Re: [dtn-interest] Bundling Agents

Matt Bradbury wrote:
> I want to see if my understanding of bundling agents is correct:
>
> Bundling agents control access to the DTN, all bundles enter and leave
> through them.

Yes.

> Does just one bundling agent reside at each "endpoint identifier". Or
> can it be many? Is a bundling agent on the same machine as a DTN
> router, or is it elsewhere.

Going with Keith's concept: every bundle agent is a DTN router, but it would be possible for a DTN router not to be a bundle agent. Each is a set of state machines residing on some computer -- not the computer itself.

This is a little different from the way we use the terms in the documents, where I think "bundle agent" is the more general term and "DTN routers" are a subclass of bundle agents that aren't just sources and sinks of bundles but may also forward bundles sourced elsewhere. We need to resolve this one way or the other, along with a lot of other terminology issues, but for now I don't think there are any contexts in which we get into trouble by using the terms interchangeably.

> Does a bundling agent control many "demux identifiers" or just one? Or
> all?

Each "demux identifier" is analogous to a port number, a token that maps to some sort of device at which an application can use the services of the bundle agent. A bundle agent multiplexes outbound bundle payloads from the devices corresponding to multiple demux identifiers (notionally, multiple application clients) and demultimplexes inbound bundle payloads to them.

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> In my head it still seems that the "bundling agent" is nothing more than
> a glorified API for an application to talk to a DTN router. The
> application asks the "bundle agent" to listen to a few different "demux
> strings". This seems the same as an application in today's world asking
> the IP stack to open a few ports and listen to them.

Yep, same model.

  The only
> difference is that the call to the bundling agents can be done over a
> network connection to a central DTN router.

And that is strictly a matter of implementation. There's nothing in the architecture that requires that an application client make any sort of network connection to the bundle agent at which it is registered, and in fact my implementation doesn't operate this way.

Scott