Tutorial HGS/SIP

Informations

• Publié par: Kanic
• Nombre de lectures: 125
• Langue: Catalan

Extrait

hgs/SIP Tutorial 1
The Session Initiation Protocol
(SIP)
Henning Schulzrinne
Dept. of Computer Science
Columbia University
New York, New York
(sip:)[e-mail]
May 2001hgs/SIP Tutorial 2
Overview
protocol architecture
typical component architectures
protocol operation
reliability
features
security
May 2001hgs/SIP Tutorial 3
Introduction
core protocol for establishing sessions in the Internet
transports session description information from initiator (caller) to callees
allows to change parameters in mid session
terminate session
May 2001hgs/SIP Tutorial 4
Protocol architecture
Languages/APIs
JAIN CPL voiceXML
servlets
Parlay
sip−cgi
Signaling
Directory/Discovery peer−to−peer
MGCP
LDAP SIP
DNS/enum TRIP SDP RTSP
H.248
PINT
SLP SPIRITS
master−slave
QoS Transport
RTP TLS
DiffServ IntServ
SCTP
May 2001?
hgs/SIP Tutorial 5
SIP applications
setting up voice over IP calls
setting up multimedia conferences
event notification (subscribe/notify) IM and presence
text and general messaging
signaling transport
May 2001hgs/SIP Tutorial 6
Personal mobility
SIP uses email style addresses to identify users
[e-mail]
(also used by [e-mail])
yahoo.com
tel:[phone]
[e-mail]
[e-mail]
[e-mail]
tel:[phone]
columbia.edu
[e-mail]
[e-mail]
May 2001hgs/SIP Tutorial 7
SIP addressing
typically, same as user’s email address:
[e-mail]
12125551212@gateways r us.com
written as URL, e.g.,sip:[e-mail]
also can use tel URLs for telephone numbers, e.g.,tel:[phone] or
fax:[phone]
May 2001hgs/SIP Tutorial 8
Building blocks
SIP user agent IP phone, PC, conference bridge
SIP redirect server returns new location for requests
SIP stateless proxy routes call requests
SIP (forking) proxy routes call requests
A@
B@
C@
SIP registrar maintains mappings from names to addresses
May 2001hgs/SIP Tutorial 9
Back to back UA (B2BUA)
two (or more) user agents, where incoming calls trigger outgoing calls to
somebody else
also, “third party call control” (later)
useful for services and anonymity
SIP UA1 (UAS) SIP UA2 (UAC)
INVITE b2b
INVITE callee
200 OK
200 OK
May 2001hgs/SIP Tutorial 10
Maintaining state in SIP entities
Stateless: each request and response handled indepdently
(Transaction) stateful: remember a whole request/response transaction
Call stateful: remember a call from beginning to end
May 2001