Trunking
For computer networking, trunking describes using multiple network cables/ports in parallel to increase the link speed beyond the limits of any one single cable or port. (See port trunking for more details.)
In telecommunication, the term trunk has the following meanings [4]:
- In a communications network, a single transmission channel between two points that are switching centers or nodes, or both. See Trunked Radio Systems
- A circuit between switchboards or other switching equipment, as distinguished from circuits which extend between central office switching equipment and information origination/termination equipment.
Note: Trunks may be used to interconnect switches, such as major, minor, public and private switches, to form networks.
- In popular parlance and in the UK at least a Trunk call was a long distance one as opposed to a Local call. See Subscriber trunk dialling and Trunk vs Toll.
Trunking in an exchange
Trunking also refers to the connection of switches and circuits within a telephone exchange [1]. Trunking is closely related to the concept of Grading. Trunking allows a group of inlet switches to receive several calls on the same inlets group and route them to a limited number of outlets. Trunking is based on the statistical assumption that not all callers will wish to make telephone calls at the same time. Thus the service provider can provide a lesser number of circuits than might otherwise be required, allowing many users to “share” a smaller number of connections and achieve capacity savings [2][3].
References
1. ⇧ Flood, J.E., Telecommunications Switching, Traffic and Networks. Chapter 4: Telecommunications Traffic. New York: Prentice-Hall, 1998.
2. ⇧ Motorola, Trunking Communications Overview www.motorola.com/LMPS/RNSG/trunking, Last accessed 13 February 2005.
3. ⇧ The Genesis Group, Trunking Basics www.genesisworld.com/trunking.htm, Last accessed 13 February 2005.
4. ⇧ From the Federal Standard 1037C and from MIL-STD-188 and from the Code of Federal Regulations, Telecommunications Parts 0-199
Derivation
From an early stage in the development of telephony, the need was found for thick cables (up to c. 10cm diameter). These were usually covered in lead. Thus, both in colour and size they resembled an elephant's trunk. Also, since they connect branch offices they act much like the trunk of a tree.