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TCPIP telnet sesions slow

 
Phil Lawson
Advisor

TCPIP telnet sesions slow

I've got a cluster of 2 4100's, 2gb of memory each. VMS7.3-2, Telnet terminal sessions are SLOW. Sometimes response time is as slow as 60 seconds. Network all checks out ok, but a sniffer says the Alpha's are not responding. Looks like the Alpha's have plenty of resources, no heavy disk IO, plenty of memory CPU's free. Is there any tuning that can be done at the tcp level? Not sure if this should be in the network section, but I'm more of a systems guy so I thought I'd start here. Thanks in advance for any help anyone can provide.

-Phil

8 REPLIES
David B Sneddon
Honored Contributor

Re: TCPIP telnet sesions slow

Phil,

Is it the initial connection that takes up to
60 seconds or are you seeing response delays of
that magnitude once the connection is established?
What version of TCPIP services do you have?
How are the boxes connected to the network?
Are you seeing any other network problems?

Dave
Ian Miller.
Honored Contributor

Re: TCPIP telnet sesions slow

Is the slow response only on the initial connection or is it also seen on established connections?
Slow responses on initial connection are sometimes due to delays in the DNS lookup of the IP addreess of the incoming connection.
____________________
Purely Personal Opinion
Antoniov.
Honored Contributor

Re: TCPIP telnet sesions slow

Phil,
as posted above, it's very important when your connection is slow.
May be interesting kwnow if just telnet is slow.
For example,
- all services are continously slow: mey be network card synchronizing with switch;
- al services are slow when starting, then they work fine: it a DNS trouble;
- telnet is slow while other services work fine: some configuration of telnet is bad.

Antonio Vigliotti
Antonio Maria Vigliotti
Phil Lawson
Advisor

Re: TCPIP telnet sesions slow

It's not the initial connection, that seems to go ok, but once connected response is slow. This is running TCPIP 5.4 ECO 2. Boxes are connectted to the network with GB ethernet. Telnet is the only thing being used on these boxes, no FTP, or HTTP or anything like that. I've dealt with Process Software in the past, and they had paramaters that needed to be tuned for large amounts of users. I don't see anything like that in the HP software.
comarow
Trusted Contributor

Re: TCPIP telnet sesions slow

First, with tcpip 7 you don't need to tune it. But please stay current with ECOs.
TCPIP 6 with ECO 5.

Is the system slow or just the telnet users.

What does monitor system show?

Is it slow from the console?

In otherwords, is it a network problem.

Let's isolate that first.
If you do a
Anal/system
show lan/count
there are many pages. Look for failures or errors. For example alignment errors or receive errors.

Bob
Bob
Volker Halle
Honored Contributor

Re: TCPIP telnet sesions slow

Phil,

in a situation like this, I would use CTRL-T as a first check, when a session seems to 'hang'. Control-T is handled in the terminal driver, so not much overhead/CPU involved and no disk-IOs. You would expect an immediate response from CTRL-T.

If CTRL-T does not respond immediately, try it on the console. It may be a system, not a network problem. If it's o.k. on the console - while the TELNET session 'hangs', try PING next (from your TELNET client to the node you're logged into).

Does this 'hang' affect ALL users on the same or both nodes of the cluster at the SAME time ? Try running 2 TELNET sessions from your TELNET client and check whether they hang at the same time.

Did you check OPERATOR.LOG ?

Volker.
Willem Grooters
Honored Contributor

Re: TCPIP telnet sesions slow

Sometimes it can be caused by a mismatch in speed between the Alpha NICs and the switch. It is known that in certain cases auto-negotiation may cause trouble.

Another thing you may look at if the telnet clients (PC?) are on a different subnet: I have seen this trouble when the Alpha had an error in the routing tables: Check the routing tables and defualt route on that machine:
$ TCPIP SHOW ROUTE/FULL
$ TCPIP netstat -r
$ TCPIP netstat -rs gives you statistics
Willem Grooters
OpenVMS Developer & System Manager
Antoniov.
Honored Contributor

Re: TCPIP telnet sesions slow

Like Willem I suspect some trouble between NIC and switch.
At first glance you can evaluate NIC parameters:
$ MC LANCP SHOW DEV /CHAR
You can see operational values (half duplex vs full duplex, NIC speed).
You can also read error counters
$ MC LANCP SHOW DEV /COUNT

Antonio Vigliotti
Antonio Maria Vigliotti