Re: [mdnsext] Discussion of BoF during Berlin IETF

Michael Sweet <> Mon, 03 June 2013 13:40 UTC

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From: Michael Sweet <>
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Date: Mon, 03 Jun 2013 09:40:28 -0400
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To: Kerry Lynn <>
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Subject: Re: [mdnsext] Discussion of BoF during Berlin IETF
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On 2013-06-03, at 8:42 AM, Kerry Lynn <> wrote:
> On Mon, Jun 3, 2013 at 4:20 AM, peter van der Stok <> wrote:
> Hi John,
> Very few, naive wishes about autonomous SD data access.
> IMO, "autonomous" is a worthy goal but probably not attainable.  Nevertheless, any
> required configuration MUST be kept to a minimum.
> As an example, under DNS-SD/mDNS the user has always had the option of choosing
> a meaningful <Instance> label for a given service.  If the scope in which this label must
> be unique is too large, the task of name conflict resolution becomes more complex.  This
> may be mitigated by autonomously choosing names with a very low probability of collision,
> but these are user unfriendly.  We need to strike a balance.

One of the things we did for the latest Bonjour Printing specification (and I'm hoping that will actually get published to soon) is to clarify the default instance naming for printers - by default, use a "make and model" string, e.g., "Acme Laser Printer", and if there is a collision either do the normal numbering stuff ("Acme Laser Printer N") or just add a unique identifier that is affixed to the printer - typically a serial number or the last 6 digits of the MAC address, e.g., "Acme Laser Printer (12:34:56)". Not super user-friendly, but at least something a customer can look for on the printer should they actually own two of the same printer.

In addition to showing the printer name in our UI, we also show the location (if set) or serial number (if we have it) under the name - something like the following feeble ASCII art:

    | ACME LASER PRINTER    |     (actual name is "Acme Laser Printer (12:34:56)")
    |   (12;34:56)          |     (no location string, so we show the serial number)
    | ACME LASER PRINTER    |     (actual name is "Acme Laser Printer (78:9A:BC)")
    |   (78:9A:BC)          |     (no location string, so we show the serial number)
    | ACME LASER PRINTER    |     (actual name is "Acme Laser Printer (FE:DC:BA)")
    |   coffee mess         |     (location string set)
    | ACME INKJET PRINTER   |     (actual name, no location or serial)
    | ACME INKJET PRINTER 2 |     (actual name using numbered method)
    |   mike's desk         |     (location string set)

And of course the customer can change the name and location strings if they wish, typically through the printer's web interface.

(Perhaps including a location key in TXT record should be encouraged/required for usability?)

Michael Sweet, Senior Printing System Engineer, PWG Chair