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It's an old hand-rule, nothing more.<BR>
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The ideal situation would be 1 byte - 0.125 ms latency in switching, but this means a computer masturbating at 8000 interrupt a second - and can you imagine what this will do with your CPU?<BR>
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Write a small test application that perform memcpy operations and calculate the transer rate.<BR>
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When test on 1 byte, 5 bytes, 10 bytes 25 bytes 50 bytes<BR>
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What you will see is that the transfer rate increase with the size of the packet - 50 byte is ca 50 byte faster than 1 byte in x-fer.<BR>
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Now test with 100 bytes 250 bytes 500 bytes 1000 bytes etc<BR>
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And you will see that little has changed from ca 50 bytes in xfer rate.<BR>
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48 byte basicaly is a good trade between latency and cpu usage. The test might vary dependent on processor , but....<BR>
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10 ms is however more or less the same, and might be a better number today. It goes for 711, 729 and 723 ...<BR>
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Jan<BR><BR><BR>
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From: brian@freeswitch.org<BR>To: freeswitch-dev@lists.freeswitch.org<BR>Date: Fri, 30 Jan 2009 09:35:44 -0600<BR>Subject: Re: [Freeswitch-dev] FreeSwitch + ISDN + analog phone adapters - status<BR><BR>Can you elaborate on this G.711 at 6ms? I have never seen this odd number.<BR>
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<DIV>/b</DIV>
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<DIV>On Jan 30, 2009, at 9:30 AM, Jan Berger wrote:</DIV><BR class=EC_Apple-interchange-newline>
<BLOCKQUOTE><SPAN class=EC_Apple-style-span style="WORD-SPACING: 0px; FONT: 13px Verdana; TEXT-TRANSFORM: none; COLOR: rgb(0,0,0); TEXT-INDENT: 0px; WHITE-SPACE: normal; LETTER-SPACING: normal; BORDER-COLLAPSE: separate">hi Hans,<BR> <BR>The standard for a PABX on G.711 is 6ms packaging of data - this is 48 byte per channel. If you go higher than this you start getting to much latency, if you go lower than this you start using to much CPU.<BR> <BR>400 byte is 50ms, meaning we have spent a lot of the latency budget already here, but this shoud be run-time configurable per channel as per need.<BR> <BR>- G.711 6 ms<BR>- IVR is 250 ms<BR>- 729 10 ms<BR>- 723 30 ms<BR> <BR>etc.<BR> <BR>You need to take into consideration that you are on a system with 8, 16 or 32 E1's of whick some is running IVR, others SIP, others swicthing back out on a different E1 etc.<BR> <BR>Jan<BR> </SPAN></BLOCKQUOTE></DIV><BR></DIV><br /><hr />Get news, entertainment and everything you care about at Live.com. <a href='http://www.live.com/getstarted.aspx ' target='_new'>Check it out!</a></body>
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