[RTG-DIR] Routing Directorate Review for draft-ietf-bess-evpn-vpws-10

["Acee Lindem (acee)" <[e-mail]>]

Hello,

I have been selected as the Routing Directorate reviewer for this draft.
The Routing Directorate seeks to review all routing or routing-related
drafts as they pass through IETF last call and IESG review, and sometimes
on special request. The purpose of the review is to provide assistance to
the Routing ADs. For more information about the Routing Directorate,
please see ​http://trac.tools.ietf.org/area/rtg/trac/wiki/RtgDir

Although these comments are primarily for the use of the Routing ADs, it
would be helpful if you could consider them along with any other IETF Last
Call comments that you receive, and strive to resolve them through
discussion or by updating the draft.

Document: draft-ietf-bess-evpn-vpws-10.txt

Reviewer: Acee Lindem
Review Date: 3/3/2017
IETF LC End Date: 3/10/2017
Intended Status: Standards Track

Summary:

    I have some minor concerns about this document that I think should be
resolved before publication.

Comments:

    The document is technically correct and comprehensive as evidenced by
successful implementation by multiple vendors. However, the document could
be much more readable with fewer run-on sentenses and some editorial
corrections. Editorial corrections are suggested in the nits.

Major Issues:

    No major issues were found.

Minor Issues:

    1. There are many compound sentences that don't need to be.
       Please consider rewording these for readability. I have
       made suggestions in below. Hopefully, you’ll agree with most
       of these.
    2. Consistent capitalization of acronyms, e.g., VLAN, P2P, and
       VXLAN.
    3. Consistent hyphenization, e.g., "cross-connect". Use "Per-ES" and
       "Per-EVI" when describing AD routes.
    4. On page 6, why is the P and B clear error treated differently
       from the  P and set error?
    5. On Page 9, why isn't the last received B Flag set used as the
       Backup PE similar to the behavior for the Primary PE?
    6. On Page 9, it is truly unfortunate that the Inter-AS options
       for EVPN weren't explicitly discussed in RFC 7432.

Nits:

Here are some suggested edits to improve the consistency and
readability of the document.

*** draft-ietf-bess-evpn-vpws-10.txt.orig       2017-03-02
20:41:20.000000000 -0500
--- draft-ietf-bess-evpn-vpws-10.txt            2017-03-03
11:20:32.000000000 -0500
***************
*** 118,167 ****
  
     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 (EVPN-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 traditional way of
!    PW signaling for p2p Ethernet services, as described in section 4.
  
!    [RFC7432] has the ability to forward customer traffic to/from a given
     customer Attachment Circuit (AC), 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) and Ethernet
     Private Line (EPL) service, in which all traffic flows are between a
     single pair of ports, that in EVPN terminology would mean a single
     pair of Ethernet Segments ES(es). 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 Auto-discovery (A-D) routes is used; whereas, for more
     general VPWS as per [RFC4664], traffic forwarding capability of EVPN
!    based on the exchange of a group of Ethernet AD routes (one Ethernet
!    AD route per AC/ES) 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 EVPN instance (EVI) Ethernet A-D
     route can be used in forwarding user traffic to the destination AC.
  
     For both EPL and EVPL services, a specific VPWS service instance is
!    identified by a pair of per EVI Ethernet A-D routes which together
     identify the VPWS service instance endpoints and the VPWS service
     instance. In the control plane the VPWS service instance is
     identified using the VPWS service instance identifiers advertised by
!    each PE and in the data plane the value of the MPLS label advertised
     by one PE is used by the other PE to send traffic for that VPWS
     service instance. As with the Ethernet Tag in standard EVPN, the VPWS
     service instance identifier has uniqueness within an EVPN instance.
  
!    Unlike EVPN where Ethernet Tag ID in EVPN routes are set to zero for
!    Port-based, vlan-based, and vlan-bundle interface mode and it is set
!    to non-zero Ethernet tag ID for vlan-aware bundle mode, in EVPN-VPWS,
!    for all the four interface modes, Ethernet tag ID in the Ethernet A-D
!    route MUST be set to a non-zero value in all the service interface
     types.
  
     In terms of route advertisement and MPLS label lookup behavior, EVPN-
!    VPWS resembles the vlan-aware bundle mode of [RFC7432] such that when
   
  
  
--- 118,167 ----
  
     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 (EVPN-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 the traditional way
of
!    PW signaling for P2P Ethernet services, as described in section 4.
  
