[zeromq-dev] 0MQ protocol stack

[Paul Colomiets]

Hi Martin,

08.04.2011, 08:52, "Martin Sustrik" <sustrik at 250bpm.com>:
> On 04/06/2011 09:45 PM, Paul Colomiets wrote:
>
>>  We can introduce notion of out-of-band messages. This should be a
>>  flag on messages which are for other means look like normal. They can
>>  be used for connection initiation and heartbeating. (May be also
>>  subcriptions, but I don't sure). This way some options sent at
>>  initiation could probably be updated later.
>
> You mean using OOB to send/recv hop-to-hop messages, right?

Right.

>
> The problem is that once the option is available in the API, people
> would start using it for business logic. Those applications would then
> become tied to single-hop topology, with no way to scale.

Just don't let read thease messages by users. Connection init
should just transmit some options set with setsockopt. And
heartbeating probably could also be read by getsockopt (e.g. time of
the last successful heartbeat).

Heartbeating and connection init are inherently hop-to-hop, So
whats wrong with that?

Probably setting some socket option (documented as
internal implementation detail which could change) may enable
receiving OOB messages, if you really need them (it's useful
for monitoring or may be for authorizing connections?).

--
Paul