[c-nsp] T1 Cables

[Jay Hennigan]

Lamar Owen wrote:

> The T1's I've had experience with have all been wired RJ48S, which uses pairs 
> 1-2 and 7-8 of the 8 pin plug (in TIA-568B that would be the orange-white and 
> brown-white pairs).  If your cables are TIA-568A or B they have the correct 
> pairing.  It's only if you have USOC RJ61 or similar that you have to worry, 
> as that splits the pairs.

RJ48S is indeed the correct designation for T1, but it uses pairs 1-2 
and 4-5.  568B pairing would be white-orange and white-blue.  1-2 and 
7-8 are the correct pairs for 56K DDS circuits.

> One poster mentioned clocking; this I would check.  What sort of errors are 
> you getting from the controller?  I have one T1 here terminated in a RSM/VIP2 
> in a Cat5509 using a PA-MC-8T1.  Some providers have more problems with B8ZS 
> versus AMI, and I have seen odd problems with HDSL (PairGain) provisioned 
> T1's that were the fault of the carrier's shelf backplane.  Currently, the T1 
> that backs up our OC3 is provisioned over fiber with an FMT-6, and that has 
> been absolutely rock solid using a standard Cat5 cable about 100 feet long.

Indeed clocking can be an issue, and it is often difficult to get a 
straight answer from a carrier as to how any given circuit is clocked. 
You want exactly one end of the circuit to provide clock.  As a rule, 
short-haul point-to-point circuits are not clocked by the carrier, most 
others are.

--
Jay Hennigan - CCIE #7880 - Network Engineering - jay at impulse.net
Impulse Internet Service  -  http://www.impulse.net/
Your local telephone and internet company - 805 884-6323 - WB6RDV