Data Segmentation and Token Ring For Networking.

Segmentation:

• As an Ethernet network grows and more stations are added to the LAN, performance can drop significantly.
• Ethernet is a shared media network; when a lot of stations have data to transmit, the net gets congested and many collision occur.
• Segmentation is the solution.
• Segmentation is the process of splitting a larger Ethernet network into two or more segments linked by brides or routers.
• The resulting segments have fewer stations to contend with for access to the net and the router or bride transfer data from one segment to the other only when the destination for the data is on the other segment. The rest of the net traffic stays in the segment where it belongs.

Token Ring:

Token Ring was developed by IBM as a robust and highly reliable network.

Specification:

Cable type                                                                  UTP, STP or fiber-optic

Maximum MSAUs                                                      33

Maximum nodes                                                         260

Max dist between node and MSAU                            45.5 m for UTP, 100m

Max patch cable distance connecting MSAUs             45.5m UTP, 200m STP, 1 Km fiber-optic

Min patch cable dist connecting MSAUs                      2.5m

Max cumulative patch cable dist connecting all MSAUs   121.2m UTP, several Km for fiber-optic

How Token Ring Works:

• The ring passes a free token around the ring in one consistent direction.
• A node receives the token from its nearest active upstream neighbor and passes it to its nearest active downstream neighbor.
• If a station receives a free token, it knows it can attach data and send it on down the ring.
• Each station is given an equal chance to have the token and take control in order to pass data.
• Each station in the ring receives the data from the busy token with data attached and repeats the token
• and data, exactly as it received them, to the next active downstream neighbor on the ring.
• The data is received and retransmitted by each node on the network until it has gone full circle.

Advantages and Disadvantages:

• Token Rings continues to operate reliably under heavy loads
•  Built-in diagnostic and recovery mechanisms
• Token Ring makes connecting a LAN to an IBM mainframe easier
• Fault-tolerance features are provided through ring configuration

Disadvantages:

• Token Ring cards and equipments are more expensive than Ethernet
• Token Ring can be very difficult to troubleshoot and requires considerable expertise

FDDI

FDDI:

• Fiber Distributed Data Interface (FDDI) is another ring-based network.
• FDDI uses fiber-optic cables to implement very fast, reliable networks.
• FDDI uses a token-passing scheme to control network access.
• Several FDDI devices can transmit data simultaneously.
• A token is passed around the ring, and the possessor of the token is allowed to transmit FDDI frames.
•  A FDDI network may have several frames simultaneously circulating on the network.
• This is possible bcz the possessor of the token may send multiple frames, without waiting for the first frame to circulate all the way around the ring before sending the next frame.
• The possessor of the FDDI token is also allowed to release the token and send it to the next station in the ring as soon as it is through transmitting frames, rather than having to wait for the frames to make it all the way around the ring.