Session Initiation Protocol

Session Initiation ProtocolThe department of Information &

Communications EngineeringDong-uk, kim

[email protected]

Table of Contents• Introduction• Transaction• Transport• Registration• Dialog • Initiating a session• Terminating a session• Headers

Introduction• Many Applications that require the creation and

management of a session.▫The Session initiation Protocol

Can enabling UA to discover one another General-purpose tool for creating, modifying and

terminating session Works independently of underlying transport protocols

SIP URIs• Two URI schemes

▫Similar to the form of an e-mail address: user@domain

• SIP URI - introduced in RFC 2543▫example: sip:[email protected]

• Secure SIP URI - introduced in RFC 3261▫example: sips:[email protected]▫Requires TLS over TCP as transport for security

SIP URIs (cont’d)• Several types of SIP URIs:

▫Address of Record (AOR) (identifies a user) example: sip:[email protected] Need DNS records to locate SIP Servers for

“domain.com”

▫Fully Qualified Domain Name (FQDN) (identifies a specific device) sip:[email protected] sip:[email protected] sip:[email protected];user=phone

Functionality

Operation

SIP Message structureINVITE sip:[email protected] SIP/2.0 <CRLF>INVITE sip:[email protected] SIP/2.0 <CRLF>

Via: SIP/2.0/UDP 169.130.12.5Call-ID: [email protected]: <sip:[email protected]>To: Bob<sip:[email protected]>CSeq: 1 INVITEMax-forwards: 70Content-Type: application/sdpContent-Length:885

Via: SIP/2.0/UDP 169.130.12.5Call-ID: [email protected]: <sip:[email protected]>To: Bob<sip:[email protected]>CSeq: 1 INVITEMax-forwards: 70Content-Type: application/sdpContent-Length:885

v=0o=xener 53655765 2353687 IN IP4 169.130.12.5s=hello sessionc=IN IP4 169.130.12.5m=audio 3456 RTP/AVP 0 3 4 5

v=0o=xener 53655765 2353687 IN IP4 169.130.12.5s=hello sessionc=IN IP4 169.130.12.5m=audio 3456 RTP/AVP 0 3 4 5

<CRLF><CRLF>

Start Line

Headers

Blank Line

Content

Request MethodBasic Extention

• INVITE• ACK• BYE• CANCEL• OPTIONS• REGISTER

• REFER• PUBLISH• SUBSCRIBE• NOTIFY• MESSAGE• INFO• UPDATE

Response code • 1xx: Provisional

▫ request received, continuing to process the request• 2xx: Success

▫ the action was successfully received, understood, and accepted

• 3xx: Redirection▫ further action needs to be taken in order to

complete the request• 4xx: Client Error

▫ the request contains bad syntax or cannot be fulfilled at this server

• 5xx: Server Error▫ the server failed to fulfill an apparently valid request

• 6xx: Global Failure▫ the request cannot be fulfilled at any server

Transaction• A SIP Transaction consists of

▫A single request▫Zero or more provisional responses ▫One or more final responses

• i.e.>▫An INVITE request▫Final response (which is not 2xx response)

The final ACK is part of the transaction

Transaction Process

UA

TCP,UDP,TLS/IP

Trasnport

Transaction

Transaction User

ApplicationStateful Proxy

Stateless Proxy

Stateful Proxy

UA

UAS UAC

S C

S C

TCP,UDP,TLS/IP TCP,UDP,TLS/IP TCP,UDP,TLS/IP TCP,UDP,TLS/IP

Proxy Core

Proxy Core

Proxy Core

Application

UAS UAC

S C

S C

S C

S C

S C

S C S C

INVITEClient Transaction

• Timer A▫ At each retransmit.▫ T1 = 500ms(default)

• Timer B▫ 64 * T1

• Timer D▫ At least 32sec. In unreliable transport▫ The duration, the server transaction

can remain in the Complete state == at INV. Server trans.

