Re: [v6ops] draft-ietf-6man-grand : saving lookups

Ted Lemon <> Tue, 11 August 2020 20:57 UTC

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From: Ted Lemon <>
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Date: Tue, 11 Aug 2020 16:57:07 -0400
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Subject: Re: [v6ops] draft-ietf-6man-grand : saving lookups
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On Aug 11, 2020, at 4:47 PM, Fred Baker <> wrote:
> On the air interface, they are either transmitting or not. In the receiving NIC, the question is whether or not they store the message; if they are not configured to receive a certain multicast group, regardless of transmission type, they receive and store the message and then forget that they have done so, re-using the buffer for the next message. If they forward the message on, it uses the bandwidth on the other side, whatever it is, with the same destination address. 
> The place where one might distinguish “broadcast” from “multicast” is on a data center switch, where “multicast” might mean keeping a list of relevant ports and only sending to them. They want to send a message once. If they are sending the same message several times, “to whom” is an important question.

Hm. What I do know about WiFi is that actual multicast messages are not acknowledged (because they can’t be) and are therefore sent at lower data rates, so that multicasts occupy much larger time slices per packet. A multicast is notionally only intended for a subset of all connected nodes. If the WiFi base station knows which nodes are interested in a particular multicast address, and that number is small, then it would nearly always be faster to transmit the message to each node as a unicast.

The question is, for a particular WiFi AP, can it know which of its connected WiFi nodes are interested in a particular NS, or do we have to multicast it to every node?

If this is known in the data center, then it must be known on the AP, right?