draft-ietf-bess-evpn-vpws-10.txt   draft-ietf-bess-evpn-vpws-11.txt 
skipping to change at page 1, line 13 skipping to change at page 1, line 13
INTERNET-DRAFT Sami Boutros INTERNET-DRAFT Sami Boutros
Intended Status: Standard Track VMware Intended Status: Standard Track VMware
Ali Sajassi Ali Sajassi
Samer Salam Samer Salam
Cisco Systems Cisco Systems
John Drake John Drake
Juniper Networks Juniper Networks
J. Rabadan J. Rabadan
Nokia Nokia
Expires: September 1, 2017 February 28, 2017 Expires: September 13, 2017 March 12, 2017
VPWS support in EVPN VPWS support in EVPN
draft-ietf-bess-evpn-vpws-10.txt draft-ietf-bess-evpn-vpws-11.txt
Abstract Abstract
This document describes how EVPN can be used to support Virtual This document describes how EVPN can be used to support Virtual
Private Wire Service (VPWS) in MPLS/IP networks. EVPN enables the Private Wire Service (VPWS) in MPLS/IP networks. EVPN enables the
following characteristics for VPWS: single-active as well as all- following characteristics for VPWS: single-active as well as all-
active multi-homing with flow-based load-balancing, eliminates the active multi-homing with flow-based load-balancing, eliminates the
need for traditional way of PW signaling, and provides fast need for traditional way of Pseudowire (PW) signaling, and provides
protection convergence upon node or link failure. fast protection convergence upon node or link failure.
Status of this Memo Status of this Memo
This Internet-Draft is submitted to IETF in full conformance with the This Internet-Draft is submitted to IETF in full conformance with the
provisions of BCP 78 and BCP 79. provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF), its areas, and its working groups. Note that Task Force (IETF), its areas, and its working groups. Note that
other groups may also distribute working documents as other groups may also distribute working documents as
Internet-Drafts. Internet-Drafts.
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2.3 VLAN-Aware Bundle Service Interface . . . . . . . . . . . . 6 2.3 VLAN-Aware Bundle Service Interface . . . . . . . . . . . . 6
3. BGP Extensions . . . . . . . . . . . . . . . . . . . . . . . . 6 3. BGP Extensions . . . . . . . . . . . . . . . . . . . . . . . . 6
3.1 EVPN Layer 2 attributes extended community . . . . . . . . . 7 3.1 EVPN Layer 2 attributes extended community . . . . . . . . . 7
4 Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 4 Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
5 EVPN Comparison to PW Signaling . . . . . . . . . . . . . . . . 10 5 EVPN Comparison to PW Signaling . . . . . . . . . . . . . . . . 10
6 Failure Scenarios . . . . . . . . . . . . . . . . . . . . . . . 11 6 Failure Scenarios . . . . . . . . . . . . . . . . . . . . . . . 11
6.1 Single-Homed CEs . . . . . . . . . . . . . . . . . . . . . . 11 6.1 Single-Homed CEs . . . . . . . . . . . . . . . . . . . . . . 11
6.2 Multi-Homed CEs . . . . . . . . . . . . . . . . . . . . . . 11 6.2 Multi-Homed CEs . . . . . . . . . . . . . . . . . . . . . . 11
7 Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . . 11 7 Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . . 11
8 Security Considerations . . . . . . . . . . . . . . . . . . . . 11 8 Security Considerations . . . . . . . . . . . . . . . . . . . . 11
9 IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 11 9 IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 12
10 References . . . . . . . . . . . . . . . . . . . . . . . . . . 12 10 References . . . . . . . . . . . . . . . . . . . . . . . . . . 12
10.1 Normative References . . . . . . . . . . . . . . . . . . . 12 10.1 Normative References . . . . . . . . . . . . . . . . . . . 12
10.2 Informative References . . . . . . . . . . . . . . . . . . 12 10.2 Informative References . . . . . . . . . . . . . . . . . . 13
Contributors . . . . . . . . . . . . . . . . . . . . . . . . . . . 13 Contributors . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 13 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 13
1 Introduction 1 Introduction
This document describes how EVPN can be used to support Virtual This document describes how EVPN can be used to support Virtual
Private Wire Service (VPWS) in MPLS/IP networks. The use of EVPN Private Wire Service (VPWS) in MPLS/IP networks. The use of EVPN
mechanisms for VPWS (EVPN-VPWS) brings the benefits of EVPN to p2p mechanisms for VPWS (EVPN-VPWS) brings the benefits of EVPN to P2P
services. These benefits include single-active redundancy as well as services. These benefits include single-active redundancy as well as
all-active redundancy with flow-based load-balancing. Furthermore, all-active redundancy with flow-based load-balancing. Furthermore,
the use of EVPN for VPWS eliminates the need for traditional way of the use of EVPN for VPWS eliminates the need for traditional way of
PW signaling for p2p Ethernet services, as described in section 4. PW signaling for P2P Ethernet services, as described in section 4.
