Path: utzoo!attcan!uunet!husc6!spdcc!eli
From: eli@spdcc.COM (Steve Elias)
Newsgroups: comp.dcom.lans
Subject: Re: 802.* a cornucopia ?
Message-ID: <1715@spdcc.COM>
Date: 23 Aug 88 16:52:55 GMT
References: <10400002@osiris.cso.uiuc.edu> <4942@cos.com> <1988Aug15.170727.24258@utzoo.uucp> <1677@spdcc.COM> <1988Aug18.165532.26169@utzo
Reply-To: eli@spdcc.COM (Steve Elias)
Organization: yes
Lines: 41

In <1988Aug22.211807.10280@utzoo.uucp> henry@utzoo.uucp (Henry Spencer) writes:
>In article <1698@spdcc.COM> eli@spdcc.COM (Steve Elias) writes:
>>	802.3 won't provide a deterministic network access time if
>>	it is under heavy load, as you say.  this is a key feature
>>	of 802.4, i think.  not so important for campus type 
>>	networks, but essential for factory & industrial networks.
>
>But 802.4 cannot provide a (very) deterministic network access time either,
>because its token can get lost.  I don't know how many times it is necessary
>to say this:  there is *no* general-purpose local network (that I know of,
>anyway) that is free from pathological misbehavior under stress.  The kind
>of misbehavior, and the kind of stress, differ from one network to another,
>but there's no royal road to networking.

	no royalty intended...

	i'm not saying that there is any perfect or optimal network
	for all situations.  it seems to me that different networks
	are going to require different optimizations and different
	reactions to stress.  one idea of 802.4 is to be have a
	"more" deterministic network access time, apparently.  i 
	really don't know if this works in practice, though i suppose
	it probably does, since there are factory networks using .4.

	the point being that there is a need for a few different
	LAN standards.  whether having both a token bus and a 
	token ring standard is useless, i'm not qualified to say.
	but as i learn more about the 802 cornucopia, i'm beginning
	to see the diffent slants of the two approaches (.4 and .5).
	perhaps having both specs is just another compromise.
	did IBM have something to do with this?

	does anyone have any idea as to why .5 implementations
	started at 1 or 4 Mbits/sec, and .4 is already chugging along
	at 10 Mbits/sec?  and when is the 16 Mbits/sec token ring
	chipset supposedly going to be available.