!    [RFC7432] provides the ability to forward customer traffic to/from a
given
     customer Attachment Circuit (AC), without any MAC lookup. This
!    capability is ideal in providing P2P services (aka, VPWS services).
!    [MEF] defines Ethernet Virtual Private Line (EVPL) service as a P2P
!    service between a pair of ACs (designated by VLANs) as an Ethernet
     Private Line (EPL) service, in which all traffic flows are between a
     single pair of ports, that in EVPN terminology would mean a single
     pair of Ethernet Segments ES(es). EVPL can be considered as a VPWS
     with only two ACs. In delivering an EVPL service, the traffic
!    forwarding capability of EVPN is based on the exchange of a pair of
!    Ethernet Auto-discovery (A-D) routes; whereas, for more
     general VPWS as per [RFC4664], traffic forwarding capability of EVPN
!    is based on the exchange of a group of Ethernet AD routes (one
Ethernet
!    AD route per AC/ES). 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 EVPN instance (EVI) Ethernet A-D
     route can be used in forwarding user traffic to the destination AC.
  
     For both EPL and EVPL services, a specific VPWS service instance is
!    identified by a pair of per-EVI Ethernet A-D routes which together
     identify the VPWS service instance endpoints and the VPWS service
     instance. In the control plane the VPWS service instance is
     identified using the VPWS service instance identifiers advertised by
!    each PE. In the data plane the value of the MPLS label advertised
     by one PE is used by the other PE to send traffic for that VPWS
     service instance. As with the Ethernet Tag in standard EVPN, the VPWS
     service instance identifier has uniqueness within an EVPN instance.
  
!    For EVPN routes, the Ethernet Tag IDs are set to zero for
!    Port-based, VLAN-based, and VLAN-bundle interface mode and it is set
!    to a non-zero Ethernet Tag ID for VLAN-aware bundle mode. Conversely,
!    for EVPN-VPWS, the Ethernet Tag ID in the Ethernet A-D
!    route MUST be set to a non-zero value in all four service interface
     types.
  
     In terms of route advertisement and MPLS label lookup behavior, EVPN-
!    VPWS resembles the VLAN-aware bundle mode of [RFC7432] such that when
   
  
  
***************
*** 170,199 ****
  INTERNET DRAFT            VPWS support in EVPN         February 28, 2017
  
  
!    a PE advertises per EVI Ethernet A-D route, the VPWS service instance
!    serves as a 32-bit normalized Ethernet tag ID. The value of the MPLS
     label in this route represents both the EVI and the VPWS service
     instance, so that upon receiving an MPLS encapsulated packet, the
!    disposition PE can identify the egress AC from the lookup of the MPLS
!    label alone and perform any required tag translation. For EVPL
     service, the Ethernet frames transported over an MPLS/IP network
!    SHOULD remain tagged with the originating Vlan-ID (VID) and any VID
     translation MUST be performed at the disposition PE. For EPL service,
     the Ethernet frames are transported as is and the tags are not
     altered.
  
     The MPLS label value in the Ethernet A-D route can be set to the
!    VXLAN Network Identifier (VNI) for VxLAN encap, and this VNI may have
     a global scope or local scope per PE and may also be made equal to
     the VPWS service instance identifier set in the Ethernet A-D route.
  
!    The Ethernet Segment identifier encoded in the Ethernet A-D per EVI
!    route is not used to identify the service, however it can be used for
     flow-based load-balancing and mass withdraw functions as per
!    [RFC7432] baseline.
  
!    As with standard EVPN, the Ethernet A-D per ES route is used for fast
!    convergence upon link or node failure and the Ethernet Segment route
     is used for auto-discovery of the PEs attached to a given multi-homed
     CE and to synchronize state between them.
  
--- 170,199 ----
  INTERNET DRAFT            VPWS support in EVPN         February 28, 2017
  
  
!    a PE advertises a per-EVI Ethernet A-D route, the VPWS service
instance
!    serves as a 32-bit normalized Ethernet Tag ID. The value of the MPLS
     label in this route represents both the EVI and the VPWS service
     instance, so that upon receiving an MPLS encapsulated packet, the
!    disposition PE can identify the egress AC from the MPLS
!    label and subsequently perform any required tag translation. For EVPL
     service, the Ethernet frames transported over an MPLS/IP network
!    SHOULD remain tagged with the originating VLAN-ID (VID) and any VID
     translation MUST be performed at the disposition PE. For EPL service,
     the Ethernet frames are transported as is and the tags are not
     altered.
  