[RFC7432] has the ability to forward customer traffic to/from a given [RFC7432] provides the ability to forward customer traffic to/from a
customer Attachment Circuit (AC), without any MAC lookup. This given customer Attachment Circuit (AC), without any MAC lookup. This
capability is ideal in providing p2p services (aka VPWS services). capability is ideal in providing P2P services (aka VPWS services).
[MEF] defines Ethernet Virtual Private Line (EVPL) service as p2p [MEF] defines Ethernet Virtual Private Line (EVPL) service as P2P
service between a pair of ACs (designated by VLANs) and Ethernet service between a pair of ACs (designated by VLANs) and Ethernet
Private Line (EPL) service, in which all traffic flows are between a Private Line (EPL) service, in which all traffic flows are between a
single pair of ports, that in EVPN terminology would mean a single 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 pair of Ethernet Segments ES(es). EVPL can be considered as a VPWS
with only two ACs. In delivering an EVPL service, the traffic with only two ACs. In delivering an EVPL service, the traffic
forwarding capability of EVPN based on the exchange of a pair of forwarding capability of EVPN is based on the exchange of a pair of
Ethernet Auto-discovery (A-D) routes is used; whereas, for more Ethernet Auto-discovery (A-D) routes; whereas, for more general VPWS
general VPWS as per [RFC4664], traffic forwarding capability of EVPN as per [RFC4664], traffic forwarding capability of EVPN is based on
based on the exchange of a group of Ethernet AD routes (one Ethernet the exchange of a group of Ethernet AD routes (one Ethernet AD route
AD route per AC/ES) is used. In a VPWS service, the traffic from an per AC/ES). In a VPWS service, the traffic from an originating
originating Ethernet Segment can be forwarded only to a single Ethernet Segment can be forwarded only to a single destination
destination Ethernet Segment; hence, no MAC lookup is needed and the Ethernet Segment; hence, no MAC lookup is needed and the MPLS label
MPLS label associated with the per EVPN instance (EVI) Ethernet A-D associated with the per EVPN instance (EVI) Ethernet A-D route can be
route can be used in forwarding user traffic to the destination AC. used in forwarding user traffic to the destination AC.
For both EPL and EVPL services, a specific VPWS service instance is 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 identified by a pair of per-EVI Ethernet A-D routes which together
identify the VPWS service instance endpoints and the VPWS service identify the VPWS service instance endpoints and the VPWS service
instance. In the control plane the VPWS service instance is instance. In the control plane the VPWS service instance is
identified using the VPWS service instance identifiers advertised by identified using the VPWS service instance identifiers advertised by
each PE and in the data plane the value of the MPLS label advertised each PE. In the data plane the value of the MPLS label advertised by
by one PE is used by the other PE to send traffic for that VPWS one PE is used by the other PE to send traffic for that VPWS service
service instance. As with the Ethernet Tag in standard EVPN, the VPWS instance. As with the Ethernet Tag in standard EVPN, the VPWS service
service instance identifier has uniqueness within an EVPN instance. instance identifier has uniqueness within an EVPN instance.
