Transcript PowerPoint 프레젠테이션

SIP Overview
Contents
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What is Sip?
SIP Benefits
SIP message structure
SIP components
SIP mobility
SIP
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What is SIP?
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Sip is signaling protocol defined by the Internet
Engineering Task Force (IETF) for initiating,
managing and terminating voice and video
sessions across packet networks
A textual based client-server protocol
Application layer protocol
It’s not Transport Protocol
It’s not QoS Reservation Protocol
SIP
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SIP history
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Work began in 1995 in IETF mmusic WG
03/1999: RFC 2543, 153 pages, 6 methods
11/1999: SIP WG formed
11/2000: draft-ietf-sip-rfc2543bis-02, 171 pages,
6 methods
SIP
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SIP benefits
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Integration with existing protocols
 Integration well with Web(Http) and e-mail(Smtp)
Simplicity
Simple protocol vs H.323
 Textual based, so parsing generation are simple
Extensibility
 HTTP and SMTP extensibility
Modularity
 Initiation,termination,change,user location, basic
registration.
 Separating notion of a session to invite a user
Scalability
 Off DNS, BGP
 Server processing.
SIP
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SIP Messages
SIP Requests:
 INVITE – Initiates a call by inviting user to participate
in session.
 ACK - Confirms that the client has received a final
response to an INVITE request.
 BYE - Indicates termination of the call.
 CANCEL - Cancels a pending request.
 REGISTER – bind a permanent address to current
location
 OPTIONS – Used to query the capabilities of a
server.
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SIP
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SIP Response Codes
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1yz Informational
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200 ok
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3yz Redirection
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300 Multiple Choices
301 Moved Permanently
302 Moved Temporarily
4yz Client error
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100 Trying
180 Ringing (processed
locally)
181 Call is Being
Forwarded
2yz Success
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5yz Server failure
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SIP
400 Bad Request
401 Unauthorized
404 Not Found
405 Method not Allowed
407 Proxy Authentication
Required
415 Unsupported Media
Type
482 Loop Detected
486 Busy Here
500 Server Internal Error
6yz Global Failure
 600 Busy Everywhere
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Invite Message Example
Request Method
Response Status
INVITE sip:[email protected] SIP/2.0
Via: SIP/2.0/UDP here.com:5060
From: BigGuy <sip:[email protected]>
To: LittleGuy <sip:[email protected]>
Message
Call-ID: [email protected]
CSeq: 1 INVITE
Header
Subject: Happy Christmas
Fields
Contact: BigGuy
<sip:[email protected]>
Content-Type: application/sdp
Content-Length: 147
SIP/2.0 200 OK
Via: SIP/2.0/UDP here.com:5060
From: BigGuy <sip:[email protected]>
To: LittleGuy
<sip:[email protected]>;tag=65a35
Call-ID: [email protected]
CSeq: 1 INVITE
Subject: Happy Christmas
Contact: LittleGuy <sip:[email protected]>
Content-Type: application/sdp
Content-Length: 134
v=0
o=UserA 2890844526 2890844526 IN IP4 here.com
s=Session SDP
c=IN IP4 100.101.102.103
t=0 0
m=audio 49172 RTP/AVP 0
a=rtpmap:0 PCMU/8000
v=0
o=UserB 2890844527 2890844527 IN IP4 there.com
s=Session SDP
c=IN IP4 110.111.112.113
t=0 0
m=audio 3456 RTP/AVP 0
a=rtpmap:0 PCMU/8000
Payload
“receive RTP G.711-encoded audio at
SIP
100.101.102.103:49172”
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Address Header Fields
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From: message originator
To: final recipient
Request-URI: current destination; may change along
signaling path
Contact: appears in INVITE / OPTIONS / ACK / REGISTER
requests and in responses. It indicates direct response
address to which subsequent transactions are sent.
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A UA may send subsequent BYE or ACK to Contact: address
(unless configured to use an outbound proxy).
It includes redirection address in 3xx and 485 responses.
It includes additional error information in 4xx, 5xx, and 6xx
responses.
It may include preference weights.
It includes current location in REGISTER requests.
Multiple Contact: header fields may be included.
SIP
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Session Description Protocol (SDP)
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Convey sufficient information to
enable participation in a multimedia
session
SDP includes description of:
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Session name and purpose
Times the session is active
Media to use
Information where to send and receive
media
Contact information
SIP
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Session Description Protocol (SDP)
o=sisalem 28908044538 289080890 IN IP4 193.175.132.
