Network Switch 101

What is a network switch? Today we introduce you to the many incarnations of this vital appliance to help you determine the right gear for your environment.

Network Switch Basics

In today’s increasingly mobile world, there has been a massive push for the propagation of wireless networking. Everyone seems to love being connected as they move about their day.

With the prevalence of wireless accessibility, people do not stop to think about what happens in the background to enable that connectivity. There is an infrastructure that must be set up, tested and maintained to allow it to remain viable and useful. Much of the time, this process can become very costly with regards to labor, equipment expense and troubleshooting. Reliability is another key factor that must also be considered. One of the solutions to create a stable network, instead of using wireless, is through the use of structured cabling and network Ethernet switches.

A network switch is a tool responsible for the connections between the systems and equipment that you wish to interact with and to share data amongst. These connections are generally created through the use of structured cabling that links both the station side (the side you interact with) and the device that you are trying to share data with, such as a server or another computer.

A network switch can be thought of as a middleman that directs traffic to its correct place. In short, if a device tries to retrieve data from another source, the switch will check to see if it knows where the destination is. If it does not know where the destination is, it will send the packets off to another device like a router and let that device determine what to do with the information. Depending on the type, layer 2 or layer 3, a switch will reside respectively on the Data Link layer or the Network layer of the OSI model.

OSI 7 Layer Model: Switches operate at Layer 2 & depending on the switch, Layer 3.OSI 7 Layer Model: Switches operate at Layer 2 & depending on the switch, Layer 3.

Layer 2 switches are some of the most common, as they tend to be less expensive and perform well. They use a device’s physical address (MAC address) from incoming message frames to determine which output port to forward the information out of. A switch is able to do this by keeping a MAC address table from ARP requests for comparing incoming frame information.

Layer 3 switches possess the same capability and behave in much the same way as a layer 2 switch; however, they also possess the ability to route between different subnets or VLANs that may exist on a local area network. This can take quite a load off of a router, leaving it to solely handle network access that is off of the LAN.

What a typical home network may look like (multiple wired connections to a switch).What a typical home network may look like (multiple wired connections to a switch).

Switches allow information to be passed along in a much more discrete and efficient way compared to network hubs. Switches enable multiple users to access network resources by creating specific pathways for information to flow between the connections without any interactions from other data packets that could potentially be on the same network segment. They effectively reduce the amount of collisions that may occur between data packets, since the switch knows where it needs to send information based on its MAC table. This is very different from a hub. A hub broadcasts data to each connected device until the correct destination is reached, which can result in data collisions as well as security issues.

How does this translate into the home and consumer side of things? An inexpensive switch can allow a person looking to create a home network to connect all of their devices together without the fear of slow data sharing caused by packet collisions, all while using the same Internet connection. They also allow for the centralization of connections within the home, making management much easier. The first step in choosing the correct switch for your home is deciding on what type you may want. Luckily, there are a few options.

What Makes a Switch?

Switches can vary greatly in the types of materials used in their construction, ranging from metal to plastic for the housing. Plastic tends to be the material of choice among lower-end models. However, companies like Netgear offer unmanaged products, such as its GS105, with metal housings. They last longer than plastic and tend to be more durable.

Interior view of a Netgear GS608 8-port 10/100/1000 Mbps SwitchInterior view of a Netgear GS608 8-port 10/100/1000 Mbps Switch

Smaller unmanaged switches tend to draw their power from wall warts. Higher-end models (like those designed to be rack mounted) usually have an in-housing power supply and only require a standard IEC power cable. As with any electronic device, switches will generate heat that must be dissipated. Many smaller switches will be passively cooled utilizing a heat sink (such as pictured above). However, larger models are normally equipped with fans to help exhaust the generated heat and prolong the life of the product.

Companies like Broadcom and Qualcomm supply a lot of the component hardware used in consumer networking products like switches, as well as other product lines ranging from routers to modems. Using this hardware, the switch knows how to handle the incoming and outgoing information. How these instruction are dealt with varies between unmanaged, smart and managed switches. For example, many unmanaged switches utilize SoC (or system on a chip) technology, where many subsystems are integrated on the same package. This SoC handles the data at the hardware level when it comes into the switch, and directs it where to go. For example, in a switch’s case, a frame would come in and be compared against a MAC table, then be directed out the appropriate network port. Higher-level switches, such as smart switches, generally contain CPUs that are integrated into a chip within the switch. This CPU can aid in handling the additional overhead of features like VLANs, QoS and Layer 3 switching.

A convenient feature added to switches is the inclusion of link lights, which are generally located near the top of the port and on either side of the port as well. The lights activate when the port detects activity from an active connection, which occurs when two products are linked together through the use of patch cables. For the most part, one activated light means that the established connection is 10/100 Mb/s, while two activated lights indicate a 1 Gb/s connection. This can be extremely useful for troubleshooting purposes. Even though link lights do not guarantee a reliable connection, they at least indicate that two devices are patched through to each other. If there are no lights, it can create a starting point for troubleshooting in that the port could potentially be bad or that the cabling between the two connected points is defective in some manner.

