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Re: Ethernet Switching question
michael_d #335894 01/28/11 03:08 AM
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Think of it as the part of the switch that ties the ports together. When you leave one switch and move to another, you're operating on a different backplane.

But the better way to phrase my initial comment is to say, latency within one switch will be the tiniest bit better than the latency between two switches.

Also the backplane throughput is usually higher than any individual port. So you can have multiple conversations all at full speed in one switch, but if multiple devices on one switch are trying to talk to multiple devices on another, they'll all have to go through the bottle neck of the connection between them. (This usually isn't an issue until multiple servers are involved.)


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Re: Ethernet Switching question
michael_d #335954 01/28/11 12:49 PM
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Originally Posted By: michael_d
OK, just for clarification.... If I can not find a 16 port switch, just get a second switch and plug it into the existing 8 port switch? Depending on what they have, and the switch dimensions, I may have to go with the second switch. I only have 2.25" to work with, as that is my shelf height.


Here's one that has 16 ports and is only 1.7" tall:

http://www.newegg.com/Product/Product.aspx?Item=N82E16817111012


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Re: Ethernet Switching question
SRoode #336109 01/28/11 10:44 PM
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Thanks for all the help fellas. The local RS had a Cisco 8 port switch like the one I already had. I hooked each switch to my router and put the devices that talk to each other on the same switch. Now all LAN jacks in the house are hot and ready for use. It's probably just wishful thinking, but I believe things are running a tad more reliable.

Re: Ethernet Switching question
michael_d #336110 01/28/11 10:48 PM
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I think you should conduct a double blind study before making claims like that. laugh


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Re: Ethernet Switching question
ClubNeon #336115 01/28/11 11:05 PM
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LOL smile

Well, at least my wireing LOOKS better. I forgot how much a PITA building patch cables is. That and I think my vision is getting worse. Those little wires are a lot harder to keep in order now than they were before.

Re: Ethernet Switching question
michael_d #336183 01/29/11 06:04 AM
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I need to redo the new ethernet jacks I just put in the basement. I apparently did something wrong on both of them. Oops! But yeah, I've always just bought my patch cables from Monoprice because they're cheap, and I don't like making more cables than I have to.

Re: Ethernet Switching question
CV #336186 01/29/11 06:08 AM
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I knew I had arrived, when I no longer had to make Ethernet cables, I could just assign someone to the job.

Of course now when I try to make them, they only work about 50% of the time, it takes me 15 minutes per end, and they look like crap.

Last edited by ClubNeon; 01/29/11 06:08 AM.

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Re: Ethernet Switching question
ClubNeon #336210 01/29/11 06:36 PM
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I like making my cables, just to have them the exact length I need, nothing more nothing less. It makes cable organizing a little easier without any extra wire to worry about looping etc.


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Re: Ethernet Switching question
jakewash #336235 01/29/11 09:07 PM
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Did you know with gigabit and higher, it's against spec to make patch cables the exact length you need? The issue is with short cables.

I found this oh HP's site, but it is noted in other places too:

Quote:
It is possible that short cables will not meet requirements due to the impact of Return Loss.

For example, if a cable is 110ohms in impedance and it is plugged into a port with impedance from 100ohms at 1MHz to 85 ohms at 100MHz, reflections may occur because the cable has almost no attenuation.

Multiple reflections may result in this scenario, possibly resulting in standing waves that build in strength until the signal at the receiver is overwhelmed.

Therefore, it is necessary for a cable assembly (.5m or 2.5m) to meet Return Loss, Near End Crosstalk, and the other specifications set forth in the IEEE 802.3ab 1000BASE-T standard.

Cables under 2.5m have strict requirements to length. They basically have to be of multiples at to not promote standing waves. You have to know the wavelength of the signal, based on the propagation rate of electrons in that particular cable, at a particular frequency. You don't want the cable to be of a length that results in waveform peaks standing at the ends of the cables, else they'll be reflected back by the receiver (because it doesn't attenuate the signal enough) and cancel out other arriving signals.

Under 0.5m it's possible for the reflections to move all the way up the cable and reflect again from the sending side. This causes true standing waves, and will make communication at speed impossible.

Once a cable hits about 2.5m it'll offer enough attenuation of it's own, that combined with the receiver there won't be enough energy to cause interference reflecting back up the line.


Pioneer PDP-5020FD, Marantz SR6011
Axiom M5HP, VP160HP, QS8
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