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Versions: (draft-ietf-l2vpn-spbm-evpn) 00 01 02 RFC 7734

BESS Working Group                            Dave Allan, Jeff Tantsura
Internet Draft                                                 Ericsson
Intended status: Standards Track                              Don Fedyk
Expires: May 2016                                                    HP
                                                            Ali Sajassi
                                                                  Cisco

                                                           October 2015


            Shortest Path Bridging, MAC Mode Support over EVPN
                       draft-ietf-bess-spbm-evpn-02


Abstract


   This document describes how Ethernet Shortest Path Bridging MAC mode
   (802.1aq) can be combined with EVPN to interwork with PBB-PEs as
   described in the PBB-EVPN solution. This is achieved via
   operational isolation of each Ethernet network attached an EVPN core
   while supporting full interworking between the different variations
   of Ethernet networks.

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
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   This Internet-Draft will expire on February 2016.

Copyright and License Notice



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   Copyright (c) 2015 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...................................................2
   1.1. Requirements Language........................................3
   2. Conventions used in this document..............................3
   2.1. Terminology..................................................3
   3. Solution Overview..............................................4
   4. Elements of Procedure..........................................5
   4.1. PE Configuration.............................................5
   4.2. DF Election..................................................6
   4.3. Control plane interworking ISIS-SPB to EVPN..................6
   4.4. Control plane interworking EVPN to ISIS-SPB..................7
   4.5. Data plane Interworking 802.1aq SPBM island or PBB-PE to
   EVPN..............................................................8
   4.6. Data plane Interworking EVPN to 802.1aq SPBM island..........8
   4.7. Data plane interworking EVPN to 802.1ah PBB-PE...............8
   4.8. Multicast Support............................................8
   5. Other Aspects..................................................9
   5.1. Transit......................................................9
   6. Security Considerations........................................9
   7. IANA Considerations...........................................10
   8. Acknowledgments...............................................10
   9. References....................................................10
   9.1. Normative References........................................10
   9.2. Informative References......................................10
   10. Authors' Addresses...........................................11


1. Introduction

   This document describes how Ethernet Shortest Path Bridging MAC mode
   (SPBM) along with Provider Backbone Bridging Provider Edges (PBB-PEs)
   and Provider Backbone Bridged Networks (PBBNs) can be supported by
   Ethernet VPNs (EVPNs) such that each SPBM island is operationally


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   isolated while providing full L2 connectivity between the different
   types of PBBNs where desired. Each SPBM island uses its own control
   plane instance and multi-pathing design, be it multiple equal cost
   tree sets, or multiple spanning trees.

   The intention is to permit past, current and emerging future versions
   of Ethernet to be seamlessly interconnected to permit large scale,
   geographically diverse numbers of Ethernet end systems to be fully
   supported with EVPN as the unifying system.

1.1. Requirements Language

   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 RFC2119 [RFC2119].



2. Conventions used in this document

2.1. Terminology

      BEB: Backbone Edge Bridge
      BGP: Border Gateway Protocol
      B-MAC: Backbone MAC Address
      B-VID: Backbone VLAN ID
      CE: Customer Edge
      DA: Destination Address
      DF: Designated Forwarder
      ESI: Ethernet Segment Identifier
      EVPN: Ethernet VPN
      IB-BEB: A BEB that has both an I-component (customer layer VLAN
      aware bridge) and a B-component (backbone layer VLAN aware
      bridge)
      ISIS-SPB: IS-IS as extended for SPB
      I-SID: I-Component Service ID
      NLRI: Network Layer Reachability Information
      PBB: Provider Backbone Bridging (802.1ah)
      PBBN: Provider Backbone Bridged Network
      PBB-PE: Co located 802.1ah BEB and EVPN PE

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      PE: Provider Edge
      SPB: Shortest Path Bridging
      SPBM: Shortest Path Bridging MAC mode
      SPBM-PE: Co-located 802.1aq SPBM<->EVPN interworking function and
      EVPN PE

3. Solution Overview

   The EVPN solution for 802.1aq SPBM incorporates control plane
   interworking in the PE to map ISIS-SPB [RFC6329] information elements
   into the EVPN Next Layer Reachability Information (NLRI) and vice
   versa. This requires each PE to act both as an EVPN BGP speaker and
   as an ISIS-SPB edge node. Associated with this are procedures for
   configuring the forwarding operations of the PE such that an
   arbitrary number of EVPN attached SPBM islands can be interconnected
   without any topological or multi-pathing dependencies. This model
   also permits PBB-PEs as defined in [PBB-EVPN] to seamlessly
   communicate with the SPBM islands.

