[Docs] [txt|pdf] [Tracker] [Email] [Diff1] [Diff2] [Nits]

Versions: 00 01 03

BESS Workgroup                                                A. Sajassi
INTERNET-DRAFT                                              P. Brissette
Intended Status: Standards Track                                   Cisco
                                                               J. Uttaro
                                                                     ATT
                                                                J. Drake
                                                                  W. Lin
                                                                 Juniper
                                                              S. Boutros
                                                                  VMWare
                                                              J. Rabadan
                                                                   Nokia

Expires: August 26, 2018                               February 26, 2018


               EVPN VPWS Flexible Cross-Connect Service
                draft-sajassi-bess-evpn-vpws-fxc-03.txt


Abstract

   This document describes a new EVPN VPWS service type specifically for
   multiplexing multiple attachment circuits across different Ethernet
   Segments and physical interfaces into a single EVPN VPWS service
   tunnel and still providing Single-Active and All-Active multi-homing.
   This new service is referred to as flexible cross-connect service. It
   also describes the rational for this new service type as well as a
   solution to deliver such service.


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



Sajassi et al.          Expires August 26, 2018                 [Page 1]


INTERNET DRAFT          EVPN VPWS Flex Xconnect        February 26, 2018


   The list of Internet-Draft Shadow Directories can be accessed at
   http://www.ietf.org/shadow.html

Copyright and License Notice

   Copyright (c) 2018 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
   2 Requirements . . . . . . . . . . . . . . . . . . . . . . . . . .  4
   4 Solution . . . . . . . . . . . . . . . . . . . . . . . . . . . .  6
     4.1 Flexible Xconnect  . . . . . . . . . . . . . . . . . . . . .  7
     4.2 VLAN-Signaled Flexible Xconnect  . . . . . . . . . . . . . .  8
       4.2.1 Local Switching  . . . . . . . . . . . . . . . . . . . .  9
   5. BGP Extensions  . . . . . . . . . . . . . . . . . . . . . . . .  9
   6 Failure Scenarios  . . . . . . . . . . . . . . . . . . . . . . . 11
     6.1 EVPN VPWS service Failure  . . . . . . . . . . . . . . . . . 13
     6.2 Attachment Circuit Failure . . . . . . . . . . . . . . . . . 13
     6.3 PE Port Failure  . . . . . . . . . . . . . . . . . . . . . . 14
     6.4 PE Node Failure  . . . . . . . . . . . . . . . . . . . . . . 14
   7  Security Considerations . . . . . . . . . . . . . . . . . . . . 14
   8  IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 14
   9  References  . . . . . . . . . . . . . . . . . . . . . . . . . . 14
     9.1  Normative References  . . . . . . . . . . . . . . . . . . . 14
     9.2  Informative References  . . . . . . . . . . . . . . . . . . 15
   Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 15









Sajassi et al.          Expires August 26, 2018                 [Page 2]


INTERNET DRAFT          EVPN VPWS Flex Xconnect        February 26, 2018


1  Introduction

   [RFC8214] describes a solution to deliver P2P services using BGP
   constructs defined in [RFC7432]. It delivers this P2P service between
   a pair of Attachment Circuits (ACs), where an AC can designate on a
   PE, a port, a VLAN on a port, or a group of VLANs on a port. It also
   leverages multi-homing and fast convergence capabilities of [RFC7432]
   in delivering these VPWS services. Multi-homing capabilities include
   the support of single-active and all-active redundancy mode and fast
   convergence is provided using "mass withdraw" message in control-
   plane and fast protection switching using prefix independent
   convergence in data-plane upon node or link failure [BGP-PIC].
   Furthermore, the use of EVPN BGP constructs eliminates the need for
   multi-segment PW auto-discovery and signaling if the VPWS service
   need to span across multiple ASes.

   Some service providers have very large number of ACs (in millions)
   that need to be back hauled across their MPLS/IP network. These ACs
   may or may not require tag manipulation (e.g., VLAN translation).
   These service providers want to multiplex a large number of ACs
   across several physical interfaces spread across one or more PEs
   (e.g., several Ethernet Segments) onto a single VPWS service tunnel
   in order to a) reduce number of EVPN service labels associated with
   EVPN-VPWS service tunnels and thus the associated OAM monitoring, and
   b) reduce EVPN BGP signaling (e.g., not to signal each AC as it is
   the case in [RFC8214]).

