wdiff draft-boutros-l2vpn-evpn-vpws-03.txt draft-boutros-l2vpn-evpn-vpws-04.txt

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

John Drake
Juniper Networks

Jeff Tantsura
Ericsson

Dirk Steinberg
Steinberg Consulting

Thomas Beckhaus
Deutsche Telecom

Expires: August 18, 2014 February 14, January 3, 2015 July 2, 2014

VPWS support in E-VPN
draft-boutros-l2vpn-evpn-vpws-03.txt
draft-boutros-l2vpn-evpn-vpws-04.txt

Abstract

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

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Table of Contents

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

1 Introduction

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

[EVPN] has the ability to forward customer traffic to/from a given
customer Attachment Circuit (AC), aka Ethernet Segment in EVPN
terminology, without any MAC lookup. This capability is ideal in
providing p2p services (aka VPWS services). [MEF] defines Ethernet
Virtual Private Line (EVPL) service as p2p service between a pair of
ACs (designated by VLANs). VLANs) and Ethernet Private Line (EPL) service, in
which all traffic flows are between a single pair of ESes. EVPL can
be considered as a VPWS with only two ACs. In delivering an EVPL
service, the traffic forwarding capability of EVPN based on the
exchange of a pair of Ethernet AD routes is used; whereas, for more
general VPWS, traffic forwarding capability of EVPN based on the
exchange of a group of Ethernet AD routes (one Ethernet AD route per
AC/segment) is used. In a VPWS service, the traffic from an
originating Ethernet Segment can be forwarded only to a single
destination Ethernet Segment; hence, no MAC lookup is needed and the
MPLS label associated with the per-EVI Ethernet AD route can be used
in forwarding user traffic to the destination AC.

In current PW redundancy mechanisms, convergence time

Both services are supported by using the Per EVI Ethernet AD route
which contains an Ethernet Segment Identifier, in which the customer
ES is encoded, and an Ethernet Tag, in which the VPWS service
instance identifier is encoded. I.e., for both EPL and EVPL
services, a function specific VPWS service instance is identified by a pair of
Per EVI Ethernet AD routes which together identify the VPWS service
instance endpoints and the VPWS service instance. In the control
plane convergence characteristics. However, with EVPN it the VPWS service instance is possible to attain faster convergence through identified using the use of data- VPWS service
instance identifiers advertised by each PE and in the data plane prefix independent convergence, upon node or link failure.

This document proposes the use of
MPLS label advertised by one PE is used by the other PE to send it
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. The Ethernet Segment identifier encoded in
he per EVI Ethernet AD route is not used to signal
labels identify the service,
however it can be used for P2P Ethernet services. flow-based load-balancing and mass
withdraw functions.

As with standard EVPN, the Per ES Ethernet AD route is used for fast
convergence upon link or node failure and the Ethernet Segment route can be
is used to synchronize state between for auto-discovery of the PEs attached to
the same a given multi-homed Ethernet Segment.
CE and to synchronize state between them.

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.

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

EVI: EVPN Instance.

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

1.2 Requirements

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

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

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

4. The VLAN tag on the access trunk only has PE-local significance.

The VLAN tag on the remote end could be different, and could also be
double tagged when the other side is single tagged.

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

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

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

2. BGP Extensions

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

This document proposes the use of the per Per EVI Ethernet AD route to
signal P2P VPWS services. The Ethernet Segment Identifier field is set to
the ESI of the attachment circuit of customer ES and the VPWS service instance. The Ethernet Tag field is set to 0 in the case of an Ethernet Private
Wire service, VPWS service
instance identifier. For both EPL and to EVPL services, for a given
VPWS service instance the VLAN pair of PEs instantiating that VPWS service
instance will each advertise a Per EVI Ethernet AD route with its
VPWS service instance identifier associated and will each be configured with the
other PE's VPWS service
for instance identifier. When each PE has
received the other PE's

Per EVI Ethernet Virtual Private Wire service. AD 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 that with which the Per EVI
Ethernet AD route is tagged identifies the VPN associated with EVPN instance in which the p2p
EVPLs where each EVPL
VPWS service instance is identified by <ESI,Eth tag>. configured. It is the operator's choice as
to how many and which VPWS service instances are configured in a
given EVPN instance. However, a given EVPN instance MUST NOT be
configured with both VPWS service instances and standard EVPN multi-
point services.

