Layer Two Tunneling Protocol Extensions (l2tpext)

Layer Two Tunneling Protocol Extensions (l2tpext)
-------------------------------------------------

Charter
Last Modified: 2006-10-09

Current Status: Active Working Group

Chair(s):
Ignacio Goyret <[email protected]>
Carlos Pignataro <[email protected]>

Internet Area Director(s):
Jari Arkko <[email protected]>
Mark Townsley <[email protected]>

Internet Area Advisor:
Mark Townsley <[email protected]>

Mailing Lists:
General Discussion:[email protected]
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Archive: http://www.ietf.org/mail-archive/web/l2tpext/index.html

Description of Working Group:

This group is responsible for extensions to the Layer 2 Tunneling
Protocol. Examples of L2TP "extensions" include any changes to the
L2TP encapsulation, control messages, or new AVPs sent in IETF
standard control messages.

I. L2TP Background:

L2TP (RFC2661) provides a means for tunneling PPP over IP. Because PPP
can effectivly carry any traffic (e.g., IP (RFC 1332), IPX (RFC 1552),
etc.) it can effectively be used to tunnel arbitrary protocols over
IP. L2TP provides:

- An extensible control protocol for dynamic setup, maintenance, and
teardown of multiple layer 2 tunnels between two logical endpoints.

- An encapsulation method for tunneling PPP frames between each
endpoint. This includes multiplexing of multiple, discrete, PPP
streams between each endpoint.

L2TP looks (in most ways) like just another point-to-point link to PPP
and may thereby take advantage of the work done for any protocol
defined
for use over a traditional PPP WAN link. It should be noted, however,
that the ability to dynamically establish a PPP connection between any
two IP connected endpoints brings new applications and challenges of
scale to existing PPP implementations and protocol definitions that
must
be considered.

As high-speed broadband access to the home replaces traditional dialup
infrastructure, L2TP has been utilized as one standard method for
aggregation and delivery of PPP connections over packet networks.
Thus,
rather than a relatively small scale or low speed circuit-switched
connection such as an analog modem or ISDN connection at the L2TP
Access Concentrator (LAC), we see PPP being received over ATM PVCs
which are generally higher speed and "always-on" vs. temporally
connected. Further, there are non-IETF standard PPP tunneling
protocols that have been developed and deployed, including PPPoE
(RFC 2516) and the 3GPP2 Wireless GPRS Tunneling Protocol Standard
(http://www.3gpp.org) that interface with L2TP at various points in
the
network. While it is unfortunate that there is more than one standard
method for tunneling PPP defined, each of these have their own
installed bases and specific application-driven nuances. Proper
integration with these various tunneling methods as they "hand-off" to
the L2TP portion of the network must be ensured.

II. L2TP Interaction with PWE3 for Pseudo-Wire Transport:

In addition to tunneling PPP, L2TPEXT will develop protocol extensions
necessary for the tunneling of specific "pseudo-wires" as defined in
the PWE3 WG. Specific milestone identification for this activity is
currently subject to ongoing work and results from PWE3.

III. WG Activities

The Working Group is currently focussed on the following activities:

- RFC2661 bundles data transport, protocol signaling, and PPP
emulation methods into a single document. This working group will
separate RFC2661 into stand-alone documents for greater
modularity. This will consist of a base L2TP document defining
common tunneling constructs and encapsulation, and a PPP document
defining the use of these constructs for tunneling of PPP sessions
as defined in RFC2661. Documents for tunneling of pseudo-wires
defined in PWE3 will be forthcoming as well.

As RFC2661 is rewritten to separate the tunnel setup and maintenance
sections for support of new applications and increased modularity,
some modifications to the base protocol may be necessary. This
includes addition of a Pseudo Wire AVP to identify the pseudo wire
being carried (with PPP identified as 0). In all cases, these will
follow the extensible models offered in the L2TP base protocol
design, with as much attention to backwards compatibility as
possible given the new requirements.

In addition to its broader scope, L2TPEXT has ongoing work to complete
from its inception as a tunneling protocol for PPP only. While RFC2661
will ultimately be made obsolete by a new L2TP base specification and
companion PPP over L2TP specification, documents based on RFC2661
which do not require this new degree of modularity will still be
published in the near term. These include:

- Identification of specific parameters and modes of IPsec in order to
aid interoperability when IPsec is used to secure L2TP traffic.

- An L2TP MIB for network management.

- An L2TP Differentiated Services Extension to negotiate DSCP
parameters to be set for packets associated with a given L2TP
tunnel, sessions within a tunnel, or L2TP control traffic which may
need differentiated QoS settings.

- Extensions to L2TP for additional or more robust control information
for informational or operational purposes as deemed necessary based
on operational experience. These include better transfer of L2TP PPP
LCP Information between tunnel endpoints when such state needs to be
shared, PPP Disconnect codes within L2TP control messages for better
debugging, and L2TP session information for enhanced logging,
billing, and error reporting.

- Standard methods for operation over such packet networks such as
Frame Relay and AAL5.

- L2TP defines a base encapsulation for operation in typical
environments for tunneling PPP at the time RFC2661 was being
developed. In cases where bandwidth cost is at a premium, the size
of the L2TP header becomes more significant. L2TP will define a
compressed version of the L2TP header for these environments that
takes advantage of the L2TP control plane to establish operational
parameters allowing removal of information from individual packets.

