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INTERNET-DRAFT                                              Sami Boutros
Intended Status: Standard Track                              Ali Sajassi
                                                             Samer Salam
                                                           Cisco Systems

                                                              John Drake
                                                        Juniper Networks

                                                           Jeff Tantsura

                                                          Dirk Steinberg
                                                    Steinberg Consulting
Expires: August 18, 2014                               February 14, 2014

                         VPWS support in E-VPN


   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: single-active as well as all-
   active multi-homing with flow-based load-balancing, eliminates the
   need for single-segment and multi-segment PW signaling, and provides
   fast protection using data-plane prefix independent convergence upon
   node or link failure.

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 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

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

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
     1.1  Terminology . . . . . . . . . . . . . . . . . . . . . . . .  3
     1.2 Requirements . . . . . . . . . . . . . . . . . . . . . . . .  4
   2. BGP Extensions  . . . . . . . . . . . . . . . . . . . . . . . .  5
   3 Operation  . . . . . . . . . . . . . . . . . . . . . . . . . . .  5
   4 EVPN Comparison to PW Signaling  . . . . . . . . . . . . . . . .  6
   5 ESI Bandwidth  . . . . . . . . . . . . . . . . . . . . . . . . .  7
   6 ESI value derivation and Eth-tag setting . . . . . . . . . . . .  7
   7 VPWS with multiple sites . . . . . . . . . . . . . . . . . . . .  8
   8 Security Considerations  . . . . . . . . . . . . . . . . . . . .  8
   9  IANA Considerations . . . . . . . . . . . . . . . . . . . . . .  8
   10  References . . . . . . . . . . . . . . . . . . . . . . . . . .  8
     10.1  Normative References . . . . . . . . . . . . . . . . . . .  8
     10.2  Informative References . . . . . . . . . . . . . . . . . .  8
   Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . .  9

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1  Introduction

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

   [EVPN] has the ability to forward customer traffic to/from a given
   customer Attachment Circuit (AC), aka Ethernet Segment in EVPN
   terminology, without any MAC lookup. This capability is ideal in
   providing p2p services (aka VPWS services). [MEF] defines Ethernet
   Virtual Private Line (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, the traffic forwarding
   capability of EVPN based on the exchange of a pair of Ethernet AD
   routes is used; whereas, for more general VPWS, traffic forwarding
   capability of EVPN based on the exchange of a group of Ethernet AD
   routes (one Ethernet AD route per AC/segment) is used. In a VPWS
   service,  the traffic from an originating Ethernet Segment can be
   forwarded only to a single destination Ethernet Segment; hence, no
   MAC lookup is needed and the MPLS label associated with the per-EVI
   Ethernet 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 EVPN 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 EVPN, the Ethernet Segment
   route can be used to synchronize state between the PEs attached to
   the same multi-homed Ethernet Segment.

1.1  Terminology

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   document are to be interpreted as described in RFC 2119 [RFC2119].

   MAC: Media Access Control

   MPLS: Multi Protocol Label Switching.

   OAM: Operations, Administration and Maintenance.

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   PE: Provide Edge Node.

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

   EVI: EVPN Instance.

   Single-Active Mode: When a device or a network is multi-homed to two
   or more PEs and when only a single PE in such redundancy group can
   forward traffic to/from the multi-homed device or network for a given
   VLAN, then such multi-homing or redundancy is referred to as "Single-

   All-Active: When a device is multi-homed to two or more PEs and when
   all PEs in such redundancy group can forward traffic to/from the
   multi-homed device for a given VLAN, then such multi-homing or
   redundancy is referred to as "All-Active".

1.2 Requirements

   1. EPL service access circuit maps to the whole Ethernet port.

   2. EVPL service access circuits are VLANs on single or double tagged
   trunk ports. Each VLAN individually will be considered to be an
   endpoint for an EVPL service, without any direct dependency on any
   other VLANs on the trunk. Other VLANs on the same trunk could also be
   used for EVPL services, but could also be associated with other

   3. If multiple VLANs on the same trunk are associated with EVPL
   services, the respective remote endpoints of these EVPLs could be
   dispersed across any number of PEs, i.e. different VLANs may lead to
   different destinations.

   4. The VLAN tag on the access trunk only has PE-local significance.
   The VLAN tag on the remote end could be different, and could also be
   double tagged when the other side is single tagged.

   5. Also, multiple EVPL service VLANs on the same trunk could belong
   to the same EVPN instance (EVI), or they could belong to different
   EVIs. This should be purely an administrative choice of the network

   6. A given access trunk could have hundreds of EVPL services, and a
   given PE could have thousands of EVPLs configured. It must be
   possible to configure multiple EVPL services within the same EVI.

   7. Local access circuits configured to belong to a given EVPN
   instance could also belong to different physical access trunks.

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2. BGP Extensions

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

   This document proposes the use of the per EVI 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-Target (RT)
   extended community that identifies the VPN associated with the p2p
   EVPLs where each EVPL is identified by <ESI,Eth tag>.

