Umm Al-Qura University
Faculty of Public Health and Health Informatics
(computer networks assignment)
Created by
Azhar Alharbi ( 441006581) Haneen Arif Alhatimi ( 442006110 ) Reman Ahmed Razzaq ( 442000395 )
Sabaa Almasabi ( 442000150 )
Group 2
Dr. Mohamed Kamal
Introduction to network layer
The network layer, which is part of online communications, enables the connection and transfer of data packets between various devices or networks.
In the OSI Model, the network layer is positioned as the third level (Layer 3) and is responsible for establishing data routing paths to facilitate network communication. Data is transmitted in the form of packets through logical network paths in a controlled and organized manner governed by the network layer.
The network layer primarily handles tasks such as setting up logical connections, forwarding data, routing packets, and reporting delivery errors. It can support either connection-oriented or
connectionless networks, but not both simultaneously.
Network topology
Network topology refers to how the nodes and links within a network are organized and connected. It can be categorized into two types: physical network topology, which relates to the physical
transmission medium, and logical network topology, which describes how data travels between devices regardless of physical connections.
Examples of logical network topologies include twisted pair Ethernet, which follows a logical bus topology, and token ring, which follows a logical ring topology.
Physical network topology encompasses various configurations of nodes and links, such as star, mesh, tree, ring, point-to-point, circular, hybrid, and bus topologies. The choice of an ideal network topology depends on factors like the organization's size, scale, objectives, and budget.
To visualize the network's structure, a network topology diagram represents the communicating devices (nodes) and their connections (links).
There are various network topologies, including:
1. Bus Topology: In a bus topology, all devices are linked to a common communication
medium, which is often a single wire referred to as a "bus." Each device connects to the bus directly,
and data is disseminated to all devices on the network. If the bus fails, the entire network may be impacted.
2. Star Topology: A star topology connects every device on the network to a central device, such as a hub or a switch. All device communication is routed through the central device. If one device or link fails, just that connection is affected, while the remainder of the network continues to function normally.
3. Ring Topology: A ring topology connects devices in a circular loop, with each device connecting to two surrounding devices. Data moves in one way around the ring, passing through each device until it reaches its destination. The entire network may be interrupted if one device or connection fails.
4. Mesh Topology: A mesh topology connects every device on the network to every other device on the network. This design provides redundancy and many data channels, leading to great
reliability.
However, it necessitates extensive cabling and might be costly to implement.
5. Tree Topology: A tree topology, also known as a hierarchical topology, merges numerous star topologies into a larger network structure. The devices are organized hierarchically, with parent and child nodes. This topology is widely utilized in bigger networks like enterprise networks.
6. Hybrid Topology: A hybrid topology is one that combines two or more separate topologies. A network, for example, may employ a hybrid of star and mesh topologies to maximize their respective benefits.
It is crucial to note that, depending on the network requirements and equipment, these topologies can be implemented using both wired and wireless connections.
how the network layer works:
1-Packet Routing
When a device needs to send data to another device on a different network, it creates a data packet.
The network layer's job is to find the best path for packets to reach their destination, which may involve multiple routers and network segments.
2- IP address
Every device connected to the Internet is assigned a unique IP address. The network layer uses source and destination IP addresses to route packets to their destinations by including these IP addresses in the packet header.
3- Subnetting
The network layer also handles subnetting, the process of dividing an IP network into smaller subnets. This practice promotes efficient use of IP addresses and improves network management.
4- Routing protocol
Network routers use routing protocols such as RIP, OSPF, and BGP to exchange network topology information and select the best route for data packets. These protocols allow routers to create routing tables based on this information.
5-Packet forwarding
After determining the packet's next hop, the router forwards it to the appropriate interface or port.
The decision depends on the destination IP address and routing table data.
6- Fragmentation and Reassembly
The network layer may also be responsible for breaking large packets into smaller fragments on the sender side and reassembling them on the receiver side as needed for transmission across network segments.
7- TTL (Time to Live)
The network layer has a time-to-live (TTL) field in the packet header that decreases with each hop.
When the TTL reaches zero, the packet is dropped. TTL prevents packets from looping indefinitely in routing loop situations.
Network layer design issues:
The network layer introduces some design issues, which are described below:
1. Save and forward packet exchange:
The host sends the packet to the nearest router. The package will be stored there until it arrives complete. Once the connection is fully processed by checking the checksum, it is forwarded to the next router until it reaches its destination. This mechanism is called "store and forward packet switching".
2. Services provided for the transport layer:
The network layer delivers its services to the transport layer through the network/transport layer interface. These services are described below.
However, before providing these services to the transport layer, the following goals must be considered:
The provision of the Service must not rely on router technology.
The transport layer must be protected from the type, number, and topology of available routers.
Transport layer network addresses should also use a consistent numbering pattern for LAN and WAN connections.
Depending on the connection, two types of services are provided:
Connectionless – Routing and insertion of packets into subnets is done individually. No additional setup is required.
Connection-oriented – The subnet must provide reliable service, and all packets must travel through a single route.
