Re: [mdnsext] mdnsext & SLP

David Farmer <farmer@umn.edu> Fri, 21 June 2013 17:12 UTC

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Date: Fri, 21 Jun 2013 12:12:52 -0500
From: David Farmer <farmer@umn.edu>
Organization: University of Minnesota
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To: Michael Sweet <msweet@apple.com>
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Cc: IETF mdnsext <mdnsext@ietf.org>, Garret Peirce <peirce@maine.edu>, David Farmer <farmer@umn.edu>
Subject: Re: [mdnsext] mdnsext & SLP
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On 6/21/13 11:43 , Michael Sweet wrote:
> Garret,
>
> On Jun 21, 2013, at 12:15 PM, Garret Peirce <peirce@maine.edu
> <mailto:peirce@maine.edu>> wrote:
>> Michael,
>>
>> I had thought the purpose of an SLP DA was to enable SD across subnet
>> boundaries.
>> The idea being there could be a number of them setup for different
>> reasons (ex. organizational/serviced scoped).
>> ref: RFC2608 section 12.
>
> *If* the DA spans the subnets, a single DA could service all of them and
> still be auto-detected by the UA's.  But that really only works for
> simple topologies where you have a common gateway or router joining the
> subnets.
>
> If you use DHCP to set the DA for the UA's on each subnet, then you have
> to configure each of the DHCP servers to do that...  And you still have
> the issue of resolving hostnames and/or routing addresses for the
> services - for example, a printer might advertise its printer service
> with any of the following:
>
>      service:printer:ipp://192.168.0.100/ipp/print
>      service:printer:ipp://10.0.1.100/ipp/print
>      service:printer:ipp://[fe80::0100]/ipp/print
>      service:printer:ipp://hostname.local./ipp/print
>      service:printer:ipp://17.1.2.100/ipp/print
>      service:printer:ipp://hostname.apple.com/ipp/print
> <http://hostname.apple.com/ipp/print>

I have experience running SLP in a large scale Campus/Enterprise 
environment, many of the things you say are a disadvantage are actually 
an advantage in such environments.

I'm not sure compatibility or interpenetration with SLP is a good idea 
or not, but something similar to the DA architecture and the ability to 
tell unicast isolated client where the DA is with a DHCP option are 
concepts I think should be considered for the dnssdext solution space.

Thanks.

-- 
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David Farmer               Email: farmer@umn.edu
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University of Minnesota
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