     The MPLS label value in the Ethernet A-D route can be set to the
!    VXLAN Network Identifier (VNI) for VXLAN encap, and this VNI may have
     a global scope or local scope per PE and may also be made equal to
     the VPWS service instance identifier set in the Ethernet A-D route.
  
!    The Ethernet Segment identifier encoded in the Ethernet A-D per-EVI
!    route is not used to identify the service. However, it can be used for
     flow-based load-balancing and mass withdraw functions as per
!    the [RFC7432] baseline.
  
!    As with standard EVPN, the Ethernet A-D per-ES route is used for fast
!    convergence upon link or node failure. The Ethernet Segment route
     is used for auto-discovery of the PEs attached to a given multi-homed
     CE and to synchronize state between them.
  
***************
*** 271,279 ****
     to only a single VLAN on a specific interface.  Therefore, there is a
     one-to-one mapping between a VID on this interface and the VPWS
     service instance identifier. The PE provides the cross-connect
!    functionality between MPLS LSP identified by the VPWS service
     instance identifier and a specific <port,VLAN>. If the VLAN is
!    represented by different VIDs on different PEs and different ES(es)
   
  
  
--- 271,279 ----
     to only a single VLAN on a specific interface.  Therefore, there is a
     one-to-one mapping between a VID on this interface and the VPWS
     service instance identifier. The PE provides the cross-connect
!    functionality between an MPLS LSP identified by the VPWS service
     instance identifier and a specific <port,VLAN>. If the VLAN is
!    represented by different VIDs on different PEs and different ES(es),
   
  
  
***************
*** 293,304 ****
  
     With this service interface, a VPWS service instance identifier
     corresponds to multiple VLANs on a specific interface. The PE
!    provides the cross-connect functionality between MPLS label
     identified by the VPWS service instance identifier and a group of
     VLANs on a specific interface. For this service interface, each VLAN
     is presented by a single VID which means no VLAN translation is
     allowed. The receiving PE, can direct the traffic based on EVPN label
!    alone to a specific port. The transmitting PE can cross connect
     traffic from a group of VLANs on a specific port to the MPLS label.
     The MPLS-encapsulated frames MUST remain tagged with the originating
     VID.   
--- 293,304 ----
  
     With this service interface, a VPWS service instance identifier
     corresponds to multiple VLANs on a specific interface. The PE
!    provides the cross-connect functionality between the MPLS label
     identified by the VPWS service instance identifier and a group of
     VLANs on a specific interface. For this service interface, each VLAN
     is presented by a single VID which means no VLAN translation is
     allowed. The receiving PE, can direct the traffic based on EVPN label
!    alone to a specific port. The transmitting PE can cross-connect
     traffic from a group of VLANs on a specific port to the MPLS label.
     The MPLS-encapsulated frames MUST remain tagged with the originating
     VID.   
***************
*** 316,335 ****
     based service interface (defined in section 2.1) and thus this
     service interface is not used in EVPN-VPWS.  In other words, if one
     tries to define data-plane and control plane behavior for this
!    service interface, he would realize that it is the same as that of
     VLAN-based service.
  
  3. BGP Extensions
  
  
!    This document specifies the use of the per EVI Ethernet A-D route to
     signal VPWS services. The Ethernet Segment Identifier field is set to
     the customer ES and the Ethernet Tag ID 32-bit field MUST be set to
!    the VPWS service instance identifier value, the VPWS service instance
     identifier value MAY be set to a 24-bit value, when 24-bit value is
!    used, it MUST be right aligned. For both EPL and EVPL services, for a
!    given VPWS service instance the pair of PEs instantiating that VPWS
!    service instance will each advertise a per EVI Ethernet A-D route
   
  
  
--- 316,335 ----
     based service interface (defined in section 2.1) and thus this
     service interface is not used in EVPN-VPWS.  In other words, if one
     tries to define data-plane and control plane behavior for this
!    service interface, one would realize that it is the same as that of
     VLAN-based service.
  
