[zeromq-dev] IPv6 multicast RADIO/DISH

Brian Adamson brian.adamson at nrl.navy.mil
Thu Apr 26 14:49:17 CEST 2018


Hi Lionel,

Although it isn’t yet supported with the ZMQ API’s, the NORM protocol can be configured with receiver feedback disabled to provide an unreliable UDP-like best effort service with the added benefit of its message fragmentation and reassembly when messages are larger than the network MTU.  Additionally the FEC-based packet erasure coding can also be invoked if desired to provide a quasi-reliable “better than best effort” service where a number of FEC parity packets per coding block (where a “block” is a block of packets) can be set that are sent in addition to the user data packets.  It would be interesting to explore adding some additional options for the NORM binding.  I haven’t had time to spend on that but would be happy to help someone who wanted to take a shot at it.

best regards,

Brian 

> On Apr 26, 2018, at 4:55 AM, Lionel Flandrin <lionel at svkt.org> wrote:
> 
> On Thu, Apr 26, 2018 at 09:23:13AM +0100, Luca Boccassi wrote:
>> On Thu, 2018-04-26 at 10:00 +0200, Lionel Flandrin wrote:
>>> Hello everyone,
>>> 
>>> I'm trying to build a multicast protocol on top of an IPv6-only
>>> network. I found that the draft RADIO/DISH sockets seem to do exactly
>>> what I want, however the zmq_udp man page doesn't explicitely mention
>>> supporting IPv6 multicast and I couldn't get pyzmq to bind an IPv6
>>> multicast DISH with any URL format I've tried.
>>> 
>>> Is IPv6 multicast simply currently unsupported for UDP sockets? If
>>> that's the case is it because of a technical difficulty or simply
>>> because nobody bothered to implement it?
>>> 
>>> Thank you for your help (and your great library),
>> 
>> UDP right now supports only ipv4 - it's a work in progress:
>> https://github.com/zeromq/libzmq/issues/2891
> 
> Ah, I see, thank you for confirming that. Do you think adding IPv6
> support would be a huge amount of work for somebody not familiar with
> ZMQ's codebase? Is it just about adding a few branches changing
> AF_INET to AF_INET6 or am I being ridiculously naive?
> 
> My current backup solution if I can't get ZMQ to do what I want is to
> write my own IPv6 multicast code using BSD sockets directly, if
> hacking ZMQ's code to add support is not too daunting I could consider
> doing that instead.
> 
>> PUB/SUB with PGM or NORM should do what you are looking for.
> 
> I considered EPGM briefly but the zmq_pgm man page seems to say that
> only IPv4 is supported, so I didn't even attempt it:
> 
>  A multicast address is specified by an IPv4 multicast address in its
>  numeric representation.
> 
> Maybe I shoudln't have been so quick to dismiss it, I'm going to give
> it a try. That being said I don't actually need the guarantees of
> PGM/NORM, in particular I don't care if a frame gets mangled or
> dropped and I don't need SNDMORE.
> 
> Thank you,
> -- 
> Lionel Flandrin
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