05-04-2010, 11:04 PM
voip.ppt (Size: 261 KB / Downloads: 446)
What is VOIP ?
Voice over Internet Protocol transfers voice through IP packets through the Internet. VoIP can use special
hardware or a PC environment to achieve this purpose. IP Telephony is defined as the use of networks to
transmit both voice and data packets
How does VOIP works:
Voice (source) - - ADC - - - - Internet - - - DAC - - Voice (dest)
DEFINITIONS OF IMP TERMS
ZoneThe collection of a gatekeeper and the endpoints registered with it is called a zoneNetwork AddressFor
each H.323 entity, a network address is assigned and this address uniquely identifies the H.323 entity on the
network TSAP Identifier These TSAP identifiers allow multiplexing of several channels sharing the same network
address
PACKET FREQENCY
Packet frequency is the number of packets containing voice samples which are sent per second
Components of H.323( it is a terminal)
Different Terminals
Gateways
Gatekeepers
H.323 TERMINAL SUPPORTING OTHER PROTOCOLS
H.245 : allowing the usage of the channels.
Q.931: call signaling and setting up the call
RTP: carries voice packets
RAS: interacting with the gatekeeper
Interface between the PSTN and the Internet
Translator : H.225 to H.221 or audio to video
GATEKEEPERS
Controls the end points under its zone
Function
Address Translation
Admissions Control
Call signaling
Call Authorization
Bandwidth Management
H.323 PROTOCOL STACK (layers)
CALL SETUP IN H.323(working)
Endpoint enters the call setup phase
Discovering a gatekeeper which would take the management of that endpoint
The capability exchange takes place between the endpoint and the gatekeeper
Registration of the endpoint with its gatekeeper
The call is established
MULTIPOINT CONTROL UNITS (MCU)
SESSION INITIATION PROTOCOL (SIP)
It is an application layer control protocol for
creating, modifying and terminating sessions with one or more participants.
SIP can also invite participants to already existing sessions, such as multicast conferences.
Media can be added to (and removed from) an existing session.
SIP transparently supports name mapping and redirection services, which supports personal mobility “
SIP MESSAGES(commands)
INVITE: for inviting a user to a call
BYE: for terminating a connection between the two end points
ASK: invitation for reliable exchange of messages
OPTIONS: for getting information about the capabilities of a call
REGISTER: gives information about the location of a user to the SIP registration server.
CANCEL: for terminating the search for a user
SAMPLE SIP OPERATION
SUPPORTING PROTOCOLS(along SIP)
VOIP AND PHONE
VoIP Networking “ The Problem
A VoIP network can grow out of control and needs a solid control layer and network management system to maintain
revenue assurance and allow further growth
Configurations in each gateway are complex and prone to error
Multiple sources of CDRs “ complex CDR analysis and billing
No control over traffic demand “ high demand causes gateway overload and lost revenue
Multiple gateways and no common routing point
CONCLUSION
Like everything else, as the technology changes so At first, only a few companies like Cisco and Lucent offered
VoIP services, but the large telecommunications carriers “ such as AT&T and Sprint -- are catching on
VoIP is predominately used for personal instead of enterprise-wide use, but will the people who use it.
CONCLUSION(contd¦)
VoIP offers opportunity to increase robustness and decrease costs
So future of communications is IP TELEPHONY.
THE END
THANK YOU