oi a
VLAN, while TPF'-T can assign the same outbound port to the tagged set of the
VLAM.
20
TPP has two frams types, the announce frame, and the reply frame. Each ct these
frames contains a VLAN ID and a source bridge routing path, where each entry in
the path is a unique pair containing a bridge MAC adress and three bits, one bit for
each LAN segment type, i.e. tagged, untagged, and encapsulated. The tagged bit is
25 high It and only if ihe bridge addressed in the pair has an access port in the tagged
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WO 2004/042981 PCT/US2003/034855
set of the VLAN named in the frame. Tire untagged and encapsulated bits ars set
likewise,
A bridge sends a TPP announce frame, e.g a GARP POU, to a TPP group address,
5 e.g, a GARP application address, through each of its outbound trunk ports for every
VLAN known to it. When a bridge receives an announce frame, it appends to the
right of the path the pair for itself regarding the named VLAN received, and forwards
the frame to each of its enabled, outbound trunk ports except the receiving trunk
port, if it has no other such ports, then il sends the final routing path and received
10 VID in a TPP reply frame to the MAC address thai precedes it jn ihe routing path.
The originating bridge of an announce frame creates a path consisting only of a pair
for itself. When a bridge receives a TPP reply frame on an inbound trunk port, it
forwards the reply frame to the bridge MAC address thai precedes it in the path. If
ihere is none, the frame is discarded.
15 TPP-E
When a bridge receives a TPP reply frame on a trunk port, it adds the trunk's
outbound port to the encapsulated set for the VID in the frame if, and only if, it is
followed by a bridge B in the routing path whose encapsulated bit is high, and either
20 a) the receiving bridge has a tagged or untagged access port for the VID and no
bridge after it in the routing path, up to and including B, has a high tagged or
untagged bit; or
b) the receiving bridge has an encapsulated access port for the VID, or is
preceded by a bridge in the routing path with a high encapsulated bil.
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WO 2004/042984 PCT/US2003/034855
TPP-T
When a bridge receives a TPP reply frame on a trunk port, it adds the trunk's
outbound part lo the togged set tot the VlD in tine frame if, and only if it is fallowed
5 by a bridge B in the routing path whose tagged or urrtagged bit is high, and either
a) the receiving bridge has an encapsulated access port for the VlD and no
bridge after it in the routing path, up to and including B, has a high
encapsulated bit; or
10
b) the receiving bridge has a tagged or untagged access port lor the VlD, or is
preceded by a bridge in the routing path with a high tagged or untagged bit
Example
15
Example 1
Consider bridging a single VLAN- Each access porttherefore is assumed to belong
to this VLAN, Thus, VLAN labeling of ports is omitted in the examples. Instead, the
20 outbound trunk ports are labeled with LAN segment types, i.e. T (tagged), U
(untagged). and E (encapsulated), U an outbound port is labeled with U, for
example, then the port belongs to the untagged set of ihe VLAN,
16

