[e2e] Network level qos support for web services

[David P. Reed]

Syed Hasan wrote:

>So does we need to tune diffserv for web services? If not then what is the
>solution for a company which wants better service for its critical web
>services?
>  
>
Faisal - since actual "service quality" has very little to do with what 
the protocol community calls "QoS", it is my opinion that web services 
should look elsewhere than diffserv to obtain their service quality.

QoS at the router level is a great "marketing" word, but frankly, stuff 
like ECN and traffic engineering are much bigger levers on the user 
experience.

But to him who has only routers and algorithms to sell, every problem 
looks like a job for "diffserv".

In other words, there is an end-to-end argument that suggests you start 
by looking at what the dominant factors in ensuring web services quality 
might be, rather than assuming it has something to do with the router 
layer.   I personally think that tools for traffic engineering have a 
much bigger payoff - if network administrators and equipment managers 
can move the load around so buffers in routers never exceed an average 
of <1 packet for each outbound interface, you maximize the benefit you 
can achieve, leaving little for QoS mechanisms to do.

If you must focus on critical vs. non-critical traffic, use 1 bit of 
high vs. low priority (which can be inserted at packet entry based on 
simple rules like iptables rules).

The 80-20 rule suggests that any further efforts will have marginal 
returns at major costs, probably better spent on investing in fibers and 
switches to remove bottlenecks discovered by traffic engineering tools.

Of course the router software suppliers don't want people to think this 
way, and the theory community needs optimization problems to publish 
about....
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