You are evaluating the implementation of a SIP trunk in the main office to support the planned Lync Server 2010 deployment. You need to calculate the minimum amount of bandwidth required for PSTN calls. How much bandwidth is required on the network connection to the SIP trunk?
A.
33.98 Mbps
B.
58.40 Mbps
C.
41.80 Mbps
D.
25.29 Mbps
Explanation:
SIP Trunk Peak Bandwidth = Max Simultaneous Calls x (64 kbps + header size). Header size is 20 bytes maximum. (http://technet.microsoft.com/en-us/library/gg425743.aspx)Lync Server 2010 supports only the following codecs:
* G.711 a-law (used primarily outside North America)
* G.711 -law (used in North America)
Can somebody explain how to calculate the answer?
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WRONG ANSWER. IS THE B
http://technet.microsoft.com/en-us/library/ee323608(v=office.13).aspx
http://technet.microsoft.com/en-us/library/gg425743.aspx
In this articles, we can see the formula Microsoft uses:
SIP Trunk Peak Bandwidth = Max Simultaneous Calls x 80kbps
so, if we convert the bandwidth from mbps to kbps
33.98 Mbps = 33980 Kbps / 80 Kbps = 424.75 Simultaneous calls, WRONG
58.40 Mbps = 58400 Kbps / 80 Kbps = 730 Simultaneous calls, OK
41.80 Mbps = 41800 Kbps / 80 Kbps = 522.5 Simultaneous calls, WRONG
25.29 Mbps = 25290 Kbps / 80 Kbps = 316.125 Simultaneous calls, WRONG
Simultaneous calls must be an integer, so the right answer is B
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Additionaly the case study has the following table with typical bandwidth usage:
————————-
Codec Bandwidth
—– ———
G.711 59.8Kbps
G.722 42.8 Kbps
RT Audio (8 KHz) 25.9 Kbps
RT Audio (16 KHz) 34.8 Kbps
————————-
Calculation for G7.11 (used by SIP-trunks):
(1000*59,8Kbps)/1024=58,3984375Mbps -> rounded to 58,40Mbps
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