• Timer C ?▫ Managed by TU

Update at recv 101 ~199 Reset to different value

▫ But At least 3 min. If Fires

CANCLE / treat like 408

TransactionTransport Transport

Transaction

UAC UAS

INVITE

TU TU

Calling

Timer A expires---------Reset ASend INVITE

Proceeding

Recv. 1xx ---------1xx to TU

Complete

Recv. 3xx ~ 6xx ---------Send ACKSet Timer D

INVITE from TU---------Send INVITESet Timer A , B


Recv. 3xx ~ 6xx ---------Send ACK requestSet Timer D

Terminated

Timer D expires---------

Timer B expiresOr Transport Err.

-------------Inform TU



Transport Err.-------------

Inform TU

Recv. 3xx ~6xx ---------Send ACK

INVITE Server Transaction• Timer G

▫ At each retransmit.▫ T1 = 2 * T1▫ T1 = 500ms(default)

• Timer H▫ 64 * T1

== timer B• Timer I

Proceeding

Recv. INVITE ---------Send response

Complete

Confirmed

Recv. INVITE ---------INVITE to TUSend 100, if 200ms condition

3xx~6xx from TU---------Send responseSet Timer G & H

ACK--------Set Timer I

Terminated

Timer I expires---------

Transport Err.-------------

Inform TU

2xx form TU---------

Send response

1xx from TU---------Send response

Recv. INVITE ---------Send response

Timer G expires---------Send responseG = min(2*T1, T2)

Timer H expiresOr Transport Err.

-------------Inform TU


Transaction

UAC UAS

INVITE

TU TU

• Non-INVITE transaction do not make use of ACK▫ Simple req-res

interactions

Non-INVITE Client Transaction


Transaction

UAC UAS

Non- INVITE

TU TU

Trying

Timer E expires---------E = min(N*T1, T2)Send Req.

Proceeding

Complete

Req. from TU---------Send Req.Set Timer E, F


Recv. 2xx ~ 6xx ---------Response to TU

Terminated

Timer K expires---------

Timer F expiresOr Transport Err.

-------------Inform TURecv. 2xx ~6xx

---------Response to TU

Timer F expiresOr Transport Err.

-------------Inform TU

Timer E expires---------E=T2Send Req.


Non-INVITEServer Transaction Trying

Proceeding

Complete

Recv. Req. ---------Pass to TU


2xx ~ 6xx from TU--------Send responseSet Timer J

Terminated

Timer J expires---------

2xx form TU---------

Send response

Recv. Req.---------Send response


Transport Err---------Inform to TU

Transport Err---------Inform to TU


Transaction

UAC UAS

Non- INVITE

TU TU

Transport Layer• Mandatory

▫UDP & TCP

• If Message size is larger than Path MTU – 200 1300 (at unknown path MTU)

▫Must be sent using an RFC 2914 (such as TCP)

Overview• SIP offers a discovery capability• Registration creates bindings in a location service

▫Associates AoR ∈ Contact addresses

Registration Msg.

Registrar.biloxi.com

Location Server

Proxy.biloxi.com

Bob’s PC

Proxy.atlanta.com

Alice Softphone

REGISTER sip:registrar.biloxi.com SIP/2.0Via: SIP/2.0/UDP bobspc.biloxi.com:5060; branch=z9hG4bKnashds7Max-Forwards: 70To: Bob <sip:[email protected]>From: Bob <sip:[email protected]>;tag=456248Call-ID: 843817637684230@998sdasdh09CSeq: 1826 REGISTERContact: <sip:[email protected]>Expires: 7200Content-Length: 0

Discover a Registrar• UA can use three ways to determine the address

to which to send registrations▫Configuration

With a registrar address

▫Using AoR A UA should use the host part of the AoR as the

Request-URI and address the request there, using the normal SIP server locations mechanisms

▫Multicast Well-known (by all SIP servers)

“sip.mcast.net”(224.0.1.75)

RegistrarStart

Receive Request

Inspects the Request-URI

Check Require-h. &Authenticate Act as a Proxy

Check UAC modify right

403 Forbidden

Inspect theAoR(To header)

