Emulab FAQ: Using the Testbed: Are there any constraints on my topology?

Yes, but only those imposed by the physical hardware that is currently available in our testbed. The constraints that people most commonly run into are the maximum speed of our links (100Mbps and partial 1Gbps links on PC3000's) and the maximum number of network interface cards (NICs) in our machines. (See the pc3000 page for the mix of interfaces there.)

You can't get any links faster than 100Mbps in general, and sometimes 1Gbps on PC3000's, since we don't yet have many gigabit links for experimenters to use. Our nodes each have 4 experimental network interfaces, so each node can be a member of up to 4 links or LANs. A good strategy for making your topology fit within those limits is to replace multiple links to a node with a LAN or with a router node.

Another approach is to use ''emulated'' network links. Emulated links are multiplexed over the actual physical links, up to the physical bandwidth that the physical link can support. In other words, five 20Mb links can be multiplexed over a 100Mb physical link. More information on emulated links can be found here. Ask Testbed Operations if you need further assistance.