Why docker port binding is for both tcp and udp?

[Michał Wieczorek]

In job specification for docker we define ports, but without saying if it's tcp or udp.

Nomad will add both binding.

Is it intentional (if so: why?), or it's done this way to make the job spec simple?

Do you consider adding option to define 'only tcp' or 'only udp'?

[Diptanu Choudhury]

Yes, this was done to make the job spec simpler. Do you have any use case where you want to enable only one?

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Thanks,
Diptanu Choudhury

Web - www.linkedin.com/in/diptanu

Twitter - @diptanu

[Michał Wieczorek]

It's just my curiosity :-) not a real use case.

I'm just trying to run nomad/docker on windows server 2016, and there's a bug in windows when we want to bind both tcp/udp for the same port - https://github.com/Microsoft/Virtualization-Documentation/issues/319

So a dirty workaround for me is to comment out line with tcp or udp bind.

When there will be a fix in windows (next TP or RTM) - problem will be gone.

But do you consider to change it (adding option to define 'only tcp' or 'only udp') or prefer to leave it like that?

[Nathan Fisher]

Would making the default tcp and then slightly more configuration for udp make sense? I feel like tcp will be the sane default for most users/
services (http and RPC). Where udp is more likely to be used for core components such as telemetry, logs, and dns. The latter being important but far fewer services.

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[Alex Dadgar]

From a scheduler perspective it is easier to assume that the port is bound for both UDP and TCP. It requires less state and less look ups meaning that the servers use less memory/disk and make faster placement decisions.

- Alex Dadgar

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[Nathan Fisher]

Makes sense. Was thinking solely from the user point of view. I can see how it would be an explosion having to maintain state for both tcp and udp allocations.

[Michał Wieczorek]

Makes sense for me too. 

Thanks.