Now that K v3.1.0 provides send_reply(), what is the preferred
ideology about whether to send stateful or stateless negative error
replies?
I mean in general, not in specific cases like digest authentication in
the new 'auth' module, where, according to the docs, a transaction and
stateful replies are required in order for enhanced nonce replay
protection.
The traditional wisdom in past bodies of scripts and knowledge in the
public realm has been, in my interpretation, that stateless replies
are acceptable for final negative responses from script[1]. After
all, a reply like "404 Not Found" from the proxy is basically
fire-and-forget; why devote additional transactional memory to it
while the transaction hold-down timer expires? We do not care if we
receive an ACK, nor want anything further to do with this branch.
On the other hand, there is a point of view out there that mixing
stateless and stateful replies is not good, despite the somewhat
increased overhead and resource usage associated with making all
replies stateful. This perspective emphasises that if the proxy is
fundamentally operating in a stateful manner, it should do so with
respect to all messages, rather than allowing a large category of
replies to slip under the radar of TM and have possibly inconsistent
results.
For now, I have changed my code to use send_reply() in all cases where
sl_send_reply() was used in the past; it seems easier to let
Kamailio/SR make the decision. However, in practice, most requests
will result in the creation of a transaction, so it is like replacing
sl_send_reply() with t_reply() in the majority of cases.
Am I missing anything? Any salient considerations I missed?
I am curious as to the consensus about the best practice here from the
vantage point of the developers.
Thanks,
-- Alex
[1] Except in FAILURE-ROUTEs, from which only stateful replies may
be issued.
--
Alex Balashov - Principal
Evariste Systems LLC
1170 Peachtree Street
12th Floor, Suite 1200
Atlanta, GA 30309
Tel: +1-678-954-0670
Fax: +1-404-961-1892
Web: http://www.evaristesys.com/
_______________________________________________
SIP Express Router (SER) and Kamailio (OpenSER) - sr-users mailing list
sr-users@lists.sip-router.org
http://lists.sip-router.org/cgi-bin/mailman/listinfo/sr-users
