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Versions: (draft-hao-trill-centralized-replication) 00 01 02 03 04 05 06 07 08

TRILL Working Group                                              W. Hao
INTERNET-DRAFT                                                    Y. Li
Intended Status: Standards Track                    Huawei Technologies
                                                             M. Durrani
                                                            Equinix Inc.
                                                               S. Gupta
                                                            IP Infusion
                                                                  A. Qu
                                                               MediaTec
Expires: June 2017                                    December 30, 2016




           Centralized Replication for Active-Active BUM Traffic
              draft-ietf-trill-centralized-replication-08.txt


Abstract

   In TRILL active-active access, an RPF check failure issue may occur
   when using the pseudo-nickname mechanism specified in RFC 7781. This
   draft describes a solution to resolve this RPF check failure issue
   through centralized replication. All ingress RBridges send BUM
   (Broadcast, Unknown unicast and Mutlicast) traffic to a centralized
   node with unicast TRILL encapsulation. When the centralized node
   receives the BUM traffic, it decapsulates the packets and forwards
   them to their destination RBridges using a distribution tree
   established as per TRILL base protocol RFC 6325. To avoid RPF check
   failure on a RBridge sitting between the ingress RBridge and the
   centralized replication node, some change in the RPF calculation
   algorithm is required. RPF checks on each RBridge should be calculated
   as if the centralized node was the ingress RBridge, instead of being
   calculated using the actual ingress RBridge.

Status of this Memo



   This Internet-Draft is submitted to IETF in full conformance with
   the provisions of BCP 78 and BCP 79.

   Internet-Drafts are working documents of the Internet Engineering
   Task Force (IETF), its areas, and its working groups.  Note that
   other groups may also distribute working documents as Internet-
   Drafts.



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Copyright Notice



   Copyright (c) 2016 IETF Trust and the persons identified as the
   document authors. All rights reserved.

   This document is subject to BCP 78 and the IETF Trust's Legal
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   warranty as described in the Simplified BSD License.



Table of Contents

   1. Introduction ................................................ 3
   2. Conventions used in this document............................ 4
   3. Centralized Replication Solution Overview.................... 4
   4. Frame duplication from remote RBridge........................ 6
   5. Local forwarding behavior on ingress RBridge................. 6
   6. Loop prevention among RBridges in a edge group............... 7
   7. Centralized replication forwarding process................... 8
   8. BUM traffic loadbalancing among multiple centralized nodes...10
   9. Co-existing with the CMT solution........................... 11
   10. Network Upgrade Analysis................................... 12
   11. TRILL protocol extension................................... 12
      11.1. "R" and "C" Flag in the Nickname Flags APPsub-TLV......12


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   12. Security Considerations.................................... 13
   13. IANA Considerations........................................ 13
   14. References ................................................ 14
      14.1. Normative References.................................. 14
      14.2. Informative References................................ 14
   15. Acknowledgments ........................................... 15

1. Introduction

   The IETF TRILL (Transparent Interconnection of Lots of Links)
   [RFC6325] protocol provides loop free and per hop based multipath
   data forwarding with minimum configuration. TRILL uses IS-IS
   [RFC6165] [RFC7176] as its control plane routing protocol and
   defines a TRILL specific header for user data.

   In active-active, Customer Equipment (CE) devices typically are
   multi-homed to edge RBridges which form an edge group. All of the
   uplinks from CE are handled via a Local Active-Active Link Protocol
   (LAALP [RFC7379]) such as Multi-Chassis Link Aggregation (MC-LAG) or
   Distributed Resilient Network Interconnect (DRNI) [802.1AX]. An
   active-active flow-based load sharing mechanism is normally
   implemented to achieve better load balancing and high reliability. A
   CE device can be a layer 3 end system by itself or a bridge switch
   through which layer 3 end systems access to TRILL campus.

   In active-active access, the pseudo-nickname solution in [RFC7781]
   can be used to avoid MAC flip-flop on remote RBridges. The basic
   idea is to use a virtual RBridge RBv with a single pseudo-nickname
   to represent an edge group. Any member RBridge of that edge group
   uses this pseudo-nickname rather than its own nickname as the
   ingress nickname when it injects TRILL data frames to TRILL campus.
   The use of the nickname solves the address flip-flop issue by
   setting the MAC address learnt by a remote RBridge to the pseudo-
   nickname. However, it introduces another issue of incorrect packet
   dropping as follows: When a pseudo-nickname is used by an edge
   RBridge as the ingress nickname to forward BUM (Broadcast, Unknown
   unicast and Mutlicast) traffic, any RBridges (RBn) sitting between
   the ingress RBridge and the distribution tree root will treat the
   traffic as if it was ingressed from the virtual RBridge RBv. If the
   same distribution tree is used by different edge RBridges of the
   same RBv, the traffic may arrive at some RBn from different ports.
   Then the RPF check fails, and the BUM traffic received on unexpected
   ports will be dropped by RBn.

