What is a switch

I. Introduction

A network switch is a networking device that connects multiple computers or other devices together on a network. It is a device that allows data to be transmitted between multiple devices on the network. Switches have multiple ports, typically Ethernet ports, which allow multiple devices to be connected to the switch.  Switches use packet switching, which involves dividing data into packets and sending them individually over the network[1].  Switches learn the MAC addresses of the devices connected to each port and maintain a MAC address table. This table is used to forward data frames to the correct destination port.  Switches can provide port isolation, which means that data traffic on one port is isolated from traffic on other ports. This can be useful for security purposes or to prevent broadcast storms.  Switches can be used to create virtual LANs (VLANs), which are logical segments of a network that can be used to separate traffic and improve security.  Switches can provide traffic management features such as quality of service (QoS) and load balancing, which can be used to prioritize traffic and optimize network performance.

A network switch serves as a central connection point for various devices on a network, such as computers, printers, servers, and other networking equipment.  Each device connects to the switch through a network cable, typically an Ethernet cable.  The switch provides multiple ports, enabling multiple devices to be connected simultaneously.

II. Difference between switch and hub

A network switch and a network hub are both networking devices that connect multiple computers or other devices together. People interchange the terms sometimes because of the similarities.  There are some key differences between the two. 

Data Forwarding:

A switch uses MAC (Media Access Control) addresses to forward data frames to the appropriate destination port[2]. It maintains a MAC address table to identify the ports where specific devices are connected. When a data frame arrives at a port, the switch looks up the destination MAC address in the table and forwards the frame to the corresponding port.  A hub, on the other hand, operates at a lower level of the networking model and does not use MAC addresses for data forwarding. Instead, it simply broadcasts all data frames received on one port to all other ports connected to it.

Collision Domain: 

Switches create separate collision domains for each port. This means that collisions only occur between devices connected to the same port. Collisions can lead to data loss and network performance issues. By creating separate collision domains, switches help to minimize collisions and improve network performance.  In contrast, a hub creates a single collision domain for all devices connected to it. This means that collisions can occur between any two devices connected to the hub, regardless of which port they are connected to.

Performance:

Switches provide higher performance than hubs because they can forward data frames more efficiently. By creating separate collision domains and using MAC address tables, switches can reduce collisions and improve network throughput.  Hubs, on the other hand, have lower performance due to the fact that they broadcast all data frames to all ports, regardless of the destination. This can lead to a significant performance degradation in busy networks.

Scalability:

Switches are more scalable than hubs because they can support a larger number of devices. Switches can be stacked or interconnected to create a larger network, allowing for more devices to be connected.  Hubs have limited scalability, as they can only support a limited number of devices before performance starts to degrade.

Security:

Switches provide better security than hubs because they can be configured to restrict traffic between specific ports. This can be useful for isolating sensitive devices or creating separate networks for different departments.  Hubs provide no security features, as they simply broadcast all data frames to all ports. This makes it easy for unauthorized users to gain access to network traffic.

III. Difference between switch and router

Network switches and routers play distinct roles in data communication. Network switches operate at layer 2 (data link layer) of the OSI model[3], where the primary focus is on transmitting data frames between devices within the same network segment. Switches use MAC addresses to identify and forward data frames directly to the intended recipient on the same network.  Routers, on the other hand, operate at layer 3 (network layer) of the OSI model. They are responsible for routing data packets between different networks or subnets. Routers use IP addresses to determine the best path for data packets to reach their destination, even if it involves crossing multiple networks.

Primary Function:

Network switches are primarily used to connect devices within the same network segment. They provide a central point for connecting multiple devices and facilitating communication between them. Switches ensure that data frames are forwarded to the correct destination within the same subnet or broadcast domain.  Routers, in contrast, are designed to connect different networks or subnets. They act as gateways between networks, allowing devices on different subnets to communicate with each other and access the internet. Routers determine the best path for data packets to reach their intended destination and forward them accordingly.

Data Forwarding:

Network switches use MAC addresses to forward data frames. When a device sends a data frame, the switch reads the destination MAC address and forwards the frame to the corresponding port connected to the destination device. This process is known as MAC address learning and forwarding.  Routers use IP addresses to route data packets. When a router receives a data packet, it examines the destination IP address and consults its routing table to determine the best path for the packet to reach its destination. The router then forwards the packet to the appropriate interface or next-hop router.

Broadcast Domains:

Network switches create separate broadcast domains for each port. This means that broadcasts sent by a device on one port will only be received by devices connected to the same port. Broadcasts do not cross switch ports and are contained within each broadcast domain.  Routers connect different broadcast domains and allow communication between devices on different subnets. When a broadcast is sent on a network, the router forwards it to all of its connected subnets, allowing devices on different subnets to receive the broadcast.

