Broadband cable is a technology used to transport data using a coaxial cable medium over cable distribution systems. The equipment used on the remote-access side is the cable modem, which connects to the Cable Modem Termination System (CMTS) on the ISP side. The Universal Broadband Router (uBR) provides the CMTS services and is deployed at the cable company headend. The uBR forwards traffic upstream through the provider's WAN core or the local PSTN, depending on the services being provided.

The Data Over Cable Service Interface Specifications (DOCSIS) protocol defines the cable procedures that the equipment needs to support. DOCSIS 2.0 was released in 2002 and remains the current version that most cable modems use today. DOCSIS 3.0 specifications released in 2006 include support for IPv6 and channel bonding.

Figure 5-6 illustrates how a cable modem connects to the CMTS.

Figure 5-6 Data Over Cable

Remote Access

Internet Service Provider

Cable Modem

Cable Modem


Cable Modem Termination System (CMTS)

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