network protocols handbook.pdf

175Protocols GuideWAN - Broadband Access ProtocolsProtocol NameDOCSIS: Data Over Cable ServiceInterface SpecificationProtocol DescriptionData Over Cable Service Interface Specification(DOCSIS),developed by CableLabs and approved by the ITU, defines interfacerequirements for cable modems involved in high-speeddata distribution (both MPEG and IP data) over cable televisionsystem networks. Other devices that recognize and support theDOCSIS standard include HDTVs and Web enabled set-topboxes for regular televisions.There are two key components in the DOCSIS architecture: aCable Modem (CM) which is located at the customer’s premise,and the Cable Modem Termination System (CMTS), which islocated at the head end of the service provider and used to aggregatetraffic from multiple Cable Modems and then communicatewith the backbone network. DOCSIS specifies modulationschemes and the protocol for exchanging bidirectional signalsbetween these two components over cable.Three versions of DOCSIS are now implemented and deployed:DOCSIS 1.0 - High Speed Internet Access. Key features: Downstreamtraffic transfer rates between 27 and 36 Mbps over aradio frequency (RF) path in the 50 MHz to 750+ MHz range,and upstream traffic transfer rates between 320 Kbps and 10Mbps (average 5 Mbps) over an RF path between 5 and 42MHz. However, because data over cable travels on a sharedloop, individuals will see transfer rates drop as more users gainaccess.DOCSIS 1.1 – Data, Voice, Gaming and Streaming. Key features:DOSCIS 1.1 is interoperable with DOCSIS 1.0. It providesenhanced QoS for multiple services such as voice and streaming;improved security over DOCSIS 1.0; and more robust upstreamdata transmission (average 10 Mbps).DOCSIS 2.0 – Has added capacity for symmetric services byoperating at 64 QAM and having new 6.4 MHz wide channel. Ithas increased bandwidth for IP traffic by using enhanced modulationand improved error correction. The result for upstreamtransmission is 30 Mbps, which is 3 times better than DOCSIS1.1 and 6 times than DOSCIS 1.0. DOSCIS 2.0 is interoperableand backward compatible with DOCSIS 1.x.The latest DOCSIS specification eDOCSIS has been publishedto the industry. eDOCSIS, embedded DOCSIS, provides a subordinatefunction at the core chip level to the host device. Ratherthan leveraging a home networking protocol, an embeddedDOCSIS device feeds directly into a cable network’s DOCSISchannel. eDOCSIS is intended to solve end device (and traffic)management, configuration and security issues, to significantlyreduce cost in the service operation and to improve speed andquality of end customer services.Protocol StructureThe specifications of the various DOCSIS versions can be foundin the attached reference documents.Related protocolsIP, MPEG, DOCSIS 1.0, DOCSIS 1.1, DOCSIS 2.0, eDOCSISSponsor SourceDOCSIS is defined by CableLabs (http://www.cablemodem.com/) and approved by ITU.Referencehttp://www.cablemodem.com/downloads/specs/SP_CMTS_NSII01-960702.pdfDOCSIS - CMTS Network Site Interface Specificationhttp://www.cablemodem.com/downloads/specs/SP-CMCI-I09-030730.pdfDOCSIS 1.1 Specificationhttp://www.cablemodem.com/downloads/specs/SP-RFIv2.0-I04-030730.pdfDOCSIS 2.0 - Radio Frequency Interface Specificationhttp://www.cablemodem.com/downloads/specs/SP-OSSIv2.0-I04-030730.pdfDOCSIS 2.0 - Operation Support System Interface Specificationhttp://www.cablemodem.com/downloads/specs/SP-eDOCSIS-I02-031117.pdfeDOCSIS Specification