28 CHAPTER 1: WEB CACHING CONCEPTS AND DEPLOYMENT The second part identifies the device on that subnet.The bits of the subnet mask are set to 1 if the device is to treat thecorresponding bit in the IP address as part of the original networknumber or as part of the subnet number. These bits in the mask are set to0 if the device is to treat the bit as part of the device number.Domain Name System The Domain Name System (DNS) maps a numerical Internet Protocol (IP)address to a more meaningful and easy-to-remember name. When youneed to access another device on your network, you enter the name ofthe device, instead of its IP address. A Domain Name System server onyour network is contacted and asked the electronic form of the question,“What is the IP address of the destination device?”. The DNS server is amachine that keeps track of all the names and their equivalent numeric IPaddresses. The DNS server responds with the correct IP address (e.g.128.118.2.23), allowing the two devices to communicate with eachother.To enable the Domain Name System, you must setup one or more DNSservers on your network. If you are uncertain about how to do this,contact your network administrator.The following Webcache features are only available if you have setup aDNS server: Caching — The Webcache will be unable to cache Web content if aDNS server is not setup. The Webcache must resolve the host namesaccessed by the Web browser in order to serve the content. Access to the Webcache by DNS Name — You can access the Webinterface or Command Line Interface of the Webcache via its DNSname, rather than its IP address e.g. webcache.mycompany.com. Web Proxy Auto-Discovery (WPAD) — This protocol can be used toconfigure Web browsers on client machines in a Proxy Cachedeployment. For further information, see “Web Proxy Auto-Discovery(WPAD)” on page 49.Domain Name SystemSyntaxYou must use the following syntax for the DNS host name and domainname: Host Name The host name must be at least 1 character long.dua1611-5aaa04.book Page 28 Friday, November 29, 2002 8:56 PM
