collision in switched systems ?

ggauravr · January 2010

I had this doubt while studying about bridges and switches..Hope someone would help me.
A bridge helps divide the collision domain by dividing an otherwise single network into two or more network segments,so that each network segment acts as a separate collision domain.If two or more devices from different segments intend to send data to nodes which are in the same segment ,does that result in a collision at the receiver segment ??
and similarly I read that there's no collision in a full-duplex switched system,so there's no need for collision handling techniques.. What if two or more nodes in such a system,send data to a same node..does that result in a collision at the receiver side ??
Hope to get help from someone..thanks in advance.

hexem · January 2010

As you say the bridge creates seperate collision domains, which effectively means shared bandwidth for all nodes in that collision domain, the more nodes in a collision domain the more likely you are to experience a collision.

All devices in that collision domain can only send or receive, they cannot do both at the same time. this is half-duplex networking.

Just to add, bridges also filter and learn and foward based on mac addresses, this is done through software instead of hardware, just think of a switch as a bridge with more ports and the ability for full duplex instead of half.

Correct about switche's they are full-duplex, meaning that nodes can send and receive at the same time, which effectively eliminates collisions and the need for CSMA/CD as it's creating a point-to-point connection (using mac addresses)

ggauravr · February 2010

thanks hexem ,for looking into my question ..but Im not yet clear ..sorry if im misunderstaning the concept.. as u said in full-duplex networking ,a node can send and receive at the same time .. But what Im asking is what if two or more stations want to send frames to the same node ..ie two or more stations intend to send data to the same node .. in that case the data from the two sending devices would collide at the receiver side and receiver may get garbled data.. ??

mikem2te · February 2010

ggauravr wrote: »

thanks hexem ,for looking into my question ..but Im not yet clear ..sorry if im misunderstaning the concept.. as u said in full-duplex networking ,a node can send and receive at the same time .. But what Im asking is what if two or more stations want to send frames to the same node ..ie two or more stations intend to send data to the same node .. in that case the data from the two sending devices would collide at the receiver side and receiver may get garbled data.. ??

As you know a collision occures when two devices effectivly connected to the same wire (using a hub) attempt to send data at the same time. This results in a garbled message on the wire, both computers detect this and back off for a period of time then try to resend.

A bridge or switch maintains a buffer or queue for each port, if two computers on two different switch ports (different collision domains) send data to a host on a third port / collision domain, the switch will add both data frames to the queue for that port and both will be sent - one after the other.

Make sense?

ggauravr · February 2010

perfectly makes sense mikme2te.. thanks a lot..that was wat i wanted to know ..thanks again..

collision in switched systems ?

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