[c-nsp] 2821 VWIC2-2MFT-T1/E1 clocking issue

[Brad Henshaw]

Jay Hennigan wrote:

> Both providers are sourcing clock, but apparently not in sync with
each other.
> Second E-1 on the WIC shows slips.

You're probably seeing a hardware limitation.

My understanding is that the E1 controller can only have one clock
source. When you set 'clock source line' (assuming network-clock-select
is letting that port have priority) the internal PLL is driven by
clocking on the selected interface and all other interfaces gain timing
from the internal clock.

Is this actually causing a problem?

Other than running links to separate providers on physically separate
boxen, you could try setting loop time on both E1's - this decouples
their timing from the PLL and will probably cause slips on both
interfaces, but may change the nature of your problem.

Feel free to slap me around with a clue by four if my understanding is
incorrect. The majority of multiple-E1 boxen I've had to deal with have
utilised E1's from a single provider with a single clock source.

Regards,
Brad