The WiFi AP need fast link so the switch need fast port and faster Uplink and 
the worse is the bandwidth require for server backup and VM moving.

10 Mbs share was more then enough and now, we will install 4 x 40Gbs links 
between the Cisco Nexus 6004 and each of it’s  FEX in  Top of the Rack mode!!!!

De : [email protected] [mailto:[email protected]] De 
la part de Matthew W. Ross
Envoyé : 28 mai 2014 13:36
À : [email protected]
Objet : Re: [NTSysADM] RE: Check cable run length

Ah, Cat-3...

When our school district got an old building as a new school, each room had a 
25-pair of cat-3 cable terminated just above the door of each room. This made 
wiring for the building extremely simple, as all we had to do was get the 
network to the door. The 25-pair carried it all back to MDF. Since then, we 
have re-wired to Cat-5e.

Also, a previous tech had an interesting idea on how he would save cable: Each 
cable he used was setup the same way: 2 pair were used for Ethernet (Orange and 
Green), 1 pair for Voice (1 Blue) and the brown pair was used for Appletalk. 
Only the Appletalk needed a special cable (terminated to an RJ45 to pins 7 and 
8). Needless to say, it was both genius and quite the hassle to fix later.
Last, It's amazing how little bandwidth is actually used by the end user. 
Except for saving some big files, 10Mbit would likely _still_ be enough for the 
average user. We have been upgrading our network capacity, but we are now 
focusing on wireless instead of the wired network, as it seems that is where 
the next big push for bandwidth is.


--Matt Ross
Ephrata School District

Bourque Daniel 
<[email protected]<mailto:[email protected]>> , 
5/28/2014 9:59 AM:
Never used it in prod but it was a fun test

PS: 10Base-T was design to work on CAT3 cable at the start!!!

Daniel Bourque


----- Message d'origine -----
De : Ben Scott [mailto:[email protected]<mailto:[email protected]>]
Envoyé : Wednesday, May 28, 2014 12:47 PM
À : [email protected]<mailto:[email protected]> 
<[email protected]<mailto:[email protected]>>
Objet : Re: [NTSysADM] RE: Check cable run length

On Fri, May 23, 2014 at 2:40 PM, Bourque Daniel
<[email protected]<mailto:[email protected]>> wrote:
> 10 Mbs Full Duplex link can go very far... I test it for fun with a 300
> meters years ago.. No error for a weekend streaming a radio-station...

 FYI:

 The 100 meter length limit for Ethernet derives from the time it
takes for the jam signal to propagate through the medium after a
collision is detected[1].  The jam signal has to be on the bus long
enough for all sending nodes to detect it.  If the length is too long,
a sender might finish sending before the jam signal arrives.  That's
called a "late collision".  The sender can't retransmit in that event,
so the frame is lost.

 But on a full-duplex link, there are no collisions.  So what's the
next limiting factor?  Attenuation?  Skew?  Crosstalk?

 Well, the IEEE spec doesn't say.  It just says "thou shalt not
exceed 100 meters".  So you're in uncharted territory.  As noted, much
longer lengths will often work.  I've heard claims of 300+ meters
before, and personally seen ~380 feet in production.  But you're on
your own as far as performance and reliability goes.  It may work
fine, or demons may fly out of your nose[2].

-- Ben

[1] http://en.wikipedia.org/wiki/CSMA/CD

[2] http://www.catb.org/jargon/html/N/nasal-demons.html



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