NETW320 – Converged Sites with Research laboratory
Lab #7 Title: CODEC Selection for any WAN
A codec is a device capable to perform encoding and decoding on a digital sign. Each codec provides a several level of speech quality. The reason for this is that codecs work with different types of compression techniques in in an attempt to require much less bandwidth. A lot more the compression, the fewer bandwidth you will need. However , this will ultimately be at the expense of sound quality, while high-compression/low-bandwidth algorithms will not have the same voice top quality as low-compression/high-bandwidth algorithms. The next table reveals three standard codec types along with their related Coder Type, Bit Price, Frame Size Delay, and appearance Ahead Hold off. These particular three were selected because these are the ones we will use in this laboratory, but there are others. TERSEBUT Recommended Wait Values/G. 114
Shape Size Wait (milliseconds)
Look In advance Delay (milliseconds)
almost eight kbps
G. 723. 1
5. a few kbps
7. a few
One common scale utilized to determine the caliber of sound produced by various codecs is the imply opinion score (MOS). This standard is founded on a level from you to 5, exactly where 1 is incredibly poor and 5 is fantastic. Here is a prevalent table utilized to rate ideals of MOS.
Listening Top quality
Moderate Hard work
a couple of
No Meaning Understood
In this lab, you will build a wide-area network that will incorporate several LANs spread across the nation and linked via the Internet with two types of traffic: data and tone. You will configure three situations where the info and voice traffic made will be placed constant. The only parameter that you will alter is definitely the type of codec used. In the first situation, the tone traffic uses G. 711 (PCM); inside the second circumstance, the tone traffic uses G. 729 (CS-ACELP); as well as the third situation, the voice traffic uses G. 723. 1 (ACELP). By keeping the traffic generated for the data and voice users constant, and only changing the codec beliefs, we will be in a position to see how the varying tad rate in the specific codecs used will affect the end-to-end delay to get the data visitors, the end-to-end delay to get the tone traffic, as well as the packet hold off variation to get the words traffic for any wide-area environment. Motivation
Deciding on what codec to work with is a tradeoff between band width and talk quality; a lot more bandwidth the codec uses, the better the presentation quality will be. Here are the codecs all of us will use, with their corresponding WITHOUT DIFFICULTY values. Codes
G. 711 (PCM)
G. 729 (CS-ACELP)
G. 723. you (ACELP)
However , this is not the sole factor that must be considered. Delay will significantly affect the quality of tone of voice traffic because it is real-time traffic. Words and responses to words must be received within a coherent and timely way for the voice discussion to be suffered by the users. Here is a table with ITU-T recommendations for the entire one-way delay times intended for voice visitors. ITU-T Suggest Acceptable Verified Overall Wait Times/G. 114 Range in Seconds
Range in Milliseconds
0 to 0. a hundred and fifty
0 to a hundred and fifty
Satisfactory for most customer applications.
0. 150 to zero. 400
150 to 400
Acceptable, given that administrators know about the tranny time and the effect it has within the transmission quality of user applications. Previously mentioned 0. four hundred
Previously mentioned 400
Unacceptable pertaining to general network planning reasons: it is acknowledged that in some exceptional cases this limit is surpassed.
The table displayed in the launch lists a Frame Size Delay and a Look Ahead Delay. The frame size refers to enough time it takes the sender to transmit a frame. For complex compression algorithms that reduce band width, this wait can...
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