DOCSIS architecture | DOCSIS network architecture
This page describes DOCSIS architecture and its network elements with functions. The DOCSIS network architecture is divided into customer side components, cable operator side components and HFC network.
What is DOCSIS ?
DOCSIS helps cable operators to provide internet services to consumers over existing cable TV systems. It requires DOCSIS compatible cable modem at the customer premises to access the services provided by the cable operator. The DOCSIS standard is managed by CableLabs. The full form of "DOCSIS" is "Data Over Cable Service Interface Specification". The other contributing companies include Cisco, Broadcom, Intel, Netgear, ARRIS, Texas Instruments and so on. It allows transmission and reception of high bandwidth data over existing cable TV network or HFC (Hybrid Fiber Coaxial) network. The first DOCSIS standard version 1.0 was developed in 1997 followed by other DOCSIS standards as mentioned in the following table.
|Standard version||Features||Downstream data rate||Upstream data rate|
|DOCSIS 1.0||Initial cable broadband technology||40 Mbps||10 Mbps|
|DOCSIS 1.1||Added Voice over IP service||40 Mbps||10 Mbps|
|DOCSIS 2.0||Higher upstream speed||40 Mbps||30 Mbps|
|DOCSIS 3.0||Greatly enhances capacity||1 Gbps||100-200 Mbps|
|DOCSIS 3.1||Capacity and efficiency progression||10 Gbps||1-2 Gbps|
|DOCSIS 4.0||Symmetrical streaming and increased upload speeds||10 Gbps||6 Gbps|
The figure depicts DOCSIS architecture. Let us understand functions of each of its elements. There are three major elements of DOCSIS system viz. Cable modem, HFC network or cable TV network and CMTS. DOCSIS network offers bi-directional flow of IP data between CM and CMTS over existing cable network. Cable network can be either all coaxial cable or Hybrid-Fiber/Coax (HFC) cable network.
DOCSIS cable modem (CM) : It is the main interface between HFC network and Home network to bridge packets flowing between them. The Cable modem allows connections with different customer premise equipments (CPEs) intending to access the internet. Typical CPEs used at home or office premises are gateway, VoIP telephone, WiFi Modem or router, Personal computer and Set Top Box (STB). CPE can either be embedded with CM in single device or both are separated into standalone devices as shown in the figure-1. WiFi modem or router takes care of providing simultaneous internet access to desktop, mobile, laptop, tablet etc. using wifi signals. CPEs support IPv4, IPv6 or both.
CMTS : CMTS stands for Cable Modem Termination System. It is the main element located at cable operator side.
DOCSIS standard defines messages and data types exchanged between CMTS and CM.
CMTS connects cable operator back office and core network to HFC network.
The main function of CMTS is to forward packets between HFC and back office.
It also forwards packets between upstream and downstream channels on HFC network.
Here downstream refers to data flow from cable company to customer premises equipment
where as upstream refers to data flow from CM (i.e. cable modem) to cable company (i.e. CMTS side).
CMTS is connected with DHCP server, switch and router to provide backbone internet connectivity.
DHCP server provides cable modem with initial configuration information such as IP address assignement etc. The other provisioning systems take care of software download to cable modem, configurations of cable modem and so on. SNMP manager allows cable operator to configure and monitor Cable Modem and CMTS. Refer benefits or advantages of DOCSIS standard >>.