Apart from the physical aspects that make up a switch, there are also different features to look out for, such as jumbo frame support, duplexing, large MAC table sizes and Auto-MDIX/MDI support.

Jumbo frames are Ethernet frames that contain more than 1500 bytes, with 9000 bytes tending to be used as a conventional MTU size. Jumbo frame support can be useful for lowering bandwidth requirements, as the switch’s CPU only has to process one larger frame as opposed to being flooded with multiple smaller frames.

There are two types of duplexing you'll encounter: full and half. Most modern equipment operates in full-duplex mode. This is very important, as a device running full duplex mode is able to simultaneously send and receive data. In half-duplex mode, one device sends a frame and all devices within the collision domain listen for the frame. This has the potential to introduce collisions if collision detection fails to prevent the occurrence, which can significantly degrade the performance of your network.

Full-duplex communication allows simultaneous sending and receiving. Half-duplex can only send or receive one transmission at a time.Full-duplex communication allows simultaneous sending and receiving. Half-duplex can only send or receive one transmission at a time.

Large MAC table sizes are more of a business-oriented capability than something that'd come into play at home. Businesses need a switch with the capacity to retain a large MAC table, as there are most likely hundreds of device IDs that will be stored in the switch’s table. This is less problematic when the number of clients on your network is small. However, it is still a desirable feature for preventing issues that could arise from running out of space on the table. At that point, the switch would not be able to properly route information, which would significantly impact performance.

Auto-MDIX/MDI support is becoming commonplace. Without this feature, devices that contain MDI (media independent interface) or MDIX (media independent crossover) connections on both sides, such as switch-to-switch connections or peer-to-peer computer connections, would require a cross-over cable as opposed to a straight-through. Auto-MDIX/MDI allows devices to be connected to each other using either type of cable, as Auto-MDIX automatically detects the required cable type and configures the connection appropriately. This removes a great amount of confusion while interconnecting devices, as two types of cable connections are no longer needed.

Different Types of Switches

It can become a confusing chore having to wade through the different types of switches. First you have to decide what type of network you would like to employ. As of today, there are two main types of networks that are used at the prosumer and enterprise level: Fiber channel and Ethernet. There is a drastic cost difference between the two, and it is quite normal to run standard Ethernet switches with a Fiber trunk connecting the switches to increase the bandwidth/speed capacity between them. The target audience for this article is the regular consumer, and as such, regular Ethernet switches will be discussed from this point on. After deciding what type of network you're going to build, you have to pick the type of switch you would like to use. For the sake of simplicity, there are three types of network switches that are important to this topic: unmanaged, intelligent/smart and fully managed.

An unmanaged switch is the most basic, and it's what most consumers will buy, as it requires the least amount of set-up and is also the least expensive. An unmanaged switch is just that, unmanaged. They are not configurable and have all of their programming built in. It is ready to work straight out of the box. Many consumers shopping for a network switch are mainly looking to expand the amount of devices that they can connect. An unmanaged switch is perfect in this situation since it requires the least amount of investment with regards to both expense and time.

Linksys SE4008 8 Port Gigabit Ethernet SwitchLinksys SE4008 8 Port Gigabit Ethernet Switch

An intelligent/smart switch is the middle ground between the unmanaged and fully managed switches. They offer limited customization, but do possess the granular control abilities that a fully managed switch has. These are great if you're looking for a bit more control over your network and how it operates. Depending on the switch, you can set up different options like Quality of Service (QoS) and VLANs, which can be useful if you have VoIP-enabled phones in your house, or if you just want to segregate different portions of your network from each other. These are still valid choices for the regular consumer, as they are generally easy to use and you can glean a bit more information off of them on how your network is configured compared to unmanaged switches.

TP-Link TL-SG2008 8 Port Gigabit Desktop Smart SwitchTP-Link TL-SG2008 8 Port Gigabit Desktop Smart Switch

At the top of the range is the fully managed switch. Most of these come with every option currently available to a network engineer. They offer granular control, such as port security, access control lists (ACLs) and greater VLAN ability. A consumer will most likely not purchase one of these because they require time and knowledge to set up properly, and the features they offer are more at home in an enterprise environment. Plus, they're expensive.

Cisco 2600X Series Ethernet Managed Switch Cisco 2600X Series Ethernet Managed Switch

Important Considerations

Every person will have different needs for their home network. One person may value the number of available ports, while another will put a greater value on something like granular control. Most importantly, take inventory of what you have and what you need to make your home network more accessible and usable. The future also needs to be taken into consideration. Just because you may have five devices that you want to physically connect to a network, that number may rise over time.

Size is one consideration, since switches come in all shapes. One brand’s four-port switch may not be same size as another comparable brand. Will you have the space to properly set up and maintain the equipment? Generally, as port count increases, so does the size of the housing that the ports are enclosed in. It is also important to remember that most switches require a certain amount of space around them as they generally vent their heat through the sides of the enclosure.