WO 2004/042984 PCT/US2003/034855
initially, every access part, is labeled according to the kindof set to which the port
belongs for the VLAN. Trunk ports are initially unlabeled. jt is the job of TPP ro infer
labels for them. Figure 5 shows a bridging of a VLAN 50 where two bridges 51, 52
are connected by a trunk 53. Each bridge has two access ports. Because each
5 Bridge has both jntagged and encapsulated access ports, TPP infers that both
outbound ports of the trunk belong to the tagged and encapsulated sets of the VLAN.
Each inbound port also belongs to these sets.
10 Each outbound port is a member of the tagged set per rule TPP-T (b). Each bridge
infers this fact when it initiates a TPP announce frame. Therefore, both the
encryption and decryption done by each bridge is shared with the other.
Example 2
15
In Figure 6, Bridge 1 (61) has an untagged access port and Bridge 2 (62) has an
encapsulated access port. Therefore, the outbound port 63 of Bridge 1 is a member
of the encapsulated set per rule TPP-E (a) whereas the outbound port 64 of Bridge 2
is a member of the tagged set per rule TPP-T (a),
20
Example 3
Figure 7 illustrates a purely encapsulated trunk link. All frames over the link are
25 encapsulated, however, no encryption is done at Bridges 2 or 3,
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WO 2004/042984 PCT/US2003/034855
Figure 8 shows the TPP message exchange between Bridges t (71), 2 (72), and 3
(73) when Bridge 1 (71) Of Figure 7 initiates an annouce frame for the VLAN, which
we assume for the example is named "B"
5 Example 4
If Bridges 1 (71) and 2 (72) in figure 7 are interchanged, me result is the bridged
cryptographic VLAN of Figure 9.
10 Example 5
Figure 10 shows a bridge 82 with three trunk ports, each connected to another
bridge 81, 83, 84. The outbound port of the trunk from Bridge 4 (84) belongs to the
tagged and encapsutated sets, whereas the outbound port of Bridge 2 (82) that is
15 connected to the inbound port of Bridge 4 is only a member of the encapsulated set
TPP may run repeatedly to inter changes in transfer points, How frequently it runs
and the number of bridges it affects depends on the displacement of access links,
For example, it an end station is wireless, then movement of the station with respect
20 to the bridged LAN can result in its encapsulated access link being relocated. Unti|
TPP is rerun, there may be redundant transfers for a VLAN.
A bridged VLAN may consist of bridges that do not participate in TPP. !n general,
there may be one or more cryptographic VLAN bridges with trunk ports connected to
25 legacy VLAN bridges. If each such itrunk port is viewed instead as a coflection of
virtual, tagged access ports, one port tor each VLAN tag that can be sent over the
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WO 2004/042984 PCT/US2003/034855
trunk, then TPP can still be run to infer transfer points among participating bridges.
However, there may be redundant transfers across the entire bridged LAN. For
exampler if a nonparticipating core switch were to separate two cryptographic VLAN
bridges, each having an access port in the encapsulated set ot the same VLAN, then
5 traffic between these encapsulated segments would be decrypted upon entry 16 the
core and then re-encrypted after exiting. Observe that no encryption or decryption is
needed if there are no access ports in the core that belong to the tagged or urnagged
sets of the VLAN. In this case, TPP can treat the virtual access port for each VLAN
Tag as an encapsulated access port rather than a tagged access port, Then all traffic
10 between the two encapsulated segments can traverse the core transparently as
encapsulated frames because every encapsulated frame is a VLAN-tagged frame.
Group security
A cryptographic VLAN v is defined by a group of m stations in at has a unique security
15 association The association consisists of the following:
a) an encryption Key Kv1
b) an authentication code key K' v1
c) a distribution key K"V1 and
d) m random values RTL R2.....RXXX
20 The encryption key is a symmetric key used by v-aware bridges and stations of v to
encrypt and decrypt frames belonging to v. All v-aware bridges, and stations of v,
