Subject: [pim] pop-count issue, your input wanted

From: Stig Venaas <[email-masked]>
Date: Wed, 26 Sep 2012 10:40:49 -0700

As part of the IESG review of draft-ietf-pim-pop-count-06.txt,
someone questioned that the Transit and Stub oif-List counts are
only 2 octets.

This means that with pop-count, we currently have a limit on 64k
transit or stub oifs that can be counted for a tree. So if there
are more than 64k hosts, or more than 64k pim routers, we cannot
count them.

Do you have any thoughts on whether we should extend these to 4
octets?

I think the alternatives are more or less these:

1. Not change anything, 65535 means 65535 or more oifs.

2. Introduce an exponential encoding, allowing larger values than
    65535 but with less precision for large counts. Sort of like
    max resp time etc in IGMP/MLD.

3. Extend in the future if needed. One could add a new 16 bit
    option that is only included if the count is bigger than 64k,
    to store additional 16 bits.

4. Simply extend to 32 bits.

The semantics of the 2 could be different. The PIM count is likely
to be smaller than the host count. So stub bigger than transit. But
I suggest keeping them the same.

Thoughts?

Stig