[c-nsp] bonded T1s into 7206VXR

[Pete Templin]

Adam Greene wrote:

> OK, folks, here's another related question: we're trying to choose between
> these bonded T1's and a 5M fiber connection, for a collocation customer in
> our datacenter. The customer is slightly concerned that the bonded T1's will
> provide less effective bandwidth than the fiber connection, due to the 1.5M
> nature of each individual circuit.
> 
> In my experience, T1's tend to get slow when I try to push >1.35M through
> them. I'm wondering if (3) bonded T1's will actually result in more like 4M
> of effective bandwidth.... From that p.o.v. a single 5M circuit over fiber
> might give slightly better performance.

5M in what format?  Metro E?  Is it rate limited?

Depending on your applications (i.e. VOIP), you might run into packet 
loss if your connection is rate limited, especially if the physical link 
is running at 100M.  Rate limiting typically looks at your traffic every 
0.125 second.  As soon as you exceed your allotment (and any configured 
burst, if accrued) within each 0.125 second window, traffic will be 
dropped.  Hence if your link is running at 100M, sending >625kbps in 
1/8th second could result in packet loss, even if your average rate is 
well below 5Mbps.

Asking (contracting?) your provider to shape outbound (they'll have to 
rate-limit inbound, but you can shape outbound to appease their inbound 
rate limiter) would avoid the rate limiting problem, but could introduce 
jitter if some packets get deferred for 119ms (maximum).

pt