Re: [Anima-bootstrap] mDNS or GRASP? [was: peer and domain [was BRSKI State Machine]]

Brian E Carpenter <> Wed, 19 October 2016 20:00 UTC

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To: "Michael Behringer (mbehring)" <>, "Max Pritikin (pritikin)" <>
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From: Brian E Carpenter <>
Organization: University of Auckland
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Date: Thu, 20 Oct 2016 09:00:19 +1300
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Subject: Re: [Anima-bootstrap] mDNS or GRASP? [was: peer and domain [was BRSKI State Machine]]
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On 19/10/2016 20:35, Michael Behringer (mbehring) wrote:
>> -----Original Message-----
>> From: Brian E Carpenter []
>> Sent: 18 October 2016 21:46

>>> "peer" is an entry in the adjacency table. Yes, there may be several on an
>> interface, of several different domains. The adjacency table discussion tries
>> to capture that.
>> Fair enough. But anyway my comment still applies: a node that is joining the
>> ACP, or simply updating its ACP adjacencies, will discover all available
>> neighbors...
> True. But why is that a problem, or what are you suggesting because of this? 
> (I think I got lost in the arguments here)

No, no problem, I was just trying to be clear about what you meant.

> We need a discovery protocol. 
> We should use the same discovery protocol for BRSKI and ACP (and other actions later on, see my message a few mins ago)
> GRASP *could* be that protocol, in the way you describe. 
> But my understanding was that we had settled on using mDNS for this discovery. 
> In the bootstrap calls, this was "decided", see
> Notes from 2016-10-04, bullet 3 (currently, lines 175-178):  
> <include from etherpad>
> 3. does not specify a GRASP mechanism for proxy discovery, should it?
> max feels, "no" because defining an insecure mode of GRASP is difficult.

Which was tru in Berlin but is now wrong; the insecure instances are defined in GRASP -07.

> mcr feels, "no" because discovery by multicast UDP but replys are by TCP which means the new node needs to open a TCP port to get a reply back. We just had a long conversation about TCP/UDP etc (re flipping the handshake) and this adds more confusion.

Which is resolved in the GRASP -08 candidate text after that conversation, and in running code.
(And also, in the "flood" model for proxy discovery, TCP doesn't even arise, so this
argument is doubly wrong.)

> group conclusion: close this. "No". (agreement on the call is noted; with toerless voting for grasp but accepting the group decision)
> </include> 

I don't get up in the middle of the night for those calls, and I don't accept that decision.

We should not *require* mDNS in Anima. I can see that it will be needed in some non-Anima
deployments of BRSKI. I thought we had actually resolved that in Berlin. Proxies can be
discovered with mDNS or GRASP. I've posted demo code for link-local discovery of proxies
by pledges using two different GRASP models - flooding or discovery/synchronization.
I'd like comments on those models. As noted above, the flooding model is UDP only.