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RFC 7781


Transparent Interconnection of Lots of Links (TRILL): Pseudo-Nickname for Active-Active Access

Part 2 of 2, p. 19 to 35
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6.  TRILL Traffic Processing

   This section provides more details of native frame and TRILL Data
   packet processing as it relates to the RBv's pseudo-nickname.

6.1.  Ingressing Native Frames

   When RB1 receives a unicast native frame from one of its ports that
   has end-station service enabled, it processes the frame as described
   in Section of [RFC6325], with the following exception:

   o  If the port is an RBv port, RB1 uses the RBv's pseudo-nickname
      instead of one of its regular nickname(s) as the ingress nickname
      when doing TRILL encapsulation on the frame.

   When RB1 receives a native multi-destination (broadcast,
   unknown unicast, or multicast) frame from one of its access ports
   (including regular access ports and RBv ports), it processes the
   frame as described in Section of [RFC6325], with the
   following exceptions:

   o  If the incoming port is an RBv port, RB1 uses the RBv's
      pseudo-nickname instead of one of its regular nickname(s) as the
      ingress nickname when doing TRILL encapsulation on the frame.

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   o  For the copies of the frame replicated locally to RBv ports, there
      are two cases, as follows:

      - If the outgoing port(s) is associated with the same
        pseudo-nickname as that of the incoming port but not with the
        same LAALP as the incoming port, the copies are forwarded out of
        that outgoing port(s) after passing the Appointed Forwarder
        check for the frame's VLAN.  That is to say, the copies are
        processed on such port(s), as discussed in Section of

      - Else, the Designated Forwarder (DF) check is also made on the
        outgoing ports for the frame's VLAN after the Appointed
        Forwarder check, and the copies are not output through any ports
        that failed the DF check (i.e., RB1 is not the DF for the
        frame's VLAN on the ports).  Otherwise, the copies are forwarded
        out of the outgoing ports that pass both the Appointed Forwarder
        check and the DF check (see Section 5.2).

   For any such frames received, the MAC address information learned by
   observing it, together with the LAALP ID of the incoming port, SHOULD
   be shared with other member RBridges in the group (see Section 7).

6.2.  Egressing TRILL Data Packets

   This section describes egress processing of the TRILL Data packets
   received on an RBv member RBridge (say RBn).  Section 6.2.1 describes
   the egress processing of unicast TRILL Data packets, and
   Section 6.2.2 specifies the egressing of multi-destination TRILL Data

6.2.1.  Unicast TRILL Data Packets

   When receiving a unicast TRILL Data packet, RBn checks the egress
   nickname in the TRILL Header of the packet.  If the egress nickname
   is one of RBn's regular nicknames, the packet is processed as defined
   in Section of [RFC6325].

   If the egress nickname is the pseudo-nickname of a local RBv, RBn is
   responsible for learning the source MAC address, unless data-plane
   learning has been disabled.  The learned {Inner.MacSA, Data Label,
   ingress nickname} triplet SHOULD be shared within the AAE group as
   described in Section 7.

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   The packet is then decapsulated to its native form.  The Inner.MacDA
   and Data Label are looked up in RBn's local forwarding tables, and
   one of the three following cases will occur.  RBn uses the first case
   that applies and ignores the remaining cases:

   o  If the destination end station identified by the Inner.MacDA and
      Data Label is on a local link, the native frame is sent onto that
      link with the VLAN from the Inner.VLAN or VLAN corresponding to
      the Inner.Label if the packet is FGL.

   o  Else if RBn can reach the destination through another member
      RBridge (say RBk), it tunnels the native frame to RBk by
      re-encapsulating it into a unicast TRILL Data packet and sends it
      to RBk.  RBn uses RBk's regular nickname instead of the
      pseudo-nickname as the egress nickname for the re-encapsulation,
      and the ingress nickname remains unchanged (somewhat similar to
      Section of [RFC7780]).  If the Hop Count value of the
      packet is too small for it to reach RBk safely, RBn SHOULD
      increase that value properly in doing the re-encapsulation.
      (NOTE: When receiving that re-encapsulated TRILL Data packet, as
      the egress nickname of the packet is RBk's regular nickname rather
      than the pseudo-nickname of a local RBv, RBk will process it per
      Section of [RFC6325] and will not re-forward it to another

   o  Else, RBn does not know how to reach the destination; it sends the
      native frame out of all the local ports on which it is Appointed
      Forwarder for the Inner.VLAN (or Appointed Forwarder for the VLAN
      into which the Inner.Label maps on that port for an FGL TRILL Data
      packet [RFC7172]).

