Network Switches Buying Guide
All about the network switches
Network switches - or switches - connect network segments, ensuring full duplex communication, good traffic performance and efficient use of bandwidth.
Today, networks are essential for supporting business activity, ensuring communication, providing entertainment, and more. But none of this would be possible without a fundamental element common to all networks that connects devices to share resources: the network switch.
What is a network switch?
A network switch is a piece of equipment that operates at Layer 2, which is the second Data Link Layer among the seven layers of the OSI (Open Systems Interconnection) model. It receives the packets sent by devices connected to its physical ports and sends them again through the ports that lead to the devices that the packets are supposed to reach. Switches are a common component of Ethernet, Fiber Channel, Asynchronous Transfer Mode (ATM), and InfiniBand networks, among others. However, most switches today generally use Ethernet.
How does a network switch work?
After a device is connected to a switch, the switch notes its Media Access Control (MAC) address, also called a physical address. It is a code embedded in the network interface card (NIC) of the device itself connected to the switch via an Ethernet cable. The switch uses the MAC address to identify the connected device from which outgoing packets are sent and where incoming packets are delivered. The MAC address therefore identifies the physical device as opposed to the network layer IP address (Layer 3), which can be dynamically assigned to a device and change over time. When a device sends a packet to another device, that device enters the switch, and the switch reads its header to determine what to do with the data packet. It matches the destination address or addresses and sends the packet through the appropriate ports that lead to the destination devices.
To reduce the risk of collision between network traffic entering and leaving a switch and a connected device at the same time, most switches offer full duplex functionality which enables packets coming from and to a device from having access to the entire bandwidth of the switch connection. (Just like the difference between two people talking on a cell phone versus what happens with a walkie talkie). While it is true that most switches operate at the Layer 2 level, some can also operate at the Layer 3 level. These are called Layer 3 switches and they offer additional functionality including features of virtual local area network (vLAN) configurations.
Differences between switches and hubs
A hub can also connect multiple devices together in order to share resources. The set of devices connected to a hub is referred to as a LAN segment. The main difference between a hub and a switch is where the packets sent by any of the connected devices are broadcasted. In case of hubs, the packets sent by any of the connected devices are broadcast to all devices connected to the hub. On the other side, switches direct packets only to the port that leads to the device to which they are addressed. Switches are typically used to connect LAN network segments, to which hubs connect. The switches filter traffic destined for devices on the same LAN segment. With this intelligence, switches use their own processing resources more efficiently, but also optimize the use of network bandwidth.
Differences between switches and routers
Switches are sometimes confused with routers. Routers also allow the transfer and routing of network traffic, hence their name. But their purpose is not the same and they operate on a different level. This is because routers operate at Layer 3 - the network layer - and are used to connect networks to other networks. The nature of the network - LAN or WAN - makes it easy to differentiate switches from routers. Locally, the devices are connected by switches. In WAN wide mode, however, networks are connected to other networks by routers. The route that a data packet can take to reach the Internet - for example: device> hub> switch> router> Internet - also helps distinguish them.
Of course, there are cases where the switching functionality is built into the hardware of the router, and the router also acts as a switch. The most common and simplest example is the home wireless router. It connects to a broadband connection through its WAN port, but it usually has additional Ethernet ports that one can use to connect an Ethernet cable to a computer, television, printer, or even a game console. If other network devices, for example other laptops and phones connect through the WiFi router, it still offers switching functions through the LAN. The router is therefore also a switch. And you can even connect a switch separate from the router to allow other devices to access both the Internet and the local network.
The different types of switches
The size of the switches will vary depending on the number of devices to be connected in a given area, as well as the type of network speed and bandwidth required for those devices. For a small office or home office, a four- or eight-port switch is usually sufficient, but for larger deployments there are switches that can have up to 128 ports. A small switch can easily find its place in an office, but larger switches can be rack mounted and placed in a cabinet, data center, or server farm. Rack switch sizes can range from 1U to 4U, but larger sizes are also available. There are also speed differences between the switches. There are Fast Ethernet (10/100 Mbps), Gigabit Ethernet (10/100/1000 Mb / s), 2.5 Gigabits (2500 Mb / s) 10 Gigabits (10/100/1000/10000 Mb / s) switches and even 40/100 Gb / s. The speed depends on the throughput required for the supported tasks.
The switches also differ in capabilities. Here are three typical categories:
- Unmanaged switches
Unmanaged switches are the most basic and you cannot change their configuration. In general, they are "plug-and-play", meaning that they offer few or no options to the user. Often, they are provided with default settings for features such as quality of service, but they cannot be changed. The advantage of unmanaged switches is that they are relatively inexpensive, but their lack of functionality makes them unsuitable for most business uses.
- Managed switches
Managed switches provide more functionality and features to IT professionals and are the most popular in enterprises. Managed switches are equipped with command line interfaces (CLI), allowing their configurations to be changed. They support simple Network Management Protocol (SNMP) agents that provide information that can be used to troubleshoot network problems. They can also support VLANs vLANs, QoS settings, and IP routing. Security is also better, and they can protect all types of traffic they handle. Because of their advanced features, managed switches cost significantly more than unmanaged switches.
- Smart Switches
Smart switches are simplified managed switches that offer more functionality than unmanaged switches, but less functionality than managed switches. They are therefore more sophisticated than unmanaged switches, but they are less expensive than fully managed switches. Typically, they do not support telnet access and have Web GUIs rather than command line interfaces (CLIs). Other options, such as vLANs, may not have as many features as those supported by fully managed switches. But because they are less expensive, they can be used on smaller networks, in businesses with fewer financial resources, or with lower feature requirements.
The list of features and functionality of a network switch varies depending on the switch manufacturer and the software included, but in general, a switch allows professionals to:
- activate and deactivate specific ports;
- configure the duplex parameters (half or full), and the bandwidth width;
- define quality of service (QoS) levels for a specific port;
- activate MAC filtering and other access control functions;
- configure SNMP monitoring of devices, including link health status;
- configure port mirroring, for monitoring network traffic.
In larger networks, switches are often used to offload traffic for analysis. This feature can be important for security, since a switch can be placed in front of a WAN router, before traffic is transmitted to the local network. This can make it easier to detect intrusions, analyse performance, and set up firewalls. Quite often, port mirroring is used to mirror the data flowing through the switch before it is sent to an intrusion detection system or packet sniffer, for example. However, the basic job of a network switch is to quickly and efficiently deliver packets from Computer A to Computer B, whether the computers are across the hall or across the world. Of course, several other devices contribute to the transmission of data, but the switch is an essential part of the network architecture.