compute and verify authentication codes over encrypted frames of v using K'v
There is one random value for each of the m stations. The /1h station of the group '
knows all m random values except RXXX. The m - 1 random values it knows are
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WO 2004/042984 PCT/US2003/034855
communicated to it by a v-aware bridge. Privacy ot me random values is ensured by
encryption using distribution key K"XXX while their authenticity is ensured by an
authentication code computed over the resulting ciphertext using authentication code
key K'v
5 Joining a cryptographic VLAN
Joining a cryptographic VLAN is done with a two-step protocol:
adding a new Station to tte group, and
enabling all other stations in the group to eliminate the new station later
A user's station joins a cryptographic VLAN v through a mutual authentication
10 protocol executed between the user, via the station, and an authenticates residing on
a v-aWare bridge. If mutuat authentication succeeds, A secure eprremeral channel is
created between the bridge and the new station to transfer Kv K'v and R1. R2
Rm securely trom the bridge to the station. Then the second step of the Join protocol
executes, Otherwise, the protocol terminates immediately. In the second step, the
15 same v-aware bridge chooses a new random value Rm+1 for the new station. and
distributes it to all v-aware bridges, and station comprising v, in a broadcast frame
that is encrypted under K" v and carries an aulhentication code computed over the
ciphertext using K'v The bridge then creates a new distribution key for v and
distributes it to all v-aware bridges and to members of v, including the new station, in
20 a broadcast frame that is encrypted under K v and carries an authentication code
computed over the ciphertext uaing K'v
Although the new station can verify the authenticity of the broadcast containing its
own random value Rm+1 it is unabfe to decrypt it because ft does not hold key K"v
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WO 2004/042984 PCT/US22003/034855
Leaving a cryptographic VLAN
A. subgroup of stations can simultaneously leave a cryptographic VLAN v, perhaps
involuntary. Suppose stations 1....it of a group leave. When this happens, it is
detected by a v-awara bridge which then announces the departure of stations 1,..., k
5 via a single broadcast frame that includes an authentication code computed over the
frama using K'y The broadcast will notify every v-aware bridge and station in the
group that stations 1,,,., k have left. Each such bnd§a and station then attempts to
re key the encryption, authentication code, and distribution keys for vT each as a
fundion of the old key and the random values R,,.,., Rk'. Every v-aware bridge and
10 all remaininig stations in v will share a now eecwity aesoiciation as a result, indudiifiig
K fewer random vslues.
Every v-aware bridge always has the current distribution key for v' unlika a station.
So every such bridge always has the complete set of random values for any
15 subgroup that leaves v, thereby allowing it to always re key the keys for v. The
Situation Is different for stations however Rekeying is a function of the random
values for departing stations, values thai these stations do not have. Therefore, they
are unable to rekey. Furthermore, forward secrecy is guaranteed, A departed
station can never become a rnernber of v again as a result of subsequent rekey ings,
20 This is because rekeyiag is a function of ttis currerrt keys which means. that all Keys
arrived at thereafter will always be a function of a random value unknown to the
station. Only through rejoining vcan the station ever become a member of v again.
Although the invention is described herein with reference to the preferred
25 embodiment, one skilled in the art will readiiy appreciate that other applications may
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WO 2004/042984 PCT/US2003/034855
be substituted for those set forth here in without departing from Ihe split and scope of
the present invention. Accordingly, the invention should only be limited by the
Claims included below.

