Re: 6MAN Adoption call on raft-chakrabarti-nordmark-6man-efficient-nd-04

[Lorenzo Colitti <[e-mail]>]

On Thu, Jan 9, 2014 at 9:44 PM, Mikael Abrahamsson <[e-mail]> wrote:

>
>> They would be rate-limited, just like any other ND packets on any
>> implementation worth its salt. I think an NS is 72 bytes including ICMPv6
>> header; if so, then even if you send out 500 of them per second, that's 36
>> kB/s. What sort of link has a problem carrying 36 kB/s? How many NSes per
>> second can routers send out anyway?
>>
>
> I don't know, people seem to indicate that there is a problem with
> multicast pps on wifi links. I haven't seen any hard data on this, it was
> just my interpretation that this was considered a problem.


Knowing nothing about this, I will cite
http://stackoverflow.com/a/4341485, hoping that the draft authors will
come along with more detailed data
(which hopefully they have already presented to justify their use case and
which I missed):

===
With unicast the access point tracks what data rate every particular
receiver can reliably receive at, and sends about that rate. With multicast
the access point does not know which receivers are interested in the data,
so simple access points send the data at the slowest possible rate (1Mb/s).
Better implemented access points may send the data at the rate that the
slowest connected client is using, and the best access points use IGMP
snooping to see who's receiving each IP multicast stream, and they will
choose the slowest rate out of the receivers for that stream.
===

Even 1Mbps is still a fair number of ND packets though.