wdiff draft-boutros-l2vpn-evpn-vpws-01.txt draft-boutros-l2vpn-evpn-vpws-02.txt

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 April 24, 2014 October 21, 2013

VPWS support in E-VPN
draft-boutros-l2vpn-evpn-vpws-01.txt
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: active/standby single-active as well as
active/active 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

This Internet-Draft is submitted to IETF in full conformance with the
provisions of BCP 78 and BCP 79.

Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF), its areas, and its working groups. Note that
other groups may also distribute working documents as
Internet-Drafts.

Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress."

The list of current Internet-Drafts can be accessed at
http://www.ietf.org/1id-abstracts.html

The list of Internet-Draft Shadow Directories can be accessed at
http://www.ietf.org/shadow.html

This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents
(http://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents
carefully, as they describe your rights and restrictions with respect
to this document. Code Components extracted from this document must
include Simplified BSD License text as described in Section 4.e of
the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License.

Table of Contents

1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
1.1 Terminology . . . . . . . . . . . . . . . . . . . . . . . . 3
2. BGP Extensions . . . . . . . . . . . . . . . . . . . . . . . . 4
3 Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
4 E-VPN EVPN Comparison to PW Signaling . . . . . . . . . . . . . . . . 5
5 ESI Bandwidth Attribute . . . . . . . . . . . . . . . . . . . . 5 . . . . . 6
6 ESI value derivation . . . . . . . . . . . . . . . . . . . . . . 6
7 VPWS with multiple sites . . . . . . . . . . . . . . . . . . . . 6
7
8 Security Considerations . . . . . . . . . . . . . . . . . . . . 6
8
9 IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 6
9 7
10 References . . . . . . . . . . . . . . . . . . . . . . . . . . 6
9.1 7
10.1 Normative References . . . . . . . . . . . . . . . . . . . 6
9.2 7
10.2 Informative References . . . . . . . . . . . . . . . . . . 7
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 7

1 Introduction

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

[E-VPN]

[EVPN] has the ability to forward customer traffic to/from a given
customer Attachment Circuit (AC), aka Ethernet Segment in E-VPN EVPN
terminology, without any MAC lookup. This capability is ideal in
providing p2p services (aka VPWS services). [MEF] defines EVPL 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 E-VPN using only EVPN based on the exchange of a pair of Ethernet AD
routes is used; whereas, for more general VPWS, traffic forwarding
capability of E-VPN using EVPN based on the exchange of a group of Ethernet AD
routes (one Ethernet AD route per AC/segment) is used. Since in In a VPWS
services,
service, the traffic from an originating Ethernet Segment can go be
forwarded only to a single destination Ethernet Segment, 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 E-VPN EVPN it
is possible to attain faster convergence through the use of data-
plane prefix independent convergence 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, 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: E-VPN 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

[E-VPN]

[EVPN] defines a new BGP NLRI for advertising different route types
for E-VPN 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
E-VPN.
EVPN.
Ethernet Ethernet
Native |<---------E-VPN Instance------------>| |<--------- 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 |
| | |
| | |
| E-VPN EVPN Inter-provider point |
| |
|<---------------- Emulated Service -------------------->|

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

All PEs and ASBRs are enabled for the E-VPN EVPN SAFI, and exchange E-VPN 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 E-VPN EVPN Comparison to PW Signaling

In E-VPN, 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 VPWS, existing
implementation of VPWS using pseudowires(PWs), redundancy is limited
to Active/Standby single-active mode, while with E-VPN EVPN implementation of VPWS both Active/Active
single-active and Active/Standby all-active redundancy modes can be supported. In VPWS,
existing implementation with PWs, backup PWs are not used to carry
traffic, while E-VPN with EVPN, traffic can be load-
balanced load-balanced among primary
and secondary PEs. On Upon link or node failure, E-
VPN EVPN 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 EVPN 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 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.

+---------------------------------------+
| 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 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 attribute and with the Flags set = All FFs to 1 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
This document does not introduce any additional security constraints.
8
9 IANA Considerations

TBD

10 References

9.1

10.1 Normative References

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

[RFC 2210] Wroclawski, J. "The Use of RSVP with IETF Integrated
Services", RFC 2210, September 1997

9.2

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-00.txt. 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