1. VoIP Signaling Protocols Framework
N. Rajagopal,
MindTree Consulting Pvt Ltd

2. ITU-T and ITU-D Workshop - Bangalore (India), 30-31 August 2001
Agenda
H.323
MGCP/MeGaCo
SIP
Deployment scenarios in India
Summary
ITU-T and ITU-D Workshop - Bangalore (India), August 2001

3. ITU-T and ITU-D Workshop - Bangalore (India), 30-31 August 2001
H.323 Family of protocols
ITU Recommendation
V1 approved in 1996, V2 in 1998
Defines multimedia applications over packet based networks
Originally developed for voice over LANs
Widely deployed
ITU-T and ITU-D Workshop - Bangalore (India), August 2001

4. ITU-T and ITU-D Workshop - Bangalore (India), 30-31 August 2001
H.323 Protocol Stack
Peer to Peer nature
Family of protocols
H.225.0: Call signaling
H RAS
H.245 Conference control
RTP/RTCP for transport
ITU-T and ITU-D Workshop - Bangalore (India), August 2001

5. ITU-T and ITU-D Workshop - Bangalore (India), 30-31 August 2001
H.323 Components
H.323 MCU
H.323
Gatekeeper
H.323
Terminal
LAN
H.323
Gateway
PSTN
ISDN
ITU-T and ITU-D Workshop - Bangalore (India), August 2001

6. ITU-T and ITU-D Workshop - Bangalore (India), 30-31 August 2001
MGCP
Media Gateway Control Protocol
Based on master –slave architecture
“Call agent” – master
“Media gateways” – slave
Call agent
Setups the calls between end points
Media gateways
Does IP <-> voice media conversion
ITU-T and ITU-D Workshop - Bangalore (India), August 2001

7. ITU-T and ITU-D Workshop - Bangalore (India), 30-31 August 2001
MGCP Protocol stack
RFC 2705
Supports “packages” for different applications
DTMF, Trunking
IVR, Media Server
Uses RTP/RTCP for transport
Designed for TCP/IP network
Text based messages
ITU-T and ITU-D Workshop - Bangalore (India), August 2001

8. MGCP Network architecture
Call Agent
Trunking
Gateway
IP Network
IP Network
Trunking
Gateway
Media Gateway
Analog Phones
ITU-T and ITU-D Workshop - Bangalore (India), August 2001

9. ITU-T and ITU-D Workshop - Bangalore (India), 30-31 August 2001
MeGaCo
Media Gateway Control Protocol
Similar to MGCP
More complete
Flexibility
Extensibility
Video support
Other transport support
ATM
ITU-T and ITU-D Workshop - Bangalore (India), August 2001

10. ITU-T and ITU-D Workshop - Bangalore (India), 30-31 August 2001
SIP
Session Initiation Protocol (RFC 2543)
Management of multimedia sessions
Simple, easy protocol
6 messages to get started
Uses RTP for media transport
Lots of extensions being proposed
Standards evolving
Possibility of different services
Good potential
ITU-T and ITU-D Workshop - Bangalore (India), August 2001

11. Comparison between Protocols
H.323
MGCP/MeGaCo
SIP
Purpose
Multimedia conferencing;
Media gateway control
Multimedia conferencing
Defined by
ITU-T
IETF
Complexity
High (multiple protocols: H for signaling, H.225 RAS for GK communication, H.245 for call signaling
Moderate
Simple (6 messages)
Endpoint requirements
Intelligent
Dumb (POTS will do)
PSTN connectivity thru
Gateway
Media Gateway + Signaling Gateway
Outbound proxy
ITU-T and ITU-D Workshop - Bangalore (India), August 2001

12. Comparison between protocols (cont’d)
Number of messages
H.323/100+
MGCP/~10
SIP/6
Type of messages
Binary
Text, readable
Media description
SDP
Voice Transport
RTP
Signaling transport
TCP
UDP
UDP/TCP
Capabilities
H.245 for capabilities exchange to support different transfers
Limited
SDP; limited abilities
Extensibility
Difficult
Easy
Remarks
Legacy; Need to support for today’s networks
May get relegated to trunking after widespread deployment of SIP
Likely Signaling protocol of future!
ITU-T and ITU-D Workshop - Bangalore (India), August 2001

13. Deployment Scenarios in India
H.323
LAN Telephony
Inter office PSTN toll bypass
Remote office connectivity
IP Phones
ITU-T and ITU-D Workshop - Bangalore (India), August 2001

14. Deployment scenarios in India
Office 1
Office 2 IP
Phone
Leased
lines IP
Network PC
Office 3 PC
IP Phone PC
ITU-T and ITU-D Workshop - Bangalore (India), August 2001

15. Deployment scenarios in India
SIP
Experimental
Promises are high
Windows XP support – ubiquitous
Likely areas of usage
Desktops
LAN telephony
ITU-T and ITU-D Workshop - Bangalore (India), August 2001

16. Deployment scenarios in India
SIP
Services
Presence, messaging
Integrated services
Productivity improvement
ITU-T and ITU-D Workshop - Bangalore (India), August 2001

17. Deployment scenarios in India
SIP
Call Centers PC
Phone
PC with SIP
Call Desk
Call Desk PC
Phone
Cabling
Network
Cabling
Network
Cabling
ITU-T and ITU-D Workshop - Bangalore (India), August 2001

18. Deployment scenarios in India
MGCP
Cable telephony
MTU telephony
Set Top
Box (Media
Gateway) TV
Headend
(CallAgent)
Ethernet
POTS
Home
Cable
PSTN
ITU-T and ITU-D Workshop - Bangalore (India), August 2001

19. ITU-T and ITU-D Workshop - Bangalore (India), 30-31 August 2001
Summary
H.323, SIP, MGCP all have their space in VoIP space
Likely coexistence
“Softswitch architecture” to control the elements in VoIP network
“Services” will be key differentiator for customer
CLECs/new generation service providers likely to go for softswitch based solution
ITU-T and ITU-D Workshop - Bangalore (India), August 2001

20. ITU-T and ITU-D Workshop - Bangalore (India), 30-31 August 2001
References
ITU-T and ITU-D Workshop - Bangalore (India), August 2001