Unlike EVPN where Ethernet Tag ID in EVPN routes are set to zero for For EVPN routes, the Ethernet Tag IDs are set to zero for Port-based,
Port-based, vlan-based, and vlan-bundle interface mode and it is set VLAN-based, and VLAN-bundle interface mode and set to non-zero
to non-zero Ethernet tag ID for vlan-aware bundle mode, in EVPN-VPWS, Ethernet Tag IDs for VLAN-aware bundle mode. Conversely, for EVPN-
for all the four interface modes, Ethernet tag ID in the Ethernet A-D VPWS, the Ethernet Tag ID in the Ethernet A-D route MUST be set to a
route MUST be set to a non-zero value in all the service interface non-zero value for all four service interface types.
types.
In terms of route advertisement and MPLS label lookup behavior, EVPN- In terms of route advertisement and MPLS label lookup behavior, EVPN-
VPWS resembles the vlan-aware bundle mode of [RFC7432] such that when VPWS resembles the VLAN-aware bundle mode of [RFC7432] such that when
a PE advertises per EVI Ethernet A-D route, the VPWS service instance 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 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 label in this route represents both the EVI and the VPWS service
instance, so that upon receiving an MPLS encapsulated packet, the instance, so that upon receiving an MPLS encapsulated packet, the
disposition PE can identify the egress AC from the lookup of the MPLS disposition PE can identify the egress AC from the MPLS label and
label alone and perform any required tag translation. For EVPL subsequently perform any required tag translation. For EVPL service,
service, the Ethernet frames transported over an MPLS/IP network the Ethernet frames transported over an MPLS/IP network SHOULD remain
SHOULD remain tagged with the originating Vlan-ID (VID) and any VID tagged with the originating VLAN-ID (VID) and any VID translation
translation MUST be performed at the disposition PE. For EPL service, MUST be performed at the disposition PE. For EPL service, the
the Ethernet frames are transported as is and the tags are not Ethernet frames are transported as is and the tags are not altered.
altered.
The MPLS label value in the Ethernet A-D route can be set to the 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 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 a global scope or local scope per PE and may also be equal to the
the VPWS service instance identifier set in the Ethernet A-D route. VPWS service instance identifier set in the Ethernet A-D route.
The Ethernet Segment identifier encoded in the Ethernet A-D per EVI 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 route is not used to identify the service. However it can be used for
flow-based load-balancing and mass withdraw functions as per flow-based load-balancing and mass withdraw functions as per the
[RFC7432] baseline. [RFC7432] baseline.
As with standard EVPN, the Ethernet A-D per ES route is used for fast 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 convergence upon link or node failure. The Ethernet Segment route is
is used for auto-discovery of the PEs attached to a given multi-homed used for auto-discovery of the PEs attached to a given multi-homed CE
CE and to synchronize state between them. and to synchronize state between them.
1.1 Terminology 1.1 Terminology
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in RFC 2119 [RFC2119]. document are to be interpreted as described in RFC 2119 [RFC2119].
MAC: Media Access Control MAC: Media Access Control
MPLS: Multi Protocol Label Switching. MPLS: Multi Protocol Label Switching.
OAM: Operations, Administration and Maintenance. OAM: Operations, Administration and Maintenance.
PE: Provide Edge Node. PE: Provide Edge Node.
ASBR: Autonomous System Border Router
CE: Customer Edge device e.g., host or router or switch. CE: Customer Edge device e.g., host or router or switch.
EVPL: Ethernet Virtual Private Line. EVPL: Ethernet Virtual Private Line.
EPL: Ethernet Private Line. EPL: Ethernet Private Line.
EP-LAN: Ethernet Private LAN. EP-LAN: Ethernet Private LAN.
EVP-LAN: Ethernet Virtual Private LAN. EVP-LAN: Ethernet Virtual Private LAN.
S-VLAN: Service VLAN identifier. S-VLAN: Service VLAN identifier.
C-VLAN: Customer VLAN identifier. C-VLAN: Customer VLAN identifier.
VID: VLAN-ID.
VPWS: Virtual Private Wire Service. VPWS: Virtual Private Wire Service.
EVI: EVPN Instance. EVI: EVPN Instance.
ES: Ethernet Segment on a PE refers to the link attached to it, this ES: Ethernet Segment on a PE refers to the link attached to it, this
link can be part of a set of links attached to different PEs in multi link can be part of a set of links attached to different PEs in multi
homed cases, or could be a single link in single homed cases. homed cases, or could be a single link in single homed cases.
