802.1aq and 802.1Qbp Support over EVPN
draft-allan-l2vpn-spbm-evpn-03

L2VPN Working Group                           Dave Allan, Jeff Tantsura 
Internet Draft                                                 Ericsson 
Intended status: Standards Track                              Don Fedyk         
Expires: August 2013                                     Alcatel-Lucent 
                                                            Ali Sajassi 
                                                                  Cisco 
 
                                                          February 2013 
                                    

                  802.1aq and 802.1Qbp Support over EVPN 
                      draft-allan-l2vpn-spbm-evpn-03 

Abstract 

   This document describes how Ethernet Shortest Path Bridging MAC mode 
   (802.1aq) and (802.1Qbp) can be combined with EVPN in a way that 
   interworks with PBB-PEs as described in the PBB-EVPN solution in a 
   way that permits operational isolation of each Ethernet network 
   subtending an EVPN core while supporting full interworking between 
   the 3 variations of Ethernet operation.    

Status of this Memo 

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

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   This Internet-Draft will expire on August 2013. 

Copyright and License Notice 

 
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   Copyright (c) 2013 IETF Trust and the persons identified as the 
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Table of Contents 

   1. Introduction...................................................3 
   1.1. Authors......................................................3 
   1.2. Requirements Language........................................3 
   2. Conventions used in this document..............................3 
   2.1. Terminology..................................................3 
   3. Changes since previous version.................................4 
   4. Solution Overview..............................................4 
   5. Elements of Procedure..........................................5 
   5.1. PE Configuration.............................................5 
   5.2. DF Election..................................................6 
   5.3. Control plane interworking ISIS-SPB to EVPN..................6 
   5.4. Control plane interworking EVPN to ISIS-SPB..................6 
   5.5. Data plane Interworking 802.1aq SPBM island or PBB-PE to 
   EVPN..............................................................8 
   5.6. Data plane Interworking EVPN to 802.1aq SPBM island..........8 
   5.7. Data plane interworking EVPN to 802.1ah PBB-PE...............8 
   5.8. Dataplane interworking between 802.1Qbp islands and EVPN.....8 
   5.9. Multicast Stitching..........................................8 
   6. Other Aspects..................................................8 
   6.1. Flow Ordering................................................8 
   6.2. Transit......................................................9 
   7. Acknowledgements...............................................9 
   8. Security Considerations........................................9 
   9. IANA Considerations............................................9 
   10. References....................................................9 
   10.1. Normative References........................................9 
   10.2. Informative References......................................9 
   11. Authors' Addresses...........................................10 
    

 
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1. Introduction 

   This document describes how Ethernet Shortest Path Bridging MAC mode 
   (802.1aq) and (802.1Qbp) along with PBB-PEs and PBBNs (802.1ah) can 
   be supported by EVPN such that each island is operationally isolated 
   while providing full L2 connectivity between them. Each island can 
   use its own control plane instance and multi-pathing design, be it 
   multiple ECT sets, multiple spanning trees, or ECMP. 

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

1.1. Authors 

   David Allan, Jeff Tantsura, Don Fedyk, Ali Sajassi 

1.2. 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 [1]. 

2. Conventions used in this document 

2.1. Terminology 

      BCB: Backbone Core Bridge 
      BEB: Backbone Edge Bridge 
      BU: Broadcast/Unknown 
      B-MAC: Backbone MAC Address 
      B-VID: Backbone VLAN ID 
      CE: Customer Edge 
      C-MAC: Customer/Client MAC Address 
      DF: Designated Forwarder 
      ESI: Ethernet segment identifier 
      EVPN: Ethernet VPN  
      ISIS-SPB: IS-IS as extended for SPB 
      I-SID: I-Component Service ID 
      MP2MP: Multipoint to Multipoint 

 
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      MVPN: Multicast VPN 
      NLRI: Network layer reachability information 
      PBBN: Provider Backbone Bridged Network 
      PBB-PE: Co located BEB and PE 
      PE: provider edge 
      P2MP: Point to Multipoint 
      P2P: Point to Point 
      RD: Route Distinguisher 
      SPB: Shortest path bridging 
      SPBM: Shortest path bridging MAC mode  
       
3. Changes since previous version 

  1) Reverting to NLRI encoding aligned with the PBB-EVPN draft. 

4. Solution Overview 

The EPVN solution for 802.1aq SPBM incorporates control plane 
interworking in the PE to map ISIS-SPB [2] information elements into the 
EVPN NLRI information 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 subtending SPB islands may be 
interconnected without any topological or multipathing dependencies. 
This requires each PE connected to an SPBM island to act both as an EVPN 
BGP speaker and as an ISIS-SPB edge node. This model also permits PBB-
PEs as defined in draft-l2vpn-pbb-evpn-02[6] to be seamlessly 
communicate with the SPB islands. The next version of this document will 
add support for 802.1Qbp permitting seamless interworking between 
802.1ah, 802.1aq and 802.1Qbp as well as supporting subtending 802.1ad 
based PBNs. 