AMENDED PAGE
REPLACEMENT CLAIMS
5 1, A method for extending VLAM bridging semantics, comprising the steps of:
providing an untagged frame and a tagged Frame in accorttence with tho IEEE
302 1Q VLAN bridge model;
providing a cryptagraphlcally encapsulated frame, wherein every
encapsulated frame has a VLAN tag that is different from a teg used within tagged
10 frames belonging to said VLAN;
providing a. trunk port divided into inbound and! outbound trunk ports;
providing one of said untagged. tagged, and encapsulated frame lype for
each segment representing a bridged, cryptographic VLAN; and
transfenring traffic between an unerrcapsulated segment (tagged or untagged)
15 and an encapsulated segment of a same VLAN.
2. The method of Claim 1, further comprising the step of:
associating with every VLAN two unique VLAN tags, said two unique VLAN
tags comprising VlO-T, which is used within tagged frame of said VLAN, and VID-E.
20 which Is used within encapsulated ffames of said VLAN.
3. The method of Claim 1. wherein for each VLAM, there is a unique security
association comprising a comptographic authentication code key tor checking integrity
and authenticity of frames that are tagged as belonging to sard VLAN, and a
25 cryptographic key for ensuring privacy of all frames belonging to said VLAN.
25

AMENDED PAGE
4, The method of Claim 1, wherein said encapsulated frame is encapsulated in
accordance with an encrypt-then-MAC method, which com prises tho steps of:
encrypting a data paytoad of a frame; and
eorciputinig a message authentication code ovet a resulting dphedett. and said
5 frame's sequence number.
5. The method of Claim 1, wherein a tagged set, an untagged set, and an
encapsulated set of ports ts associated with each VLAN.
10 6, The method of Claim 1, further comprising the step of:
using a security association for a VLAN to verify authenticity aad integrity of
every frame tagged as betonging to said VLAN, and received at a port in said
VLAN's encapsutated set.
15 7. The method of Claim 6, further comprising the step of:
providing an ingress-filtertng rule for said port to determine whether
verification occurs.
8. The method of Claim 6, further comprising the step of,
20 using said association to encapsulate tagged and untagged frames bebng'ing
to paid VLAN cryptographfcally before sending them from a port In said VLAN's
eneapsulated set,
9. An apparatus for sending frames in bridged, crypto graphic VLANs, comprising:
25 at least two bridges
24

AMENDED PAGE
a plurality of trunklinks wherein every trunk link of said trunk links is
associated With the inbound trunk port of one bridge of said at least two bridges and
the outbound trunk port of another bridge of said at feast two bridges;
a plurality of access porte;
5 a plurality of access links wherein every access link of said access links is
associated with one access port of said access ports; and
means for nepreserting said VLANs by different encapsulated segments even
though thay share a same medium, wherein physical separation of said VLANs is
cryptographic
10
10. The apparatus of Claim 9, further comprising:
an ingress-filtering rule associated with alt least one of said access ports for
specifying authenticity checking,, wherein a frame received at said one of sard access
ports is authenticated using a securty association for an associated VLAN;
15 wherein, if authentication successful, then said frame is determined to be a
member of an encapsulated segment for said associated VLAM.
11. The apparatus of Claim 10, wherein said ingress -filterr ule associated with at
least one of said access ports specifies authentication and Integrity checking for
20 certain of said VLANs.
12. The apparatus of Claim 11 r further comprising;
an authentication code that is computed over a received frame's ciphertext
end sequance number using said security association;
25

AMENDED PAGE
wherein, ifsaid authenticate code does not match a received authentication
code in said frame, then said frame is discarded; and
wherein said frame is otherwise determined to belong to an encapsulated
segment for an associated VLAN.
5
13, The apparatus of Claim 9, further comprising:
one or more rules for constructing a target port set for a frame received at an
inbound pert that belongs to the tagged and encapsulated sets off a VLAN;
wherein , every port in the encapsulated set of said VLAN that is not a member
10 of trie tagged set of said VLAN is removed If satd frame is tagged; and
wherein, every port in either the tagged or untaggod sets of said VLAN that is
not a member of the encapsulated set of said VLAN is removed if said frame is
encapsulated.
15 j4.The apparatus of Claim 9, further comprising;
one or more rules for constructing a forwarding set for a received frame, which
rules may comprise any of Ihe following:
add a received frame to said forwarding set;
add a VLAN lag to a received frame; add the resuft to said forwarding set;
20 a received frame is cryptographically encapsulated using a security
association; a resulting frame is VLAN taggedand added to said forwarding set;
remove a VLAN tag from a received frame; add an untagged frame to said
Forwarding set;
a veceived frame's ciphertext is decrypted using 3 security assciation: a
25 resulting frame is untagged and added to said forwarding set; and
26

AMENDED PAGE
a received frame's ciphertext is decrypted using a security association; a
resulting frame is tagged and added to said forwording set.
15, A method for forwarding frames of a forwardlag set that ia defined with respect to
5 the target port set far a received frame of a VLAN, comprising the steps of:
queuing an untagged frame, if any, in said forwarding set. for transmission at
every port in said target set that belongs to the untaggecf set for said VLAN;
queuing an VLAN-tagged frame, if any, in said forwarding set. for transmission at
every port in said target set that belongs to the tagged set for said VLAN; and
10 queuing an encapsulated frams, if any, in said forwarding set. for transmission at
every port in said target set that belongs lo the encapsulated set for sprd VLAN.
16, A method for eliminating redundant transfers between LAN segments in a
bridged, cryptographic VLAN, comprising the STEPS of:
15 avoiding transfer of an unencapsulated frame to a VLAN's encapsulated
segment more than once in a bridged VLAN where each transfer requires
ervcrypton;
perforrnirig encapsufatbn once, said encapsulation being shared by all egress
ports that belong to said VLAN's encapsulated set across all bridges; and
20 avoiding repeated decapsulation across bridges in said bridged VLAN where
each requires decryption.
17 A method for determining optima transfer points between LAN segments
representing a bridged, cryptographic VLAN, comprising the steps of:
27

