Token Ring Facts

Token Ring Facts

Token ring began as a proprietary networking standard developed by IBM. Now there is a public token ring networking standard created by the IEEE 802.5 committee and other vendors that manufacture token ring components. Token ring was a popular networking architecture that is quickly being replaced by Ethernet. However, you may still encounter token ring in some existing networks.
Token ring networks have the following advantages:

• There are no collisions.
• The transmitting host can use the entire bandwidth to send its data.
• You can assign priorities to designated hosts to give them greater network access.
• Troubleshooting broken network connections is made easy by built-in diagnostic devices.

Token ring networks have the following disadvantages:

• Higher cost than Ethernet networks.
• Slower operating speeds than Ethernet networks.

The following table describes various details about token ring.

Characteristic	Description
Topology	Token ring networks are wired using a physical star, logical ring topology (a physical ring topology is also possible but not common).
Media Access Method	Token ring uses a token-passing media access method: A token passes from host to host. When a host needs to transmit, it grabs the token. The host encapsulates its data into a frame and transmits it around the ring. Each host examines the recipient address of the frame until it arrives at the recipient. The recipient transmits a success frame to the transmitting host to confirm that it received the data. Once it receives a success frame, the sending host creates and releases a new token. A host can communicate directly only with machines immediately upstream or downstream from them in the data flow. A broken ring results when a host fails. Other hosts on the network can no longer communicate with any hosts downstream from the break.
Transmission Media	Token ring networks support the following transmission media: Special IBM-type cables STP and UTP Fiber optic Token Ring uses several types of drop cables to connect workstations to the MSAU (multistation access unit): Type 1 or Type 2 shielded twisted pair (STP) wiring with a DB-9 connector. Category 3 (4 Mbps) or Category 5 (16 Mbps) unshielded twisted pair (UTP) cabling with RJ-45 connectors.
Networking Devices	The central connecting point for a token ring network is an MAU (multi-station access unit). You can uplink MAUs by connecting patch cables between the RI (ring in) and RO (ring out) ports on each MAU. Be aware that you must connect both sets of RI and RO ports on both MAUs to make sure the ring is complete.
Speed	Common token ring networks operate at either 4 or 16 Mbps. Newer standards include 100 Mbps and Gigabit (1000 Mbps) token ring, although these have never been widely adopted.