Properties of dns Host Entries Different kinds of mappings are possible Simple case: 1-1 mapping between domain name and IP addr: kittyhawk cmcl.Cs. cmu. edu maps to 128.2.194.242 Multiple domain names maps to the same IP address eecs. mit. edu and cs. mit. edu both map to 18.62.1.6 Single domain name maps to multiple IP addresses aolcomandwww.aol.commaptomultipleIpaddrs Some valid domain names dont map to any IP address for example: cmcl. cs. cmu. edu Lecture13:10-10-2006
Lecture 13: 10-10-2006 11 Properties of DNS Host Entries • Different kinds of mappings are possible: • Simple case: 1-1 mapping between domain name and IP addr: • kittyhawk.cmcl.cs.cmu.edu maps to 128.2.194.242 • Multiple domain names maps to the same IP address: • eecs.mit.edu and cs.mit.edu both map to 18.62.1.6 • Single domain name maps to multiple IP addresses: • aol.com and www.aol.com map to multiple IP addrs. • Some valid domain names don’t map to any IP address: • for example: cmcl.cs.cmu.edu
DNS Design: Hierarchy Definitions Each node in hierarchy stores a list of names that root end with same suffix org Suffix= path up tree net edu com uk E.g., given this tree, where would following be stored gwu ucb cmu bu mit Fred. com Fred. edu Cs ece Fred. cmu. edu cmc Fred cmcl. cs cmu. edu Fred. cs mit. edu Lecture13:10-10-2006
Lecture 13: 10-10-2006 12 DNS Design: Hierarchy Definitions root net edu org com uk gwu ucb cmu bu mit cs ece cmcl • Each node in hierarchy stores a list of names that end with same suffix • Suffix = path up tree • E.g., given this tree, where would following be stored: • Fred.com • Fred.edu • Fred.cmu.edu • Fred.cmcl.cs.cmu.edu • Fred.cs.mit.edu