TRILL Active-Active Edge Using Multiple MAC Attachments
draft-ietf-trill-aa-multi-attach-00

The information below is for an old version of the document
Document Type Active Internet-Draft (trill WG)
Authors Mingui Zhang  , Radia Perlman  , Hongjun Zhai  , Muhammad Durrani  , Mukhtiar Shaikh , Sujay Gupta 
Last updated 2014-07-22
Replaces draft-zhang-trill-aa-multi-attach
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INTERNET-DRAFT                                              Mingui Zhang
Intended Status: Proposed Standard                                Huawei
Updates: 7176                                              Radia Perlman
                                                                   Intel
                                                            Hongjun Zhai
                                                                     ZTE
                                                        Muhammad Durrani
                                                         Mukhtiar Shaikh
                                                                 Brocade
                                                             Sujay Gupta
                                                             IP Infusion
Expires: January 24, 2015                                  July 23, 2014

        TRILL Active-Active Edge Using Multiple MAC Attachments
                draft-ietf-trill-aa-multi-attach-00.txt

Abstract

   TRILL active-active service provides end stations with flow level
   load balance and resilience against link failures at the edge of
   TRILL campuses.

   This draft specifies a method in which member RBridges in an active-
   active edge RBridge group use their own nicknames as ingress RBridge
   nicknames to encapsulate frames from attached end systems. Thus,
   remote edge RBridges are required to keep multiple locations of one
   MAC address in one Data Label. Design goals of this specification are
   discussed in the document.

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.

   Internet-Drafts are draft documents valid for a maximum of six months
   and may be updated, replaced, or obsoleted by other documents at any
   time.  It is inappropriate to use Internet-Drafts as reference
   material or to cite them other than as "work in progress."

   The list of current Internet-Drafts can be accessed at
   http://www.ietf.org/1id-abstracts.html

   The list of Internet-Draft Shadow Directories can be accessed at
 

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   http://www.ietf.org/shadow.html

Copyright and License Notice

   Copyright (c) 2014 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
   Provisions Relating to IETF Documents
   (http://trustee.ietf.org/license-info) in effect on the date of
   publication of this document. Please review these documents
   carefully, as they describe your rights and restrictions with respect
   to this document. Code Components extracted from this document must
   include Simplified BSD License text as described in Section 4.e of
   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.

Table of Contents

   1. Introduction  . . . . . . . . . . . . . . . . . . . . . . . . .  3
   2. Acronyms and Terminology  . . . . . . . . . . . . . . . . . . .  4
     2.1. Acronyms  . . . . . . . . . . . . . . . . . . . . . . . . .  4
     2.2. Terminology . . . . . . . . . . . . . . . . . . . . . . . .  4
   3. Overview  . . . . . . . . . . . . . . . . . . . . . . . . . . .  4
   4. Incremental Deployable Options  . . . . . . . . . . . . . . . .  5
     4.1. Detail of Option C  . . . . . . . . . . . . . . . . . . . .  6
     4.2. Capability Flags TLV  . . . . . . . . . . . . . . . . . . .  8
   5. Design Goals  . . . . . . . . . . . . . . . . . . . . . . . . .  9
     5.1. No MAC Flip-Floping (Normal Unicast Egress) . . . . . . . .  9
     5.2. Regular Unicast/Multicast Ingress . . . . . . . . . . . . .  9
     5.3. Right Multicast Egress  . . . . . . . . . . . . . . . . . .  9
       5.3.1. No Duplication (Single Exit Point)  . . . . . . . . . .  9
       5.3.2. No Echo (Split Horizon) . . . . . . . . . . . . . . . . 10
     5.4. No Black-hole or Triangular Forwarding  . . . . . . . . . . 11
     5.5. Load Balance Towards the AAE  . . . . . . . . . . . . . . . 11
     5.6. Scalability . . . . . . . . . . . . . . . . . . . . . . . . 11
   6. Security Considerations . . . . . . . . . . . . . . . . . . . . 12
   7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 12
     7.1. TRILL APPsub-TLVs . . . . . . . . . . . . . . . . . . . . . 12
     7.2. Active Active Flags . . . . . . . . . . . . . . . . . . . . 12
   Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . . . 13
   8. References  . . . . . . . . . . . . . . . . . . . . . . . . . . 13
     8.1. Normative References  . . . . . . . . . . . . . . . . . . . 13
     8.2. Informative References  . . . . . . . . . . . . . . . . . . 14
   Appendix A. Scenarios on Split Horizon . . . . . . . . . . . . . . 14
   Author's Addresses . . . . . . . . . . . . . . . . . . . . . . . . 17
 

