WINDOWS NT SERVER v4.0, Ring Topology

© Copyright Brian Brown, 1996-1999. All rights reserved.
This material may not be reproduced in printed or electronic format without the express permission of the author.

Ring Topology

workstations connect to the ring
faulty workstations can be bypassed
more cabling required than bus
the connectors used tend to cause a lot of problems
commonly used to implement token ring at 4 and 16mbps
four wire, generally STP or UTP

Physical Implementation Of A Ring Network
Each workstation is connected back to a Multiple Access Unit (MAU), which supports up to eight workstations. Additional MAU are cascaded to provide greater workstation numbers.

Wiring is performed in a physical star fashion, with cables wired directly from each workstation back to the MAU.

IEEE 802.5 Token Ring
This protocol is widely used in ring networks for controlling station access to the ring. A short message (called a token) is circulated around the ring, being passed from station to station (it originates from a controller or master station which inserts it onto the ring).

A station which wants to transmit waits for the token to arrive. When the token arrives, the station changes it from a token to a connector message, and appends its message. This new message is then placed on the outgoing side of the ring.

Each station passes on received tokens if they have nothing to transmit. They monitor connector messages to see if the message is addressed to them. If connector messages are addressed to them, they copy the message, modify it to signify its receipt, then send it on around the ring. Connector messages which are not addressed to them are passed directly on to the next station in the ring.

When the connector message travels full circle and arrives at the original sending station, it checks the message to see if it's been received. It then discards the message and replaces it with a token.

Either

Token passing part4 of 5

Token passing part5 of 5

Physical Ring Cable Limits

TOKEN RING NETWORK LAYOUT
Limitations

maximum number of workstations = 96
maximum number of 8228 MAU's = 12
maximum patch cable distance between an 8228 MAU and a station (not including 8' adapter cable) = 150 feet (45 meters)
maximum patch cable distance between two 8228's = 150 feet (45 meters)
maximum patch cable connecting all 8228's = 400 feet (120 meters)

Rules

stations are connected into the jacks of the 8228 units
patch cables interconnect RO to RI for 8228 units.
the last RO is connected to the first RI to form a ring.

Cable

patch cables generally type 6 (26 awg) or 1 (22 awg)
type 1 for lengths > 66 feet (20 meters)
IBM 8310574 MIC connectors
alternatively, UTP with RJ45 connectors

Ring Topology: Summary

Advantages	Disadvantages
Cable failures affect limited users	Costly Wiring
Equal access for all users	Difficult Connections
Each workstation has full access speed to the ring	Expensive Adaptor Cards
As workstation numbers increase performance diminishes slightly

Star Topology

all wiring is done from a central point (the server or hub)
has the greatest cable lengths of any topology (and thus uses the most amount of cable)
generally STP or UTP, four wire

Star Topology: Summary

Advantages	Disadvantages
Easy to add new workstations	Hub failure cripples all workstations connected to that hub
Centralized control	Hubs are slighty more expensive than thin-Ethernet
Centralized network/hub monitoring