Voice over IP: Issues and Protocols. Dhigha D Sekaran Sunil Chintakindi . Voice over IP: An Introduction. Voice over IP is a technology allowing an enterprise to carry voice traffic over an IP data network at substantially reduced bandwidth.
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Dhigha D Sekaran
(c) 1999 Dept of Computer Science, Iowa State University
Voice over IP is a technology allowing an enterprise to carry voice traffic over an IP data network at substantially reduced bandwidth.
It is a a set of facilities for managing the delivery of multimedia information (including fax transmission) in digital form in discrete packets
Frame Relay or
INVITE: initiate call
ACK confirm final response
BYE terminate (or transfer) call
CANCEL cancel “searches” or “ringing”
OPTIONS features supported by the other side
REGISTER register with location service
Terminals:Terminals Provide Real-time communications. They must support voice/video/data communications. The most common H.323 Terminal today is Microsoft net meeting
Gateway: H.323 gateways provide services to H.323 clients so that they can communicate with non H.323 clients. The gateway must provide translations between different transmission formats, communication procedures, and audio codecs
Gatekeepers: They provide call control services for H.323 endpoints, such as address translation and bandwidth management. If they are present in the network the endpoint must use their services. The H.323 standards define mandatory as well as optional services for the gatekeeper.
Multiple Control Units(MCUs): They provide conferences of 3 or more endpoints
IETF MMMUSIC ITU_T
Large and small conference MCU based control unit
Firewall friendly complex, multiple protocols
Multicast signaling -----
Personnel mobility Not(yet)
SSL, HTTP security work in progress
Post dial delay:1.5RTT 8.5RTT
Text based binary based.
60+ pages 200 complex pages!!!
Easy implementation , Debugging very complex
Can be implemented using Java, Tcl,Perl mostly only in C/C++
SDP(Session Description Protocol) Intended for describing multimedia sessions
RSVP(Resource Reservation Protocol) for prioritization of voice packets
RTP(Real time Protocol) for sequencing of packets
H.225: Specifies messages for call control including signaling, registration and admission
H.245-Specifies messages for opening and closing channels
H.261-Video codec for audiovisual services at 64kbps
H.263- New Video codec for video over POTS
- can give voice traffic higher priority
- enforces QoS based class, not on length of packet
- High performance architecture that can scale to billions of ports
- Reliable data networking
- Provide PSTN quality (voice and latency)
- Needs open standards and interfaces
- Natural transition and migration
- Billing/ rating solutions, Network management