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1. Introduction

   In the TRILL Active-Active Edge (AAE) topology, a Multi-Chassis Link
   Aggregation Group (MC-LAG) is used to connect multiple RBridges to a
   switch, vSwitch or multi-port end station. An endnode clump is
   attached to this switch or vSwitch. It's required that data traffic
   within a specific VLAN from this endnode clump (including the multi-
   port end station) can be ingressed and egressed by any of these
   RBridges simultaneously. End systems in the clump can spread their
   traffic among these edge RBridges at the flow level. When a link
   fails, end systems keep using the rest of links in the MC-LAG without
   waiting for the convergence of TRILL, which provides resilience to
   link failures.

   Since a packet from each endnode can be ingressed by any RBridge in
   the AAE group, a remote edge RBridge may observe multiple attachment
   points (i.e., egress RBridges) for this endnode identified by its MAC
   address and Data Label (VLAN or Fine Grained Label (FGL)). This issue
   is known as the "MAC flip-flopping". Three potential solutions arise
   to address this issue: 

      1) AAE member RBridges use a pseudonode nickname, instead of their
      own, as the ingress nickname for end systems attached to the MC-
      LAG. [CMT] falls within this category.

      2) AAE member RBridges split work among themselves for which one
      will be responsible for which MAC addresses. A member RBridge will
      encapsulate the packet using its own nickname if it is responsible
      for the source MAC address. Otherwise, if the frame is known
      unicast, it encapsulates the packet using the nickname of the
      responsible RBridge; if the frame is multicast, it needs to
      redirect the packet to its responsible RBridge for encapsulation.

      3) AAE member RBridges keep using their own nicknames. Remote edge
      RBridges are required to keep multiple points of attachment per
      MAC address and Data Label attached to the AAE. 

   The purpose of this document is to develop an approach based on
   solution 3. Although it focuses on exploring solution 3, the major
   design goals discussed here are common for all three AAE solutions.
   Through mirroring the scenarios studied in this draft, other
   potential solutions may benefit as well.

   The main body of the document is organized as follows. Section 2
   lists the acronyms and terminologies. Section 3 gives the overview
   model. Section 4 provides three options for incremental deployment.
   Section 5 describes how this approach meets the design goals. 

 

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2. Acronyms and Terminology

2.1. Acronyms

   AAE: Active-Active Edge

   Data Label: VLAN or FGL

   ESADI: End Station Address Distribution Information [ESADI]

   FGL: Fine Grained Label [RFC7172]

   IS-IS: Intermediate System to Intermediate System [ISIS]

   MC-LAG: Multi-Chassis Link Aggregation Group

   TRILL: TRansparent Interconnection of Lots of Links [RFC6325]

   vSwitch: A virtual switch such as a hypervisor that also simulates a
   bridge.

2.2. Terminology

   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].

   Familiarity with [RFC6325], [RFC6439] and [RFC7177] is assumed in
   this document. 

