Re: [core] RFC 7252 - 8.2 - Multicast - Request / Response Layer, page 67, top

Achim Kraus <achimkraus@gmx.net> Wed, 01 April 2020 20:28 UTC

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From: Achim Kraus <achimkraus@gmx.net>
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Date: Wed, 1 Apr 2020 22:28:01 +0200
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Subject: Re: [core] RFC 7252 - 8.2 - Multicast - Request / Response Layer, page 67, top
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Hi,

>> +---------------+                +-----------------+
>> |               |    request    _|_                |
>> |               |        .---> /   \   224.0.1.187 |
>> |              _|_      /      \___/ --.   :9999   |
>> | 192.168.0.1 /   \ ---´         |      \          |
>> |   :54321    \___/ <---.       _|_     /  rewrite |
>> |               |        \     /   \ <-´           |
>> |               |         `--- \___/ 192.168.0.100 |
>> |               |    response    |         :5683   |
>> +---------------+                +-----------------+
>>        Client                           Server

Nice diagram.

> Not sure why you would also want to rewrite the transport endpoint?

I tried to follow the discussion.
The idea to change the port as well enables java (and I guess some more)
to differentiate between multicast and unicast requests. Jim also
mentioned, that it enables the use of multiple servers on the same host.
I have not enough experience with multicast in different environments to
see, if that may cause more trouble (e.g. firewall etc.). I would guess,
that some  implementations will just offer that variant, at least as
configurable option (I would try do so for Californium).
So my favorite for now is just implement it and see, what the user's
feedback will be.

If that idea gets declined (may be by negative feedback of users), I
still think, that there is a demand for other means to distinguish
between multicast and unicast requests. Maybe, either the usage of the
uri-host option or a new option will help.

This maybe considered as "too pragmatically", but on the other side I
also don't see the "great benefit" in insist not to change the port.

best regards
Achim