[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 #18 from Gustavo J. A. M. Carneiro <gjcarneiro at gmail.com>  2009-02-01 09:10:18 EDT ---
(In reply to comment #17)
> (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 am unsure.  Last time I posted the code I did not get much reaction, which
probably means it could be a specialized feature.  It is generally useful for
IP-in-IP overlay networks, or "tunnels", but I am guessing not that many people
are interested in tunneling.

So, in principle no, I have no plans to merge it.  But I am receptive to
merging if pushed.

> 
> > 
> > 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.

You make a good point regarding 802.1q.

> 
> 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.  
> 

One of the things that scare me is that this will probably mean we will need
yet another IsLoopback () pure virtual method in the base class, or IsVirtual
(), if we follow the current trend.  The number of IsXxx () methods in the base
class is starting to grow too much IMHO.


-- 
Configure bugmail: http://www.nsnam.org/bugzilla/userprefs.cgi?tab=email
------- You are receiving this mail because: -------
You are on the CC list for the bug.