The IEEE 802.X (ISO 8802.X) LAN group of standards:
The IEEE has produced several standards for LAN's which are collectively known as the IEEE 802 series.The various standards are compatible at the upper part of the data link layer but differ at the physical layer and the MAC sublayer.They have been adopted by ANSI and by the ISO.
The table below outlines the standards and their definitions:
|
IEEE 802.1 |
Details how the other 802 standards relate to one another and to the ISO OSI Reference Model . |
|
IEEE 802.2 (ISO 8802.2) |
Divides the OSI data link layer into two sublayers and defines the functions of the Logical Link Control (LLC) and the Medium Access Control (MAC) sublayers. |
|
IEEE 802.3 |
Defines the Carrier Sense Multiple Access / Collision Detection (CSMA/CD) protocol, which is often referred to as Ethernet. |
|
IEEE 802.4 (ISO 8802.4) |
Defines the token passing bus access method. |
|
IEEE 802.5 (ISO 8802.5) |
Defines the token ring access method. |
|
IEEE 802.5j (ISO 9314) |
Defines the fibre distributed data interface (FDDI), which uses a token ring access method with fibre optic cables and operates at a bit rate of 100 Mbps. |
IEEE 802.5 (ISO 8802.5) Token Ring Access Method Standard:
The IEEE 802.5 Standard is based on a technology originally developed by IBM in the 1970's.It was standardised by the IEEE as standard 802.5 in 1985.
Where should Token Ring networks be used......?:
The standard states that token ring is intended for use in commercial and light industrial environments.Use in home or heavy-industrial environments, although not precluded, is not considered to be within the scope of the standard.
An overview of Token Ring networks:
A token ring network is a type of Local Area Network (LAN), where workstations and network devices are normally physically connected in a star-wired ring configuration.The Token Ring protocol provides services at the Physical and Data Link Layers of the OSI Reference model.Signals travel around the network from one station to the next with the cabling ensuring that a logical ring is maintained.IEEE 802.5 networks originally operated at 4Mbps (and indeed some still do), but the standard now covers transmission rates of up to 16Mbps.Workstations connect to central hubs often called Multistation Access Units (MSAU's).Multiple MSAU's are connected together to create larger multistation networks.
The data access method used on token ring networks is called token passing.This is a deterministic access method which ensures collisions cannot occur as only one station can transmit at any given time.