Goals and Milestones:

Done Submit L2TP over Frame Relay to IESG for consideration as a
Proposed Standard

Done Submit L2TP Security to IESG for consideration as a Proposed
Standard

Done Submit L2TP PPP Disconnect Information to IESG for
consideration as a Proposed Standard

Done Submit L2TP ATM extensions to IESG for consideration as a
Proposed Standard

Done Submit L2TP MIB to IESG for consideration as a Proposed
Standard

Done Submit L2TP Link Information to IESG for consideration as a
Proposed Standard

Done Submit L2TP Session Info to IESG for consideration as a
Proposed Standard

Done Submit L2TP Differentiated Services to IESG for consideration
as a Proposed Standard

Done Submit L2TP over AAL5 to IESG for consideration as a Proposed
Standard

Done Submit initial Internet-Draft of L2TP Base Specification

Done Submit initial Internet-Draft of PPP over L2TP

Done Submit final Internet-Draft of L2TPv3 Base Specification to
IESG

Mar 2004 Submit L2TP Header Compression to IESG for consideration as a
Proposed Standard

Apr 2004 Submit Internet-Draft of PPP over L2TPv3 to IESG

Done Submit Internet-Draft of HDLC over L2TPv3 to IESG

Done Submit Internet-Draft of Frame Relay over L2TPv3 to IESG

Done Submit L2VPN Extensions for L2TP to IESG

Done Submit Internet-Draft of Ethernet over L2TPv3 to IESG

Done WG Last Call on L2TP Failover

Done WG Last Call on L2TP Tunnel Switching

Mar 2005 WG Last Call on L2TP RADIUS and Infomsg Extensions

Internet-Drafts:

Posted Revised I-D Title <Filename>
------ ------- --------------------------------------------
Jul 2001 Jul 2007 <draft-ietf-l2tpext-l2tp-ppp-06.txt>
PPP Tunneling Using Layer Two Tunneling Protocol Version 3
(L2TPv3)

Aug 2001 Mar 2007 <draft-ietf-l2tpext-tunnel-switching-08.txt>
PPP over L2TP Tunnel Switching

Feb 2005 Mar 2007 <draft-ietf-l2tpext-tdm-03.txt>
Layer Two Tunneling Protocol - Setup of TDM Pseudowires

Oct 2005 Aug 2007 <draft-ietf-l2tpext-pwe3-ip-05.txt>
Signaling and Encapsulation for the Transport of IP over L2TPv3

Dec 2005 Mar 2007 <draft-ietf-l2tpext-proxy-authen-ext-eap-02.txt>
L2TP Proxy Authenticate Extensions for EAP

Jul 2006 May 2007 <draft-ietf-l2tpext-radius-ext-nas-port-01.txt>
RADIUS & L2TP Extended NAS-Port AVPs

Request For Comments:

RFC Stat Published Title
------- -- ----------- ------------------------------------
RFC3070 PS Feb 2001 Layer Two Tunneling Protocol (L2TP) over Frame Relay

RFC3145 PS Jul 2001 L2TP Disconnect Cause Information

RFC3193 PS Nov 2001 Securing L2TP using IPSEC

RFC3437 PS Jan 2002 Layer-Two Tunneling Protocol Extensions for PPP Link
Control Protocol Negotiation

RFC3301 PS Jun 2002 Layer Two Tunnelling Protocol : ATM access network
extensions

RFC3355 PS Sep 2002 L2TP Over AAL5

RFC3371 PS Sep 2002 Layer Two Tunneling Protocol 'L2TP' Management
Information Base

RFC3308 PS Nov 2002 L2TP IP Differentiated Services Extension

RFC3438BCP Dec 2002 L2TP IANA Considerations Update

RFC3573 PS Jul 2003 Signalling of Modem-On-Hold status in Layer 2 Tunneling
Protocol (L2TP)

RFC3817 I Jun 2004 L2TP Active Discovery Relay for PPPoE

RFC3931Standard Mar 2005 Layer Two Tunneling Protocol (Version 3)

RFC4045 E Apr 2005 Extensions to support efficient carrying of multicast
traffic in Layer-2 Tunneling Protocol (L2TP)

RFC4349 PS Feb 2006 High-Level Data Link Control (HDLC) Frames over Layer 2
Tunneling Protocol, Version 3 (L2TPv3)

RFC4454 PS May 2006 Asynchronous Transfer Mode (ATM) over Layer 2 Tunneling
Protocol Version 3 (L2TPv3)

RFC4591 PS Aug 2006 Frame Relay over Layer 2 Tunneling Protocol Version 3
(L2TPv3)

RFC4667 PS Sep 2006 Layer 2 Virtual Private Network (L2VPN) Extensions for
Layer 2 Tunneling Protocol (L2TP)

RFC4719 PS Nov 2006 Transport of Ethernet Frames over Layer 2 Tunneling
Protocol Version 3 (L2TPv3)

RFC4951 PS Aug 2007 Fail Over Extensions for Layer 2 Tunneling Protocol
(L2TP)