   These service provider want the above functionality without
   scarifying any of the capabilities of [RFC8214] including single-
   active and all-active multi-homing, and fast convergence.

   This document presents a solution based on extensions to [RFC8214] to
   meet the above requirements.


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

   OAM: Operations, Administration and Maintenance

   PE: Provide Edge Node



Sajassi et al.          Expires August 26, 2018                 [Page 3]


INTERNET DRAFT          EVPN VPWS Flex Xconnect        February 26, 2018


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

   EVPL: Ethernet Virtual Private Line

   EPL: Ethernet Private Line

   ES: Ethernet Segment

   VPWS: Virtual private wire service

   EVI: EVPN Instance

   VPWS Service Tunnel: It is represented by a pair of EVPN service
   labels associated with a pair of endpoints. Each label is downstream
   assigned and advertised by the disposition PE through an Ethernet A-D
   per-EVI route. The downstream label identifies the endpoint on the
   disposition PE. A VPWS service tunnel can be associated with many
   VPWS service identifiers for VLAN-signaled VPWS service where each
   identifier is a normalized VID.

   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-
   Active".

   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".


2 Requirements

   Two of the main motivations for service providers seeking a new
   solution are: 1) to reduce number of VPWS service tunnels by
   multiplexing large number of ACs across different physical interfaces
   instead of having one VPWS service tunnel per AC, and 2) to reduce
   the signaling of ACs as much as possible. Besides these two
   requirements, they also want multi-homing and fast convergence
   capabilities of [RFC8214].

   In [RFC8214], a PE signals an AC indirectly by first associating that
   AC to a VPWS service tunnel (e.g., a VPWS service instance) and then
   signaling the VPWS service tunnel via a per-EVI Ethernet AD route
   with Ethernet Tag field set to a 24-bit VPWS service instance
   identifier (which is unique within the EVI) and ESI field set to a
   10-octet identifier of the Ethernet Segment corresponding to that AC.



Sajassi et al.          Expires August 26, 2018                 [Page 4]


INTERNET DRAFT          EVPN VPWS Flex Xconnect        February 26, 2018


   Therefore, a PE device that receives such EVPN routes, can associate
   the VPWS service tunnel to the remote Ethernet Segment, and when the
   remote ES fails and the PE receives the "mass withdraw" message
   associated with the failed ES per [RFC7432], it can update its BGP
   path list for that VPWS service tunnel quickly and achieve fast
   convergence for multi-homing scenarios. Even if fast convergence were
   not needed, there would still be a need for signaling each AC failure
   (via its corresponding VPWS service tunnel) associated with the
   failed ES, so that the BGP path list for each of them gets updated
   accordingly and the packets are sent to backup PE (in case of single-
   active multi-homing) or to other PEs in the redundancy group (in case
   of all-active multi-homing). In absence of updating the BGP path
   list, the traffic for that VPWS service tunnel will be black-holed.

   When a single VPWS service tunnel multiplexes many ACs across number
   of Ethernet Segments (number of physical interfaces) and the ACs are
   not signaled via EVPN BGP to remote PE devices, then the remote PE
   devices neither know the association of the received Ethernet Segment
   to these ACs (and in turn to their local ACs) nor they know the
   association of the VPWS service tunnel (e.g., EVPN service label) to
   the far-end ACs - i.e, the remote PEs only know the association of
   their local ACs to the VPWS service tunnel but not the far-end ACs.
   Thus upon a connectivity failure to the ES, they don't know how to
   redirect traffic via another multi-homing PE to that ES. In other
   words, even if an ES failure is signaled via EVPN to the remote PE
   devices, they don't know what to do with such message because they
   don't know the association among the remote ES, the remote ACs, and
   the VPWS service tunnel.

   In order to address this issue when multiplexing large number of ACs
   onto a single VPWS service tunnel, two mechanisms are devised: one to
   support VPWS services between two single-homed endpoints and another
   one to support VPWS services where one of the endpoints is multi-
   homed. An endpoint can be an AC, MAC-VRF, IP-VRF, global table, or
   etc.

