session initialization protocol (sip) presented by: lei luo computer & information science...
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![Page 1: Session Initialization Protocol (SIP) Presented by: Lei Luo Computer & Information Science Department University of Delaware Nov. 18, 2004 Some slides](https://reader031.vdocuments.net/reader031/viewer/2022032311/56649da95503460f94a96036/html5/thumbnails/1.jpg)
Session Initialization Protocol (SIP)
Presented by: Lei Luo
Computer & Information Science DepartmentUniversity of Delaware
Nov. 18, 2004
Some slides are borrowed from Dorgham Sisalem’s SIP Tutorial
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What Is SIP?
Phone Network
Alice
Alice’s Home Station
Bob
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What is SIP?
A signaling protocol Set up Modify Multimedia Sessions Tear down Request/deliver presence and Instant messages
Enable Internet endpoints Discover one another Agree on a characterization of a session
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What is NOT SIP?
Not a transport protocolNot a media transmission protocolNot a QoS Reservation ProtocolNot an integrated communications system
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Internet Multimedia Protocol Stack
Source: Henning Schulzrinne,http://www.cs.columbia.edu/~hgs/internet/
SCTP
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What can SIP Do?
User LocationUser AvailabilityUser CapabilitySession SetupSession Management
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What Else Can SIP Do?
Request/deliver presence information and instant message sessions: Publish and upload presence information Request delivery of presence information Notify presence and other events Transport instant messages
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Tesla Marconi
INVITE
180 Ringing
200 OK
ACK
Media Session
BYE
200 OK
Simple SIP session establishment exampleSimple SIP session establishment example
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AliceProxy Server
Bob
INVITE
180 Ringing
200 OK
ACK
Media Session
BYE
200 OK
INVITE
180 Ringing
200 OK
SIP call example with proxy serverSIP call example with proxy server
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Alice Registrar Server
REGISTERContact: sip:[email protected]
200 OK
SIP registration exampleSIP registration example
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SUBSCRIBE
200 OK
NOTIFY
200 OK
…
NOTIFY
200 OK
MESSAGE
200 OK
MESSAGE
200 OK
SIP presence and instant message exampleSIP presence and instant message example
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How does SIP Work?
Based on HTTP-like request/response modelText-based protocolUse the UTF-8 charsetSIP message
A request from a client to a server A response from a server to a client
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SIP User Agent (UA)
SIP-enabled end-devices Maintain states on calls
Local and remote tags Call-ID Local and remote CSeq header fields
Contain client (UAC) & server applications (UAS) Must support SDP for media description
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SIP User Agent Examples
Cisco Siemens
MIC
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Presence Agent
SIP devices Receive subscription requests Generate state notifications
Collect presence informationNeed to authenticate a subscription request
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SIP Gateway
A special type of UA Interface a SIP network to a non-SIP network
Terminate the signaling pathMay or may not terminate the media pathSupport much more users than normal UA
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SIP Networks with Gateways
InternalTelephoneExtn: 7040
SIP/PSTN Gateway
Department PBX
Web based configuration
Web server
Telephoneswitch
SQLdatabase
Proxy, redirect, registrar server
Extn: 7134
xiaotaow@cs NetMeeting
H.323
rtspd: media server
sipum: Unified messaging
Quicktime
RTSP clients
RTSP
Extn: 7136
713x
Single machine
SNMP(Network Management)
sipconf: Conference server
SIP/H.323 Gateway
Local/long distance1-212-5551212
Borrowed from Xiaotao Wu’s slides (Columbia University, 2002)
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SIP Servers SIP Workhorses
Logical Entities Accept SIP requests Respond to requests
Types of Servers Proxy Server Redirect Server Registration Server
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SIP Message Format
Generic-message= Start-line
*message-header
CRLF
[ message-body ]
Start-line= Request-Line / Status-Line
Request-Line = Method SP Request-URI SP SIP-Version CRLF
Status-Line = SIP-Version SP Status-Code SP Reason-Phase CRLF
SP – blank space
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SIP Methods Sets
Basic Methods INVITE REGISTER BYE ACK CANCEL OPTIONS
Extended Methods REFER SUBSCRIBE NOTIFY MESSAGE etc.
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SIP Response Codes
Consistent with/extend HTTP/1.1 response codes 1xx – Informational 2xx – Success 3xx – Redirection 4xx – Client error 5xx – Server failure 6xx – Global Failure
600 – Busy Everywhere 603 – Decline 604 – Does Not Exist Anywhere etc.
