Re: [homenet] Updates to Homenet Architecture Principles doc

[Ray Hunter <[e-mail]>]

Juliusz Chroboczek wrote:
>>>> "The inclusion of physical layer characteristics including bandwidth,
>>>> loss, and latency in path computation should be considered for
>>>> optimising communication in the homenet."
>
>> Should the text then rather say "Path selection in Homenet needs to be
>> more sophisticated than measuring pure hop count due to the use of
>> heterogeneous link technologies, and therefore the routing protocol should
>> be capable of utilising multiple link-dependent metrics, such as
>> bandwidth, delay, and link reliability", rather than mentioning
>> "optimised"?
>
> I'm happy with either.  The current text leaves it to the protocol people
> to decide what "optimising" means, but I also like the way you spell out
> the requirement.  If you'll allow me to indulge in some minor nit picking
> wrt. your suggested wording:
>
>   - you require "multiple [...] metrics", which is what we do in Babel, but
>     we certainly don't wish to prevent somebody from being smart enough to
>     design a single metric that works satisfactorily on all link layers;
>   - you use "bandwdith" where you mean "throughput" (yeah, I know, I'm
>     a pedant);
>   - I'm on a personal crusade against the utilisation of the verb "to utilise".
>
> So perhaps something like:
>
>    Due to the use of heterogeneous link technologies, path selection in
>    a homenet needs to be more refined than minimising hop count.  The
>    homenet routing protocol should be able to select paths according to
>    criteria such as latency, throughput, link reliability (e.g. measured
>    packet loss) or other performance metrics.
>
> -- Juliusz
>
>
I could certainly live with your text, and if the WG ever moved to 
evaluating competing candidate routing protocols against requirements 
derived from the architecture, it could provide a useful and objective 
differentiator, which is possibly something that has been lacking up 
until now. e.g. {BABEL,  EIGRP, full IS-IS .....} might be preferred 
over {OSPFv3....} which might be preferred over {RIPng, HNCP native 
routing, IS-IS (only using cost and default cost=10) , AODV (without 
link quality extensions) ....} on this particular measure of suitability.

-- 
Regards,
RayH