1.1 What is Computer Network?
The group of computers and devices linked by communication channels allowing users to share information, data, software and hardware with further users is meant to be computer network. Network protocols bound hardware as well as software components of network.
Two or more computers are said to be in a network if and only if they are connected mutually and are able to commune. Computers are connected to a network by the use of all the ports i.e., parallel ports, modem ports, Ethernet ports, serial ports, USB ports , fire wire ports and many more in one or more way. But Ethernet port is the most broadly used ports for networking.
Hosts, end stations or workstations are referred while talking about networks. Anything attached to the network including hubs, bridges, switches, routers, access points, firewalls, workstations, servers, mainframes, printers, scanners, copiers, fax machines and more are included under Host or end stations .
Computers are connected in a network for sharing of software and hardware resources, information and data as well as smooth the progress of communication.
1.2 TCP/IP Layered architecture
Fig: TCP/IP Layered architecture
The following are the layers of the TCP/IP architecture:
In the application layer Simple Mail Transfer Protocol (SMTP) and File Transfer Protocol (FTP) uses protocol for network communication. Application layer protocols are most frequently linked with client-server applications.
End-to-end message transfer capability, flow control, error control and fragmentation etc are provided by the transport layer. The transport layer ensures source to destination delivery of packets safely and reliably. The service through which applications are connected together via the use of ports is provided by transport layer.
Packets are logically transmitted over the entire network in the OSI’s Network layer. Hosts addressing by assigning them an IP address and packet routing among multiple networks are handled in this layer. This layer is concerned with routing data; end to end message delivery etc.
The data exchange between the host and the network are monitored by the interface layer. The protocols for physical transmission of data is defined by Interface Layer .
1.3 Autonomous System
IP networks and routers collection under the control of one entity representing a common routing policy is called an Autonomous System. Each AS have a unique AS number for use in routing. Each network is uniquely identified on the internet by ASN. IANA (Internet assigned Numbers authority) assign AS numbers and supply to Regional internet Registries (RIRs) in blocks.
Autonomous System can be divided into three categories:
Multihomed Autonomous System: Connections to more than one AS is maintained by a Multihomed AS.
Stub autonomous System: Connection to only one other AS is Stub autonomous System.
Transit autonomous System: Connections through itself to separate networks are provided by Transit autonomous System.
The method of selecting paths in a network via which to send data is meant to be routing. The process of finding a pathway from a sender to a desired destination is also said to be routing. The telephone network, the internet and transport networks, etc perform routing. Network Layer of either TCP/IP layered model or the OSI (Open System interconnect) Reference model mainly carry out routing.
The logically addressed packets are passed from their source to destination via intermediary nodes i.e. forwarding is directed by routing. Routing tasks are performed by routers. Routing and packet forwarding is performed by ordinary computers available with multiple network cards in a limited manner. Forwarding is directed by the routing process on the basis of routing tables where routing record to different...