Fundamental Networking Confusion

[it_sav]

I've been searching for the answer to this question for some time, but apparently am not phrasing it well. I hope someone here can help me.

This feels like a really fundamental misunderstanding on my part, but I can't seem to wrap my head around it.

I've got a couple scenarios below all dealing with bandwidth with varying rates across legs of the journey.

Scenarios:
1. 2 - 10/100 switches with a gigabit uplink to each other. Host A and B are on Switch A, and Host C and D are on Switch B. If A is sending or receiving data from Host C at 100Mb/s and Host B is sending or receiving data from Host D at 100 Mb/s, will the fact that there is a gigibit uplink matter at all?

2. Host A has a gigabit NIC and is plugged into a gigabit port on a switch. Hosts B and C are both 100 Mb/s. If both B and C are transferring large files to or from Host A at the same time, will the fact that Host A has a gigabit NIC matter at all?

3. Network A has a 10 Mb/s WAN link. Remote Networks B and C both have 1.5 Mb/s WAN links. If both B and C are transferring large files to or from Network A at the same time, will the fact that Host A has a larger WAN link matter at all?

Any thoughts, further resources, or links would be much appreciated.

Thanks!

[ua549]

1. Yes, both switches can process more traffic faster from a number of sources.

2. Yes, once again the faster link allows more traffic into the switch where it is distributed to any number of slower links.

3. Yes.

What you are not understanding is the fact that more than one of the slow links from a switch to end node can be "active" at any given moment in time. That is the big advantage of a switch over a hub.

[it_sav]

Thank you very much for your reply. I'd like to rephrase and see if i'm getting this.

So in scenario 1, physically switch A receives the data from both hosts A and B at the slower speed, forwards the data to switch B at the faster speed. Then switch B holds the data in a buffer while it meters the data out to hosts C and D at the slower speed again. Is that right?

Thanks!

[ua549]

Yes, that is correct.

[it_sav]

Got it, thanks!