3. Implementation of connectionless services:
The data packet is called a "datagram", and the corresponding subnet is called a "datagram subnet". If the size of the message to be transmitted is four times the size of the packet, the network layer will split it into four packets and transmit each packet to the router. Some agreements. Each packet has a destination address and is routed independently regardless of packet.
4. Implementation of Connection-Oriented Service:
When utilizing a connection-oriented service, the process begins with establishing a connection, utilizing it, and subsequently releasing it. In connection-oriented services, data packets are delivered to the recipient in the exact sequence in which they were dispatched by the sender.
This can be accomplished through two methods:
- Circuit Switched Connection: This method establishes a dedicated physical pathway or circuit between the communicating nodes before transferring the data stream.
- Virtual Circuit Switched Connection: Here, the data stream is conveyed over a packet switched network in a manner that creates the illusion of a dedicated path from the sender to the receiver. A virtual path is created, even though other connections may also share this pathway.
How does the network layer move in the OSI model?
The network layer in the OSI (Open Systems Interconnection) paradigm oversees logical addressing and data routing between various networks. It makes ensuring that data packets are successfully transmitted across numerous interconnected networks from the source host to the destination host.
The network layer, which comes after the physical layer and the data connection layer in the OSI model, is commonly regarded as the third layer in actual implementations, the network layer and internet layer operations are frequently separated into two layers. While the internet layer covers addressing and routing across multiple networks, the network layer primarily deals with addressing and routing within a single network or subnet. The OSI model's relocation of the network layer relates to the advancement and modification of networking technology over time. In contemporary networking topologies, the network layer is very intimately related to the internet layer due to the advent and broad use of the Internet Protocol (IP) as the primary protocol for internetworking. By using IP addresses, which are used at the network layer, IP provides logical addressing and permits packet routing across connected networks. To make routing easier, it turns the data received from the transport layer into IP packets and adds source and destination IP addresses. Based on the destination IP address, these IP packets are subsequently routed through routers until they reach the desired destination network.
Definition of frame and packet in network layer:
In the context of the network layer in computer networking, the terms "frame" and "packet" refer to different units of data encapsulation and transmission.
1. Frame:
A frame is a unit of data encapsulation at the data link layer of the OSI model or the network access layer of the TCP/IP model. It represents a structured format of data that includes the physical (MAC) addresses of the source and destination devices, error detection or correction codes, and the actual payload (data) being transmitted.
2. Packet:
A packet, on the other hand, is a unit of data encapsulation at the network layer of the OSI model or the internet layer of the TCP/IP model. It represents a logical grouping of data that includes the network layer header, payload (data), and sometimes a trailer for error detection.
In summary, frames are used for communication within a local network or subnet at the data link layer, whereas packets are used for communication between networks at the network layer. Frames contain physical (MAC) addresses, while packets contain logical (IP) addresses. Both frames and packets play crucial roles in the layered networking models to ensure reliable and efficient data transmission.
How are frames and packets used to transmit data over a network?
Applications like web browsers generate data which needs to be transmitted over networks.
- The transport layer (TCP/UDP) segments the data into smaller parts called segments.
- Segments are encapsulated by the internet layer (IP) with IP headers containing source/destination addresses and routing info, forming IP packets.
- IP packets are too large for physical networks, so the data link layer adds headers/trailers to form frames with source/destination MAC addresses for local routing.
- Frames travel locally on networks like Ethernet via switches based on MAC addressing.
- To route beyond a local network, frames reach routers which remove frame headers, see IP packets, and encapsulate in new frame headers to next hop router/switch.
- This process of removing and adding frame headers at each router continues hop-by-hop until packets reach their final local network destination.
- There, frames are processed, IP headers removed, and data reassembled to complete end-to end transmission between applications across networks.
The key differences between IPv4 and IPv6
IPv4 and IPv6 are different versions of the Internet protocols used to manage communication and identification of devices on networks such as the Internet.
Introduced in 1983, IPv4 (internet protocol version 4) uses 32-bit addresses and provides approximately 4 billion unique addresses. Its limited address space is almost exhausted.
IPv6 and IPv4 differ in five significant areas: addressing and routing, security, network address translation, administrative workload, and support for mobile devices. Additionally, IPv6 encompasses a crucial aspect, which involves a range of potential migration and transition strategies from IPv4. IPv6 (Internet Protocol version 6) was developed as a successor, using 128-bit addressing and providing a significantly larger address space of approximately 340 billion addresses to accommodate future growth. It represents the address in hexadecimal format, rather than the decimal format of IPv4.
IPv6 improves upon IPv4 in several ways: It expands the address space to meet future needs. Address assignment can be static or dynamic via DHCPv6 (dynamic host Configuration protocol version 6) or automatic. It features a simplified 40-byte fixed-length header and new options such as flow labels for traffic classification.
In summary, IPv6 is intended to replace IPv4 (due to its limited number of addresses) and improve various network aspects such as addressing, headers, routing, and security to accommodate future growth in Internet-connected devices.
In conclusion, the network layer plays a crucial role in the design of computer networks. It is essential for forwarding, addressing, and routing data packets to make sure they effectively go to their intended locations. The network layer makes it possible for information to move freely across different networks and devices by leveraging IP addresses, routing protocols, and routing tables. Its tasks include regulating the effective use of IP addresses as well as packet routing and subnetting.
