A105@UWOCC1.BITNET (Brent Sterner) (12/02/86)
A quick puzzle. I've connected our only DECserver-200, and I've noticed the output from some programs is very jerky (at 9600 baud). I've left most of the server parameters alone. Reducing the circuit timer from 80 to 40 ms does not help. The server is connected via DELNI to what must be the least-loaded ethernet cable in the world. Error counts are very low over a period of several weeks, so there is apparently no physical reason for this. There is no lost data as far as I can see. Connections made directly to the VAX (8600) do not show this symptom. Even SET HOST 0 several times, and running through several layers of DECnet doesn't produce the sort of output I'm seeing, so I'm reasonably sure it is LAT related. Any suggestions will be persued. Thanks as usual. Brent Sterner Computing & Communications Services Natural Sciences Building The University of Western Ontario London, Ontario, Canada N6A 5B7 Telephone (519)661-2151 x6036 Network <A105@UWOCC1.BITNET>
"Ken_Garnett.AYLRX"@XEROX.COM.UUCP (12/05/86)
The jerky output you are getting is probably due (as you say) to LAT11, the set host 0 will not have the same effect on the 8600 as this does not use LAT11 but the full function decnet code, I have heard other users have the same problem with both terminal access through LAT11 and X25, these protocols seem to be fine for moving large chunks of data around but not for terminal traffic where the vax can generate packets for the terminal with a very small amount of data contained in the packet (for full duplex, a packet containing one byte of user data is not unusual) this means the server has to do a phenominal amount of work dis-assembling the packets as they arrive, also the host vax is doing far more work than would be desirable. I have heard that as LAT11 is a subset of decnet that the LAT packets are treated as second rate by the host decnet software, but I have no proof of this. CURE :- sorry I know of none ! (maybe someone closer to DEC can provide an answer) Regards Ken Garnett Advanced Technology Manager, Rank Xerox, Aylesbury, UK
LEICHTER-JERRY@YALE.ARPA.UUCP (12/07/86)
A quick puzzle. I've connected our only DECserver-200, and I've
noticed the output from some programs is very jerky (at 9600 baud).
I've left most of the server parameters alone. Reducing the circuit
timer from 80 to 40 ms does not help. The server is connected via
DELNI to what must be the least-loaded ethernet cable in the world.
Error counts are very low over a period of several weeks, so there
is apparently no physical reason for this. There is no lost data as
far as I can see.
...
I believe SOME "jerkiness" is normal - the LAT protocol IS a packetizing
protocol, and the human eye seems to be pretty sensitive to this kind of
effect. I've been using LAT lines on and off for long enough now that I
don't notice any more. As I recall, you stop noticing after a week or so.
(Further, when I use a LAT line after several weeks of NOT using one, I
don't notice the effect either.)
The actual effect on throughput of the "jerkiness" is minimal. Also, loading
on the Ethernet will have no effect on this phenomenon - it won't get any
worse until you are bringing your Ethernet to the point of collapse.
My advice: Give it a week of steady use. If it still bothers you, check out
the system more closely, as there really MAY be something wrong.
BTW, note that decreasing the circuit timer value as you did will increase
loading on the host - it will just about double it. Probably not worth
worrying about, but worth being aware of.
-- Jerry
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