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Versions: 00 01 02 03 04 05 06 draft-ietf-bess-evpn-vpws

INTERNET-DRAFT                                              Sami Boutros
Intended Status: Informational                               Ali Sajassi
                                                             Samer Salam
Expires: January 1, 2013                                   June 30, 2012


                         VPWS support in E-VPN
                  draft-boutros-l2vpn-evpn-vpws-00.txt


Abstract

   This document describes how E-VPN can be used to support virtual
   private wire service (VPWS) in MPLS/IP networks. E-VPN enables the
   following characteristics for VPWS: 1) active/standby redundancy, 2)
   active/active multi-homing with flow-based load-balancing, 3)
   eliminates the need for single-segment and multi-segment PW
   signaling, and 4) provides faster convergence using data-plane prefix
   independent convergence upon node or link failure in comparison to
   control-plane convergence with PW redundancy.


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


Copyright and License Notice

   Copyright (c) 2012 IETF Trust and the persons identified as the
   document authors. All rights reserved.



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   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
     1.1  Terminology . . . . . . . . . . . . . . . . . . . . . . . .  3
   2. BGP Extensions  . . . . . . . . . . . . . . . . . . . . . . . .  4
   3 Operation  . . . . . . . . . . . . . . . . . . . . . . . . . . .  4
   4 E-VPN Comparison to PW Signaling . . . . . . . . . . . . . . . .  5
   5 VPWS with multiple sites . . . . . . . . . . . . . . . . . . . .  5
   6 Security Considerations  . . . . . . . . . . . . . . . . . . . .  6
   7  IANA Considerations . . . . . . . . . . . . . . . . . . . . . .  6
   8  References  . . . . . . . . . . . . . . . . . . . . . . . . . .  6
     8.1  Normative References  . . . . . . . . . . . . . . . . . . .  6
     8.2  Informative References  . . . . . . . . . . . . . . . . . .  6
   Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . .  6

























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1  Introduction

   This document describes how E-VPN can be used to support virtual
   private wire service (VPWS) in MPLS/IP networks. The use of E-VPN
   mechanisms for VPWS introduces all the benefits of E-VPN to p2p
   services. These benefits include active/standby AC redundancy,
   active/active multi-homing with flow-based load-balancing.
   Furthermore, the use of E-VPN for VPWS eliminates the need for
   signaling single-segment and multi-segment PWs for p2p Ethernet
   services.

   [E-VPN] has the ability to forward customer traffic to/from a given
   customer Attachment Circuit (aka Ethernet AD route) without any MAC
   lookup. This capability is ideal in providing P2P services (aka VPWS
   services). [MEF] defines EVPL service as P2P service between a pair
   of ACs (designated by VLANs). EVPL can be considered as a VPWS with
   only two ACs. In delivering an EVPL service, traffic forwarding
   capability of E-VPN between a pair of Ethernet AD routes is used;
   whereas, for more general VPWS, traffic forwarding capability of E-
   VPN among a group of Ethernet AD routes (one Ether AD route per
   AC/site) is used. Since in VPWS services,  the traffic from an
   originating Ether AD route can go only to a single destination Ether
   AD route, no MAC lookup is needed and MPLS label associated with the
   destination Ether AD route can be used in forwarding user traffic to
   the destination AC.

   In current PW redundancy mechanisms, convergence time is a function
   of control plane convergence characteristics. However, with E-VPN it
   is possible to attain faster convergence through the use of data-
   plane prefix independent convergence upon node or link failure.

   This document proposes the use of the Ethernet AD route to signal
   labels for P2P Ethernet services. As with E-VPN, the Ethernet Segment
   route can be used to synchronize LACP and other state between the PEs
   attached to the same multi-homed device.



1.1  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].

   MAC: Media Access Control

   MPLS: Multi Protocol Label Switching.




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   OAM: Operations, Administration and Maintenance.

   PE: Provide Edge Node.

   CE: Customer Edge device e.g., host or router or switch.

   EVI: E-VPN Instance.


2. BGP Extensions


   [E-VPN] defines a new BGP NLRI for advertising different route types
   for E-VPN operation. This document does not define any new BGP
   messages, but rather repurposes one of the routes as described next.