3. Overview

 

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                               +-----+
                               | RB4 |
                    +----------+-----+----------+
                    |                           |
                    |                           |
                    |       Rest of campus      |
                    |                           |
                    |                           |
                    +-+-----+--+-----+--+-----+-+
                      | RB1 |  | RB2 |  | RB3 |
                      +-----\  +-----+  /-----+
                              \   |   /
                                \ | /
                                 |||MC-LAG1
                                 |||
                                +---+
                                | B |
                                +---+
                             H1 H2 H3 H4: VLAN 10

      Figure 3.1: An example topology for TRILL Active-Active Edge

   Figure 3.1 shows an example network for TRILL Active-Active Edge. In
   this figure, endnodes (H1, H2, H3 and H4) are attached to a bridge
   (B) which communicates with multiple RBridges (RB1, RB2 and RB3) via
   the MC-LAG. Suppose RB4 is a 'remote' RBridge out of the AAE group in
   the TRILL campus. This connection model is also applicable to the
   virtualized environment where the physical bridge can be replaced
   with a vSwitch while those bare metal hosts are replaced with virtual
   machines (VM).  

   For a packet received from their attached endnode clumps, a member
   RBridge of the AAE group always encapsulates it using its own
   nickname as the ingress nickname no matter whether it's unicast or
   multicast.

   The remote RBridge RB4 will see multiple attachments of one MAC from
   each of the end nodes.

4. Incremental Deployable Options

   Three options are listed below to cope with incremental deployment
   scenarios. Among them, Option C can be hardware independent.

   -- Option A

      A new capability announcement would appear in LSPs. "I can cope
      with multiple attachments for an endnode". Only if all edge
 

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      RBridges announce this capability can the AAE group use this
      approach. For those legacy RBridges who are not capable of coping
      with multiple endnode attachments, new type TRILL switches will
      not establish connectivity with them so that they are isolated
      from these new type TRILL switches. Note only edge RBridges (those
      that are Appointed Forwarders [RFC6439]) need to be able to
      support this. It does not affect totally transit RBridges.

   -- Option B

      Each edge RBridge in the AAE group ingress data frames from any
      MC-LAG into a specific TRILL topology [TRILL-MT]. In this way, the
      topology ID is used as the discriminator of different locations of
      a specific MAC address at the remote RBridge. TRILL MAY reserve a
      list of topology IDs to be dedicated to AAE. RBridges that do not
      support this reserved list MUST NOT establish connectivity with
      edge RBridges in the AAE group.

   -- Option C

      As pointed out in Section 4.2.6 of [RFC6325] and Section 5.3 of
      [ESADI], one MAC address may be persistently claimed to be
      attached to multiple RBridges within the same Data Label in the
      TRILL ESADI LSPs. For this option, AAE member RBridges make use of
      TRILL ESADI protocol to distribute multiple attachments of a MAC
      address. Remote RBridges disable the data plane learning for such
      multi-attached MAC addresses.

4.1. Detail of Option C

   An RBridge in an AAE MUST advertise all Data Labels enabled for all
   its attached MC-LAGs. This causes remote RBridges to disable the MAC
   learning via the TRILL Data packet decapsulation within these Data
   Labels for this RBridge. The advertisement of such Data Labels can be
   realized by allocating one reserved flag from the Interested VLANs
   and Spanning Tree Roots Sub-TLV (Section 2.3.6 of [RFC7176]) and one
   reserved flag from the Interested Labels and Spanning Tree Roots Sub-
   TLV (Section 2.3.8 of [RFC7176]). When this flag is set to 1, the
   originating IS is advertising Data Labels for MC-LAGs rather than
   plain LAN links. (See Section 7.2)

   Whenever a MAC from the MC-LAG of this AAE is learned, it needs to be
   advertised via the ESADI protocol. In its TRILL ESADI LSPs, the
   originating IS needs to include the identifier of this AAE. Remote
   RBridges need to know all nicknames of RBridges in this AAE. This is
   achieved by listening to the "MC-LAG Group RBridges" TRILL APPsub-TLV
   defined in Section 5.3.2. MAC Reachability TLVs [RFC6165] are
   composed in a way that each TLV only contains MAC addresses of end
 

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   nodes attached to a single MC-LAG. Each such TLV is enclosed in a
   TRILL APPsub-TLV defined as follows.

