# Do hubs and switches slow down speeds?



## f0rged

If you have a hub or a switch, and a bunch of computers hooked off that, do you get the total speed of your connection divided by the number of computers connected?

Or are there hubs/switches that replicate the speed, so that each link is 100mb? That doesn't logically make sense if the link is only ever 100mb.

Or both?


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## PohTayToez

It depends.  If you have 10 computers connected to one internet connection through a hub/switch, but only one computer is using that connection, then that one computer's connection will run about the same as it would if it was the only computer connected.  If two computers are downloading something at the same time, then the connection will be split between both, etc.


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## The_Other_One

If my memory serves me correctly, a hub simply broadcasts the incoming signal to all other ports, where as a switch can isolate the ports required for data transmission.  Technically with a switch, you shouldn't loose much, if any network bandwidth.  However your internet will slow down if every computer accesses it on the network.


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## Viking

like the_other_one says  with a hub whatever goes in one port goes out the other ports. A switch can actually speed up a network b/c it can break up broadcast domains. Each port on a switch or a node can be a different network. Data can be transmitted smoothly between networks. In tcp/ip the data packet has the recipients network address and goes to every network card on the lan and the network card with the id that matches is the only one that will receive the data packet, unless it is a "broadcast ( ..or is it multicast?)" , then it goes to everyone. There are collisions of data packets when two or more NICs try to send data @ the same time. As long as you are not going to connect up 30 or 100s of PCs I would not worry about speed.


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## JamesC

^ or when someone is sniffing, they can grab them too. >.>

Anyway, it really depends on bandwidth as well. On a regular home DSL connection for example, you can have about 3-4 computers before you notice any differences. 

Think of it like this: your streaming video from youtube (let that represent bumper to bumper traffic on a freeway) then someone checks their email (car tries to merge in to the traffic) and it slows down the video stream or email (people get mad and there is road rage). A switch would be like a traffic cop, telling people when to go and who can merge.

So I guess a switch would increase speed on more active/crowded networks, but having a traffic cop on an empty freeway might cause a little distraction (only nanoseconds).

If everyone is just browsing the web or chatting, there wouldn't be any noticeable difference. When someone does some heavy load activities, then it is an issue, which is why a lot of bigger networks require load balancing of some sort. 

So it's not really divided evenly, people just use all of what is available.


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## 99F

that analogy confused me can you explain once i replace my lost brain cells??


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## Viking

what a switch does is break up a broadcast domain.

lets say you have 100 computers on one lan. All data packets circulate through the whole lan. When other network cards try to send their data there could be collisions of data packets. If that happens the NIC( network interface card) waits and retransmits, if it happens again, the nic waits a little long, ...again alittle more longer...etc .So that is what you see on a crowded LAN as latency. So as JamesC's scenario the switch acts like a data packet traffic cop. If you take those 100 PC's and say divide them up into 5 networks of 20 PC's . Each network is plugged into one connector on the switch. The switch ( data traffic cop) knows which addresses are on which of the 5 LANs. So instead of ALL the data circling through all 100 PCs it( the data) is confined to ONE of the 5 LANs.


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## JamesC

Yeah my example was pretty bad...

Thanks Viking


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## PohTayToez

I thought it was an awesome example, and I'm definitely going to use it some time.


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## Monoliths

Viking said:


> what a switch does is break up a broadcast domain.



If I remember right routers break up broadcast domains and switches break up collision domains (which is what your example is explaining I think).

Unless we are talking about VLans that is...


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## Viking

you could be right,  sometimes when there are solar flares my thinking gets disrupted. Thank you for catching that.... should of had my tin foil linned hat on.


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## JamesC

Someone actually asked today, what was the difference between a switch and a router. I actually had to think hard there for a second. 

I know routers are generally more intelligent, but I am thinking not just because they have basic packet forwarding abilities like a switch, but also can have firewalls and dhcp? Where as switches cannot? Or can switches have those too? Also because they can connect 2+ networks (ie WAN/LAN) where switches are strictly 1 network?

Should of paid more attention in Network Theory


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## Viking

Also I beleive that all the networks connected or computers have to be on the same subnet where as routers can negotiate different subnets.
Also a switch can convert between different collison domains as part of a broadcast domain and a router can negotiate between different broadcast domains. 
Routers can also have NAT and SPI.   You usually get only one ip address from  your isp. NAT takes that one ip and lies to your isp saying yup only one computer connected. It then keeps track of all your internet requests and what ip on your LAN made the request, turns around and Uses the WAN ip from your isp to make the request. As the data comes back NAT sends it to the correct ip address on your LAN.  
SPI just makes sure that all the data packets coming in were actually requested by someone on YOUR lan.... to keep hackers out.


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