[pim] Zero-Configuration Assignment of IPv6 Multicast Addresses

["Karstens, Nate" <[e-mail]>]

Greetings,

I am the chair of a standards committee at the National Marine Electronics Association (NMEA). We are in the final stages of developing NMEA OneNet, a standard for Ethernet/IPv6-based communication and control of marine systems (a little background: NMEA has existing standards, NMEA 0183 and NMEA 2000, that provide similar functionality over serial and CAN).

Marine networks can be a mix of low-bandwidth embedded sensors and high-bandwidth streams for radar and video data, and most of this data is sent multicast on the local network. In order to prevent high-bandwidth streams from overwhelming low-bandwidth links, we assign traffic to different multicast addresses and then use multicast snooping to direct those streams only to hosts that request them.

Source-specific multicast is not feasible due to the available switch hardware. As such, we believe we have identified a need for zero-configuration assignment of IPv6 multicast addresses on the local network.

We investigated MADCAP, but this is not ideal because maritime systems try to avoid single points of failure. We also found ZMAAP, which seemed promising, but it was only a draft standard that expired in 2003. Link-scoped multicast addresses also seemed promising, but when you transmit these addresses on Ethernet you get 33:33 followed by 32 bits of the group ID, so even devices that assign their own IPv6 multicast addresses using a unique IID can still collide at the Ethernet layer due to the colliding group IDs.

Another related complication is that multicast streams can originate from different applications on the same host, and there is no mechanism for those applications collaborating to avoid collisions at the IPv6 layer.

Instead of developing our own method, we decided it may be preferable to work with IETF to develop an Internet standard that we could then use in our work. (Or, if there is something that will work for us but we're not aware of, to learn about that). Alvaro recommended that we email this group to start the conversation and see where that leads us.

Thanks,

Nate Karstens
Garmin International, Inc.
Chair, NMEA OneNet TSC

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