The headend and what it does for a cable network
Most cable companies have a DMC (Digital Media Center) that stores all the movies, up and down links content and provides monitoring on input and out put. The DMC is a central ingest point for digital content. However High quality content is bluky and needs to be transported to outlying regions of the network for playout, to ensure that consumers have the quality that they have paid for.
In each geographical region they have a headend. The old analogue headends were quite simple affairs, now they are massive complex installations.
Here is a picture of a UPC headend.
UPC headend
The number of channels, number of concurrent VOD streams and number of internet connections that a cable network can provide is dependent on the number of multiplexers. The multiplexers live in the headend (a bit simplistic, but generally true). The Conditional Access (CA) system also lives in the headend
The headend is the most expensive part of the network, it is often more expensive than all the boxes that it serves.
