Subject: L2TP link extensions

From: "S.Rajesh Kumar" <[email-masked]>
Date: Tue, 6 Jun 2000 14:34:07 -0700 (PDT)

The "L2TP link extensions (draft-ietf-l2tpext-link-00.txt) defines
AVPs for the LAC to influence LCP parameters negotiated by the LNS.
Pardon my ignorance, but - What is the use of this? If the LAC has
the parameters that it wants negotiated on the PPP session, the LAC
could do proxy-LCP to ensure that these are used? Why is it necessary
to make the LNS negotiate these parameters?

Also - why should the LAC influence the parameters negotiated by the
LNS?

Thanks in advance for the clarification
Rajesh

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From: James Carlson <[email-masked]>
Date: Tue, 6 Jun 2000 20:00:12 -0400 (EDT)

S.Rajesh Kumar writes:
> could do proxy-LCP to ensure that these are used?

Right; if the LAC is filtering the LCP options and mediating the
negotiation, then there's no reason at all for the SLI.

> Why is it necessary

There are some who believe that the LAC should pass all LCP frames
unmolested and that the LNS should therefore have intimate
understanding of (or at least tolerance for) the vagaries of the link
types that all of the LACs support.  But that's just my reading.  ;-}

> Also - why should the LAC influence the parameters negotiated by the

If the LNS is doing LCP on behalf of the LAC, then it will need this
information to set link-related parameters correctly.

-- 
James Carlson                                  <[email-masked]>
"PPP Design and Debugging" --- http://people.ne.mediaone.net/carlson/ppp

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From: "W. Mark Townsley" <[email-masked]>
Date: Tue, 06 Jun 2000 21:01:51 -0400

> negotiation, then there's no reason at all for the SLI.

Big "if"

> types that all of the LACs support.  But that's just my reading.  ;-}

It is reality as well. It was an original design constraint that the LAC
not need to be cognizant of contents of the packets it is tunneling once
the L2TP session is up.

> information to set link-related parameters correctly.

It *could* need this information in some cases, so link-info exists to
identify a standard and extensible method for packaging this information
(rather than in individual AVPs, as is done with the current ACCM format
in the SLI).