DComTalk.com

Could someone give me a technical reason why, when I connected a cable modem
and three computers to a hub, it was faster than connecting a cable modem
and three computers with a switch?

I know that routers are the solution, but I am in a debate and am drawing on
my past experience. For example, when using a packet sniffer, you want to
be a part of the same collision an broadcast domain. You can do that with a
hub, but you can't with a switch.

It must be the same principle when you only have 2 or 3 computers on the
same network and collisions are not a problem. Am I right and if I am,
could someone explain why?

TIA

From: "RobW" <robwl-no-spam@gmail.com>

| Could someone give me a technical reason why, when I connected a cable modem
| and three computers to a hub, it was faster than connecting a cable modem
| and three computers with a switch?
|
| I know that routers are the solution, but I am in a debate and am drawing on
| my past experience. For example, when using a packet sniffer, you want to
| be a part of the same collision an broadcast domain. You can do that with a
| hub, but you can't with a switch.
|
| It must be the same principle when you only have 2 or 3 computers on the
| same network and collisions are not a problem. Am I right and if I am,
| could someone explain why?
|
| TIA
|

Hubs only retime the signal.

E-switches use active electronic processing electronics and that takes time. That time
introduces a latency. The cheap E-switches have higg latency valuse as compared to more
expensive E-switches. Thus SOHO Routers and SOHO E-switches have high latencies that will
exibit a slightly slowere performace than a hub. This will be more evident on a network
with little use. On a more congested network, the E-switch will perform better because of
the serparation of collision domains.

I have also see then an auto-switching hub (not a dedicated 100Mb/s or 10Mb/s hub) will also
introduce latency as compared with a hub that is a dedicated to 10Mb/s or 100Mb/s.

--
Dave
http://www.claymania.com/removal-trojan-adware.html
http://www.ik-cs.com/got-a-virus.htm

RobW <robwl-no-spam@gmail.com> wrote:

Could someone give me a technical reason why, when I
connected a cable modem and three computers to a hub,
it was faster than connecting a cable modem and three
computers with a switch?

Simple. Hubs are electrical repeaters, merely reforming and
retransmitting waves. They often have a very short delay
times, one bit-time or so.

Switches have intelligence. They look at the destination MAC
and stuff it out the right port. Expensive commercial switches
have a "cut-over" that will start forwarding packets before
they are complete. Cheap SOHO equipment is store and forward,
nothing gets sent out until the full packet is received,
up to 12,000 bit times (1.2 ms at 10Mb/s).

In practice, very rarely is the difference noticeable or important.

-- Robert

"RobW" <robwl-no-spam@gmail.com> wrote in message
news:rKKkf.134848$y_1.223@edtnps89...

Could someone give me a technical reason why, when I connected a cable
modem and three computers to a hub, it was faster than connecting a cable
modem and three computers with a switch?

What does "it was faster" mean? Higher throughput? Higher latency? Less
loss of performance of one data flow when you start another? It could be
that you had some major negotiation problem with the switch, and that caused
performance problems.

DS

Greetings,

Could someone give me a technical reason why, when I connected a cable modem
and three computers to a hub, it was faster than connecting a cable modem
and three computers with a switch?

This sounds like a simple Duplex neogtiation issue between the Switch
and the PC, however there are several possible causes for this....

In practise, there should no difference between using a HUB and a
SWITCH with only 3 machines, as long as BOTH the HUB and the SWITCH
are operating at the same speed (EG 10Mb/Half Duplex). If there IS a
difference, then the most likely cause will be some sort of Ethernet
Negotiation mis-match when using the Etherswitch. The simple solution
is to turn off auto-negotiation by locking each machine to a fixed
configuration that matches the Switch.

A true HUB is only Half Duplex, which is the lowest level of
autonegotiation, whereas a switch should be able to operate in both
Half and Full Duplex modes. The most common form of performance issues
when using Etherswitches is a DUPLEX negotiation mis-match between the
ends (Half at one end, Full at the other), and the net effect of this
is a DRAMATIC decrease in performance.

Note. Be very careful about some Gigabit Ethernet cards, Gig only has
Full Duplex, so when connecting to a lower speed it needs to be able
to switch to Half Duplex, expecially when using a Hub. I have heard
that when some Gig cards are asked for <1Gb, they fail to drop down to
Half Duplex if Autonegotiation starts working (which it will do on an
Etherswitch).

I know that routers are the solution, but I am in a debate and am drawing on
my past experience. For example, when using a packet sniffer, you want to
be a part of the same collision an broadcast domain. You can do that with a
hub, but you can't with a switch.

It depends on the Etherswitch, EG Cisco Switches have a Monitor mode
that allow a port to be replicated and monitored, so it is possible,
but you have to have the facility in the Etherswitch and know what you
are doing....

I hope this helps..............pk.

--
Peter from Auckland.