Xref: utzoo comp.protocols.tcp-ip:14073 comp.dcom.lans:6717
Path: utzoo!attcan!uunet!bellcore!envy!karn
From: karn@envy.bellcore.com (Phil R. Karn)
Newsgroups: comp.protocols.tcp-ip,comp.dcom.lans
Subject: Re: IP down scaling (linear or what) ?
Keywords: ip scaling performance
Message-ID: <1990Dec10.181110@envy.bellcore.com>
Date: 10 Dec 90 23:11:10 GMT
References: <58@nixeid.UUCP> <1990Dec7.104135.12@ux1.cso.uiuc.edu>
Sender: usenet@bellcore.bellcore.com (Poster of News)
Reply-To: karn@thumper.bellcore.com
Organization: Packet Communications Research Group (Bellcore)
Lines: 23

In article <1990Dec7.104135.12@ux1.cso.uiuc.edu>, krol@ux1.cso.uiuc.edu
(Ed Krol) writes:
|> Just remember that as the link speed decreases the IP (and
presumably)
|> TCP headers take up a greater percentage of the available bandwidth.
|> Leaving less room for real data.  (At a link speed of about 500 baud
|> you have just enough bandwidth to send TCP IP headers and do HDLC
|> bitstuffing - sorry no room for data)

Nonsense. The overhead of a TCP/IP link is entirely determined by the
amount of data in each packet vs the size of the headers. The link
speeds don't enter into it at all.

When the application queues many small packets for transmission, a TCP
that implements the Nagle algorithm (now a required part of the
standard) actually *reduces* the header overhead automatically as the
link speed decreases. Rather than launch multiple small packets into a
narrow pipe, a Nagle TCP bunches them together by delaying
transmission of new data when there is already unacknowledged data in
the pipe; multiple packets are launched only when they are
maximum-sized (i.e., have minimum header overhead).

Phil