How Do I Configure Clocking?
- Nathaniel Halbrooks
Per Port Configuration
Below is all the different scenarios that can occur for a single T1/E1/J1 link. Now remember there can NOT be no clock on a T1/E1/J1 link and there can not be two clocks. Also note step 4 is the typical setup when connecting to the telco.Â
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The link in this scenario will NOT connect to the far end equipment because there has to be one clock on a T1/E1/J1 link.
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The link in this scenario will connect to the far end equipment because there is a clock on the line.
The link in this scenario will connect to the far end equipment because there is a clock on the line. But the issue here will be that there is two different clocks on the line. This means both ends will be syncing from their own clock which will be slightly different. You may not notice an issue at first but over time the clocks will change a bit and you will have sound issues.
The link in this scenario will connect to the far end equipment because there is a clock on the line. This is also your typical setup for connecting to a telco.
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Per Card Configuration
Each Sangoma card requires a single clock per card. The reason for this is it increases our efficiency because each port can be handled in a single interrupt rather a separate interrupt per card. So this single interrupt for each port approach allows us to run an A108 with out adding a great deal of load to the system.
Now if the case where two clocks occur this can cause issues that will result in noise and faxing problems. Now you can get two clocks in two scenarios. The first is you have multiple telco's connected to one card; now in some cases this is not an issue if the telcos are providing you with the same clock. Often in North America the telco's all provide the same clock so normally it is not something to worry about. The second way it can occur is if you are providing clocking for a channel bank or a PBX; this is because you receive one clock from the telco and you need to provide another to channel bank/pbx. Below is how to correctly setup the card in that scenario.
In the setup below there is one telco link and three channel bank/pbx links. Now in the /etc/wanpipe/wanpipe*.conf files for this senario to occur the clocking will be set as shown below. So this means port 2-4 the clock is provided from the clock on the card its self and port 1 gets it's clock from the telco; so this results in two different clocks. Now when using our configuration scripts this will occur because NORMAL clocking was selected for port 1 and ports 2-4 MASTER was selected but the clocking source was "Free run" rather then "Port 1".
This Setup Is Wrong; Just For Example
Port 1:Â Â Â Â TE_CLOCKÂ Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â = NORMAL
               TE_REF_CLOCK                   = 0
Port 2-4:Â TE_CLOCKÂ Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â = MASTER
               TE_REF_CLOCK                   = 0
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In the setup below there is one telco link and three channel bank/pbx links. Now in the /etc/wanpipe/wanpipe*.conf files for this senario to occur the clocking will be set as shown below. So this means port 2-4 the clock is provided from the clock on port 1 which is the telco's clock; so this results in only a single clock. Now when using our configuration scripts this will occur because NORMAL clocking was selected for port 1 and ports 2-4 MASTER was selected but the clocking source was "Port 1" rather then "Free run". This scenario here is correct because there is only one clock as shown in the picture below and the fix in the configuration was "TE_REF_CLOCK =1" rather then "TE_REF_CLOCK =0" for ports 2-4.
This Setup Is Correct
Port 1:Â Â Â Â TE_CLOCKÂ Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â = NORMAL
               TE_REF_CLOCK                   = 0
Port 2-4:Â TE_CLOCKÂ Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â = MASTER
               TE_REF_CLOCK                   = 1
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