ESI: Ethernet Segment Identifier. ESI: Ethernet Segment Identifier.
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one VPWS service identifier. one VPWS service identifier.
2 Service interface 2 Service interface
2.1 VLAN-Based Service Interface 2.1 VLAN-Based Service Interface
With this service interface, a VPWS instance identifier corresponds With this service interface, a VPWS instance identifier corresponds
to only a single VLAN on a specific interface. Therefore, there is a 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 one-to-one mapping between a VID on this interface and the VPWS
service instance identifier. The PE provides the cross-connect service instance identifier. The PE provides the cross-connect
functionality between MPLS LSP identified by the VPWS service functionality between an MPLS LSP identified by the VPWS service
instance identifier and a specific <port,VLAN>. If the VLAN is instance identifier and a specific <port,VLAN>. If the VLAN is
represented by different VIDs on different PEs and different ES(es) represented by different VIDs on different PEs and different ES(es),
(e.g., a different VID per Ethernet segment per PE), then each PE (e.g., a different VID per Ethernet segment per PE), then each PE
needs to perform VID translation for frames destined to its Ethernet needs to perform VID translation for frames destined to its Ethernet
segment. In such scenarios, the Ethernet frames transported over an segment. In such scenarios, the Ethernet frames transported over an
MPLS/IP network SHOULD remain tagged with the originating VID, and a MPLS/IP network SHOULD remain tagged with the originating VID, and a
VID translation MUST be supported in the data path and MUST be VID translation MUST be supported in the data path and MUST be
performed on the disposition PE. performed on the disposition PE.
2.2 VLAN Bundle Service Interface 2.2 VLAN Bundle Service Interface
With this service interface, a VPWS service instance identifier With this service interface, a VPWS service instance identifier
corresponds to multiple VLANs on a specific interface. The PE corresponds to multiple VLANs on a specific interface. The PE
provides the cross-connect functionality between MPLS label provides the cross-connect functionality between the MPLS label
identified by the VPWS service instance identifier and a group of identified by the VPWS service instance identifier and a group of
VLANs on a specific interface. For this service interface, each VLAN VLANs on a specific interface. For this service interface, each VLAN
is presented by a single VID which means no VLAN translation is is presented by a single VID which means no VLAN translation is
allowed. The receiving PE, can direct the traffic based on EVPN label allowed. The receiving PE, can direct the traffic based on EVPN label
alone to a specific port. The transmitting PE can cross connect 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. traffic from a group of VLANs on a specific port to the MPLS label.
The MPLS-encapsulated frames MUST remain tagged with the originating The MPLS-encapsulated frames MUST remain tagged with the originating
VID. VID.
2.2.1 Port-Based Service Interface 2.2.1 Port-Based Service Interface
This service interface is a special case of the VLAN bundle service This service interface is a special case of the VLAN bundle service
interface, where all of the VLANs on the port are mapped to the same interface, where all of the VLANs on the port are mapped to the same
VPWS service instance identifier. The procedures are identical to VPWS service instance identifier. The procedures are identical to
those described in Section 2.2. those described in Section 2.2.
2.3 VLAN-Aware Bundle Service Interface 2.3 VLAN-Aware Bundle Service Interface
Contrary to EVPN, in EVPN-VPWS this service interface maps to VLAN- Contrary to EVPN, in EVPN-VPWS this service interface maps to a VLAN-
based service interface (defined in section 2.1) and thus this based service interface (defined in section 2.1) and thus this
service interface is not used in EVPN-VPWS. In other words, if one service interface is not used in EVPN-VPWS. In other words, if one
tries to define data-plane and control plane behavior for this tries to define data plane and control plane behavior for this
service interface, he would realize that it is the same as that of service interface, one would realize that it is the same as that of
VLAN-based service. VLAN-based service.