  3. BGP Extensions
  
  
!    This document specifies the use of the per-EVI Ethernet A-D route to
     signal VPWS services. The Ethernet Segment Identifier field is set to
     the customer ES and the Ethernet Tag ID 32-bit field MUST be set to
!    the VPWS service instance identifier value. The VPWS service instance
     identifier value MAY be set to a 24-bit value, when 24-bit value is
!    used, it MUST be right aligned. For both EPL and EVPL services using
!    a given VPWS service instance, the pair of PEs instantiating that VPWS
!    service instance will each advertise a per-EVI Ethernet A-D route
   
  
  
***************
*** 340,350 ****
  
     with its VPWS service instance identifier and will each be configured
     with the other PE's VPWS service instance identifier. When each PE
!    has received the other PE's per EVI Ethernet A-D route the VPWS
     service instance is instantiated. It should be noted that the same
     VPWS service instance identifier may be configured on both PEs.
  
!    The Route-Target (RT) extended community with which the per EVI
     Ethernet A-D route is tagged identifies the EVPN instance in which
     the VPWS service instance is configured. It is the operator's choice
     as to how many and which VPWS service instances are configured in a
--- 340,350 ----
  
     with its VPWS service instance identifier and will each be configured
     with the other PE's VPWS service instance identifier. When each PE
!    has received the other PE's per-EVI Ethernet A-D route, the VPWS
     service instance is instantiated. It should be noted that the same
     VPWS service instance identifier may be configured on both PEs.
  
!    The Route-Target (RT) extended community with which the per-EVI
     Ethernet A-D route is tagged identifies the EVPN instance in which
     the VPWS service instance is configured. It is the operator's choice
     as to how many and which VPWS service instances are configured in a
***************
*** 355,361 ****
  3.1 EVPN Layer 2 attributes extended community
  
     This draft proposes a new extended community [RFC4360], to be
!    included with the per EVI Ethernet A-D route. This attribute is
     mandatory if multihoming is enabled.
  
          +------------------------------------+
--- 355,361 ----
  3.1 EVPN Layer 2 attributes extended community
  
     This draft proposes a new extended community [RFC4360], to be
!    included with the per-EVI Ethernet A-D route. This attribute is
     mandatory if multihoming is enabled.
  
          +------------------------------------+
***************
*** 404,447 ****
  
  
     L2 MTU (Maximum Transmission Unit) is a 2-octet value indicating the
!    MTU in bytes.
  
!    A received L2 MTU=0 means no MTU checking against local MTU is
     needed. A received non-zero MTU MUST be checked against local MTU and
     if there is a mismatch, the local PE MUST NOT add the remote PE as
     the EVPN destination for the corresponding VPWS service instance.
  
     The usage of the Per ES Ethernet A-D route is unchanged from its
!    usage in [RFC7432], i.e. the "Single-Active" bit in the flags of the
     ESI Label extended community will indicate if single-active or all-
     active redundancy is used for this ES.
  
     In multihoming scenarios, both B and P flags MUST NOT be both set. A
     PE that receives an update with both B and P flags set MUST treat the
     route as a withdrawal. If the PE receives a route with both B and P
!    unset, it MUST discard the received route from the sender PE.
  
     In a multihoming all-active scenario, there is no DF election, and
     all the PEs in the ES that are active and ready to forward traffic
!    to/from the CE will set the P Flag to 1. A remote PE will do per-flow
!    load balancing to the PEs that send P=1 for the same Ethernet Tag and
!    ESI. B Flag in control flags SHOULD NOT be set in the multihoming
     all-active scenario and MUST be ignored by receiving PE(s) if set.
  
!    In multihoming single-active scenario, for a given VPWS service
!    instance, in steady state, as result of DF election, the Primary
!    elected PE for the VPWS service instance should signal P=1,B=0, the
!    Backup elected PE should signal P=0,B=1, and the rest of the PEs in
!    the same ES should signal P=0,B=0. When the primary PE/ES fails, the
     primary PE will withdraw the associated Ethernet A-D routes for the
!    VPWS service instance from the remote PE, the remote PEs should then
     send traffic associated with the VPWS instance to the backup PE. DF
     re-election will happen between the PE(s) in the same ES, and there
!    will be a new elected primary PE and new elected backup PE that will
!    signal the P and B Flags as described. A remote PE SHOULD receive P=1
!    from only one Primary PE and a B=1 from only one Backup PE. However
!    during transient situations, a remote PE receiving P=1 from more than
!    one PE will select the last advertising PE as the primary PE when
   
  
  
--- 404,448 ----
  
  
     L2 MTU (Maximum Transmission Unit) is a 2-octet value indicating the
!    MTU in octets.
  