      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      | Type = MC-LAG-GROUP-MAC       | (2 bytes)
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |   Length                      | (2 bytes)
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+...+-+-+
      |   MC-LAG System ID              (8 bytes)       | 
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+...+-+-+
      |   MAC-Reachability TLV          (7 + 6*n bytes) |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+...+-+-+

   o  Type: MC-LAG Group MAC (TRILL APPsub-TLV type #TBD) 

   o  Length: The MAC-Reachability TLV [RFC6165] is contained in the
      value field as a sub-TLV. The total number of bytes contained in
      the value field is given by 15+6*n.

   o  MC-LAG System ID: The System ID of the MC-LAG as specified in
      Section 5.3.2 of [802.1AX]. Here, it also serves as the identifier
      of the AAE.

   o  MAC-Reachability sub-TLV: The MC-LAG-GROUP-MAC APPsub-TLV value
      contains the MAC-Reachability TLV as a sub-TLV.

   This MC-LAG-GROUP-MAC APPsub-TLV SHOULD be included in a GENINFO TLV
   [RFC6823] in the ESADI-LSP. There may be more than one occurrence of
   such TRILL APPsub-TLV in one ESADI-LSP fragment.

   For those MAC addresses contained in an MC-LAG-GROUP-MAC APPsub-TLV,
   this document applies. Otherwise, [ESADI] applies. For example, an
   AAE member RBridge continues to enclose MAC addresses learned from
   TRILL Data packet decapsulation in MAC-Reachability TLV as per
   [RFC6165] and advertise them using the ESADI protocol. 

   When the remote RBridge learns MAC addresses contained in the MC-LAG-
   GROUP-MAC APPsub-TLV via the ESADI protocol, it always sends the
   packets destined to these MAC addresses to the closest one (the one
   to which the remote RBridge has the least cost forwarding path) of
   those RBridges in the AAE identified by the MC-LAG System ID in the
   MC-LAG-GROUP-MAC APPsub-TLV. If there are multiple such member
   RBridges, the ingress RBridge is required to select a unique one in a
   pseudo-random way as specified in Section 5.3 of [ESADI].

   When another RBridge in the same AAE group receives an ESADI-LSP with
   the MC-LAG-GROUP-MAC APPsub-TLV, it also learns MAC addresses of
   those end nodes served by the corresponding MC-LAG. These MAC
 

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   addresses SHOULD be learned as if those end nodes are locally
   attached to this RBridge itself.

   An AAE member RBridge MUST use the MC-LAG-GROUP-MAC APPsub-TLV to
   advertise the MAC addresses learned from a plain local link (a non
   MC-LAG link) with Data Labels that happen to be covered by the Data
   Labels of any attached MC-LAG. The reason is that data plane learning
   within these Data Labels at the remote RBridge has been disabled for
   this RBridge.

4.2. Capability Flags TLV

   The following Capability Flags TLV will be included in LSP as a TRILL
   APPsub-TLV of GENINFO-TLV.

      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      | Type = MULTI-MAC-ATTACH-CAP   | (2 bytes)
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |   Length                      | (2 bytes)
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |E|H| Reserved  |                 (1 byte)
      +-+-+-+-+-+-+-+-+

   o  Type: Multi-MAC-Attach Capability (TRILL APPsub-TLV type #TBD) 

   o  Length: Set to 1.

   o  E: When this bit is set, it indicates the originating IS acts as
      specified in Option C.

   o  H: When this bit is set, it indicates that the originating IS
      keeps multiple MAC attachments with fast path hardware at the data
      plane.

   o  Reserved: Reserved flags for future use. These MUST be sent as
      zero and ignored on receipt.

