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тАО06-20-2008 12:56 AM
тАО06-20-2008 12:56 AM
We are now using telnet to connect our users to the OpenVMS nodes. A change will be made to use SSH.
Anyone who knows what the impact is on resource usage. We have over 1000 users.
If have searched the internet but this is very hard to find.
Greetings,
Piet
Solved! Go to Solution.
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тАО06-20-2008 01:23 AM
тАО06-20-2008 01:23 AM
Re: SSH and performance
Purely Personal Opinion
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тАО06-20-2008 10:23 AM
тАО06-20-2008 10:23 AM
Re: SSH and performance
And yes, I am aware of steps I can take to alleviate these, but there are politics and red tape and other businesses/groups involved, etc, etc. things don't get easily done.
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тАО06-22-2008 07:02 PM
тАО06-22-2008 07:02 PM
SolutionIn that environment, each login takes up two process slots: one to do the SSH protocol stuff (including encryption) and one for the actual user session. So at the very least you're going to consume around twice as many process slots as you have now, and some extra RAM (around 200-800 pages per session).
In addition, CPU usage will increase because each SSH session must encrypt outgoing traffic (screen updates) and decrypt incoming traffic (keystrokes). How much additional load this is will depend on how active your users are.
Regards,
Jeremy Begg
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тАО06-25-2008 12:41 PM
тАО06-25-2008 12:41 PM
Re: SSH and performance
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тАО06-25-2008 02:11 PM
тАО06-25-2008 02:11 PM
Re: SSH and performance
> that limits SSH sessions. I forget its
> name.
I use the TCPIP service limit:
ALP $ tcpip show service /full ssh
Service: SSH
State: Enabled
Port: 22 Protocol: TCP Address: 0.0.0.0
Inactivity: 5 User_name: TCPIP$SSH Process: TCPIP$SSH
Limit: 64 Active: 0 Peak: 64
[...]
The SSH attacks on my system always end like
this one:
%%%%%%%%%%% OPCOM 25-JUN-2008 08:56:05.89 %%%%%%%%%%%
Message from user INTERnet on ALP
INTERnet ACP SSH Reject Request - service limit - from Host: 220.92.203.126 Port
: 33015
Of course, if you have more (than roughly
zero) real users, you may need to think a bit
harder about the best limit value.
The usual attack program seems to give up at
the first rejection, and the dead processes
die off in a little while, so any service
denial is usually fairly short.
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тАО06-30-2008 06:24 AM
тАО06-30-2008 06:24 AM
Re: SSH and performance
1) ucx show dev will show 2 connections. So you could run into the maximum bg device limit (also channelnt ?).
2) if users must copy big files (e.g. db dumps) using ssh this will give a heavy load because of the encryption. Consider lowering the encryption number of bits (I didn't test the impact but in zipiing large files it had serious impact lowering /level).
3) 1 user doing type *.log.* caused cpu rate of 4% for encryption only (GS160 with multinet).
4) Any X clients not supporting encryption ? Then use putty.
Wim
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тАО06-30-2008 11:58 AM
тАО06-30-2008 11:58 AM
Re: SSH and performance
What was the effective "baud rate" of this "terminal". If it was on a 9600 bps connetion, then that would be significant. But if on a telnet session from a PC terminal emulator, the encryption data rate would be more significant.
The point being that the type command will normally be i/o bound by the output device, and therefore the speed of the output device will have a large effect on the resources used by SSH encryption.
Jon
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тАО07-01-2008 12:09 AM
тАО07-01-2008 12:09 AM
Re: SSH and performance
And we have several times a year someone running a program with "debugging messages" that have about the same effect.
Wim