[Ns-developers] ns-3.5 planning / mac multicast

[Fabian Mauchle]

Hi all,
hi Mathieu

I recently worked on multicasting in Wifi networks. The current
implementation of MAC multicast in Wifi and Csma networks do basically their
thing, but they do not correctly represent reality.

1. The NetDevice is currently responsible for creating the multicast MAC
address [NetDevice::GetMulticast(Ipv4Address)]. I don't know of any real API
which would do this.

2. Most NetDevices accept all (or most) multicast frames without any
selection or configuration. After I have seen some hints in several RFC's
that a L3 protocol MUST register the multicast addresses (MAC) it wants to
listen to, I searched for an API for this and found one in Linux [see
manpage netdevice (7)]

3. The netdevice API in Linux also allows to enable or disable promiscuous
mode. The NetDevice API in ns-3 only allows the registration of a
promiscuous or non-promiscuous receive callback.

My current plans are as follows:
- I will try to adapt the NetDevice API to the linux API
- Any implementation of the NetDeivce is still free how they treat multicast
frames
- Revert the creation and control over multicast addresses to the
Ipv4L3Protocol*
- I will try to figure out which other components are affected
- I will try to come up with a patch within 2-3 weeks from now.

*The use of multicast in IPv4 is relatively rare. This prepares basically
for IPv6 since it often makes use of multicast.

What are your feelings about this?

Regards

Fabian Mauchle
Institute for Internet Technologies and Applications,
University of Applied Sciences Rapperswil, Switzerland