DOCSIS Archives

25 06, 2010

bradyvolpe.com v2.0

Mia Colabrese2020-11-25T09:02:21-05:00June 25th, 2010|

Changes to bradyvolpe.com! Due to traffic utilization and site limitations I have out-stayed the welcome of the free hosting capabilities of my previous site. Not a bad problem to have. On this new site I have the capabilities to add a great bit more content, interactivity, video/audio content and perhaps some feeds from live demos. With this comes overhead so I will be putting in place some Google Adsense advertisements to hopefully offset these costs. In the mean time I will continue to work on completing my DOCSIS

12 10, 2009

DOCSIS 3.0 Tutorial – Introduction

Mia Colabrese2021-08-17T16:05:13-04:00October 12th, 2009|

This is the first of a new series of Tutorials focused on the Data Over Cable Service Interface Specifications (DOCSIS) version 3.0. I will make the assumption that you are familiar with the DOCSIS 1.x / 2.0 standards or have already reviewed my DOCSIS Basics Tutorial as I will be using many terms without explanation since they were previously covered. The DOCSIS 3.0 specification is an extension of the DOCSIS 1.x and 2.0 specification which dramatically increases the data throughput by adding a technology known as channel bonding to the DOCSIS downstream and upstream, adding increased security, adding support for IPv6, and substantially improving the back-office management support (MIBs, SNMP, IPDR, etc.) for DOCSIS. Each of these topics will covered in much greater detail in this DOCSIS 3.0 tutorial in multiple posts yet to come.

7 10, 2009

DOCSIS Upstream – Part II

Mia Colabrese2021-08-17T13:40:53-04:00October 7th, 2009|

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

2 10, 2009

Speeding Upstream – Part I

Mia Colabrese2021-08-18T10:19:55-04:00October 2nd, 2009|

The first part of this article (in CT's March 2009 issue) discussed downstream potential issues, while this one focuses on the potential issues associated with upstream deployments. In particular, this article covers the critical upstream areas that one should be aware of when getting ready to deploy or already deploying DOCSIS 3.0.

9 03, 2009

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

Mia Colabrese2021-08-17T13:22:59-04:00March 9th, 2009|

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.

3 03, 2009

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

Mia Colabrese2021-08-17T15:43:18-04:00March 3rd, 2009|

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.

28 02, 2009

DOCSIS and Cable Modems – How it works :: UCD

Mia Colabrese2021-08-17T10:36:51-04:00February 28th, 2009|

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

22 02, 2009

DOCSIS and Cable Modems – How it works :: Anatomy of a Burst

Mia Colabrese2021-08-17T22:35:57-04:00February 22nd, 2009|

DOCSIS Cable Modem Data Burst Defined Previously I have discussed that cable modems share the upstream channel by using Time Division Multiple Access (TDMA). This means that when a cable modem is not transmitting data its RF transmitter is turned off. In order to transmit data it must transmit a burst of data which contains a REQUEST to the CMTS. The REQUEST relays the cable modem's Service IDentifier and the number of bytes of information the modem has to transmit in its buffer. The CMTS prioritizes all incoming

16 02, 2009

Troubleshooting DOCSIS – VoIP Impairments > Delay & Jitter

Mia Colabrese2021-08-17T15:54:55-04:00February 16th, 2009|

In this blog I will address delay and jitter as they pertain to VoIP in a DOCSIS network. Delay, jitter and packet loss are the three primary impairment in a VoIP network, but packet loss was addressed in my Troubleshooting DOCSIS - VoIP Impairments > Packet Loss blog. After packet loss, delay is the second most disruptive impairment in VoIP networks. The effects of delay to the caller generally appear as echo and talker overlap. In PSTN communications, echo can arise as acoustic echo between the mouthpiece and

15 02, 2009

Troubleshooting DOCSIS – VoIP Impairments > Packet Loss

Mia Colabrese2021-08-17T15:45:30-04:00February 15th, 2009|

In this blog I am going to focus on VoIP packet loss, which is just one of the three (3) primary types of VoIP impairments that are present in a DOCSIS network. I will cover many RF and IP terms in this blog that I have not discussed in my previous tutorials, not to worry! This terminology is all fodder for future blogs. :-) To review, the three fundamental impairments which impact call quality of VoIP communications are as follows: * Packet Loss – The complete or partial loss of a packet containing actual voice payload. * Delay – The time a packet takes to traverse the space between the source and destination of a voice call. The space is comprised of both the physical distance the data must travel in addition to the active network routing and switching elements, which contribute additional delay. * Jitter – The variance of inter-packet arrival time from one transmitted packet to the next sequential packet.