AMENDED PAGE
reducing any bridged LAN to a spanning tree whose nodes are said bridges
and whose edges are trunk links 10 induce a partial order on sard bridges: wherein a
least bridge is the root of said spanning tree; wherein the set of bridges together with
a partial order define a complete, partsaily ordered set; and wherein every nonempty
5 subset of said bridges has a least upper bound;
wherein said least upper bound of aJI bridges requiring a received frame of a
VLAN to belong to one of said LAN segments representing said VLAN is an optimal
transfer point for converting received frames to frames for that LAN segment; and
deducing automatically, from an assignment of bridge access ports in said
10 bridged VLAN to said LAN segments, the smallest set of LAN segments that must be
associated with a given outbound trunk port in order to bridge said VLAN.
18. An apparatus for implementing a transfer point protocol (TPP) in a bridged,
cryptographic VLANT comprising:
15 at least two brid ges:
a plurality of trunk links wherein every trunk link of said trunk links is
associated with an inbound trunk port of one bridge of said at least two bridges and
an outbound trunk port of-another bridge of said at least two bridges;
a plurality of access ports;
20 a plurality ol accesslinks wherein every access Iink of said access links is
associated with one access port of said access ports: and
means for representing said VLANs by different entapsutated sertjmentes even
though they share a same medium, wbere in physicaf separation of said VLANs is
cryptographic,
28

AMENDED PAGE
two Iink-layef protocols, a first link-layer protocol (TPP-T) for adding outbound
ports to the tagged set of a VLAN. and a second link-layer protocol (TPP-E) for
adding outbound ports to tfte encapsulated set of a VLAN; and
wherein every access port is assigned to a tagged, untagged, or encapsulated
5 set for a VLAM prior to sxecution.
19. The apparatus of Claim 18, said transfer point protocol (TPP) further comprising:
two frames types, one of said frame types comprising an announce frame.
and a second of said frame types comprising a reply frame wherein each of said
10 frames contains a VLAN ID and a source bridge routing palh, where each entry in
said path is a unique pair containig a bridge MAC address and three bits, one bit for
each LAN segment type. wherein said tagged bit is high if andt only if a bridge
addressed in, said pair has an access port in a tagged set of said VLAN named in
said frame, and wherein said untagged and encapsulated bits are set likewise.
15
20. A transfer point protocol (TPP) in a bridged, cryptographic VLAN, comprising the
steps of
a bridge sending a TPP announce frame to a TPP group address through
each of its trunk ports for every VLAN known to it
20 when a bridge receives an announce frame, said bridge appending to
reserved routing path an entry for itself regarding the received VLAN ID. nnd
forwarding said frame to each of its enabled, outbound Irunk ports except the
receiving trunk port: wherein it said bridge has no other such trunk ports, then said
bridge sending a final routing path and said received VLAN ID in a TPP reply frame
25 to the MAC address that precedes said bridge in said routing path:
29