6.2.2.  Multi-Destination TRILL Data Packets

   When RB1 receives a multi-destination TRILL Data Packet, it checks
   and processes the packet as described in Section of
   [RFC6325], with the following exception:

   o  On each RBv port where RBn is the Appointed Forwarder for the
      packet's Inner.VLAN (or for the VLAN to which the packet's
      Inner.Label maps on that port if it is an FGL TRILL Data packet),
      the DF check (see Section 5.2) and the ingress nickname filtering
      check (see Section 5.3) are further performed.  For such an RBv
      port, if either the DF check or the filtering check fails, the
      frame MUST NOT be egressed out of that port.  Otherwise, it can be
      egressed out of that port.

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7.  MAC Information Synchronization in Edge Group

   An edge RBridge, say RB1 in LAALP1, may have learned a correspondence
   between a {Data Label and MAC address} and nickname for a remote host
   (say h1) when h1 sends a packet to CE1.  The returning traffic from
   CE1 may go to another member RBridge of LAALP1 (for example, RB2).
   RB2 may not have that correspondence stored.  Therefore, it has to do
   the flooding for unknown unicast.  Such flooding is unnecessary,
   since the returning traffic is almost always expected and RB1 had
   learned the address correspondence.  To avoid the unnecessary
   flooding, RB1 SHOULD share the correspondence with other RBridges of
   LAALP1.  RB1 synchronizes the correspondence by using the
   MAC-Reachability (MAC-RI) sub-TLV [RFC6165] in its ESADI-LSPs

   On the other hand, RB2 has learned the MAC address and Data Label of
   CE1 when CE1 sends a frame to h1 through RB2.  The returning traffic
   from h1 may go to RB1.  RB1 may not have CE1's MAC address and Data
   Label stored even though it is in the same LAALP for CE1 as RB2.
   Therefore, it has to flood the traffic out of all its access ports
   where it is Appointed Forwarder for the VLAN (see Section 6.2.1) or
   the VLAN the FGL maps to on that port if the packet is FGL.  Such
   flooding is unnecessary, since the returning traffic is almost always
   expected and RB2 had learned CE1's MAC and Data Label information.
   To avoid that unnecessary flooding, RB2 SHOULD share the MAC address
   and Data Label with other RBridges of LAALP1.  RB2 synchronizes the
   MAC address and Data Label by enclosing the relative MAC-RI TLV
   within a pair of boundary TRILL APPsub-TLVs for LAALP1 (see
   Section 9.3) in its ESADI-LSP [RFC7357].  After receiving the
   enclosed MAC-RI TLVs, the member RBridges of LAALP1 (i.e., LAALP1
   related RBridges) treat the MAC address and Data Label as if it were
   learned by them locally on their member port of LAALP1; the LAALP1
   unrelated RBridges just ignore LAALP1's boundary APPsub-TLVs and
   treat the MAC address and Data Label as specified in [RFC7357].
   Furthermore, in order to make the LAALP1 unrelated RBridges know that
   the MAC and Data Label are reachable through the RBv that provides
   service to LAALP1, the Topology-ID/Nickname field of the MAC-RI TLV
   SHOULD carry the pseudo-nickname of the RBv, rather than a zero value
   or one of the originating RBridge's (i.e., RB2's) regular nicknames.

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8.  Member Link Failure in an RBv

   As shown in Figure 4, suppose that the link RB1-CE1 fails.  Although
   a new RBv will be formed by RB2 and RB3 to provide active-active
   service for LAALP1 (see Section 5), the unicast traffic to CE1 might
   still be forwarded to RB1 before the remote RBridge learns that CE1
   is attached to the new RBv.  That traffic might be disrupted by the
   link failure.  Section 8.1 discusses failure protection in this

   However, multi-destination TRILL Data packets can reach all member
   RBridges of the new RBv and be egressed to CE1 by either RB2 or RB3
   (i.e., the new DF for the traffic's Inner.VLAN or the VLAN the
   packet's Inner.Label maps to in the new RBv).  Although there might
   be a transient hang time between failure and the establishment of the
   new RBv, special actions to protect against downlink failure for such
   multi-destination packets are not needed.

