1. SEMINAR ON DDNS (DYNAMIC DOMAIN NAME SERVICE)
PRESENTED BY ::B.MANGILAL
Under guidance of
Ms.keerthi Reddy

2. WHAT IS DNS?
DNS is a service that maps a local name to an IP address and conversely an address to a name.
DNS STRUCTREDNS works by dividing the internetwork into a set of domains or networks that can be further subdivided into subdomains.

3. DNS IN INTERNETIn internet the domain name space is divided into three different sections.

4. RESOURCE RECORDS
The information required to resolve symbolic names is maintained by the name server in a set of resource records, which are entries in a database.
The RR will have a TTL value, which can be used to delete the RR records from the cache. Setting the TTL value of all RR records from DDNS to a very small value will allow you to make the naming system dynamic.

5. RESOLVING SYMBOLIC NAMES The name server operation fall in two catagories, recursive and nonrecursive.

6. DNS is usually static which means the IP address for a given host name will be the same always,unless it is actually changed.
A DDNS will,however, return different IPs for the same host name. Each IP denotes a separate server in the server group.
The IP return for a host name is decided by the distributed server load balancing algorithm,which is present in the Dispatcher.

7. Key Features of DDNS  Can map your domain name to servers even without a static IP address  1/3 cost of Fixed IP  Enable users to operate Internet services such as web, or chat server in home environment  No extra equipment required

8. DDNS generally used in client server model
DDNS generally used in client server model.When the load on a single server gets to be too high,it is better to distribute it to a group of servers using DDNS. The various components of such a system are:- (i) DDNS (ii) Dispatcher RMI object (resides in the DDNS) (iii) LoadHandler RMI object (resides at each of the servers)

9. DISTRIBUTED SYSTEM OF VIEW The following happens,when a client wants to send a request to a server
1.The client sends a DNS request to the DDNS
2.DDNS communicates with the available servers
3.The IP address of the least loaded server is sent to the client
4.The client sends request to that server
server4

10. OBJECT-ORIENTED VIEW OF THE SYSTEM The sequence of execution is as follows
1.DDNS requests the IP of least loaded server to the Dispatcher
2.The dispatcher sends a request to the servers for the number of requests active at that time.
3.The loadHandler has an RMI component that stores the number of active connections at that time.The number of connections is sent to the dispatcher.

11. DISTRIBUTED SERVER LOAD BALANCING ALGORITHM(DSLB)
4.From the results of the various servers,the dispatcher decides the least loaded server and sends it’s IP to DDNS.
5.The DDNS sends the IP to the client.
DISTRIBUTED SERVER LOAD BALANCING ALGORITHM(DSLB)
The algorithm is called distributed because it is entirely based on loadHandler RMI components,which are distributed on each of the servers in the server group.

12. The Dispatcher RMI component at the Dispatcher will access the the loadHandler RMI component through RMI. The loadHandler RMI component can be functionally divided into two types: (I) Application specific: This means that the entire load balancing is done for a single application such as a web server. The loadHandler has a counter that specifies the number of requests being handled by the web server.

13. (2) General: This means that the load balancing is not specific to any appilication.The load Handler considers all requests to the server. HANDLING SERVER FAILURES The dispatcher RMI components in the DDNS will try to access load handler components to obtain the load .If the server fails the load handler components will not be accessible and so the dispatcher will mark the server as failed. The advantage of this approach is that new servers can be added to the server group at any time without a need to restart the entire system.

14. THANK YOU