3. BGP Extensions 3. BGP Extensions
This document specifies the use of the per EVI Ethernet A-D route to 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 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 customer ES and the Ethernet Tag ID 32-bit field MUST be set to
the VPWS service instance identifier value, the VPWS service instance 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 identifier value MAY be set to a 24-bit value and when a 24-bit value
used, it MUST be right aligned. For both EPL and EVPL services, for a is used, it MUST be right aligned. For both EPL and EVPL services
given VPWS service instance the pair of PEs instantiating that VPWS using a given VPWS service instance, the pair of PEs instantiating
service instance will each advertise a per EVI Ethernet A-D route that VPWS service instance will each advertise a per-EVI Ethernet A-D
with its VPWS service instance identifier and will each be configured route with its VPWS service instance identifier and will each be
with the other PE's VPWS service instance identifier. When each PE configured with the other PE's VPWS service instance identifier. When
has received the other PE's per EVI Ethernet A-D route the VPWS each PE has received the other PE's per-EVI Ethernet A-D route, the
service instance is instantiated. It should be noted that the same VPWS service instance is instantiated. It should be noted that the
VPWS service instance identifier may be configured on both PEs. same VPWS service instance identifier may be configured on both PEs.
The Route-Target (RT) extended community with which the per EVI The Route-Target (RT) extended community with which the per-EVI
Ethernet A-D route is tagged identifies the EVPN instance in which Ethernet A-D route is tagged identifies the EVPN instance in which
the VPWS service instance is configured. It is the operator's choice 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 as to how many and which VPWS service instances are configured in a
given EVPN instance. However, a given EVPN instance MUST NOT be given EVPN instance. However, a given EVPN instance MUST NOT be
configured with both VPWS service instances and standard EVPN multi- configured with both VPWS service instances and standard EVPN multi-
point services. point services.
3.1 EVPN Layer 2 attributes extended community 3.1 EVPN Layer 2 attributes extended community
This draft proposes a new extended community [RFC4360], to be This draft defines a new extended community [RFC4360], to be included
included with the per EVI Ethernet A-D route. This attribute is with per-EVI Ethernet A-D routes. This attribute is mandatory if
mandatory if multihoming is enabled. multihoming is enabled.
+------------------------------------+ +------------------------------------+
| Type(0x06)/Sub-type(0x04)(2 octet)| | Type(0x06)/Sub-type(0x04)(2 octet)|
+------------------------------------+ +------------------------------------+
| Control Flags (2 octets) | | Control Flags (2 octets) |
+------------------------------------+ +------------------------------------+
| L2 MTU (2 octets) | | L2 MTU (2 octets) |
+------------------------------------+ +------------------------------------+
| Reserved (2 octets) | | Reserved (2 octets) |
+------------------------------------+ +------------------------------------+
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B If set to 1 in multihoming single-active scenarios, it B If set to 1 in multihoming single-active scenarios, it
indicates that the advertising PE is the Backup PE. indicates that the advertising PE is the Backup PE.
C If set to 1, a Control word [RFC4448] MUST be present C If set to 1, a Control word [RFC4448] MUST be present
when sending EVPN packets to this PE. when sending EVPN packets to this PE.
L2 MTU (Maximum Transmission Unit) is a 2-octet value indicating the L2 MTU (Maximum Transmission Unit) is a 2-octet value indicating the
MTU in bytes. MTU in bytes.
A received L2 MTU=0 means no MTU checking against local MTU is A received L2 MTU of zero means no MTU checking against local MTU is
needed. A received non-zero MTU MUST be checked against local MTU and 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 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 EVPN destination for the corresponding VPWS service instance.
The usage of the Per ES Ethernet A-D route is unchanged from its 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 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- ESI Label extended community will indicate if single-active or all-
active redundancy is used for this ES. active redundancy is used for this ES.
In multihoming scenarios, both B and P flags MUST NOT be both set. A 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 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 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. clear, it MUST treat the route as a withdrawal from the sender PE.
In a multihoming all-active scenario, there is no DF election, and 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 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 to/from the CE will set the P Flag. A remote PE will do per-flow
load balancing to the PEs that send P=1 for the same Ethernet Tag and load-balancing to the PEs that set the P Flag for the same Ethernet
ESI. B Flag in control flags SHOULD NOT be set in the multihoming Tag and ESI. The B Flag in control flags SHOULD NOT be set in the
all-active scenario and MUST be ignored by receiving PE(s) if set. multihoming all-active scenario and MUST be ignored by receiving
PE(s) if set.
