PLUG IN THE %&$* HUB!

[technical.angel]

Honestly, I'm not sure if it was a hub, router or switch. Once upon a time, I knew the difference between the three, and I know it involves how it routes bandwith, but I don't really know or care now.

And, if you can ask that question, you know NOTHING about technology in education!!!

[Chromatix]

Really, the distinction is between hubs, switches, *bridges* and routers (in increasing order of sophistication).

Hubs understand only the lowest, physical layer of the network stack. They receive a packet on any port and immediately broadcast it, indiscriminately, on all other ports. Many are capable of detecting a malfunctioning port (or device attached to it) and isolating it from the network. All devices attached to a hub must be operating on half-duplex and the same speed of signalling - most hubs only supported the original 10MHz speed.

Switches understand the second layer of the stack, and are capable of storing each packet in a queue, and selectively forwarding it on a single appropriate port. They do this by examining the MAC addresses in the Ethernet frames. This hugely increases aggregate capacity, because pairs of ports can operate independently of each other. Store-and-forward also allows full-duplex signalling, which also increases capacity, and allows different ports to use different signalling types and speeds (so 10base-T can now talk to 100base-TX).

Switches became roughly the same price as hubs some years ago, so their better performance meant that hubs essentially disappeared. Except for "USB hubs" which are not the same thing - USB is not a network. If you come across an old network device, a big clue for telling the difference is that a hub *cannot* support full-duplex connections.

Bridges are a step up from switches, because they understand two different network standards and forward packets between them. For example, some old networks use ATM for long runs between buildings, but Ethernet inside the buildings. Bridges are still fairly dumb devices.

Routers are sophisticated devices which understand the third layer (and sometimes higher layers) of the network stack, where IP (Internet Protocol, as in TCP/IP) lives. Their job is to forward packets between different networks when they need to be forwarded, and to avoid forwarding packets that don't need to be, with high accuracy. Basic routers are now so cheap that almost every broadband subscriber has one. Proper, commercial-grade routers are still very expensive.

A typical consumer broadband router actually contains a router, a bridge *and* a switch. The switch is the central part, forming the main interface to the private network (often of just one computer, but oh well). The bridge hangs off this and supplies the wireless network, while the router (of a particular kind called a Network Address Translation router) attaches the whole lot to the Internet. I hate these things because they are designed incompetently and built down to a price, but they're getting steadily harder to avoid. I'd much rather have an Ethernet-to-ADSL2+ bridge, and let *me* do the routing if necessary.

[Ironclad Alibi]

Who uses hubs any more? Last time I saw a hub in use was at least 5 years ago, and I was replacing it with a switch.

Just curious

Your comment reminded me of a User Friendly comic wherein one of the characters was questioning whether anyone used portals any more.

And then there is the following ditty about hosts sung to the tune of the Mr. Ed theme song.

A host is a host,
From coast to coast
And nobody talks to a host that's close,
Unless the host that isn't close
Is busy, hung, or dead.