   For single-homed endpoints, it is OK not to signal each AC in BGP
   because upon connection failure to the ES, there is no alternative
   path to that endpoint. However, the ramification for not signaling an
   AC failure is that the traffic destined to the failed AC, is sent
   over MPLS/IP core and then gets discarded at the destination PE -
   i.e., it can waste network resources. However, when there is a
   connection failure, the application layer will eventually stop
   sending traffic and thus this wastage of network resources should be
   transient. Section 4.1 describes a solution for such single-homing
   VPWS service.

   For VPWS services where one of the endpoints is multi-homed, there



Sajassi et al.          Expires August 26, 2018                 [Page 5]


INTERNET DRAFT          EVPN VPWS Flex Xconnect        February 26, 2018


   are two options:

   1) to signal each AC via BGP so that the path list can be updated
   upon a failure that impacts those ACs. This solution is described in
   section 4.2 and it is called VLAN-signaled flexible cross-connect
   service.

   2) to bundle several ACs on an ES together per destination end-point
   (e.g., ES, MAC-VRF, etc.) and associated such bundle to a single VPWS
   service tunnel. This is similar to VLAN-bundle service interface
   described in [RFC8214]. This solution is described in section 4.3.



4 Solution

   This section describes a solution for providing a new VPWS service
   between two PE devices where a large number of ACs (e.g., VLANs) that
   span across many Ethernet Segments (i.e., physical interfaces) on
   each PE are multiplex onto a single P2P EVPN service tunnel. Since
   multiplexing is done across several physical interfaces, there can be
   overlapping VLAN IDs across these interfaces; therefore, in such
   scenarios, the VLAN IDs (VIDs) MUST be translated into unique VIDs to
   avoid collision. Furthermore, if the number of VLANs that are getting
   multiplex onto a single VPWS service tunnel, exceed 4K, then a single
   tag to double tag translation MUST be performed. This translation of
   VIDs into unique VIDs (either single or double) is referred to as
   "VID normalization". When single normalized VID is used, the lower
   12-bit of Ethernet tag field in EVPN routes is set to that VID and
   when double normalized VID is used, the lower 12-bit of Ethernet tag
   field is set to inner VID and the higher 12-bit is set to the outer
   VID.

   Since there is only a single EVPN VPWS service tunnel associated with
   many normalized VIDs (either single or double) across multiple
   physical interfaces, MPLS lookup at the disposition PE is no longer
   sufficient to forward the packet to the right egress
   endpoint/interface. Therefore, in addition to an EVPN label lookup
   corresponding to the VPWS service tunnel, a VID lookup (either single
   or double) is also required. On the disposition PE, one can think of
   the lookup of EVPN label results in identification of a VID-VRF, and
   the lookup of normalized VID(s) in that table, results in
   identification of egress endpoint/interface. The tag manipulation
   (translation from normalized VID(s) to local VID) can be performed
   either as part of the VID table lookup or at the egress interface
   itself.

   Since VID lookup (single or double) needs to be performed at the



Sajassi et al.          Expires August 26, 2018                 [Page 6]


INTERNET DRAFT          EVPN VPWS Flex Xconnect        February 26, 2018


   disposition PE, then VID normalization MUST be performed prior to the
   MPLS encapsulation on the ingress PE. This requires that both
   imposition and disposition PE devices be capable of VLAN tag
   manipulation, such as re-write (single or double), addition, deletion
   (single or double) at their endpoints (e.g., their ES's, MAC-VRFs,
   IP-VRFs, etc.).


4.1 Flexible Xconnect

   In this mode of operation, many ACs across several Ethernet Segments
   are multiplex into a single EVPN VPWS service tunnel represented by a
   single VPWS service ID. This is the default mode of operation for FXC
   and the participating PEs do not need to signal the VLANs (normalized
   VIDs) in EVPN BGP.

   With respect to the data-plane aspects of the solution, both
   imposition and disposition PEs are aware of the VLANs as the
   imposition PE performs VID normalization and the disposition PE does
   VID lookup and translation. In this solution, there is only a single
   P2P EVPN VPWS service tunnel between a pair of PEs for a set of ACs.