!    A received L2 MTU of zero indicates no MTU checking against the local
MTU is
     needed. A received non-zero MTU MUST be checked against local MTU and
     if there is a mismatch, the local PE MUST NOT add the remote PE as
     the EVPN destination for the corresponding VPWS service instance.
  
     The usage of the Per ES Ethernet A-D route is unchanged from its
!    usage in [RFC7432], i.e., the "Single-Active" bit in the flags of the
     ESI Label extended community will indicate if single-active or all-
     active redundancy is used for this ES.
  
     In multihoming scenarios, both B and P flags MUST NOT be both set. A
     PE that receives an update with both B and P flags set MUST treat the
     route as a withdrawal. If the PE receives a route with both B and P
!    clear, it MUST discard the received route from the sender PE.
  
     In a multihoming all-active scenario, there is no DF election, and
     all the PEs in the ES that are active and ready to forward traffic
!    to/from the CE will set the P Flag. A remote PE will do per-flow
!    load balancing to the PEs that set the P Flag for the same Ethernet
Tag and
!    ESI. The B Flag in control flags SHOULD NOT be set in the multihoming
     all-active scenario and MUST be ignored by receiving PE(s) if set.
  
!    In multihoming single-active scenario for a given VPWS service
!    instance, the DF election should result in the Primary-elected PE
!    the VPWS service instance advertising the P Flag set and the B Flag
!    clear, the Backup-elected PE should advertise the P Flag clear and
!    the B Flag set, and the rest of the PEs in the same ES should signal
!    both the P and B flags clear. When the primary PE/ES fails, the
     primary PE will withdraw the associated Ethernet A-D routes for the
!    VPWS service instance from the remote PE and the remote PEs should
then
     send traffic associated with the VPWS instance to the backup PE. DF
     re-election will happen between the PE(s) in the same ES, and there
!    will be a newly elected primary PE and newly elected backup PE that
will
!    signal the P and B Flags as described. A remote PE SHOULD receive the
P
!    Flag set from only one Primary PE and the B Flag set from only one
Backup 
!    PE. However, during transient situations, a remote PE receiving a P
Flag 
!    set from more than one PE will select the last advertising PE as the
primary PE when
   
  
  
***************
*** 450,461 ****
  INTERNET DRAFT            VPWS support in EVPN         February 28, 2017
  
  
!    forwarding traffic. A remote PE receiving B=1 from more than one PE
!    will select only one backup PE. A remote PE MUST receive P=1 from at
     least one PE before forwarding traffic.
  
     If a network uses entropy labels per [RFC6790] then the C Flag MUST
!    NOT be set to 1 and control word MUST NOT be used when sending EVPN-
     encapsulated packets over a P2P LSP.
  
  
--- 451,462 ----
  INTERNET DRAFT            VPWS support in EVPN         February 28, 2017
  
  
!    forwarding traffic. A remote PE receiving a B Flag set from more than
one PE
!    will select only one backup PE. A remote PE MUST receive P Flag set
from at
     least one PE before forwarding traffic.
  
     If a network uses entropy labels per [RFC6790] then the C Flag MUST
!    NOT be set and the control word MUST NOT be used when sending EVPN-
     encapsulated packets over a P2P LSP.
  
  
***************
*** 488,494 ****
     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 per EVI
     Ethernet A-D routes, one route per VPWS service instance.  For inter-
     AS option B, the ASBRs re-advertise these routes with NEXT_HOP
     attribute set to their IP addresses as per [RFC4271]. The link
--- 489,495 ----
     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 per-EVI
     Ethernet A-D routes, one route per VPWS service instance.  For inter-
     AS option B, the ASBRs re-advertise these routes with NEXT_HOP
     attribute set to their IP addresses as per [RFC4271]. The link
***************
*** 510,520 ****
     label will identify the VPWS service instance and if translation is
     needed, it should be done by the Ethernet interface for each service.
  
!    For single-homed CE, in an advertised per EVI Ethernet A-D route the
     ESI field is set to 0 and the Ethernet Tag ID is set to the VPWS
     service instance identifier that identifies the EVPL or EPL service.
  
!    For a multi-homed CE, in an advertised per EVI Ethernet A-D route the
     ESI field is set to the CE's ESI and the Ethernet Tag ID is set to
     the VPWS service instance identifier, which MUST have the same value
     on all PEs attached to that ES. This allows an ingress PE in a
--- 511,521 ----
     label will identify the VPWS service instance and if translation is
     needed, it should be done by the Ethernet interface for each service.
  
