Thank you for your detailed answer.I learned a lot from your reply. On Thu, Mar 26, 2009 at 9:30 PM, <kai.vehma...@nokia.com> wrote:
> 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) >
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