tcp_isn_passphrase question

[Adam W.]

Guru's my current settings on my servers for tcp_isn_passphrase is 0. What impact will it have if I changed the setting to =1?

[Patrick Wallek · Accepted solution]

Have a read through this thread and see if it helps:

http://forums13.itrc.hp.com/service/forums/questionanswer.do?admit=109447627+1235411639230+28353475&threadId=1298896

[Adam W.]

Patrick, What I gather from the thread is that there is a change (of course) but nothing that will be noticed at all. Right?

[Laurent Menase]

Hi Adam,

the isn (initial sequence number) will be randomized RFC 1948.
The passphrase used will be "1"
you can set to any value since the kernel will use it as a passphrase when generating the seed of the randomization.- other parameters are taken.

when getting the value you will get 1.

Once enabled, it can't be disabled except rebooting, since that "ndd -set /dev/tcp tcp_isn_passphrase 0" will set the passphrase to "0" and don't reset it.

[Laurent Menase]

yes the result is compatible with TCP RFCs, so no noticeable change will be seen at all from applications or users, or peer systems.

[Adam W.]

Thanks Guys.