The new bis Jonathan Rosenberg dynamicsoft

Why rewrite the specification? IESG said so RFC2543 was never the model of clarity to begin with Bis got worse with micro-editing Symptoms –Repitition of material in many places –No overview of operations –Structure not obvious Decision made at August IETF to move forward full steam with a rewrite

How was it done? Recruited a bis rewrite team –Jonathan, Henning editors –Added four co-authors to help write Gonzalo Camarillo (Ericsson) Jon Peterson (Neustar) Alan Johnston (Worldcom) Robert Sparks (dynamicsoft) –Coaching from Dean Willis, Brian Rosen –Project Management from Rakesh Shah –Technical writing from Jean Mahoney Jonathan prepares new outline and defines mapping of existing text to new outline (early Sep.) Sections assigned to each writer

How was it done? First iteration done, mid-September Five iterations follow, with reviewers assigned to specific sections Nearing final iterations, MUST/MAY/SHOULD trackers assigned –Brutally painful! Final draft complete and submitted 10/26/01

New structure Present SIP as a layered protocol –Message layer –Transport layer –Transaction layer –Transaction users Semantically oriented Message layer –Self explanatory – message formats Transport layer –Manages persistent connections –Listens for requests and responses –Via rules for sending responses, inserting received param

New Structure Transaction layer –Reliability –Request/response matching –ACK generation for non-INVITE Some big changes here –ACK-200 is officially a different transaction –ACK non-200 is part of the transaction –Same EXACT transaction machine for proxies and UA –Handling for INVITE 2xx response *NOT* part of the transaction layer!! UA state machinery retransmits 2xx and ACK Allows transaction machines to die instantly when 2xx received –Transitions based on timeouts, not # of retransmits, to unify machine between UDP, TCP More aggressive transaction timeouts defined for TCP –Proper RTT estimation defined –Actual diagrams for non-INVITE transactions included

INVITE Client FSM |INVITE from TU Timer A fires |INVITE sent Reset A, V Timer B fires INVITE sent t.o. to TU | | | | Calling | | >| | >| xx | | | 2xx to TU | ACK sent | |1xx | |1xx to TU | | | | | 1xx V Timer C fires | | 1xx to TU t.o. to TU | | | | >| | | |Proceeding | | | >| | >| | xx | | | 2xx to TU | | ACK sent, | | | resp. to TU| | | | | NOTE: | V | | ACK sent | transitions | | | | labeled with | | | Completed | | the event | >| | | over the action | | to take | ^ | | | | | Timer D fires | | - | | | V | | | | | | Terminated|< | |

INVITE Server FSM |INVITE |pass to TU, send 100 INVITE V send response | | from TU | | Proceeding| |send response >| |< from TU | |2xx from TU send response | |send response | | | INVITE V Timer G fires | send response send response | | | | | | Completed | | | >| |< | | | | | ACK | | | - | >+ | Timer H fires | V fail to TU | | | | | | Confirmed | | | | | | | | |Timer I fires | |- | | | V | | | | | | Terminated|< | |

Outline 1.Intro 2.Overview of Functionality 3.Terminology 4.Overview of Operation 5.Structure of the Protocol 6.Definitions 7.SIP Messages 8.General UA Behavior 9.Canceling Requests 10.Registrations 11.Querying for Capabilities 12.Dialogs 13.Initiating a Session 14.Modifying a Session 15.Terminating a Session 16.Proxy Behavior 17.Transactions 18.Transport 19.Security 20.Common Message Components 21.Headers 22.Response Codes 23.SRV 24.Examples 25.BNF

Dialogs Equivalent to call-leg from bis-04 Call leg has been eradicated from the spec –Generalization, presence Dialog procedures are no longer INVITE specific –Maintenance of Cseq, Route sets –Construction of mid-dialog requests –General construction guidelines

Other changes Collected BNF BNF now uses explicit LWS –Has been validated by Robert Responses no longer need to transmitted over TCP for server transactions! –Does NOT include INV-2xx CANCEL cant be sent until 1xx received BYE cant be sent by UAS until ACK received CR or LF alone deprecated 3xx to re-INVITE allowed and specified Merged requests OK (good, actually) Radical surgery on multicast –No special treatment at ALL except deciding where to send the messages –Assumes only a single respondent –If there are more than one, responses look like retransmits –Still needs more refinement in spec Proxies no longer forward 6xx on receipt –CANCEL first, then 6xx after all responses Serverfeatures integrated 100rel will be integrated SDP extracted to separate I-D

Whats not stable? Registration section needs more rigor Security section needs a lot more rigor, a lot more explanatory text SRV functionality likely to change –Under discussion with IESG –Likely to be much simplified (no merging of transports) Proxy Route/maddr/dns processing still shakey