ejabberd can use XEP-0033 to reduce traffic on certain situations. For example, when a user changes it presence.
Service for XEP-0033: Extended Stanza Addressing
New ejabberd router for multicast packets (XEP-0033)
This patch adds multicast capability to ejabberd_c2s: presence stanza broadcasts are sent to the multicast router instead of the main router.
Patch applied to ejabberd Git in the 'master' branch.