data center network simulation with ns3, question about Subnetting and csma channel

[avon yan]

Hi, all!

Happy New Year!

 

I am now working on the simulation of dada center network using ns3 now, and I am meeting some problems. Looking for your help!

 

1. I found some codes about fattree architecture, seems that many people choose csma channel to link the host and the edge SW, why? Just as this html

   https://groups.google.com/forum/#!searchin/ns-3-users/fattree/ns-3-users/3eDYy-JElBs/xBLgQyXEV9MJ says, we can choose either csma or p2p…Is there any differences?

2. Must all the node in the same tor, like the edge SW and the hosts connected with it, or, like the SW and hosts in the same BCube0, be in the same subnet?

   If they should be in the same subnet, how to achieve this?

 

Pls help~