One document matched: draft-lee-l2tpext-pwe3-vpl-00.txt
Internet Engineering Task Force CY Lee
INTERNET DRAFT M Higashiyama
November 2002
Ethernet Pseudo-wire over L2TPv3 (multipoint support)
<draft-lee-l2tpext-pwe3-vpl-00.txt>
Status of this memo
This document is an Internet-Draft and is in full conformance with
all provisions of Section 10 of RFC2026.
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Abstract
This draft describes the emulation of an Ethernet segment or
broadcast domain over an IP network and the use of L2TPv3 to
transport Ethernet frames.
1. Terminology
LCCE L2TP Control Connection Endpoint (See [L2TPv3])
NSP Native Service Processing
PSN Packet Switched Network
PW Pseudo-Wire
PWE3 Pseudo-Wire Emulation Edge to Edge (Working Group)
VPL Virtual Private LAN (aka Ethernet Pseudo-Wire)
2. Overview
To emulate an Ethernet broadcast domain, tunnels are setup between
sites (LCCE) of a VPL. At a site, Ethernet traffic of a VPL is
encapsulated in L2TP by a LCCE and transported over the IP network
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to another LCCE of the VPL. The receiving LCCE decapsulates the
Ethernet frame and forward the frame to the destination node in the
VPL.
[L2TP-ETH] specifies the transport of Ethernet frames from one point
to another point over L2TPv3. This draft describes the transport of
Ethernet traffic across multiple sites that belong to the same VPL,
including point to point transport of Ethernet frames using [L2TP-
ETH] and bridging at LCCEs. The scope of the application of this
draft in this initial version is [CE-VPL].
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The following two figures (adapted from [PWE3-frame]) describe the
reference models to support VPL services.
Emulated Service
(Broadcast Domain/"LAN", within dotted lines)
..................................
Native . . Native
Ethernet . . Ethernet
or . |<-- PSN Tunnel-->| . or
VLAN . . VLAN
Service . +----+ +----+ . Service
| . |LCCE| |LCCE| . |
Remote -------.--| 1 |=================| 2 |-.------- Remote
LAN | . | | | | . | LAN
Site 1 | . +----+ +----+ . | Site 2
. \\ // .
. \\ // .
. \\ // .
. PSN \\ // PSN .
. Tunnel \\ +----+ // Tunnel.
. \\|LCCE|// .
. \| 3 |/ .
. +----+ .
. | .
..................................
|
|
Native Ethernet or
VLAN Service
|
|
Remote LAN
Site 3
|
|
Remote ----------------|----------------Remote
LAN Site 1 | LAN Site 2
|
|----------------Remote
| LAN Site 3
Fig 1 Emulated Ethernet Segment/Ethernet Pseudo-Wire
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+-------------+ +-------------+
| Emulated | | Emulated |
| Ethernet | | Ethernet |
| (including | Emulated Service | (including |
| VLAN) |<==============================>| VLAN) |
| Services | | Services |
+-------------+ Ethernet Pseudo Wire +-------------+
|Encapsulation|<==============================>|Encapsulation|
|& Bridging | |& Bridging |
+-------------+ +-------------+
| | PSN Tunnel | |
| IP |<==============================>| IP |
+-------------+ +-------------+
| Physical | | Physical |
+-----+-------+ +-----+-------+
| |
| PSN |
| ____ ___ ____ |
| _/ \___/ \ _/ \__ |
| / \__/ \_ |
| / \ |
+========/ |===+
\ /
\ /
\ ___ ___ __ _/
\_/ \____/ \___/ \____/
Fig 3: VPL Protocol Stack Reference Model
3. Establishing L2TPv3 control connection and session
An L2TP control connection (as described in [L2TPv3]) is set up first
to each peer LCCE of a VPL (See "Tunnel Endpoints Information").
Ethernet PW type must be included in the Pseudo Wire Capabilities
list as described in [L2TP-ETH].
A point to point Ethernet PW to each peer LCCE belonging to the same
VPL, is established as an L2TP session. A new PW Type namely,
"Ethernet VPL" is defined. This parameter indicates to an LCCE
whether additional processing wrt multipoint service is required.
Each LCCE signals its PW type in a AVP [L2TPv3] Attribute Type TBA.
The PW ID is associated with an L2TP session as described in [L2TP-
ETH].
In this version of the draft, each L2TP session is associated with
one VPL only. Hence an LCCE does not need to add a globally unique
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identifier (VLAN ID) to frames for the purpose of identifying a frame
as belonging to the emulated broadcast domain, although the traffic
from a LAN site may or may not be VLAN tagged.
A virtual interface is created for every L2TP session setup to a
remote LCCE.
3.1 Tunnel Endpoint Authentication
If an LCCE authenticates the remote LCCE using L2TP, a Challenge AVP
is included in the L2TP control connection setup message, as
described in [L2TPv3]. If the expected response received from a LCCE
does not match, the establishment of the control connection MUST be
disallowed. A CHAP-like [RFC1994] authentication is used at each
LCCE. To use L2TP tunnel authentication, a single shared secret MUST
exist between the two LCCEs. [See section on "Tunnel Endpoint
Information"].
L2TP (Layer Two Tunneling Protocol) may use IPsec for tunnel
authentication as described in [L2TP-IPSEC] instead.
4. Bridging
An LCCE learns MAC addresses from the customer facing ports and the
virtual interfaces (or the tunnels to remote LCCE sites of a VPL).
