Apache and Zeroconf Networking

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Apache and Zeroconf Networking

• Sander Temme ltsander_at_temme.netgt

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Agenda

• What is Zeroconf?
• Technology Overview
• Existing Initiatives
• Zeroconf-enabling Apache httpd
• Zeroconf-enabling Tomcat
• Conclusion

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What is Zeroconf?

• IETF Working Group
• Formed in Sept. 1999
• Usability of TCP/IP

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What is Zeroconf?
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What is Zeroconf?

• TCP/IP Autoconfiguration
• Network naming
• Service Browsing

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Technology Overview

• Link-local addressing
• multicast DNS
• DNS Service-Discovery

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Link-local Addressing

• No Central Address Server
• Pick a Random Address
• In 169.254.0.0/16 range
• Address Defense
• Can Work With Centrally Assigned Addresses

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Link-local Addressing
169.254.1.219
Printer
Network
169.254.10.29
169.254.4.51
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mDNS

• DNS-like Protocol
• Every Host Runs Responder
• Hosts Pick Own Names
• Communication over IP Multicast
• Link-local
• Resolves to Link-local or Regular Address

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mDNS
PC_BILL
169.254.1.219
Printer
Network
169.254.10.29
lj21569478
169.254.4.51
PC_LARRY
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DNS-SD

• Service Publishing and Browsing
• Uses Existing DNS Record types
• User Sees Only Service Names
• Works With mDNS or Regular DNS

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DNS-SD
PC_BILL
Laserjet in the Closet Under the Stairs
169.254.1.219
Bills Files
Printer
Network
169.254.10.29
lj21569478
169.254.4.51
PC_LARRY
Larrys Tunes
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Example Applications

• Printer configuration
• Music sharing
• Peer to peer chat
• Gaming
• Telnet server

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Peer to Peer Chat
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Sharing Tunes
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Sharing Sites
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Platform support

• MacOSX 10.2 and up
• Linux several initiatives
• Mandrake
• Windows

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Windows and Rendezvous
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Existing Initiatives

• Apples Rendezvous
• mod_rendezvous
• mod_rendezvous_apple
• jmdns
• dotlocal.org
• zeroconf.sourceforge.net
• Mandrake Linux
• Swampwolf

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Swampwolf

• mDNS deamon and library howl
• API for service registration
• Linux, FreeBSD, Windows
• BSD-style license
• Plugin for Internet Explorer on Windows

http//www.swampwolf.com/
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Zeroconf and Apache httpd

• Module named mod_zeroconf
• Registers Apache Virtualhosts with external mDNS
  responder
• Configurable Service names and paths
• Targeted at Apache httpd 2.0

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Demo
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mod_zeroconf Design
Apache 2.0 Core
Virtual Host Config Info
mod_zeroconf
mDNS Callbacks
Howl mDNSResponder
mDNS Registration
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What Gets Registered?

• Service Name
• SRV information port, hostname, partial URI
• Hostname (if different)
• Callback function

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mod_zeroconf Design
Apache Core
Virtual Host Config Info
mod_zeroconf
Callback Process
mDNS Callbacks
Howl mDNSResponder
mDNS Registration
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Registration Callbacks

• Network can be very dynamic
• Service name, Hostname conflicts
• Apache needs to respond
• Cant block parent process
• fork a child

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Known Issues

• Doesnt know about SSL, other features
• ServerName needs to be nameport
• Callback child is not reaped
• Callbacks are vestigal no conflict resolution
• Host registration not solid code
• Doesnt escape periods in service name
• NO stop/restart/graceful code

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To-dos

• Learn about https protocol
• Learn about DAV,
• Port to MacOSX? Apache 1.3?
• Implement stop/restart
• Alternative mDNS implementations
• IPv6 compatibility
• More solid hostname registration

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Zeroconf-enabling Tomcat

• Ideas
• Java implementation of Zeroconf jmdns
• Or talk to (native) system mDNS
• Use this to register Tomcat webapps
• And web services? With WDSL info?
• How would that interfere with UDDI stuff?
• Dynamic deployment of webapps requires dynamic
  updates of mDNS registration
• No code available yet

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Conclusion

• Zeroconf is great
• Will make networks more usable
• Platform support needed across vendors
• Applications will follow

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Updates

• http//apache.org/sctemme/Apcon2003/TU10/