[Serusers] UAS Cancel handling

Antanas Masevicius antanas.masevicius at z1sys.com
Tue Nov 16 16:43:34 CET 2004


Hello,

after setting fr_timer and fr_inv_timer to lower values than default:

modparam("tm", "fr_timer", 12)
modparam("tm", "fr_inv_timer", 24)

noticed that some SIP phones continues to ring even if a caller hangs up
the phone. After a callee receives CANCEL message it responds either with
481 ir 487 (transaction does not exists). If fr_inv_timer is not expired,
callee responds with 481 and cancels INVITE request. If timer, by the time
caller sends CANCEL, is expired, callee returns 487 and does not stop
ringing.
After comparing CANCEL messages in both cases (using algorithm
described in 3261, 17.2.3) i didn't find any difference between them
(Branch, sent-by, to tagm from tag, call-id, cseq - all matches). How UAS
distinguishes these CANCEL messages and how SER changes CANCEL message
after fr_inv_timer is exeeded?

Antanas





More information about the sr-users mailing list