Multi User Chat and Extended Stanza Addressing

A Multi-User Chat service sends a lot of similar messages to a lot of JIDs, so it would seem this service can bastly benefit if using Extended Stanza Addressing.

We can group the possible targets in:

• Sending message broadcasts (section 7.9 of XEP-45)
  
• Sending system advisories: change on subject, change on room configuration, system messages (sections 8.1, 10.9)
  
• Sending presence broadcasts: join, leave, nick change, granting/removing privileges... (sections 7.1.3, 7.2, 7.3, 7.4, 8.2, 8.3, 8.4, 8.5, 9.1, 9.2, 9.3...)
  

Upgrading a MUC service to send message broadcasts and system message broadcasts using a multicast service (XEP-33) is easy, since the exact same message stanza is sent to all the room occupants.

However, presence broadcasts are slightly different depending on the room configuration and the destination role and affiliation: on some cases the presence stanza includes additional attributes (jid). So, upgrading a MUC service to send presence broadcasts using a multicast service is slightly more complicated.