Is there an application-agnostic signaling protocol?

Question

Is there an application-agnostic signaling protocol?

The use case is this. We have an open-source library for a multi-agent system that supports several protocols of the application layer of the OSI model. On the moment HTTP, XMPP, and ZeroMQ are supported for example. We would like to add high-bandwidth real-time streaming possibilities. It is logical to use RTP for that.

So, to recapitulate, we already have a connection to the other party that we can use for signalling. We want to negotiate only a new channel for data communication.

However, regarding the current standards, with respect to signaling all of them seem to be tied to their application. These current "standards" seem to be SIP, RTSP, and Jingle. They all seem to use RTP or SRTP on the application layer, and UDP on the transport layer. See e.g. XEP-0167.

The only thing we want to negotiate is another connection to that party that can be used for data transmission. In the Session Description Protocol all kind of stuff about media shows up, optional phone numbers, etc. If someone can point at a signaling protocol that is meant to be application-agnostic, that would be great!

Answer 1

If you just need a signalling protocol that is system and application agnostic, XMPP is the way to go.

Answer 2

I'm a big fan of XMPP and I think you'll get what you need with it. However since you already have HTTP as well, I want to mention that PubSubHubbub can also be used for that! The current version of the protocol applies to any mime type that can be transported with HTTP so that would work.

In practice it's just a webhooks API which makes it easy to use and scale via load balancing.

Answer 3

Is there an application-agnostic signaling protocol?

Yes there are lots and you already mention a number of them such as XMPP, SIP and RTSP. You could also add the brand new WebRTC protocol to the list.

We would like to add high-bandwidth real-time streaming possibilities. It is logical to use RTP for that.

Yes. RTP is lightweight and as its name suggest was designed for carrying real-time traffic. It's also popular so you will be able to find numerous existing implementations.

The only thing we want to negotiate is another connection to that party that can be used for data transmission. In the Session Description Protocol all kind of stuff about media shows up, optional phone numbers, etc. If someone can point at a signaling protocol that is meant to be application-agnostic, that would be great!

I'm not sure what you mean here. Session Description Protocol (SDP) is a standard way to describe the media capabilities of a device. It's commonly used in SIP and RTSP (and XMPP has something equivalent) however it's separate from those protocols and if you don't want to use it you are free to come up with your own way of describing media.

You may be getting overwhelmed by some of the SDP examples, and they can indeed get very complicated when there are multiple streams and codecs offered. However an SDP payload can also be very simple; below is an SDP example for an RTSP server offering a single MJPEG video stream.

v=0
o=- - 0 IN IP4 0.0.0.0
s=-
t=0 0
m=video 0 RTP/AVP 26