In multihoming single-active scenario, for a given VPWS service In multihoming single-active scenario for a given VPWS service
instance, in steady state, as result of DF election, the Primary instance, the DF election should result in the Primary-elected PE for
elected PE for the VPWS service instance should signal P=1,B=0, the the VPWS service instance advertising the P Flag set and the B Flag
Backup elected PE should signal P=0,B=1, and the rest of the PEs in clear, the Backup elected PE should advertise the P Flag clear and
the same ES should signal P=0,B=0. When the primary PE/ES fails, the the B Flag set, and the rest of the PEs in the same ES should signal
primary PE will withdraw the associated Ethernet A-D routes for the both P and B Flags clear. When the primary PE/ES fails, the primary
VPWS service instance from the remote PE, the remote PEs should then 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 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 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 will be a newly elected primary PE and newly elected backup PE that
signal the P and B Flags as described. A remote PE SHOULD receive P=1 will signal the P and B Flags as described. A remote PE SHOULD
from only one Primary PE and a B=1 from only one Backup PE. However receive the P Flag set from only one Primary PE and the B Flag set
during transient situations, a remote PE receiving P=1 from more than from only one Backup PE. However during transient situations, a
one PE will select the last advertising PE as the primary PE when remote PE receiving a P Flag set from more than one PE will select
forwarding traffic. A remote PE receiving B=1 from more than one PE the last advertising PE as the primary PE when forwarding traffic. A
will select only one backup PE. A remote PE MUST receive P=1 from at remote PE receiving a B Flag set from more than one PE will select
least one PE before forwarding traffic. the last advertising PE as the 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 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- NOT be set and control word MUST NOT be used when sending EVPN-
encapsulated packets over a P2P LSP. encapsulated packets over a P2P LSP.
4 Operation 4 Operation
The following figure shows an example of a P2P service deployed with The following figure shows an example of a P2P service deployed with
EVPN. EVPN.
Ethernet Ethernet Ethernet Ethernet
Native |<--------- EVPN Instance ----------->| Native Native |<--------- EVPN Instance ----------->| Native
Service | | Service Service | | Service
(AC) | |<-PSN1->| |<-PSN2->| | (AC) (AC) | |<-PSN1->| |<-PSN2->| | (AC)
skipping to change at page 9, line 41 skipping to change at page 9, line 46
| EVPN Inter-provider point | | EVPN Inter-provider point |
| | | |
|<---------------- Emulated Service -------------------->| |<---------------- Emulated Service -------------------->|
Figure 3: EVPN-VPWS Deployment Model Figure 3: EVPN-VPWS Deployment Model
iBGP sessions are established between PE1, PE2, ASBR1 and ASBR3, iBGP sessions are established between PE1, PE2, ASBR1 and ASBR3,
possibly via a BGP route-reflector. Similarly, iBGP sessions are possibly via a BGP route-reflector. Similarly, iBGP sessions are
established between PE3, PE4, ASBR2 and ASBR4. eBGP sessions are established between PE3, PE4, ASBR2 and ASBR4. eBGP sessions are
established among ASBR1, ASBR2, ASBR3, and ASBR4. established among ASBR1, ASBR2, ASBR3, and ASBR4.
