Jean-Yves Avenard wrote:
Hello
On 15/05/2005, at 12:00 AM, Colin Anderson wrote:
wierd. Im running fc2 2.6.8 smp no problems. Could be timing slips on your
PRI, happened to me until I looked hard at the PRI
So you turned off Hyperthreading on your linux box or not??
What could I do to check if my PRI has timing slips? I have to say that my knowledge in this area is close to zero. The extent of my knowledge was to connect a TE110P card, configure it and run it. That's it
Jean-Yves
In most cases the slips on T1s and E1s are because people have carefully configured their system to cause them. Probably because there is no clear explanation around of the right way to do things. Their careful configuration generally consists of ensuring they have the following lines in their zaptel.conf file (E1 example):
span=1,0,0,cas,hdb3,crc4 span=2,0,0,cas,hdb3,crc4 span=3,0,0,cas,hdb3,crc4 span=4,0,0,cas,hdb3,crc4
This ensures they do not listen to any external source's opinion about clock speeds. As they centre of the universe, their Asterisk box expects the 4 systems connected to their 4 E1s to fall in line with the clock speed of the Asterisk box. (here's a clue: a PSTN switch contains an atomic clock as its clock source, and believes everyone else's clock it too flawed to listen to).
Other people carefully configure their zaptel.conf file to contain lines like (again, an E1 example):
span=1,1,0,cas,hdb3,crc4 span=2,2,0,cas,hdb3,crc4 span=3,3,0,cas,hdb3,crc4 span=4,4,0,cas,hdb3,crc4
and then attach spans 1, 2, and 3 to a PBX and span 4 to the PSTN. So, their primary source of clock is some grotty PBX, as it is listed as the number 1 option for obtaining a clock. They expect the PSTN to fall in line with the PBX's clock. Well, if the PBX has actually locked directly to the PSTN by another E1, that might work out. However, in most cases the Asterisk box is playing piggy in the middle, and the PBX should be syncing to the clock it gets from the Asterisk box.
The right thing to do is to sync to the PSTN. The E1s connected to the PSTN should be listed as the lowest numbered clock sources, starting from 1. Places you never want to sync to should be set to zero.
Regards, Steve
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