Current Meeting Report

2.4.6 UniDirectional Link Routing (udlr)

NOTE: This charter is a snapshot of the 53rd IETF Meeting in Minneapolis, MN USA. It may now be out-of-date. Last Modified: 11-Feb-02
Emmanuel Duros <>
Hidetaka Izumiyama <>
Routing Area Director(s):
Randy Bush <>
Bill Fenner <>
Routing Area Advisor:
Bill Fenner <>
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Description of Working Group:
Note: An alternate site for UDLR's files is:

The UDLR working group issued the RFC 3077 in March 2001. This RFC describes a link-layer tunneling mechanism (LLTM) for supporting unidirectional links (UDL) in the Internet.

During the design of this mechanism by the UDLR working group, several implementations evolved. These implementations are fully interoperable and are currently being used in several operational environments.

As of the publication of RFC 3077, the working group has decided to further their work by issuing the following objectives:

1. Produce informational rfc's that describe in detail the requirements of example case study scenarios as listed below. Note that these scenarios relate to field experiments that are being undertaken based on the LLTM mechanism:

a) configuration of multicast routing protocols over a unidirectional link

b) configuration of unicast routing protocols over a unidirectional link

c) securing operation of a UDLR network

2. Identify security holes

3. Push the current document (RFC 3077) status to Draft Standard.

Goals and Milestones:
Dec 01   Submit I-D on the configuration of multicast routing protocols over a UDL
Dec 01   Submit I-D on the configuration of unicast routing protocols over a UDL
Dec 01   Submit I-D on securing operation of a UDLR network
Mar 02   Submit the Link Layer Tunneling Mechanism to the IESG for consideration as a Draft Standard
Jul 02   Submit Internet-drafts as Informational RFCs
Request For Comments:
RFC3077PSA Link Layer Tunneling Mechanism for Unidirectional Links

Current Meeting Report

Here follows the minutes of the UDLR WG, thanks to Celine and Izu for
taking them...

Could all speakers send me there presentations in pdf format ? Thanks.


19th of March, 14:15-15:15 at Salon B

* WG activities update 5 min

* I-D update : draft-ietf-udlr-dvmrp-conf-02.txt
by Celine Benassy (Alcatel) 10 min

Question from E. Duros: how NACK are sent ? In multicast
-> to clarify this point on the future version of the draft

* New I-D : draft-ietf-udlr-multicast-issue-00.txt
by Jun Takei(JSAT) 15 min

Bill : usage of unicast routing table for RPF is implementation issue not PIM spec.
Cisco routers could use static multicast routing and do not always use the same unicast routing table.

Someone: In network using MPLS you do not need to have separated tables even if each route is composed of two unidirectional connections: the RPF interface is the incoming interface of hello messages (PIM-SM hello messages). To send a message to the sender of the Hello message an other interface (the ouput interface) is used.

E. Duros: in your network architecture where are the hosts ?
on the broadcast link between routers or behind the last router ?

-> It is possible to have both hosts on the broadcast link and behind the last router.

* Discussion about general document 10 min

Proposal to produce a general document that would describe which protocols are known to operate over UDLR. It would show the limitations of each protocol in the network architecture, e.g. using satellite link. However this document does not intend to solve each protocol's issue, it is not the aim of the WG.

We had a rough consensus from the WG to move forward on this action.

* Moving RFC status to draft standard 5 min

Review IETF process(RFC2026)

Bill : need to write applicable senario (applicable statements)
Bill will provide some example.


None received.