Tag Archives: MAC

Fresh Tech | DOCSIS Protocol Analyzer – Can’t stop a good idea!

November 22, 2011   Brady   No comments
DOCSIS Xpert Protocol Analyzer

When I first heard rumor that a knew company had a DOCSIS protocol analyzer floating around I had to see it! With full disclosure, many of you know that after 10 years in RF and fiber-optic transport equipment, I spent a few years designing, marketing and selling DOCSIS protocol analyzers. More specifically I focused on making them available to cable operators because I knew they could detect really difficult to isolate problems. Averna know owns the technology from my Sigtek days, so it is nice to see a new competitor in the space. What’s more is that its nice to see this competitor at SCTE Cable-Tec Expo who is interested in cable operator’s issues.

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DOCSIS 3.0 Tutorial – Upstream Channel Bonding

August 22, 2010   Brady   5 Comments
DSAM DOCSIS 3.0 Throughput Test

The focus of this article will be on the mechanics of upstream channel bonding and how it works more from a DOCSIS protocol perspective. Much more detailed information can be found in the DOCSIS 3.0 MULPIv3.0 document located in the Library, but this will provide a high level overview for the layman who is curious about the basics. First lets understand that it is the cable modem that is doing the channel bonding, remember in the upstream the cable modem transmits data to the CMTS. Per DOCSIS 3.0, the CM can bond from one to four channels in the upstream as coordinated by the CMTS. The CM is always under control by the CMTS.

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DOCSIS 3.0 Tutorial – Downstream Channel Bonding

July 18, 2010   Brady   2 Comments

Downstream Channel Bonding is perhaps the ball bearings of DOCSIS 3.0, enabling subscriber data speeds in excess of 160 Mbps (4 times that of previous DOCSIS versions). While conceptually simple, the principle of combining multiple downstream DOCSIS channels together to carry the same user data must have tight constraints in order to preserve the integrity of the data and have the data arrive at the correct subscriber’s device and in sequence. This article will cover both the physical layer aspects and DOCSIS protocol aspects that enable channel bonding.

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Speeding Upstream – Part II

October 07, 2009   Brady   5 Comments

This article will focus more specifically on DOCSIS 3.0 issues that will occur as you are deploying DOCSIS 3.0 or post -deployment.

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DOCSIS and Cable Modems – How it works :: Quality of Service

March 09, 2009   Brady   2 Comments
Quality of Service

DOCSIS 1.0 enabled data over coax with a “best effort” service using a data request-grant methodology. DOCSIS 1.1 and subsequent specifications added guaranteed Quality of Service (QoS) by providing Unsolicited Grant Synchronization (UGS) which means that a cable modem does not have to send a data request in order to receive a bandwidth grant from the CMTS. The new UGS service is an enabling technology which has allowed cable operators to successfully deploy the highly revenue generating Voice-over-IP (VoIP) services. In the following sections I will illustrate the differences between best-effort (request-grant) and QoS (UGS) services.

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DOCSIS and Cable Modems – How it works :: Station Maintenance

March 03, 2009   Brady   33 Comments
DOCSIS Station Maintenance

While the UCD provides the language of the DOCSIS network, the Station Maintenance messaging is the proverbial “heartbeat” of the DOCSIS network. A station maintenance session consists of a Range Request sent from a cable and a Range Response sent by the CMTS. The CMTS analyzes the signal quality of the Range Request message and sends back any necessary RF adjustments in the Range Response message. This “handshake” between every cable modem and the CMTS must occur once every 30 seconds as dictated by the DOCSIS specification.

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DOCSIS and Cable Modems – How it works :: UCD

February 28, 2009   Brady   11 Comments
DOCSIS Upstream Channel Descriptor - UCD

Just as a picture is worth a thousand words, so is a complete Upstream Channel Descriptor (UCD) as seen by a cable modem. This message, sent every two seconds by the the CMTS, contains an enourmous amount of valuable information that every cable modem on a DOCSIS network needs to know in order to communicate. Often undervalued, the UCD is a virtual Hitchiker’s Guide to the DOCSIS network! So without any further ado, let me show you an example of a full UCD message and then explain its contents further

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DOCSIS and Cable Modems – How it works :: Cable Modem Registration

February 09, 2009   Brady   30 Comments
DOCSIS Network Cable Modem Registration Illustration

Through DOCSIS tutorial seminars, I have found the most effective way to bring someone up to speed on DOCSIS communications is by teaching the cable modem registration process. During the registration process, we will cover the RF physical layer, theDOCSIS Media Access Layer (MAC) and the Internet Protocol (IP) layer. Yes, the cable modem exercises the first three layers of the Open Systems Interconnection Reference Model (OSI Reference Model or OSI Model)…

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