The term delivery refers to the way in which the packet is handled by the networks under the network layer.The network layer handles the packets in the physical network and it is termed as delivery of the packet.
The delivery to the final destination takes place in two ways.
In this method when the source and the destination are located on the same physical network then the delivery takes place.The sender can find out the network address with the addresses of the networks to which it is connected.If the match is found then it is assured that is direct delivery.
In this type of the method the destination is not on the same network as the delivery point from where the packet is to be delivered.Such type of the delivery is termed as the indirect type of delivery.
Note: A delivery always involves one direct delivery but zero or more indirect delivery.
Forwarding means the way in which the packet is delivered to the next station.The various forwarding techniques are:
1)Next Hop Method
The technique which reduces the contents of the routing table is called next hop method
In this method the routing table contains the address of the next hop instead of the information of the complete route.
3)Network Specific Method
It is the technique in which the routing table is reduced and the searching process is simplified.
4)Hot Specific Method
In this method entry of every destination is connected to the same physical network.
Here we make the assumption that the routers and the hosts use the classless addressing as we know that the classful addressing can be treated as the special case of the classless addressing.In the case of the classless addressing the routing tables needs to have one row of information for each of the blocks.The table which is to be searched is based on the network address.It is to be noted that the destination address gives no idea about the network address.To solve the problem we need to involve the mask in the table i.e. we need to take an extra column that includes the mask for the corresponding block.
The term Routing signifies the way routing tables are created to help in the forwarding process.To continuously update the routing tables the routing protocols are used.A router has the routing table with the entry for each destination to route the IP packets.The routing packet can be of two types.
1)Static Routing Table
It contains the informations entered manually.The route for each destination is entered into the table by the administrator.It can be used in the small internet which is not to be changed quite often.It will be the case of poor strategy if the static routing table is to be used in the big internet.
2)Dynamic Routing Table
This table is updated timely using the dynamic protocols such as RIP,OSPF or BGP.Whenever changes occur in the internet then the dynamic routing protocols update all the tables in the router automatically for the efficient delivery of the IP packets.
Unicast Routing Protocols
As we know that the dynamic routing table is the demand of the todays internet.The tables needs to be updated whenever there are changes in the internet.The routing protocols have been created for the dynamic routing tables.It is the combination of the certain rules and the procedures which let the router know about the changes in the internet.It even allows the router to share the informations abot the internet and their neighbourhood
The function of the router is to receive the packets from the network and then passes it to the other network.The router is connected to the various networks.The optimization makes the decision that when the router receives the packet to which network the packet is to be passed on and out of the available pathways the optimum path is to be selected.The term optimium can be explained as the one approach to assign the cost for the passing network and this assigned cost is called metric.The metric is assigned to the networks depending on the type of the protocols.
1)Routing Information Protocol(RIP)-In this the cost of passing the network is all same.All the networks are treated as same in this protocol.
2)Open Shorted Path First(OSPF)-It allows the administrator to assign the cost for passing through the network based on the type of the service required.A route has different cost through the network.
3)Border Gateway Protocol-(BGP)The cfriteria is based on the policy and the policy decides which path is to be choosen by the administrator.
Intra-Domain Routing and Inter-Domain Routing
In today’s era the internet has become such a vast network that it will be impossible for one routing protocol to perform the task of updating the routing table of all the routers.For such a reason the internet is divided into the autonomous systems.The autonomous system(AS) can be defined as the group of the networks and routers under the authority of the single administration.
1)When the routing is done inside the autonomous system then it is referred as INTRA-DOMAIN ROUTING.Each autonomous system can choose either one or more than one intra domain routing protocols to handle the routing in the autonomous systems.
2)When the routing is done between the autonomous systems then it is known as INTER DOMAIN ROUTING.Each autonomous system can choose only one inter domain routing protocol to handle the routing between the autonomous systems.
Distance Vector Routing
In this the minimum cost route between any two nodes is the route with the mnimum distance.Each node is given the vector of minimum distance to every node.The table at each node instructs the packets to their node by showing the next stoppage in the route.It is the Intra domain routing protocol.
