INTERNET-DRAFT Sami Boutros
Intended Status: Informational Ali Sajassi
Samer Salam
Expires: January 1, 2013 June 30, 2012
VPWS support in E-VPN
draft-boutros-l2vpn-evpn-vpws-00.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: 1) active/standby redundancy, 2)
active/active multi-homing with flow-based load-balancing, 3)
eliminates the need for single-segment and multi-segment PW
signaling, and 4) provides faster convergence using data-plane prefix
independent convergence upon node or link failure in comparison to
control-plane convergence with PW redundancy.
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Copyright and License Notice
Copyright (c) 2012 IETF Trust and the persons identified as the
document authors. All rights reserved.
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Table of Contents
1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
1.1 Terminology . . . . . . . . . . . . . . . . . . . . . . . . 3
2. BGP Extensions . . . . . . . . . . . . . . . . . . . . . . . . 4
3 Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
4 E-VPN Comparison to PW Signaling . . . . . . . . . . . . . . . . 5
5 VPWS with multiple sites . . . . . . . . . . . . . . . . . . . . 5
6 Security Considerations . . . . . . . . . . . . . . . . . . . . 6
7 IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 6
8 References . . . . . . . . . . . . . . . . . . . . . . . . . . 6
8.1 Normative References . . . . . . . . . . . . . . . . . . . 6
8.2 Informative References . . . . . . . . . . . . . . . . . . 6
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 6
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1 Introduction
This document describes how E-VPN can be used to support virtual
private wire service (VPWS) in MPLS/IP networks. The use of E-VPN
mechanisms for VPWS introduces all the benefits of E-VPN to p2p
services. These benefits include active/standby AC redundancy,
active/active multi-homing with flow-based load-balancing.
Furthermore, the use of E-VPN for VPWS eliminates the need for
signaling single-segment and multi-segment PWs for p2p Ethernet
services.
[E-VPN] has the ability to forward customer traffic to/from a given
customer Attachment Circuit (aka Ethernet AD route) without any MAC
lookup. This capability is ideal in providing P2P services (aka VPWS
services). [MEF] defines 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, traffic forwarding
capability of E-VPN between a pair of Ethernet AD routes is used;
whereas, for more general VPWS, traffic forwarding capability of E-
VPN among a group of Ethernet AD routes (one Ether AD route per
AC/site) is used. Since in VPWS services, the traffic from an
originating Ether AD route can go only to a single destination Ether
AD route, no MAC lookup is needed and MPLS label associated with the
destination Ether 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 E-VPN 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 E-VPN, the Ethernet Segment
route can be used to synchronize LACP and other state between the PEs
attached to the same multi-homed device.
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.
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OAM: Operations, Administration and Maintenance.
PE: Provide Edge Node.
CE: Customer Edge device e.g., host or router or switch.
EVI: E-VPN Instance.
2. BGP Extensions
[E-VPN] defines a new BGP NLRI for advertising different route types
for E-VPN operation. This document does not define any new BGP
messages, but rather repurposes one of the routes as described next.
This document proposes the use of the 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 with the Ethernet Tag field when non-zero
3 Operation
The following figure shows an example of a P2P service deployed with
E-VPN.
Ethernet Ethernet
Native |<---------E-VPN 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 |
| | |
| | |
| E-VPN Inter-provider point |
| |
|<---------------- Emulated Service -------------------->|
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iBGP sessions will be established between PE1, PE2, ASBR1 and ASBR3,
possibly via a BGP route-reflector. Similarly, iBGP sessions will be
established between PE3, PE4, ASBR2 and ASBR4. eBGP sessions will be
established among ASBR1, ASBR2, ASBR3, and ASBR4.
All PEs and ASBRs are enabled for the E-VPN SAFI, and exchange E-VPN
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 an C-TAG or S-TAG
interface as described in [802.1Q] that can carry a single vlan tag
or two vlan tags nested in each other. This interface is setup 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
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 ID 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.
4 E-VPN Comparison to PW Signaling
In E-VPN, 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 VPWS, redundancy is
limited to Active/Standby mode, while with E-VPN both Active/Active
and Active/Standby redundancy modes can be supported. In VPWS, backup
PWs are not used to carry traffic, while E-VPN traffic can be load-
balanced among primary and secondary PEs. On link or node failure, E-
VPN can trigger failover with the withdrawal of a single BGP route
per service, 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, E-
VPN may employ data plane local repair mechanisms not available in
VPWS.
5 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)
can be setup automatically without any explicit provisioning of P2P
connections among the sites.
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6 Security Considerations
This document does not introduce any additional security constraints.
7 IANA Considerations
TBD
8 References
8.1 Normative References
[KEYWORDS] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
8.2 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-00.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
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