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Can anyone explain what this option does?

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3 Answers 3

up vote 9 down vote accepted

All computers running Mac OS X contain a feature called Bonjour. It works by sending multicast DNS packets out onto your current network to advertise your computer’s available services. This is how iTunes Sharing works; your computer tells other computers that it has a shared iTunes library available, and gives the computers instructions on where to connect to it. Over the past few weeks, I have been experimenting with an extension of the service called Wide Area Bonjour. Instead of sending out multicast DNS packets to your local network, it sends out similar packets to an actual DNS server, which with the correct authentication, updates actual zones in the DNS server. This essentially allows you to use the magic of Bonjour across many networks, or even the Internet. All that’s required is that each computer that is interested in your Bonjour domain has the domain listed in its “Search Domains” (or “DNS Suffix”). The service I have been testing out is Global Hostname, which will host a Wide Area Bonjour-enabled zone for you, either on your own domain, or a subdomain of globalhostname.org. Apple’s AirPort product range feature Wide Area Bonjour to enable you to control your AirPort from wherever you are.


Its purpose is to provide features similar to those offered by "Back to My Mac" without using the .Mac/MobileMe service. It requires that you have your own DNS server. If your service provider supports secure dynamic DNS update (RFC 3007), you can provide your Mac with a global DNS hostname so that other computers outside your local network can refer to it by name. Even if your computer’s IP address changes at regular intervals, your computer will automatically update its global DNS hostname to point to its current IP address. Your service provider or domain administrator will provide you with the necessary user name and password so your Mac can update its hostname every time its address changes. If your service provider supports Wide-Area Bonjour registrations, you can also select the “Advertise services in this domain using Bonjour” checkbox to advertise this computer’s active Sharing services in this domain. If the domain’s administrator enabled Bonjour browsing for this domain, other computers will see the services listed automatically in the respective application, based on the Search Domains entered in their Network preferences or based on information returned by DHCP. :)

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yes, but what does dynamic global hostname mean? :) –  Robert S Ciaccio Sep 2 '10 at 18:36
the "Added" section seems like they suddenly discovered the description in OS X's built-in help. a better answer might have a screen shot of browsing a bonjour domain in Finder, etc –  username Aug 30 '11 at 5:18

For hostname read domain name such as apple.stackexchange.com, john-pc.local or localhost

localhost is a static local hostname in that it is only accessible to a limited area (in this case a single device) and, by tradition, assigned to the same ip address:

john-pc.local is (potentially) a dynamic local hostname in that while it will always refer to the same pc, the device's ip address will vary*.

(* Well at least it will in most household wi-fi networks where the router assigns devices local ip addresses in a manner which means that the ip address might change from time to time by using Dynamic Host Configuration Protocol or DHCP for short. The same system is frequently used by Internet Service Providers to assign ip address to their subscribers.)

apple.stackexchange.com is a static global hostname in that it is accessible to the while world and semi-permanently* assigned to the same ip address:

(* The ip address can of course be changed but not as part of an automatic software process. )

johndoe.acme-dns-provider.xyz is (potentially) a dynamic global hostname. It is accessible to the while world always points toward the same device but the ip address changes with the device's. Whenever the device's ip address changes special software on the device would log on the the dns providers server and update the ip address record.

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As far as GlobalNames are concerned it is a replacement for the WINS service that many Windows networks rely upon.

On a DNS server it is required to create SRV records and don't think this isn't a security risk. You still need to open ports through your routers firewall to enable the service to work.

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