Token Ring

Ring network is one of IEEE standards (IEEE 802.5) .It is developed by IBM. The Token ring network is based on ring topology.

A token passing ring LAN is a group of computers connected in a loop. The group uses a token passing access mechanism. A computer wishing to send data should first receive permission. When it gets control of the network it may transmit a frame. Each frame transmitted on the ring is transmitted from one computer to the next, until it ultimately returns to the initiator of the transmission.

The transmitted signal will travel in this ring network from hub to hub. Any computer connected to this ring will have access to this data. The token comes from the nearest active upstream neighbor (NAUN). When a computer receives a token packet, if no attached data with this token and the computer has data ready for transmission, it attaches its data to the token then sends it to its nearest active downstream neighbor (NADN). Each computer downstream will pass the data on since the token is being used until the data reaches its recipient. The recipient will set two bits to indicate it received the data and transmit the token and data. When the computer that sent the data receives the package, it can verify that the data was received correctly. It will remove the data from the token and pass the token to its NADN.


-Token Ring Speed

Although the process may seem to be cumbersome, the speed of data transmission is exceedingly fast and movement of the token is measured in microseconds. The token ring also has a built-in recovery and management system to ensure the system does not give way to faults or problems.

Although the Token Ring networking system appears to be reliable and fast, its early development stages were hit with problems and issues which made it appear to be less reliable and efficient than the Ethernet networking system. These led to its subsequent decline, with Ethernet now in place in an estimated 70 percent of LAN setups worldwide.

Token ring applet :

Code:

http://whale.hit.bme.hu/~remopp/DES/SimpleApplet/index.html

High Speed Token Ring


High Speed Token Ring, or HSTR, is a new token ring standard that
promises to push token ring speeds to 100 Mbps and 1 Gbps. The High
Speed Token Ring Alliance consists of 3Com, Bay Networks, IBM,
Madge, Olicom, UNH Interoperability Lab, and Xylan.

The first HSTR specification will allow for 100 Mbps token ring
speeds over both Type 1 and UTP copper cabling. Further
specifications will tackle 100 Mbps token ring over fiber. These
standards are due for completion in June or July of 1998. Another
HSTR specification will allow for 1 Gbps HSTR over fiber, and this
standard is due to be completed at the end of 1998.