   This document proposes the use of the Ethernet AD route to signal P2P
   services. The Ethernet Segment Identifier field is set to the ESI of
   the attachment circuit of the VPWS service instance. The Ethernet Tag
   field is set to 0 in the case of an Ethernet Private Wire service,
   and to the VLAN identifier associated with the service for Ethernet
   Virtual Private Wire service. The route is associated with a Route-
   Target (RT) extended community attribute that identifies the service
   instance (together with the Ethernet Tag field when non-zero

3 Operation

   The following figure shows an example of a P2P service deployed with
   E-VPN.
          Ethernet                                          Ethernet
          Native   |<---------E-VPN Instance------------>|  Native
          Service  |                                     |  Service
           (AC)    |     |<-PSN1->|       |<-PSN2->|     |  (AC)
             |     V     V        V       V        V     V  |
             |     +-----+      +-----+  +-----+   +-----+  |
      +----+ |     | PE1 |======|ASBR1|==|ASBR2|===| PE3 |  |    +----+
      |    |-------+-----+      +-----+  +-----+   +-----+-------|    |
      | CE1| |                                              |    |CE2 |
      |    |-------+-----+      +-----+  +-----+   +-----+-------|    |
      +----+ |     | PE2 |======|ASBR3|==|ASBR4|===| PE4 |  |    +----+
           ^       +-----+      +-----+  +-----+   +-----+          ^
           |   Provider Edge 1        ^        Provider Edge 2      |
           |                          |                             |
           |                          |                             |
           |              E-VPN Inter-provider point                |
           |                                                        |
           |<---------------- Emulated Service -------------------->|




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   iBGP sessions will be established between PE1, PE2, ASBR1 and ASBR3,
   possibly via a BGP route-reflector. Similarly, iBGP sessions will be
   established between PE3, PE4, ASBR2 and ASBR4. eBGP sessions will be
   established among ASBR1, ASBR2, ASBR3, and ASBR4.

   All PEs and ASBRs are enabled for the E-VPN SAFI, and exchange E-VPN
   Ethernet A-D routes - one route per AC. The ASBRs re-advertise the
   Ethernet A-D routes with Next Hop attribute set to their IP
   addresses. The link between the CE and the PE is an C-TAG or S-TAG
   interface as described in [802.1Q] that can carry a single vlan tag
   or two vlan tags nested in each other. This interface is setup as a
   trunk with multiple VLANs.

   A VPWS with multiple sites or multiple EVPL services on the same CE
   port can be included in one EVI between 2 or more PEs. An Ethernet
   Tag corresponding to each P2P connection and known to both PEs is
   used to identify the services multiplexed in the same EVI. For CE
   multi-homing, the Ethernet AD Route encodes the ESI associated with
   the CE. This allows flow-based load-balancing of traffic between PEs
   connected to the same multi-homed CE. The VPN ID MUST be the same on
   both PEs attached to the site. The Ethernet Segment route may be used
   too, for discovery of multi-homed CEs. In all cases traffic follows
   the transport paths, which may be asymmetric.

4 E-VPN Comparison to PW Signaling

   In E-VPN, service endpoint discovery and label signaling are done
   concurrently using BGP. Whereas, with VPWS based on [RFC4448], label
   signaling is done via LDP and service endpoint discovery is either
   through manual provisioning or through BGP. In VPWS, redundancy is
   limited to Active/Standby mode, while with E-VPN both Active/Active
   and Active/Standby redundancy modes can be supported. In VPWS, backup
   PWs are not used to carry traffic, while E-VPN traffic can be load-
   balanced among primary and secondary PEs. On link or node failure, E-
   VPN can trigger failover with the withdrawal of a single BGP route
   per service, whereas with VPWS PW redundancy, the failover sequence
   requires exchange of two control plane messages: one message to
   deactivate the group of primary PWs and a second message to activate
   the group of backup PWs associated with the access link. Finally, E-
   VPN may employ data plane local repair mechanisms not available in
   VPWS.

5 VPWS with multiple sites

   The future revision of this draft will describe how a VPWS among
   multiple sites (full mesh of P2P connections - one per pair of sites)
   can be setup automatically without any explicit provisioning of P2P
   connections among the sites.



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6 Security Considerations

   This document does not introduce any additional security constraints.
7  IANA Considerations

   TBD

8  References

8.1  Normative References

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


8.2  Informative References

   [EVPN-REQ] A. Sajassi, R. Aggarwal et. al., "Requirements for
   Ethernet VPN", draft-ietf-l2vpn-evpn-req-00.txt.

   [EVPN] A. Sajassi, R. Aggarwal et. al., "BGP MPLS Based Ethernet
   VPN", draft-ietf-l2vpn-evpn-00.txt.



Authors' Addresses


   Sami Boutros
   Cisco
   170 West Tasman Drive
   San Jose, CA  95134, US
   Email: sboutros@cisco.com

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

   Samer Salam
   Cisco
   595 Burrard Street, Suite 2123
   Vancouver, BC V7X 1J1, Canada
   Email: ssalam@cisco.com






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