Projekt (0)

Tallinna Tehnikaülikool Raadio- ja sidetehnika instituut
Projekt ainetes ,,IRT0030 Andmeside"
ja
,,IRT0100 Kommunikatsioonivõrkude struktuurid ja teenused"
teemal
« VoIP teenus»
Üliõpilane: Ruslan Karpovits Õpperühm: IATM Matrikli nr: 050829 Õppejõud: Avo Ots
Tallinn
2008 Author 's word This project is written to show some interesting aspects of working with VoIP ( Voice over Internet Protocol ) service. The project briefly describes the process of finding a solution for based VoIP problem and its realization.
-2- Contents
Introduction .............................................................................................................................. - 4 -
Mission ....................................................................................................................................... - 5 -
Solution...................................................................................................................................... - 5 - Scheme .................................................................................................................................... - 5 - Components ............................................................................................................................ - 5 - Configuration ......................................................................................................................... - 7 - Monitoring.............................................................................................................................. - 8 - Price ..................................................................................................................................... - 10 -
Conclusion ............................................................................................................................... - 10 -
Referencies .............................................................................................................................. - 11 -
-3- Introduction VoIP is a solid technology available since some years that allows people to communicate via voice using the IP protocol instead of telephone lines. Unfortunately this technology has been relegated in a niche market due to several factors such as proprietary standards, high price tag, limited integration with existing telephony environments. However in the last couple of years the situation changed dramatically since some open source tools such as asterisk as well as low- cost VoIP telephone adapters and services become available. In fact , today it is quite common for internet providers to provide their customers VoIP calls at very low cost, if any, in addition to standard xDSL connectivity.
The VoIP uses Internet protocol (IP) to send digitized voice traffic over the Internet or private networks . An IP packet consists of a train of digits containing a control header and a data payload. The header provides network navigation information for the packet, and the payload contains the compressed voice data.
While circuit -switched telephony deals with the entire message , VoIP-based data transmission is packet-based, so that chunks of data are packetized (separated into units for transmission), compressed, and sent across the network--and eventually re-assembled at the designated receiving end. The key point is that there is no need for a dedicated link between transmitter and receiver.
Packetizing voice data involves adding header and trailer information to the data blocks. Packetization overhead (additional time and data introduced by this process) must be reduced to minimize added latencies (time delays through the system). Therefore , the process must achieve a balance between minimizing transmission delay and using network bandwidth most efficiently --smaller size allows packets to be sent more often, while larger packets take longer to compose. On the other hand , larger packets amortize the header and trailer information across a bigger chunk of voice data, so they use network bandwidth more efficiently than do smaller