INTERNET-DRAFT Sami Boutros
Intended Status: Standard Track Ali Sajassi
Samer Salam
Cisco Systems
John Drake
Juniper Networks
Jeff Tantsura
Ericsson
Expires: April 24, 2014 October 21, 2013
VPWS support in E-VPN
draft-boutros-l2vpn-evpn-vpws-02.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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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 EVPN Comparison to PW Signaling . . . . . . . . . . . . . . . . 5
5 ESI Bandwidth . . . . . . . . . . . . . . . . . . . . . . . . . 6
6 ESI value derivation . . . . . . . . . . . . . . . . . . . . . . 6
7 VPWS with multiple sites . . . . . . . . . . . . . . . . . . . . 6
8 Security Considerations . . . . . . . . . . . . . . . . . . . . 6
9 IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 7
10 References . . . . . . . . . . . . . . . . . . . . . . . . . . 7
10.1 Normative References . . . . . . . . . . . . . . . . . . . 7
10.2 Informative References . . . . . . . . . . . . . . . . . . 7
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 7
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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.
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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".
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 with the Ethernet Tag field when non-
zero).
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 |
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| |-------+-----+ +-----+ +-----+ +-----+-------| |
+----+ | | 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 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 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. Upon link or node failure, EVPN can trigger
failover with the withdrawal of a single BGP route per service,
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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".
6 ESI value derivation
The 10 bytes ESI value will contain:-
1) 6-byte System-ID that is globally unique. These 6 bytes can be
auto derived using a mechanism similar to the one used for
automating B-MAC Address Assignment in [PBB-EVPN].
2) 4-byte Local-AC-ID that is unique within each PE.
The combination of System-ID and Local-AC-ID makes the associated AC-
ID globally unique. A pair of such globally unique AC-ID identifies a
point-to-point service (EVPL or EPL) uniquely in the provider
network.
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)
can be setup automatically without any explicit provisioning of P2P
connections among the sites.
8 Security Considerations
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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
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John Drake
Juniper Networks
Email: jdrake@juniper.net
Jeff Tantsura
Ericsson
Email: jeff.tantsura@ericsson.com
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