All PEs and ASBRs are enabled for the EVPN SAFI and exchange per EVI 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- Ethernet A-D routes, one route per VPWS service instance. For inter-
AS option B, the ASBRs re-advertise these routes with NEXT_HOP AS option B, the ASBRs re-advertise these routes with the NEXT_HOP
attribute set to their IP addresses as per [RFC4271]. The link attribute set to their IP addresses as per [RFC4271]. The link
between the CE and the PE is either a C-tagged or S-tagged interface, 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 as described in [802.1Q], that can carry a single VLAN tag or two
nested VLAN tags and it is configured as a trunk with multiple VLANs, nested VLAN tags and it is configured as a trunk with multiple VLANs,
one per VPWS service instance. It should be noted that the VLAN ID one per VPWS service instance. It should be noted that the VLAN ID
used by the customer at either end of a VPWS service instance to used by the customer at either end of a VPWS service instance to
identify that service instance may be different and EVPN doesn't identify that service instance may be different and EVPN doesn't
perform that translation between the two values. Rather, the MPLS perform that translation between the two values. Rather, the MPLS
label will identify the VPWS service instance and if translation is label will identify the VPWS service instance and if translation is
needed, it should be done by the Ethernet interface for each service. 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 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 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. 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 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 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 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 on all PEs attached to that ES. This allows an ingress PE in a
multihoming all-active scenario to perform flow-based load-balancing multihoming all-active scenario to perform flow-based load-balancing
of traffic flows to all of the PEs attached to that ES. In all cases of traffic flows to all of the PEs attached to that ES. In all cases
traffic follows the transport paths, which may be asymmetric. traffic follows the transport paths, which may be asymmetric.
The VPWS service instance identifier encoded in the Ethernet Tag ID The VPWS service instance identifier encoded in the Ethernet Tag ID
in an advertised per EVI Ethernet A-D route MUST either be unique 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 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 per-EVI Ethernet A-D route is re-advertised by the ASBR from one AS
to the other AS. to the other AS.
Per ES Ethernet A-D route can be used for mass withdraw to withdraw 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-home site all per-EVI Ethernet A-D routes associated with the multi-home site
on a given PE. on a given PE.
5 EVPN Comparison to PW Signaling 5 EVPN Comparison to PW Signaling
In EVPN, service endpoint discovery and label signaling are done In EVPN, service endpoint discovery and label signaling are done
concurrently using BGP. Whereas, with VPWS based on [RFC4448], label concurrently using BGP. Whereas, with VPWS based on [RFC4448], label
signaling is done via LDP and service endpoint discovery is either signaling is done via LDP and service endpoint discovery is either
through manual provisioning or through BGP. through manual provisioning or through BGP.
In existing implementation of VPWS using pseudowires(PWs), redundancy In existing implementations of VPWS using pseudowires(PWs),
is limited to single-active mode, while with EVPN implementation of redundancy is limited to single-active mode, while with EVPN
VPWS both single-active and all-active redundancy modes can be implementation of VPWS both single-active and all-active redundancy
supported. modes can be supported.
In existing implementation with PWs, backup PWs are not used to carry In existing implementations with PWs, backup PWs are not used to
traffic, while with EVPN, traffic can be load-balanced among carry traffic, while with EVPN, traffic can be load-balanced among
different PEs multi-homed to a single CE. different PEs multi-homed to a single CE.
Upon link or node failure, EVPN can trigger failover with the Upon link or node failure, EVPN can trigger failover with the
withdrawal of a single BGP route per EVPL service or multiple EVPL withdrawal of a single BGP route per EVPL service or multiple EVPL
services, whereas with VPWS PW redundancy, the failover sequence services, whereas with VPWS PW redundancy, the failover sequence
requires exchange of two control plane messages: one message to requires exchange of two control plane messages: one message to
deactivate the group of primary PWs and a second message to activate deactivate the group of primary PWs and a second message to activate
the group of backup PWs associated with the access link. the group of backup PWs associated with the access link.
Finally, EVPN may employ data plane egress link protection mechanisms Finally, EVPN may employ data plane egress link protection mechanisms
not available in VPWS. This can be done by the primary PE (on local 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 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 by the backup PE to encapsulate the traffic and direct it to the
PE. backup PE.
6 Failure Scenarios 6 Failure Scenarios
On a link or port failure between the CE and the PE for both single On a link or port failure between the CE and the PE for both single
and multi-homed CEs, unlike [RFC7432] the PE MUST withdraw all the and multi-homed CEs, unlike [RFC7432] the PE MUST withdraw all the
associated Ethernet A-D routes for the VPWS service instances on the associated Ethernet A-D routes for the VPWS service instances on the
failed port or link. failed port or link.
