At 06:14 PM 3/15/2004, Klaus Darilion wrote:

Hi!

If the proxy replies stateless, how should the proxy handle the incoming ACK request?

e.g. an INVITE to an offline user:

if (!lookup("location")) { sl_send_reply("404", "Not Found"); break; }

The SIP client will respond with ACK to the 404 response. How shall I handle this ACK - just ignoring it?

sl_send_reply generates a specific to-tag. ACKs with this totag will be consumed before script processing occurs. This fails if there is already a to-tag -- then ACK gets inside the script. To address that one would have to reply statefuly and consume ACKs based on transaction state. I personaly prefer the stateless operation for better scalability.

BTW: Is it allowed to send stateless replies on existing transactions? e.g: t_newtran(); ... sl_send_reply(..);

It is not forbidden but it will break. If no reply is put in the transaction state, the transaction state will expie someday and generate 408. Use t_reply if you created transaction state. A typical sequence follows:

# message store if (method == "MESSAGE") { if (!t_newtran()) { # T-state not created, failure occured (lac of memory?) sl_reply_error(); # -> it is safe to reply statelessly break; };

if (m_store("0")) { # there is transaction state -> do reply statefuly now t_reply("202", "Accepted for Later Delivery"); break; };

# message store failed but T-state already exists -- again, reply # statefuly t_reply("503", "Service Unavailable"); break; };

-jiri