[Bluez-users] Higher throughput with larger UDP packet size

[Bluez-users] Higher throughput with larger UDP packet size

[Sean Loh]

Hi!!

I have established an IP network over the BlueZ stack
and have transmitted UDP packets at varying sizes. I
then  assessed the throughput using the different
datagram packets sizes. Why is it that the larger UDP
packets obtain higher throughputs than the smaller UDP
packets (eg. 60,000 bytes vs 5000 bytes)? Shouldn't
the smaller UDP packets obtain an overall higher
througput since less time is spent for segmentation
and reassembly?

Thanks a million 


		
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Re: [Bluez-users] Higher throughput with larger UDP packet size

[Peter Stephenson]

Sean Loh wrote:
> I have established an IP network over the BlueZ stack
> and have transmitted UDP packets at varying sizes. I
> then  assessed the throughput using the different
> datagram packets sizes. Why is it that the larger UDP
> packets obtain higher throughputs than the smaller UDP
> packets (eg. 60,000 bytes vs 5000 bytes)? Shouldn't
> the smaller UDP packets obtain an overall higher
> througput since less time is spent for segmentation
> and reassembly?

CPU time is not an important factor; the big difference is the time
to send packets over the air.  The shorter packets have extra headers
to encapsulate them at the lower levels, which makes all the difference.

At the Bluetooth baseband level, by the way, 5000 bytes already counts
as "large" and will have to be fragmented into quite a lot of packets
transmitted over the air.  However, I certainly don't recommend using
smaller packets at the UDP level for the reason I've given.

pws


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