From KAREN wiki

Contents 1 Multicasting 2 The Basics 3 Multicasting Testing 3.1 Testing Environment

Multicasting

The Technical Centre section of the KAREN website contains information regarding Multicasting.

The KAREN multicast standards are derived from our upstream R&E partners internationally. This enables KAREN members to be a sender or receiver of multicast content with appropriately configured R&E sites around the world.

The current standards for multicast support over KAREN are that PIM Sparse Mode and MBGP must be supported. Anyone wanting to be an aggregator or that wants to offer multicast content will also require MSDP support. While different platforms may be able to offer various levels of multicast support based on a subset of these features REANNZ recommends that any KAREN connected devices support the standards that have been adopted by the international community.

There is also a fantastic resource available here: [IPv4 Multicast on JANET, Technical Guide]

The Basics

Receiving Multicast Traffic A host must inform the routers on it's LAN of it's interest in receiving traffic from a multicast group. Hosts and Routers use Internet Group Membership Protocol [(IGMP)] achieve this.

Transmitting Multicast Traffic A multicast source is a host that sends data to a mulitcast address (aka multicast group). This is entirely independant of IGMP, and will flood the LAN of the multicast source host.

Protocol Independant Multicast - Sparse Mode [(PIM-SM)] is the protocol used by KAREN, and is the most widely deployed of multicasting protocols. PIM-SM has 3 stages for delivering multicast from a source to a reciever:

1. The building of a shared tree, aka the Rendezvous Point Tree, that will deliver packets between the Rendezvous Point (RP) router and the interested listeners for the multicast group.
2. The building of a Shortest Path Tree (SPT) that will delvier packets between the source and the RP.
3. The building of a set of STPs that will, for efficiency, deliver packets directly between source and listener

Multicasting Testing

We have performed a series of labs to "take a look under the hood" of the mysteries of Multicasting, details and updates follow below...

Testing Environment