Subject: l2tp m bit semantics

From: Juha Heinanen <[email-masked]>
Date: Wed, 8 Sep 1999 12:39:40 +0300 (EEST)

what is the scope of the word "recognize" in this statement of the l2tp
spec?

Mandatory (M) bit: Controls the behavior required of an
implementation which receives an AVP which it does not recognize.

for example, if an lns receives an SCCRQ request that has the Result
Code AVP in it, should it consider the Result Code AVP as unrecognized
within the SCCRQ message and thus silently ignore it or should it
consider the message errorneous and reject the whole request?

i'm asking on behalf of who major vendors that interprete the statement
differently.

-- juha

---

From: James Carlson <[email-masked]>
Date: 08 Sep 1999 17:37:02 -0400

> consider the message errorneous and reject the whole request?

One would think that AVPs defined by the base document (RFC 2661) are
fully defined by that document.  In other words, if Result Code
appears outside of the context of CDN or StopCCN, then it's a protocol
error, not an "unrecognized" AVP.

The implication would be that the only "unrecognized" AVPs are those
that an implementation doesn't implement in any context.  (Presumably
because they're defined outside of RFC 2661.)

I agree, though, with the idea that the "mandatory" bit is an
incompletely specified idea.  A better implementation of the same idea
is in RFC 1771 ...

-- 
James Carlson, System Architect                     <[email-masked]>
IronBridge Networks / 55 Hayden Avenue   71.246W   Vox:  +1 781 372 8132
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"PPP Design and Debugging" --- http://people.ne.mediaone.net/carlson/ppp