wdiff draft-boutros-l2vpn-evpn-vpws-02.txt draft-boutros-l2vpn-evpn-vpws-03.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
Expires: April 24, August 18, 2014 February 14, 2014 October 21, 2013

VPWS support in E-VPN
draft-boutros-l2vpn-evpn-vpws-02.txt
draft-boutros-l2vpn-evpn-vpws-03.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.

Status of this Memo

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Table of Contents

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

1 Introduction

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

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

In current PW redundancy mechanisms, convergence time is a function
of control plane convergence characteristics. However, with EVPN it
is possible to attain faster convergence through the use of data-
plane prefix independent convergence, upon node or link failure.

This document proposes the use of the Ethernet AD route to signal
labels for P2P Ethernet services. As with EVPN, the Ethernet Segment
route can be used to synchronize state between the PEs attached to
the same multi-homed Ethernet Segment.

1.1 Terminology

The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"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 EVI Ethernet AD route to
signal P2P services. The Ethernet Segment Identifier field is set to
the ESI of the attachment circuit of the VPWS service instance. The
Ethernet Tag field is set to 0 in the case of an Ethernet Private
Wire service, and to the VLAN identifier associated with the service
for Ethernet Virtual Private Wire service. The route is associated
with a Route-Target (RT)
extended community attribute that identifies the service instance (together VPN associated with the Ethernet Tag field when non-
zero). p2p
EVPLs where each EVPL is identified by <ESI,Eth tag>.

3 Operation

The following figure shows an example of a P2P service deployed with
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, and exchange EVPN
Ethernet A-D routes - one route per AC. The ASBRs re-advertise the
Ethernet A-D routes with Next Hop attribute set to their IP
addresses. The link between the CE and the PE is either a C-tagged or
S-tagged interface, as described in [802.1Q], that can carry a single
VLAN tag or two nested VLAN tags. This interface is set up as a trunk
with multiple VLANs.

A VPWS with multiple sites or multiple EVPL services on the same CE
port can be included in one EVI between 2 or more PEs. An Ethernet
Tag corresponding to each P2P connection and known to both PEs is
used to identify the services multiplexed in the same EVI.

For CE single-homing the ESI field must be set to 0 in the Ethernet
AD route, the <Eth-tag> field will be set to the AC-ID of the EVPL or
EPL service.

For CE multi-homing, the Ethernet AD Route encodes the ESI associated
with the CE. This allows flow-based load-balancing of traffic between
PEs connected to the same multi-homed CE. The VPN AC ID encoded in the
tag field MUST be the same on both PEs attached to the site. The
Ethernet Segment route may be used too, for discovery of multi-homed
CEs. In all cases traffic follows the transport paths, which may be
asymmetric.

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

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

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

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

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

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

4 EVPN Comparison to PW Signaling

In EVPN, service endpoint discovery and label signaling are done
concurrently using BGP. Whereas, with VPWS based on [RFC4448], label
signaling is done via LDP and service endpoint discovery is either
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 primary
and secondary PEs.
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 service, 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 10 bytes ESI value will contain:-

1) 6-byte System-ID that is globally unique. These 6 bytes set per [EVPN] procedures - e.g., it is set to 0
for single home sites and can be
auto derived using a mechanism similar 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 one used for
automating B-MAC Address Assignment in [PBB-EVPN].

2) 4-byte Local-AC-ID that
AC-ID representing the EPL or EVPL service. This is unique within each PE. different from
the baseline [EVPN] Where <Eth-tag> field is set only for VLAN-aware
bundle service.

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

"EVI" for VPWS services MUST be different from multipoint services
specified in baseline [EVPN]. This implies the associated AC-
ID globally unique. A pair of such globally corresponding RTs for
VPWS and multipoint services needs to be different.

AC-IDs in the <Eth-tag> field MUST be unique AC-ID identifies 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
point-to-point service (EVPL given EVPL or EPL) uniquely in EPL service, are
configured by an operator to connect the provider
network. 2 sides of the EPL/EVPL
services at both sides of the services.

7 VPWS with multiple sites

The future revision of this draft will describe how a 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. sites is outside the scope
of this document.

8 Security Considerations

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

TBD

10 References

10.1 Normative References

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

10.2 Informative References

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

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

[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
170 West Tasman Drive
San Jose, CA 95134, US
Email: sboutros@cisco.com

Ali Sajassi
Cisco
170 West Tasman Drive
San Jose, CA 95134, US
Email: sajassi@cisco.com

Samer Salam
Cisco
595 Burrard Street, Suite 2123
Vancouver, BC V7X 1J1, Canada
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