   This document specifies a centralized replication solution for
   broadcast, unknown unicast and multicast (BUM) traffic forwarding to
   resolve the issue of incorrect packet drop caused by RPF check


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   failure in the virtual RBridge case. The basic idea is that all
   ingress RBridges send BUM traffic to a centralized node, which
   SHOULD be a distribution tree root, using unicast TRILL
   encapsulation. When the centralized node receives the packets, it
   decapsulates and forwards them to their destination RBridges using a
   distribution tree established as per the TRILL base protocol.

2. Conventions used in this document

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
   document are to be interpreted as described in RFC-2119 [RFC2119].
   The acronyms and terminology in [RFC6325] are used herein with the
   following additions:

      BUM - Broadcast, Unknown unicast and Multicast

      CE - As in [RFC7783], Customer Equipment device (end station or
   bridge). The device can be either physical or virtual equipment.

      DF - Designated Forwarder [RFC7781]

      FGL - Fine Grained Label [RFC7172].

      LAALP -Local Active-Active Link Protocol [RFC7379].

      MC-LAG - Multi-Chassis Link Aggregation.

      RPF - Reverse Path Forwarding.



3. Centralized Replication Solution Overview

   When an edge RBridge receives BUM traffic from a CE device, it uses
   unicast TRILL encapsulation instead of multicast encapsulation to
   send the packets to a centralized node. The centralized node SHOULD
   be a distribution tree root because such roots are normally chosen
   to be high capacity core RBridges with many high bandwidth
   adjacencies.

   The TRILL header of the unicast TRILL encapsulation contains an
   "ingress RBridge nickname" field and an "egress RBridge nickname"
   field. If the ingress RBridge receives the BUM packet from a port
   that is in an active-active edge group using [RFC7781], it sets the
   ingress RBridge nickname to be the pseudo-nickname rather than its
   own nickname to avoid MAC flip-flop on remote RBridges. The egress


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   RBridge nickname is set to a special nickname of the centralized
   node which is used to differentiate the centralized replication
   purpose unicast TRILL encapsulation from a normal unicast TRILL
   encapsulation. This special nickname is called an R-nickname.

   When the centralized RBridge receives a unicast TRILL encapsulated
   packet with its R-nickname as egress nickname, it decapsulates the
   packet. Then the centralized RBridge replicates and forwards the BUM
   packet to the packet's destination RBridges using one of the
   distribution trees established as per TRILL base protocol. It SHOULD
   use a distribution tree whose tree root is the centralized RBridge
   itself. When the centralized RBridge forwards the BUM traffic, it
   simply sends it on the distribution tree as if it was a locally
   ingressed frame except that the ingress nickname remains the same as
   that in the packet it received to ensure that the MAC address
   learning by all egress RBridges is bound to the pseudo-nickname.

   When the replicated packet is forwarded by each RBridge along the
   distribution tree starting from the centralized node, the RPF check
   is performed as per [RFC6325]. For any RBridge sitting between the
   ingress RBridge and the centralized replication node, the incoming
   port of such BUM packet should be the centralized node facing port
   as the multicast traffic always comes from the centralized node in
   this solution. However the RPF port as the result of distribution
   tree calculation as per [RFC6325] will be the real ingress RBridge
   facing port as it uses virtual RBridge as the ingress RBridge, so
   the RPF check will fail. To solve this problem, some change in the
   RPF calculation algorithm is required. In this case, the RPF
   calculation on each RBridge should use the centralized node as the
   ingress RBridge instead of the real ingress virtual RBridge to
   perform the calculation. As a result, RPF check will accept traffic
   on the centralized node facing port of the RBridge for multi-
   destination traffic. This prevents incorrect frame drops by the RPF
   check.

   To differentiate the centralized replication unicast TRILL
   encapsulation from normal unicast TRILL encapsulation, the R-
   nickname is introduced for centralized replication. When the
   centralized node receives unicast TRILL encapsulation traffic with
   the egress nickname R-nickname, it decapsulates the packet and then
   forwards the packet to the destination RBridges through a
   distribution tree by re-encapsulation as aforementioned. In TRILL,
   RBridges can hold multiple nicknames so the centralized RBridge
   simply obtains another nickname to use as the R-nickname. The
   centralized RBridge or RBridges should announce their R-nickname to
   all TRILL campus through the TRILL LSP extension specified in
   Section 11.


