[rrg] Why a host-based solution does not necessarily add signalling load

[Scott Brim]

Excerpts from Paul Jakma on Thu, Jan 22, 2009 01:12:40PM +0000:
> On Wed, 21 Jan 2009, David Conrad wrote:
>
>> Paul,
>>
>>> I assumed there was an implied ", to a significant enough extent for 
>>> it to matter" at the end of the sentence I quoted.
>>
>> What meets your requirement of enough "to matter"?  Depending on  
>> deployment scenario, a tunnel-router-based solution could cover  
>> thousands of hosts or more.  Is that enough to matter?
>
> It's going to be subjective to a point, but determining "to matter"  
> would involve comparing the control-overhead to the actual data-bearing 
> traffic, rather than focusing solely on the difference in control traffic 
> between end-host and intermediary based solutions.
>
> Having a tunnel-router do the liveliness tests for 1000 hosts might save 
> 999 instances of control traffic, but if the 999 instances of control 
> traffic comprise 1-2% of the data traffic - then should we care? (Is 
> there a data-communications version of Amdahl's Law I can quote here?).
>
> By my back-of-the-envelope calculations, a Shim6/REAP solution has  
> Order(1.2%) overhead relative to data-traffic (on a low amount of  
> traffic, 24kB - e.g. fetching the google front-page) for the normal  
> case. Failure cases presumably might take slightly more - but failure is 
> not the common case. Solid quantitative studies would be really useful.

Could you show us your BOTEC?  I've been meaning to go gather some
real numbers.

Scott