How much of this network service is a rule engine
function and how much is a "set up" service that
is provided by a proxylet?
At 08:41 AM 8/28/2001, Markus Hofmann wrote:
Ng Chan Wah wrote:
> It is to my understanding that the work group is moving towards using
> adaptation service (either local or remote) to handle content adaptation
> decisions base on network traffic conidtions. The rationale being the rule
> engine should be kept as efficient as possible.
Well, the view is more that the rule engine itself should not do
network monitoring or performance measurements. However, the rule
engine can make use of system variables that hold the actual results
of such measurements (we just extended this in the lates IRML draft).
For example, there might be a rule that says "if 'network_load'
matches 'high' then do 'adaptation_for_high_load'". The
system-variable 'network_load' can be set by another (local) service
module or my an independent piece of software running on the OPES
intermediary (or whatever we end up calling this box).
> For example, when content adaption is needed for an A/V stream, a rule
> simply states that all ccontents belonging to the A/V stream be
forwarded to
> the adaptation service. It is the adaptation service that will decide what
> kind of adaptation is required.
Or you've rules that forward the content to certain adaptation
services based on the value of certain system variables.
> This leads back to the problem I face which leads me to OPES in the first
> place. How does the adaptation service obtain network condition
> informations? There are couple of ways that are either non-standard, or
need
> to go lower than the session layer in the protcols stack.
Defining mechanisms for obtaining network conditions seems to be
out-of-scope for OPES. OPES will define the framework that allows you
to plug-in service modules that can do such measurements, but it does
not tell those modules HOW to do it (that's a "local" implementation
decision). OPES might also provide means to consider conditions
obtained through network measurements in rule matching - for example
through system variables. A missing piece now remains a "protocol"
that let's you set system/service variables on OPES intermediaries -
something for OPES to look at?
-Markus
Michael W. Condry
Director, Network Edge Technology