Token passing: Difference between revisions
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On a [[local area network]], '''token passing''' is a [[channel access method]] where a packet called a ''token'' is passed between nodes to authorize that node to communicate.<ref>{{cite web|last1=Sheldon|first1=Tom|title=Token and Token-Passing Access Methods|url=http://www.linktionary.com/t/token_access.html|website=Linktionary|accessdate=8 July 2017}}</ref><ref>{{cite book|last1=Littlejohn Shinder|first1=Debra|title=Computer Networking Essentials|date=2001|publisher=Cisco Press|isbn=978-1587130380|page=123|url=https://books.google.com/books?id=ZMizSUW7XF4C&q=token+passing&pg=PA123|accessdate=8 July 2017}}</ref><ref>{{cite web|last1=Savage|first1=Stefan|title=Lecture 6: Media Access Control|url=https://cseweb.ucsd.edu/classes/fa11/cse123-a/123f11_Lec6.pdf|website=Computer Science and Engineering|publisher=UC San Diego|accessdate=8 July 2017}}</ref> In contrast to [[Polling (computer science)|polling]] access methods, there is no pre-defined "master" node.<ref>{{cite web|last1=DiNicolo|first1=Dan|title=Essential Network Concepts Part 3|url=http://www.securitypronews.com/essential-network-concepts-part-3-2004-03|website=Security Pro News|accessdate=9 July 2017|archive-date=16 July 2013|archive-url=https://web.archive.org/web/20130716120055/http://www.securitypronews.com/essential-network-concepts-part-3-2004-03|url-status=dead}}</ref> The most well-known examples are [[Token Ring|IBM Token Ring]] and [[ARCNET]], but there were a range of others, including [[FDDI]] (Fiber Distributed Data Interface), which was popular in the early to mid 1990s. |
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Token passing schemes degrade deterministically under load, which is a key reason why they were popular for industrial control LANs such as [[Manufacturing Automation Protocol|MAP]], (Manufacturing Automation Protocol).<ref>{{cite web|title=Token Bus (IEEE 802.4)|url=https://www.technologyuk.net/telecommunications/networks/token-bus.shtml|website=www.technologyuk.net|accessdate=8 July 2017}}</ref> The advantage over [[Contention_(telecommunications)|contention]] based channel access (such as the [[CSMA/CD]] of early Ethernet), is that collisions are eliminated, and that the channel [[Bandwidth (computing)|bandwidth]] can be fully utilized without idle time when demand is heavy.<ref>{{cite book|last1=Hura|first1=Gurdeep|title=Data and Computer Communications: Networking and Internetworking|date=2001|publisher=CRC Press|isbn=978-0849309281|page=327|url=https://books.google. |
Token passing schemes degrade deterministically under load, which is a key reason why they were popular for industrial control LANs such as [[Manufacturing Automation Protocol|MAP]], (Manufacturing Automation Protocol).<ref>{{cite web|title=Token Bus (IEEE 802.4)|url=https://www.technologyuk.net/telecommunications/networks/token-bus.shtml|website=www.technologyuk.net|accessdate=8 July 2017|archive-date=4 July 2019|archive-url=https://web.archive.org/web/20190704173558/http://www.technologyuk.net/telecommunications/networks/token-bus.shtml|url-status=dead}}</ref> The advantage over [[Contention_(telecommunications)|contention]] based channel access (such as the [[CSMA/CD]] of early Ethernet), is that collisions are eliminated, and that the channel [[Bandwidth (computing)|bandwidth]] can be fully utilized without idle time when demand is heavy.<ref>{{cite book|last1=Hura|first1=Gurdeep|title=Data and Computer Communications: Networking and Internetworking|date=2001|publisher=CRC Press|isbn=978-0849309281|page=327|url=https://books.google.com/books?id=c0z7d9S82EsC&q=token+deterministic&pg=PA327}}</ref> The disadvantage is that even when demand is light, a station wishing to transmit must wait for the token, increasing [[latency (engineering)|latency]]. |
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Some types of token passing schemes do not need to explicitly send a token between systems because the process of "passing the token" is implicit. An example is the channel access method used during "Contention Free Time Slots" in the [[ITU-T]] [[G.hn]] standard for high-speed [[local area network]]ing using existing home wires (power lines, phone lines and coaxial cable). |
Some types of token passing schemes do not need to explicitly send a token between systems because the process of "passing the token" is implicit. An example is the channel access method used during "Contention Free Time Slots" in the [[ITU-T]] [[G.hn]] standard for high-speed [[local area network]]ing using existing home wires (power lines, phone lines and coaxial cable).{{cn|date=July 2017}} |
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==See also== |
==See also== |
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*[[Token ring]] |
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*[[ARCNET]] |
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*[[Cambridge Ring (computer network)|Cambridge Ring]] |
*[[Cambridge Ring (computer network)|Cambridge Ring]] |
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*[[HP-IL|HP Interface Loop (HP-IL)]] |
*[[HP-IL|HP Interface Loop (HP-IL)]] |
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*[[Ring network]] |
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==References== |
==References== |
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Latest revision as of 02:36, 4 July 2024
On a local area network, token passing is a channel access method where a packet called a token is passed between nodes to authorize that node to communicate.[1][2][3] In contrast to polling access methods, there is no pre-defined "master" node.[4] The most well-known examples are IBM Token Ring and ARCNET, but there were a range of others, including FDDI (Fiber Distributed Data Interface), which was popular in the early to mid 1990s.
Token passing schemes degrade deterministically under load, which is a key reason why they were popular for industrial control LANs such as MAP, (Manufacturing Automation Protocol).[5] The advantage over contention based channel access (such as the CSMA/CD of early Ethernet), is that collisions are eliminated, and that the channel bandwidth can be fully utilized without idle time when demand is heavy.[6] The disadvantage is that even when demand is light, a station wishing to transmit must wait for the token, increasing latency.
Some types of token passing schemes do not need to explicitly send a token between systems because the process of "passing the token" is implicit. An example is the channel access method used during "Contention Free Time Slots" in the ITU-T G.hn standard for high-speed local area networking using existing home wires (power lines, phone lines and coaxial cable).[citation needed]
See also
[edit]References
[edit]- ^ Sheldon, Tom. "Token and Token-Passing Access Methods". Linktionary. Retrieved 8 July 2017.
- ^ Littlejohn Shinder, Debra (2001). Computer Networking Essentials. Cisco Press. p. 123. ISBN 978-1587130380. Retrieved 8 July 2017.
- ^ Savage, Stefan. "Lecture 6: Media Access Control" (PDF). Computer Science and Engineering. UC San Diego. Retrieved 8 July 2017.
- ^ DiNicolo, Dan. "Essential Network Concepts Part 3". Security Pro News. Archived from the original on 16 July 2013. Retrieved 9 July 2017.
- ^ "Token Bus (IEEE 802.4)". www.technologyuk.net. Archived from the original on 4 July 2019. Retrieved 8 July 2017.
- ^ Hura, Gurdeep (2001). Data and Computer Communications: Networking and Internetworking. CRC Press. p. 327. ISBN 978-0849309281.
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