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New Member

Configuring e1 controller clocking in unframed mode

Hi

I have two cisco 2800 series routers and each has a dual e1 card (VWIC-2MFT-G703). Both routers are WAN connected via G.SHDSL The e1 controllers are configured in unframed mode. I originally configured both routers to obtain clocking from the line (providers network) at both ends. There were some issues with the link in terms of high error rates and was fixed but now the service provider is insisting that one side must provide clocking (one router end configured to source the clocking). Originally, they specified to configure the routers to obtain clocking from the line.

My questions are:

1. Wouldn't you normally configure the interfaces to follow the clocking provided by the ISPs network at both ends with an e1 unframed service?

2. Is the scenario of having one router end provide the clocking to the provider's network and the other router end follow the line (clocking from network) valid? (I suppose you would do this in situations when the routers are connected back-to-back using a crossover cable)

3. In e1 unframed mode, do you really need clocking? There is a third clocking option, which is free running. In what situations would you use this?

router(config)#control e1 0/0/0

router(config-controller)#clock source ?

free-running Free Running Clock

internal Internal Clock

line Recovered Clock

I need to know as there are potential line problems and I need to ensure that clocking is not the issue. I don't trust the ISP engineers (saying one thing and then the other, then blaming the routers for the problems)

6 REPLIES
Silver

Re: Configuring e1 controller clocking in unframed mode

What I believe the clock source design is depending on the provider service. If they request the router to be clocksource then try to follow it ant test.

Once the link is upa dn carry the line test by provider and the user(you), then there should be no problem.

In my experience, I tried to configure both internal and external clock but never tried free-running. There is no specific way that provider should provide the clock. Remember to ask the provider to test the line to ensure it is problem-free.

Finally, they cannot blame the router because they should provide the sample config. to you to match w/ their service. And you can ask them to prove why there is problem in the router.

Hope this helps.

New Member

Re: Configuring e1 controller clocking in unframed mode

Thank you very much for replying.

I was really trying to find what the majority of clocking was set up out there, and it seems from my other inquiries, that the ISP will usually provide the clocking. So I am not sure why this particular ISP I am having issues with has asked for one end to provide the clocking (router provides clocking to the isp), whereby the initial requirement they told us was to get the clocking from the line, on both ends.

The provider has made up its mind that its a router problem. What I needed to know is other things that can be done to ensure that the router configs are sound and enough tests and stats to show them the source of the problem is the line.

Silver

Re: Configuring e1 controller clocking in unframed mode

IC. You can ask the provider to conduct the loopback & burst test to ensure their line is working & error-free. And if they insist there is problem in the router, ask them to bring one and prove the line is working.

You are difficult to prove your router is healthy, so you can only ask them to provide it to isolate the problem.

Hope this helps.

Re: Configuring e1 controller clocking in unframed mode

Often telco's do not interfere with clock of e1 circuits, which means that one of your routers have to provide clock (clock source internal), while other have to recover clock from the line (clock source line). This is especially true for unframed circuits.

Indirectly clock sync problems can be seen as moderate to high error rate when interface is loaded, but show almost no errors when there is no load on the interface.

New Member

Re: Configuring e1 controller clocking in unframed mode

many thanks for the info on this thread. There were other issues related to this,so its been a while, but thanks for confirming that in most cases, for an unframed circuit, it does make sense that one end (A) provides clocking and the other end (B) recovers from that line, which is sourced from the A end.

I would be interested to find out though what would be the rate of errors that would be considered normal or expected. What is typically seen in practice. Is there a standards document that pertain to expected error rates for E1 data services. Just need to know when we baseline/trend the rate, we can find which point we take notice and at what level we ignore.

Silver

Re: Configuring e1 controller clocking in unframed mode

Sorry, I have no such doc. on hand to tell the benchmark of error rate. What I suggest if the error rise continuously, there should be some problem. And you also need to compare the overall ratio between byte/packet and the no. of error. If the error is only 1 or 2 %, then it should be fine. Moreover, better clear the counter before monitor the error rate.

Hope this helps.

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