MODULE 1 Flashcards
(11 cards)
.Explain encapsulation and decapsulation with neat block diagram
Encapsulation at the Source Host
At the source, we have only encapsulation.
1. At the application layer, the data to be exchanged is referred to as a message. A
message normally does not contain any header or trailer, but if it does, we refer to
the whole as the message. The message is passed to the transport layer.
2. The transport layer takes the message as the payload, the load that the transport
layer should take care of. It adds the transport layer header to the payload, which
contains the identifiers of the source and destination application programs thatwant to communicate plus some more information that is needed for the end-toend delivery of the message, such as information needed for flow, error control, or
congestion control. The result is the transport-layer packet, which is called the segment (in TCP) and the user datagram (in UDP). The transport layer then passes the
packet to the network layer.
3. The network layer takes the transport-layer packet as data or payload and adds its
own header to the payload. The header contains the addresses of the source and
destination hosts and some more information used for error checking of the header,
fragmentation information, and so on. The result is the network-layer packet,
called a datagram. The network layer then passes the packet to the data-link layer.
4. The data-link layer takes the network-layer packet as data or payload and adds its
own header, which contains the link-layer addresses of the host or the next hop (the
router). The result is the link-layer packet, which is called a frame. The frame is
passed to the physical layer for transmission.
decapsulation with neat block diagram
Decapsulation and Encapsulation at the Router
At the router, we have both decapsulation and encapsulation because the router is connected to two or more links.
1. After the set of bits are delivered to the data-link layer, this layer decapsulates the
datagram from the frame and passes it to the network layer.
2. The network layer only inspects the source and destination addresses in the datagram
header and consults its forwarding table to find the next hop to which the datagram is to
be delivered. The contents of the datagram should not be changed by the network layer
in the router unless there is a need to fragment the datagram if it is too big to be passed
through the next link. The datagram is then passed to the data-link layer of the next link.
3. The data-link layer of the next link encapsulates the datagram in a frame and
passes it to the physical layer for transmission.
Decapsulation at the Destination Host
At the destination host, each layer only decapsulates the packet received, removes the
payload, and delivers the payload to the next-higher layer protocol until the message
reaches the application layer. It is necessary to say that decapsulation in the host
involves error checking.
.Discuss in detail about guided media for transmission
Guided media, which are those that provide a conduit from one device to another,
include twisted-pair cable, coaxial cable, and fiber-optic cable. A signal traveling
along any of these media is directed and contained by the physical limits of the
medium. Twisted-pair and coaxial cable use metallic (copper) conductors that accept
and transport signals in the form of electric current. Optical fiber is a cable that accepts
and transports signals in the form of light
Write short notes on multiplexing and demultiplexing
Multiplexing:
Multiplexing refers to the process where multiple data streams (applications or processes) are combined and sent through a single network connection.
At the source, the transport layer collects data from different applications, assigns each data stream a port number, and then passes them down to the network layer. The transport layer encapsulates each data stream with the necessary headers, allowing them to travel over the same connection.
Demultiplexing:
Demultiplexing is the reverse process, which occurs at the destination.
At the receiving end, the transport layer looks at the incoming packet’s header to determine which application or process the data belongs to based on the port number. It then delivers the data to the correct application.
This is how the transport layer distinguishes between multiple data streams sent to the same device.
Switching
Switching in networking refers to the process by which data is directed to its destination across a network. This process involves switching devices such as routers or switches, which use different techniques to route data from one node to another. Switching plays a vital role in handling network traffic efficiently by determining the best path for data to travel between the sender and receiver.
There are three primary types of switching techniques:
Circuit Switching - Used in traditional telephone networks.
Packet Switching - Commonly used in modern data networks.
Message Switching - Rarely used today but was prominent in early telecommunication systems
Datagram Switching
Datagram Switching (Packet Switching)
Datagram switching is a form of packet switching. In this method, data is divided into small packets, and each packet is sent independently through the network. Each packet might take a different route to the destination based on the availability of network resources, and they may arrive out of order.
Key Characteristics of Datagram Switching:
No Pre-established Path: Unlike circuit switching, where a dedicated path is established, datagram switching sends packets independently, with no need for a dedicated connection.
Dynamic Routing: Packets are routed dynamically based on the network’s state. Routers in the network decide on-the-fly the best route for each packet.
Independent Packets: Each packet is treated as an independent entity. It contains all the necessary information, such as the destination address, to be delivered correctly.
Resilience and Flexibility: If one route fails due to congestion or malfunction, packets can be re-routed through alternative paths.
No Sequencing: Packets may arrive at the destination out of order and must be reassembled.
Connectionless Communication: Datagram switching is connectionless, meaning there is no need to establish a connection before sending data, as each packet is routed independently.
Advantages N DISof Datagram Switching:
Advantages of Datagram Switching:
Efficient Use of Resources: Since packets can use any available path, network resources are utilized more efficiently, reducing the likelihood of congestion.
Fault Tolerance: Datagram switching allows packets to be rerouted in case of network failures or bottlenecks, making the network more resilient.
Disadvantages of Datagram Switching:
Out-of-Order Delivery: Since packets may take different paths, they might arrive at the destination in the wrong order, requiring reassembly.
Variable Delays: Different routes may result in different travel times for packets, leading to unpredictable delays.
OSI (Open Systems Interconnection) model
a conceptual framework that standardizes the functions of a telecommunication or computing system into seven distinct layers. It helps in understanding and designing a network architecture that is flexible, robust, and interoperable.
