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Old 01-30-2009, 03:20 PM   #1
lucazorzi
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Gigabit Switch and 100 Mbit peripherals


Hi everyone!

I would like to upgrade my LAN from 100 Mbps to 1 Gbps, but one of my peripherals (a NSLU2) has only a 10/100 Mbps network card.

The question is: if there is a 100 Mbps peripheral plugged into a gigabit switch, will it slow down the gigabit peripherals connected to the switch?

Thanks in advance,
Luca
 
Old 01-30-2009, 04:01 PM   #2
johnsfine
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I just did a bunch of performance tests (ping with large packet size while other pairs of computers loaded connections with file transfer) on a LAN with a mixture of 1Gb and 100Mb and was very impressed with the way our Netgear and D-Link 1Gb switches deal with the mixed load. (I was fixing a LAN performance problem with some obsolete Dell and Cisco LAN equipment).

I didn't measure well enough to be certain that everything that could be independent is independent. But to the extent I could measure, it was.

A "switch" (unlike older "hubs") should be able run independent paths fully in parallel.

Example 1:
X at 100Mb talks through switch to Y at 1Gb
meanwhile U at 1Gb talks through same switch to V at 1Gb.
The traffic from X to Y has no effect on the traffic from U to V.

Example 2:
X at 100Mb talks through switch to Y at 1Gb
meanwhile U at 1Gb talks through same switch to Y at 1Gb.

That's the case that I'm unsure of myself. What are the characteristics of speed shift at the switch between the 100Mb link to X and the 1Gb link to Y? If contention from U means X only gets an effective 50Mb path to Y, does that tie up 50% of the potential 1Gb path from U to Y or only 50Mb of it or where in between?

But I think you are worried about much more severe effects that don't happen (so don't worry about it). Plugging in a 100Mb connection will do nothing to the other performance on your LAN and sending 100Mb packets won't do enough to matter (if anything at all).

Last edited by johnsfine; 01-30-2009 at 04:03 PM.
 
Old 01-30-2009, 04:04 PM   #3
CoderMan
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Quote:
Originally Posted by lucazorzi View Post
Hi everyone!

I would like to upgrade my LAN from 100 Mbps to 1 Gbps, but one of my peripherals (a NSLU2) has only a 10/100 Mbps network card.

The question is: if there is a 100 Mbps peripheral plugged into a gigabit switch, will it slow down the gigabit peripherals connected to the switch?

Thanks in advance,
Luca
No it won't. Of course, other devices will only be able to talk to the NSLU2 at 100 Mbps.

Switches work by creating distinct pathways between the ports when needed. If a device on one port is communicating at 1 Gbps with a device on another port, it doesn't matter whether or not there is a device on a third port that is slower.
 
Old 01-30-2009, 04:12 PM   #4
lucazorzi
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Thanks for your quick replies!
 
  


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