[j-nsp] SSH/Telnet session hanging

[Mark Tinka]

On Thursday, June 02, 2011 01:58:21 AM Jeff Wheeler wrote:

> I believe that vendors have made a mistake by changing
> this default, but it is inconsequential to most networks
> because they have a consistent MTU across their whole
> backbone.  If you don't, you should base the iBGP TCP
> MSS on the smallest value which is safe for your
> network, and not use Path MTU Detection.  You can decide
> to figure this on a per-session basis, but this simply
> produces complexity for minimal gain in convergence
> time.

We have two networks, they all run Jumbo frames across the 
board. One does 9,192 bytes, the other does 9,000 bytes.

In all cases, we decided to set the 'tcp-mss' in Junos 
systems to 1,500 bytes, which is the lowest MTU we have in 
our network - toward our upstreams and peers.

Like you've pointed out, you can run 'tcp-mss' per group, 
but this just gives you more headache than it's worth. So to 
make it consistent from our border/peering routers to our 
core and edge routers, we simply use 1,500 bytes. This has 
worked very well, and performance has not been impacted.

For the Cisco's, I wrote this on 'c-nsp' back in '09:

http://www.mail-archive.com/cisco-
nsp at puck.nether.net/msg18844.html

Cheers,

Mark.
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