What is a Network Switch?
A network switch is the basic component of a Local Area Network (LAN) that enables one to connect various network devices together and exchange data/information between them. A network switch generally has multiple ports where network devices like computers, printers, servers, etc. could connect using cat5E/cat6 cables/ RJ-45 jacks. Multiple switches can connect to each other as well. All the computers/network devices that connect to a switch (or connect to other switches connected to this switch) can communicate and exchange data with each other, as long as they are all in the same network segment.
With a computer network (formed using network switches), one can copy a file from one computer to another or one can connect a printer/server/NAS box and share it with all the computers connected to the network. Of course, there are many more applications.
In this article, let us look at some basic information on what is a network switch. Since this is intended to be a basic guide on network switches, the features and functionalities dealt below are mostly applicable to simple unmanaged switches used at homes/small businesses. But there are links to other articles dealing with advanced concepts pertaining to enterprise switches.
Switch ports: Common switch models have 5 ports, 8 ports, 12 ports, 16 ports, 24 ports and 48 ports. Some network switches are available in other port configurations as well. When a switch is said to have five ports, it means that one can connect five network devices to it. For example, it is possible to connect four computers and one broadband router/modem to a five port switch. That way, Internet from a broadband router can be shared with the four connected computers.
Media – Copper/Fiber: A five port network switch generally means that there are five copper ports that enable one to connect computers, printers and other network devices using copper cables. Copper cables refer to Cat5E/Cat6 Unshielded Twisted Pair cables. One can also connect optical fiber cables, but they are generally not used to connect endpoint devices. Instead, the optical fiber cables connect a switch to other switches (like distribution/core switches) in order to create high speed and reliable network backbone connections (up-links). While copper cables can be used for connections up to 100 meters, optical fiber cables can be used for connections up to a few kilo-meters. Click here to know about other passive components that are used to create a network.
Bandwidth: Each switch port provides a certain maximum bandwidth (throughput) to the network device connecting to it. Generally, switch ports either support 10/100 Mbps or 10/100/1000 Mbps (Gigabit switches). Network switches support auto-negotiation, where each switch port negotiates with the network interface card of the network device (like a computer) on the best speed it can connect to (10, 100 or 1000 Mbps) and connect to them using that speed.
Switch fabric speed: Every network switch supports certain maximum throughput between its various backbone modules. This is called as the switch fabric speed. If the switch fabric speed exceeds the sum of maximum bandwidth supported by each port, then it is said to have a non-blocking configuration. Otherwise, it is said to have a blocking configuration. Switches generally run at less than 50% of their port capacity and hence a blocking configuration might be sufficient for simple applications. But switches that need to connect high speed equipments (like storage appliances, servers) or need to support high speed applications (like heavy graphics/video transmission) in all its ports might do better with a non-blocking configuration.
Types of Network Switches:
- Unmanaged/Smart/Managed Switches: An unmanaged switch is a very simple switch that cannot be managed. It generally has a plug and play configuration. One can connect the power supply, connect network devices and expect the unmanaged switch to work, without any configurations, etc. They are used at homes/small businesses. Smart switches support a few management functionalities like web-based management console, VLAN, jumbo frame support, cable length/status monitoring, etc. They are slightly more expensive than unmanaged switches and can be used at home and SMB’s. Manageable switches have many more management features and are generally used in companies/enterprises. They are more expensive than smart switches.
- Layer-2/Layer-3 Switches: Layer-2 Switches operate in the data link layer and they can just transmit data/information from one switch port to any other connected switch port in the same network. A Layer-3 switch can provide some functions of a router and can transmit data/information not only between switch ports in the same network, but also between switch ports belonging to different networks. You can read more about Layer-3 switches from here.
- POE/Non-POE Switches: Power Over Ethernet (POE) is a technology that enables switch ports to transmit electrical power along with data, using a single cat5e/cat6 cable. POE switches can power up POE supported network devices like IP phones, access points, IP cameras, etc. and hence there is no need for a separate AC power supply/power adapter for these devices. POE switches are generally expensive, when compared to normal switches.
- Stand-alone/Chassis based Switches: Most of the low end switches/edge switches that connect to computers and other network devices are stand-alone switches having a fixed configuration. The number of ports provided by these switches are fixed and they are less expensive. Chassis based switches are used at network core/distribution layers. These switches contain empty slots which can be populated by fiber port modules/copper port modules of different configurations and hence they are expandable. There are many more advantages of chassis-based switches, which you can read from here. However, there are some stand-alone switches that support a stackable configuration, providing limited expansion capabilities to stand-alone switches.
- Copper/Fiber Switches: Copper Switches have copper ports (to connect to computers, printers and other end point network devices). But some of them may have a few expansion ports (SFP slots) that can connect to optical fiber cables using appropriate fiber modules. These OFC cables are used mostly for connecting to other network switches, creating the network backbone. There are fiber switches that have all-fiber ports, with a few (optional) copper ports. These fiber switches are generally kept at the center of the network (distribution/core layers) in order to connect to various edge switches using optical fiber cables.
- Desktop/Wall-mount/Rack-mountable Switches: Many entry level switches either need to be kept on the desk or need to be mounted on a wall (using a wall mount kit). But the best option is to buy rack-mountable switches that come in standard 19″ rack-mountable form factor. Network Racks provide a safe enclosure where switches (and other network devices) are arranged neatly and the total available space is utilized efficiently.
LED indicators: Many network switches have switch level LED lights and port level LED lights that allow the administrator to monitor certain aspects of the switch/individual ports. For example, one can know if a switch port is functioning and the speed at which each port is connecting to the network devices by looking at the color of LED lights in each port.
Network devices that can be connected to a switch: Computers, laptops, printers, servers, other network switches, IP phones, access points, video conferencing equipments, IP surveillance cameras, IP PBX, NAS storage appliances, Wired/wireless Routers, broadband/cable modems, IPTV, media players, gaming stations, music systems, video streaming equipments, etc.
Interconnecting Network Switches: It is possible to connect a cat6 cable between one port of a network switch and another port of another network switch to interconnect both of them. But the interconnect bandwidth in this case is restricted to the maximum bandwidth supported by either of the two ports. Some network switches offer expansion ports that support switch interconnections over higher bandwidths. For example, a switch with twenty-four 10/100 Mbps ports might provide two 10/100/1000 Mbps (gigabit) ports for connecting to other switches.
It is also possible to connect two switches using optical fiber cables if the switch has SFP slots and supports fiber modules/fiber cable connectivity. Fiber cables support higher bandwidth – One can create a 10 GE (Ten gigabit ethernet) backbone for a switch that supports all gigabit ports using fiber cables (for example).
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