3 Operation

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

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

All PEs and ASBRs are enabled for the EVPN SAFI, SAFI and exchange EVPN Per EVI
Ethernet A-D routes - AD routes, one route per AC. The VPWS service instance. For inter-
AS option B, the ASBRs re-advertise the
Ethernet A-D these routes with Next Hop
attribute set to their IP addresses. The link between the CE and the
PE is either a C-tagged or S-tagged interface, as described in
[802.1Q], that can carry a single VLAN tag or two nested VLAN tags. This interface tags
and it is set up configured as a trunk with multiple VLANs.

A VLANs, one per VPWS with multiple sites or multiple EVPL services on the same CE
port can
service instance. It should be included in one EVI between 2 or more PEs. An Ethernet
Tag corresponding to each P2P connection and known to both PEs is noted that the VLAN ID used by the
customer at either end of a VPWS service instance to identify that
service instance may be different and EVPN doesn't perform that
translation between the services multiplexed in two values. Rather, this should be done by
the same EVI. Ethernet interface.

For CE single-homing single-homed CE, in an advertised Per EVI Ethernet AD route the
ESI field must be is set to 0 in and the Ethernet
AD route, the <Eth-tag> Tag field will be is set to the AC-ID of VPWS
service instance identifier that identifies the EVPL or EPL service.

For CE multi-homing, the a multi-homed CE, in an advertised Per EVI Ethernet AD Route encodes route the
ESI associated
with the CE. This allows flow-based load-balancing of traffic between
PEs connected field is set to the same multi-homed CE. The AC ID encoded in CE's ESI and the
tag Ethernet Tag field is set to
the VPWS service instance identifier, which MUST be have the same value
on both all PEs attached to the site. The
Ethernet Segment route may be used too, for discovery that ES. This allows an ingress PE to perform
flow-based load-balancing of multi-homed
CEs. traffic flows to all of the PEs attached
to that ES. In all cases traffic follows the transport paths, which
may be asymmetric.

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

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

The <Eth-tag> Tag
field value representing the AC-ID of the EPL/EVPL
service of the remote side may in an advertised Per EVI Ethernet AD route MUST either be equal
unique across all ASs, or an ASBR needs to perform a translation when
the local side.

An operator may choose to associate many per EVI EAD routes with
different ESIs and tags to the same Route-Target (RT) extended
community attribute. As such, Ethernet AD route is re-advertised by the association of per EVI EAD routes ASBR from one
AS to the same RT is a network operator design choice. other AS.

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

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

4 EVPN Comparison to PW Signaling

In EVPN, service endpoint discovery and label signaling are done
concurrently using BGP. Whereas, with VPWS based on [RFC4448], label
signaling is done via LDP and service endpoint discovery is either
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.

Upon link or node failure, EVPN can trigger failover with the
withdrawal of a single BGP route per EVPL service or multiple EVPL
services, whereas with VPWS PW redundancy, the failover sequence
requires exchange of two control plane messages: one message to
deactivate the group of primary PWs and a second message to activate
the group of backup PWs associated with the access link. Finally,
EVPN may employ data plane local repair mechanisms not available in
VPWS.

5 ESI Bandwidth

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

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

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

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

6 ESI value derivation and Eth-tag setting

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

The <Eth-tag> field in the Ethernet A-D per EVI route is set to the
AC-ID representing the EPL or EVPL service. This is different from
the baseline [EVPN] Where <Eth-tag> field is set only for VLAN-aware
bundle service.

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

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

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

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

7 VPWS with multiple sites

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

8 Acknowledgements

The authors would like to acknowledge Wen Lin contributions to this
document.

9 Security Considerations

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

TBD

TBD.

11 References

10.1

11.1 Normative References

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

10.2

11.2 Informative References

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

[EVPN] A. Sajassi, R. Aggarwal et. al., "BGP MPLS Based Ethernet
VPN", draft-ietf-l2vpn-evpn-04.txt.

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

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

Authors' Addresses
Sami Boutros
Cisco
Email: sboutros@cisco.com

Ali Sajassi
Cisco
Email: sajassi@cisco.com

Samer Salam
Cisco
Email: ssalam@cisco.com

John Drake
Juniper Networks
Email: jdrake@juniper.net

Jeff Tantsura
Ericsson
Email: jeff.tantsura@ericsson.com

Dirk Steinberg
Steinberg Consulting
Email: dws@steinbergnet.net

Patrice Brissette
Cisco
Email: pbrisset@cisco.com

Thomas Beckhaus
Deutsche Telecom
Email:Thomas.Beckhaus@telekom.de>