   The Capability Flags TRILL APPsub-TLV is used to notify other
   RBridges whether the originating IS supports the capability indicated
   by the E and H bits. For example, if E bit is set, it indicates the
   originating IS will act as defined in Option C. That is, it will
   disable the data plane MAC learning for AAE RBridges within Data
   Labels advertised by them while waiting for the TRILL ESADI LSPs to
   distribute the {MAC, Nickname, Data Label} association. Meanwhile,
   this RBridge is able to act as an AAE RBridge. It's required to
   advertise MAC addresses learned from MC-LAGs in TRILL ESADI LSPs
   using the MC-LAG-GROUP-MAC APPsub-TLV defined in Section 4.1. AAE
   RBridges supporting Options C won't establish connectivity with
 

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   remote edge RBridges unless this RBridge has advertised this
   Capability Flags TLV with E bit set.

   Capability specification for Option B is out the scope of this
   document. It may be specified in documents for TRILL multi-topology
   [TRILL-MT].

5. Design Goals

   How this specification meets the major design goals of AAE is
   explored in this section. 

5.1. No MAC Flip-Floping (Normal Unicast Egress)

   Since all RBridges talking with the AAE RBridges in the campus are
   able to keep multiple locations for one MAC address, a MAC address
   learned from one AAE member will not be overwritten by the same MAC
   address learned from another AAE member. Although multiple entries
   for this MAC address will be created, the remote RBridge is required
   to adhere to a unique one of the locations (see Section 4.1) for each
   MAC address rather than keep flip-flopping among them.

5.2. Regular Unicast/Multicast Ingress

   MC-LAG guarantees that each frame will be sent upward to the AAE via
   exactly one uplink. RBridges in the AAE can simply follow the process
   per [RFC6325] to ingress the frame. For example, each RBridge uses
   its own nickname as the ingress nickname to encapsulate the packet.
   In such scenario, each RBridge takes for granted that it is the
   Appointed Forwarder for the VLANs enabled on the uplink of the MC-
   LAG.

5.3. Right Multicast Egress

   A fundamental design goal of AAE is that there is no duplication or
   forwarding loop.

5.3.1. No Duplication (Single Exit Point)

   When multi-destination packets for a specific Data Label are received
   from the campus, it's important that exactly one RBridge out of the
   AAE group let through each multicast packet, therefore no duplication
   happens. Since AAE member RBridges support MC-LAG, they are able to
   utilize the hashing function of MC-LAG to determine the single exit
   point. If the output of the hashing function points to the port
   attached to the receiver RBridge itself (i.e., the packet should be
   egressed out of this node), it egresses this packet. Otherwise, the
   packet MUST be dropped.
 

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5.3.2. No Echo (Split Horizon)

   When a multicast frame originated from an MC-LAG is ingressed by an
   RBridge of an AAE group, forwarded across the TRILL network and then
   received by another RBridge in the same AAE group, it is important
   that this RBridge does not egress this frame back to this MC-LAG.
   Otherwise, it will cause a forwarding loop (echo). The well known
   'split horizon' technique can be used to eliminate the echo issue. 

   RBridges in the AAE group need to split horizon based on the ingress
   RBridge nickname plus the VLAN of the TRILL Data packet. They need to
   set up per port filtering lists consists of the tuple of <ingress
   nickname, VLAN>. Packets with information matching with any entry of
   the filtering list MUST NOT be egressed out of that port. The
   information of such filters is obtained by listening to the following
   "MC-LAG Group RBridges" TRILL APPsub-TLV included in the GENINFO TLV
   in LSPs.

      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      | Type = MC-LAG-GROUP-RBRIDGES  | (2 bytes)
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |   Length                      | (2 bytes)
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |   Sender Nickname             | (2 bytes)
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+...+-+-+
      |   MC-LAG System ID              (8 bytes)       | 
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+...+-+-+

   o  Type: MC-LAG Group RBridges (TRILL APPsub-TLV type #TBD)

   o  Length: 10

   o  Sender Nickname: The nickname of the originating IS. 

   o  MC-LAG System ID: The System ID of the MC-LAG as specified in
      Section 5.3.2 of [802.1AX].

   All enabled VLANs MUST be consistent on all ports connected to an MC-
   LAG. So that the enabled VLANs need not to be included in the MC-LAG
   Group RBridges TRILL APPsub-TLV. They can be locally obtained from
   the port attached to that MC-LAG.

