INTERNET-DRAFT Sami Boutros
Intended Status: Standard Track Ali Sajassi
Samer Salam
Cisco Systems
John Drake
Juniper Networks
Jeff Tantsura
Ericsson
Expires: August 28, 2013 February 24, 2013
VPWS support in E-VPN
draft-boutros-l2vpn-evpn-vpws-01.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: active/standby as well as
active/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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Copyright and License Notice
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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 ESI Bandwidth Attribute . . . . . . . . . . . . . . . . . . . . 5
6 VPWS with multiple sites . . . . . . . . . . . . . . . . . . . . 6
7 Security Considerations . . . . . . . . . . . . . . . . . . . . 6
8 IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 6
9 References . . . . . . . . . . . . . . . . . . . . . . . . . . 6
9.1 Normative References . . . . . . . . . . . . . . . . . . . 6
9.2 Informative References . . . . . . . . . . . . . . . . . . 7
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 7
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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 applies the benefits of E-VPN to p2p services.
These benefits include active/standby AC redundancy as well as
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 (AC), aka Ethernet Segment in E-VPN
terminology, 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, the traffic forwarding capability of E-VPN using only a
pair of Ethernet AD routes is used; whereas, for more general VPWS,
traffic forwarding capability of E-VPN using a group of Ethernet AD
routes (one Ethernet AD route per AC/segment) is used. Since in VPWS
services, the traffic from an originating Ethernet Segment can go
only to a single destination Ethernet Segment, 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 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 state between the PEs attached to
the same multi-homed 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.
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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 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 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 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 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 ESI Bandwidth Attribute
The ESI Bandwidth Attribute is a new optional BGP attribute that will
be associated with the Ethernet AD route used to realize the EVPL
services.
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+---------------------------------------+
| Type (2 octets) |
+---------------------------------------+
| Length (2 octets) |
+---------------------------------------+
| Flags (1 Octet) |
+---------------------------------------+
| Reserved=0(1 Octet) |
+---------------------------------------+
| Reverse SENDER_TSPEC |
+---------------------------------------+
The content of the SENDER_TSPEC are as defined in [RFC 2210] section
3.1.
When a PE receives this attribute for a given EVPL it MUST request
the appropriate resources described in the SENDER_TSPEC 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 attribute and with the Flags set
to 1 "PSN Resources Unavailable".
6 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.
7 Security Considerations
This document does not introduce any additional security constraints.
8 IANA Considerations
TBD
9 References
9.1 Normative References
[KEYWORDS] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
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[RFC 2210] Wroclawski, J. "The Use of RSVP with IETF Integrated
Services", RFC 2210, September 1997
9.2 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
John Drake
Juniper Networks
Email: jdrake@juniper.net
Jeff Tantsura
Ericsson
Email: jeff.tantsura@ericsson.com
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