SEMINAR ONSEMINAR ON

DDNS DDNS(DYNAMIC DOMAIN NAME SERVICE)(DYNAMIC DOMAIN NAME SERVICE)

PRESENTED BY ::B.MANGILALPRESENTED BY ::B.MANGILAL

Under guidance ofUnder guidance of

Ms.keerthi ReddyMs.keerthi Reddy

WHAT IS DNS?WHAT IS DNS?DNS is a service that maps a local name DNS is a service that maps a local name

to an IP address and conversely an to an IP address and conversely an address to a name.address to a name.

DNS STRUCTREDNS STRUCTREDNS works by dividing DNS works by dividing the internetwork into a set of domains or the internetwork into a set of domains or networks that can be further subdivided networks that can be further subdivided into subdomains.into subdomains.

DNS IN INTERNETDNS IN INTERNETIn internet the domain name In internet the domain name space is divided into three different sections.space is divided into three different sections.

RESOURCE RECORDSRESOURCE RECORDS

The information required to resolve The information required to resolve symbolic names is maintained by the symbolic names is maintained by the name server in a set of name server in a set of resource records, resource records, which are entries in a database. which are entries in a database.

The RR will have a TTL value, which can The RR will have a TTL value, which can be used to delete the RR records from the be used to delete the RR records from the cache. Setting the TTL value of all RR cache. Setting the TTL value of all RR records from DDNS to a very small value records from DDNS to a very small value will allow you to make the naming system will allow you to make the naming system dynamic.dynamic.

RESOLVING SYMBOLIC NAMESRESOLVING SYMBOLIC NAMESThe name server operation fall in two The name server operation fall in two

catagories, recursive and nonrecursive.catagories, recursive and nonrecursive.

DNS is usually static which means the IP DNS is usually static which means the IP address for a given host name will be the same address for a given host name will be the same

always,unless it is actually changed.always,unless it is actually changed.

A DDNS will,however, return different A DDNS will,however, return different IPs for the same host name. Each IP IPs for the same host name. Each IP denotes a separate server in the denotes a separate server in the server group.server group.

The IP return for a host name is The IP return for a host name is decided by the distributed server decided by the distributed server load balancing algorithm,which is load balancing algorithm,which is present in the Dispatcher.present in the Dispatcher.

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

DDNS generally used in client server DDNS generally used in client server model.When the load on a single server gets to model.When the load on a single server gets to be too high,it is better to distribute it to a group be too high,it is better to distribute it to a group

of servers using DDNS.of servers using DDNS.The various components of such a system The various components of such a system

are:- are:- (i) DDNS(i) DDNS

(ii) Dispatcher RMI object (ii) Dispatcher RMI object (resides in the DDNS) (resides in the DDNS)

(iii) LoadHandler RMI object (iii) LoadHandler RMI object (resides at each of the servers)(resides at each of the servers)

DISTRIBUTED SYSTEM OF VIEWDISTRIBUTED SYSTEM OF VIEW The following happens,when a client wants The following happens,when a client wants

to send a request to a serverto send a request to a server

1.The client sends a 1.The client sends a DNS request to the DNS request to the DDNSDDNS

2.DDNS communicates 2.DDNS communicates with the available with the available serversservers

3.The IP address of the 3.The IP address of the least loaded server is least loaded server is sent to the clientsent to the client

4.The client sends 4.The client sends request to that serverrequest to that server

server4

OBJECT-ORIENTED VIEW OF THE OBJECT-ORIENTED VIEW OF THE SYSTEMSYSTEM

The sequence of execution is as followsThe sequence of execution is as follows1.DDNS requests the IP 1.DDNS requests the IP

of least loaded server of least loaded server to the Dispatcherto the Dispatcher

2.The dispatcher sends a 2.The dispatcher sends a request to the servers request to the servers for the number of for the number of requests active at that requests active at that time.time.

3.The loadHandler has 3.The loadHandler has an RMI component an RMI component that stores the that stores the number of active number of active connections at that connections at that time.The number of time.The number of connections is sent to connections is sent to the dispatcher.the dispatcher.

4.From the results of the various servers,the 4.From the results of the various servers,the dispatcher decides the least loaded server dispatcher decides the least loaded server

and sends it’s IP to DDNS.and sends it’s IP to DDNS.

5.The DDNS sends the IP to the client.5.The DDNS sends the IP to the client.

DISTRIBUTED SERVER LOAD DISTRIBUTED SERVER LOAD BALANCING ALGORITHM(DSLBBALANCING ALGORITHM(DSLB))

The algorithm is called distributed because The algorithm is called distributed because it is entirely based on loadHandler RMI it is entirely based on loadHandler RMI

components,which are distributed on components,which are distributed on each of the servers in the server group.each of the servers in the server group.

The Dispatcher RMI component at the The Dispatcher RMI component at the Dispatcher will access the the loadHandler Dispatcher will access the the loadHandler

RMI component through RMI.RMI component through RMI.The loadHandler RMI component can be The loadHandler RMI component can be

functionally divided into two types:functionally divided into two types:(I) (I) Application specific:Application specific:

This means that the entire load balancing is This means that the entire load balancing is done for a single application such as a web done for a single application such as a web server. The loadHandler has a counter that server. The loadHandler has a counter that

specifies the number of requests being specifies the number of requests being handled by the web server.handled by the web server.

(2)(2) General:General: This means that the load This means that the load balancing is not specific to any appilication.The balancing is not specific to any appilication.The

load Handler considers all requests to the server.load Handler considers all requests to the server.

HANDLING SERVER FAILURESHANDLING SERVER FAILURES

TheThe dispatcher RMI components in the DDNS dispatcher RMI components in the DDNS will try to access load handler components to will try to access load handler components to

obtain the load .If the server fails the load handler obtain the load .If the server fails the load handler components will not be accessible and so the components will not be accessible and so the dispatcher will mark the server as failed. The dispatcher will mark the server as failed. The

advantage of this approach is that new servers advantage of this approach is that new servers can be added to the server group at any time can be added to the server group at any time without a need to restart the entire system.without a need to restart the entire system.