Zero Configuration Networking with Bonjour

Cheshire

zeroconf mdns dns-sd service discovery network management configuration

@misc{cheshire:google-2005,
  title={Zero Configuration Networking with {Bonjour}},
  author={Stuart Cheshire},
  month={November},
  year={2005},
  note={{Google} {TechTalks}},
  howpublished={\url{http://video.google.com/videoplay?docid=-7398680103951126462#}}
}

[ video ]

Keep things simple

• Wild array of software and hardware that might have to work together
• Simplicity is the only way to get it all to play nicely

Three operations

• Register
• Browse
• Resolve

Three components to labels: <User Visible Name> <Service Type> <Zone>

• E.g.: <Sales> <_ipp._tcp> <.local.>

Example browsing for a printer

  Query: _ipp._tcp.local. PTR
  Response: Sales._ipp._tcp.local.
            Marketing._ipp._tcp.local.
            Engineering._ipp._tcp.local.
            3rd Floor Copy Room._ipp._tcp.local.

Example binding a specific printer

  Query: Sales._ipp._tcp.local. SRV
  Response: Sales._ipp._tcp.local. SRV 0 0 631 my-printer.local.
  Query: Sales._ipp._tcp.local. TXT pdl=application/postscript
  Query: my-printer.local. A
  Response: my-printer.local. A 169.254.12.34

• The SRV request gets the port number to use
• The TXT request gets more information about how to use it, e.g., in this case the page description language and other attribtues (half a K for most printers)
• The A request gets the IPv4 address

Backoff eventually takes you out to querying once per hour

• To avoid that kind of wait, when things join the network they announce themselves
• Short times to live keep things up to date but costs network resources
• Failure to contact devices cause cache to refresh, it's a hint that the cache is out of date
  • Other devices overhear that failure as well and then update their caches
  • Responses by multicast as well, so they're all snooping on other responses

Power over Ethernet is a big complementing plus

• Faster than USB, longer cables, same ease of use with PoE and ZeroConf

Not just for local use, can also query remote domains

• Standard DNS queries issued to that domain

Local resources advertised

• Flight departures at the airport
• Directions to coffee, dinner, etc. at hotel
• Put advertising on those services!

Goes as far as the domains offered by DHCP, domains manually added by user

Printers might need a default printer driver for anything to work on top of and a fancier one you can install with lots of crazy features, color matching, etc.

• Postscript is a good answer, but a lot of low-end printers don't do it

.local. namespace was a contentious issue

• NAT, local IP, etc., definitely have problems, e.g., doing video chat across Internet
• But printing locally, etc., really don't need those kinds of global addresses

Of note:

• Axis network cameras---running full Linux