[j-nsp] 'tracepath' broken with Junipers

[Pekka Savola]

Hi,

Tracepath is a nice tool which can be used, among other things, to 
find the PMTU of the path, and to observe whether the path seems 
asymmetric or symmetric (this is done by comparing the TTLs of the 
packets).

Unfortunately, Junipers seem to break tracepath, because apparently 
they decrement TTL twice when sending ICMPs, making the path always 
look asymmetric.

The easy fix would be to send the ICMPs with (e.g.,) TTL=129 so that 
after decrementing twice, it would look like (to those who assume a 
regular base TTL is 128) it has only been decremented once.

We opened a case on this a long time ago, but apparently tracepath 
wasn't considered one of tools Juniper wants to support.

Any comments?

-- 
Pekka Savola                 "You each name yourselves king, yet the
Netcore Oy                    kingdom bleeds."
Systems. Networks. Security. -- George R.R. Martin: A Clash of Kings