What Rogers call 'service' [was: Micro Routers (Was: : Raspberry PI (as router))]

[James Knott]

Lennart Sorensen wrote:
> On Thu, Jun 14, 2012 at 03:18:08PM -0400, Bob Jonkman wrote:
>> >  I wonder if there's some level of compression being applied to lower
>> >  levels of the stack, so that the application can actually report a
>> >  higher throughput than the pipe is capable of delivering directly...
> Well there is PPP involved which could be doing compression, although I
> am usually transfering stuff that isn't going to get any more compressed.
>
> 25Mbit=25000000bits=3125000bytes so even with a bit of overhead, using
> 1500 byte packets (or close to it) for http transfers, there really
> doesn't seem to be any reason it shouldn't be close to 3000KB/s.
>
> I believe PPP adds 8 bytes to a packet.  Ethernet header would be another
> 14 bytes, so a 1500 byte packet going over the VDSL2 PPPoE link should
> be 1522 bytes.  If I scale by 1500/1522, I get 3079KB/s rather than
> 4125KB/s, so not much overhead there.
>
> I just ran a dist-upgrade and hit 2856 kB/s download speed, although
> the connection wasn't completely idle at the time.

On ADSL, the MTU is 1492, not 1500 bytes, with the PPP header occupying 
the remaining 8.  Also, ADSL is very dependent on distance from the 
DSLAM and also cable quality.  Of course, there may be other issues at 
the server or along the route to it.

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