                        /                    \
                       |     TRILL Campus     |
                        \                    /
                             |     |     |
                         +---+     |     +----+
                         |         |          |
                     +------+     +------+   +------+
                     | RB1  |     | RB2  |   | RB3  |
                     ooooooo|ooooo|oooooo|ooo|ooooo |
                    o+------+ RBv +------+   +-----o+
                      |    |       |  +-|-----+  |
                     \|/+--|-------+  | +------+ |
                    - B |  +----------|------+ | |
                     /|\| +-----------+      | | |
                     (| | |)<--LAALP1       (| | |)<--LAALP2
                    +-------+              +-------+
                    |  CE1  |              |  CE2  |
                    +-------+              +-------+

          B - Failed Link or Link Bundle

               Figure 4: A Multi-Homed CE with a Failed Link

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8.1.  Link Protection for Unicast Frame Egressing

   When the link CE1-RB1 fails, RB1 loses its direct connection to CE1.
   The MAC entry through the failed link to CE1 is removed from RB1's
   local forwarding table immediately.  Another MAC entry learned from
   another member RBridge of LAALP1 (for example, RB2, since it is still
   a member RBridge of LAALP1) is installed into RB1's forwarding table
   (see Section 9.3).  In that new entry, RB2 (identified by one of its
   regular nicknames) is the egress RBridge for CE1's MAC address.
   Then, when a TRILL Data packet to CE1 is delivered to RB1, it can be
   tunneled to RB2 after being re-encapsulated (the ingress nickname
   remains unchanged and the egress nickname is replaced by RB2's
   regular nickname) based on the above installed MAC entry (see
   bullet 2 in Section 6.2.1).  RB2 then receives the frame and egresses
   it to CE1.

   After failure recovery, RB1 learns that it can reach CE1 via link
   CE1-RB1 again by observing CE1's native frames or from the MAC
   information synchronization by member RBridge(s) of LAALP1 as
   described in Section 7.  It then restores the MAC entry to its
   previous one and downloads it to its data-plane "fast path" logic.

9.  TLV Extensions for Edge RBridge Group

   The following subsections specify the APPsub-TLVs needed to support
   pseudo-nickname edge groups.

9.1.  PN-LAALP-Membership APPsub-TLV

   This APPsub-TLV is used by an edge RBridge to announce its associated
   pseudo-nickname LAALP information.  It is defined as a sub-TLV of the
   TRILL GENINFO TLV [RFC7357] and is distributed in E-L1FS FS-LSPs
   [RFC7780].  It has the following format:

         |  Type = PN-LAALP-Membership   |  (2 bytes)
         |  Length                       |  (2 bytes)
         |  LAALP RECORD(1)                          |  (variable)
         .                                           .
         .                                           .
         |  LAALP RECORD(n)                          |  (variable)

          Figure 5: PN-LAALP-Membership Advertisement APPsub-TLV

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   where each LAALP RECORD has the following form:

           0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 ..
         |OE|     RESV    |                  (1 byte)
         |  Size          |                  (1 byte)
         |  Reusing Pseudo-Nickname      |  (2 bytes)
         |  LAALP ID                                  |  (variable)

   o  PN-LAALP-Membership (2 bytes): Defines the type of this
      sub-TLV, 2.

   o  Length (2 bytes): The sum of the lengths of the LAALP RECORDs.

   o  OE (1 bit): A flag indicating whether or not the LAALP wants to
      occupy an RBv by itself; 1 for occupying by itself (or Occupying
      Exclusively (OE)).  By default, it is set to 0 on transmit.  This
      bit is used for edge RBridge group auto-discovery (see
      Section 4.1).  For any one LAALP, the values of this flag might
      conflict in the LSPs advertised by different member RBridges of
      that LAALP.  In that case, the flag for that LAALP is considered
      to be 1.

   o  RESV (7 bits): MUST be transmitted as zero and ignored on receipt.

   o  Size (1 byte): Size of the remaining part of the LAALP RECORD
      (2 plus the length of the LAALP ID).

   o  Reusing Pseudo-Nickname (2 bytes): Suggested pseudo-nickname of
      the AAE group serving the LAALP.  If the LAALP is not served by
      any AAE group, this field MUST be set to zero.  It is used by the
      originating RBridge to help the vDRB to reuse the previous
      pseudo-nickname of an AAE group (see Section 4.2).

   o  LAALP ID (variable): The ID of the LAALP.  See Section 9.4.

