[SPAM] Re: SCP speed question

[David Bandel]

On 1/9/07, Rick Bowers <rwbowers at gmail.com> wrote:
> At 1/6/2007 12:08 AM, you wrote:
>
>
> >Are you sure you're not seeing between 4 and 11MB/s?  Most measurements of
> >transfer speed are done in BYTES not bits, as the network gear is rated.
> >Approx divide by 10, particularly over wan links (analog: 8 bits data, 1
> >start, 1 stop).  Or if you want to think perfect world switching, /8 is more
> >your cup o' tea.
>
> Perhaps I'm wrong, but I thought start/stop bits applied only to
> synch/asynch communications. TCP/IP has no start/stop bits as far as
> I know. So, don't we (mostly) all divide by 8 these days?
>

While the terminology (start/stop bits) might not have been correct,
there is overhead.  The amount of overhead (specifically, the IP and
TCP headers) take up a percentage that is not constant.  That
percentage may be low (assuming the MTU is high, around 1500) or it
may be significant (if the MTU is low, like 296).

You can divide by 8 on a fast circuit w/ high MTU and PMTU discovery
and you'll be very close.  But on a dial-up, you'll be off
considerably.

Ciao,

David A. Bandel
-- 
Focus on the dream, not the competition.
            - Nemesis Air Racing Team motto