3 Operation

   The following figure shows an example of a P2P service deployed with
          Ethernet                                          Ethernet
          Native   |<--------- EVPN 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      |
           |                          |                             |
           |                          |                             |
           |              EVPN Inter-provider point                 |
           |                                                        |
           |<---------------- Emulated Service -------------------->|

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

   All PEs and ASBRs are enabled for the EVPN SAFI, and exchange EVPN
   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

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   addresses. The link between the CE and the PE is either a C-tagged or
   S-tagged interface, as described in [802.1Q], that can carry a single
   VLAN tag or two nested VLAN tags. This interface is set up 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 single-homing the ESI field must be set to 0 in the Ethernet
   AD route, the <Eth-tag> field will be set to the AC-ID of the EVPL or
   EPL service.

   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 AC ID encoded in the
   tag field 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

   The <Eth-tag> field of the EVI EAD route represents the AC-ID of the
   EPL and EVPL service.

   EPL service need to be identified by a non 0 <Eth-tag> field in the
   Ethernet AD route.

   The <Eth-tag> field value representing the AC-ID of the EPL/EVPL
   service of the remote side may be equal to the local side.

   An operator may choose to associate many per EVI EAD routes with
   different ESIs and tags to the same Route-Target (RT) extended
   community attribute. As such, the association of per EVI EAD routes
   to the same RT is a network operator design choice.

   Per ES EAD route can be used for mass withdraw to withdraw all per
   EVI EAD routes associated with the multi-home site on a given PE.

   The VLANs on the two ACs of a given EVPL service may have different
   VLANs. EVPN doesn't perform that translation, and that it should be
   handled by the Ethernet interface.

4 EVPN Comparison to PW Signaling

   In EVPN, 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

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   through manual provisioning or through BGP.

   In existing implementation of VPWS using pseudowires(PWs), redundancy
   is limited to single-active mode, while with EVPN implementation of
   VPWS both single-active and all-active redundancy modes can be

   In existing implementation with PWs, backup PWs are not used to carry
   traffic, while with EVPN, traffic can be load-balanced among
   different PEs multi-homed to a single CE.

   Upon link or node failure, EVPN can trigger failover with the
   withdrawal of a single BGP route per EVPL service or multiple EVPL
   services, 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,
   EVPN may employ data plane local repair mechanisms not available in

5 ESI Bandwidth

   The ESI Bandwidth will be encoded using the Link Bandwidth Extended
   community defined in [draft-ietf-idr-link-bandwidth] and associated
   with the Ethernet AD route used to realize the EVPL services.

   When a PE receives this attribute for a given EVPL it MUST request
   the required bandwidth from the PSN towards the other EVPL service
   destination PE originating the message. When resources are allocated
   from the PSN for a given EVPL service, then the PSN SHOULD account
   for the Bandwidth requested by this EVPL service.

   In the case where PSN resources are not available, the PE receiving
   this attribute MUST re-send its local Ethernet AD routes for this
   EVPL service with the ESI Bandwidth = All FFs to declare that the
   "PSN Resources Unavailable".

   The scope of the ESI Bandwidth is limited to only one Autonomous

6 ESI value derivation and Eth-tag setting

   The ESI value is set per [EVPN] procedures - e.g.,  it is set to 0
   for single home sites and can be manually configured or auto-derived
   for multi-homed sites.

   The <Eth-tag> field in the Ethernet A-D per EVI route is set to the
   AC-ID representing the EPL or EVPL service. This is different from

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   the baseline [EVPN] Where <Eth-tag> field is set only for VLAN-aware
   bundle service.

   The AC-ID value SHOULD be the same at both sides of the EPL or EVPL
   service and it SHOULD be unique within an AS.

   "EVI" for VPWS services MUST be different from multipoint services
   specified in baseline [EVPN]. This implies the corresponding RTs for
   VPWS and multipoint services needs to be different.

   AC-IDs in the <Eth-tag> field MUST be unique within one AS, an ASBR
   MAY be required to perform AC-IDs translations if the AC-IDs are not
   unique across multiple ASs.

   Local and remote AC-IDs of a given EVPL or EPL service, are
   configured by an operator to connect the 2 sides of the EPL/EVPL
   services at both sides of the services.

7 VPWS with multiple sites

   The VPWS among multiple sites (full mesh of P2P connections - one per
   pair of sites) that can be setup automatically without any explicit
   provisioning of P2P connections among the sites is outside the scope
   of this document.

8 Security Considerations

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


10  References

10.1  Normative References

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

10.2  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-04.txt.

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   [PBB-EVPN] A. Sajassi et. al., "PBB-EVPN", draft-ietf-l2vpn-pbb-evpn-

   [draft-ietf-idr-link-bandwidth] P. Mohapatra, R. Fernando, "BGP Link
   Bandwidth Extended Community", draft-ietf-idr-link-bandwidth-06.txt

Authors' Addresses

   Sami Boutros
   Email: sboutros@cisco.com

   Ali Sajassi
   Email: sajassi@cisco.com

   Samer Salam
   Email: ssalam@cisco.com

   John Drake
   Juniper Networks
   Email: jdrake@juniper.net

   Jeff Tantsura
   Email: jeff.tantsura@ericsson.com

   Dirk Steinberg
   Steinberg Consulting
   Email: dws@steinbergnet.net

   Patrice Brissette
   Email: pbrisset@cisco.com

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