   On receipt of such an APPsub-TLV, if RBn is not an LAALP related edge
   RBridge, it ignores the sub-TLV; otherwise, it parses the sub-TLV.
   When new LAALPs are found or old ones are withdrawn compared to its
   old copy, and they are also configured on RBn, RBn performs the
   "Member RBridges Auto-Discovery" procedure described in Section 4.

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9.2.  PN-RBv APPsub-TLV

   The PN-RBv APPsub-TLV is used by a Designated RBridge of a virtual
   RBridge (vDRB) to dictate the pseudo-nickname for the LAALPs served
   by the RBv.  It is defined as a sub-TLV of the TRILL GENINFO TLV
   [RFC7357] and is distributed in E-L1FS FS-LSPs [RFC7780].  It has the
   following format:

          | Type = PN-RBv                 |  (2 bytes)
          | Length                        |  (2 bytes)
          | RBv's Pseudo-Nickname         |  (2 bytes)
          | LAALP ID Size |  (1 byte)
          | LAALP ID (1)                                |  (variable)
          .                                             .
          .                                             .
          | LAALP ID (n)                                |  (variable)

   o  PN-RBv (2 bytes): Defines the type of this sub-TLV, 3.

   o  Length (2 bytes): 3+n*k bytes, where there are n LAALP IDs, each
      of size k bytes.  k is found in the LAALP ID Size field below.  If
      Length is not 3 plus an integer times k, the sub-TLV is corrupt
      and MUST be ignored.

   o  RBv's Pseudo-Nickname (2 bytes): The appointed pseudo-nickname for
      the RBv that serves the LAALPs listed in the following fields.

   o  LAALP ID Size (1 byte): The size of each of the following LAALP
      IDs in this sub-TLV.  8 if the LAALPs listed are MC-LAGs or DRNI
      (Section 6.3.2 of [802.1AX]).  The value in this field is the k
      value that appears in the formula for Length above.

   o  LAALP ID (LAALP ID Size bytes): The ID of the LAALP.  See
      Section 9.4.

   This sub-TLV may occur multiple times with the same RBv
   pseudo-nickname; this means that all of the LAALPs listed are
   identified by that pseudo-nickname.  For example, if there are
   LAALP IDs of different length, then the LAALP IDs of each size would
   have to be listed in a separate sub-TLV.

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   Because a PN-RBv APPsub-TLV is distributed as part of the application
   link state by using the E-L1FS FS-LSP [RFC7780], creation, changes to
   contents, or withdrawal of a PN-RBv APPsub-TLV is accomplished by the
   Designated RBridge updating and flooding an E-L1FS PDU.

   On receipt of such a sub-TLV, if RBn is not an LAALP related edge
   RBridge, it ignores the sub-TLV.  Otherwise, if RBn is also a member
   RBridge of the RBv identified by the list of LAALPs, it associates
   the pseudo-nickname with the ports of these LAALPs and downloads the
   association to data-plane fast path logic.  At the same time, RBn
   claims the RBv's pseudo-nickname across the campus and announces the
   RBv as its child on the corresponding tree or trees using the
   Affinity sub-TLV [RFC7176] [RFC7783].

9.3.  PN-MAC-RI-LAALP Boundary APPsub-TLVs

   In this document, two APPsub-TLVs are used as boundary APPsub-TLVs
   for an edge RBridge to enclose the MAC-RI TLV(s) containing the MAC
   address information learned from the local port of an LAALP when this
   RBridge wants to share the information with other edge RBridges.
   They are defined as TRILL APPsub-TLVs [RFC7357].  The
   PN-MAC-RI-LAALP-INFO-START APPsub-TLV has the following format:

         |Type=PN-MAC-RI-LAALP-INFO-START| (2 bytes)
         | Length                        | (2 bytes)
         | LAALP ID                                 | (variable)

   o  PN-MAC-RI-LAALP-INFO-START (2 bytes): Defines the type of this
      sub-TLV, 4.

   o  Length (2 bytes): The size of the following LAALP ID.  8 if the
      LAALP listed is an MC-LAG or DRNI.

   o  LAALP ID (variable): The ID of the LAALP (see Section 9.4).

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   The PN-MAC-RI-LAALP-INFO-END APPsub-TLV is defined as follows:

         | Type=PN-MAC-RI-LAALP-INFO-END | (2 bytes)
         | Length                        | (2 bytes)

   o  PN-MAC-RI-LAALP-INFO-END (2 bytes): Defines the type of this
      sub-TLV, 5.

   o  Length (2 bytes): 0.