   As discussed previously, since the EVPN VPWS service tunnel is used
   to multiplex ACs across different ES's (e.g., physical interfaces),
   the EVPN label alone is not sufficient for proper forwarding of the
   received packets (over MPLS/IP network) to egress interfaces.
   Therefore, normalized VID lookup is required in the disposition
   direction to forward packets to their proper egress end-points -
   i.e., the EVPN label lookup identifies a VID-VRF and subsequently,
   the normalized VID lookup in that table, identifies the egress
   interface.

   This mode of operation is only suitable for single-homing because in
   multi-homing the association between EVPN VPWS service tunnel and
   remote AC changes during the failure and therefore the VLANs
   (normalized VIDs) need to be signaled.

   In this solution, on each PE, the single-homing ACs represented by
   their normalized VIDs are associated with a single EVPN VPWS service
   tunnel (in a given EVI). The EVPN route that gets generated is an
   EVPN Ethernet AD per EVI route with ESI=0, Ethernet Tag field set to
   VPWS service instance ID, MPLS label field set to dynamically
   generated EVPN service label representing the EVPN VPWS service
   tunnel. This route is sent with an RT representing the EVI. This RT
   can be auto-generated from the EVI per section 5.1.2.1 of [EVPN-
   Overlay]. Furthermore, this route is sent with the EVPN Layer-2
   Extended Community defined in section 3.1 of [RFC8214] with two new
   flags (defined in section 5) that indicate: 1) this VPWS service



Sajassi et al.          Expires August 26, 2018                 [Page 7]


INTERNET DRAFT          EVPN VPWS Flex Xconnect        February 26, 2018


   tunnel is for default Flexible Cross-Connect, and 2) normalized VID
   type (single versus double). The receiving PE uses these new flags
   for consistency check and MAY generate an alarm if it detects
   inconsistency but doesn't bring down the VPWS service.

   It should be noted that in this mode of operation, a single Ethernet
   AD per EVI route is sent upon configuration of the first AC (ie,
   normalized VID). Later, when additional ACs are configured and
   associated with this EVPN VPWS service tunnel, the PE does not
   advertise any additional EVPN BGP routes. The PE only associates
   locally these ACs with the already created VPWS service tunnel.

   The default FXC mode can be used for multi-homing. In this mode, a
   group of normalized VIDs (ACs) on a single Ethernet segment that are
   destined to a single endpoint are multiplexed into a single EVPN VPWS
   service tunnel represented by a single VPWS service ID. When the
   default FXC mode is used for multi-homing, instead of a single EVPN
   VPWS service tunnel, there can be many service tunnels per pair of
   PEs  - i.e, there is one tunnel per group of VIDs per pair of PEs and
   there can be many groups between a pair of PEs, thus resulting in
   many EVPN service tunnels.


4.2 VLAN-Signaled Flexible Xconnect

   In this mode of operation, just as the default FXC mode in section
   4.1, many normalized VIDs (ACs) across several different
   ES's/interfaces are multiplexed into a single EVPN VPWS service
   tunnel; however, this single tunnel is represented by many VPWS
   service IDs (one per normalized VID) and these normalized VIDs are
   signaled using EVPN BGP.

   In this solution, on each PE, the multi-homing ACs represented by
   their normalized VIDs are configured with a single EVI. There is no
   need to configure VPWS service instance ID in here as it is the same
   as the normalized VID. For each normalized VID on each ES, the PE
   generates an EVPN Ethernet AD per EVI route where ESI field
   represents the ES ID, the Ethernet Tag field is set to the normalized
   VID, MPLS label field is set to dynamically generated EVPN label
   representing the P2P EVPN service tunnel and it is the same label for
   all the ACs that are multiplexed into a single EVPN VPWS service
   tunnel. This route is sent with an RT representing the EVI. As
   before, this RT can be auto-generated from the EVI per section
   5.1.2.1 of [EVPN-Overlay]. Furthermore, this route is sent with the
   EVPN Layer-2 Extended Community defined in section 3.1 of [RFC8214]
   with two new flags (defined in section 5) that indicate: 1) this VPWS
   service tunnel is for VLAN-signaled Flexible Cross-Connect, and 2)
   normalized VID type (single versus double). The receiving PE uses



Sajassi et al.          Expires August 26, 2018                 [Page 8]


INTERNET DRAFT          EVPN VPWS Flex Xconnect        February 26, 2018


   these new flags for consistency check and MAY generate an alarm if it
   detects inconsistency but doesn't bring down the VPWS service.