   Through parsing an MC-LAG Group RBridges TRILL APPsub-TLV, the
   receiver RBridge discovers all other RBridges connected to the same
   MC-LAG. The Sender Nickname of the originating IS will be added into
   the filtering list of the port attached to the MC-LAG. For example,
   RB3 in Figure 3.1 will set up a filtering list looks like {<RB1,
   VLAN10>, <RB2, VLAN10>} on its port attached to MC-LAG1. According to
 

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   split horizon, TRILL Data packets within VLAN10 ingressed by RB1 or
   RB2 will not be egressed out of this port.

   When there are multiple MC-LAGs connected to the same RBridge, these
   MC-LAGs may have overlap VLANs. Customer may need hosts within these
   overlap VLANs to communicate with each other. In Appendix A, several
   scenarios are given to explain how hosts communicate within the
   overlap VLANs and how split horizon happens.

5.4. No Black-hole or Triangular Forwarding

   If a sub-link of the MC-LAG fails while remote RBridges continue to
   send packets towards the failed port, a black-hole happens. If the
   AAE member RBridge with that failed port starts to redirect the
   packets to other member RBridges for delivery, triangular forwarding
   forms.

   The member RBridge attached to the failed sub-link can make use of
   the ESADI protocol to flush those failure affected MAC addresses as
   defined in Section 5.2 of [ESADI]. After doing that, no packets will
   be sent towards the failed port, hence no black-hole will happen. Nor
   will the member RBridge need to redirect packets to other member
   RBridges, which may otherwise lead to the triangular forwarding.

5.5. Load Balance Towards the AAE

   Since a remote RBridge can record multiple attachments of one MAC
   address, this remote RBridge can choose to spread the traffic towards
   the AAE members. Each of them is able to act as the egress point. By
   doing this, the forwarding paths may be not limited to the least cost
   Equal Cost Multiple Paths from the ingress RBridge to the AAE
   RBridges. The traffic load from the remote RBridge towards the AAE
   RBridges can be balanced based on a pseudo-random selection method
   (see Section 4.1).

   Note that the load balance method adopted at the ingress RBridge is
   not to replace the load balance mechanism of MC-LAG. These two load
   spreading mechanisms should take effect separately.

5.6. Scalability

   With option A, multiple attachments need to be recorded for a MAC
   address learned from AAE RBridges. More entries may be consumed in
   the MAC table. However, MAC addresses attached to an MC-LAG are only
   a small part of all MAC addresses in the whole TRILL campus. As a
   result, the extra space required by the multi-attached MAC addresses
   can be accommodated by RBridges' unused MAC table space. 

 

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   With option C, remote RBridges will keep the multiple attachments of
   a MAC address in the ESADI link state databases. While in the MAC
   table, an RBridge still establishes only one entry for each MAC
   address.

6. Security Considerations

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

   For security considerations pertain to extensions hosted by TRILL
   ESADI, see the Security Considerations section in [ESADI].

   For general TRILL security considerations, see [RFC6325].

7. IANA Considerations

7.1. TRILL APPsub-TLVs

   IANA is requested to allocate three new types under the Generic
   Information TLV (#251) [RFC6823] for the TRILL APPsub-TLVs defined in
   Section 4.1, 4.2 and 5.3.2 of this document. 

   Reference: [ESADI] and [This document]

                  Type     Name                    Reference
               ---------- --------                 -----------
                       0  Reserved            
                       1  ESADI-PARAM              [ESADI]
                   2-254  Unassigned          
                     255  Reserved            
                     256  MC-LAG-GROUP-MAC         This document
                     257  MULTI-MAC-ATTACH-CAP     This document
                     258  MC-LAG-GROUP-RBRIDGES    This document
               260-65534  Unassigned           
                   65535  Reserved          

7.2. Active Active Flags

   IANA is requested to allocate two flag bits, as follows:

   One flag bit appears in the "Interested VLANs and Spanning Tree Roots
   Sub-TLV".

