Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!samsung!uunet!philmtl!altitude!pascal
From: pascal@altitude.UUCP (Pascal Gosselin)
Newsgroups: comp.protocols.appletalk
Subject: Re: Routers that can support > 2 Localtalk connections?
Keywords: ROUTERS LOCALTALK ETHERTALK SCSI SPEED COLLISIONS
Message-ID: <1990Mar15.001402.20929@altitude.UUCP>
Date: 15 Mar 90 00:14:02 GMT
References: <1990Mar10.160033.16149@altitude.UUCP> <663@wcc.oz>
Organization: None
Lines: 68

tom@wcc.oz (Tom Evans) writes:

>In article <1990Mar10.160033.16149@altitude.UUCP>, pascal@altitude.UUCP (Pascal Gosselin) writes:

>(Summary of how a class of kids on 18 Macs can kill a network by all
>launching stuff at once)
> 
>>      I have proposed (and will be testing Tuesday) installing Liaison 2.0
>> on the SE/30 and thus DOUBLE the throughput of the network (The SE/30's
>> horsepower is such that the routing necessary on one of the Atalk Zones
>> to access the server will entail a negligeable delay, I've tested this   
>> before with Liaison on Ethernet servers doubling as Localtalk<->Ethertalk
>> routers.

>Nope. Your test should show little improvement, and if it does then
>not for the reason you expect. LocalTalk in a Mac is CPU-INTENSIVE.
>The CPU has to manually send a byte out the LocalTalk port once every
>34uS or so. While it is doing this it CAN'T DO ANYTHING ELSE,
>especially not send data out another LocalTalk port. Thus the total
>throughput from a Mac running two LocalTalk ports is the same as from
>the same Mac running one Localtalk port.

    I have run the test, and the throughput IS improved.  I DO AGREE that
killing the network with 18 launches is torture, but this is no reason for
having 0% efficiency on the network.  I have contacted the person reponsible
for the MacJanet server software at Watcom, he's going to look into the problem.
You see, this problem (absolute total network hangup with MacJanet server) seems
to happen with a VERY specific hardware/software combination.  We have other
schools running it (and they run it hard at the University of Waterloo) (the
MacJanet software) and they have not reported similar problems.

    Basically, I found that having one Mac Plus on both zones lauching
Mac Draw II 1.1 at the same time dropped the load time from 55secs to 40secs.
The speed is obviously not doubled, as floppy accesses on the Mac Pluses
account for quite a bit of the required load time.  As for implying that an
SE/30 cannot handle two localtalk ports at 230.4kbps, I do not have the
technical knowledge to challenge you on this claim.  However, it seems ODD
that a lowly Mac Plus is capable of handling 230.4kps while the SE/30, with
5 times the processing horsepower, could not handle twice as many interrupts???
Does this imply that an SE/30 is using 99% of it's CPU ressources, like a
Mac Plus might seemingly does, to handle a single Localtalk port????

    I also think that splitting the network in two (as I have tried) might
help ease the latency problem that has everyone retrying for what they
think are packets that never got there??? (i.e. 9 macs instead of 18 per
network should help, right?)

    Liaison 2.0 also has a setting for the amount of CPU that it dedicates
for the bridging functions, enabling this feature seems to give the best
performance when a dedicated server is used as a bridge (since menu/mouse
responsiveness is not a factor).  As for the reduced CPU time given to the
application (i.e. AppleShare), it's no big deal as only a few milliseconds
of hard disk transfer time translates into quite a few seconds of Localtalk
transfer.

    I have NEVER seen an AppleShare file server die from excessive network
traffic.  I will be glad to post a few "unofficial" benchmarks once the
bugs are ironed out on the server (BTW, Liaison is NOT killing the server,
I merely installed it to see if it would help out). 

    It is unfortunate that Localtalk is so slow and that the speedup solutions
seem as expensive as local hard disks.
   
-- 
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| Pascal Gosselin          |   philmtl!altitude!pascal@uunet.uu.net  |
| Computer Connection Inc. |     (514) 674-1514     CIS: 72757,1570  |
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