9 Oct
2008
9 Oct
'08
12:41 a.m.
El Miércoles, 8 de Octubre de 2008, Victor Pascual Ávila escribió:
Actually I understand this document to be part of a
research project.
I don't believe that ignoring a VIA header or preventing a SIP entity
from inserting a VIA header is a common praxis in the industry. But as
you might imagine, research is research and prototypes are prototypes
Well, however this is completely unfeasible since it would involve modifying
all the SIP devices to be compliant with this non RFC3261 specification.
This is: even if a proxy doesn't add a Via header, the response will come
through the proxy because the destination UAS adds to the top Via:
"received=PROXY_IP;"
It doesn't matter if the top Via is the Via inserted by the UAC (since the
proxy didn't add its own Via). However, the UAS will add the "received"
parameter poiting to the proxy IP, so it will send the reply to the proxy.
Also, it's a completely crazy idea. What to do in the following scenarios?
a) UAC --- (udp) --> LB proxy -- (tcp) --> UAS
b) UAC --- (tcp) --> LB proxy -- (udp) --> UAS
Note that replies for a transaction must use the same network transport, so
it's just impossible that UAS in case a) (who receives the request via TCP
from proxy) to reply UAC directly using UDP.
So in conclusion, I think that the document tells about something obvisouly
not tested, in fact, something illegal with the current SIP specification.
Thanks for your comment. Regards.
--
Iñaki Baz Castillo