[Ns-developers] finalizing the ns-3 object model (configuration)

[craigdo@ee.washington.edu]

> >    Parameters params;
> >    params.Set ("PointToPoint::ChannelDataRate", "5000000");
> >    params.Set ("PointToPoint::ChannelDelay", "2");
> > 
> >    Ptr<PointToPointChannel> channel0 =
> >      PointToPointTopology::AddPointToPointLink ( n0, n2, params);

> I see this as one solution that has a few features that the 
> conventional 
> way of doing this (read in a flat configuration file, store global 
> variables) doesn't.
> - it provides a way to plumb in, and scope the applicability of 
> configuration parameters, when the object being configured 
> may be a few 
> layers down in the API.
> - it also would localize the declaration of these values to the class 
> (TypeId) using them, easing the automated documentation of them
> 
> I think though that your comment was directed more at the 
> usability than 
> functionality of the proposal, so do you have some other 
> ideas about how 
> one might achieve the same scoping goals?
> 
> > 
> > I was thinking about this last Friday and it occurred to me that the
> > namespace in our tracing system gets us almost there.  I 
> have methods like
> > the following scribbled on my whiteboard:
> > 
> >   Set ("/nodes/*/tcp/reno/ssthresh", "16000");
> >   Set ("/nodes/1/tcp/rajno/cwnd". "4000");
> 
> This is an interesting idea and looks like Linux proc too.  
> It might be 
> nice to reuse the tracing namespace if possible rather than 
> define a new 
> configuration one.
> 
> It doesn't seem to me to address one of the other issues that 
> Parameter 
> deals with, which was the ability to locally override these settings.

I thought my suggestion directly dealt with ability to locally override the
global settings.  For example, one example locally set the "cwnd" parameter
only in the object referred to by "/nodes/1/tcp/rajno".  I also thought it
directly dealt with "a way to plumb in, and scope the applicability of
configuration parameters, when the object being configured may be a few
layers down in the API," since that's what that same example code did.  

What it didn't do was provide generic parameters to object constructors in
topology code, but I was going to defer that discussion `till tomorrow.

But, yes, my comments are directed more at the usability than the
functionality of the proposal.

-- Craig