[c-nsp] Re: DS3 framing: M13 vs. C-bit

[MADMAN]

Michael K. Smith wrote:

> On 1/18/05 9:40 AM, "John Neiberger" <John.Neiberger at efirstbank.com> wrote:
> 
> 
>>I don't have  a lot of experience with DS3s and I have a minor problem
>>that I need some help with. We have a point-to-point DS3 with both
>>endpoints set to M13 framing (Cisco 7513 PA-T3+ and a Kentrox IDSU).
>>This link involves two service providers. Qwest says that we are
>>provisioned for M13, as well. However, Time Warner at the other end of
>>the link seems to think we're provisioned for C-bit. My question is
>>this: does that matter?
>>
>>We see a highly intermittent burst of errors from time to time but
>>other than that we don't see a problem. It can run for days or weeks
>>without a single error and then we'll see a blip of a couple thousand
>>errors, after which it runs cleanly again. Is it possible that this
>>problem is caused because of c-bit being used on the Time Warner side of
>>that part of the link?
>>
>>We have three potential courses of action:
>>
>>1. Get Time Warner to switch to M13
>>2. Get Qwest to switch to c-bit and change our end devices to c-bit
>>3. Do nothing since the errors are brief and infrequent
>>
>>What do you think? Could the framing mismatch cause a problem, perhaps
>>similar to an AMI/B8ZS mismatch in the DS1 world?
>>
> 
> Here is a pretty good discussion of C-Bit vs. M1-3 from the archives.
> 
> http://puck.nether.net/lists/cisco-nsp/2393.html
> 
> I'm a bit surprised you can get the DS-3 to talk end-to-end with two
> different framing types.  I would bet there are more than two circuits in
> play here.  I have always heard C-Bit and B3ZS for Framing/Line-encoding on
> a data circuit.  I *think* MI-3 is more for DS-1 over DS-3 purposes.

   Yes I think C-bit is bascially used for clear channel applications, 
p-p DS3's.  M13 framing is needed when you have a head end terminating 
the DS3 and multiple T1's as spokes.

   Dave

-- 
David Madland
CCIE# 2016
Sr. Network Engineer
Qwest Communications
612-664-3367

"Emotion should reflect reason not guide it"