Difference between a switch and a hub

"People tend to benefit from a switch over a hub if their network has four or more computers, or if they want to use their home network for applications that generate significant amounts of network traffic, like video editing over the network.

Technically speaking, hubs operate using a broadcast model and switches operate using a virtual circuit model. When four computers are connected to a hub, for example, and two of those computers communicate with each other, hubs simply pass through all network traffic to each of the four computers. Switches, on the other hand, are capable of determining the destination of each individual traffic element (such as an Ethernet frame) and selectively forwarding data to the one computer that actually needs it. By generating less network traffic in delivering messages, a switch performs better than a hub on busy networks."

For example, suppose you have computers A B C & D on a gigabit network, and A & B are talking to each other as well as C & D talking to each other. With a hub, anything A says goes to C & D as well as to B. If both pairs are transmitting data the total speed is limited to 1Gbps, so A & B communicate at 500Mbps and C & D communicate at 500Mbps. With a switch, A & B become their own private network and C & D become their own private network. Both pairs can send data at the full 1Gbps simultaneously. As you can imagine, this disparity grows rapidly as more computers are communicating through a hub. With a switch the speed between each pair of computers remains near the maximum no matter how many other computers are connected.

Considering that a 24 port gigabit switch can now be purchased for a tiny fraction of the price of a 4 port hub just a few years ago, there probably isn't any reason to consider a hub.

Thanks for the explanations. My 10/100 hub really slows down when I print pictures on two printers at the same time. Now I know why. I was going to get another hub (switch) but three out of four recently upgraded computers have only 10/100 lans. The USB 2.0 drives kind of take up the slack however.
JJK

getting back to the interface card question for a moment, should I be using a garden variety gig card I can pick up at Fry's or a more expensive card that handles the network transactions itself, pulling it away from the host cpu?

Reid C

Venerable 3Com is giving up the Network adapter business... But I'm very partial to NICs with Intel silicon. The big issue for me is that Intel is very good about posting updates for OS or network changes years after the NIC was manufactured.

That's just my .02 cents.

Second vote for Intel here. I'm not up on their current specs so i can't make a specific recommendation, but they've always been flawless. I've been using Intel NICs for nearly 15 years with never a hitch.

Cards based on the RealTek chipset seem ultra reliable and dependable too. It's quite surprising for such a low-priced card. I suspect though that part of the low prices may be due to no on-card processing. That being said, in side-by-side speed tests i've never seen anything run faster than RealTek NICs.

I would suggest looking at reviews on various computer magazines (though I'm not sure if they still review NICs much).

Probably most of the features of an expensive NIC are fluff that you don't need (like VLANs, IP filtering, and so on). But there is in fact a difference in the sustained throughput of different NICs. 1Gbps is theoretical bandwidth. Real bandwidth is determined by the capabilites of the hardware, the drivers, and the operating system.

Also, another benefit of a switch is bidirectional communication. On a hub, communication is one-way. On a switch, a network node can transmit and receive at the same time. So theoretically, you could get 2Gbps on a switched network (1G xmit plus 1G receive). But that's only theory. I can't think of too many scenarios where simultaneous transmit and receive will happen at full sustained speed.

Also, Asus has some new motherboard designs where they have dual Intel GB NICs that can be used for "teaming". It means you connect both NICs to another mobo with the same technology and you double the throughput. But it seems to be only a point-to-point solution, i.e. for two directly connected computers with no switch or hub in the middle. But I could be wrong about some of the details. I haven't researched it much.

Another thing to consider is that if one is editing DV or HDV, even a 100Mbps connection will still allow 3 simultaneous A/V streams with room to spare. A GB connection, even if it's a scummy one only running at half speed, will allow at least 16 simultaneous HDV streams. I doubt the host PC will be able to do anything useful with that much data in real time. In other words, i wouldn't lose any sleep worrying about which is the most efficient card.