Path: utzoo!mnetor!uunet!lll-winken!lll-tis!ames!pasteur!ucbvax!UCSD.EDU!karn
From: karn@UCSD.EDU (Phil Karn)
Newsgroups: comp.protocols.tcp-ip
Subject: Re: Acking out-of-order packets?
Message-ID: <8803031615.AA28777@ucsd.edu>
Date: 3 Mar 88 16:15:54 GMT
Sender: daemon@ucbvax.BERKELEY.EDU
Organization: The Internet
Lines: 11

Nothing really "depends" on those do-nothing ACKs, in the sense that the
protocol still operates correctly even if they are lost.

I should probably let Van describe his own technique, but basically it
involves interpreting a flurry of do-nothing ACKs as an indication that
an early packet was lost. This triggers a retransmission before the timer
would ordinarily expire and do it.

This appears to be a big performance win over networks with large 
bandwidth*delay products (e.g., the Wideband net).

Phil