Zero%20Configuration%20Networking

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Zero Configuration Networking

• Sander Temme
• ltsander_at_temme.netgt

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Agenda

• What is Zero Configuration Networking
• Demonstration
• Description of Protocols
• Available Implementations
• Usage Sample

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Agenda

• What is Zero Configuration Networking
• Demonstration
• Description of Protocols
• Available Implementations
• Usage Sample

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Agenda

• What is Zero Configuration Networking
• Origins
• What Problems does it Solve?
• What Problems does it Not Solve?

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Origins
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Origins IETF

• Zero Configuration Working Group
• Established September 1999
• Charter fragment

The goal of the Zero Configuration Networking
(ZEROCONF) Working Group is to enable networking
in the absence of configuration and
administration.
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Problems Solved

• Automatic IP Address Configuration
• Server-free Hostname Resolution
• Directory-less Service Discovery

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Problems Not Solved

• Security
• Authenticity
• Access Control
• Wide Area Networks (for now)

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Applications

• Printing
• Zero Configuration Chat
• Music Sharing and Streaming (iTunes)
• Tivo streaming photos, music to TV
• Gaming (NASCAR Racing 2002)
• Many devices without interface

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Agenda

• What is Zero Configuration Networking
• Demonstration
• Description of Protocols
• Available Implementations
• Usage Sample

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Agenda

• What is Zero Configuration Networking
• Demonstration
• Description of Protocols
• Available Implementations
• Usage Sample

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IP Address Autoconfiguraton

• In Absence of DHCP Server
• Link-local Addressing
• Solved by IPv6
• IPv4 pick random in 169.254/16
• Address Defense
• Multihomed systems only one interface
• Supported on Mac and Windows

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Link-local Addressing
Printer
169.254.1.219
169.254.10.29
Network
169.254.4.51
169.254.4.51
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Hostname Resolution

• In Absence of DNS Server
• Multicast DNS
• DNS-like protocol
• Every host has responder
• Listens on 224.0.0.251 and/or ff02fb
• Hostnames picked by user
• Hostname defense

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mDNS
PC_Bill
Printer
169.254.1.219
169.254.10.29
lj21569478
Network
Mac_Steve
169.254.4.51
PC_Larry
169.254.4.51
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Service Discovery

• Human-readable Service Names
• Runs on mDNS
• Query for Service Type returns list
• Long-lived queries
• Service Name resolves to
• hostname
• port, add. info
• IP address

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DNS-SD
Laserjet, Closet Under the Stairs
PC_Bill
Printer
169.254.1.219
169.254.10.29
Bills Files
lj21569478
Network
Mac_Steve
169.254.4.51
PC_Larry
169.254.4.51
Steves Movies
Larrys Tunes
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Agenda

• What is Zero Configuration Networking
• Demonstration
• Description of Protocols
• Available Implementations
• Usage Sample

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Bonjour

• First implementation on market
• Apple Trademark
• Introduced in Mac OS X 10.2
• Incorporated in iTunes for Windows
• Recently Released under APSL
• For Windows, POSIX platforms, Java

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Howl

• Open Source from Porchdog Software
• Mostly BSD Licensed
• Windows, FreeBSD, Linux, MacOSX
• C, .NET API

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jmdns

• Pure Java mDNSResponder
• LGPL
• Last Release 11/2003 check CVS

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Agenda

• What is Zero Configuration Networking
• Demonstration
• Description of Protocols
• Available Implementations
• Usage Sample

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Java Example SimpleChat

• 179 non-comment LOC
• Listen on ephemeral port
• Advertise on mDNS
• Listen for other instance on mDNS
• Put found instances in pop-up menu
• Send chat messages to selected partner

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Bonjour in Java

• Factory Class DNSSD
• Interfaces define callbacks

BrowseListener Service Browsing
ResolveListener Name Resolution
RegisterListener Service Registration
QueryListener DNS Record Resolution
DomainListener Domain Resolution
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Example Browsing

• Call Browse method
• pass in class that implements BrowseListener
• serviceFound() when service appears
• serviceLost() when service goes away
• Interface methods manipulate pop-up menu

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Demo
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Conclusion

• Easy to use
• Cross-platform
• Dynamic
• Configuration-free

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More Information

• http//developer.apple.com/networking/bonjour/
• Developer Info
• http//www.apple.com/macosx/features/bonjour/
• Marketing
• http//www.zeroconf.org/ (IETF site)
• http//www.dotlocal.org/ (Kinda stale)
• http//www.porchdogsoft.com/ (Howl)
• http//www.lists.apple.com/mailman/listinfo/bonjou
  r-dev

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More Info LL IP Addressing

• Generally happens after DHCP times out
• Host picks Random Address
• Sends out ARP Request for Address
• If no Answer, Assumes Address
• If Answer, Host Starts Over

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More Info mDNS

• DNS-like Protocol
• All Hosts Listen on Multicast 224.0.0.251, port
  5353
• All Hosts authoritative for .local. domain
• Short-lived Hostname Cache
• Introductory Unsollicited Response
• Goodbye Packet (TTL 0)

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More Info DNS-SD

• Uses DNS PTR Records
• PTR of form Service Name._http._tcp.local.
• Free-form Service Name
• Enumeration browsing for _http._tcp.local. gives
  list of web service instances
• Resolving Instance Name yields hostname, TXT
  record with port info, etc.