When a new MAC address is learned, the MAC address is associated with
the virtual interface or ports where the frame arrives. When a frame
with the cached MAC address is received, the LCCE knows which virtual
interface or port to forward the frame to. When a frame with a new
MAC address is received, an LCCE floods the frame to all other ports
or virtual interfaces, except the interface where the frame is
received from. To optimize forwarding of traffic over a VPL see the
next section.
The learning, bridging, filtering and forwarding procedures are as
defined in [802.1d] and [802.1q], except that the ports on a switch
in this case can be a virtual interface as well as a physical port.
5. Optimizing bridging over a VPL
To optimize the forwarding of traffic in a VPL, a full mesh of
tunnels may be setup among LCCE sites. Since each LCCE has a direct
tunnel to other LCCEs, bridging may be modified such that traffic
arriving at an LCCE from another LCCE need not be forwarded to other
LCCEs. Spanning Tree Protocol (STP) may be turned off if there are no
additional connectivity among the LCCEs (e.g. "backdoor"
connectivity), apart from the full meshed of tunnels; otherwise STP
must be used to prevent forwarding loops.
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The states in setting up a full meshed of tunnels (over an IP
network) are only incurred at LCCEs.
6. Tunnel Endpoints Information
How the configurable tunnel parameters (e.g. IP addresses of remote
LCCEs) are obtained is not within the scope of this draft. [VPLS-
DNS] and [CE-AUTOCONFIG] are examples of mechanisms that may be used
to auto discover and distribute VPL site information.
7. PW Monitoring
The procedures for PW monitoring and fault detection described in
[L2TP-ETH] may be used to monitor the virtual interfaces or L2TP
sessions.
8. Acknowledgment
This draft benefited from discussions with Alexis Berthillier, Sasha
Cirkovic, Arnold Jansen, Jeremy DeClercq, Jeanne DeJaegher and
related discussions with the Ethernet over L2TPv3 design team, as
well as consultations with Mark Townsley and Danny McPherson.
Normative References
[802.1D] IEEE, "ISO/IEC 15802-3:1998,(802.1D, 1998 Edition),
Information technology --Telecommunications and information exchange
between systems --IEEE standard for local and metropolitan area
networks --Common specifications-Media access control (MAC) Bridges",
June, 1998.
[802.1Q] ANSI/IEEE Standard 802.1Q, "IEEE Standards for Local and
Metropolitan Area Networks: Virtual Bridged Local Area Networks",
1998 .
[802.3] IEEE, "ISO/IEC 8802-3: 2000 (E), Information
technology--Telecommunications and information exchange between
systems --Local and metropolitan area networks --Specific
requirements --Part 3: Carrier Sense Multiple Access with Collision
Detection (CSMA/CD) Access Method and Physical Layer Specifications",
2000.
[L2TPv3] Lau, J., Townsley, M., Valencia, A., Zorn, G., Goyret, I.,
Pall, G., Rubens, A., Palter, B., "Layer Two Tunneling Protocol
"L2TP"", (draft-ietf-l2tpext- l2tp-base-01.txt), work in progress,
July 2001.
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[L2TP-IPSEC] RFC 3193, B. Patel,B. Aboba,W. Dixon, G. Zorn, S. Booth
"Securing L2TP using IPSec"
[L2TP-ETH] Aggarwal, et al., Transport of Ethernet Frames over
L2TPv3, draft-ietf-l2tpext-pwe3-ethernet-00.txt, October 2002.
Informational References
[EOL2TP] M. Higashiyama, "Ethernet Over L2TP", (draft-higashiyama-
eol2tp-01.txt), November 2001
[Kompella] Kompella, K., Leelanivas, M., Vohra, Q., Bonica, R., Metz,
E., Ould-Brahim, H., Achirica, J., Z., "MPLS-based Layer 2 VPNs",
(draft-kompella- ppvpn-l2vpn-00.txt), work in progress, July 2001.
[Martini-encap] Martini, L., El-Aawar, N., Tappan, D., Rosen, E.,
Jayakumar, J., Vlachos, D., Liljenstolpe, C., Heron, G., Kompella,
K., Vogelsang, S., Shirron, J., Smith, T., Radoaca, V., Malis, A.,
Sirkay, V., Cooper, D., "Encapsulation Methods for Transport of
Layer 2 Frames Over IP and MPLS Networks", (draft-martini- l2circuit-
encap-mpls-03.txt), work in progress, July 2001.
[PWE3-frame] Pate, P., Xiao, X., So, T., Malis, A., Nadeau, T.,
White, C., Kompella, K., Johnson, T., "Framework for Pseudo Wire
Emulation Edge-to-Edge (PWE3)" (draft- pate-pwe3-framework-02.txt),
work in progress, July 2001.
[Laserre-Vkompella] Lasserre, M, Kompella, V, et al, "Virtual Private
LAN Services over MPLS" draft-lasserre-vkompella-ppvpn-vpls-01.txt,
March 2002
[VPLS-DNS] Heinanen, "DNS/LDP Based VPLS". draft-heinanen-dns-ldp-
vpls-00.txt, January 2002.
[CE-AUTOCONFIG] CY Lee, J DeClercq "CE Auto-Configuration", (draft-
lee-ppvpn-ce-auto-config-01.txt), work in progress, July 2002
[CE-VPL] CY Lee, M Higashiyama, "CE-based VPL", (draft-lee-ce-based-
vpl-00.txt), work in progress, July 2002
Authors' Information
Cheng-Yin Lee Cheng-Yin.Lee@alcatel.com
Mitsuru Higashiyama Mitsuru.Higashiyama@yy.anritsu.co.jp
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