Routing Table:

Network switches do not maintain a routing table[4]. They rely on MAC address learning and forwarding to deliver data frames within the same network segment.  Routers, however, maintain a routing table that contains information about different networks and the best paths to reach them. The routing table is used to make routing decisions and determine the next hop for data packets.

Default Gateway:

Network switches do not act as a default gateway for devices connected to them. Devices on a network must configure their default gateway as the IP address of a router to access other networks and the internet.  Routers serve as the default gateway for devices on their network. When a device sends a data packet to a destination outside its subnet, the router acts as the gateway and forwards the packet to the appropriate next hop.

Security:

Network switches may provide basic security features such as port security and VLANs. Port security limits the number of MAC addresses allowed on a port, and VLANs allow for the segmentation of a network into multiple logical subnets.Routers offer more advanced security features, including access control lists (ACLs), firewalls,   and encryption. ACLs define rules for permitting or denying traffic based on source and destination IP addresses, port numbers, and other criteria. Firewalls protect networks from unauthorized access, and encryption ensures the privacy and integrity of data in transit.

Different uses:

Network switches are commonly used in small offices, homes, and small businesses. They connect devices such as computers, printers, and servers within the same network  Network switches are suitable for small to medium-sized networks. They provide efficient connectivity within a single network segment and can handle a limited number of devices.  Routers are more scalable and are used in large and complex networks. They can connect multiple networks, subnets, and remote locations, and handle a significant volume of traffic.

IV. Types of Network Switches

Unmanaged switch:

An unmanaged switch is a type of network switch that operates with a fixed configuration and does not offer advanced management features. It is designed to be plug-and-play, requiring minimal setup or maintenance. Unmanaged switches are commonly used in small networks, such as home networks or small businesses, where simplicity and affordability are important.  Unmanaged switches come with a pre-configured set of features and settings, and they do not allow users to modify these settings. This makes them easy to use, as there is no need for complex configuration.  Unmanaged switches typically provide basic switching functionality, such as connecting multiple devices to a network and forwarding data packets between them. They do not offer advanced features such as VLANs, QoS, or port security.   Unmanaged switches are designed to be easy to install and use. They can be simply connected to other network devices, such as computers or routers, and will start functioning immediately without the need for any configuration.  Unmanaged switches are generally more affordable than managed switches, making them a cost-effective option for small networks.

Managed switch:

A managed switch is a type of network switch that offers advanced configuration options and management features. Unlike unmanaged switches, which operate with a fixed configuration, managed switches allow network administrators to customize and control various aspects of the switch's operation. Managed switches allow administrators to create virtual LANs (VLANs), which logically segment the network into multiple isolated domains. This is useful for security, traffic management, and network organization.  Managed switches provide Quality of Service (QoS) features that enable administrators to prioritize certain types of network traffic, such as VoIP or video conferencing, to ensure consistent performance and reduce latency.  Managed switches offer port security features that allow administrators to restrict access to specific ports and limit the number of MAC addresses that can be learned on a port. This helps to prevent unauthorized devices from accessing the network and enhances security.  Managed switches support Simple Network Management Protocol (SNMP), which allows administrators to remotely monitor and manage the switch using network management software.  Managed switches typically provide a command-line interface (CLI) that allows administrators to configure and manage the switch through text-based commands.

Layer 3 Switch:

A layer 3 switch is a networking device that operates at layer 3 of the OSI model and can perform routing functions in addition to switching. It is a more advanced type of switch that can be used to create and manage virtual LANs (VLANs) and to route traffic between different VLANs and subnets[5]. Layer 3 switches are typically used in larger networks where high performance and scalability are required.

Layer 3 switches can route traffic between different VLANs and subnets, which allows for more efficient and secure network traffic management.   Layer 3 switches can create and manage VLANs, which are logical segments of a network that can be used to isolate different types of traffic or to create separate networks for different departments or users.  Layer 3 switches can provide QoS features that allow network administrators to prioritize certain types of traffic, such as VoIP or video conferencing, to ensure consistent performance and reduce latency.   Layer 3 switches can be stacked together to create a single, larger switch, which can be useful for scaling up a network or for creating a redundant network.  Layer 3 switches can provide security features such as access control lists (ACLs) and port security, which can be used to protect the network from unauthorized access and attacks.

Layer 3 switches are a valuable tool for managing and securing larger networks. They provide a number of advanced features and benefits that can help to improve network performance, security, and scalability.

Stackable switches: 

Stackable switches are a type of network switch that can be connected together to create a single, larger switch. This allows for greater scalability and redundancy in a network. Stackable switches are typically used in large enterprise networks where high performance and reliability are required.