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4. Frame duplication from remote RBridge

   Frame duplication may occur when a remote host sends a multi-
   destination frame to a local CE which has an active-active
   connection to the TRILL campus. To avoid local CE receiving multiple
   copies from a remote RBridge, the designated forwarder (DF)
   mechanism is supported for egress direction multicast traffic.

   The DF election mechanism [RFC7781] allows only one port of one
   RBridge in an active-active group to forward multicast traffic from
   the TRILL campus to the local access side for each VLAN. The basic
   idea of DF is to elect one RBridge per VLAN from an edge group to be
   responsible for egressing the BUM traffic. [RFC7781] describes the
   DF election mechanism among member RBridges involving in an edge
   group.

   If the DF election mechanism is used for frame duplication
   prevention, access ports on an RBridge are categorized as one of
   three types: non-group, group DF port and group non-DF port. The
   last two types can be called group ports. Each of the group ports is
   associated with a pseudo-nickname. If consistent nickname allocation
   to edge group RBridges is used, it is possible that same pseudo-
   nickname is associated with more than one port on a single RBridge.
   A typical scenario is that CE1 is connected to RB1 & RB2 by LAALP1
   while CE2 is connected to RB1 & RB2 by LAALP2. In order to conserve
   the number of pseudo-nicknames used, member ports for both LAALP1
   and LAALP2 on RB1 & RB2 are all associated with the same pseudo-
   nickname.

5. Local forwarding behavior on ingress RBridge

   When an ingress RBridge (RB1) receives BUM traffic from a local
   active-active connected CE (CE1) device, the traffic will be
   injected into the TRILL campus with TRILL encapsulation, and it will
   be replicated and forwarded to all destination RBridges through
   central replication, including the ingress RBridge itself, along a
   TRILL distribution tree. To avoid the traffic looping back to the
   original sender CE, an ingress nickname of the CE group's pseudo-
   nickname is used for traffic filtering.

   However, if there are two CEs, say CE1 and CE2, connecting to the
   ingress RB1 and each associated with the same pseudo-nickname, RB1
   needs to locally replicate and forward to CE2, because another copy
   of the BUM traffic between CE1 and CE2 through TRILL campus will be
   blocked by the traffic filtering.




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   If CE1 and CE2 are not associated with the same pseudo-nickname, the
   copy of the BUM traffic between CE1 and CE2 through TRILL campus
   won't be blocked by the traffic filtering. To avoid duplicated
   traffic on receiver CE, there cannot be local replicated BUM traffic
   between these two CEs on ingress RB1.

   In summary, to ensure correct BUM traffic forwarding behavior for
   each CE, the local replication behavior on the ingress RBridge is as
   follows:

      1. Replicate to the active-active group ports associated with the
   same pseudo-nickname as that associated with the incoming port.

      2. Do not replicate to active-active group ports associated with
   other pseudo-nicknames.

      3. Do not replicate to non-edge-group ports.



   The above local forwarding behavior on the ingress RBridge of RB1
   can be called centralized replication local forwarding behavior A.

   If ingress RBridge RB1 itself is the centralized replication node,
   BUM traffic injected by RB1 into the TRILL campus won't loop back to
   RB1. In this case, the local forwarding behavior is called
   centralized replication local forwarding behavior B. Behavior B on
   RB1 is as follows:

      1. Local replication to the ports associated with the same
   pseudo-nickname as that associated with the incoming port.

      2. Local replication to the group DF port associated with
   different pseudo-nicknames. Do not replicate to group non-DF port
   associated with different pseudo-nicknames.

      3. Local replication to non-edge-group ports.

6. Loop prevention among RBridges in a edge group

   If a CE sends a broadcast, unknown unicast, or multicast (BUM)
   packet through a DF port to an ingress RBridge, that RBridge will
   forward that packet to all or a subset of the other RBridges that
   only have non-DF ports for that active-active group. Because BUM
   traffic forwarding to non-DF ports isn't allowed, in this case the
   frame won't loop back to the CE.



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   If a CE sends a BUM packet through a non-DF port to an ingress
   RBridge, say RB1, then RB1 will forward that packet to other
   RBridges that have a DF port for that active-active group. In this
   case the frame will loop back to the CE and the traffic split-
   horizon filtering mechanism is used to avoid looping back among
   RBridges in the edge group.

