Disclaimer
The Author of this posting offers the information contained within this posting without consideration and with the reader's understanding that there's no implied or expressed suitability or fitness for any purpose. Information provided is for informational purposes only and should not be construed as rendering professional advice of any kind. Usage of this posting's information is solely at reader's own risk.
Liability Disclaimer
In no event shall Author be liable for any damages whatsoever (including, without limitation, damages for loss of use, data or profit) arising out of the use or inability to use the posting's information even if Author has been advised of the possibility of such damage.
Posting
Routing performance can be confusing because forwarding rate usually is slower with smaller packets and faster with larger packets. Additionally, forwarding rate slows as "services" (processes that work with the packets besides just forwarding, e.g. ACLs, NAT, firewall, etc.) are added.
Your spec of:
For eg. cisco 3945 as given in the doc. is
Router Model pps Mbps
ISR G2 3945 982,000 502.78
would be for just pure forwarding of minimum size Ethernet packets without any services. Fast switching also assumes these packets don't required any additional examination for forwarding, as they might if the had IP options. If they did, process switching might slow the effective rate by about a factor of 10.
You also need to account for this figure is for all forwarding of packets through the box, so that would be 502 Mbps that could be split between the two directions of a full duplex link. E.g. about 250 Mbps in both directions, or about 100 Mbps in one direction and 400 Mbps in the other, etc.
Your spec of:
circuit-speed WAN performance up to 350 Mbps with services
Is a recommendation that takes into account possible services you might use, duplex traffic, media conversion, VPN, etc. Basically, this recommendation is very conservative and indicates you should be safe up to about that bandwidth doing almost anything on the router. Normally, most configurations can obtain higher performance.