404 Not Found

The Index.Which indicates a binding of the list

The AoR(“To:”) convert to

Canonical form

Contains the Contact header

One exist/w “*” & expire

400 Invalid RequestAdditional header or

positive expires

Call-ID agree with binding

Req

uest fail

Expires interval1) param.2) header3) local policy

Less thanmin-Expire

423 Interval Too Brief/w Min-expire

Update or Add Bindings

A Fail

200 Ok/w bindings & expire

500 Server Error

Y

Y

Y

Y

Y Y

Y

Remove the binding

Check CSeq

Y

Y

Y

REGISTER sip:registrar.biloxi.com SIP/2.0Via: SIP/2.0/UDP bobspc.biloxi.com:5060;branch=z9hG4bKnashds7Max-Forwards: 70To: Bob <sip:[email protected]>From: Bob <sip:[email protected]>;tag=456248Call-ID: 843817637684230@998sdasdh09CSeq: 1826 REGISTERContact: <sip:[email protected]>Expires: 7200Content-Length: 0

Dialog• Represents a Peer to Peer SIP relationship

between two user agents▫Facilitates sequencing of messages between

the UAs and proper routing of requests

• A dialog is identified at each UA with a dialog IDwhich consists of▫Call-ID value▫A local tag ▫A remote tag

Creating A Dialog

INVITE [email protected]

[email protected] [email protected] Server Redirect Server


302 Moved Temporarily/w Contact: [email protected]


180 Ringing

200 Ok

ACK

100 Trying

180 Ringing

200 Ok

Early DialogRecv .101~199Start with INVITE

DialogRecv .2xxStart with INVITE

Record-Route /w params., orderAdd Contact headerTarget = Request.ContactDialog.Call-ID = Request.Call-ID

Add Record-Route

Route set: Reverse order of Record-Route

ACK

Cseq: a INVITE

Cseq: a ACK (CANCEL)

Requests within a Dialog

RTP

[email protected] [email protected] Server

200 Ok

ACK200 Ok

DialogRecv .2xxStart with INVITE

ACK

BYE

Route: <sip:proxy;lr>Cseq: a+1

BYE

BYE

Route: <sip:proxy;lr>Cseq: a

400 Bad request

DialogTerminated

200 Ok200 Ok

Overview

Agent(Offerer)

Agent(Answerer)

OfferAnswer

INVITE

200

INVITE

200

INVITE200

200

RFC 3264

UAC Processing• Initial Offer MUST be in either

▫An INVITE Answer : 2xx Msg.

▫Final 2xx response Answer : ACK

• Send INVITE Msg.▫UAC waits for response for the INVITE

“Expire:” Transaction returns a timeout

Treat as if “408”

UAC Processing • 1xx Response

▫Early dialog• 3xx Response

▫Using Contact Addr. Depend on Response Code• 4xx ~ 6xx Response

▫Terminating early dialog

UAS Processing• “Expires:” in INVITE Request

▫ If fires 487 (Request Terminated)• Progress

▫Can not answer the invitation immediately Provisional response To prevent cancelation

▫UAS must send a non-100 provisional response at every min.

• Redirected ▫300, 301, 302▫“Contact : ”

• Rejected▫488 response should include a warning header

Why the offer was rejected

UAS Processing• Accepted

▫The UAS core generates a 2xx response.▫ INVITE contains offer msg.

2xx response should contain answer

Terminating a Session• Each session is Associated with a single dialog

▫When a BYE is received on a dialog Any session associated with the dialog should

terminated

A UA must not send BYE outside of a dialog

Caller Callee

INVITE

100

180

Early DialogRecv .101~199Start with INVITE

BYE

Caller Callee

INVITE100180200

Confirmed Dialog

BYEACK

UAs Behavior• UAC

▫Creates a new non-INVITE client transaction• UAS

▫UAS receiving BYE msg. Must check if it matches an existing dialog

If not, responses 481 (Call/Transaction does not exists)