   This split-horizon mechanism relies on the ingress nickname field in
   the TRILL header to check if a packet's egress port belongs to a
   same active-active group as the packet's incoming port to the TRILL
   campus.

   When the ingress RBridge receives BUM traffic from an active-active
   connected CE device, the traffic will be sent through the TRILL
   campus with TRILL encapsulation to a centralized RBridge. There it
   will be replicated and forwarded to its destination RBridges, which
   include ingress RBridge itself, through a TRILL distribution tree.
   If the same pseudo-nickname is used for two active-active access CEs
   as ingress nickname, an egress RBridge can use that nickname to
   filter traffic forwarding to all local CEs. In this case, the
   traffic between these two CEs goes through the local RBridge and
   another copy of the traffic from the TRILL campus is filtered. If
   different ingress nicknames are used for two connecting CE devices,
   the access ports connecting to these two CEs should be isolated from
   each other. The BUM traffic between these two CEs should go through
   the TRILL campus, otherwise the destination CE connected to same
   RBridge with the sender CE will receive two copies of the traffic.

7. Centralized replication forwarding process


















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                                 +-----------+
                                 |   (RB5)   |
                                 +-----------+
                                       |
                                 +-----------+
                                 |   (RB4)   |
                                 +-----------+

                                  |     |    |
                          --------      |     --------
                         |              |             |
                       +------+      +------+      +------+
                       |(RB1) |      |(RB2) |      | (RB3)|
                       +------+      +------+      +------+
                         *   |         *  |          * |  ^
                         *   |         *  |          * |   ^
                         *   ----------*-------------*--    ^
                         ***************************** |     ^
                  LAALP1 *                      LAALP2 |      ^
                     +------+                    +------+    +------+
                     |  CE1 |                    | CE2  |    | CE3  |
                     +------+                    +------+    +------+
                 Figure 1  TRILL Active-active access

   Assuming the centralized replication solution is used in the example
   network of above figure 1, RB5 is the distribution tree root and
   centralized replication node, CE1 and CE2 are active-active accessed
   to RB1, RB2, and RB3 through LAALP1 and LAALP2 respectively, CE3 is
   single homed to RB3. The RBridge's own nicknames of RB1 to RB5 are
   nick1 to nick5 respectively. RB1, RB2, and RB3 use the same pseudo-
   nickname for LAALP1 and LAALP2; that pseudo-nickname is P-nick. The
   R-nickname on the centralized replication node of RB5 is S-nick.

   The BUM traffic forwarding process from CE1 to CE2 and CE3 is as
   follows:


       1. CE1 sends BUM traffic to RB3.

       2. RB3 replicates and sends the BUM traffic to CE2 locally. RB2
   also sends the traffic to RB5 using unicast TRILL encapsulation. In
   the TRILL Header, the ingress nickname is set as P-nick and the
   egress nickname is set as S-nick.

      3. RB5 decapsulates the unicast TRILL Data packet. Then it uses a
   distribution tree to forward the packet as a multi-destination TRILL
   Data packet. The egress nickname in the multi-destination TRILL
   Header is the nick5 and the ingress nickname is still P-nick.


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      4. RB4 receives multicast TRILL traffic from RB5. Traffic
   incoming port is the up port facing the distribution tree root,
   RB4's RPF check will be correct based on the changed RPF port
   calculation algorithm in this document. After the RPF check is
   performed, it forwards the traffic to all other egress RBridges (RB1,
   RB2, and RB3).

      5. RB3 receives multicast TRILL traffic from RB4. It decapsulates
   the multi-destination TRILL Data packet. Because the ingress
   nickname of P-nick is equivalent to the nickname of local LAALPs
   connecting to CE1 and CE2, RB3 doesn't forward the traffic to CE1
   and CE2 to avoid duplicated frame. RB3 only forwards the packet to
   CE3.

      6. RB1 and RB2 receive multicast TRILL traffic from RB4. The
   forwarding process is similar to the process on RB3, i.e., because
   the ingress nickname of P-nick is equivalent to the nickname of the
   local LAALPs connecting CE1 and CE2, they also don't forward the
   traffic to local CE1 and CE2.



8. BUM traffic load balancing among multiple centralized nodes

   To support unicast TRILL encapsulation BUM traffic load balancing,
   multiple centralized replication nodes can be deployed and the
   traffic can be spread over these nodes based on VLAN or FGL.
   Furthermore, if it was desirable for a centralized node to be sent
   more of this BUM traffic, it could hold two or more R-nicknames. The
   share of BUM traffic it would receive would be proportional to the
   number of R-nicknames it held.