   This pair of APPsub-TLVs can be carried multiple times in an
   ESADI-LSP and in multiple ESADI-LSPs.  When an LAALP related edge
   RBridge (say RBn) wants to share with other edge RBridges the MAC
   addresses learned on its local ports of different LAALPs, it uses one
   or more pairs of such APPsub-TLVs for each such LAALP in its
   ESADI-LSPs.  Each encloses the MAC-RI TLVs containing the MAC
   addresses learned from a specific LAALP.  Furthermore, if the LAALP
   is served by a local RBv, the value of the Topology-ID/Nickname field
   in the relative MAC-RI TLVs SHOULD be the pseudo-nickname of the RBv,
   rather than one of RBn's regular nicknames or a zero value.  Then, on
   receipt of such a MAC-RI TLV, remote RBridges know that the contained
   MAC addresses are reachable through the RBv.

   On receipt of such boundary APPsub-TLVs, when the edge RBridge is not
   an LAALP related one or cannot recognize such sub-TLVs, it ignores
   them and continues to parse the enclosed MAC-RI TLVs per [RFC7357].
   Otherwise, the recipient parses the boundary APPsub-TLVs.  The
   within one TRILL GENINFO TLV.  If an END is encountered without any
   previous START in the ESADI-LSP, the END APPsub-TLV is ignored.
   After encountering a START, if the end of the ESADI-LSP is reached
   without encountering an END, then the end of the ESADI-LSP is treated
   as if it were a PN-MAC-RI-LAALP-INFO-END.  The boundary APPsub-TLVs
   and TLVs between them are handled as follows:

   1) If the edge RBridge is configured with the contained LAALP and the
      LAALP is also enabled locally, it treats all the MAC addresses
      contained in the following MC-RI TLVs enclosed by the
      corresponding pair of boundary APPsub-TLVs as if they were learned
      from its local port of that LAALP;

   2) Else, it ignores these boundary APPsub-TLVs and continues to parse
      the following MAC-RI TLVs per [RFC7357] until another pair of
      boundary APPsub-TLVs is encountered.

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9.4.  LAALP IDs

   The LAALP ID identifies an AAE RBridge group in the TRILL campus and
   thus MUST be unique across the campus.  In all of the APPsub-TLVs
   specified above, the length of the LAALP ID can be determined from a
   size field.  If that length is 8 bytes, the LAALP ID is an MC-LAG or
   DRNI identifier as specified in Section 6.3.2 of [802.1AX].  The
   meaning and structure of LAALP IDs of other lengths are reserved and
   may be specified in future documents.

10.  OAM Packets

   Attention must be paid when generating Operations, Administration,
   and Maintenance (OAM) packets.  To ensure that the response messages
   can return to the originating member RBridge of an RBv, a
   pseudo-nickname cannot be used as the ingress nickname in TRILL OAM
   messages, except in the response to an OAM message that has that
   RBv's pseudo-nickname as the egress nickname.  For example, assume
   that RB1 is a member RBridge of RBvi.  RB1 cannot use RBvi's
   pseudo-nickname as the ingress nickname when originating OAM
   messages; otherwise, the responses to the messages may be delivered
   to another member RBridge of RBvi rather than RB1.  But when RB1
   responds to the OAM message with RBvi's pseudo-nickname as the egress
   nickname, it can use that pseudo-nickname as the ingress nickname in
   the response message.

   Since RBridges cannot use OAM messages for the learning of MAC
   addresses (Section 3.2.1 of [RFC7174]), it will not lead to MAC
   address flip-flopping at a remote RBridge, even though RB1 uses its
   regular nicknames as ingress nicknames in its TRILL OAM messages, and
   at the same time RB1 uses RBvi's pseudo-nickname in its TRILL Data

11.  Configuration Consistency

   The VLAN membership of all the RBridge ports in an LAALP MUST be the
   same.  Any inconsistencies in VLAN membership may result in packet
   loss or non-shortest paths.

   Take Figure 1 as an example.  Suppose that RB1 configures VLAN1 and
   VLAN2 for the CE1-RB1 link, while RB2 only configures VLAN1 for the
   CE1-RB2 link.  Both RB1 and RB2 use the same ingress nickname RBv for
   all frames originating from CE1.  Hence, a remote RBridge (say RBx)
   will learn that CE1's MAC address in VLAN2 is originating from the
   RBv.  As a result, on the return path, RBx may deliver VLAN2 traffic
   to RB2.  However, RB2 does not have VLAN2 configured on the CE1-RB2
   link, and hence the frame may be dropped or has to be redirected to
   RB1 if RB2 knows that RB1 can reach CE1 in VLAN2.

