ring network

jwills

I was reading that on a physical ring topology, if there is a break in the ring the network goes down. I understand that. What i don't understand is i thought rings (token ring) was a logical ring. Therefore if on node was disconnected it wouldn't bring down the ntwk. Could someone explain that to me.

7255carl

hi there, the difference between the ring topology and token ring is that ring topology is wired as a pysical ring, whilst token rings are generally wired as a star topology, giving more capacity to deal with breaks without bringing the network down as the broken connection can be bypassed, have a look at the topology technotes, that should clear up any confusion. hope this helps.

apologies for the brief explanation, the boss just walked in

bighornsheep

http://www.techexams.net/technotes/networkplus/mediatopo.shtml

A ring network is a general topology for node configuration, token ring was the original implementation of a ring network topology, there is also the IEEE 802.5 specifications which is like a token ring topology but does not include physical layout.

In general, the characteristic of a token ring network is that any failed node WILL bring down the network but collision should not occur because there is strong flow control from the token that is passed around.

jwills

OK, so it sounds like you are saying when i hear of ring topoplogy they are talking about topology and when they talk about token ring and FIDDI they are talking about access method which is really a logical ring. Is that correct?

Thanks

bighornsheep

jwills wrote:

when they talk about token ring and FIDDI they are talking about access method which is really a logical ring. Is that correct?

Token ring and FDDI are completely different, even though FDDI uses "rings" they are fibre optic links, and there will be more than one "ring" for redundancy purposes.

I believe the typical usage for FDDI is in the backbone of a network or what Cisco would call the core layer, whereas token ring may be found in the workgroup/LAN portion of a network.

blackmage439

Just as a summary of information posted (and maybe some that's not):

A ring topology is just that: a network physically designed in a bus/ring fashion. Each node is connected to one other node. FDDI follows this topology standard, but with two rings: one for redundancy. A network designed in a ring topology does not necessarily need to follow a logical ring form of communication. For example, you can design an Ethernet network in as a ring topology. However, a ring is nothing more than a bus, which will severely degrade the quality of an Ethernet network. FDDI is usually found connecting sites on a WAN or MAN, or used as the high-speed backbone for a LAN, WAN, or MAN.

A logical ring, which is the idea that Token Ring is based on, does not follow a physical ring topology. Token Ring uses a hub-like device to connect nodes in a star topology. This allows for central control of the token. Generally, you'll never find this technology outside a LAN.

Turgon

I used to support IBM Token Ring in the 90's. It ran on good old chunky IBM Type 1. The central point for the token ring network were the devices known as MAU's or Media Access Units. These controlled the insertion of devices in and out of the token ring network. Our topology was what was known as an 'active star'. The MAUs were connected together with Ring In and Ring out interfaces.

FDDI and Token Ring have some similarities at the frame level. For the old CCIE written I covered a lot of material on FDDI. FDDI has four specifications. For hardware we looked at SAS, DAS and concentrators. Check out the optical bypass switch for resilience.


http://www.cisco.com/univercd/cc/td/doc/cisintwk/ito_doc/fddi.htm