The Seven Layers of the OSI Model:
Physical Layer (Layer 1):
Function: Deals with the physical connection between devices and the transmission of raw data (bits) over a medium like cables, radio waves, or fiber optics.
Key Tasks:
Bit transmission (0s and 1s).
Physical connections (cables, hubs).
Defines the electrical, mechanical, and procedural aspects of the communication.
Data Link Layer (Layer 2):
Function: Provides node-to-node data transfer and handles error detection and correction from the physical layer. This layer structures data into frames for transmission.
Key Tasks:
Framing: Organizes data into frames.
MAC (Media Access Control): Controls how devices on the network gain access to the medium.
Error detection and correction.
Network Layer (Layer 3):
Function: Manages packet forwarding, including routing through different routers, to ensure the data reaches its destination across multiple networks.
Key Tasks:
Logical addressing (IP addresses).
Routing: Determines the best path for data packets.
Fragmentation: Breaks down large packets into smaller ones if necessary.
Transport Layer (Layer 4):
Function: Ensures complete data transfer and manages flow control, error correction, and retransmission of lost packets. This layer provides end-to-end communication.
Key Tasks:
Segmentation and reassembly of data.
Flow control: Prevents data overflow.
Error detection and correction.
Connection-oriented communication (e.g., TCP) or connectionless communication (e.g., UDP).
Session Layer (Layer 5):
Function: Manages sessions (connections) between applications, handling the setup, management, and termination of these connections.
Key Tasks:
Establishing, maintaining, and terminating sessions.
Synchronization: Adds checkpoints in the data stream to recover in case of errors.
Dialog control: Manages two-way communication.
Presentation Layer (Layer 6):
Function: Translates data between the application layer and the network, ensuring that data is in a usable format for both layers. It handles data encryption, compression, and translation.
Key Tasks:
Data translation: Converts data formats (e.g., ASCII to EBCDIC).
Encryption/Decryption.
Data compression and decompression.
Application Layer (Layer 7):
Function: The closest layer to the end-user, this layer interacts with software applications to provide communication between applications over the network.
Key Tasks:
Provides network services like file transfers, emails, remote login.
Protocols such as HTTP, FTP, SMTP, DNS operate at this layer.
TCP/IP Protocol Suite
Introduction
The TCP/IP (Transmission Control Protocol/Internet Protocol) protocol suite is a set of communication protocols used to interconnect network devices on the internet and similar networks. It was developed by the United States Department of Defense to facilitate reliable communication over diverse networks. The suite is based on a four-layer model, which consists of the Application, Transport, Internet, and Network Access layers.
TCP/IP Protocol Suite LAYER
Layers of the TCP/IP Protocol Suite
Application Layer
Function: The top layer of the TCP/IP model, responsible for providing network services directly to user applications. It facilitates communication between software applications and lower layers of the protocol stack.
Protocols: Includes HTTP (Hypertext Transfer Protocol), FTP (File Transfer Protocol), SMTP (Simple Mail Transfer Protocol), and DNS (Domain Name System).
Example: A web browser using HTTP to request a web page from a server.
Transport Layer
Function: Responsible for end-to-end communication and data integrity. It ensures complete data transfer and provides error recovery and flow control.
Protocols:
TCP (Transmission Control Protocol): Connection-oriented protocol that ensures reliable transmission of data, providing error-checking and correction.
UDP (User Datagram Protocol): Connectionless protocol that is faster but does not guarantee reliability or data order.
Example: TCP establishes a connection before data transfer and ensures that packets are delivered without errors.
Internet Layer
Function: Manages the logical addressing and routing of data packets across different networks. It determines the best path for data to travel from the source to the destination.
Protocols: Primarily uses IP (Internet Protocol), which provides addressing information and packet routing. Other protocols include ICMP (Internet Control Message Protocol) for error reporting and routing diagnostics.
Example: IP addressing allows devices on different networks to communicate with each other.
Network Access Layer
Function: Also known as the Link Layer, it defines the protocols for data transmission over physical network connections. It is responsible for framing, addressing, and error detection on the local network.
Protocols: Includes Ethernet, Wi-Fi (IEEE 802.11), and PPP (Point-to-Point Protocol).
Addressing in the TCP/IP Protocol Suite
In the TCP/IP protocol suite, addressing is a critical aspect that enables communication across networks. Different types of addresses are used at different layers to ensure that data can move from one device to another. The four primary types of addresses are physical address, logical address, port address, and specific address.
- Physical Address (Link Layer Address or MAC Address)
The physical address is used at the Data Link Layer and is also called the MAC (Media Access Control) address.
It is a unique identifier assigned to the network interface card (NIC) of a device and is used to deliver data frames within the same local network.
Physical addresses are generally used in Ethernet and Wi-Fi networks. - Logical Address (IP Address)
The logical address is used at the Network Layer and is better known as the IP address.
The IP address uniquely identifies each device connected to the network. It is used for routing packets from source to destination across different networks.
There are two versions of IP addresses:
IPv4: A 32-bit address.
IPv6: A 128-bit address. - Port Address
The port address is used at the Transport Layer and identifies specific processes or services running on a device.
For example, HTTP typically uses port 80, while FTP uses port 21.
A combination of an IP address and a port address is called a socket, which enables communication between a specific process on one device and a specific process on another device. - Specific Address
Specific addresses are user-friendly names, such as domain names (e.g., www.example.com), that map to IP addresses using the Domain Name System (DNS).
DNS is used at the Application Layer to translate these human-readable names into the IP addresses needed for routing.
