Re: [manet-dlep-rg] TCP clients, servers, and discovery (WAS: Re: notes DLEP meeting @ IETF88)

["Taylor, Rick" <[e-mail]>]

Okay, I'm wavering on this one.  I've being thinking hard on this, and my opinion is changing.

First off:

Implementation issues are irrelevant in my opinion.  We are all agreed that writing a TCP server or client is pretty much boiler-plate code.  Modems have full TCP stacks, so do routers (I'm ignoring John's 802.15.4 question).

And now my ramblings:

The correct assignment of Server and Client roles should be driven by semantics of the roles, a server normally handles multiple conversations with many clients: HTTP, SNMP, SMTP, etc, etc...

A server also 'serves' information to interested parties: "I have information, come get it" is a well-used paradigm.

But, using these two suggested modes of operation gives two different answers:

Routers (in general) will handle multiple sessions with modems, and modems (in general) will communicate with a single router.  This implies that the Router should be the Server.

However, Modems 'serve' DLEP information to routers; they have information for the router to come ask them about.  This implies that the Modem should be the TCP server.  The modem can decide how many sessions to accept and serve (generally 1).

An important factor that I believe has not yet been addressed is that DLEP capable routers 'want' to create a DLEP session with a modem so they can perform their function, but a modem doesn't really care if anyone is receiving DLEP info.  This leads me to suggest that a router should find out that there is a modem on an interface (it receives the discovery) and it then demands the DLEP session from the modem (i.e. It connects to the server in the modem).

>From a game-theory perspective (bear with me) the modem gets no benefit by connecting to an advertising router, and therefore may not, but a router does gain benefit and therefore can force the session creation by connecting.  Therefore, the router should be the client.

Aaaargh!  I'm now arguing with myself!

Rick
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