   It should be noted that in this mode of operation, the PE sends a
   single Ethernet AD route for each AC that is configured - i.e., each
   normalized VID that is configured per ES results in generation of an
   EVPN Ethernet AD per EVI.

   This mode of operation provides automatic cross checking of
   normalized VIDs used for EVPL services because these VIDs are
   signaled in EVPN BGP. For example, if the same normalized VID is
   configured on three PE devices (instead of two) for the same EVI,
   then when a PE receives the second EVPN EAD per-EVI route, it
   generates an error message unless the two EVPN EAD per-EVI routes
   include the same ESI. Such cross-checking is not feasible in default
   FXC mode because the normalized VIDs are not signaled.


4.2.1 Local Switching

   When cross-connection is between two ACs belonging to two multi-homed
   Ethernet Segments on the same set of multi-homing PEs, then
   forwarding between the two ACs MUST be performed locally during
   normal operation (e.g., in absence of a local link failure) - i.e.,
   the traffic between the two ACs MUST be locally switched within the
   PE.

   In terms of control plane processing, this means that when the
   receiving PE receives an Ethernet A-D per-EVI route whose ESI is a
   local ESI, the PE does not alter its forwarding state based on the
   received route. This ensures that the local switching takes
   precedence over forwarding via MPLS/IP network. This scheme of
   locally switched preference is consistent with baseline EVPN [RFC
   7432] where it describes the locally switched preference for MAC/IP
   routes.

   In such scenarios, the Ethernet A-D per EVI route should be
   advertised with the MPLS label either associated with the destination
   Attachment Circuit or with the destination Ethernet Segment in order
   to avoid any ambiguity in forwarding. In other words, the MPLS label
   cannot represent the same VID-VRF used in section 4.2 because the
   same normalized VID can be reachable via two Ethernet Segments. In
   case of using MPLS label per destination AC, then this same solution
   can be used for VLAN-based VPWS or VLAN-bundle VPWS services per
   [RFC8214].


5. BGP Extensions



Sajassi et al.          Expires August 26, 2018                 [Page 9]


INTERNET DRAFT          EVPN VPWS Flex Xconnect        February 26, 2018


   This draft uses the EVPN Layer-2 attribute extended community defined
   in [RFC8214] with two additional flags added to this EC as described
   below. This EC is to be advertised with Ethernet A-D per EVI route
   per section 4.



           +------------------------------------+
           |  Type(0x06)/Sub-type(TBD)(2 octet) |
           +------------------------------------+
           |  Control Flags (2 octets)          |
           +------------------------------------+
           |  L2 MTU (2 octets)                 |
           +------------------------------------+
           |  Reserved (2 octets)               |
           +------------------------------------+



            0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5
           +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
           |   MBZ           | V | M |C|P|B|  (MBZ = MUST Be Zero)
           +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+


   The following bits in the Control Flags are defined; the remaining
   bits MUST be set to zero when sending and MUST be ignored when
   receiving this community.

        Name     Meaning

        B,P,C    per definition in [RFC8214]

        M        00 mode of operation as defined in [RFC8214]
                 01 VLAN-Signaled FXC
                 10 Default FXC



        V        00 operating per [RFC8214]
                 01 single-VID normalization
                 10 double-VID normalization


   The M and V fields are OPTIONAL on transmission and ignored at
   reception for forwarding purposes. They are used for error
   notifications.




Sajassi et al.          Expires August 26, 2018                [Page 10]


INTERNET DRAFT          EVPN VPWS Flex Xconnect        February 26, 2018


6 Failure Scenarios

   Two examples will be used as an example to analyze the failure
   scenarios.

   The first scenario is depicted in Figure 1 and shows the VLAN-
   signaled FXC mode with Multi-Homing. In this example:

   - CE1 is connected to PE1 and PE2 via (port,vid)=(p1,1) and (p3,3)
   respectively. CE1's VIDs are normalized to value 1 on both PEs, and
   CE1 is Xconnected to CE3's VID 1 at the remote end.

