On 28 Oct 2005 at 13:20, Toomas Piibe wrote:

> All switches what I have seen few years are auto-sense
> feature. In one case it saved some money because I
> personally couldn't go to buy cables and when I start
> install LAN I discovered that half of cables are crossover.
> But LAN is working.
>
> I don't have seen new hubs some years maybe Ann has
> actually switch?
>
> Toomas


  Ann specified a SynOptics "Lattis" model, and there are several hubs
marketed under that name.

  A hub and a sitch both fulfill the same role in a network topology.  But
most hubs do it in fairly simple circuitry, and can in fact operate without
any kind of examination of the network data, forwarding each bit as it is
received.  A switch, on the other hand, must examine address details in
every packet -- this almost always requires a "store and forward" apporach
where a packet is received, examined, and dispatched.  A switch eliminates
collisions, so full duplex (independent simultaneous send and receive) can
be used (which usually means higher throuput), but there are some
applications where the latency introduced by a switch is unacceptable, and
so hubs are unlikely to disappear completely.

  Auto-sense of cable polarity is a common and useful feature in a small
home switch/router, but trying to build it into a hub could be very
difficult.  (SynOptics refers to several of their models as "managed" hubs,
so it's perhaps not *entirely* out of the question....)

David Gillett

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