Link State Routing
Link state routing is quite different in the concept than the distance vector routing.If each node in the domain has the entire topology of the domain then the entire list of the links and the nodes,cost including the condition of the links the Dijkstra’s algorithm can be used in this case to build the routing table.It is the Intra domain routing protocol.
Path Vector Routing
Path vector routing is used in the inter domain routing.Its principle is same as the distance vector routing.In this lets assume that a node in each autonomous system can act on the behalf of the entire autonomous systems.This particular node can be called as the speaker node.The speaker node in the autonomous system creates the routing table and advertises it to the speaker nodes of the neighbouring autonomous systems.The speaker node in each autonomous system can freely communicate with each other.It is to be noted that the speaker node advertises the paths not the metric nodes.
MULTICAST ROUTING PROTOCOLS
Unicast, Multicast, and Broadcast
In this communication there is one source and one destination.There is one to one relationship between source and the destination.The address of the source and the destination in the IP diagram are the unicast address which are assigned to the host.In the unicasting when the router receives the packets the packet is forwarded through only one of its interfaces as described in the routing table.A packet can be discarded by the router if it is unable to find the destination address in the routing table.
In this type of the communication there is one source and group of the destinations.The relation is one to many type.The source address is the unicast address but the destination address is the group address i.e it defines one or more destinations.The group address identifies the members of the group.When the router receives the packet it forwards it through the several of its interfaces.In this type of the communication technique the router forwards the received packets.
In this communication on the relationship between the source and the destination is one to all. In this one host is the source and other hosts are the destinations.The internet does not support the broadcasting as there is huge amount of the traffic and because of the bandwidth it needs.
Multicasting technique has many applications in day today.
1)Access to the distributed databases.
The information is stored in more than one location at the time of the production.The user who needs to access the data does not know about the location of the information.In the multi cast to all the data base location and the location has the information responds.
Bussiness often sends the information to the customers and the nature of the information has to be same for each customer.
It involves multicasting.The indivisual attending the teleconference.Temporary or permanent groups can be formed for this purpose.
One growing area in the use of multicasting is the distance learning.It is convenient for the students who find it difficult to attend the classes on the campus.
In the case of the multicasting the concept of the optimal routing is to be considered.
Optimal routing routing:shortest path trees
In this the root of the tree is the source and the leaves are the potential destination.The path from the roots to the destination is considered as the shortest path.
The formation of the trees and the number of the trees varies in the multicating and unicasting.
In the multicast routing when the router receives the multicast packet,it might have destinations in more than one network.Forwarding it requires the shortest path of the tree.if there are n groups then n shortest path trees are needed.
1)Distance Vector Multicast Routing Protocol is an implementation of the multicast distance vector routing.It can said as the source based routing protocol which is based on the RIP.
2)Core based tree protocol is nothing but a group shared protocol that uses the core as the root of the tree.The AS system is divided into various regions and the core is chosen from this region
3)Protocol independent Multicast is the name which is given to the two independent multicast routing protocols.
a)Protocol Independent multicast Dense Mode(PIM-DM)
b)Protocol Independent.Multicast Sparse mode(PIM-SM)
PIM-DM is used in the case when there is the probability that each router is involved in the multicasting.In this all the routers are involved in the process to broadcast the packets.
PIM-SM is used when there is possibility that each router is involved in the multi casting.The use of the protocols that are used to broadcast the packet are not justified.It is basically used in the multicast environment such as WAN.
Related Questions and Answers
Q.What are the delivery techniques??
There are two types of the delivery techniques
1. direct delivery 2.indirect delivery
Q what is the concept of forwarding??
The Forwarding is the process in which the data are forwarded to the destination.
Q.What is multicasting??
In the multi casting the data packet is to be delivered from the single source to the multiple destinations.
Q what do you mean by the term Routing??
The term routing means the way the routing tables are created to help out in the forwarding process.