                            +--------------+ +----+   +---+
                            |              | |PBB |---|CE2|
                            |              | |PE3 |   +---+
         +-----+     +----+ |              | +----+
         |     |-----|SPBM| |              |
         |SPBM |     |PE1 | |   IP/MPLS    |
   +---+ |NTWK1|     +----+ |   Network    |
   |CE1|-|     |            |              |
   +---+ |     |     +----+ |              |
         |     |-----|SPBM| |              | +----+   +-----+
         +-----+     |PE2 | |              | |SPBM|   |SPBM | +---+
                     +----+ |              | |PE5 |---|NTWK2|-|CE3|
                            +--------------+ +----+   +-----+ +---+
               Figure 1: PBB and SPBM EVPN Network

   Figure 1 illustrates the generalized space addressed by this memo.
   SPBM networks may be multi-homed onto an IP/MPLS network that
   implements EVPN for the purpose of interconnect with other SPBM


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   networks, and/or PBB PEs. The multipathing configuration of each SPBM
   network can be unique as the backbone VLAN ID (B-VID) configuration
   (how multi-pathing is performed in SPBM) is not propagated across the
   IP/MPLS network implementing EVPN. As with PBB networking the B-VID
   is local to the SPBM network so in SPBM a B-MAC associated with B-VID
   is advertised with the supported I-SIDs at the PBB gateway.

   Each EVPN is identified by a route target. I-SID Based Load-balancing
   in [PBB-EVPN] which allows multiple gateways per B-VID (each with
   different I-SIDs) across the EVPN is supported by the interworking
   between PBBNs and SPBM networks.  However SPBM only allows a single
   active designated forwarder per B-VID as described below. The route
   target identifies the set of SPBM islands and PBB-PEs that are
   allowed to communicate. Each SPBM island is administered to have an
   associated Ethernet Segment ID (ESI) extended community associated
   with it.
   BGP acts as a common repository of the I Component Service ID (I-SID)
   attachment points for the set of attached PEs/SPBM islands. This is
   in the form of B-MAC address/I-SID/Tx-Rx-attribute tuples. BGP
   distributes I-SID information into each SPBM island on the basis of
   locally registered interest. If an SPBM island has no backbone edge
   bridges (BEBs) registering interest in a particular I-SID,
   information about that I-SID from other SPBM islands, PBB-PEs or
   PBBNs MUST NOT be leaked into the local ISIS-SPB routing system.
   For each B-VID in an SPBM island, a single SPBM-PE MUST be elected
   the designated forwarder (DF) for the B-VID. An SPBM-PE can be a DF
   for more than one B-VID. This is described further in section 4.2.
   The SPBM-PE originates IS-IS advertisements as if it were an IB-BEB
   that proxies for the other SPBM islands and PBB PEs in the EVPN
   defined by the route target, but the PE typically will not actually
   host any I-components.
   An SPBM-PE that is a DF for a B-VID MUST strip the B-VID tag
   information from frames relayed towards the EVPN. The DF MUST also
   insert the appropriate B-VID tag information into frames relayed
   towards the SPBM island on the basis of the local I-SID/B-VID
   bindings advertised in ISIS-SPB.

4. Elements of Procedure

   A PE MUST implement and perform the following procedures:

4.1. PE Configuration

   At SPBM island commissioning a PE is configured with:

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   1) The route target for the service instance. Where a route target
      is defined as identifying the set of SPBM islands, PBBNs and PBB-
      PEs to be interconnected by the EVPN.

   2) The unique ESI for the SPBM island. Mechanisms for deriving a
      unique ESI for the SPBM island are out of scope.

   The following is configured as part of commissioning an ISIS-SPB
   node:

   1) A Shortest Path Source ID (SPSourceID) used for algorithmic
      construction of multicast addresses. Note this is required for
      SPBM BEB operation independent of the EVPN operation.

   2) The set of B-VIDs used in the SPBM island and multi-pathing
      algorithm IDs to use for each. The set of B-VIDs and multi-
      pathing algorithms used can be different in different domains.
      Therefore the B-VID is local to an SPBM domain and is removed for
      frames carried over the IP/MPLS network.

