924E timing issues

[wfjones1]

I have two T-1's connected to a 924e. I have the first one on T1 0/1 configured as timing-source t1 0/1 primary and t1 0/2 as secondary. These are not in an MLPPP bundle or MFT bundle. These are separate T-1's

timing-source t1 0/1

!

timing-source t1 0/2 secondary

!

I am seeing these timing errors on the router. (actually is see this on multiple routers that we are adding second T-1's to.) Is there a different configuration I should be using?

I want to receive clock from the network and not be internal. But even if I reverse it and choose the second T-1 as primary and the first as secondary the CLI messages just reverse and point to the first T-1

2014.03.06 20:12:44 T1.t1 0/2 ES 15 min threshold exceeded

2014.03.06 20:15:15 T1.t1 0/2 CSS 15 min threshold exceeded

interface t1 0/1

  tdm-group 1 timeslots 1-24 speed 64

  no shutdown

!

interface t1 0/2

  tdm-group 1 timeslots 1-24 speed 64

  no shutdown

interface fr 1 point-to-point

  frame-relay lmi-type ansi

  no shutdown

  cross-connect 1 t1 0/1 1 frame-relay 1

!

!

interface fr 2 point-to-point

  frame-relay lmi-type ansi

  no shutdown

  cross-connect 2 t1 0/2 1 frame-relay 2

[jayh]

What is on the other end of these T1s?  Can you provide a network diagram or narrative describing how the units are connected?

Here's a general overview:

A T1 circuit is a point-to-point (even if one side goes to "the Internet").  Each T1 circuit should have exactly one source of clock.  It clocks from one side and the other side synchronizes to that.  If both sides are clocking internally or from another source, you will get clock slips.  If both sides clock from the T1 itself, then there is no authoritative clock and the circuit will work for a while [where "while" can be seconds, days, or months] and then fail completely and (usually) recover by itself.

The TA900 series can have only one authoritative clock source for the chassis at any one time.

This means that if T1 0/1 is the primary clock source and is up, and you have a T1 0/2 connected, then the TA900 will try to clock T1 0/2 internally with the clock it recovers from T1 0/1.  If the other side of T1 0/2 is also sourcing clock, then you'll have slips.  This sounds like your exact problem.

If your scenario is like this:

CARRIER---->TA900#1-----link---->TA900#2

Then set the first TA900 to clock from the carrier with internal as secondary, and set the second TA900 to clock from the first one with internal as secondary.

If your scenario is like this:

CARRIER A------->TA900<------CARRIER B

Then you need to choose one carrier to clock from and convince the other carrier to set their router to clock from you.  First-line people at most carriers won't understand this issue, but generally there will be someone clueful that you will be able to reach if persistent.  It's a non-standard configuration for them but most will get it if you tell them that your equipment is connected to a second clock source.

In this case, set your TA900 to source from the T1 of the carrier that is clocking to you (normal setup) with a secondary of internal.  Ask the other carrier to take clock from you.  If your link to the primary carrier fails, then your TA900 will revert to its internal clock and your second T1 will remain in sync because the second carrier is clocking from you.

[wfjones1]

Jayh,

    First off thank you for your response.

In this scenario both T-1's are connected to a Verizon MPLS PE router on their MPLS cloud. They won't take clock from me on one of my T-1's. How come, if I set the timing source for one as primary and the other as secondary, that won't work?  It would seem that if the second T-1 is set to secondary it would get clocking from the first and then if that T-1 fails it should take over the clock?

[wfjones1]

and sorry for the separate response but from what the system status shows this should be telling me that the primary clock source would be t-1 0/1 and is active.. if that failed the t1 0/2 should take over correct?

<hostname removed> uptime is 15 weeks, 1 days, 20 hours, 46 minutes, 0 seconds

System returned to ROM by External Hard Reset
Current system image file is "T900E2A-A4-05-00-E.biz"
Boot system image file is "T900E2A-A4-05-00-E.biz"

Power Source:  AC
System primary clock source configuration:  t1 0/1
System secondary clock source configuration:  t1 0/2
System current active clock source:  t1 0/1

T1 Framer Version: QuadFalc56 V3.1

[jayh · Accepted solution]

wfjones1 wrote:

Jayh,

    First off thank you for your response.

In this scenario both T-1's are connected to a Verizon MPLS PE router on their MPLS cloud. They won't take clock from me on one of my T-1's. How come, if I set the timing source for one as primary and the other as secondary, that won't work?  It would seem that if the second T-1 is set to secondary it would get clocking from the first and then if that T-1 fails it should take over the clock?

You'll need to get more aggressive with Verizon. At times you just need to keep demanding a supervisor until you get someone with some clue.

The problem is almost certainly that both T1s are not connected to the SAME MPLS PE router, and that the clocks from the two routers are slightly different.  Your setup is like the second example in my previous reply. 

The TA900 uses a single T1 clock for the entire chassis.  This clock can come from a T1 line or be generated internally. There is a backup capability, so if you choose a T1 as your primary clock source and that T1 goes down, it can choose a second T1 or fall back to the internal oscillator.

In your scenario, because the incoming clocks are slightly different, whichever T1 you choose as primary will cause slips on the other.

Your options are:

• Convince Verizon to take clock from you on one of the T1s.
• Convince Verizon to feed both circuits to you from the same router.
• Convince Verizon to connect both routers to an accurate BITS clock source.
• Use two devices at your site, one for each T1, and connect them together as Ethernet.
• Use a device at your site that is capable of accepting two independent clock sources.

Convincing Verizon to take clock from you is do-able, I've done it, but you need to be forceful and persistent.  There are people within Verizon who understand these things but there are multiple layers of gatekeepers whose job it is to keep anyone with clue from interacting with customers.

[jayh]

wfjones1 wrote:

and sorry for the separate response but from what the system status shows this should be telling me that the primary clock source would be t-1 0/1 and is active.. if that failed the t1 0/2 should take over correct?

Yes, that's correct.  The issue you're having is that because T1 0/1 is primary and active, it is being used as the clock for the entire chassis, including sourcing clock on T1 0/2.  And Verizon's clock on T1 0/2 is also being sourced from them, and is slightly different from the clock they are providing on T1 0/1.

[Anonymous]

Hello,

I went ahead and flagged the "Correct Answer" on this post to make it more visible and help other members of the community find solutions more easily. If you don't feel like the answer I marked was correct, feel free to come back to this post and unmark it.  If you still need assistance, we would be more than happy to continue working with you on this - just let us know in a reply.

Thanks,

Geoff