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TRILL                                                        Weiguo Hao
                                                              Yizhou Li
                                                               Zhibo Hu
Internet Draft                                                   Huawei
Intended status: Standards Track                      February 14, 2014
Expires: August 2014



         Frame Duplication Avoidance For TRILL Active-Active Access
             draft-hao-trill-dup-avoidance-active-active-01.txt


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Abstract

   The problems in active-active connection to TRILL campus was
   introduced in [TRILL-Active-PS]. Frame duplication was a well
   recognized issue in that scenario. This draft proposes a Designated
   Forwarder (DF) mechanism to solve the issue of frame duplications.
   The basic idea is to elect one RBridge per VLAN from an edge group
   to be responsible for egressing the multicast frames. An edge group
   is a group of edge RBridges that a CE is multi-homed to in active-
   active mode. TRILL protocol extension for DF election is described
   in this draft.





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Table of Contents


   1. Introduction ................................................ 3
   2. Conventions used in this document............................ 5
   3. DF election mechanism overview............................... 5
   4. DF election algorithm per VLAN............................... 6
   5. Link and node failure process................................ 7
   6. TRILL protocol extension..................................... 7
      6.1. The LAGID TLV .......................................... 7
   7. Security Considerations...................................... 8
   8. IANA Considerations ......................................... 8
   9. References .................................................. 8
      9.1. Normative References.................................... 8
      9.2. Informative References.................................. 8
   10. Acknowledgments ............................................ 8

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] [RFC6326bis] as its control plane routing protocol and
   defines a TRILL specific header for user data.

   Customer edge(CE) devices typically are multi-homed to several
   RBridges which form an edge group. All of the uplinks of CE is
   considered as an Multi-Chassis Link Aggregation (MC-LAG) bundle. An
   active-active flow-based load-sharing mechanism is implemented to
   achieve better load balancing and high reliability. A CE device can
   be a layer3 end system by itself or a bridge switch through which
   layer3 end systems are accessed to TRILL campus.

   Draft [TRILL-Active-PS] lists basic problems which any active-active
   solutions should address:













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                                   +------+
                                   | CEx  |
                                   +------+
                                       |
                                    +------+
                                   |(RBx) |
                                   +------+
                                       |
                               -------------------
                              /                    \

                             |                      |
                             |   TRILL Campus       |
                             |                      |
                              \                    /
                               --------------------
                                    |     |    |
                            --------      |     --------
                           |              |             |
                         +------+      +------+      +------+
                         |(RB1) |      |(RB2) |      | (RBk)|
                         +------+      +------+      +------+
                          |              |   |          |
                          |   ___________|   |______    |
                          |   |LAG1          LAG2   |   |
                         +------+                  +------+
                         |  CE1 |                  | CE2  |
                         +------+                  +------+

               Figure 1 TRILL Active-Active Access Scenario

   1. Frame duplications

   2. Loop

   3. Address flip-flop

   4. Unsynchronized information among member RBridges

   This document proposes a Designated Forwarder (DF) mechanism to
   solve the issue of frame duplications. Frame duplication may occur
   when a remote host sends multi-destination frame to a local CE which
   has active-active connection to the TRILL campus. The basic idea of
   DF is to elect one RBridge per VLAN from an edge group to be
   responsible for egressing the multicast traffic. An edge group is
   the group of edge RBridges that a CE is multi-homed to in active-


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   active mode. TRILL protocol extension can be easily extended to
   support DF election mechanism.

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].

   This document uses the same terminology as found in the active-
   active problem statement draft [TRILL-Active-PS].  Some of the terms
   defined in the that document have been repeated in this section for
   the convenience of the reader, along with additional terminology
   that is used by this document.

   CE - customer equipment. Could be a bridge or end station.

   FGL -Fine Grained Label.

   Edge group - a group of edge RBs to which one CE is multiply
   Attached, a edge group corresponds to a MC-LAG. One RB can be in
   more than one edge group.

3. DF election mechanism overview

   Each CE is multi-homed to multiple edge RBs in active-active mode
   through an MC-LAG. These edge RBs form one edge group. An edge group
   corresponds to an MC-LAG. A RB may  join multiple edge groups to
   provide active-active access for multiple CE devices.

   Each MC-LAG should be assigned a globally unique LAGID in network as
   identification. When an edge RB, say RB1, has any downlink port
   running in MC-LAG mode, the following DF election procedures are
   executed.

   1. RB1 acquires the unique LAGID for that MC-LAG through manual or
   automatic provisioning.

   2. RB1 then starts a timer (default value = 10 seconds) to allow the
   reception of LAGID TLV LSP from other RB nodes of same edge group.
   This timer value MUST be same across all RBs of same edge group.

   3. RB1 announces self LAGID in TRILL LSP to TRILL campus before
   local timer expires.




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   4. All RBs that have same LAGID provisioned as in RB1's announcement
   discover each other and form an edge group.

