asynchronous transfer mode (ATM), the between source telephone and destination switching fabric designed to handle voice, telephone. I will continue with my analogies data, and video traffic. Such network to explain how your voice gets transported optimization will go a long way toward across the Internet. eliminating network congestion and the In terms of H.323 there is a trade off associated packet loss. The Internet industry between call quality and bandwidth, in also is tackling the problems of network general the higher the quality the greater the reliability and sound quality on the Internet bandwidth required through the gradual adoption of standards. During the call setup portion of H.323 the Standards-setting efforts are focusing on the phones have to decide which speech three central elements of Internet telephony: encoder/decoder to use when they send the the audio codec format; transport protocols; speech to the other phone, Bill and Sally and directory services. both have phones that support G.723.1, G.711 and G729. H.323 Call Sequence: The main difference between each of As such, H.323 addresses the core these encoders is the amount of bandwidth applications by defining how they use, G.711 uses 64kbit/s and G.723.1 delay-sensitive traffic, (i.e., voice and can use as little as 5.3kbit/s. Although it video), gets priority transport to ensure would seem obvious to use the encoder with communications service over the the lowest bandwidth, there is a loss of Internet. (The H.324 specification defines quality with a lower bandwidth.. At the the transport of voice, data, and video over same time a stream of G723.1 encoded voice regular telephony networks, while H.320 data starts being sent from each phone to the defines the protocols for transporting voice, other phone. data, and video over integrated services How VoIP works part 4 :Hear the digital network (ISDN). Quality. The performance of the speech encoders at How VoIP works part 3: Encoding each end, the number of packets lost on route, Latency and Jitter. The call control part of H.323 sets up the I have already talked about the parameters for the full duplex voice path encoders in the previous section. I also
asynchronous transfer mode (ATM), the switching fabric designed to handle voice, data, and video traffic. Such network optimization will go a long way toward eliminating network congestion and the associated packet loss. The Internet industry also is tackling the problems of network reliability and sound quality on the Internet through the gradual adoption of standards. Standards-setting efforts are focusing on the three central elements of Internet telephony: the audio codec format; transport protocols; and directory services. H.323 Call Sequence: As such, H.323 addresses the core applications by defining how delay-sensitive traffic, (i.e., voice and video), gets priority transport to ensure communications service over the Internet. (The H.324 specification defines the transport of voice, data, and video over regular telephony networks, while H.320 defines the protocols for transporting voice, data, and video over integrated services digital network (ISDN). How VoIP works part 3: Encoding The call control part of H.323 sets up the parameters for the full duplex voice path between source telephone and destination telephone. I will continue with my analogies to explain how your voice gets transported across the Internet. In terms of H.323 there is a trade off between call quality and bandwidth, in general the higher the quality the greater the bandwidth required During the call setup portion of H.323 the phones have to decide which speech encoder/decoder to use when they send the speech to the other phone, Bill and Sally both have phones that support G.723.1, G.711 and G729. The main difference between each of these encoders is the amount of bandwidth they use, G.711 uses 64kbit/s and G.723.1 can use as little as 5.3kbit/s. Although it would seem obvious to use the encoder with the lowest bandwidth, there is a loss of quality with a lower bandwidth.. At the same time a stream of G723.1 encoded voice data starts being sent from each phone to the other phone. How VoIP works part 4 :Hear the Quality. The performance of the speech encoders at each end, the number of packets lost on route, Latency and Jitter. I have already talked about the encoders in the previous section. I also
49147559-VOICE-OVER-IP.docx