Understanding SIP
Dorgham Sisalem
Jiri Kuthan
Mobile Integrated Services
GMD Fokus
Sisalem,kuthan@fokus.gmd.de
Attention!
Update Notice
Authors are committed to ongoing improvement of this tutorial.
Thus, this version may include updates and differ slightly from
printed version. You can get the updated version at the following
address:
http://www.fokus.gmd.de/mobis/siptutorial/
Frequent Misunderstandings
There are numerous issues that turned out to be difficult to
understand. Such issues are labeled with the symbol bellow. Please,
pay special attention to them.
Frequently
Misunderstood
Issue
Outline
It’s IP Telephony
Who is who
IP Telephony Basics
Protocol ZOO
SIP Signaling
Multimedia Communication
Advanced Signaling
Programmability
QoS Preconditions
Mobility and 3gpp
SIP vs H.323
Robustness
Security
Legacy
Political Issues
Status Update
Conclusions
References
The Big FAQ
Q: You are too IP-centric, aren’t you?
A: Of course, we are.
Internet
telephony (which has Internet in its name) is
about IP.
IP telephony runs on top of IP and utilizes the IP service model.
It is not about re-engineering PSTN -- PSTN is good enough.
SIP is much more similar to HTTP rather than to legacy
signaling both in terms of service model and protocol
design.
Appeals of IP Telephony
Saving, but ...
⌧lower QoS
⌧Telcos lower prices (1998: Berlin-Prague, 99 Pf/Min, 1999:
39 Pf/Min, 2000: 32 Pf/Min call-by-call, 23 Pf/Min
preselection)
Internet Service integration
IP is the first true Integrated Services Digital
Network
Major argument: convenience
In IP, you are your own master
Open service market: access providers located across
the globe; even you can be a provider.
Programmability: programs by user as well as third
p
arties.
