BROCADE IP PRIMER

Chapter 18: Global Server Load Balancing (GSLB)Domain Name Service (DNS) is a service that provides the ability to resolve aname to an IP address, and vice versa. On the Internet, you would submit aname (e.g., www.brocade.com) and, through DNS, you would get a response(e.g., 63.236.63.244). Now your packets and communications have a Layer 3address that they can use to communicate across the Internet.The concept of resolving names to Layer 3 addresses is actually as old as theInternet itself (perhaps older). Name resolution started by keeping entries in afile. In a way, this file served much the same purpose as a phone book(though, not nearly as large). It was simply a text file that listed a name (e.g.,www.brocade.com) and the IP address it belongs to (e.g., 63.236.63.244).This system lasted for about 20 years, and is still in use today. Most operatingsystems provide a “hosts” or “hosts.txt” file that you can edit and provide yourown local resolutions.In 1983, a man by the name of Paul Mockapetris came up with the concept ofDNS, and wrote the first implementation. It is now referred to in the IETF RFC'sas RFC 1034 and RFC 1035 (written in 1987). In 1984 and 1985, a UNIXbasedsoftware program called BIND (Berkeley Internet Name Domain) wascreated to service DNS. This has remained one of the most popular programsfor serving DNS.DNS HierarchyDNS functions based on a hierarchy. The “hosts” file system didn't work toowell, because it required every individual workstation to know how to resolveevery address on the Internet. That would have been fine in the 1970's, butnow, the file would be huge (and would have to be constantly updated). DNSdoesn't function on the concept of centrally storing all of the names that needto be resolved. Instead, it uses a hierarchy to distribute the resolution to amore specific structure.. (Root)Top-Level Domains (TLD).gov.edu.com .net .orgParent Domain/ZoneAppleBrocadeMicrosoftHost/Sub-Zonekp wwwincoming 1Not too many people realize that a Fully-Qualified Domain Name (FQDN)should properly be written with a period at the end of the name (e.g., www.brocade.com.).That period represents the Root of the DNS hierarchy. A nameconsists of a series of groups that are separated by a period. For example, let's388 Brocade IP Primer