Subject: Clarification regarding encryption and compression in PPP

From: Arul J P <[email-masked]>
Date: Mon, 30 Oct 2000 10:32:49 +0530

Hi,

   Can LCP echo request packets or CHAP challenge packets be
encrypted or compressed.

regards
Arul.

---

From: James Carlson <[email-masked]>
Date: Mon, 30 Oct 2000 06:41:48 -0500 (EST)

>    Can LCP echo request packets or CHAP challenge packets be

That's up to the encryption or compression algorithm in use.  ECP and
CCP define the negotiation method; they don't determine which
protocols are actually passed through the encoding method chosen.

I would expect normal implementations to encrypt at least the CHAP
Challenge and possibly also LCP Echo-Request, but compress neither.
(DESE-bis [RFC 2419] prohibits encryption of LCP.  It wouldn't
surprise me to find that in some implementations, LCP packets with
code numbers above 4 are encrypted anyway.)

The underlying rule is that compression of infrequently used things,
such as NCP negotiation messages, is unlikely to be helpful and could,
if errors occur, be harmful (at least to accurate logging).
Encryption, once negotiated, is mandatory.  They only time you don't
encrypt is when you're restarting the link.

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