How do ring and bus network connect to router?

Question

Sorry this is probably a very silly question, but for some reason i am confused.

How does a LAN with bus or ring topology connect to a router and other LANs?

For example in a star network they all connect to a switch which can then connect to a router, but where does a switch go and fit in a bus or ring topology?

In this image of a ring network there is no switch: http://www.brainbell.com/tutorials/Networking/images/01fig04.gif

would the switch in the ring network simply be placed alongside the other nodes?

Thank you very much

Answer 1

Although the image in the question is a standard example of a token ring network - with each system having connections to two adjacent machines - that's not the only way they were implemented.

IBM introduced multistation access units which essentially functioned as token ring hubs - you could plug systems into them and remove them without breaking the ring. The Wikipedia article on Token Ring describes these.

I don't think this is what you're asking about, but if you wanted to hook a legacy token ring network to the Internet these days, you can get media converters and/or bridges.

For a bus network like thickwire or thinwire, if you wanted to connect a router, you'd just hook it up like any other device (to a transceiver on thickwire). Like IBM's MAUs for token ring, you could get equipment that would simplify the cabling, e.g. DEC and AMP made special cables and connectors that would let you plug in to a thinwire chain w/out having to break the chain.

Answer 2

In ring and bus there is no switch, the traffic is passed along by each node. This is one of the reasons why you don't see them in use. When lines along the way fail, it breaks the communication instead of just taking out that one machine.

In your picture, they aren't labeled so let's say the headless machine is 1 and the rest are 2-6 going clockwise.

For 1 to talk to 3 it would have to pass through 2 or if 2 was down, then 6, 5 and 4.

Worse off is bus topology, without the loop around, one downed machine would segment the network in two basically.

Take away the link between 1 and 6 on your picture and you'd have bus topology.

Now let's say 3 goes down, 1 and 2 can talk, 4, 5 and 6 can talk, but 1 and 2 cannot reach 4, 5 and 6.

As far as a router, it would be in line the same as any workstation or server and could fall to the same communication breakdowns as described above.

Sure you could say with star topology, you lose 1 switch and everybody is down, but it is a lot easier to have a replacement switch on hand.