Subject: IPCP within MP?

From: Archie Cobbs <[email-masked]>
Date: Fri, 28 Apr 2000 14:25:49 -0700 (PDT)

I have encountered some equipment that seems to have a bug,
and I just wanted to confirm with the list that it is in fact
a bug, or else what my misunderstanding is..

What happens is this:

  1.  A 2 B-channel ISDN multi-link PPP connection is made.

  2.  Both links reach the LCP NETWORK phase; Link #1 comes
      up first, then link #2.

  3.  The peer sends me an IPCP Configure-Request as a single,
      complete multilink encapsulated packet on link #1.

  3.  My side attempts to send an IPCP Configure-Request that's
      split into two parts and sent as two multi-link fragments
      over the two links.

  4.  The remote side responds with an LCP Protocol-Reject
      of protocol 0x003d (the multilink protocol) on link #2,
      and ignores my IPCP Configure-Request. The protocol
      reject contains enough of the packet to show that it's
      rejecting one of the IPCP Configure-Request MP fragments.

  5.  Because the peer never hears my IPCP Configure-Request's
      the connection never succeeds.

  6.  If I alter my code to not fragment my IPCP Configure-Request
      but send it as a complete packet, things seem to work fine.

I'd be interested to hear if anyone else has encountered this
behavior... or if you are the vendor and know about this problem.

Thanks,
-Archie

___________________________________________________________________________
Archie Cobbs   *   Whistle Communications, Inc.  *   http://www.whistle.com

---

From: James Carlson <[email-masked]>
Date: Fri, 28 Apr 2000 17:37:05 -0400 (EDT)

>   2.  Both links reach the LCP NETWORK phase; Link #1 comes

I assume that the MP MRRU is set on both links, MP
Endpoint-Discriminators and Short-Sequence-Number options match, and
MRUs are the same.

>       split into two parts and sent as two multi-link fragments

No problem with that.  (I don't think I've seen an implementation yet
that does this, though ...)

>       rejecting one of the IPCP Configure-Request MP fragments.

Assuming that the second link is actually configured to run MP, that's
a rather horrible bug.

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