4.6 DOCSIS

• A cable modem transmits what is called a ranging request, which allows the CMTS (headend) to determine the network delay to the cable modem, as well as to perform and necessary power adjustments
• Channel allocation in DOCSIS typically involves allocation of channels between one CMTS and one or more cable modems, which are located in the subscribers’ homes.
• Central to the DOCSIS MAC layer is the notion of a service flow, which provides a way to manage both upstream and downstream quality of service management.
• All cable modems must support at least one upstream and one downstream service flow, called the primary service flow.
• Upstream transmission is divided into discrete intervals by an upstream bandwidth allocation mechanism called a minislot.
• Specifically, a new revision to the DOCSIS protocol allows for low latency, through a new specification called LLD (Low-Latency DOCSIS) LLD recognizes that for many interactive applications, such as gaming and video conferencing, low latency is as important as high throughput.