AMENDED PAGE
an originating bridge of an announce frame creating a path consisting only of
an entry for itselt;
when a bridge receives a TPP reply frame, said bridge forwarding said reply
frame to the bridge MAC add ness that precedes said bridge ia said routing path; and
5 if there is none, discarding said frame.
21. The protocol of Claim 20, wherein when a bridge receives a TPP reply frame on
an inbound trunk port, said bridge acids the outbound port corresponding to said
inbound trunk port to line encapsulated set for the VLAN 10 to said frame if, and only
10 if, said bridge is followed by another bridge in said routing path with an encapsulated
access port, and either:
said bridge has a tagged or untagged access port for said VLAN ID and no
bridge after ft in said routing path, up lo an including said other bridge, has a tagged
or untegged access port; or
15 said bridge has an encapsutated access port for said VLAN ID, or said bridge
is preceded by another bridge In said routing path with art encapsulated access port.
22. The protocol of Claim 20, wherein when a bridge receives a TPP reply frame on
an in bound trunK port, said bridge adds the outbound port corresponding to said
23 inbound trunk port to the tagged set for the VLAN ID in said frame if, and only if. said
bridge is followed by another bridge m said routing path with a tagged or untagged
access port, and either,
said bridge has an encapsulated access port for said VLAN ID and no bridge
after it in said routing path, up to an including, said oiher bridge, has an encapsulated
25 access port; or
30

AMENDED PAGE
said bridge has a lagged or untagged access port for said VLAN ID, or said
bridge is preceded by another bridge rn said routing path with a tagged or untagged
access port
5 23. The protocol of Claim 20, wherein the outbound port of a trunk port is treated as:
a set of virtual, tagged access ports with one said tagged access port for each
VLAN supported by said trunk port;
a set of virtual, encapsulated success ports with ane said encapsulated access
port for each VLAN supported by said trunk port; or
10 a set of virtual, encapsulated or virtual, tagged access ports with one said,
ragged or encapsulated access port for each VLAN supported dy said trunk port.
24. A protocol or access link displacement In a bridged, cryptographic VLAN,
comprising bridges that support encapsulated segments, said protocol comprising
15 the steps of:
rccoyriizing an access port of a bridge of said bridged VLAN with which a
displaced access link can be associated, wherein said access port may be, virtual
and created automatically;
automatically assigning said access port In a LAN segment type based an a
30 segment type of said displaced access link; and
executing a transfer port protocol (TPP) for said bridged VLAN with said
access port belonging to said assigned LJ\N segment type,
25. A method for establishing a group security association for a cryptographic VLAN
25 comprising m stations, comprising the steps.of:
31

AMENDED PAGE
providing an encryption key K v, wherein said encryption key is a symmetric
key useti by v-aware bridges and station of v to encrypt and decrypt frames
belonging to v1
providing an authentication code key K¢ v, wherein all unaware bridges, and
5 station of v, compile and verify authemication codes over encrypted frames of v
using K¢ v,
providing a distribution key K¢¢ v; and
providing m random values R1, R2,.... Rm, wherein there is one random
value for each of said fn stations, wherein an ith station of said group knows all m
10 random values except Ri, wherein said m - 1 random vafyea that said ith station
knows are communicated to it by a v-aware bridge;
wherein privacy of said random values is ensured by errayption using said
distribution Key K¢¢ v, while their authenticity is ensured by an authentication code
computed over a resulting clphertext using said authentication code key K¢ v.
15
26. A method for joining an encapsulated segment of a cryptographic VLAN,
compnsing the steps of:
addivig a new statort to a group; and
enabling all other stations in said group to eliminate said new station later
20
27, The method of Claim 26, said step of adding a new station to a group further
comprisingthe step of:
a user' s station joining a cryptographic VLAN v through a mutual
authemication protocol executed between said user, via said user's station, and an
25 authentication residing on a v-aware bridge;
32

