Path: utzoo!attcan!uunet!decwrl!ucbvax!CHANCE.MITRE.ORG!mckee
From: mckee@CHANCE.MITRE.ORG (H. Craig McKee)
Newsgroups: comp.protocols.tcp-ip
Subject: Re: Maintainability of TELNET Sessions Over Marginal Circuits
Message-ID: <9010021321.AA13109@chance.mitre.org>
Date: 2 Oct 90 13:21:09 GMT
Sender: daemon@ucbvax.BERKELEY.EDU
Organization: The Internet
Lines: 25

>When they brought up the first LAN ... the link was of poorer quality 
>than they had thought and continually looses [crypto] synch ....

Is the link protocol synchronous (eg, HDLC) or asynchronous (start/
stop bits)?  My experience with synchronous links is that a crypto like
the KG-84 rarely looses synch (because modem clock recovery circuits are
generally very good).  For some cryptos there is a mode of operation
called CTAC that is self-synchronizing; it does not require loss-of-
synch logic in another box.  The site can get expert advice from
their cryptologic support center or the National Security Agency.

  >2.  How robust is IP in dealing with corrupted data streams when crypto
  >    synch is lost in the header?  In the body?
  >3.  How robust is TCP in dealing with corrupted data streams?

Corrupted data will be detected and discarded by error detection 
logic at the link, IP, and TCP layers.

  >4.  Would fudging IP, TCP, or TELNET timers by a "crypto resync constant"
  >    alleviate problems?

Give it a try; it's not a good hack, but I've done some bizarre things 
when trying to get a circuit up.  

Regards - Craig