Re: [Anima-bootstrap] anima-bootstrap: Bootstrap proxy discovery options

Hi Toerless,

A few remarks to your extensive e_mail

>    Also comparison with mDNS as we discussed it:
>      - code size: We need GRASP for more functions in AN beside 
> discovery,
>        we do not need mDNS for anything in AN, so on IoT devices we 
> would save
>        code size. TBD: Size of an mDNS stack (note: We MAY want 
> "normal" DNS,
>        so the code size for mDNS may not be that large as a delta on 
> top of
>        "normal" DNS).
>      - Number of packet exchanges (TBD: not clear how much this is a 
> real
>        problem, mDNS may optimize here): mDNS exchange is logical three 
> step:
>        PTR RR lookup -> SRV, TXT RR lookup, AAAA lookup
>      - mDNS being a query/reply exchange wouldn't have the security 
> properties
>        i described above. Unless you abuse it and engineer an MDNS 
> unsolicited
>        announce periodically with all the four RRs included. And i 
> guess
>        one could define a TXT RR with the signed timestamp. Aka: I
> could probably
>        do the same thing i was describing above also with mDNS. Not 
> sure if
>        mDNS people would like that...

I checked mDNS-SD (it is not too complex),
It is sufficient to send a query for the SRV RR containing the required 
service.
(Knowing that your service must exist removes the need for checking its 
existence, so no PTR query).
mDNS should also return the AAAA RR defined by the contents of the SRV 
RR in the same message.
The DNS encoding of the messages is pretty concise. (for example, name 
strings occur only once)

> 
> 2. If 1. failed:  OPTIONAL Discovery of bootstrap proxy via L3
> 
Many installations will have their own brand of service discovery (SD).
Inter-operability of SD is the first objective; we can safely assume 
that if a given brand of SD is used,
the whole installation uses this brand as specified by a SDO that is 
active in this particular market.

I think it is sufficient to state that the proxy service needs to be 
discovered
and how this can be done with DNS-SD (mDNS) or DHCP, the IETF standards.

Greetings,

Peter
> 
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