[cisco-voip] what is: "cablelength long 0db"

[Graham, Darel]

Get a TBERD and play with the level settings. Measure the incoming signal level from the LEC and the output levels of the router T1 card at different settings. This is the only way you will really know and understand what it is doing and what you are getting.
All the answers here are great influencers, but they cannot tell you what your local provider is sending and what you are receiving on that T1. A TBERD is a handy piece of test equipment to see those levels.

Darel

From: cisco-voip-bounces at puck.nether.net [mailto:cisco-voip-bounces at puck.nether.net] On Behalf Of Lelio Fulgenzi
Sent: Monday, August 23, 2010 4:11 PM
To: <nikola at att.net>
Cc: Nikola Stojsin; voyp list
Subject: Re: [cisco-voip] what is: "cablelength long 0db"

Thanks. I'll have to review that doc.

…
Don't look at me, my iPod maid that spilling mistake.

On 2010-08-23, at 6:21 PM, Nikola Stojsin <nikolas at networkmakers.com<mailto:nikolas at networkmakers.com>> wrote:
Hello Lelio:

If I remember correctly, SPServices adds SSH/SSL, ATM, VoATM, and MPLS to IP Voice (which itself adds voice to the data-only IP Base) etc.

This white paper might be useful (especially ‘Cisco Image Packaging section’, somewhere in the middle):
http://www.cisco.com/web/about/security/intelligence/ios-ref.html

As for the cablelength long 0db, that command does two things: (1) compensates for the reception loss due to the cable length by increasing the pulse of a signal at the receiver (26dB is the default), and (2) tries to controls far-end crosstalk (in other words, by attenuating the signal from the transmitter - 0dB here – it tries to keep sending and receiving signal within 7.5dB of each other). To quote Cisco:  “Line build-out attenuates the stronger signal from the customer installation transmitter so that the transmitting and receiving signals have similar amplitudes. A signal difference of less than 7.5 dB is ideal.” In other words, you are amplifying what you receive and reducing what you send in an attempt to reduce the difference in sending and receiving signal levels below 7.5dB, all in order to prevent crosstalk. Etc. Etc.

If you do a quick sh controller t1 0/0/0 and see the following line: “Cablelength is long gain26 0db”, that means pulse increase of 26dB of what the interface receives and 0db attenuation (no attenuation) of what the interface sends. Your mileage may vary here, but I have yet to see this command being needed at the normal PRI cable lengths; conversely, it can be a lifesaver if the cable is long (or – more commonly! – provider signal is challenged).

HTH,
Nikola



-------------------------------------------
Nikola Stojsin
PhD CCIE #12888
President
Network Makers LLC
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From: cisco-voip-bounces at puck.nether.net<mailto:cisco-voip-bounces at puck.nether.net> [mailto:cisco-voip-bounces at puck.nether.net] On Behalf Of Lelio Fulgenzi
Sent: Monday, August 23, 2010 5:26 PM
To: voyp list
Subject: [cisco-voip] what is: "cablelength long 0db"

I've got this on my new 3845, but it's not on my other one.
________________________________
controller T1 0/0/0
 cablelength long 0db
!
controller T1 0/1/0
 cablelength long 0db
________________________________

And another thing, why am I running "(C3845-SPSERVICESK9-M), Version 15.0(1)M2"

isn't SP mean ServiceProvider? I'm sure I didn't ask for this.

What are people normally running on their branch voice routers ???

---
Lelio Fulgenzi, B.A.
Senior Analyst (CCS) * University of Guelph * Guelph, Ontario N1G 2W1
(519) 824-4120 x56354 (519) 767-1060 FAX (JNHN)
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
Cooking with unix is easy. You just sed it and forget it.
                              - LFJ (with apologies to Mr. Popeil)


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