DOCSIS_CMTS

8/22/2019 DOCSIS_CMTS

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Overview of

DOCSIS


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DOCSIS

Data OverCable Service

Interface Specification


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CABLELABS- An organization that govern the DOCSIS

certification forCable TV Industry equipments

- Defined several standards for cable TV industry

- One such standard is forCable Modem and is known as DOCSIS (Data Over Cable

Service Interface Specification)

INTRODUCTION TO

DOCSIS


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HeadEnd

Distribution Hub (resides in HeadEnd)

Cable Modem

Computer/TV

MAIN COMPONENTS OF

DOCSIS


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Contains the major equipment for the network

Talks to different Video Sources as well as Data traffic, assembles and sends to

Distribution Hub

Contains Cable Modem Terminating System (CMTS)

HEADEND


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HeadEnd

CMTS

Distribution

Hub

Distribution

HubVideo

Source2

DataSource2

Assembly of Video

+ Data packets


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Receives Assembled data from the Head End.

Assembled Data Contains Video Packets + Data Packets

The function of the Hub contains

Modulator which modulates the Video packets to different Channels

Receiver to receive data from the subscriber.

Distribution Hub


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Distribution Hub

HEAD END

RECEIVER

MODULATOR

CHANNEL 1

CHANNEL 2

CHANNEL n

From Sub 1

From Sub 2

From Sub n

UPSTREAM

DOWNSTREAM


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CABLE MODEM

HEADEND

CMTS Cable

Modem

Cable

Modem

Cable

Modem

Cable

Modem

Cable

Modem

Cable

Modem


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General Architecture of

Cable Modem

Burst Modulator

Demodulator MAC Interfaces

USB

EthernetPCI

TUNER

Extracts data from

MPEG frames,

Filter data from CMs,

Times transmission

of upstream bursts

A/D Conversion,

Demodulation,

Error Correction,

MPEG

synchronization.

Converts TV

Channel to a

fixed lower

frequency

-In the transmit direction

-D/A conversion

-Reed Solomon encoding of

each burst


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Why did we talk about Cable Modem?

Interesting Question

DOCSIS is the standard that govern the

Cable Modem,

Cable Modem Terminating System and

their environment.


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Standard that defines passing of data (IP), over Hybrid Fiber Coax (HFC) networks.

Data goes along with Video packets.

Main purpose is to ensure interoperability between Cable Modem at Subscribers

location and Cable Modem Terminating System at operators headend.

DOCSIS


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DOCSIS 1.0

DOCSIS 1.1

DOCSIS 2.0

DOCSIS 3.0

Generations of

DOCSIS


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Primary Internet access service to the Subscribers

A single cable is shared by multiple subscribers

Includes Baseline privacy features to provide the subscribersecurity over the shared HFC access network.

Most of the BW is reserved for Downstream (from CMTS toCM)

DOCSIS 1.0


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Introduces

- Efficient utilization of BW, through Web browsing and email.

- Supports best effort transmission of data

- Baseline Privacy Features (SP-CMTS-SMI)

- Security Management Interface (SMI)

DOCSIS 1.0


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Adds ability to delivery data very accurately

Supports Telephone Services

Backward compatibility to DOCSIS 1.0

Have Quality of Service and management of network equipment.

When used in DOCSIS 1.0 environment, it doesnt assure accurate delivery of data.

DOCSIS 1.1


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Introduces

DOCSIS1.1

Quality of Service

-Dynamic Service

-Concatenation

-Fragmentation

-Payload Header Suppression

IP Multicast

SNMP Version3

- Fault Management

CM Authentication

CM Account Mgmt

Enhanced Security

Software

(Difference between DOCSIS 1.0 and DOCSIS 1.1)


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DOCSIS 1.1 builds upon 1.0, but also includes the following features:

Quality of Service

Dynamic Services

Concatenation

FragmentationPayload Header Suppression

IP Multicast

CM Authentication

SNMP v3

View-based access control and management (VACM)CM Account Management

Fault Management

Secure Software


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Since DOCSIS 1.1 provides the QOS and enhanced Security, that was lacking in

DOCSIS 1.0,

DOCSIS 2.0 mainly focuses on

- Improvement of performance- more efficient use of network capacity.

DOCSIS 2.0


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Features Improved in DOCSIS 2.0:

Upstream Capacity:

+ Triples the maximum capacity when

compared to DOCSIS 1.1

+ Increased Upstream throughput to 30.72Mbps.

- Uses a fewer timeslots to transmit a given amount of BW than DOCSIS 1.x cablemodems. The saved TS are used by other CMs, which increases the throughput.

DOCSIS 2.0


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Higher Modulation

(Improved Signal Processing)

- DOCSIS 1.0 provide modulation rate of QPSK

- DOCSIS 1.1 provide modulation rate of 16 QAM

- DOCSIS 2.0 provide modulation rate of 64QAM or 128QAM

Allows more subscribers and services on a single channel ->increased revenues tooperators.

DOCSIS 2.0


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Advanced PHY layer modulation

techniques that allows operators to run higher modulation levels.

Supports immunity to Ingress Noise.

DOCSIS 2.0


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There are different specifications for each piece of the system.

A DOCSIS reference model is defined to understand the layout of different

specifications.

DOCSIS SPECIFICATION


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DOCSIS REFERENCE MODEL

PSTN

Backbone

Network

Network

Termination

MOD

DEMOD

Security & Access

Controller

O/E

Node

O/E

Node

O/E

NodeCombiner

Splitter

Transmitter

Receiver

5

42MH

z

50 - 860 MHz

Fiber

Cable Modem

Operations

Support System

CMTS

HEAD END

coax

Remote

Access

Server

Backbone

Transport

AdapterWAN

T1/T3

Video


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DOCSIS covers many aspects of the Cable

network. Included in the architecture are:

The link between the PC and the Cable Modem (CM)

The link between the CM and the Cable Modem Termination System (CMTS)

Network Management

Link Privacy

Generic information about the network beyond the CMTS

The Existence of DOCSIS


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The link between PC and the Cable Modem (CMCI)

The link between the CM and the CMTS

Network Management (CMTS-OSSI)

Link Privacy (CMTS-SMI)

Generic information about the network beyond the CMTS (CMTS-NSI)

DOCSIS SPECIFICATIONS


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Cable Modem to RF Interface

- Defines the messages that flow over Coax and into Cable Modem

- Description of those messages

- Description of Electrical modulators and PHY layer Techniques.

CMRFI


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Cable Modem to Computer Interface

- Defines the protocol between the PC to Cable Modem

CMCI


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Cable Modem Termination System Security Management Interface

Also known as DOCS SS (Security System)

- Allows only the Valid users to use the system

- Data is encrypted so that a user is assured of privacy of their data

CMTS-SMI


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Operation System Service Interface

- Network Management activities

- Allows the operator to detect problems in the network and determine the following

* - Status

* - Capability

* - Provisioning of the parameters for

Cable Modem

OSSI


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A DOCSIS compliant cable modem requires access to three types of

servers in order to successfully come online.

The first is a DHCP server, which provides the cable modem with an

IP address, a subnet mask and other IP related parameters.

The second is an RFC868 compliant Time of Day (ToD) server which

lets the modem know what the current time is. A cable modem needs

to know the time in order to be able to properly add accurate

timestamps to its event log.

The third is a Trivial File Transfer Protocol (TFTP) server from whicha cable modem is able to download a DOCSIS configuration file

containing cable modem specific operational parameters.


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Simple DOCSIS LAB


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Ranging


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Thank you

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DOCSIS_CMTS

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