hub in full duplex

If you use a hub in full duplex, are you any more likely to have collisions than if you used a switch in full duplex?

Reply to
bob
Loading thread data ...

Where did you manage to find a full duplex hub?

formatting link

Reply to
Walter Roberson

Because of the design of a true hub, you cannot use it in full duplex. Full duplex implies having

*simultaneous* transmission and reception.

All hubs are, by definition, half duplex devices. Period. End of story.

With a hub, anything recieved is immediately retransmitted out all ports on the hub, which means that you can't transmit *while* you are receiving.

A crossover cable is a different matter since the transmit and receive paths are physically separate.

This has been beaten to death several times before in this and other newsgroups.

John

-- John P. Dearing A+, Network+, Server+ To reply just drop "YOUR PANTS" in my addy!!

Reply to
John P. Dearing

(snip)

What is a 'true hub'?

Where does it say this? Do you have a reference to an IEEE standard?

There are two types of hubs, repeaters and bridges, the latter commonly known as switches. As the first hubs were repeaters, and it is easier to write a three letter word, hub was often used for repeater, but the word itself does not imply that.

As I understand it, many switches are being sold described as hubs, hopefully not described as repeaters.

-- glen

Reply to
glen herrmannsfeldt

Perhaps I should have been more precise in defining a "hub". Sorry about that.

In the context of this discussion, a hub is what you are referring to as a multiport ethernet repeater, as opposed to a multiport ethernet bridge, commonly referred to as an ethernet switch.

In that context, an ethernet hub can't operate in full duplex because once a signal is received on one port, it will be immediately sent out on all the other ports. This design operates just like ethernet on coax, while one station is transmitting, the others must listen. If a second station were to start transmitting it would be a collision.

I rather doubt that very many networking professionals would make that mistake. In my experience, a device called a hub means ethernet repeater and a switch means something completely different.

While it hasn't been my experience, I suppose there could be some misrepresentation going on out there.

I hope that we've now completely beaten this old horse to death. Again. 8-)

Cheers!

John

Reply to
John P. Dearing

(snip)

Note that the OP never mentioned repeater.

(snip)

How is hub defined in the IEEE standards?

There have been reports here of people buying what they thought were repeaters, and found that they were switches. Hopefully they properly note the appropriate standards.

-- glen

Reply to
glen herrmannsfeldt

Yup, but the OP asked to compare hubs and switches, implying that to the OP a hub is something different than a switch. Are there different kinds of hubs that are -not- bridges?

Reply to
Walter Roberson

Glenn is playing word games with you I believe. "Hub" per se is not defined in the standards as far as I know. At least not for Ethernet--the term really comes from Arcnet, where "hubs" of two kinds are defined, and the device which served a similar function in Ethernet when 10baseT started becoming popular came to be called a "hub" even though technically speaking it was a "multiport repeater"--with 10base2 or 10base5 it was sometimes called a "multiport repeater" and sometimes a "concentrator" but seldom a "hub".

Hubs, as the term was used when such devices first came on the market, were not bridges in any sense, they were simple repeaters. After a while, when multiple speeds became available, "dual-speed hubs" that consisted of repeaters for 10 Mb/sec and for 100 Mb/sec with a bridge between the two and either manual or automatic switching of ports from one side of the bridge to the other became available. These days a "hub" can be just about anything.

Reply to
J. Clarke

Rage, Rage! Against the dying of the terms! :)

Hub == repeater Switch == bridge

Don't let the salescritters muddy the waters, it only causes confusion later.

rick jones

Reply to
Rick Jones

Cabling-Design.com Forums website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.