Path: utzoo!utgpu!watserv1!watmath!att!linac!pacific.mps.ohio-state.edu!zaphod.mps.ohio-state.edu!julius.cs.uiuc.edu!zweig From: zweig@cs.uiuc.edu (Johnny Zweig) Newsgroups: comp.protocols.tcp-ip Subject: Re: IP Bandwidth limits (was Re: TCP window size restriction) Message-ID: <1991Jan11.181702.4546@julius.cs.uiuc.edu> Date: 11 Jan 91 18:17:02 GMT References: <9101091020.AA08870@techops.cray.com> <80719@sgi.sgi.com> Sender: news@julius.cs.uiuc.edu (USENet News) Reply-To: zweig@cs.uiuc.edu Organization: U of Illinois, Dept. of Computer Science, Systems Research Group Lines: 20 cjohnson@somni.wpd.sgi.com (Chris Johnson) writes: > Well, there is a data rate limit for TCP/IP, > but it isn't window size dependent. The > sixteen bit IP id field and the 16 bit max > packet length limit a particular connection > to 4GB/255 seconds or about 16MB/sec. For one thing, 255 seconds seems like a long TTL but whatever. There is _not_ a requirement for IP that ID numbers be unique over the time frame of one TTL (or 2*TTL or whatever). ID numbers are for fragment reassembly -- no fragments means no bandwidth limitation (so as long as I guaranteee my super-zippy net has an MTU of 65536 octets I am okay). I admit this is dangerous, in the sense that if some moron comes along and starts fragmenting in a bizarre way such that fragments aren't reassembled soon enough and their IDs get confused (a multi-megabyte LIFO buffer?) things will break, but I think it is important to keep in mind that just because IP was designed around very general interoperability requirements it is broken. -Johnny IP