   References: [RFC7176], [ESADI] and [This document]

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

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        0     M4     IPv4 Multicast Router Attached   [RFC7176]
        1     M6     IPv6 Multicast Router Attached   [RFC7176]
        2      -     Unassigned
        3     ES     ESADI Participation              [ESADI]
       4-15    -     (used for a VLAN ID)             [RFC7176]
        16    AA     Enabled VLANs for Active-Active  This document
      17-19    -     Unassigned
      20-31    -     (used for a VLAN ID)             [RFC7176]

   One flag bit appears in the "Interested Labels and Spanning Tree
   Roots Sub-TLV".

   References: [RFC7176], [ESADI] and [This document]

      Bit  Mnemonic  Description                      Reference
      ---  --------  -----------                      ---------
        0     M4     IPv4 Multicast Router Attached   [RFC7176]
        1     M6     IPv6 Multicast Router Attached   [RFC7176]
        2     BM     Bit Map                          [RFC7176]
        3     ES     ESADI Participation              [ESADI]
        4     AA     FGLs for Active-Active           This document
       5-7     -     Unassigned

Acknowledgements

   Authors would like to thank the comments and suggestions from Donald
   Eastlake, Erik Nordmark, Fangwei Hu, Liang Xia and Yizhou Li.

8. References 

8.1. Normative References

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

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

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

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

   [RFC6823] Ginsberg, L., Previdi, S., and M. Shand, "Advertising
 

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             Generic Information in IS-IS", RFC 6823, December 20165

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

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

   [RFC7177] D. Eastlake 3rd and R. Perlman and A. Ghanwani and H. Yang
             and V. Manral, "Transparent Interconnection of Lots of
             Links (TRILL): Adjacency", RFC 7177, May 2014.

   [ESADI]   H. Zhai, F. Hu, et al, "TRILL (Transparent Interconnection
             of Lots of Links): ESADI (End Station Address Distribution
             Information) Protocol", draft-ietf-trill-esadi-07.txt,
             April 2014, Submitted to IESG for Publication.

   [802.1AX] IEEE, "IEEE Standard for Local and metropolitan area
             networks / Link Aggregation", 802.1AX-2008, 1 January 2008.

8.2. Informative References

   [CMT]     T. Senevirathne, J. Pathangi, et al, "Coordinated Multicast
             Trees (CMT)for TRILL", draft-ietf-trill-cmt-03.txt, April
             2014, working in progress.

   [TRILL-MT] D. Eastlake, M. Zhang, A. Banerjee, V. Manral, "TRILL:
             Multi-Topology", draft-eastlake-trill-multi-topology, work
             in progress.

   [ISIS]    ISO, "Intermediate system to Intermediate system routeing
             information exchange protocol for use in conjunction with
             the Protocol for providing the Connectionless-mode Network
             Service (ISO 8473)", ISO/IEC 10589:2002.

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

Appendix A. Scenarios on Split Horizon

 

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    +------------------+   +------------------+   +------------------+
    |        RB1       |   |        RB2       |   |        RB3       |
    +------------------+   +------------------+   +------------------+
    L1       L2       L3   L1       L2       L3   L1       L2       L3
    VL10~20  VL15~25  VL15 VL10~20  VL15~25  VL15 VL10~20  VL15~25  VL15
    MC-LAG1  MC-LAG2  LAN  MC-LAG1  MC-LAG2  LAN  MC-LAG1  MC-LAG2  LAN
    B1       B2       B10  B1       B2       B20  B1       B2       B30

        Figure A.1: An example topology to explain split horizon

   Suppose RB1, RB2 and RB3 are the Active-Active group connecting MC-
   LAG1 and MC-LAG2. MC-LAG1 and MC-LAG2 are connected to B1 and B2 at
   their other ends. Suppose all these RBridges use port L1 to connect
   MC-LAG1 while they use port L2 to connect MC-LAG2. Assume all three
   L1 enable VLAN 10~20 while all three L2 enable VLAN 15~25. So that
   there is an overlap of VLAN 15~20. Customer needs hosts in these
   overlap VLANs to communicate with each other. That is, hosts attached
   to B1 in VLAN 15~20 need to communicate with hosts attached to B2 in
   VLAN 15~20. Assume the remote plain RBridge RB4 also has hosts
   attached in VLAN 15~20 which need to communicate with those hosts in
   these VLANs attached to B1 and B2.