Additionally, it offers choices for both circuit-switched and virtual circuit-switched connections, providing versatility in data transfer techniques. In the end, the network layer serves as the
foundation for the internet and most computer networks, facilitating cross-border connectivity and information sharing.
References:
Fraihat, A. (2021). Computer networking layers based on the OSI model. Test Eng. Manag, 83, 6485- 6495.
Ali, A. N. A. (2012). Comparison study between IPV4 & IPV6. International Journal of Computer Science Issues (IJCSI), 9(3), 314.
Design issues in network layer - GeeksforGeeks. (n.d.). https://www.geeksforgeeks.org/design- issuesin-network-layer/amp/
What is Network Topology? Definition and FAQs | HEAVY.AI.
(n.d.). https://www.heavy.ai/technical-glossary/network-topology
Network hardware components
Unit 9
Reman Ahmed Azhar Alharbi prepared by :
Haneen alhatimi
Sabaa Almasabi
Hubs
Switches Bridges Routers Gateways
Network interface cards (NICs) Modems
Firewalls
Unit outline
Introduction
Network hardware is defined as a set of physical or
network devices that are essential for interaction and
communication between hardware units operational on a computer network
Reman
What’s mean of Hub
A network hub is a simple networking device that
connects multiple devices together
Active hub
Intelligent hub
Types of hubs
Passive hub
Switches
Switches are networking devices operating at layer 2 or a data link layer of the
OSI model. They connect devices in a network and use packet switching to send,
receive or forward data packets or data frames over the network.
PoE switches Managed
switches Unmanaged
switches
Types of switches
Bridges
1/preventing unnecessary traffic from crossing onto other network segments
2/isolate a busy network from a not-so-busy one
bridge connects dissimilar networks together
Advantages of Bridges:
Azhar
Transparent bridge:are invisible to other devices
on the network
1 Translational
bridge:convert the received data from
one networking system to another.
2 Source-route
bridge:developed and designed by IBM
specifically for token ring networks.
3
Azhar
router is a device that connects two or more packet-switched networks or subnetworks.
1/The router reads the header of a packet to determine its destination,
2/then reviews the routing table to find out the most efficient path to that destination.
3/then forwards the packet to the next network in the path.
Routers
Azhar
Vulnerability exploits
1
DDoS attacks
2
Administrative credentials
3
Azhar
a "gateway" typically refers to a device or software component that connects two different networks, enabling communication between them. Gateways serve as intermediaries that facilitate the exchange of
data between networks with different protocols
Gateway is located at the boundary of a network and manages all data that inflows or outflows from that network
The feature that differentiates a gateway from other network devices is that it can operate at any layer of the
OSI model ( Open Systems Interconnection)
Types of Gateways
Each type serves a specific role in facilitating data exchange and communication across diverse networks
network gateways for connecting LANs to WANs
Ex: ( Router ) Haneen
protocol gateways for translating between network protocols or
communications standards
application gateways for managing traffic at the
application layer
VoIP gateways converts voice & telepone signls between Digital and analog
formats
cloud gateways for integrating on-premises infrastructure with cloud
services
and IoT gateways for connecting and
aggregating data from IoT
devices.
Network Interface Cards
An NIC is the core piece of hardware used for networking connectivity. While traditionally associated with PCs,
laptops, and servers, NICs can exist in almost any networked device including printers, telephones, and scanners.
is essential to allow your different devices to communicate together and share informat and data for a more productive and efficient IT system
NIC provides a computer with a dedicated, full-time connection to a network
and provides a secure, faster, and more reliable connection.
NIC
Companies that manufacturer the NIC card :
This companies adds a MAC address into the NIC cards which is an Identefair that every network device uses to uniquely identify itself on a network
it’s operate at the Data Link Layer of the OSI model.
They are used to control access to the physical network medium, such as Ethernet or Wi-Fi
MAC addresses are globally unique. No two devices
should have the same MAC address
Modems
Sabaa
is a device that connects your home or office network to the internet service provider
The term "modem" was coined to describe the device that
performs these modulation and demodulation functions.
-A modem converts digital signals into an analog signal.
-The modem helps to connect the LAN (A local area network )to the internet.
-Modem performs both modulation and demodulation processes in the same time
disadvantages
-The working of the modem slows down when connected to the hub.
-When we using a modem a limited number of network devices can be connected to the internet.
-Modems have a high rock of security-related attacks.
Advantages
Advantages and disadvages
Sabaa
A firewall is a security system that protects a computer network from unauthorized access.
Firewalls
Sabaa
-Promotes Privacy and Security -Monitors Network Traffic
-Prevent Virus Attack
-Network segmentation
-Application-level filtering
advantages
Sabaa
Disadvantages
-Configuring firewalls can be complex, requiring technical expertise.
-Firewalls need powerful equipment and resources, which can be expensive to acquire and maintain.
-Firewalls can sometimes block websites or applications that you actually want to access.
-Firewalls can be bypassed or circumvented by professional attackers using advanced techniques.
Sabaa
For listening For listening
For listening