Stackable switches can be easily scaled up by adding additional switches to the stack. This allows for a network to grow without having to replace the entire switching infrastructure.  Stackable switches can be configured to provide redundancy, which means that if one switch fails, the other switches in the stack will continue to operate and provide connectivity to the network.  Stackable switches can provide high performance by aggregating the bandwidth of multiple switches into a single logical switch. This can improve network performance and reduce latency.   Stackable switches can be managed as a single unit, which simplifies network management and administration.

PoE switches: 

A Power over Ethernet (PoE) switch, often known as a PoE switch, is a network switch that combines data connectivity and power delivery over a single Ethernet cable[6]. It is a practical and efficient solution for powering devices such as IP phones, wireless access points, security cameras, and other network-connected devices that require both data and power. Here's an elaboration and expansion of the input text:

PoE utilizes a standard Ethernet cable to carry both data and electrical power, eliminating the need for separate power cables.  It operates by transmitting electrical current on the unused pairs of the Ethernet cable, which are typically the spare pairs (pins 4 and 5 and pins 7 and 8).  PoE switches typically provide 48 volts of power to connected devices, which is sufficient for most PoE-powered devices.  Some PoE switches offer higher power levels, such as 56 volts or even 95 volts, to support devices with higher power requirements, such as PTZ cameras or video conferencing systems.

PoE switches are available in various sizes and configurations.  Small desktop switches with a few PoE ports for home or small office use.  Medium-sized switches with dozens of PoE ports for mid-sized businesses.  Large enterprise-grade switches with hundreds of PoE ports for large organizations and data centers.  Ruggedized PoE switches designed for outdoor use in harsh environments.        

PoE switches are widely used in various environments.  They can power IP phones, wireless access points, security cameras, and other network devices.  PoE can provide power and connectivity to laptops, and tablets.  PoE is useful in powering medical devices, such as patient monitors and bedside terminals.  PoE can be used in connecting and powering sensors, actuators, and other industrial IoT devices. PoE can power surveillance cameras and passenger information systems in trains, buses, and other vehicles.

PoE eliminates the need for separate power cables, reducing installation time and complexity.  PoE reduces the cost of purchasing and deploying separate power supplies and eliminates the need for additional electrical outlets.  PoE switches allow for easy expansion and scalability of network devices without the need for additional power outlets.  PoE switches provide a continuous power supply to connected devices, reducing the risk of power outages and data loss.

V. Conclusion

Network switches play a crucial role in modern networks by facilitating efficient data transmission, improving network performance, and enhancing security and reliability.  Network switches operate between routers and hubs in terms of functionality. Routers work at layer 3 of the OSI model and route traffic between networks, while hubs operate at layer 1 and forward data packets to all connected devices. Network switches combine the functionality of both hubs and routers, operating at layer 2 and forwarding data packets in an intelligent way using a MAC address table. Switches offer advanced features like VLANs, port security, and QoS, providing granular control over network traffic.

While switches share some similarities with hubs in their ability to connect multiple devices within a single network segment, their capabilities extend far beyond simple connectivity. Network switches employ switching functions, which enable them to forward data packets to specific devices based on their Media Access Control (MAC) addresses.  This advanced functionality sets network switches apart from hubs and makes them indispensable in modern networking infrastructures. Network switches allow for more efficient and granular control over data traffic, enabling organizations to create high-performance networks that can handle large volumes of data and support a wide range of applications.

In a typical network environment, hubs may be utilized to connect devices within a limited area, such as a single floor or a small office. Network switches are then employed to interconnect multiple hubs, creating a larger and more scalable network infrastructure. Routers are strategically positioned at the boundaries of networks, connecting them to the outside world, such as the Internet, and facilitating communication between different organizations or remote locations.  The interplay of hubs, network switches, and routers enables the seamless flow of data across diverse network environments, ensuring reliable and efficient communication for businesses and organizations of all sizes.

VI. References

1 What is a network switch and how does it work?, https://www.networkworld.com/article/969239/what-is-a-network-switch-and-how-does-it-work.html

2 MAC address,  https://www.techtarget.com/searchnetworking/definition/MAC-address

3 OSI model, https://www.techtarget.com/searchnetworking/definition/OSI

4 Routing Tables in Computer Network, https://www.geeksforgeeks.org/routing-tables-in-computer-network/

5 What is a Layer 3 Switch And Why Would Your Network Need It?, https://techgenix.com/layer-3-switch/

6 A Beginner’s Guide to Understanding PoE Switches,  https://www.iptechview.com/beginners-guide-understanding-poe-switches