6.1 Single-Homed CEs 6.1 Single-Homed CEs
Unlike [RFC7432], EVPN-VPWS uses Ethernet A-D route advertisements Unlike [RFC7432], EVPN-VPWS uses Ethernet A-D route advertisements
for single-homed Ethernet Segments. Therefore, upon a link/port for single-homed Ethernet Segments. Therefore, upon a link/port
failure of this single-homed Ethernet Segment, the PE MUST withdraw failure of this single-homed Ethernet Segment, the PE MUST withdraw
the associated per EVI Ethernet A-D routes. the associated per-EVI Ethernet A-D routes.
6.2 Multi-Homed CEs 6.2 Multi-Homed CEs
For a faster convergence in multi-homed scenarios with either Single- For a faster convergence in multi-homed scenarios with either Single-
Active Redundancy or All-active redundancy, mass withdraw technique Active Redundancy or All-active redundancy, a mass withdraw technique
is used. A PE previously advertising a per ES Ethernet A-D route, can 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 withdraw this route by signaling to the remote PEs to switch all the
VPWS service instances associated with this multi-homed ES to the VPWS service instances associated with this multi-homed ES to the
backup PE backup PE.
7 Acknowledgements 7 Acknowledgements
The authors would like to acknowledge Jeffrey Zhang, Wen Lin, Nitin The authors would like to acknowledge Jeffrey Zhang, Wen Lin, Nitin
Singh, Senthil Sathappan and Vinod Prabhu for their feedback and Singh, Senthil Sathappan, Vinod Prabhu, Himanshu Shah, Iftekhar
Hussain, Alvaro Retana and Acee Lindem for their feedback and
contributions to this document. contributions to this document.
8 Security Considerations 8 Security Considerations
The mechanisms in this document use EVPN control plane as defined in The mechanisms in this document use EVPN control plane as defined in
[RFC7432]. Security considerations described in [RFC7432] are equally [RFC7432]. Security considerations described in [RFC7432] are equally
applicable. applicable.
This document uses MPLS and IP-based tunnel technologies to support This document uses MPLS and IP-based tunnel technologies to support
data plane transport. Security considerations described in [RFC7432] data plane transport. Security considerations described in [RFC7432]
skipping to change at page 12, line 4 skipping to change at page 12, line 10
The mechanisms in this document use EVPN control plane as defined in The mechanisms in this document use EVPN control plane as defined in
[RFC7432]. Security considerations described in [RFC7432] are equally [RFC7432]. Security considerations described in [RFC7432] are equally
applicable. applicable.
This document uses MPLS and IP-based tunnel technologies to support This document uses MPLS and IP-based tunnel technologies to support
data plane transport. Security considerations described in [RFC7432] data plane transport. Security considerations described in [RFC7432]
and in [ietf-evpn-overlay] are equally applicable. and in [ietf-evpn-overlay] are equally applicable.
9 IANA Considerations 9 IANA Considerations
IANA has allocated the following EVPN Extended Community sub-type: IANA has allocated the following EVPN Extended Community sub-type:
SUB-TYPE VALUE NAME Reference SUB-TYPE VALUE NAME Reference
0x04 EVPN Layer 2 attributes [RFCXXXX] 0x04 EVPN Layer 2 Attributes [RFCXXXX]
This document creates a registry called "EVPN Layer 2 attributes This document creates a registry called "EVPN Layer 2 Attributes
Control Flags". New registrations will be made through the "RFC Control Flags". New registrations will be made through the "RFC
Required" procedure defined in [RFC5226]. Required" procedure defined in [RFC5226].
Initial registrations are as follows: Initial registrations are as follows:
P Advertising PE is the Primary PE. P Advertising PE is the Primary PE.
B Advertising PE is the Backup PE. B Advertising PE is the Backup PE.
C Control word [RFC4448] MUST be present C Control word [RFC4448] MUST be present.
10 References 10 References
10.1 Normative References 10.1 Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/RFC2119, March Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/RFC2119, March
1997, <http://www.rfc-editor.org/info/rfc2119>. 1997, <http://www.rfc-editor.org/info/rfc2119>.
[RFC7432] Sajassi, A., Ed., Aggarwal, R., Bitar, N., Isaac, A., [RFC7432] Sajassi, A., Ed., Aggarwal, R., Bitar, N., Isaac, A.,
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