gigabit>gigabit ethernet question

J_M


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My goal is to have a gigabit connection between a MacPro(intel) and a PowerMac(G5) tower. These computers will be connected via 2 gigabit switches but there will be other 10/100 devices connected to these switches and a router/gateway that is 10/100mbps.

Will the 2 computers connected via gigabit switches connect at 1000 speed? or will the switch require the data to run back through the router first?

I hope I explained the question, if not I'll try again. thanks

No code has to be inserted here.

all connected via Cat5e / Cat6
 
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J_M


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a little clarification

>a variety of 100/1000 computers, printers

sounds like more than it really is.... there are 2-XP boxes, 1-Win7, a network printer, another WAP and the MacPro connected to the second gigabit switch.
 

dtravis7


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I think it depends on the switch. I know for sure my Dlink 8-port Gigabit says it will do Gigablt even if 100BT computers are connected to it and in my tests that is what it's doing. I get full gigabit speeds with the Gigabit computers and 100BT speed with the older systems.

I believe my 5-Port Netgear also does this.
 
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Hi Dennis

I have a 8-Port Gigabit GREENnet Switch TEG-S80g and the 5-port version. They do say they handle auto-negotiation (hopefully). Someone posted on an older dead forum thread that all data still needs to go through the router which would require it to flow a through 100mbps device. That seems like it would be an incredible burden on the router to handle all data.

Is it possible that data would only move between the 2 computers and the switches and not leave the portion of the network that is solely 1000mbps?

thanks again, j
 
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J_M


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other than tossing around large files and watching the Activity Monitor is there any other way of checking the speed of transfer?
 

dtravis7


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I am running a Dlink DIR-655 Router with all Gigabit ports. So my whole network except for a few old computers hung on it is all Gigabit.
 
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ah, OK, so I still might have a problem with my older router.

I was looking at the DLink DIR-655, I might have to give it a try.

thanks
 

dtravis7


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Do remember one thing, if you transfer large files and use activity monitor, the speed will also be limited by how fast the hard drive can write in the system on the receiving end! Gigabit is so fast, older hard drives will affect the speed as they can only receive data so fast! :D Grin

There are utilities to test network speed. Let me see what I can find for OSX. So far with OSX I have just used the method you described as it tells me if it's working or not.
 
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You are probably right about the speed.

I am going to use this as a semi-offsite backup with CarbonCopyCloner which is great and I use on my local drives. I figure that anything I can do to cleanup the pipes first will also help keep the data good too.
 
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update -

I received the following from Trendnet support, it seems that the data would flow between the switches/computers and not need to touch the slower ports of the router.

You should not see any loss of speed using the switches as the gigabit switches should pass through the data to the PC computers without using the router.
 
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Most all modern switches available for purchase today (and in the last few years) are capable of auto-negotiating speeds depending on what type of device is plugged into that port. In other words, Gigabit devices will communicate at Gigabit speeds and 100 Mbit devices will communicate at 100 Mbit speeds. Your printer may or may not be 10 Mbit, if so it will communicate at 10 Mbit speeds (more than enough for a printer).

Also, the switch is capable of passing data in between devices attached to the switch locally. So, if PC-A and PC-B are both plugged into the Gigabit switch, and they both have Gigabit NICs, you will get Gigabit speeds. The only time data will need to pass through the router is if it is leaving your network (or if you happen to be trying to communicate with a device plugged into the LAN ports on the router, if you have them). If your router also functions as a DHCP and/or DNS server as most consumer routers do, that (very small amount of) data will need to go to the router as well.
 
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thanks for the response!

If your router also functions as a DHCP and/or DNS server as most consumer routers do, that (very small amount of) data will need to go to the router as well.

If PC-A is connected to PC-B, and the router does handle DHCP, are there 2 events that occur - the router actively directs the traffic but the data flows directly from PC-PC via the switches?

Or, since the local IP has already been assigned to the PC's they would communicate independent of the router until there is a request to renew the IP?

thanks again,

j
 
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Sorry, I threw that last bit in there just to show that there MAY still be local traffic that has to go to the router, but realize it might have been a bit confusing now.

So, assuming that PC-A and PC-B are both connected to the switch, and the switch is connected to the router...

When you turn on either PC, one of the startup tasks the PC does is request an IP address from the DHCP server (router). This traffic obviously has to go to the router, since the router is the device handling the request. After both devices are assigned IP addresses, however, traffic is handled directly by the switch, unless it needs to be routed outside your network.

To answer your question, to simply transfer data between two devices, the router does not necessarily get involved.

A fairly simple example, PC-A wraps up some data in a packet and sends it off through the NIC. The switch gets the packet and looks at the MAC address of the destination device. The switch has an internal database of all the MAC addresses of devices currently connected to it, so it knows whether the destination device is local (on the switch) or not. If the destination device is attached to a port on the switch, it is sent directly to that port and on to the destination device.

If the destination device is not located locally on the switch, it knows that it has to pass the packet on to the router, so that it can be routed outside the network.

This gets way more complicated if you really want to go in depth, but for a home user this is all you really need to know.

For your typical home setup of Internet > Router > Switch > Various devices, you can assume that all substantial traffic between the devices in your home are handled directly by the switch (that is, file transfers, print jobs, etc.) and anything going out to or coming in from the Internet needs to go through the router. Since most home Internet plans are way less that the 100 Mbit/s speeds that the ports on your router probably provide, this is not an issue.
 
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great information!

Thanks for taking the time to respond, it's very much appreciated.

j
 

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