Introduction and architecture about Session Initiation Protocol

1. Introduction:
Session Initiation Protocol (SIP)
Aung Thu Rha Hein(g5536871)

2. Agenda
 Overview of SIP
 SIP Functions & Features
 SIP Architecture
 SIP Components
 SIP Server Modes
 Sample SIP call scenario
 SIP Requests & Responses
 Protocols used with SIP
 Summary & Conclusion
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3. Overview of SIP
 A signaling protocol used to create, manage and
terminate sessions in IP network
 A standard protocol defined by IETF
 IETF mapped it as Application-layer protocol in OSI
layer
 Similar to HTTP & SMTP protocol in syntax
 URI: SPI: aung@mahidol.com
 It is extensible
 But doesn’t provide end-to-end functionality
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4. SIP Functions & Features
 User Location
 Address Resolution: translate URIs to current IP address
 User Availability
 User can control certain types of communication status
 User Capabilities
 Determining the features available by both parties’
programs
 Session Setup
 a three-way handshake
 Session Management
 Able to modify session in use
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5. SIP Functions & Features(Cont. )
 Registration
 Users can register themselves using their ID, independent
from the device registration
 Redirect
 SIP server can redirect a request to another address
 Forking
 Request forwarding: Serial & Parallel Forking
 Proxy
 Proxy server can forward the request of the user to
another one
 Mobility
 SIP calls can set up if proper gateways are provided
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6. SIP Architecture
 SIP Components
 User Agents
 Can act as User Agent Client (UAC) and User Agent Server (UAS)
 SIP Endpoints: Softphone, SIP phone, Smart Phone, PDA
 SIP Servers
 Registrar
 Authenticate and register UA’s location and status
 Proxy
 Forward request to other computers. Involve in session setup and
teardown
 Redirect
 Redirect clients to UAs they are attempting to contact. Also can fork a
call.
 Location Services
 A database that used to keep information about users’ registration
and their locations
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7. SIP Architecture(cont.)
 SIP Server Modes
 Stateful vs Stateless
 SIP server can run in one of these two modes
 Stateful server keep track of all requests and responses
 Stateless server found as part of backbone
 Client/server vs P2P
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8. Sample SIP call scenario
 SIP Registration
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9. Sample SIP call scenario(cont.)
 Request through Proxy server
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10. Sample SIP call scenario(cont.)
 Request through Redirect server
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11. SIP Requests & Responses
SIP Request Packet
INVITE sip:14158867900@me.com:5060SIP/2.0
From: ”ALICE" <sip:9184249378@67.231.5.6>
To: <sip:14158867900@108.166.22.22>
Contact: <sip:9184249378@67.231.5.6:1234>
Call-ID: 490dffec2cafa2772a11eec8716e
CSeq: 102 INVITE
User-Agent: middleserver
Max-­­Forwards: 30
Allow: INVITE,ACK, CANCEL, OPTIONS, BYE,REFER, SUBSCRIBE
Content-Type: application/sdp
Content-Length:180
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12. SIP Requests & Responses
SIP Response Packet
SIP/2.0 100 Trying (180 Ringing, 200 OK)
From: ”BOB" <sip:9184249378@67.231.5.6>
To: <sip:14158867900@108.166.22.22>
Call-ID: 490dffec2cafa2772a11eec8716e
CSeq: 102 INVITE
User-Agent: middleserver
Max-­­Forwards: 30
Allow: INVITE, ACK, CANCEL, OPTIONS, BYE, REFER, SUBSCRIBEBYE, REFER,
SUBSCRIBE
1xx : Informational
2xx Success: request successful
3xx Redirection : request should tried another location
4xx Client Error: an error in request
5xx Server Error: an error in recipient
6xx Global Failure : request has failed and should not be retried again
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13. Protocols used with SIP
 User Datagram Protocol (UDP)
 used to send datagrams over IP network
 Transport Layer Security (TLS)
 provides security between applications
 Session Description Protocol (SDP)
 used to send description information when sending multimedia
data
 Real-Time Transport Protocol (RTP)
 used to transport real-time data across a network
 Media Gateway Control Protocol (MGCP)
 used to control gateways that provide access to the PSTN
 Real-Time Streaming Protocol (RTSP)
 used to control the delivery of streaming media
 SIMPLE (SIP for Instant Messaging and Presence Leveraging
Extensions)
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14. Summary & Conclusion
 A fundamental building block for real-time
communication
 SIP is an open standard and development
community is trying for higher interoperability
 Research going for further enchantments and
solutions to known issues
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