   - CE2 is connected to PE1 and PE2 via ports p2 and p4 respectively:
       o (p2,1) and (p4,3) identify the ACs that are used to Xconnect
          CE2 to CE4's VID 2, and are normalized to value 2.
       o (p2,2) and (p4,4) identify the ACs that are used to Xconnect
          CE2 to CE5's VID 3, and are normalized to value 3.

   In this scenario, PE1 and PE2 advertise an AD per-EVI route per
   normalized VID (values 1, 2 and 3), however only two VPWS Service
   Tunnels are needed: VPWS Service Tunnel 1 (sv.T1) between PE1's FXC
   service and PE3's FXC, and VPWS Service Tunnel 2 (sv.T2) between
   PE2's FXC and PE3's FXC.




























Sajassi et al.          Expires August 26, 2018                [Page 11]


INTERNET DRAFT          EVPN VPWS Flex Xconnect        February 26, 2018


                   N.VID 1,2,3 +---------------------+
                           PE1 |                     |
                       +---------+     IP/MPLS       |
      +-----+ VID1  p1 | +-----+ |                   +
      | CE1 |------------| FXC | |     sv.T1       PE3          +-----+
      |     |       /\ | |     |=======+     +----------+    +--| CE3 |
      +-----+\     +||---|     | |     \     |          |  1/   |     |
          VID3\   / ||---|     | |      \    | +-----+  |  /    +-----+
               \ / /\/ | +-----+ |       +=====| FXC |----+
                \ / p2 +---------+           | |     |  |   2   +-----+
                /\                           | |     |----------| CE4 |
               / /\    +---------+      +======|     |  |       |     |
              / /  \p3 | +-----+ |     /     | |     |  |       +-----+
       VIDs1,2 /    +----| FXC |      /      | |     |---+
      +-----+ /   /\   | |     |======+      | +-----+  |\3    +-----+
      | CE2 |-----||-----|     | |     sv.T2 |          | \    | CE5 |
      |     |-----||-----|     | |           +----------+  +---|     |
      +-----+     \/   | +-----+ |                 |           +-----+
         VIDs3,4  p4   +---------+                 |
                            PE2 |                  |
                    N.VID 1,2,3 +------------------+



                  Figure 1 VLAN-Signaled Flexible Xconnect


   The second scenario is a default Flexible Xconnect with Multi- Homing
   solution and it is depicted in Figure 2. In this case, the same VID
   Normalization as in the previous example is performed, however there
   is not an individual AD per-EVI route per normalized VID, but per
   bundle of ACs on an ES. That is, PE1 will advertise two AD per-EVI
   routes: the first one will identify the ACs on p1's ES and the second
   one will identify the AC2 in p2's ES. Similarly, PE2 will advertise
   two AD per-EVI routes.
















Sajassi et al.          Expires August 26, 2018                [Page 12]


INTERNET DRAFT          EVPN VPWS Flex Xconnect        February 26, 2018


                    N.VID 1,2,3 +---------------------+
                            PE1 |                     |
                        +---------+     IP/MPLS       |
      +-----+ VID1   p1 | +-----+ | sv.T1             +
      | CE1 |-------------| FXC |======+            PE3         +-----+
      |     |        /\ | |     | |    \     +----------+    +--| CE3 |
      +-----+\      +||---|     | sv.T2 \    |          |  1/   |     |
          VID3\    / ||---|     |=====+  \   | +-----+  |  /    +-----+
               \  // \/ | +-----+ |    \  +====| FXC |----+
                \ /  p2 +---------+     +======|     |  |   2   +-----+
                /\                           | |     |----------| CE4 |
               / /\    +---------+       +=====|     |  |       |     |
              / /  \p3 | +-----+ sv.T3  / +====|     |  |       +-----+
       VIDs1,2 /    +----| FXC |=======+ /   | |     |---+
      +-----+ /   /\   | |     | |      /    | +-----+  |\3    +-----+
      | CE2 |-----||---| |     | sv.T4 /     |          | \    | CE5 |
      |     |-----||---| |     |======+      +----------+  +---|     |
      +--VIDs3,4  \/   | +-----+ |                  |          +-----+
                  p4   +---------+                  |
                            PE2 |                   |
                    N.VID 1,2,3 +-------------------+

                  Figure 2 Default Flexible Xconnect



6.1 EVPN VPWS service Failure

   The failure detection of an EVPN VPWS service can be performed via
   OAM mechanisms such as VCCV-BFD and upon such failure detection, the
   switch over procedure to the backup S-PE is the same as the one
   described above.