   Assuming there are k different R-nicknames held by centralized nodes
   in a TRILL campus. The VLAN-based (or FGL-based [RFC7172]) load
   balancing algorithm used by ingress active-active access RBridge is
   as follows:

         1. All R-nicknames are ordered and numbered from 0 to k-1 in
   ascending order treating the nicknames as unsigned 16-bit integers.

         2. For VLAN or FGL ID m, choose the R-nickname whose number
   equals (m mod k) as egress nickname for BUM traffic unicast TRILL
   encapsulation.

   For examples, there are 3 R-Nicknames (RN). The RNs will be ordered
   RN0 to RN2. Assuming there are 5 VLANs from VLAN ID 1 to ID 5



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   spreading among edge RBridges, the traffic in VLAN 1 will go to RN1,
   VLAN 2 will go to RN2, and so on.

   When an ingress RBridge participating in active-active connection
   receives BUM traffic from local CE, the RBridge decides which R-
   nickname to send the traffic to based on the VLAN-based load
   spreading algorithm, thus VLAN/FGL-based load balancing for the BUM
   traffic can be achieved using multiple centralized nodes/ multiple
   R-nicknames.

9. Co-existing with the CMT solution

                    +------+    +------+
                    |(RB6) |    |(RB7) |
                    +------+    +------+
      ------------------|-----------|----------------------
      |            |              |          |            |
   +------+    +------+       +------+    +------+     +------+
   |(RB1) |    |(RB2) |       |(RB3) |    |(RB4) |     |(RB5) |
   +------+    +------+       +------+    +------+     +------+
       |          |               |          |            |
       ------------               -------------------------
             |                               |
         +------+                         +------+
         |  CE1 |                         |  CE2 |
         +------+                         +------+
       Figure 2 CMT and centralized replication co-existing scenario



   Both the centralized replication solution and the CMT [RFC7783]
   solution rely on using pseudo-nicknames to avoid MAC flip-flop on
   remote RBridges. These two solutions can co-exist in a single TRILL
   campus. Each solution can be selected by each active-active edge
   group of RBridges independently.

   As illustrated in Figure 2, RB1 and RB2 use CMT for CE1's active-
   active access, RB3, RB4, and RB5 use the centralized replication for
   CE2's active-active access.

   For the centralized replication solution, edge group RBridges MUST
   announce the local pseudo-nickname using Nickname Flags APPsub-TLV
   with C-flag set. A nickname with the C-flag set is called a "C-
   nickname". A transit RBridge will perform the centralized
   replication specific RPF check algorithm if it receives TRILL Data
   packets with a C-nickname as ingress nickname.



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   In this case, an edge group using CMT [RFC7783] MUST NOT set the C-
   nickname flag on the pseudo-nickname it is using. To avoid confusion,
   a pseudo-nickname MUST NOT be shared between a centralized
   replication edge group and a CMT-based edge group.

10. Network Upgrade Analysis

   Centralized nodes will typically need software and hardware upgrades
   to support centralized replication, which stitches together the TRILL
   unicast traffic decapsulation process and the process of normal
   TRILL multicast traffic forwarding along distribution tree.

   Active-active connection edge RBridges will typically need software
   and hardware upgrade to support unicast TRILL encapsulation for BUM
   traffic; the process is similar to other head-end replication
   processes.

   Transit nodes typically need a software upgrade to support the
   changed RPF port calculation algorithm.

11. TRILL protocol extensions

   Two new flags, "R" and "C", are specified in the Nickname Flags
   APPsub-TLV [RFC7780]. A nickname with the "R" flag set is called an
   R-nickname and a nickname with the the "C" flag set is called a C-
   nickname. The R-nickname is a specialized nickname attached to a
   centralized node to differentiate unicast TRILL encapsulated BUM
   traffic from normal unicast TRILL traffic. The C-nickname flag is
   set on the psudo-nickname for each edge group. A C-nickname is a
   specialized pseudo-nickname for which transit RBridges perform a
   different RPF check algorithm for TRILL data packets with the C-
   nickname in the ingress nickname field.



   When active-active edge RBridges use centralized replication to
   nickname and the C-nickname is used as ingress nickname in the TRILL
   header for the unicast TRILL encapsulation of BUM traffic.