118
s=SIP Example
[email protected]
c=IN IP4 126.16.69.4
v=0
t=28908044900 28908045000
m=audio 49170 RTP/AVP 0
a=rtpmap:0 PCMU/8000
SIP
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SIP Distributed Architecture
SIP Components
H.323
Location
Server
Redirect
Server
Registrar
Server
SIP/H.323 Gateway
PSTN
User Agent
SIP/PSTN Gateway
Proxy
Server
Proxy
Server
SIP
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SIP Components
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User agent(user application)
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UA Client(caller)
UA Server(called party)
Proxy Server
Redirect Server
Register
SIP
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User Agents
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An application that initiates, receives
and terminates calls.
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User Agent Clients (UAC) – An entity
that initiates a call.
User Agent Server (UAS) – An entity that
receives a call.
Both UAC and UAS can terminate a call.
Both SW and HW available
SIP
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Proxy Server
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An intermediary program that acts as both a
server and a client to make requests on behalf
of other clients.
Requests are serviced internally or by passing
them on, possibly after translation, to other
servers.
Interprets, rewrites or translates a request
message before forwarding it.
Stateless proxy server
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No information about the message is stored
Stateful proxy server
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Forking
reliability
SIP
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SIP Operation in Proxy Mode
User [email protected] on left-hand side
is initiating a call to [email protected]
on right-hand side; Callee registered with his
server previously
Location Server
#6
#7
Callee
INVITE sip:[email protected]
From: sip:[email protected]
To: sip: [email protected] #1
Call-ID: [email protected]
Callee@support
#2
#3
INVITE sip:[email protected]
From: sip:[email protected]
To: sip: [email protected]
#4
Call-ID: [email protected]
OK 200
From: sip:[email protected]
Proxy/Registrar
To: sip: [email protected]
Call-ID: [email protected]
OK 200
From: sip:[email protected] #5
To: sip: [email protected]
Call-ID: [email protected]
ACK [email protected]
[email protected]
[email protected]
Media stream #8
SIP
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Location Server
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A location server is used by a SIP
redirect or proxy server to obtain
information about a called party’s
possible location(s).
Locating service
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LDAP
SQL
SIP
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Redirect Server
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After location service to look up a user,
location information is sent back to the
caller in a redirection class response,
which concludes the transaction.
Unlike a proxy server, the redirect server
does not forward SIP request.
Unlike a user agent server, the redirect
server does not accept or terminate calls.
SIP
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SIP Operation in Redirect Mode
Redirect Server/Location Server
Callee
[email protected]
#1 INVITE [email protected]
#4
[email protected]
#2
#3
302 moved temporarily
Contact: [email protected]
Proxy
#5 ACK [email protected]
[email protected]
#6 INVITE [email protected]
#7 OK 200
#8 ACK [email protected]
SIP
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Registrer Server
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A server that accepts REGISTER
requests.
The register server may support
authentication.
A registrer server is typically co-located
with a proxy or redirect server and may
offer location services.
SIP
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SIP Registration
SIP
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Simplified SIP Call Setup and Teardown
Proxy Server
User Agent
INVITE
Location/Redirect Server
INVITE
302
(Moved Temporarily)
User Agent
Proxy Server
ACK
INVITE
INVITE
302
(Moved Temporarily)
ACK
Call
Setup
INVITE
180 (Ringing)
200 (OK)
ACK
Media
Path
Call
Teardown
180 (Ringing)
200 (OK)
ACK
180 (Ringing)
200 (OK)
ACK
RTP MEDIA PATH
BYE
BYE
BYE
200 (OK)
200 (OK)
200 (OK)
SIP
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SIP and Terminal Mobility
Home Network
HP
REGISTER
#2
Cell 2
Signalling
FP
REGISTER
Cell 1
#1
Visited Network
SIP
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SIP and Terminal Mobility
Home Network
#1
INVITE
HP
#4
#2
INVITE
Cell 2
Signalling
Data
FP
Cell 1
INVITE
#3
Visited Network
SIP
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SIP and Terminal Mobility
Home Network
HP
reINVITE #3
#1
#4
REGISTER
#3
Cell 2
Signalling
Data
FP
REGISTER
Cell 1
#2
Visited Network
SIP
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Personal Mobility
[email protected]
Invest: [email protected]
SIP
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