Hi, On 24 March 2009, Gilbert Lee wrote: >There are 3 ways of keep-alive mechanism from my experience. > >1. CRLF >2. OPTION >3. REGISTER
.. but none of these are standardized, so it's hard to implement and pick a good default. Some deployments may not like weird looking messages (blacklist you if you send garbage), some deployments don't like if otherwise valid SIP messages are repurposed for flow keepalives (OPTIONS, REGISTER). Using OPTIONS for keepalives is certainly not very elegant, but at least OPTIONS is standardized, and it is much more lightweight (for the servers) than sending REGISTERs. >It seems to be called SIP Session Timer while sending REGISTER >message again is called SIP Expire Time. Session timers are a different beast, and they are meant to keep a session (=e.g. a call) established. The big missing building block is however the keepalives for your network registration. >Any way, is there any standard declared document in RFC? The standard solution is a spec called draft-ietf-sip-outbound: http://tools.ietf.org/wg/sip/draft-ietf-sip-outbound/ Sofia-SIP has had an initial implementation of it for a long, long time, but unforunately (disclaimer: these are just my personal views): 1) The spec has been in the works for a _long_ time and it's still not ready. 2) It addresses more things than just the simplest case of keeping your registration alive. 3) As it's not ready yet, and nobody knows how widely it will be deployed by services, clients cannot really rely on just on sip-outbound (you still have to support other keepalive options as well unless you only need to support a very limited set of services) As for adding more non-standard keepalive options (e.g. CRLF and empty packets), that sounds like a good idea to me. Patches are welcome! :) -- first.surn...@nokia.com (Kai Vehmanen) ------------------------------------------------------------------------------ _______________________________________________ Sofia-sip-devel mailing list Sofia-sip-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/sofia-sip-devel
