WS-X6748-GE-TX question

[FANCYpete]

Trying to calculate how many end-users would be able to pull down data at 100Mbs each from a Server that has a 1Gb connection to a WS-X6748-GE-TX card, presuming worst-case scenario in which every user would be maxing out their respective 100MB connection, bearing in mind that the server’s 1GB connection resides on a ws-x6748-ge-tx card that has a 2x20GB switch fabric connection on the backplane to the SUP720 supervisor module.

SERVER-->SWITCH1(1GB port on ws-x6748-ge-tx)-->(2 x 1GB Uplink)SWITCH2-->(2 x 1GB Uplink)SWITCH3-->END USERS w/ 100Mb connections

I'm the Fanciest of the Fancy...INDEED

 

[FANCYpete]

I realize this is a hard question to answer... of course I realize the bottleneck is the 1GB server connection...BUT, because it's on a 6748-ge-tx, it does have 40GB to the backplane to work with as far as buffering / queueing packets out of the port...none of the floors where the end users connect have more than 74 users...so ~7.4Gb maximum (worst-case) scenario ..if every user was truly pulling their 100Mb worth of data down from the server.... 7.4Gb vs 40Gb.....the hardware would handle it on the switch.... might be a little slow if that were to happen but the traffic would get through, right?


I'm the Fanciest of the Fancy...INDEED

 

[dgrizzard]

The buffers are so teeny tiny eensy weensy ... they will drop the packets on the output port to your server.

It would most likely be line rate right up until the output queue on the port your server is plugged into. Then... drop and request retransmit.

 

[dgrizzard]

It would be like shooting a firehose at a small hole in the wall. Some of the water will make it through, and as it flows through the hose...yes it will be full force.

But ultimately you just end up with a wet floor.

 

[VinceWhirlwind]

I don't really understand why the size of the backplane on the server switch is relevant: the bottleneck is the 1Gb server interface, UNLESS the Server hardware itself can only do, say, 400Mb.

Either way, if each client has a 1Gb connection, they will probably be able to suck up at most 160Mb-400Mb. Even if they have some sort of awesome hardware that can actually do close to 1Gb, the client and Serv switchports will start to congest at around 650Mb/s, so you wouldn't get much more than that through any one of them..