Subject: Handling LCP Code-Reject

From: [email-masked]
Date: Tue, 23 May 2000 13:51:13 -0400

I recently got a problem report on my PPP implementation because it
terminates the connection after receiving a code-reject for LCP code 11,
Discard Request.  I went back to RFC 1661 and re-read the section on
code-reject on page 34. It states (in part) "Upon reception of the
Code-Reject of a code which is fundamental to this version of the
protocol, the implementation SHOULD report the problem and drop the
connection, since it is unlikely that the situation can be rectified
automatically".

In hindsight, it's clear to me that I did not really think hard enough
about what I was doing when I wrote the code that handles a Code-Reject
from the peer. Certainly I wouldn't try to argue that support of Discard
Request is "fundamental" to my implementation. So why am I dropping the
connection?

But on the other hand, where should the line be drawn? Before I jump in to
tinker with this I thought it was worth posting a note to the list to see
if I could get feedback about what other folks implementations deal with
this issue. Where do you draw the line on what is a fundamental code?
Discard-Request and below? Protocol-Reject and below? Or some other
boundary?

Any feedback appreciated. Thanks,

-john martz, 8-852-5539,  [email-masked]
IBM AS/400 TCP/IP PPP development (and stuff)

---

From: James Carlson <[email-masked]>
Date: Tue, 23 May 2000 13:59:43 -0400 (EDT)

> Discard-Request and below? Protocol-Reject and below? Or some other

The usual rule is >= Configure-Request and <= Protocol-Reject -- those
codes cannot be rejected.  (Don't forget that 0 is the
Vendor-Extension code number.)  The others are fair game.

(For what it's worth, many implementations have many unsubtle bugs in
Code-Reject handling; partly because of the old RFCs, and partly just
because.)

-- 
James Carlson, Internet Engineering       <[email-masked]>
SUN Microsystems / 1 Network Drive         71.234W   Vox +1 781 442 2084
MS UBUR02-212 / Burlington MA 01803-2757   42.497N   Fax +1 781 442 1677
"PPP Design and Debugging" --- http://people.ne.mediaone.net/carlson/ppp