1 of 2: Questions about switches and hubs . . .
drowd
Texas
ok, i am in a networking class right now as part of my degree plan, and my prof has a lot of experience in the work force, but i tried to ask him today some questions about the differences between switches and hubs, and he hemmed and hawed but never really answered me. first off, my assumptions:
before this point, i had always assumed that the difference between hubs and switches was that hubs were all on the same wire. you can have however many ports, but they all ultimately are on the same wire, thus lots of collisions, etc. now, i thought the difference with a switch, was that each port had its own connection to every other port. so, on a 4 port switch, port 1 has a direct connection to port 2, port 3, and port 4. port 2 has a direct connection to port 1, port 3, and port 4, etc. and those were my assumptions up until recently . . .
so, my prof was teaching that a switch is ALSO on the same circuit like a hub, and that they are all connected to the same line, but they are different from hubs. hubs send out packets to all ports all the time, and if that packet is meant for that computer, it is accepted, otherwise it goes to the bit bucket. switches on the other hand, the first packet is sent to all ports, but once the acknowledgement is recieved from the port, it only sends to that port through MAC addresses, thus not flooding the rest of the switch. so he said that these virtual circuits are what makes switches special because this load balances and keeps the bus collision free, but that they ARE on the same bus as all the other ports.
so after class, i set up this scenario with this sort of simple switch
| 1 | 2 | 3 | 4 |
just four ports, and then i said something to the effect of "port 1 and 3 have an ideal connection and are transferring files at the hypothetical 100 Mbps. port 2 and 4 have computers connected, but they are not communicating. if all of these ports are on the same wire, how will transmission speed no be reduced in half if 2 and 4 start trying to transfer at this speed?" with my previous assumptions, that they all have their dedicated lines, it makes sense. and i have even experienced this scenario at lan partys where 1 and 3 are xfering and 2 and 4 are xfering and there is no slow down whatsoever with a switch. a switch being all on the same wire just doesnt make sense to me . . .
anyway, that is sort of my problem. if anyone would like to clarify and correct me or my professor, it would be greatly appreciated. thanks a lot . . .
and this pic is for my prof :-\
/me scratches his head.
before this point, i had always assumed that the difference between hubs and switches was that hubs were all on the same wire. you can have however many ports, but they all ultimately are on the same wire, thus lots of collisions, etc. now, i thought the difference with a switch, was that each port had its own connection to every other port. so, on a 4 port switch, port 1 has a direct connection to port 2, port 3, and port 4. port 2 has a direct connection to port 1, port 3, and port 4, etc. and those were my assumptions up until recently . . .
so, my prof was teaching that a switch is ALSO on the same circuit like a hub, and that they are all connected to the same line, but they are different from hubs. hubs send out packets to all ports all the time, and if that packet is meant for that computer, it is accepted, otherwise it goes to the bit bucket. switches on the other hand, the first packet is sent to all ports, but once the acknowledgement is recieved from the port, it only sends to that port through MAC addresses, thus not flooding the rest of the switch. so he said that these virtual circuits are what makes switches special because this load balances and keeps the bus collision free, but that they ARE on the same bus as all the other ports.
so after class, i set up this scenario with this sort of simple switch
| 1 | 2 | 3 | 4 |
just four ports, and then i said something to the effect of "port 1 and 3 have an ideal connection and are transferring files at the hypothetical 100 Mbps. port 2 and 4 have computers connected, but they are not communicating. if all of these ports are on the same wire, how will transmission speed no be reduced in half if 2 and 4 start trying to transfer at this speed?" with my previous assumptions, that they all have their dedicated lines, it makes sense. and i have even experienced this scenario at lan partys where 1 and 3 are xfering and 2 and 4 are xfering and there is no slow down whatsoever with a switch. a switch being all on the same wire just doesnt make sense to me . . .
anyway, that is sort of my problem. if anyone would like to clarify and correct me or my professor, it would be greatly appreciated. thanks a lot . . .
and this pic is for my prof :-\
/me scratches his head.
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Comments
Good threads, but I can't be 100% certain that either of my answers to them are correct, just my 'assumptions' as well.