As mentioned in the weekly report #59, experiments have the limitations on the number of links that cross switches and sites. It is due to the way the 'assign' script in the emulab software works. The 'assign' script allocates 100 Mbps per link even though the ns file specifies the link speed as less than 100 Mbps (e.g., 1 Mbps). This means, the number of VLAN's that cross two switches like, Cisco and Nortel at ISI would be limited to 10 even when each link has 1 Mbps as the speed.
To increase the number of VLAN's across the switch boundaries and the two campuses, we set the inter-switch trunk speeds in the testbed database as 4 Gbps, instead of the current real 1 Gbps, so that total of 40, instead of 10 VLAN's can be assigned. The ISI-UCB tunnel speed is set to 1 Gbps, instead of the real 150 Mbps. Doing this would potentially over-subscribe the trunk or the tunnel.
http://www.isi.deterlab.net/doc/Inter-Switch-Bandwidth-Limit.pdf
In the diagram on the above URL, the numbers next to the arrows stand for the actual bandwidth of the links, and the numbers next to them in parentheses are the number of VLAN's that can be assigned over the links. Please keep in mind that these links are shared by all the experiments running on the testbed.
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