1. SIP Session Timer Jonathan Rosenberg dynamicsoft

2. Changes zSignificant overhaul from previous version zMotivation: list discussion on supporting function when only one of UAS/UAC knows extension z Works since you don’t need to support it to receive re-invites z Want either side to perform reinvites

3. Call Flow zUAC supports, UAS doesn’t y200 OK won’t have S- T yLast proxy that inserted S-T inserts S- T value + Require into response yRequires stateful S-T proxies INV; k:timer S-T: 500 200 OK Require: timer S-T: 500 UACUASProxy ACK INV; k:timer S-T: 500

4. Call Flow zUAS supports, UAC doesn’t yNo Supported in INVITE yProxy inserts S-T anyway yUAS reflects S-T, no Require, knows it is doing re-INVITES INV S-T: 500 200 OK S-T: 500 200 OK S-T: 500 ACK INV; k:timer S-T: 500 INV; k:timer S-T: 500 UACUASProxy

5. Call Flow zNeither Supports yProxy inserts S-T timer even though no Supported yNo S-T in response yProxy doesn’t insert S- T or Require INV S-T: 500 200 OK ACK UACUASProxy

6. Call Flow zBoth Support ySame as previous drafts yUAC will perform timer zOpen issues yreinvite issues? INVk:timer S-T: 500 200 OK S-T: 500 Require: timer 200 OK S-T: 500 Require: timer ACK UACUASProxy INV; k:timer S-T: 500