Computer Network Tutorial

Introduction of Computer Network Types of Computer Network Network Topology Computer Networking Architecture Transmission Modes (Data Flow) Basic Networking Devices Integrate Services Digital Network (ISDN)

Model

OSI Model TCP/IP Model

Physical Layer

Digital Transmission Analog Transmission Transmission Media Switching

Data Link Layer

Error detection and Error correction Data Link Control Multiple Access Aloha

Network Layer

Network Layer - Logical Address Address Mapping Unicast Routing Protocol

Transport Layer

Process to Process Delivery User Datagram Protocol Transmission Control Protocol Stream Control Transmission Protocol Session Layer and Presentation Layer

Application Layer

Domain Name System Application Protocol E-mail Cryptography

Misc

Classes of Routing Protocols Classification of Routing Algorithms Controlled Access Protocols in Computer Networks Differences between IPv4 and IPv6 Fixed and Flooding Routing Algorithms Advantages and Disadvantages of Fibre Optics Cable APIPA Difference between Active and Passive FTP Fiber Optics and its Types Method of Joining and Fusion of Fiber Optic Cable Define Framing in Computer Network Disadvantages of Computer Network Mesh Topology Diagram in Computer Network Ring Topology in Computer Network Star Topology in Computer Networks 4G Mobile Communication Technology Advantages and Disadvantages of LAN Advantages and Disadvantages of MAN Advantages and Disadvantages of WAN Application Layer in OSI Model Cyclic Redundancy Check Example Data link layer in OSI model Difference between Transport and Network Layer Hamming Code Example Network Layer in OSI Model Session Layer in OSI Model Transport Layer in OSI Model Two Port Network in Computer Networks Uses of Computer Networks What is Computer Network What is Framing in a Computer Network Advantages and Disadvantages of Bus Topology Difference between Star Topology and Bus Topology Subnetting in Computer Network Subnetting Questions and Answers What is Bus Topology What is Network Topology and Types in Computer Networks Access Control in Networking Basic Characteristics of Computer Network Benefits of SOCKS5 Proxy in Computer Networks Computer Network viva Questions Difference between BOOTP and RARP Difference Between Network Topologies and Network Protocols Difference between NFC and RFID Difference Between Point-to-Point Link and star Topology Network Differences Between MSS and MTU Differences Between Trunk Port and Access Port Different Modes of Communication in Computer Networks MIME Protocol in Computer Networks Modes of Communication in Computer Networks Network Attack in Computer Network Port Address in Networking Simplest Protocol in Computer Network Sliding Window Protocol in Computer Network Stop And Wait Protocol in Computer Networks TCP 3-Way Handshake Process in Computer Networks What is a Proxy Server What is APPN What is ICMP Protocol What is Point-to-Point Protocol What is Port Address in Networking What is the HDLC Protocol What is VRRP Protocol Difference Between Analog and Digital Signals Difference Between Hub and Repeater Difference between Repeater and Switch Difference Between Transparent Bridge and Source Routing Bridge Source Routing Bridge in Computer Networks Transparent Bridge in Computer Networks Transport Protocol in Computer Networks Types of CSMA in Computer Networks What is Wired and Wireless Networking Network Security in Computer Network Disadvantages of Extranet Difference Between TELNET and FTP Define Protocol in Computer Networks Guided Transmission Media in Computer Network What is a Gateway in a Computer Network IGMP in Computer Networks LAN Protocols in Computer Networks MAN Meaning in Computer Modulation Techniques in Computer Networks Switching in DCN TCP/IP Applications What is IGMP? What is Modem in Networking What is Non-Persistent CSMA Difference between Cell Splitting and Cell Sectoring Forouzen Computer Network

E-mail in Computer Network

E-mail

E-mail stands for electronic mail. E-mail is an application layer service in which a user can transfer the messages and information with another user. E-mail is the most popular service of the internet.

Architecture

There are four scenarios in the architecture of electronic mail (e-mail).

First Scenario

In the first scenario of e-mail, the sender and receiver use the same system, and that is directly connected to the server. This scenario requires only two user agent (UA).

E-mail in Computer Network

For example, let takes two user agents (Alice and Bob), that is shown in the figure. When Alice sends the mail to Bob, then Alice runs the user agent (UA) program to prepare the e-mail. After that, this e-mail is stored in the mailbox of Bob.

Second Scenario

In the second scenario of e-mail, the sender and receiver are used the two different systems. The e-mail is sent through the internet in this scenario. This scenario requires two user agents (UAs) and a pair of message transfer agents (MTAs). The example of this scenario is shown in the figure.

E-mail in Computer Network

For example, let takes two user agents (Alice and Bob), which is shown in the figure. When Alice sends the mail to Bob, then Alice runs the user agent (UA) and message transfer agents (MTAs) program to prepare the e-mail through the internet. After that, this e-mail is stored in the mailbox of Bob.

Third Scenario

In the third scenario of e-mail, the sender is connected to the server through a LAN and WAN. This scenario requires two user agents (UAs) and two pairs of message transfer agents (MTAs). The example of this scenario is shown in the figure.

E-mail in Computer Network

Fourth Scenario

In the fourth scenario of e-mail, the sender and receiver are connected to the server through a LAN and WAN. This scenario requires two user agents (UAs), two pairs of message transfer agents (MTAs), and a pair of message access agents (MAAs). The example of this scenario is shown in the figure.

E-mail in Computer Network