   A type-1 Route Distinguisher for the node can be auto-derived. The
   actual procedure is out of scope of this document.

4.2. DF Election

   PEs self appoint themselves for the role of DF for a B-VID for a
   given SPBM island. The procedure used is as per section 8.5 of
   [RFC7432] "Designated Forwarder election".
   A PE that assumes the role of DF for a given B-VID is responsible for
   originating specific information into BGP from ISIS-SPB and vice
   versa. A PE that ceases to perform the role of DF for a given B-VID
   is responsible for withdrawing the associated information from BGP
   and ISIS-SPB respectively. The actual information exchanged is
   outlined in the following sections.

4.3. Control plane interworking ISIS-SPB to EVPN

   When a PE receives an SPBM service identifier and unicast address
   sub-TLV as part of an ISIS-SPB MT capability TLV it checks if it is
   the DF for the B-VID in the sub-TLV.

   If it is the DF, and there is new or changed information then a
   MAC/IP advertisement route NLRI is created for each new I-SID in the
   sub-TLV. Changed information that results in modification to existing
   NLRI are processed accordingly.


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   - the Route Distinguisher is set to that of the PE.

   - the ESI is that of the SPBM island.

   - the Ethernet tag ID contains the I-SID (including the Tx/Rx
     attributes). The encoding of I-SID information is as per figure 2.


       0                   1                   2                   3
       0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |T|R| Reserved  |                 I-SID                         |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

         Figure 2: I-SID encoding in the Ethernet tag-ID field

   - the MAC address is copied from the sub-TLV

   - a locally assigned MPLS label

   Similarly in the scenario where a PE became elected DF for a B-VID in
   an operating network, the IS-IS database would be processed in order
   to construct the NLRI information associated with the new role of the
   PE.

   If the BGP database has NLRI information for the I-SID, and this is
   the first instance of registration of interest in the I-SID from the
   SPBM island, the NLRI information with that tag is processed to
   construct an updated set of SPBM service identifier and unicast
   address sub-TLVs to be advertised by the PE.

   The ISIS-SPB information is also used to keep current a local table
   indexed by I-SID to indicate the associated B-VID for processing of
   frames received from EVPN. When an I-SID is associated with more than
   one B-VID, only one entry is allowed in the table. Rules for
   preventing this are out of scope of this memo.

4.4. Control plane interworking EVPN to ISIS-SPB

   When a PE receives a BGP NLRI that has new information, it checks if
   it is the elected DF to communicate this information into ISIS-SPB by
   checking if the I-SID in the Ethernet Tag ID locally maps to the B-
   VID it is an elected DF for. Note that if no BEBs in the SPB island
   have advertised any interest in the I-SID, it will not be associated
   with any B-VID locally, and therefore not of interest. If the I-SID

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   is of local interest to the SPBM island and the PE is the DF for the
   B-VID that the I-SID is locally mapped to, a SPBM service identifier
   and unicast address sub-TLV is constructed/updated for advertisement
   into ISIS-SPB.

   The NLRI information advertised into ISIS-SPB is also used to locally
   populate a forwarding table indexed by B-MAC+I-SID that points to the
   label stack to impose on the SPBM frame. The bottom label in the
   stack being that obtained from the NLRI.

4.5. Data plane Interworking 802.1aq SPBM island or PBB-PE to EVPN

   When an PE receives a frame from the SPBM island in a B-VID for which
   it is a DF, it looks up the B-MAC/I-SID information to determine the
   label stack to be added to the frame for forwarding in the EVPN. The
   PE strips the B-VID information from the frame, adds the label
   information to the frame and forwards the resulting MPLS packet.

4.6. Data plane Interworking EVPN to 802.1aq SPBM island

   When a PE receives a packet from the EVPN it can infer the B-VID to
   overwrite in the SPBM frame from the I-SID or by other means (such as
   via the bottom label in the MPLS stack).

   If the frame has a local multicast destination address (DA), it
   overwrites the SPSourceID in the frame with the local SPSourceID.

4.7. Data plane interworking EVPN to 802.1ah PBB-PE

   A PBB-PE actually has no attached PBBN nor concept of B-VID so no
   frame processing is required.

   A PBB-PE is required to accept SPBM encoded multicast DAs as if they
   were 802.1ah encoded multicast DAs. The only information of interest
   being that it is a multicast frame, and the I-SID encoded in the
   lower 24 bits.