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   How LAALP implementations maintain consistent VLAN configuration on
   the TRILL switch LAALP ports is out of scope for the TRILL protocol.
   However, considering the consequences that might be caused by
   inconsistencies, TRILL switches MUST disable the ports connected to
   an LAALP with an inconsistent VLAN configuration.

   It is important that if any VLAN in an LAALP is being mapped by edge
   RBridges to an FGL [RFC7172] the mapping MUST be the same for all
   edge RBridge ports in the LAALP.  Otherwise, for example, unicast FGL
   TRILL Data packets from remote RBridges may get mapped into different
   VLANs, depending on which edge RBridge receives and egresses them.

   It is important that RBridges in an AAE group not be configured to
   assert the OE-flag if any RBridge in the group does not implement it.
   Since, as stated in [RFC7379], the RBridges in an AAE edge group are
   expected to be from the same vendor, due to the proprietary nature of
   deployed LAALPs, this will normally follow automatically from all of
   the RBridges in an AAE edge group supporting, or not supporting, OE.

12.  Security Considerations

   Authenticity for contents transported in IS-IS PDUs is enforced using
   regular IS-IS security mechanisms [IS-IS] [RFC5310].

   For security considerations pertaining to extensions transported by
   TRILL ESADI, see the Security Considerations section in [RFC7357].

   Since currently deployed LAALPs [RFC7379] are proprietary, security
   over membership in, and internal management of, active-active edge
   groups is proprietary.  If authentication is not used, a rogue
   RBridge that insinuates itself into an active-active edge group can
   disrupt end-station traffic flowing into or out of that group.  For
   example, if there are N RBridges in the group, it could typically
   control 1/Nth of the traffic flowing out of that group and a
   similar amount of unicast traffic flowing into that group.  For
   multi-destination traffic flowing into that group, it could control
   all that was in a VLAN for which it was the DF and can exercise
   substantial control over the DF election by changing its own
   System ID.

   For general TRILL security considerations, see [RFC6325].

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13.  IANA Considerations

   IANA has allocated four code points from the range below 255 for the
   four TRILL APPsub-TLVs specified in Section 9 and added them to the
   "TRILL APPsub-TLV Types under IS-IS TLV 251 Application Identifier 1"
   registry, as follows:

           Type  Name                        Reference
           ----  --------------------------  ---------
             2   PN-LAALP-Membership         RFC 7781
             3   PN-RBv                      RFC 7781
             4   PN-MAC-RI-LAALP-INFO-START  RFC 7781
             5   PN-MAC-RI-LAALP-INFO-END    RFC 7781

14.  References

14.1.  Normative References

   [802.1AX]  IEEE, "IEEE Standard for Local and metropolitan area
              networks - Link Aggregation", IEEE Std 802.1AX-2014,
              DOI 10.1109/IEEESTD.2014.7055197, December 2014.

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119,
              DOI 10.17487/RFC2119, March 1997,

   [RFC5310]  Bhatia, M., Manral, V., Li, T., Atkinson, R., White, R.,
              and M. Fanto, "IS-IS Generic Cryptographic
              Authentication", RFC 5310, DOI 10.17487/RFC5310,
              February 2009, <>.

   [RFC6165]  Banerjee, A. and D. Ward, "Extensions to IS-IS for Layer-2
              Systems", RFC 6165, DOI 10.17487/RFC6165, April 2011,

   [RFC6234]  Eastlake 3rd, D. and T. Hansen, "US Secure Hash Algorithms
              (SHA and SHA-based HMAC and HKDF)", RFC 6234,
              DOI 10.17487/RFC6234, May 2011,

   [RFC6325]  Perlman, R., Eastlake 3rd, D., Dutt, D., Gai, S., and A.
              Ghanwani, "Routing Bridges (RBridges): Base Protocol
              Specification", RFC 6325, DOI 10.17487/RFC6325, July 2011,

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   [RFC6439]  Perlman, R., Eastlake, D., Li, Y., Banerjee, A., and F.
              Hu, "Routing Bridges (RBridges): Appointed Forwarders",
              RFC 6439, DOI 10.17487/RFC6439, November 2011,

