ABtalk

 SMTP  -SMTP stands for simple mail transfer   protocol. -SMTP is an application layer protocol. -The transfer protocol of SMTP is TCP(Transmission control protocol)    because TCP is a reliable and connection Oriented protocol.TCP gurantees e-mail delivery . -It uses TCP port 25. -A few webmail services like G-mail use   unofficial port 465 for SMTP. -SMTP requires each message in 7-bit   ASCII(American Standard Code for   Information Interchange ) format. -SMTP is used by the client to send mail to servers because SMTP is a push protocol.It is used to send mail from sender to senders mail server and it is also used to send mail to receivers mail server from senders mail server . - Recepient download the mail from the mail server using POP3 or, IMAP .They can also just view the mail on the server by using webmail. Some SMTP commands:  •HELO and EHLO:- Command that initiate a new protocol session...

  FTP -FTP stands for file transfer protocol. -The Transport protocol of FTP is TCP     because it requires reliability. -The port number of FTP is 20/21.Port 20   performs the task of forwarding and   transferring of data and port 21 performs   the task of transmitting of commands. -It is a standard internet protocol provided   by TCP/IP for transmitting the file(which     may contain any kind of digital   information,such as text document,   movie ,image etc.) from one device to   another. -It is mainly used for transferring the web   page files from their creater to the   computer that acts as a server for other   computer on internet and it is also used   for downloading the files to computer   from other servers. -The main competitor for FTP is Http and   now sites runs Http servers instead of   FT...

TCP/IP stands for Transmission control protocol/Internet protocol.TCP is a transport layer protocol and IP is a network layer protocol .TCP and IP both are different protocol but by the help of these two protocol ,TCP/IP model was developed.TCP/IP model defines how data is transferred from one computer to another.When two devices communicates with each other through the help of internet ,it is possible only for TCP/IP model .The TCP/IP model consists of 4 layers.These are :- (1) Application layer:-  -This layer performs the function of the   top three layer of the OSI model,i.e.Application layer , presentation   layer and session layer . -The application layer is the top-most layer of the TCP/IP model. -The application layer provides the user with the interface to communication. -There are several protocols used by the application layer for interaction such as:FTP,HTTP, SMTP,DNS,TELNET etc. -The application layer sends data to transpo...

TCP vs. UDP  -TCP stands for transmission control   protocol whereas UDP stands for user   datagram protocol. -Tcp is a reliable and connection-oriented   Transport protocol whereas UDP is a less   reliable and connection-less protocol. -In tcp , Error control is   mandatory.because checksum is used at   the end of the TCP to detect errors   whereas error control is optional in case   of UDP . -TCP is comparatively slower than UDP. -The header size of TCP is 20-60 bytes   whereas header size of UDP is 8 bytes . -TCP doesn't supports broadcasting   whereas UDP supports broadcasting . -TCP is used by SMTP,FTP,HTTP,HTTPs   etc, whereas UDP is used by DHCP,DNS etc .

Router  -Router is a internetworking device which is used to connect two or, more different networks. - Router operates on network layer of the OSI model. -It consists of both hardware and software.software is used in router for path determination. -When packet enters into a router ,Router has to read the header of each packet for addresses and compares that address with a table called Routing table .When router finds a match ,it sends packets to the destination. -If router can't decide the destination Path ,at that time it does flooding(kind of broadcast). -Router can do both forwarding and filtering.  -In router,every port has its own broadcast Domain and separate collision domain. -Router can be able to read both IP address and Mac address.

OSI model  OSI stands for open system interconnection .OSI model is a reference model developed by ISO in 1984 ,which defines how data is transferred from one computer network to another computer network .OSI model consists of 7 layers .These are follows-  (1) Application later-  - Application layer is the top-most layer of the OSI model . - Application layer is used by network applications .It means computer application that use internet .Like -Google chrome,Safari etc. - It allows application to communicate with other application.  - Protocols like Http,ftp, telnet,smtp etc, are worked in this layer . (2) Presentation layer- -The presentation layer is also known as Syntax layer . - The presentation layer translates data between the format the network require and the format the computer expects.It means ,it does encryption at sender side and decryption at receiver side.Encryption means changing the plain text into cipher text and decr...

Hub is a networking device which operates on physical layer of the OSI(open system interconnection) model whereas switch is also a networking device but it operates on data link layer of the OSI model .Hub is purely hardware  but switch is a device which is the combination of both software and hardware.Hub supports broadcast transmission whereas switch supports Unicast, multicast and broardcast transmission .Hub is having single collision domain whereas Every port of Switch is separate collision domain.Transmission mode of hub is half-duplex whereas transmission mode of switch is full-duplex.Hub can do only forwarding whereas Switch can be able to do both forwarding and filtering.Hub can't store MAC (media access control) address where as switch stores MAC address.

Transmission mode Transmission mode means Transferring of data between two devices.It is of 3 types .These are - (1)Simplex mode-  Simplex mode of transmission is the simple method of communication.In this type of transmission ,data can be send only through one direction i.e, communication is unidirectional.In this type of transmission, receiver can not send a reply to the sender. Examples are Television remote , keyboard etc. (2)Half-duplex mode-   In half-duplex mode each station can both transmit and receive but can't do both simultaneously.It means when the sender sending data ,at that time receiver can't sends data to the sender.When one device is sending,the other can only receive . Example :-Walkie-talkie . (3)Full-duplex mode-     In this type of transmission ,both station can transmit and receive data simultaneously .It means whenever a sender is sending data to the receiver ,at that time receiver can be able to send...

Swich  Switch is a networking device which is used to connect bunch of devices together in a network through twisted pair cable . It works under data link layer of the OSI(open system interconnection) model. It consists of both hardware and software.so, it can do both forwarding and filtering. When data enters into a switch ,it reads the address and compares that address with  a table called CAM table(content accessible memory where switch maintains port number and MAC address).when it finds a match it sends data to the destination port.Lets take an example for better understand- If pc1 sends data to pc3,First of all data will goes to switch.Then switch reads the  address which is contained in the frame.Then compares that address(MAC address) with CAM table .when it finds a match that pc3 is connected with port number c ,it immediately sends data to the Pc3.It supports unicast , multicast and broardcast transmission.Switch has one broardcast domain . Every p...

Bridge    Bridge is a networking device ,which is used to connect two LANs(local area network). Bridge works under datalink layer of OSI (open system interconnection). Bridge can divide a larger network into two smaller segments.so,Traffic is low in case of Bridge. When packet enters into a bridge,it reads the address(Media access control) and compares that address with a table(containing address of all the nodes of both the segments).When the bridge finds a match ,it sends packet to the destination segment but not to the destination device. Lets take an example for better understand :-   If pc1 sends data to pc5 ,First of all data will goes to bridge then bridge will decide in which segment pc5 is connected.Then bridge will sends data to the destination segment .It means data will goes to pc5  and also data will goes to pc4 and pc6. Here in segment A pc1,pc2 and pc3 is connected and in segment B pc4,pc5 and pc6 is connected. It has 2 Colli...

what is a Hub ? Hub is a networking device which is used to connect multiple devices together in LAN(local area network). Hub works under physical layer of OSI(open system interconnection) model. It is purely hardware device where data reaches from one or, more nodes and is forwarded to one or, more nodes. Traffic is high in hub because it is purely hardware .It has not software to determine the destination address.so,it does only forwarding but not filtering.Lets take an example for better understand:-             If pc1 sends data to pc2,Data will goes to pc2 and also data goes to pc3 and pc4.which means hub can not do filtering .It can do only forwarding.                                                                                  ...