Contrast with nethead. This term refers to a communications worker (be they engineer, manager or general operative) who has a background in the technology of traditional telephone networks, and believes in the use of fixed lines and dedicated hardware for the solution of networking problems. The term comes from Bell, the now defunct US telephone giant. Old fashioned telephone networks are circuit-switched, as opposed to the new packet-switched internet. Netheads are usually strongly opposed to bellheads, whose numbers are now diminishing as the internet spreads and packets look set to dominate even voice telephony.

Bellhead, or bell-head, is an old-school discipline of networking thought that's contrasted with packethead nowadays. This refers to a commitment to locked in data models, or proprietary systems such as might be seen at places like AT&T, Bell, Sprint, and other leviathans of the POTS, or the plain old telephone systems.

One of the best examples of this, and one of the best contrasts would be to compare the now popular packet switching IP (Internet Protocol), to the now-defunct circuit switching ATM (Asynchronous Transfer Mode) protocol. In comparing IP and ATM, the following characteristics are found:

ATM's characteristics include:

  • The somewhat arbitrary 53 bit cell.
  • The use of virtual circuits to establish two types of connections - the permanent virtual circuit, or PVC, and the switched virtual circuit. SVC
  • An attempt to support both queuing and datagram ideals - cells include sequence numbers and other metadata.
IP's characteristics include:
  • Modifiable datagram (packet) sizes, meaning networks with greater throughput can use larger packets of data.
  • The assumption of unreliable infrastructure and engineering around this - CRC error checking is build into the header metadata for IP datagrams.
  • Sequence numbers are enabled by default.

In the above contrast, one can see a static mindset at work. The network represented by the bellhead design of ATM will never increase in bandwidth - voice will always use 24 bits of the 53 bit packet, whereas data can use 48 bits, with five extra bits remain for metadata. This design assumes networking technology will never improve or change.

IP allows larger and larger packet sizes, as well as an unreliable transport method more tolerant of dropped information. This makes IP-model networks more dynamic than circuit-switched networks. As the bandwidth available on networks has surpassed the POTS systems of copper in favor of fiber optic communications, ATM is rapidly becoming obsolete - as are large numbers of bellheads.

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