Summary of SIP headersHeader field Where Proxy ACK BYE CAN INV OPT REG Compact

Accept R - o - o m* o

Accept 2xx - - - o m* o

Accept 415 - c - c c c

Accept-Encoding R - o - o o o

Accept-Encoding 2xx - - - o m* o

Accept-Encoding 415 - c - c c c

Accept-Language R - o - o o o

Accept-Language 2xx - - - o m* o

Accept-Language 415 - c - c c c

Alert-Info R ar - - - o - -

Alert-Info 180 ar - - - o - -

Allow R - o - o o o

Allow 2xx - o - m* m* o

Allow r - o - o o o

Summary of SIP headers(2)Header field Where Proxy ACK BYE CAN INV OPT REG Compact

Allow 405 - m - m m m

Authentication-Info 2xx - o - m m m

Authorization R o o o o o o

Call-ID c r m m m m m m i

Call-Info ar i i i o o o

Contact R o - - m o o m

Contact 1xx - - - o - -

Contact 2xx - - - m o o

Contact 3xx d - o - o o o

Contact 485 - o - o o o

Content-Disposition o o - o o o

Content-Encoding o o - o o o e

Content-Language o o - o o o

Content-Length ar t t t t t t l


Content-Type * * - * * * c

CSeq c r m m m m m m

Date a o o o o o o

Error-Info 300-699 a - o o o o o

Expires - - - o - o

From c r m m m m m m f

In-Reply-To R - - - o - o

Max-Forwards R amr m m m m m m

Min-Expires 423 - - - - - m

MIME-Version o o - o o o

Organization ar - - - o o o

Priority R ar - - - o - -

Proxy-Authenticate 407 ar - m - m m m

Proxy-Authenticate 401 ar - o o o o o


Proxy-Authorization R dr o o - o o o

Proxy-Require R ar - o - o o o

Record-Route R ar o o o o o -

Record-Route 2xx,18x ma - o o o o -

Reply-To - - - o - -

Require ar - c - c c c

Retry-After

404,413,

480,486,

500,503,

600,603

- o o o o o

Route R adr c c c c c c

Server r - o o o o o

Subject R - - - o - - s

Supported R - o o m* o o k

Supported 2xx - o o m* m* o


Timestamp o o o o o o

To c(1) r m m m m m m t

Unsupported 420 - m - m m m

User-Agent o o o o o o

Via R amr m m m m m m v

Via rc dr m m m m m m

Warning r - o o o o o

WWW-Authenticate 401 ar - m - m m m

WWW-Authenticate 407 ar - o - o o o

▶ In “where”R: in requestsr: in responses2xx, 4xx, etc: response codec: copied from request to response

▶ In “proxy”a: can add/concatenate if not presentm: can modify valued: can delete valuer: must be able to be read (cannot be encrypted)

▶ In methodsc: conditional o: optionalm: mandatory t: should be sent, but can be omittedm*: should be sent, but can be omitted (mandatory in stream-based transport protocol)

IETF WGs• Applications Area• General Area• Internet Area• Operations and Management Area• Real-time Applications and Infrastructure Area• Routing Area• Security Area• Transport Area

WGsWG name Activity and Key wordsavt RTP

bliss Interoperability

drinks Provisioning, orthogonal to ENUM & SPEERMINT

ecrit Emergency

ENUM Telephone number mapping

geopriv Location convey

iptel Ip telephony with “tel” URI

mediactrl Media server control

mmusic SDP

p2psip P2psip

sigtran IP, PSTN interworking

simple IM & Presence, PIDF

SIP SIP

sipping Investigation, Event Package, 3GPP

speechse MRCP, TTS

speermint Session peering

xcom Centrailzed conference

RFC 2543

RFC 3261Overview

RFC 3262PRACK

RFC 3263Locating SIP

RFC 3264Offer / Answer

RFC 3265Event-Noti.

RFC 4575Conference

RFC 3515refer

RFC 3856Presence

RFC 3857winfo

…

RFC 2778Pres & IM

model

RFC 2779Requirement

RFC 3859CPP

RFC 3861locating

IM & pres.

RFC 3863PIDF

RFC 4479Data Model

RFC 4480RPID

RFC 4481Timed ext.

