[ofa-general] Re: ARP in IPoIB

[Amar Mudrankit]

Michael,
thanks for your reply. But, this gives rise to couple of questions..

1] If such multicast routing protocol for IB routers is not yet specifid by
IBTA or IETF, then current implementation have IP subnet restricted within a
IB subnet. According to RFC 4391, section 9.1.1, the link layer address is
formed through combination of GID + QPN. If we are not spanning across IB
subnets what is the use of GID as we need to get LID from GID? Probably, in
that case ARP reply with LID,Q_Key and other path information would be
helpful which resolves path in 1 loop than 2 loops in case of GID(first to
resolve GID and then to get LID).

2] When we look at code the dev->dev_addr is still made up of GID+QPN. What
could be the purpose of having implementation this way if we can have
dev->dev_addr made up of LID,Q_KEY etc with reference to point no 1 above?

On 7/26/07, Michael S. Tsirkin <mst at dev.mellanox.co.il> wrote:
>
> > Quoting Amar Mudrankit <amar.mudrankit at gmail.com>:
> > Subject: ARP in IPoIB
> >
> > Hello all,
> >
> >     Being new to this group, following questions may sound a bit basic
> level
> > but I would be really very happy if somebody could help me out in those.
> >
> > 1] Does current implementation of IPoIB supports IP hosts spanning
> different IB
> > subnets? If so, how does it resolves the IP addresses(QPN+GID etc)
> because how
> > would the broadcast IP ( multicast IB) request would reach different IB
> subnet
> > as the router should have multicast routing capabilities? Does it mean
> that the
> > current IPoIB implementation is supported for hosts within single IB
> subnet and
> > not beyond that?
> >
> > 2] What is all-router multicast group(RFC-4391 section 10)? How does it
> help in
> > routing packet to a IP host present on different IB-subnet?
>
> Pls refer to this document: RFC 4393, IP over InfiniBand (IPoIB)
> Architecture
> Chapter 3.3. IP Subnets Across IB Subnets which has some answers to your
> questions.
>
> Here's a link:
> http://tools.ietf.org/html/rfc4392
>
> --
> MST
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.openfabrics.org/pipermail/general/attachments/20070726/c90ef7d8/attachment.html>