2 Data Over Cable Service Interface Specification
3 INTRODUCTION TO DOCSIS CABLELABS® -An organization that govern the DOCSIS certification for Cable TV Industry equipments -Defined several standards for cable TV industry -One such standard is for Cable Modem and is known as DOCSIS (Data Over Cable Service Interface Specification)
4 MAIN COMPONENTS OF DOCSIS HeadEnd Distribution Hub (resides in HeadEnd) Cable Modem Computer/TV
5 HEADEND 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)
6 HeadEnd CMTS Distribution Hub Distribution Hub Optical Fibre Video Source 1 Video Source2 Data Packets Data Source2 Video Packets Assembly of Video + Data packets
7 Distribution Hub 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.
8 Distribution Hub HEAD END RECEIVER MODULATOR CHANNEL 1 CHANNEL 2 CHANNEL n From Sub 1 From Sub 2 From Sub n UPSTREAM DOWNSTREAM
10 General Architecture of Cable Modem Burst Modulator DemodulatorMAC Interfaces USB Ethernet PCI 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
11 Interesting Question Why did we talk about Cable Modem? DOCSIS is the standard that govern the –Cable Modem, –Cable Modem Terminating System and –their environment.
12 DOCSIS 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.
13 Three Generations of DOCSIS DOCSIS 1.0 DOCSIS 1.1 DOCSIS 2.0
14 DOCSIS 1.0 Primary Internet access service to the Subscribers A single cable is shared by multiple subscribers Includes Baseline privacy features to provide the subscriber security over the shared HFC access network. Most of the BW is reserved for Downstream (from CMTS to CM)
15 DOCSIS 1.0 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)
16 DOCSIS 1.1 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.
17 DOCSIS1.1 Introduces 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)
18 DOCSIS 2.0 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.
19 DOCSIS 2.0 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 cable modems. The saved TS are used by other CMs, which increases the throughput.
20 DOCSIS 2.0 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 to operators.
21 DOCSIS 2.0 Advanced PHY layer modulation techniques that allows operators to run higher modulation levels. Supports immunity to Ingress Noise.
22 DOCSIS SPECIFICATION There are different specifications for each piece of the system. A DOCSIS reference model is defined to understand the layout of different specifications.
23 DOCSIS REFERENCE MODEL PSTN Backbone Network Termination MOD DEMOD Security & Access Controller O/E Node O/E Node O/E Node Combiner Splitter Transmit ter Receiver 5 – 42 MHz 50 - 860 MHz Fiber Cable Modem Operations Support System CMTS HEAD END CMTS-NSI DOCS-OSSI CM-RFI coax CMCI CMTS-PRI Remote Access Server Backbone Transport Adapter WAN T1/T3 Video Data
24 The Existence of DOCSIS 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
25 DOCSIS SPECIFICATIONS 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)
26 CMRFI 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.
27 CMCI Cable Modem to Computer Interface - Defines the protocol between the PC to Cable Modem
28 CMTS-SMI 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
29 OSSI 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