   Two major requirements:

   1. Frames ingressed from RB1-L1-VLAN 15~20 MUST NOT be egressed out
   of ports RB2-L1 and RB3-L1. At the same time,

   2. frames coming from B1-VLAN 15~20 should reach B2-VLAN 15~20.

   RB3 stores the information for split horizon on its ports L1&L2. On
   L1: {<ingress_nickname_RB1, VLAN 10~20>, <ingress_nickname_RB2, VLAN
   10~20>} and on L2: {<ingress_nickname_RB1, VLAN 15~25>,
   <ingress_nickname_RB2, VLAN 15~25>}.

   Five clarification scenarios:

   a. Suppose RB2/RB3 receives a TRILL multicast data packet with VLAN
      15 and ingress nickname RB1. RB3 is the single exit point
      (selected out according to the hashing function of MC-LAG) for
      this packet. On ports L1&L2, RB3 has covered
      <ingress_nickname_RB1, VLAN 15>, so that RB3 will not egress this
      packet out of either L1 or L2. Here, _split horizon_ happens.

      Beforehand, RB1 obtains a native frame on port L1 from B1 in VLAN
      15. RB1 judges it should be forwarded as a multicast frame across
      the TRILL campus. Also, RB1 replicates this frame without TRILL
      encapsulation and sends it out of port L2, so that B2 will get
      this frame.
 

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   b. Suppose RB2/RB3 receives a TRILL multicast data packet with VLAN
      15 and ingress nickname RB4. RB3 is the single exit point. On
      ports L1&L2, since RB3 has not stored any tuple with ingress_
      nickname_RB4, RB3 will decapsulate the packet and egress it out of
      both ports L1 and L2. So both B1 and B2 will receive the frame.

   c. Suppose there is a plain LAN link port L3 on RB1, RB2 and RB3,
      connecting to B10, B20 and B30 respectively. These L3 ports happen
      to be configured with VLAN 15. On port L3, RB1 and RB3 stores no
      information of split horizon for AAE (since this port has not been
      configured to be in any MC-LAG). They will egress the packet
      ingressed out of RB1-L1 in VLAN 15.

   d. If a packet is ingressed from RB1-L1 or RB1-L2 with VLAN 15, port
      RB1-L3 will not egress packets with ingress-nickname-RB1. RB1
      needs to replicate this frame without encapsulation and sends it
      out of port L3.

   e. If a packet is ingressed from RB1-L3, since RB1-L1 and RB1-L2
      cannot egress packets with VLAN 15 and ingress-nickname-RB1, RB1
      needs to replicate this frame without encapsulation and sends it
      out of port L1 and L2.

 

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Author's Addresses

   Mingui Zhang
   Huawei Technologies
   No.156 Beiqing Rd. Haidian District,
   Beijing 100095 P.R. China
        
   EMail: zhangmingui@huawei.com

   Radia Perlman
   Intel Labs
   2200 Mission College Blvd.
   Santa Clara, CA 95054-1549 USA

   Phone: +1-408-765-8080
   EMail: radia@alum.mit.edu

   Hongjun Zhai
   ZTE Corporation
   68 Zijinghua Road
   Nanjing 200012 China

   Phone: +86-25-52877345
   EMail: zhai.hongjun@zte.com.cn

   Muhammad Durrani
   Brocade

   EMail: mdurrani@brocade.com

   Mukhtiar Shaikh
   Brocade

   EMail: mshaikh@brocade.com

   Sujay Gupta
   IP Infusion
   Bangalore, India

   EMail: sujayg@ipinfusion.com

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