Switches: performance

isjones

Hi,

Just started studying Cisco...
Switches, how do they perform if multiple devices simultaneously attempt to communicate with a single device. Specifically do they send a jam signal as with a basic ethernet bus if they become overloaded?

I think what I am asking is how do switches operate internally? Do they/can they become overwhelmed?

TIA, Ian

cisco_kidd

isjones wrote: »

Hi,

Just started studying Cisco...
Switches, how do they perform if multiple devices simultaneously attempt to communicate with a single device. Specifically do they send a jam signal as with a basic ethernet bus if they become overloaded?

I think what I am asking is how do switches operate internally? Do they/can they become overwhelmed?

TIA, Ian

First let's go over the basicis. Devices connected to a switch can operate at full duplex, whereas devices connected to a hub would operate more efficiently in half duplex. A hub and all it's ports is 1 collision domain, whereas an interface on a switch is a collision domain.

The description you referenced above "jam signals" and "ethernet" would only apply to a hub called CDMA/CD. Modern networks today use switches and full duplex connections where CDMA/CD is not needed (obsolete), so on a switch, you don't have jam signals. If you have a 100mbps connection on a switch at full duplex, it can transmit at 100mbps and receive at 100mbps unlike a hub and your description above. So, basically, a switch can more efficiently use a wire by sending AND receiving at the same time than a hub which can only send OR receive.