[Ns-bugs] [Bug 188] global routing does not handle ip aliasing

[code@nsnam.ece.gatech.edu]

http://www.nsnam.org/bugzilla/show_bug.cgi?id=188





--- Comment #17 from Tom Henderson <tomh at tomh.org>  2009-01-31 22:05:58 EDT ---
(In reply to comment #16)
> (In reply to comment #15)
> > I've been looking at this bug again in the context of the ns-3-ip work. 
> > AFAICS, there is no support in the real world for routing protocols to deal
> > with IPv4 aliasing on a single net device.  Instead, how this seems to be
> > universally handled is the creation of virtual devices on top of a physical
> > device.  These are often called subinterfaces in routers.
> [...]
> 
> If you go for this, can you think of another name than "virtual devices"? 
> That's to avoid confusion with
> http://code.nsnam.org/gjc/ns-3-virtual-netdevice/
> Maybe "alias devices"?  Especially since I was planning to write a paper in the
> next few weeks including this VirtualNetDevice (among other things, like
> UMTS/Wifi integration work that my colleague is working on).

I had forgotten about your tap-like VirtualNetDevice when I posted the above;
sorry.  Do you have future merge plans for it?

> 
> I still get the feeling think these fake devices will be a source of confusion
> for people doing work on L2 stuff (like me).  We'll have to take extra care to
> check whether a device is real or fake before using it...  If you do it, I
> recommend to at least try to put it on a different layer, so that only layer >=
> 3 is affected and they do not appear in the list of Node devices
> (Node::GetDevice).
> 

It seems to me that these should not be in layer-3 but should appear to layer-3
like a real device.  For instance, it seems to me that loopback should be a
L2-virtual device rather than the way it is an IPv4 only device now.  I think
that people doing L2 work on 802.1q will probably want support for these types
of devices.

But I agree with you that there are issues lurking with these types of devices
that need to be resolved so that they do not become confusing.  


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