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Re: Strange public traceroutes return private RFC1918 addresses

  • From: Leo Bicknell
  • Date: Tue Feb 03 14:16:02 2004

In a message written on Tue, Feb 03, 2004 at 08:40:22PM +0200, Petri Helenius wrote:
> If you're paying for 40 byte packets anyway, there is no incentive to 
> ever go beyond 1500

With a 20 byte IP header:

A 40 byte packet is 50% data.

A 1500 byte packet is 98.7% data.

A 9000 byte packet is 99.7% data.

Anyone who pays by the bit should like large packets better than
small packets, as you pay for less "overhead" bandwidth.

Note that a 1500 byte IP in IP packet becomes 1520, and then gets
fragmented to 1500 and a 40 byte packet (20 data, 20 header).  That's
only 97.3% efficient, where as a single 1520 byte packet, if it
could be carried, is 98.7% efficient.

Obviously talking in smaller numbers, but to a lot of VPN vendors
1.4% improvement in bandwidth usage, bus usage, or avoiding the
path through the device that fragments a packet in the first place
is a big win.

       Leo Bicknell - [email protected] - CCIE 3440
        PGP keys at
Read TMBG List - [email protected],

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