17 GLOSSARY
H
TERM | DEFINITION |
H.323 | A suite of protocols created by the ITU for interactive video |
| conferencing, data sharing, and audio applications such as VoIP. |
Network where only one device at a time can transmit data. See | |
| also |
headend | A location that receives TV programming, radio |
| programming, data, and telephone calls that it modulates |
| onto the HFC network. It also sends return data and telephone |
| transmissions. Headend equipment includes transmitters, |
| preamplifiers, frequency terminals, demodulators, modulators, |
| and other devices that amplify, filter, and convert incoming |
| broadcast TV signals to wireless and cable channels. |
header | The data at the beginning of a packet that identifies what is in the |
| packet. |
hexadecimal | A |
| numbers (0 to 9 and the letters A to F) as base units before |
| adding a new position. On computers, hexadecimal is a |
| convenient way to express binary numbers. |
HFC | A hybrid fiber/coaxial cable network uses |
| trunk and coaxial cable to the subscriber’s premises. |
hop | The interval between two routers on an IP network. The number |
| of hops a packet traverses toward its destination (called the hop |
| count) is saved in the packet header. For example, a hop count |
| of six means the packet has traversed six routers. The packet |
| hop count increases as the |
host | In IP, a host is any computer supporting |
| services with full |
| unique host number that, when combined with the network |
| number, forms its IP address. |
| Host also can mean: |
| • A computer running a web server that serves pages for |
| one or more web sites belonging to organization(s) or |
| individuals |
| • A company that provides this service |
| • In IBM environments, a mainframe computer |
HTML | Hyper Text Markup Language |
hub | On a LAN, a hub is a device that connects multiple hosts to the |
| LAN. A hub performs no data filtering. See also bridge and router. |
| An IP hub is typically a unit on a rack or desktop. |
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