!    For single-homed CE, in an advertised per-EVI Ethernet A-D route the
     ESI field is set to 0 and the Ethernet Tag ID is set to the VPWS
     service instance identifier that identifies the EVPL or EPL service.
  
!    For a multi-homed CE, in an advertised per-EVI Ethernet A-D route the
     ESI field is set to the CE's ESI and the Ethernet Tag ID is set to
     the VPWS service instance identifier, which MUST have the same value
     on all PEs attached to that ES. This allows an ingress PE in a
***************
*** 523,535 ****
     traffic follows the transport paths, which may be asymmetric.
  
     The VPWS service instance identifier encoded in the Ethernet Tag ID
!    in an advertised per EVI Ethernet A-D route MUST either be unique
     across all ASs, or an ASBR needs to perform a translation when the
!    per EVI Ethernet A-D route is re-advertised by the ASBR from one AS
     to the other AS.
  
!    Per ES Ethernet A-D route can be used for mass withdraw to withdraw
!    all per EVI Ethernet A-D routes associated with the multi-home site
     on a given PE.
  
  
--- 524,536 ----
     traffic follows the transport paths, which may be asymmetric.
  
     The VPWS service instance identifier encoded in the Ethernet Tag ID
!    advertised in a per-EVI Ethernet A-D route MUST either be unique
     across all ASs, or an ASBR needs to perform a translation when the
!    per-EVI Ethernet A-D route is re-advertised by the ASBR from one AS
     to the other AS.
  
!    A per-ES Ethernet A-D route can be used for mass withdraw to withdraw
!    all per-EVI Ethernet A-D routes associated with the multi-homed site
     on a given PE.
  
  
***************
*** 540,551 ****
     signaling is done via LDP and service endpoint discovery is either
     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
     supported.
  
!    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.
  
--- 541,552 ----
     signaling is done via LDP and service endpoint discovery is either
     through manual provisioning or through BGP.
  
!    In existing implementations 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
     supported.
  
!    In existing implementations 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.
  
***************
*** 566,572 ****
  
     Finally, EVPN may employ data plane egress link protection mechanisms
     not available in VPWS. This can be done by the primary PE (on local
!    AC down) using the label advertised in the per EVI Ethernet A-D route
     by the backup PE to encapsulate the traffic and direct it to backup
     PE.
  
--- 567,573 ----
  
     Finally, EVPN may employ data plane egress link protection mechanisms
     not available in VPWS. This can be done by the primary PE (on local
!    AC down) using the label advertised in the per-EVI Ethernet A-D route
     by the backup PE to encapsulate the traffic and direct it to backup
     PE.
  
***************
*** 582,594 ****
     Unlike [RFC7432],  EVPN-VPWS uses Ethernet A-D route advertisements
     for single-homed Ethernet Segments. Therefore, upon a link/port
     failure of this single-homed Ethernet Segment, the PE MUST withdraw
!    the associated per EVI Ethernet A-D routes.
  
  6.2 Multi-Homed CEs
  
     For a faster convergence in multi-homed scenarios with either Single-
!    Active Redundancy or All-active redundancy, mass withdraw technique
!    is used. A PE previously advertising a per ES Ethernet A-D route, can
     withdraw this route signaling to the remote PEs to switch all the
     VPWS service instances associated with this multi-homed ES to the
     backup PE
--- 583,595 ----
     Unlike [RFC7432],  EVPN-VPWS uses Ethernet A-D route advertisements
     for single-homed Ethernet Segments. Therefore, upon a link/port
     failure of this single-homed Ethernet Segment, the PE MUST withdraw
!    the associated per-EVI Ethernet A-D routes.
  
  6.2 Multi-Homed CEs
  
     For a faster convergence in multi-homed scenarios with either Single-
!    Active Redundancy or All-active redundancy, a mass withdraw technique
!    is used. A PE previously advertising a per-ES Ethernet A-D route, can
     withdraw this route signaling to the remote PEs to switch all the
     VPWS service instances associated with this multi-homed ES to the
     backup PE
***************
*** 630,636 ****
  
       P      Advertising PE is the Primary PE.
       B      Advertising PE is the Backup PE.
!      C      Control word [RFC4448] MUST be present
  
  10 References
  
--- 631,637 ----
  
       P      Advertising PE is the Primary PE.
       B      Advertising PE is the Backup PE.
!      C      Control word [RFC4448] MUST be present.
  
  10 References


Thanks,
Acee