Cse -306


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Cse -306

  1. 1. Presented By- Satyam Pandey Reg No.- 11103875
  2. 2.   Network addresses are numbers.  Addresses are topologically oriented Used for routing purposes Moving a host may require change of address Are not easy to remember  Names can be used for users and for applications Easy for humans Can be used as a low level service discovery mechanism. Changing the server machine requires just changing the name-> IP binding Names can have a logical structure. REQUIREMENT OF DNS
  3. 3.   In the beginning, there was the hosts.txt -A file containing the names and addresses of all hosts in the network -Problems: maintainability, size -Still used as a backup (local network host information)  DNS – Tree-structured – Delegation – Separated from network structure and topology – uses UDP, port number 53 for queries, TCP for zone transfers. HISTORY
  4. 4.  Terms: -namespace = set of possible names, flat or hierarchical. -naming system maintains a collection of bindings of names to values. -given a name, a resolution mechanism returns the corresponding value. -a name server is an implementation of the resolution mechanism. -DNS (Domain Name System) = name service in Internet. -Zone is an administrative unit, domain is a subtree. DNS System
  5. 5.  First level hierarchy -- domains for each country + edu., com., gov., mil., org., net., int. – New domains: aero., biz., coop., info., museum., name., pro. – DNS first level managed by Internet Corporation for Assigned Names & Numbers (ICANN), also manages address allocations. Hierarchy is partitioned into subtrees, zones -- zone corresponds to administrative boundaries in DNS (and, often also of DNS-servers). DNS Domain Hierarchy
  6. 6.  1. Global Distribution  Data is maintained locally, but retrievable globally  No single computer has all DNS data  DNS lookups can be performed by any device  Remote DNS data is locally catchable to improve performance. 2. Loose Coherency  Changes to the master copy of the database are replicated according to timing set by the zone administrator.  Cached data expires according to timeout set by zone administrator DNS features
  7. 7.  3. Scalability  No limit to the size of the database  No limit to the number of queries -- 24,000 queries per second handled easily  Queries distributed among masters, slaves, and caches 4. Reliability  Data is replicated --Data from master is copied to multiple slaves  Clients can query  Clients will typically query local caches  DNS protocols can use either UDP or TCP Contd…
  8. 8.  5. Dynamicity  Database can be updated dynamically  Modification of the master database triggers replication  Only master can be dynamically updated Contd….
  9. 9.   Name servers store information about the name space in units called “zones”.  Usually, more than one name server are authoritative for the same zone  Also, a single name server may be authoritative for many zones Types of Name Server 1.Authoritative – maintains the data  Master – where the data is edited  Slave – where data is replicated to 2. Caching – stores data obtained from an authoritative server. Name Servers and Zones
  10. 10.  Name Server and Zones
  11. 11.  Questions?