Xref: utzoo comp.protocols.tcp-ip:2929 comp.protocols.iso:64
Path: utzoo!mnetor!uunet!lll-winken!lll-tis!ames!ucsd!rutgers!bellcore!faline!thumper!karn
From: karn@thumper.bellcore.com (Phil R. Karn)
Newsgroups: comp.protocols.tcp-ip,comp.protocols.iso
Subject: Re: SLIP working group?
Message-ID: <1016@thumper.bellcore.com>
Date: 30 Mar 88 20:55:26 GMT
References: <1966@hou2d.UUCP>
Organization: Bell Communications Research, Inc
Lines: 26
Summary: too little, too late

The framing technique you describe is EXACTLY the same as SLIP, with one
important difference -- the specific values of the "escape" and "frame
end" characters are different. Why? Is gratuitous incompatibility with
de-facto standards a prerequisite for ISO approval?

I distinguish between the framing technique used by SLIP and the format
of the information carried in a frame. There's nothing about SLIP
framing that says you can't add a link-level CRC or checksum if you
wish. It just hasn't been necessary, as there are already checksums at
the IP and TCP layers.  The error rate of a typical dialup link (if it
works at all) is low enough that the extra software processing required
to recompute a checksum over an entire packet at each hop is hard to
justify. I keep a nailed-up 9600 bps V.32 modem link between work and
home. In the 6 days since it was last rebooted, my machine at home has
received 13,186 packets over the serial link. Of these, however, only 6
had IP header checksum errors and 8 contained TCP header checksum
errors. I have also used SLIP heavily elsewhere, but I have NEVER seen a
file corrupted by the failure of the TCP checksum to catch an error.

The propensity of the ISORMites to reinvent the wheel (with seemingly
deliberately incompatible lug-nut threads) never ceases to amaze me.
Considering the popularity of SLIP, your time would be much better spent
making incremental, desirable improvements (e.g., logins and passwords
for switched environments) instead of devising totally new and
gratuitously different protocols to do what is already being done.

Phil