   [RFC7172]  Eastlake 3rd, D., Zhang, M., Agarwal, P., Perlman, R., and
              D. Dutt, "Transparent Interconnection of Lots of Links
              (TRILL): Fine-Grained Labeling", RFC 7172,
              DOI 10.17487/RFC7172, May 2014,

   [RFC7176]  Eastlake 3rd, D., Senevirathne, T., Ghanwani, A., Dutt,
              D., and A. Banerjee, "Transparent Interconnection of Lots
              of Links (TRILL) Use of IS-IS", RFC 7176,
              DOI 10.17487/RFC7176, May 2014,

   [RFC7356]  Ginsberg, L., Previdi, S., and Y. Yang, "IS-IS Flooding
              Scope Link State PDUs (LSPs)", RFC 7356,
              DOI 10.17487/RFC7356, September 2014,

   [RFC7357]  Zhai, H., Hu, F., Perlman, R., Eastlake 3rd, D., and O.
              Stokes, "Transparent Interconnection of Lots of Links
              (TRILL): End Station Address Distribution Information
              (ESADI) Protocol", RFC 7357, DOI 10.17487/RFC7357,
              September 2014, <>.

   [RFC7780]  Eastlake 3rd, D., Zhang, M., Perlman, R., Banerjee, A.,
              Ghanwani, A., and S. Gupta, "Transparent Interconnection
              of Lots of Links (TRILL): Clarifications, Corrections, and
              Updates", RFC 7780, DOI 10.17487/RFC7780, February 2016,

   [RFC7783]  Senevirathne, T., Pathangi, J., and J. Hudson,
              "Coordinated Multicast Trees (CMT) for Transparent
              Interconnection of Lots of Links (TRILL)", RFC 7783,
              DOI 10.17487/RFC7783, February 2016,

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14.2.  Informative References

   [IS-IS]    International Organization for Standardization,
              "Information technology -- Telecommunications and
              information exchange between systems -- Intermediate
              System to Intermediate System intra-domain routeing
              information exchange protocol for use in conjunction with
              the protocol for providing the connectionless-mode network
              service (ISO 8473)", ISO/IEC 10589:2002, Second Edition,
              November 2002.

   [RFC7174]  Salam, S., Senevirathne, T., Aldrin, S., and D. Eastlake
              3rd, "Transparent Interconnection of Lots of Links (TRILL)
              Operations, Administration, and Maintenance (OAM)
              Framework", RFC 7174, DOI 10.17487/RFC7174, May 2014,

   [RFC7379]  Li, Y., Hao, W., Perlman, R., Hudson, J., and H. Zhai,
              "Problem Statement and Goals for Active-Active Connection
              at the Transparent Interconnection of Lots of Links
              (TRILL) Edge", RFC 7379, DOI 10.17487/RFC7379,
              October 2014, <>.

   [RFC7782]  Zhang, M., Perlman, R., Zhai, H., Durrani, M., and S.
              Gupta, "Transparent Interconnection of Lots of Links
              (TRILL) Active-Active Edge Using Multiple MAC
              Attachments", RFC 7782, DOI 10.17487/RFC7782,
              February 2016, <>.

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   We would like to thank Mingjiang Chen for his contributions to this
   document.  Additionally, we would like to thank Erik Nordmark, Les
   Ginsberg, Ayan Banerjee, Dinesh Dutt, Anoop Ghanwani, Janardhanan
   Pathangi, Jon Hudson, and Fangwei Hu for their good questions and


   Weiguo Hao
   Huawei Technologies
   101 Software Avenue
   Nanjing  210012

   Phone: +86-25-56623144

   Donald E. Eastlake 3rd
   Huawei Technologies
   155 Beaver Street
   Milford, MA  01757
   United States

   Phone: +1-508-333-2270

Top      Up      ToC       Page 35 
Authors' Addresses

   Hongjun Zhai
   Jinling Institute of Technology
   99 Hongjing Avenue, Jiangning District
   Nanjing, Jiangsu  211169


   Tissa Senevirathne


   Radia Perlman
   2010 256th Avenue NE, #200
   Bellevue, WA  98007
   United States


   Mingui Zhang
   Huawei Technologies
   No. 156 Beiqing Rd., Haidian District
   Beijing  100095


   Yizhou Li
   Huawei Technologies
   101 Software Avenue
   Nanjing  210012

   Phone: +86-25-56625409