Instructions for configuring DNS Service Discovery

TipsMake.com - In essence, DNS Service Discovery (DNS-SD) is a part of Zeroconf networking system - with the function to allow servers and clients on the same network to exchange information and access data in LAN network without any settings or configurations .

Most versions of Linux support the Avahi library for Zeroconf, but most users don't 'exploit' these advantages. In the following article, we together explore the basic setup steps to apply in the for DNS - SD model, initialize the automatic bookmark service, and all that is needed in this test is 1 Apache module and extension - Firefox extension.

The strength of the DNS - SD model is to support Zeroconf applications or hardware devices that transmit DNS SRV record (often used in static DNS systems to point to hosts and other connection ports). announcements, and any other components in the same network, only 'listen' and look for signals coming from here. This model has the function of sending signals through multicast - DNS (mDNS) - the protocol has 'origin' from regular DNS, but has a rather special way of operating, which is based on the based multicast addresses. on local and pseudo domains in local.

This system model is similar to Universal Plug-and-Play (UPnP) , except for the ability to manage and monitor more services, built directly above the DNS layer. The main technology platform of mDNS / DNS-SD is Apple, and with UPnP is Microsoft, so we can easily recognize the 'silent' competition of these two big guys is to stop supporting products. each other's. The user community desires to have a unified IETF protocol in the future, but at the moment mDNS / DNS-SD is still sufficient to meet the needs of the Avahi open source library that Linux users are still daily use.

In the Apple world, devices such as printers and chat clients use mDNS to inform themselves, you can refer here to learn more about the programs supported by system, including VoIP application for server and client (eg Asterisk) . And basically, any service can be recorded information via SRV record, only need to provide translation name case, data transfer protocol (TCP or UDP), port and hostname values ​​of the server are active. Besides, along with the proper configuration of server properties, DNS-SD blocks on the client system will automatically 'capture', sort and classify the services in the local that are being used by programs. In the Linux operating system, Avahi will 'listen' and record mDNS messages and messages, any 'favorite' client program will ask Avahi if any XMPP server exists. That's the whole basic process for making connections.

Refer to some other services:

We can easily imagine how DNS-SD makes it difficult for applications that are difficult to configure like VoIP, but if you are a beginner in this area, start with the familiar HTTP web server protocol. . For those who regularly use Linux, they can use many support tools such as phpMyAdmin, CUPS administration, Webmin .

The principle of consistency is that all web services we want to access can be made from more than 1 computer in the LAN system. You can access each machine or use synchronous tools such as Firefox Sync, Xmarks . but not guarantee the security in terms of security. But with Zeroconf networking , users will no longer have to worry about this problem anymore.

Andrew Tunnell - Jones, a programmer has successfully written a small extension for Firefox to support DNS - SD. The main source code is stored in Github, but users can install the DNSSD utility for Firefox manually, requiring Firefox 4.0 or later (but so far no information is available). Any compatibility with Firefox 5.x). For the Linux operating system, Avahi still works well, and the Mac OS X user community will still be satisfied with Apple's Bonjour, and Windows users are similar with the Bonjour package for Windows. Apples.

After restarting Firefox, this extension will add a menu called DNSSD to the Navigation bar and the Bookmarks menu. Click that, and we will see a list of all HTTP servers that are 'detected' by the Avahi or Bonjour service, no need to perform any further configuration or setup operations. If you want to check the extension list, then use the avahi-browse --all command from the Command Promt window.

In case you are using GNOME, you will see the warning information displayed whenever the system reviews the new service. We can change these settings in the Add - ons Manager Preferences section .

But in fact, users still encounter some shortcomings with this service. Firstly, the utility does not have the option to display the menu of the DNSS, followed by the fact that although we can access the DNSSD menu via Bookmarks, we cannot move and change the location of the utility. You can refer to mod_dnssd for more details.

Mod_dnssd is an Apache module that can add several functions to support mDNS / DNS-SD to websites built with Apache itself, with minimal number of operations, settings or configurations. The latest version is currently 0.6, fully supports Apache 2.2.

To use this module, we need to enable it by replacing the direct DNSSDEnable on character string in the Environment section of apache2.conf . With such independent configuration, Apache will conduct a full inspection of VirtualHosts via mDNS / DNS-SD . By default, mod_dnssd will verify Apache resources such as HTTP services.

Obviously, when we combine the functionality of Apache and Firefox, we can solve some of the problems of DNS - SD, along with the ability to support more HTTP services. However, users should also avoid some of the troubles caused by DNS - SD when automatically activated in the Intranet system, through which other users can easily discover this service. And so, we have to be careful when performing the setup process above, besides DNS-SD-based services can only be 'seen' for LAN client components, and in the case If you want to avoid other Wifi users, you should sort and sort into different subnet ranges. But in fact, there is still one condition for this service model, which is the requirement for Firefox - the client-side application. Good luck!