RFC 4482CIPID

RFC 4119PIDF_LO

…

RFC 3860CPIM

RFC 4079arch. of

GEOPROV LO

Protocol Definition

(SIP/SIPPING)

ServiceArchitecture

(SIMPLE)

InformationFormat

(SIMPLE/geopriv)

No. Is RFC WG remark title Rev. Status Abstract

1 RFC GEOPRIV RFC 4079 A Presence Architecture for the Distribution of GEOPRIV Location Object - RFC A protocol that carries PIDF_LO which used [I-D-SIP-location-Conveyance]

2 RFC GEOPRIV RFC 4119 A Presence-based GEOPRIV Location Object Format - RFC Describes a Location-Object(LO) for carrying geographical information on the internet.

3 RFC IMPP RFC 2778 A Model for Presence and Instatnt Messaging - RFC A Logical model for presence and instant messaging architecture

4 RFC IMPP RFC 2779 Instatn Messaging / Presence Protocol Requirements - RFC Defines a minimal set of requirements of IMPP

5 RFC IMPP RFC 3859 Common Profile for Presence (CPP) - RFC Defines common semantics and data formats for preence

6 RFC IMPP RFC 3860 Common Profile for Instant Messaging (CPIM) - RFC Defines common semantics and data formats for IM

7 RFC IMPP RFC 3861 Address Resolution for Instant Messaging and Presence - RFC Provides a guidance for locationg the resources associated with URIs using DNS, SRV

8 RFC IMPP RFC 3863 Presence Information Data Format (PIDF) - RFC A Definition for Presence Information Data Format (PIDF) as an Extension of XML

9 RFC SIMPLE RFC 4482 CIPID: Contact Information for the PIDF - RFC Additional Contact Information to the Presentity

10 RFC SIMPLE RFC 4660 Fuctional Description of Event Notification Filtering - RFCDescribes the opeations a subscriber performs in order to put filtering rules associated with a subscription

11 RFC SIMPLE RFC 4662 A SIP Event Notification Extention for Resource Lists - RFC A Subscribe mechanism for a list of resource, instade of send SUBSCRIBE to each resource

12 RFC SIMPLE RFC 4481Timed Presence Extensions to the PIDF to Indicate Status Information for Pas and Future Time Intervals

- RFC A PIDF extension for timed status information for a time interval fully in the future or the past

13 RFC SIMPLE RFC 5263 SIP Extension for Partial Notification of Presence Information - RFC Describes the partial notification mechanism

14 RFC SIMPLE RFC 5262 PIDF Extension for Partial Prescnce - RFC A Definition for using PIDF XML for partial presence

15 RFC SIMPLE RFC 5264 Publication of Partial Presence Information - RFC A mechanism for partial presence information

16 RFC SIMPLE RFC 5196 SIP UA Capability Extension to PIDF - RFC Defines a PIDF extension to represent SIP IA capabilities

17 RFC SIMPLE RFC 4479 A Data Model for Presence - RFC A definition to PIDF for presence and instant messaging

18 RFC SIMPLE RFC 5025 Presecne Authorization Rules - RFC Authorization rules for Presence

19 RFC SIMPLE RFC 3856 A Presence Package for the SIP - RFC Presence extension for the event package

20 RFC SIMPLE RFC 4480 RPID: Rich Presence Extensions to the PIDF - RFC An extension that adds optional elements to the PIDF

21 RFC SIMPLE RFC 3857 A Watcher Information Event Templete-Package for the SIP - RFCAn event templete package for event notification for management watcher information that associated a resource

22 RFC SIMPLE RFC 3858 An XML based Format for Watcher Information - RFC A PIDF Definition for Watcher Information

23 RFC SIMPLE RFC 4825 The XML Configuration Access Protocol(XCAP) - RFC A protocol definition that can read, write, modify application in XML format on a server

24 RFC SIMPLE RFC 4826 XML Formats for Representing Resource Lists - RFC A Definition how to reprensenting resource list with XCAP

25 RFC SIMPLE RFC 4827 An XCAP Usage for Manipulating Presence Document Contents - RFC Describes a usage of the XCAP for manipulating the contents of PIDF

26 Draft SIMPLEinterdomain-scaling-

analysisPresence Interdomain Scalling Analysis for SIP/SIMPLE 5 Publication Requested An analysis for presence and IM traffic as an informational doc.

