[Xorp-users] Using XORP for PIM-SM

[James Courtier-Dutton]

>2008/6/5 Pavlin Radoslavov <pavlin at icsi.berkeley.edu>:
>> Ben Greear <greearb at candelatech.com> wrote:
>>
>> The linux kernel uses a 32-bit number as a bitfield, and at least some of that
>> is visible in the user-space to kernel API as well.
>
> The 32-bit bitfield was probably used in older kernels and/or
> userland programs.
> Now the olist in the kernel for example should be specified in an
> array of size MAXVIFS which can be redefined as appropriate.
>
> Approx. 2 years ago I had an interaction with a fellow who also
> wanted to increase the number of max. vifs in the Linux kernel.
> I believe he was able to achieve few hundred vifs, but I don't know
> whether he needed any more than this or whether he was hitting some
> other limits.
> The notes (and the discoveries re. other system limits) in the
> xorp/ERRATA file on the subject are from that experiment with him.
> In other words, it should be possible, but requires kernel and XORP
> recompilation, and system parameters tweaking. See the IGMP/MLD and
> PIM-SM entries in the xorp/ERRATA file for details.
> If you find some other limits, please us know so we can update the
> documentation.
>

Thank you Ben and Pavlin very much. The ERRATA file seems to agree
with what I found in the kernel, in that the bitfield is not used
anymore and an array of size MAXVIFS combined with other limit
adjustments is used instead.

The number of multicast interfaces limit of 32 was going to be a
problem. It does not seem so much of a problem now.

I will report back if I end up getting XORP to work with my somewhat
different network setup.
As a general backround, the network has a mix of PTP (Point-to-Point)
and P2MP (Point to Multipoint) links, so the PIM-Hello, Join/Prune
etc, will be going down the PTP links, with some of the multicast
traffic being diverted to go down the P2MP links.
PIM-SM RFC4601 only covers PTP and hub/switch based LAN networks link
types. It is a shame we don't have an PIM-SM RFC to cover P2MP link
types.

Kind Regards

James