AMENDED PAGE
wherein if mutual authentication succeeds, a SECURE ephemeral channel is
created between said v-aware bridge and said new station to transfer an encryption
key K v, an authentication code key K¢ v, and m random values R1, R2, ..., Rm
securely from said v-aware bridge to said new station, in which case sard enabling
5 step executes."'.
otherwise, said protocol terminates immediately.
23. The method of Claim 27, said sfep of enabling all other stations in said group to
elimanate said new station later further comprising the steps of;
10 said v-aware bridge choosing a new random value Rrn+1 for said new station
and distributing said new random value Rm+1 to all v-aware bridges, and stations
comprising v, jn a broadcast frame that is encrypted under a distribution key K¢¢ v
and that carries an airthentication code computed over ciphertext using K¢ v;
said bridge then greatinig a new distribution key for v and ditributing said new
15 distribution key to all v-aware bridges and to members of vr including said new
station, in a broadcast frama that is encrypted under K v and thai carries an
authentication code computed over said crphertext using K¢v.
29, The method of Claim 281 wherein said new station can verify authenticity of a
20 broadcast containing its own random value Rm+1, but is unable to decrypt said
broadcast because it does not hold key K¢¢v.
30. A method for leaving a cryptographic VLAN, comprising the steps of:
detecting with a v-aware bridge a subgroup of stations 1...k simultaneously
25 leaving a cryptographic VLAN v XXX
33

AMENDED PAGE
said bridge v-aware announcing the departure of said stations 1,.,., k via a
single broadcast frame that comprises an authenlication code computed over said
frame using an authentication code key K¢ v, wherein said broadcast notifies every
v-aware bridge and station in group v that stations 1,..,k have left;
5 each such bridge and station then attempting to rakey encryption,
authentication code, and distribution keys for v, each as a function ot an old key and
random values R1...., Rk, and
every v-aware bridge and all remaining stations in group v sharing a new
security association as a result, comprising k fewer random values.
10
31 The method of Claim 30, wherein every v-aware bridge atways has a current
distribution key for v, and
wherein every v-aware bridge always has a complete set cf random values for
any subgroup that leaves group v, thereby allowing it to always rekey the keys for
15 group v.
32. The method of Claim 30,wherein for station rekeying is a function of random
values for departing stations that these stations do not have wherein said stations
are unable to rekey,
20
33. The method of Claim 30, wherein a departed station can never become a
member of group vagain as a rasult of subsequent rekeyings because rekeying is a
function of current keys, and all keys arrived at there after are always a function or a
random value unknown to said departed station.
25
34

AMENDED PAGE
34. The method of Claim 30, wherein a departed station can only become a member
of v again by rejoining v,
5
35

The invention comprises there extention of the XXXX VLAN bridge moded. The first ectention is the cryXXX
graphic separation of VLANs over XXX links. A LAN segment type reffered XXX as an encapXXX LAN segment is introduced. An.
frames or sucha segment are encapsulated according to an encryption and XXX scheme. The second extention is the:
division of a trunk port into inbound and outbound ports. The third extention is a protocol that automatically XXX for each outbound
port in a bridge VLAN. a set of LAN segment types for the port that minimizes the number of transfer between encapsulated and
unencapsulated segments required to transport a frame in the bridge VLAN.

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Patent Number

216839

Indian Patent Application Number

00751/KOLNP/2005

PG Journal Number

12/2008

Publication Date

21-Mar-2008

Grant Date

19-Mar-2008

Date of Filing

28-Apr-2005

Name of Patentee

CRANITE SYSTEMS, INC

Applicant Address

6620 VIA DEL ORO, 2ND FLOOR, SAN JOSE, CA 95119, UNITED STATES OF AMERICA

Inventors:

#	Inventor's Name	Inventor's Address
1	VOLPANO, DENNIS. MICHAEL	22310 DAVENRICH STRFFT, SALINAS, CA 03908 UNITED STATES OI AMERICA.
2	ZHAO, XINHUA. J	787 CORTO STREET, MOUNTAIN VIEW, CA 94043, UNITED STATES OF AMERICA

PCT International Classification Number

H04L

PCT International Application Number

PCT/US2003/034855

PCT International Filing date

2003-10-30

PCT Conventions:

#	PCT Application Number	Date of Convention	Priority Country
1	10/286, 634	2002-11-01	U.S.A.