[Ns-developers] [nsc/ns3] status and plans

[Mathieu Lacage]

hi florian,

After trying to use the nsc/ns-3 trees for the attribute stuff, I have
to confess that I am really scared about the whole user experience, and
I think that there are a few things which really need to be addressed
before trying to keep working on the linux 2.6.26 code.

1) nsc must be separately downloaded, built, installed (with a couple of
magic ln commands), and, then, we can build the nsc-ns-3 code. It would
be _really_ helpful if you could make this whole process automatic
within ns-3. Since sam finally moved to a mercurial repo for nsc, you
should be able to use a strategy similar to the one used for the
reference traces and download automatically with mercurial (or a tarball
with wget) the nsc tree when it is needed (the user does not specify
--disable-nsc). Ideally, the ns-3 build system would also be able to
invoke the nsc build system (scons), and, then, install nsc correctly to
make ns-3 find it. Sam mentionned that he considered using waf instead
of scons but got scared by the lack of documentation. I would suggest
that you try to bring gustavo in the loop to figure out if he can help
with that and, if he can't what he can do to help you make ns-3 figure
things out for nsc.

2) Obviously, nsc does not work on 64bit systems: trying to build the
nsc code as 32bit code on a 64bit system has proven to be a serious
challenge. Sam is aware of that issue and plans to fix this by making
the code build natively to 64bit on 64bit systems so, we are on the
right track but, I think that this issue is really important to make it
easier to get started with nsc/ns-3 so, we need to keep track of it and
make sure that we scream at sam if he does not get to do it himself.

3) I see that your focus lately has been to try to bring in more
protocols from newer kernels to work within nsc. This is great but it
would be nice if we could figure out what is really the priority before
merging your code in ns-3. I can see a couple of other (maybe not
equally important) items so, here is a small list which I would like to
discuss (feel free to add more to it):
  a) add netlink sockets
  b) make nsc use the native ipv4/arp stacks and ignore the ns-3
ipv4/arp stacks.
  c) bring in ipv6
It is clear to me that c) is not possible until the other ns-3 ipv6 code
has made progress so, let's ignore it. I am not sure what a) would be
really useful for so, we could ignore it. b) might be potentially much
more interesting but might be too much work within the scope of a gsoc
project.

Neither 1 nor 2 are highly complex technical problems and I understand
that they could be seen as being a bit boring :) Both, are, however,
critical to make it possible to deploy nsc as largely as possible so, it
would be really nice if you could try to spend some time on any of these
issues before proceeding further with more kernel code or, if you really
want to keep working on kernel code, that you set a date after which,
whether the kernel code is done or not, you will work on these build
issues.

regards,
Mathieu