27 Draft SIMPLE view-sharing Optimizing Federated Presence with View Sharing 1 Active A traffic reduce method with view sharing associated I-D-interdomain-scaling-analysis

28 RFC SIMPLE RFC 3856 A SIP Event Package for the SIP - RFC The usage of the SIP for subscriptions and notifications of presence

29 Draft SIP info-event SIP INFO Method and Package Framework 0 Active Defines a event package for session defining, negotiation and exchanging with INFO method

30 Draft SIP location-conveyance Location Conveyance for the SIP 10 ActiveDefines an extension to the SIP to convey geographic location information from one to another SIP entity

31 RFC SIP RFC 3515 The SIP Refer Method - RFC Defines REFER method, refer event package and refer-to request header

32 Draft SIPPINGpresence-scaling-

requirementsScaling Requirements for Presence in SIP/SIMPLE 1 Active A set of requirements for enabling interdomain scaling on presence

33 Draft SIPPING cc-framework A Call Control and Multi-party usage framework for the SIP 10 Publication Requested Define a framework and requirements for call control and multi party usage of SIP

34 Draft SIPPING cc-transfer Session Initiation Protocol Call Control - Transfer 11 Waiting for AD As a part of SIP Multipart call control - call transfer with REFER

35 Draft SIPPING config-framework A Framework for SIP User Agent Profile Delivery 15 AD Evaluation A Framework ro enable configuratio of SIP UA in SIP deployment

36 Draft SIPPING policy-package A SIP Event Package for Session-specific Session Policies 5 IESG Evaluation Enables UA to subacribe to session policy for a SIP session and to receive notifications, if it change

37 Draft SIPPING rtcp-summary SIP Package for Voice Quaity Reporting Event 5 IESG Evaluation A Definition to enable the collection and reporting that measure the qualituy for VoIP sessions

38 Draft SIPPING gruu-reg-event Registration Event Package Extention for SIP GRUUs 9 Last CallReg. event package (RFC3680) extention to GRUU for frequency unreachable 'contact' information

39 Draft SIPPING pending-additions The SIP Pending Additions Event Package 5 RFC Ed. QueueDefines a event package whereby user agent can subscribe to the consent-related state of the resources[ID-sip-consent-framework] that are being added to a resource list that defines translation

40 RFC SIPPING RFC 4575 A SIP Event Package for Conference State - RFC A SIP Event Package for tightly coupled conferences using the SIP

41 RFC SIPPING RFC 4235 An INVITE-Initiated Dialog Event Package for the SIP - RFC A Dialog event package for INVITE initiated dialog

42 RFC SIPPING RFC 4730 A SIP Event Package for Key Press Stimulus - RFCDescribes a KPML that enables monitoring of DTMF signals and user XML docs refered to as KPML

43 RFC SIPPING RFC 3842 A Message Summary and Message Waiting Infication Event Package for the SIP - RFCA SIP Event Package to carry message waiting status and message summaries form a messaging systm to UA

44 RFC SIPPING RFC 4354A SIP Event Package and Data Format for Various Setting in Support for the PTToCellular Service

- RFCDefines a SIP event package to support publication, subscription, and notification of additional capabilities for PoC

45 RFC SIPPING RFC 3680 A SIP Event Package for Registration - RFC A Event Package for Register event occurred state

46 RFCSPEERMIN

TRFC 5344 Presence and Instant Messaging Peering Use Cases - RFC

Describes several user cases of peering of non-VoIP services between two or more Service Provider

( ㅡ _-)’’

SIP-overload WGRate-based Overload Control• Limit the request rate a server receives from an

upstream element. ▫ Feedback: X requests per second.

Loss-based Overload Control• Reduce the request rate a server receives by a

percentage X.▫ Feedback: reduce load by X%.

Window-based Overload Control• Limit the number of request a server can receive

without confirming a request.▫ Feedback: send X more requests.

Overload Signal-based Overload Control• De-/increase of request rate until a target overload

notification rate is reached. ▫ Feedback: server overloaded (503 response without

Retry–After header)

Any Questions

Session Initiation Protocol

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