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pelon
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Joined: 22 Aug 2024
Posts: 1
Location: Geneva, IL
PostPosted: Wed Aug 22, 2024 9:01 pm    Post subject: Telnet Reply with quote
Seeking advice on resolving slow telnet connections. We are using some Linux hand held pc that use telnet. Not able to use ssh on these units. We see significant delay or lag up to 1 minute or more before the units connect to our main Linux server. Anyone have any suggestion how we can resolve this issue.



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crouse
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Joined: 17 Apr 2024
Posts: 11831
Location: Iowa
PostPosted: Wed Aug 22, 2024 9:19 pm    Post subject: Reply with quote
http://aplawrence.com/SCOFAQ/FAQ_scotec4telnetslow.html
Quote:

Slow telnet or ftp connections are often caused by the server wanting to do a reverse DNS lookup to find out who is connecting. If you aren't running DNS, you can fix this just by listing all the machines in /etc/hosts.



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masinick
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Joined: 03 Apr 2024
Posts: 8595
Location: Concord, NH
PostPosted: Wed Aug 22, 2024 9:27 pm    Post subject: Re: Telnet Reply with quote
pelon wrote:
Seeking advice on resolving slow telnet connections. We are using some Linux hand held pc that use telnet. Not able to use ssh on these units. We see significant delay or lag up to 1 minute or more before the units connect to our main Linux server. Anyone have any suggestion how we can resolve this issue.


Do these units NOT HAVE ssh instead of telnet? The original telnet was the initial example of how to achieve a remote console terminal connection. Within the overall packet overhead of TCP/IP, telnet has only a moderate overhead. The problem is that it also has little, if any, adherence to or protection from security issues. SSH adds a layer of complexity but achieves a reasonable level of security. With trusted hosts, you can use authentication (I believe it is Kerberos based) that can be associated with communication between specific host systems. You can't do that with telnet. The old rlogin and rsh commands could automatically connect, but they had no Kerberos authentication either so they were nearly as bad as telnet in this regard.

Defining local hosts is one way to overcome performance issues, with the tradeoff of more local host management.



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