4.8. Multicast Support

   Within a PBBN domain Ethernet Unicast and Multicast end services are
   supported. PBB can tunnel multicast traffic in Unicast PBB frames
   when using head end replication. This is the only form of multicast
   traffic interworking supported by this document. Native PBB multicast
   forwarding over EVPN, PE replication or optimizing PBB multicast
   across the EVPN is not addressed by this memo.




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5. Other Aspects

5.1. Transit

   Any PE that does not need to participate in the tandem calculations
   at the B-MAC layer can use the IS-IS overload bit to exclude SPBM
   tandem paths and behave as pure interworking platform.

6. Security Considerations

   Security issues associated with incorrect interconnect of customer
   LANs cannot be directly addressed by implementations of this
   document, as it requires misconfiguration in the Shortest Path
   Bridging domains. The identifiers so administered have global
   significance to the larger system. They are relayed transparently by
   EVPN and only policed in the SPBM domains. Therefore care is required
   in synchronization of identifiers that need to be common for inter-
   domain operation.

   There are only two identifiers unique to this solution provisioned at
   an SPBM-PE at service turn up; the route target and the ESI. The ESI
   needs to be unique and common to all SPBM-PEs connected to a common
   SPBM network, or PBBN else portions of the overall network will not
   share reachability (EVPN will assume that separate networks are
   interconnected by SPBM). Security issues exist when SPBM domains are
   incorrectly cross connected together via EVPN which will result in
   back-holing or incorrect delivery of data with associated privacy
   issues. This could be achieved by provisioning the incorrect RT value
   at an SPBM-PE or associating the RT with the wrong interface. This
   can be avoided via care in route target provisioning at SPBM-PEs for
   service adds and changes.

   The potentially most destructive behavior of the overall system would
   be frequent changes to the DF elections for a given ESI. This would
   require SPBM-PEs to frequently flap in the form of either the node
   continuously resetting or links flapping in a form that keeps
   severing and re-connecting the SPBM-PE from either the IP/MPLS
   network or the attached SPBM-Network. Either of these scenarios would
   result in significant control plane traffic as DF associated
   information was advertised and withdrawn from both the SPBM and BGP
   control planes. Dual homing of SPBM-PEs on both networks would
   minimize the likelihood of this scenario occurring.

   The issues associated with securing the BGP control plane
   (independent of this particular memo) are reflected in the security
   considerations section of [RFC4761].


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7. IANA Considerations

   No IANA assignments are required by this document.



8. Acknowledgments

   The authors would like to thank Peter Ashwood-Smith, Martin Julien
   and Janos Farkas for their detailed review of this draft.



9. References

9.1. Normative References

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

[RFC4761]  Kompella (ed.), "Virtual Private LAN Service (VPLS) Using
           BGP for Auto-Discovery and Signaling", IETF RFC 4761,
           January 2007

[RFC6329]
                 Fedyk et.al. "IS-IS Extensions Supporting IEEE 802.1aq
           Shortest Path Bridging", IETF RFC 6329, April 2012

[RFC7432]
                 Aggarwal et.al. "BGP MPLS Based Ethernet VPN", IETF RFC
           7432, February 2015

9.2. Informative References

[802.1aq]
                 802.1aq (2012), IEEE Standard for Local and
           Metropolitan Area Networks: Bridges and Virtual Bridged
           Local Area Networks - Amendment 9: Shortest Path
           Bridging

[PBB-EVPN]  Sajassi et.al. "PBB E-VPN", IETF work in progress,
            draft-ietf-l2vpn-pbb-evpn-10, May 2015

[802.1Q]
                 802.1Q (2011), IEEE Standard for Local and metropolitan
           area networks--Media Access Control (MAC) Bridges and
           Virtual Bridged Local Area Networks






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10. Authors' Addresses

   Dave Allan (editor)
   Ericsson
   300 Holger Way
   San Jose, CA  95134
   USA
   Email: david.i.allan@ericsson.com

   Jeff Tantsura
   Ericsson
   300 Holger Way
   San Jose, CA 95134
   USA
   Email: jeff.tantsura@ericsson.com

   Don Fedyk
   Hewlett-Packard
   153 Tayor Street
   Littleton, MA, 01460
   USA
   don.fedyk@hp.com

   Ali Sajassi
   Cisco
   170 West Tasman Drive
   San Jose, CA  95134,
   USA
   Email: sajassi@cisco.com




















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