Borrowed from HTTP
Created for SIP
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SIP Registration Server
Alice Registrar ServerSIP/2.0 200 OKVia: SIP/2.0/UDP 128.175.13.50:5060; branch=z9hG4bKus19To: Alice <sip:[email protected]>From: Alice <sip:[email protected]>;tag=3431Call-ID: [email protected]: 1 REGISTERContact: <sip:[email protected]>;expires=3600Content-Length: 0
REGISTER sip:registrar.udel.eduVia: SIP/2.0/UDP 128.175.13.50:5060; branch=z9hG4bKus19Max-Forwards: 70To: Alice <sip:[email protected]>From: Alice <sip:[email protected]>;tag=3431Call-ID: [email protected]: 1 REGISTERContact: sip:[email protected]: 0
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SIP Proxy Server
Alice Bob
Outbound proxy server
Inbound proxy server
Location server
DNS server
Media (RTP)
INVITE sip:[email protected] SIP/2.0Via: SIP/2.0/UDP 100.101.102.103:5060; branch=z9hG4bKmp17aTo: Bob <sip:[email protected]>From: Alice <sip:[email protected]>;tag=42Subject: Where are you exactly?Contact: <sip:[email protected]>
INVITE sip:[email protected] SIP/2.0Via: SIP/2.0/UDP proxy.yahoo.com:5060; branch=z9hG4bKtiop3Via: SIP/2.0/UDP proxy.udel.com:5060; branch=z9hG4bK83842.1Via: SIP/2.0/UDP 100.101.102.103:5060; branch=z9hG4bKmp17aTo: Bob <sip:[email protected]>From: Alice <sip:[email protected]>;tag=42Subject: Where are you exactly?Contact: <sip:[email protected]>100 Trying
100 Trying
180 Ringing
180 Ringing
180 Ringing
200 OK
200 OK
200 OK
ACKBYE
200 OK
INVITE sip:[email protected] SIP/2.0Via: SIP/2.0/UDP proxy.udel.com:5060; branch=z9hG4bK83842.1Via: SIP/2.0/UDP 100.101.102.103:5060; branch=z9hG4bKmp17aTo: Bob <sip:[email protected]>From: Alice <sip:[email protected]>;tag=42Subject: Where are you exactly?Contact: <sip:[email protected]>
SIP Trapezoid
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SIP Proxy Server
INVITE Bob
Alice
Bob’s voicemail
Bob’s Phone
INVITE Bob
486 Busy Here
INVITE Bob
Proxy servers can make flexible “routing decisions” to decide where to send a request.
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SIP Proxy Server
INVITE Bob
Alice
Bob’s Cell PhoneINVITE Bob
INVITE Bob
Bob’s Office Phone
INVITE Bob
Bob’s Home Phone
In parallel search, a proxy issues several requests to possible user locations upon receiving an incoming request.
200 OK
200 OKCANCEL
CANCEL
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SIP Redirect Server
INVITE sip:[email protected] SIP/2.0Via: SIP/2.0/UDP 100.101.102.103:5060; branch=z9hG4bKmp17aTo: Bob <sip:[email protected]>From: Alice <sip:[email protected]>;tag=42Subject: Where are you exactly?Contact: <sip:[email protected]>
Alice
Bob
Redirect Server
SIP/2.0 302 Moved TemporarilyVia: SIP/2.0/UDP 100.101.102.103:5060; branch=z9hG4bKmp17aTo: Bob <sip:[email protected]>;tag=64From: Alice <sip:[email protected]>;tag=42Subject: Where are you exactly?Contact: sip:[email protected]
INVITE sip:[email protected] SIP/2.0Via: SIP/2.0/UDP 100.101.102.103:5060; branch=z9hG4bKmp17aTo: Bob <sip:[email protected]>From: Alice <sip:[email protected]>;tag=13473Subject: Where are you exactly?Contact: <sip:[email protected]>
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That’s It!
We have learned a lot about SIP!!
Did we really learn a lot of stuff about SIP?
No Way!!!
Then what are we gonna do?
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Key References
J. Rosenberg, SIP: Session Initialization Protocol, RFC 3261, 2002
A. Johnston, SIP: Understanding the Session Initialization Protocol, 2nd edition
J. Kuthan and D. Sisalem, SIP Tutorial http://iptel.org/sip/
SIP web site: http://www.cs.columbia.edu/sip/
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Questions?