6.2 Attachment Circuit Failure

   In case of AC Failure, the VLAN-Signaled and default FXC modes behave
   in a different way:

   o VLAN-signaled FXC (Figure 1): a VLAN or AC failure, e.g. VID1 on
   CE2, triggers the withdrawal of the AD per-EVI route for the
   corresponding Normalized VID, that is, Ethernet-Tag 2. When PE3
   receives the route withdrawal, it will remove PE1 from its path- list
   for traffic coming from CE4.

   o Default FXC (Figure 2): a VLAN or AC failure is not signaled in the
   default mode, therefore in case of an AC failure, e.g. VID1 on CE2,
   nothing prevents PE3 from sending CE4's traffic to PE1, creating a



Sajassi et al.          Expires August 26, 2018                [Page 13]


INTERNET DRAFT          EVPN VPWS Flex Xconnect        February 26, 2018


   black-hole. Application layer OAM may be used if per-VLAN fault
   propagation is required in this case.


6.3 PE Port Failure

   In case of PE port Failure, the failure will be signaled and the
   other PE will take over in both cases:


   o VLAN-signaled FXC (Figure 1): a port failure, e.g. p2, triggers the
   withdrawal of the AD per-EVI routes for Normalized VIDs 2 and 3, as
   well as the withdrawal of the AD per-ES route for p2's ES. Upon
   receiving the fault notification, PE3 will withdraw PE1 from its
   path-list for the traffic coming from CE4 and CE5.

   o Default FXC (Figure 2): a port failure, e.g. p2, is signaled by
   route for sv.T2 will also be withdrawn. Upon receiving the fault
   notification, PE3 will remove PE1 from its path-list for traffic
   coming from CE4 and CE5.

6.4 PE Node Failure

   In the case of PE node failure, the operation is similar to the steps
   described above, albeit that EVPN route withdrawals are performed by
   the Route Reflector instead of the PE.


7  Security Considerations

   There are no additional security considerations beyond what is
   already specified in [RFC8214].


8  IANA Considerations

   TBD.


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.

   [RFC7432]  Sajassi et al., "Ethernet VPN", RFC 7432, February 2015.




Sajassi et al.          Expires August 26, 2018                [Page 14]


INTERNET DRAFT          EVPN VPWS Flex Xconnect        February 26, 2018


   [RFC8214]  Boutros et al., "Virtual Private Wire Service Support in
              Ethernet VPN", RFC 8214, August 2015.




9.2  Informative References

   [BGP-PIC] Bashandy A. et al., "BGP Prefix Independent Convergence",
              draft-rtgwg-bgp-pic-02.txt, work in progress, October
              2013.

   [EVPN-Overlay] Sajassi et al., "A Network Virtualization Overlay
              Solution using EVPN", draft-ietf-bess-evpn-overlay-12,
              work in progress, February 2018.



Authors' Addresses


   A. Sajassi
   Cisco
   EMail: sajassi@cisco.com



   P. Brissette
   Cisco
   EMail: pbrisset@cisco.com



   J. Uttaro
   ATT
   EMail: ju1738@att.com



   J. Drake
   Juniper
   EMail: jdrake@juniper.net



   S. Boutros
   ATT
   EMail: boutros.sami@gmail.com



Sajassi et al.          Expires August 26, 2018                [Page 15]


INTERNET DRAFT          EVPN VPWS Flex Xconnect        February 26, 2018


   W. Lin
   Juniper
   EMail: wlin@juniper.net



   J. Rabadan
   jorge.rabadan@nokia.com











































Sajassi et al.          Expires August 26, 2018                [Page 16]


Html markup produced by rfcmarkup 1.126, available from https://tools.ietf.org/tools/rfcmarkup/