Hi, Its not mandatory as it may flood the network with Re-invites or Updates even in valid call scenarios which are running for quite a long time. I could see that as the main reason.
Also if we are using TCP as transport we can build TCP based "Keep alive" mechanism. Session timers are mainly useful for proxy when UDP is the transport. >From UAC/UAS(endpoints) it will not be a major issue as they can clear off the transaction when user disconnect. After all user will be aware of there is some one responding at the other end or there is silence. Hope I have answered your question. Regards Sunil Verma ESN: 877-5050 Ph: +919731245000 -----Original Message----- From: [email protected] [mailto:[email protected]] On Behalf Of M. Ranganathan Sent: Sunday, July 11, 2010 1:57 AM To: sip-implementors Subject: [Sip-implementors] Expires header. Why not mandatory for DialogForming INVITE Hello, I am wondering why it is not mandatory for the UAC to attach an Expires to a dialog forming INVITE. It would seem useful for at least a couple of things: 1. Stack can know when to tear down a "dead" transaction which is stuck in Proceeding state. 2. Downstream proxy can know what the max fork expiration time can be. It would seem useful to make this a mandatory header for a dialog forming INVITE and yet it is not. Just wondering why. Ranga -- M. Ranganathan _______________________________________________ Sip-implementors mailing list [email protected] https://lists.cs.columbia.edu/cucslists/listinfo/sip-implementors Please do not print this email unless it is absolutely necessary. The information contained in this electronic message and any attachments to this message are intended for the exclusive use of the addressee(s) and may contain proprietary, confidential or privileged information. If you are not the intended recipient, you should not disseminate, distribute or copy this e-mail. Please notify the sender immediately and destroy all copies of this message and any attachments. WARNING: Computer viruses can be transmitted via email. The recipient should check this email and any attachments for the presence of viruses. The company accepts no liability for any damage caused by any virus transmitted by this email. www.wipro.com _______________________________________________ Sip-implementors mailing list [email protected] https://lists.cs.columbia.edu/cucslists/listinfo/sip-implementors
