ARP & RARP

ARP
In computer networking, the Address Resolution Protocol (ARP) is the method for finding a host's link layer (hardware) address when only its Internet Layer (IP) or some other Network Layer address is known.
ARP has been implemented in many types of networks; it is not an IP-only or Ethernet-only protocol. It can be used to resolve many different network layer protocol addresses to interface hardware addresses, although, due to the overwhelming prevalence of IPv4 and Ethernet, ARP is primarily used to translate IP addresses to Ethernet MAC addresses.

RARP
Reverse Address Resolution Protocol (RARP) is a Link layer networking protocol used by a host computer to obtain its Internet Protocol (IPv4) address when it has available its link-layer address, such as an Ethernet address.
RARP requires one or more server hosts to maintain a database of mappings from Link Layer address to protocol address. Media Access Control (MAC) addresses needed to be individually configured on the servers by an administrator. RARP was limited to serving IP addresses only.

Hub, Switch, Router & Bridge

Hub



Hub is a networking component which acts as a convergence point of a Network allowing the transfer of data packets. In its simplest form a hub works by duplicating the data packets received via one Port and making it available to all ports, therefore allowing data sharing between all devices connected to the hub.

A hub has 1 broadcast domain and 1 collision domain.


Switch



Switch is almost the same as hub but has different attribute. Switch has 1 broadcast domain and many(subject to number of ports) Collision domain. This is a big boost to network environment as it is faster than hub. Switch consist of a few network bridge.



Router



Unlike hub and switch, router is not just a repeater. Router forwards data packets along networks. Router is use to connect at least 2 networks, example LAN or WAN to its ISP'S network. Router usually placed at gateways.

A router has multiple number of broadcast domains(subject to number of ports).


Bridge



Network bridge or commonly known as bridge is the basic of other advance module such as switch and router.

Broadcast Domain & Collision Domain

Broadcast Domain

A broadcast domain is a logical network segment whereby any network equipment can transmit data directly to another equipment or device without going through a routing device, given the condition that the devices share the same subnet and use the same gateway; also, they must be in the same VLAN.


Collision Domain

Collision domain is also logical network segment in which the data packets can collide to each other. What actually happen is that a single network device sends packets throughout a network segment and forces every other device in that network segment to pay attention to those packets.

TCP/IP & OSI

The TCP/IP is part of the Internet Protocol Suite. Inside the Internet Protocol Suite there are five layers which work together to make the network environment work. These five layers are Application Layer, Transport Layer, Network Layer, Data Link Layer, and Physical Layer. TCP works in the transport layer breaking the data that needs to be send to small parts. Basically it links the application layer with other lower layers. IP however is located in the Network Layer which correspond as address in the networking world.

Open System Interconnection or OSI is basically an older version of TCP/IP or can also be said the early design of Internet Protocol Suite. It has 7 layers of protocol. OSI is then simplified and further compress into 5 layers and is name TCP/IP.

COMPARISON

Focus of Reliability Control

1.Implementation of the OSI model places emphasis on providing a reliable data transfer service, while the TCP/IP model treats reliability as an end-to-end problem.

2.Each layer of the OSI model detects and handles errors, all data transmitted includes checksums. The transport layer of the OSI model checks source-to-destination reliability.

3.In the TCP/IP model, reliability control is concentrated at the transport layer. The transport layer handles all error detection and recovery. The TCP/IP transport layer uses checksums, acknowledgments, and timeouts to control transmissions and provides end-to-end verification.

Roles of Host System

Hosts on OSI implementations do not handle network operations (simple terminal), but TCP/IP hosts participate in most network protocols. TCP/IP hosts carry out such functions as end-to-end verification, routing, and network control. The TCP/IP internet can be viewed as a data stream delivery system involving intelligent hosts.

The Unicode

Unicode is now a computing industry standard where by many developers are using. Windows platform, which everyone of us fond of is also using Unicode as its medium of translating raw data into digital inputs. Unicode takes a leap forward from ASCII by identifying 100, 000 symbols in its inventory.

The sample table of Unicode :

The ASCII Code

The ASCII code is used to represent a specific pre-assigned symbol in the computer. ASCII which stands for American Standard Code for Information Interchange (ASCII) represents character in the computer by translating these symbols into decimal numbers which the only language the computer understands. ASCII consists of 128 characters including a set of 33 hidden control character.

Here is the list of ASCII code.

Test......

testing..... testing.......