Substance:
- Introduction
- Basic Concept of Token Ring
- Token Ring Self Maintenance
- Token Ring Operations Using Hubs.
Token Ring (example data exchange)
1. Introduction
Token Ring was developed by IBM in 1980 and became the IEEE 802.5 standard. It evolved after exceeding the capabilities of 10Base-T.
Token ring is a star topology network, with Multistation Access Unit (MAU) as the center of the network. MAU functions like HUB except that data moves in 1 direction. Data moves like a circle on MAU.
To access the network, a token is needed. The token is thrown into the network and will receive data by sending it back to the sender's token. With the presence of switch technology on Ethernet, token ring is no longer widely used.
2. Basic Concept of Token Ring
Unlike Ethernet, Token Ring uses a topology where data is sent from one machine to another around the ring, and so on until it ends up where it started. This scheme uses the Token Passing Protocol, meaning that a machine can only use the network as long as it has control of the Token, this is useful to ensure that there are no data collisions caused by just one machine. Today, Token Ring is very rare because the cost and flexibility of Ethernet dominates the market.
Below we will show the basic operation of Token Ring and below the animation is an explanation of what is happening. Although the standard speed is 16 Mbps, in this tutorial we will use the 4 Mbps Token Ring speed to explain the basic concepts.
Token Ring - "Refresh" your browser to see the Animation start from the beginning.
Initially, the Token is freely circulating around the ring, consider this as a data frame intended or intended for an empty data-carrying ship. To use the network, the first step the ship's engine must take is to capture the token freely circulating around the ring and then replace it with the data and message it has.
In the above example, machine 1 wants to send some data to machine 4, so the first step it has to do is to capture the freely circulating Token, then write the data and the recipient's address on the Token.
The data packet is then sent to machine 2, machine 2 reads the address and it turns out that it is not the address, then it is thrown to machine 3, machine 3 reads the address and it turns out that it is not the address either, then it is thrown again by machine 3 to machine 4, machine 4 reads the address and it turns out that it matches.
This time it is the correct address and machine number 4 rings or (the indicator is represented by a flashing screen). Unusually, this time releasing the Token to the Ring, the first thing to do is to send a Token frame back to the original address, machine no. 1, with a message that the data has been received (the indicator is represented by a flashing purple screen).
To return the message, the Token is released again by machine 4 to machine 5, then machine 5 checks the address and it turns out that it is not the address, then it is passed again by machine 5 to machine 6, machine 6 reads it and it turns out that it is also not the address, then the Token is passed again by machine 6 to machine 1, then machine 1 checks the address and it turns out that it is correct.
Machine 1 acknowledges the address, reads the acknowledgement from number 4 (the indicator is represented by a purple flashing screen), then machine 1 releases the Free Token back into the Orbit Ring for use again by every machine around the Ring.
That is the basics of Token Ring, the animation gives an illustration and tries to explain how data is sent, received and acknowledged. However, Token Ring is also equipped with a built management and recovery systems making it very tolerant of errors.
3. Token Ring Self Maintenance
When a Token Ring network is running, all machines try to take part in the negotiation to decide who will control the Ring, or more precisely we call it the "Active Monitor". Then the machine with the highest MAC address will win the negotiation participation, while the other machines become "Standby Monitors".
The job of the Active Monitor is to make sure that no machine is causing problems on the network and if there is an error or rebuild the Ring if there is an error or after a break. The Active Monitor performs Ring Polling every 7 seconds and cleans the Ring when there is a problem. Ring Polling allows all machines to know who is participating in the Ring orbit and learn the addresses from their nearest neighbors downstream (from upstream to downstream), termed as "Nearest Active Upstream Neighbor (NAUN)". Ring cleaning is done after receiving a report of interference or data loss.
Each machine knows the address of its nearest or Nearest Active Upstream Neighbor (NAUN). This is the most important function in Token Ring, it looks like updating information continuously, in order to re-establish itself when a machine enters or leaves the Ring.
When a machine enters the Ring, the Active Monitor performs a lebe test to verify that the connection is working properly, if it passes, it sends a voltage to the hub which operates as a relay to enter it into the Ring.
If there is a problem around the Ring, then the machine that is having the problem will immediately stop receiving signals. If in a short time (short period of time) this error still continues, then the recovery procedure according to the algorithm assumes that the machine is at fault and must be cleaned again or possibly removed from the Ring.
4. Token Ring Operation Using Hub
Token Ring Using Hub
A simple Token Ring uses a Hub, simply changing the position so that it appears to be a star topology. The tokens still circulate around the network and are still controlled in the same way, however, using hub or switch technology greatly increases reliability, as the hub can automatically cut off any ports that are disconnected or have faults in the cable.
Token Ring was developed by IBM in 1980 and became the IEEE 802.5 standard. It evolved after exceeding the capabilities of 10Base-T.
Token ring is a star topology network, with Multistation Access Unit (MAU) as the center of the network. MAU functions like HUB except that data moves in 1 direction. Data moves like a circle on MAU.
Figure 3.13 Token Ring
To access the network, a token is needed. The token is thrown into the network and will receive data by sending it back to the sender's token.
With the advent of switch technology on Ethernet, token ring became less widely used.