Layer Two Tunneling Protocol Extensions (l2tpext) ------------------------------------------------- Charter Last Modified: 2009-06-25 Current Status: Active Working Group Chair(s): Ignacio Goyret Carlos Pignataro Internet Area Director(s): Ralph Droms Jari Arkko Internet Area Advisor: Ralph Droms Mailing Lists: General Discussion:l2tpext@ietf.org To Subscribe: l2tpext-request@ietf.org In Body: subscribe 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 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 2008 WG Last Call on L2TP Proxy Authenticate Extensions for EAP Mar 2008 Submit Internet-Draft of PPP over L2TPv3 to IESG Mar 2008 WG Last Call on L2TP Tunnel Switching Jun 2008 WG Last Call on L2TP RADIUS and Infomsg Extensions Jun 2008 WG Last Call on IP over L2TPv3 Done WG Last Call on TDM over L2TPv3 Internet-Drafts: Posted Revised I-D Title ------ ------- -------------------------------------------- Feb 2005 Apr 2009 Layer Two Tunneling Protocol version 3 - Setup of Time-Division Multiplexing (TDM) Pseudowires Oct 2008 Jul 2009 L2TPv3 Extended Circuit Status Values 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)