How can I calculate require size for Layer 2 Link between sites

[Jonnyballgame34]

Greetings,

I've got two sites, (one existing, one new), that are about 10 miles apart will be connected via fiber ring for about 6 months. We're preparing to ordering the ring but I'm unsure how to select bandwidth.  Can anyone recommend tools/reading/standards etc. for predicting the traffic/sizing the circuit? 

This is part of a move/migration, so the one piece I do know is that the total layer 2 traffic between sites will be less than the the L2 traffic on the current network any advice would be appreciated. Thank you

[Joseph W. Doherty]

For a MAN, you might try some typical LAN over-subscription ratios, say from 4:1 to 48:1.

If you can, if the MAN connection supports various CIRs, you can try the minimal CIR that the physical link offers, and bump it up if performance is inadequate.

On the issue of performance, understand even 10 miles apart will add latency that you don't see now, so even if you have infinite MAN bandwidth, the distance will slow your network access.

If your MAN bandwidth is under 100 Mbps, and even if not, you might find QoS might be critical to make up for less than LAN bandwidth.

Even if you have a MAN link with LAN bandwidth, and even with ideal QoS, again, the distance latency may make the network appear to perform slower.  So, understand increasing bandwidth will not correct a distance latency issue.  There are WAN accelerator appliances that help mitigate distance latency.  I mention this because sometimes WAN acceleration is better than just more MAN/WAN bandwidth.