Subject: LCP Reconfiguration

From: Theimer Thomas <[email-masked]>
Date: Wed, 29 Apr 1998 14:31:54 +0200

Hi,

I have a question concerning the PPP state machine that is related to
LCP reconfiguration. The question is the following:

What happens when the link is in the open state, and an LCP
Configure-Request is received. RFC1661 says the following:

   The receipt of the LCP Configure-Request causes a return to the Link
   Establishment phase from the Network-Layer Protocol phase or
   Authentication phase.

Does that mean all network layer connections are terminated completely,
LCP options are renegotiated, and authentication is restarted ? That
implies also that the user has to logon again, and all network layer
protocols have to be restarted. The effect of this is similar to
terminating and restarting the link.

I just want to make sure that this interpretation is correct, and that
existing implementations actually behave accordingly.

Thanks for any comments,

Thomas Theimer

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From: James Carlson <[email-masked]>
Date: Wed, 29 Apr 1998 09:09:58 -0400

> terminating and restarting the link.

If a user was involved in logging in, then, yes, he must do that
again.  The link starts over.  (Of course, it's legal and reasonable
for the implementation to remember what was negotiated last time so
that it can avoid any Configure-Naks or Configure-Rejects, so it's not
always exactly the same as terminating and restarting the link.)

The control protocols for the network layer interfaces (such as IPCP)
do have to start over after authentication (if any), but this does not
mean that the network layer itself (such as IP) is restarted.

> existing implementations actually behave accordingly.

Note that it terminates the network layer connection.  This does *NOT*
imply that it should terminate any transport or application layer
sessions.  Some *very* common implementations of PPP, however, do
improperly kill off everything anyway.

For what it's worth, I've seen many implementations of PPP which fall
over and die if LCP Configure-Request is seen after LCP goes to Open
state.  It's hard to mandate that all implementations work right ...

-- 
James Carlson, Consulting S/W Engineer  <[email-masked]>
IronBridge Networks / 55 Hayden Avenue  71.246W    Vox:  +1 781 402 8032
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