   5. DF election process starts when the timer expires.

   6. Each RB in an edge group elects a DF using same algorithm which
   guarantees the same RB elected as DF per MC-LAG per VLAN. The RB
   that is elected as a DF for a given VLAN will unblocks multi-
   destination traffic in the egress direction towards the CE. All non-
   DF PEs continue to drop multi-destination traffic in the egress
   direction towards the CE.

   All edge RBs, including DF and non-DF, can ingress the traffic to
   TRILL campus as usual. On the other hand, only the elected DF
   RBridge can egress the multi-destination frame from TRILL campus to
   local access network. It ensures no duplicated frame received by
   local CE when a remote RB sends multicast traffic.

4. DF election algorithm per VLAN

   Assuming there are k RBs in an edge group, DF election algorithm per
   VLAN is as follows:

   1. All RBs in an edge group are ordered and numbered from 0 to k-1
   in ascending order according to the 7-octet IS-IS ID.

   2. For VLAN ID m, choose RB whose number equals (m mod k) as DF.

   FGL are primarily intended for >4K tenants use in large Data Centers
   to provide traffic isolation among each tenants. When a CE is multi-
   homed to TRILL campus through FGL in active-active mode, DF election
   should be considered per FGL. If there are some specific multicast
   groups receivers connecting to TRILL campus, DF election should be
   considered per multicast group.

   If VLANs and multicast group addresses are statically configured on
   edge RBridge access port, the operators will  ensure configuration
   consistency  in an edge group. The algorithm always give consistent
   calculation result during DF election.

   If VLANs is dynamically enabled through VLAN registration protocol
   (VRP) (GVRP or MVRP), VLANs enabled for each MC-LAG should be either
   provisioned on all the corresponding ports on RBs of the same edge
   group or synchronized among those RBs. Similarly, the  multicast
   groups dynamically joined through IGMP or MLD protocol by a RBridge
   port should follow the same logic. The detailed synchronization
   mechanism is beyond the scope of this draft.


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   In a steady state, all VLANs and multicast group addresses are
   consistent among all edge RBs in an edge group. Therefore the DF
   election algorithm gives the consistency calculation result for each
   MC-LAG and each VLAN(or FGL/multicast group).

5. Link and node failure process

   When an edge RB, say RB1, has all downlink ports in a particular MC-
   LAG failed, RB1 should announce a new LSP with the remaining alive
   LAGIDs. When other RBs in the same edge group as RB1 receive the LSP,
   these RBs think RB1 has left the edge group and will trigger the DF
   re-election process.

   If RB1 suffers a node failure, after other RBs in the same edge
   group know this information because RB1 becomes unreachable in the
   core IS-IS link state data base (all links to RB1 will appear to be
   down), other RBs will re-run the DF election process.

6. TRILL protocol extension

   The LAGID TLV is introduced to support global LAGID announcement. It
   is carried in an LSP PDU. Edge RBs rely on the LAGID TLV to
   automatically form edge group corresponding to each MC-LAG. DF
   election of the edge group is followed by such auto-discovery.

6.1. The LAGID TLV

   +-+-+-+-+-+-+-+-+
   |Type= LAGID-TLV | (1 byte)
   +-+-+-+-+-+-+-+-+
   | Length | (1 byte)
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |             LAGID             | (10 bytes)
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+


   o Type: TLV Type, TBD.

   o Length: indicates the length of LAGID field, it is a fixed value
   of ten.

   o LAGID: the global LAGID corresponding to a MC-LAG.







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7. Security Considerations

   This draft does not introduce any extra security risks. For general
   TRILL Security Considerations, see [RFC6325].

8. IANA Considerations

   TBD

9. References

9.1. Normative References

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

   [2]     [RFC6325] Perlman, R., et.al. "RBridge: Base Protocol
         Specification", RFC 6325, July 2011.

   [3]     [RFC6326bis] Eastlake, D., Banerjee, A., Dutt, D., Perlman,
         R., and A. Ghanwani, "TRILL Use of IS-IS", draft-eastlake-
         isis-rfc6326bis, work in progress.

9.2. Informative References

   [4]  [TRILL-Active-PS] Li,Y., et.al., "Problems of Active-Active
         connection at the TRILL Edge", draft-yizhou-trill-active-
         active-connection-prob-02, Work in progress, July

         2014.

10. Acknowledgments

   The authors wish to acknowledge the important contributions of
   Donald Eastlake, Junlin Zhang.













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   Authors' Addresses

   Weiguo Hao
   Huawei Technologies
   101 Software Avenue,
   Nanjing 210012
   China

   Phone: +86-25-56623144
   Email: haoweiguo@huawei.com


   Yizhou Li
   Huawei Technologies
   101 Software Avenue,
   Nanjing 210012
   China

   Phone: +86-25-56625375
   Email: liyizhou@huawei.com

   Zhibo Hu
   Huawei Technologies
   156 Beiqing Road,
   Beijing 100095
   China

   Phone: +86-010-60613388
   Email: huzhibo@huawei.com



















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