Comments on: DOCSIS and Cable Modems – How it works :: Anatomy of a Burst http://volpefirm.com/docsis-101/docsis101_anatomy-of-a-burst/ A Technical Communications Company Wed, 16 May 2012 06:51:01 +0000 hourly 1 http://wordpress.org/?v=3.3.2 By: Brady http://volpefirm.com/docsis-101/docsis101_anatomy-of-a-burst/#comment-128 Brady Tue, 01 Nov 2011 16:26:23 +0000 http://bradyvolpe.com/?p=162#comment-128 Hi Linford, What you are seeing is the nature of a "MAC Domain" and is the proper operation of a CMTS. A MAC Domain is defined on the CMTS as the Downstream port associated with the respective upstream ports. So on your Terayon 3500, the downstream on one line card is associated with the upstreams on that same line card, which makes up a single MAC domain. On line card #2 you have a second MAC domain. Some CMTS vendors, like Cisco, give you the ability to associate the downstream of one MAC domain with the upstreams of another MAC domain. Unfortunately I have very little experience on Terayon CMTSs and have not tried to do cross-MAC domain associations. I recommend that you consult the manual if you have one. Good luck, -Brady Hi Linford,

What you are seeing is the nature of a “MAC Domain” and is the proper operation of a CMTS. A MAC Domain is defined on the CMTS as the Downstream port associated with the respective upstream ports. So on your Terayon 3500, the downstream on one line card is associated with the upstreams on that same line card, which makes up a single MAC domain. On line card #2 you have a second MAC domain.

Some CMTS vendors, like Cisco, give you the ability to associate the downstream of one MAC domain with the upstreams of another MAC domain. Unfortunately I have very little experience on Terayon CMTSs and have not tried to do cross-MAC domain associations. I recommend that you consult the manual if you have one.

Good luck,
-Brady

]]> By: Linford http://volpefirm.com/docsis-101/docsis101_anatomy-of-a-burst/#comment-127 Linford Sun, 30 Oct 2011 23:59:31 +0000 http://bradyvolpe.com/?p=162#comment-127 I have a Terayon 3500. I am using 2 Line Cards, that is 4 US ports on each card. I am trying to use one downstream frequency for all CM's assocaited with the 8 US's. I am finding that the CM's only lock when they see a DS from their corresponding line card. In other words CM's assocaited with Card 3 will not work with a downstream from Card 2. Is this normal, how do I correct this. Linford I have a Terayon 3500. I am using 2 Line Cards, that is 4 US ports on each card. I am trying to use one downstream frequency for all CM’s assocaited with the 8 US’s. I am finding that the CM’s only lock when they see a DS from their corresponding line card. In other words CM’s assocaited with Card 3 will not work with a downstream from Card 2. Is this normal, how do I correct this.

Linford

]]> By: Brady http://volpefirm.com/docsis-101/docsis101_anatomy-of-a-burst/#comment-126 Brady Wed, 26 May 2010 01:56:46 +0000 http://bradyvolpe.com/?p=162#comment-126 Hi Aditya, The IUCs are an output of the Burst Profile or modulation profile defined in the running-config on a Cisco CMTS. Cisco has a lot of great online documentation for modifying their modulation profiles depending upon which CMTS model you have and which IOS you are running. I recommend Goggling this topic and you should come up to speed rather quickly. But you absolutely must have administrator access to the CMTS. This is not something that can be done from the cable modem (i.e. if you are trying to hack in :-). Regards, -Brady Hi Aditya,

The IUCs are an output of the Burst Profile or modulation profile defined in the running-config on a Cisco CMTS. Cisco has a lot of great online documentation for modifying their modulation profiles depending upon which CMTS model you have and which IOS you are running. I recommend Goggling this topic and you should come up to speed rather quickly. But you absolutely must have administrator access to the CMTS. This is not something that can be done from the cable modem (i.e. if you are trying to hack in :-) .

Regards,
-Brady

]]> By: Aditya http://volpefirm.com/docsis-101/docsis101_anatomy-of-a-burst/#comment-125 Aditya Tue, 13 Apr 2010 04:35:44 +0000 http://bradyvolpe.com/?p=162#comment-125 can we force cmts to select "burst profile" via IUCs ? If so which command is there for Cisco CMTS ? can we force cmts to select “burst profile” via IUCs ?
If so which command is there for Cisco CMTS ?

]]> By: Brady http://volpefirm.com/docsis-101/docsis101_anatomy-of-a-burst/#comment-124 Brady Tue, 08 Dec 2009 15:48:11 +0000 http://bradyvolpe.com/?p=162#comment-124 Okinawajoe, For DOCSIS 1.x and 2.0 timing sources are not easily supported for DOCSIS CMTSs. In DOCSIS 3.0 Modular CMTS architectures, they do become mandatory and greatly improve the timing of the architecture. Symmetricom is a provider of DOCSIS Timing References for DOCSIS 3.0 CMTSs. I will cover this in more detail when I pick back up the DOCSIS 3.0 Tutorial series. Regards, -Brady Okinawajoe,

For DOCSIS 1.x and 2.0 timing sources are not easily supported for DOCSIS CMTSs. In DOCSIS 3.0 Modular CMTS architectures, they do become mandatory and greatly improve the timing of the architecture. Symmetricom is a provider of DOCSIS Timing References for DOCSIS 3.0 CMTSs. I will cover this in more detail when I pick back up the DOCSIS 3.0 Tutorial series.

Regards,
-Brady

]]> By: okinawajoe http://volpefirm.com/docsis-101/docsis101_anatomy-of-a-burst/#comment-123 okinawajoe Tue, 01 Dec 2009 16:00:25 +0000 http://bradyvolpe.com/?p=162#comment-123 Looking forward to reading more on A-TDMA ... question ... is an external timing source required for A-TDMA? I seem to remember this being the case (highly suggested?) in a Symmetricom white paper. Looking forward to reading more on A-TDMA … question … is an external timing source required for A-TDMA? I seem to remember this being the case (highly suggested?) in a Symmetricom white paper.

]]> By: Brady http://volpefirm.com/docsis-101/docsis101_anatomy-of-a-burst/#comment-122 Brady Mon, 23 Feb 2009 13:54:59 +0000 http://bradyvolpe.com/?p=162#comment-122 Dave, Good catch. I made the correction already. I spend too much time on Cisco CMTSs where the standard minimum mini-slot time is two-ticks or 12.5 usec. Thanks for giving feedback on my error. Nothing worse than mis-information. Regards, -Brady Dave,

Good catch. I made the correction already. I spend too much time on Cisco CMTSs where the standard minimum mini-slot time is two-ticks or 12.5 usec. Thanks for giving feedback on my error. Nothing worse than mis-information.

Regards,
-Brady

]]> By: Dave http://volpefirm.com/docsis-101/docsis101_anatomy-of-a-burst/#comment-121 Dave Mon, 23 Feb 2009 13:30:51 +0000 http://bradyvolpe.com/?p=162#comment-121 Brady, Pretty sure a tick is 6.25us, not 12.5. 160,000 ticks per second = 6.25us Dave Brady,

Pretty sure a tick is 6.25us, not 12.5.
160,000 ticks per second = 6.25us

Dave

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