20 aug 2012 kl. 10:06 skrev Daniel-Constantin Mierla: > Hello, > > over the weekend I committed the code that allows to remove contacts from > location table if the device does not respond to several attempts of SIP nat > keepalives (usually OPTIONS requests). > > The feature works only for SIP over UDP, being the only transport for which > nathelper module sends keepalives (or sip ping requests as written in some > docs). > > Also, the lack of keepalive reply is tracked only for location records stored > in memory (so it does not work with db only mode for usrloc). This is because > the keepalives are sent stateless, not using tm module, to avoid overloading > of timers and shared memory when dealing with large subscriber base -- > therefore the implementation is very lightweight in using resources, > targeting of course scalability. Detection of replies for keepalives is done > based on from tag which carries the internal unique id of the location > contact (which is available from v3.3). > > In order to enable this feature you have to set the keepalive_timeout > parameter of nathelper module -- that's the only addition you have to add to > a config that sends SIP nat keepalives. Internally, the modules store the > timestamp of the last SIP keepalive reply (nathelper detects the right reply > and calls usrloc API for storing the timestamp in contact structure in > memory). > > http://kamailio.org/docs/modules/devel/modules_k/nathelper.html#id2535244 > > Before sending a new keepalive to a contact, it is checking if the last > keepalive reply is older than keepalive_timeout value and if yes, will lower > the expires to 10 seconds (if the expires is higher). There is no special > handling of keepalive reply codes, all of them will update the last keepalive > timestamp. > > This feature should be useful in mobile networks, to avoid stacking lot of > invalid contacts which could result in lot of branches causing many > retransmissions. > > There is plant to go for tcp/tls as well and detect when the connection is > down, but looks like no spare time in the near future. However, right now > using set_forward_no_connect() will avoid trying to create new connections > for natted uses whose registration connection is down. > On my personal wish list is to have an event route when a registered device becomes unreachable - like a closed TCP connection for a device behind NAT or failure to response to NAT pings.
/O
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