                         +--------------+  
                         |              |  
                         |              |   
      +-----+     +----+ |              | +----+   +---+ 
      |     |-----|SPBM| |              | |PBB |---|CE2| 
      |SPBM |     |PE1 | |   IP/MPLS    | |PE1 |   +---+ 
+---+ |NTWK1|     +----+ |   Network    | +----+  
 
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|CE1|-|     |            |              | 
+---+ |     |     +----+ |              |                  
      |     |-----|SPBM| |              | +----+   +-----+              
      +-----+     |PE2 | |              | |SPBM|   |SPBM | +---+ 
                  +----+ |              | |PE3 |---|NTWK2|-|CE3| 
                         +--------------+ +----+   +-----+ +---+  
            Figure 1: PBB and SPBM EVPN Network 
 
Each EVPN is identified by a route target. The route target identifies 
the set of SPB islands and BEB-PEs that are allowed to communicate. This 
manifests itself as a set of Ethernet segments, where each Ethernet 
segment ID is unique within the route target. 
BGP acts as a common repository of the I-SID attachment points for the 
set of subtending PEs/SPBM islands. This is in the form of B-MAC 
address/I-SID/Tx-Rx-attribute tuples. BGP filters leaking I-SID 
information into each SPBM ISLAND on the basis of locally registered 
interest. If an SPBM ISLAND has no BEBs registering interest in an I-
SID, information about that I-SID from other SPBM island, PBB-PEs or 
PBBNs will not be leaked into the local ISIS-SPB routing system. 
Each SPBM island is administered to have an associated Ethernet Segment 
ID (ESI) associated with it.  
For each B-VID in an SPBM island, a single SPBM-PE is elected the 
designated forwarder for the B-VID. An SPBM-PE may 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 I-BEB or IB-BEB that 
proxy for the other SPBM islands and PBB PEs in the VPN 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 strips the B-VID tag information 
from frames relayed towards the EVPN. The DF also inserts 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. 
                                   
5. Elements of Procedure 

5.1. 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 service 
      instance is defined as 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 
      common ESI for the SPBM island are for a future version of the 
      document. 

   And 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 DA addresses. Note this is required for 
      SPBM BEBs independent of the EVPN operation. 

   2) The set of VLANs (identified by B-VIDs Ethernet frames) used in 
      the SPBM island and multipathing algorithm IDs to use. The B-VID 
      may be different in different domains and may be removed as 
      carried over the IP/MPLS network. 

   A type-1 RD for the node can be auto-derived. This will be described 
   in a future version of the document.  

5.2. DF Election 

   PEs self appoint in the role of DF for a B-VID for a given SPBM 
   island. The procedure used is as per section 9.5.2 of draft-ietf-
   l2vpn-evpn-01[4] "DF election with service carving". 
    
5.3. 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 
   advertisement route NLRI is created for each new I-SID in the sub-
   TLV. 

   - the Route Distinguisher (RD) 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. 

 
 
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       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 from the sub-TLV 

   - an 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 
   SPB 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 
   fraPE 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 this 
   will be in a future version of the document.  

5.4. Control plane interworking EVPN to ISIS-SPB 

   When a PE receives a BGP NLRI that is new information, it checks 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 is of 
   local interest to the SPBM island and the PE is the DF for the B-VID 
   that that I-SID is locally mapped to, a SPBM service identifier and 
   unicast address sub-TLV is constructed/updated for advertisement into 
   IS-IS. 

   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 

 
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   label stack to impose on the SPBM frame. The bottom label being that 
   offered in the NLRI. 

5.5. 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. 

5.6. Data plane Interworking EVPN to 802.1aq SPBM island 

   When a PE receives a packet from the EVPN it may 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 DA, it overwrites the SPsourceID 
   in the frame with the local SPsourceID. 

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

   A PBB-PE actually has no subtending 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. 

5.8. Data plane interworking between 802.1Qbp islands and EVPN 

   For a future version of the document 

5.9. Multicast Stitching 

   For a future version of the document 

6. Other Aspects 

6.1. Flow Ordering 

   When per I-SID multicast is implemented via PE replication, a stable 
   network will preserve frame ordering between known unicast and BU 
   traffic (e.g. race conditions will not exist). This cannot be 
   guaranteed when multicast is used in the EVPN. 

 
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6.2. Transit 

   Any PE that does not need to participate in the tandem calculations 
   may use the IS-IS overload bit to exclude SPBM tandem paths and 
   behave as pure interworking platform. 
7. Acknowledgements 

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

8. Security Considerations 

   For a future version of this document. 

9. IANA Considerations 

   For a future version of this document. 

10. References  

10.1. Normative References  

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

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

  [3]   Rosen et.al., "BGP/MPLS IP Virtual Private Networks 
        (VPNs)", IETF RFC 4364, February 2006 

  [4]   Aggarwal et.al. "BGP MPLS Based Ethernet VPN", IETF work 
        in progress, draft-ietf-l2vpn-evpn-01, July 2012 

10.2. Informative References 

  [5]   IEEE Standard for Local and Metropolitan Area Networks: 
        Bridges and Virtual Bridged Local Area Networks - 
        Amendment 9: Shortest Path Bridging 

  [6]   Draft IEEE Standard for Local and Metropolitan Area 
        Networks---Virtual Bridged Local Area Networks - 
        Amendment: Equal Cost Multiple Paths (ECMP), 802.1Qbp 
        draft 1.0 

  [7]   Sajassi et.al. "PBB E-VPN", IETF work in progress, draft-
        ietf-l2vpn-pbb-evpn-03, June 2012 
 
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  [8]   802.1Q (2011) IEEE Standard for Local and metropolitan 
        area networks--Media Access Control (MAC) Bridges and 
        Virtual Bridged Local Area Networks 

    

11. 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 
   Email: jeff.tantsura@ericsson.com 
    
   Don Fedyk 
   Alcatel-Lucent 
   Groton, MA  01450 
   USA 
   EMail: Donald.Fedyk@alcatel-lucent.com 
    
   Ali Sajassi 
   Cisco 
   170 West Tasman Drive 
   San Jose, CA  95134, US 
   Email: sajassi@cisco.com 
    

 
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