11.1. "R" and "C" Flag in the Nickname Flags APPsub-TLV

   If this APPsub-TLV is being advertised by an RBridge that does not
   have the nickname appearing in the Nickname Flags APPsub-TLV, the R
   and C flag bits in the APPsub-TLV MUST be treated as if they were
   zero.




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              0  1  2  3  4  5  6  7  8  9 10 11 12 13 14 15
             +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
             |   Nickname                                    |
             +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
             |IN|SE|R | C|    RESV                           |
             +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
                             NICKFLAG RECORD

            o R = If R flag is one, it indicates that the advertising
   TRILL switch holding Nickname is a centralized replication node, and
   Nickname is used as egress nickname for edge group RBridges to
   inject BUM traffic into the TRILL campus when the edge group
   RBridges use centralized replication solution for active-active
   access. If flag is zero, that nickname will not be used for that
   purpose.

            o C = If C flag is one, it indicates that the TRILL traffic
   with this nickname as an ingress nickname that requires the special
   RPF check algorithm specified in Section 3. If flag is zero, that
   nickname will not be used for that purpose.

   It is possible, due to errors or due to transient inconsistent LSPs
   when the link state database is converging after a configuration
   change or the like for there to be inconsistent Nickname Flags
   APPsub-TLVs for the same nickname. In this case it is RECOMMENDED
   that the nickname be treated as an R-nickname / C-nickname if any
   Nickname Flags APPsub-TLV for that nickname has the R / C flag set.



12. Security Considerations

   This draft does not introduce any extra security risks. For general
   TRILL Security Considerations, see [RFC6325]. For Security
   Considerations related to pseudo-nickname active-active, see
   [RFC7781].

13. IANA Considerations

   IANA is requested to assign two bits in the Nickname Flags APPsubTLV
   flags for the R and C bits discussed in Section 11.1 [Bits 3 and 4
   suggested] and update the "NickFlags" Bits registry on the TRILL
   Parameters page as follows:


              Bit  Mnemonic   Description           Reference
             ---  --------  --------------------  -----------


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               3    R        Replication Nickname  [This document]
               4    C        Special RFC Check     [This document]

14. References

14.1. Normative References

      [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
   Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/RFC2119, March
   1997, <http://www.rfc-editor.org/info/rfc2119>.

      [RFC6165]  Banerjee, A. and D. Ward, "Extensions to IS-IS for
   Layer-2 Systems", RFC 6165, DOI 10.17487/RFC6165, April 2011,
   <http://www.rfc-editor.org/info/rfc6165>.

      [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, <http://www.rfc-
   editor.org/info/rfc6325>.

      [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,
   <http://www.rfc-editor.org/info/rfc7172>.

      [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,
   <http://www.rfc-editor.org/info/rfc7176>.

      [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, <http://www.rfc-
   editor.org/info/rfc7780>.


14.2. Informative References

      [RFC7781] Zhai, H., Senevirathne, T., Perlman, R., Zhang, M., and
   Y. Li, "Transparent Interconnection of Lots of Links (TRILL):
   Pseudo-Nickname for Active-Active Access", RFC 7781, DOI
   10.17487/RFC7781, February 2016, <http://www.rfc-
   editor.org/info/rfc7781>.

      [RFC7379] Li, Y., Hao, W., Perlman, R., Hudson, J., and H. Zhai,
   "Problem Statement and Goals for Active-Active Connection at the


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   Transparent Interconnection of Lots of Links (TRILL) Edge", RFC 7379,
   DOI 10.17487/RFC7379, October 2014, <http://www.rfc-
   editor.org/info/rfc7379>.

      [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, <http://www.rfc-editor.org/info/rfc7783>.


15. Acknowledgments

   The authors wish to acknowledge the important contributions of
   Donald Eastlake, Hongjun Zhai, Xiaomin Wu, Liang Xia.


































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Authors' Addresses

   Weiguo Hao
   Huawei Technologies
   101 Software Avenue,
   Nanjing 210012
   China
   Email: haoweiguo@huawei.com

   Yizhou Li
   Huawei Technologies
   101 Software Avenue,
   Nanjing 210012
   China
   Email: liyizhou@huawei.com

   Muhammad Durrani
   Equinix Inc.

   Email: mdurrani@equinix.com


   Sujay Gupta
   IP Infusion
   RMZ Centennial
   Mahadevapura Post
   Bangalore - 560048
   India
   Email: sujay.gupta@ipinfusion.com

   Andrew Qu
   MediaTec
   Email: laodulaodu@gmail.com















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