Hierarchy of Name Servers o Distribute the information among many computers instead of one computer Divide the space into many domains Each domains can be divided further into subdomains o Each domain has a computer, DNS server to take of o hierarchy of servers is the same as that of names 16
16 Hierarchy of Name Servers Distribute the information among many computers instead of one computer ⚫ Divide the space into many domains ⚫ Each domains can be divided further into subdomains Each domain has a computer, DNS server, to take of. Hierarchy of servers is the same as that of names
Hierarchy of name servers root server arpa server edu server com server us server fda. edu mcgraw.com Irwin. com
17 Hierarchy of name servers
Zone o What a serer is responsible for or has authority over is called a zone o If the domain is not divided into subdomain.the“ domain? and the“zone refer to the same thing for a dNs server o The server keeps a database called a zone file and keeps all the information for every node under the domain o The domain and the zone may refer to different things 18
18 Zone What a serer is responsible for or has authority over is called a zone If the domain is not divided into subdomain, the “domain” and the “zone” refer to the same thing for a DNS server. The server keeps a database called a zone file and keeps all the information for every node under the domain The domain and the zone may refer to different things
Zones and domains Root delegation acom) one O hhe omain Zone and o domain 19
19 Zones and Domains delegation
Delegation o Server divides part of its domain and deleg ates responsibility to the lower eⅴ e servers o The zone of a server is made of o information which is not delegated, and reference to the delegated information
20 Delegation Server divides part of its domain and delegates responsibility to the lowerlevel servers The zone of a server is made of ⚫ information which is not delegated, and ⚫ reference to the delegated information