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Re: Peering point speed publicly available?

  • From: Richard A Steenbergen
  • Date: Thu Jul 01 22:30:29 2004

On Thu, Jul 01, 2004 at 08:01:48PM -0600, Cody Lerum wrote:
> 
> Latency does have a impact on TCP transfers, now granted the difference
> between a oc-3 and oc-192 is negligible, but if you stack a lot of T1
> connections back to back its going to be a factor in your max throughput
> across the path.
> 
> (Stats below might not exactly be accurate...snipped from another site)
> 
> DS3: (1500 bytes * 8 bits/byte) / 44040192 bits/sec = .27 ms (approx)
> DS1: (1500 bytes * 8 bits/byte) / 1572864 bits/sec = 8 ms (approx)
> DS0: (1500 bytes * 8 bits/byte) / 65536 bits/sec = 183 ms (approx)

Lets not put words in anyone's mouth here. Latency does indeed have an
impact on TCP transfers (though it CAN be overcome with decent algorithms
and sufficiently large buffers to keep packets on the wire pending acks).
What I said was that serialization latency has no impact in TCP transfers,
and that the difference between 10Mbps ethernet and OC-192 is only barely
detectable.

(1500 bytes * 8 / 10000000) - (1500 bytes * 8 / 9952000000) = .0012 ms

If you have a DS0, serialization latency is not your limiting factor for
TCP speed. If you have a T-1's worth of data to pass, it doesn't matter if
you're routing it through an unused 10Mbps ethernet or unused OC-192.

-- 
Richard A Steenbergen <[email protected]>       http://www.e-gerbil.net/ras
GPG Key ID: 0xF8B12CBC (7535 7F59 8204 ED1F CC1C 53AF 4C41 5ECA F8B1 2CBC)