Speaking of ports, the number of them is one of the most important variables to note. This also requires some level of planning beforehand. Once you run out of ports, that switch’s capacity has been reached and another device must be purchased. It is best to take an inventory of what you currently have and what you wish to physically connect. As stated earlier, it is best to also plan for the future. At some point, you may wish to add devices that you may not have thought of previously, such as set top boxes, game consoles, streaming boxes, IP cameras and IP phones.

Trendnet’s 5 Port TEG-S5g Switch and 24 Port TEG-S24g SwitchesTrendnet’s 5 Port TEG-S5g Switch and 24 Port TEG-S24g Switches

Speed and reliability are also important factors. At the consumer level, you will be looking at switches that support speeds of 10/100/1000 Mb/s. Older 10/100 Mb/s models can be considerably cheaper than gigabit (1000 Mb/s), and are generally fine for light streaming of video and audio. However, most modern devices support gigabit and, for the most part, are not much more expensive than 10/100 switches. Gigabit-class transfers can become increasingly important if you are connected to a server’s network share or are sharing/transferring data between two or more devices. The speed difference alone can make up for the cost difference, as your time will be utilized more efficiently. As we move further into the future, enterprise-level speeds like 10 Gb/s will continue to fall in price. For now, 10 Gb/s is still too expensive; the cost/performance ratio cannot be justified by a majority of home users.

Wireless networking will generally be slower and less reliable than a physical connection, and is contingent on a myriad of factors like environment and placement. If speed is most important to you, then you definitely want the reliability of a physical network capable of delivering more consistent and stable results.

Conclusion

The purchase of a networking switch can be a frustrating one, given all of the options that are available. However, it does not need to be complicated if you arm yourself with a little knowledge and remember to take into consideration all of what you want out of your device. Just remember to plan for the future and not just buy for your network as it stands today. Devices are replaced and new ones are added all of the time, which could require extra performance or capacity.

Considerations like speed, port count, size and reliability are all important aspects that must be taken into account. A budget should be constructed for any added expense that a new switch might compel. This could be as simple as extra network patch cables or something pricier, such as adding structured cabling to your house, allowing you to move your connected device away from the general area of the switch. If you find that the added expense of bringing structured cabling into your home is too much, wireless is always a great option, though its disadvantages must also be weighed carefully.

Wireless technology is now a part of our daily lives. However, a wired network connection will most likely give you greater overall satisfaction since it circumvents the pitfalls of wireless, one of the greatest being environmental factors. Wired tends to be more reliable and is subject to less interference from what is around the structured cabling. Most consumers will likely find it within their budget (and needs) to acquire at least an eight-port Gigabit unmanaged switch to let them attach devices like PCs, network storage and consoles, structured cable locations permitting, allowing them to centralize their connections.

MORE: Networking in the Forums

Eric Bliss is an Associate Contributing Writer for Tom's Hardware.

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  • zodiacfml
    The article is all over the place. It will just confuse a basic consumer. Layer 3 switches need not to be mentioned as they are for organizations. Networking "hub" need not also to be mentioned as you cannot purchase a "new" one anymore and the article doesn't explain well why it causes collisions. I also don't know why it has to mention enterprise equipment and racks.

    One thing it also fails to mention are home Wi-Fi routers. They are all in one devices that almost have four extra LAN ports for connecting a LAN cable. These ports are made possible as they have an integrated "switch" device. If that is sufficient then a consumer might not need a switch.

    In some larger homes, you might want to add a switch connected to a Wi-Fi router to increase the number of available of ports. First reason, a homeowner might need LAN ports immediately in wall outlets. Second, for installing and filling the home with Wi-Fi access points. Third reason is for other IP devices such as security cameras, IP phones, and others. So, one major feature excluded in the article is PoE. An advanced home network might need to deploy a PoE switch if it has security cameras and Wi-Fi access points at the same time to avoid the need of using power adapters for each networking device. PoE discussion can be expanded as it has two power level standards which can be an issue with Wi-Fi ac standard access points.
    7
  • Vistouf
    Router vs Switch.. That's what I wanted to read about.
    1
  • boju
    I fried a switch once...

    Wanted a USB to RJ45 dongle for the WiiU instead of using it's wireless. EB games/Dick Smith didn't sell Nintendo's dongle anymore so got near enough what i thought might work. One of those USB to RJ45 but came with two ends, i thought one end was just another spare LOL. Was a USB to USB extension over Cat5 cable and had the RJ45 straight into the switch, matter of minutes it was a lesson learned...

    Not proud of it, but was funny.
    0
  • ubercake
    Anonymous said:
    The article is all over the place. It will just confuse a basic consumer. Layer 3 switches need not to be mentioned as they are for organizations. Networking "hub" need not also to be mentioned as you cannot purchase a "new" one anymore and the article doesn't explain well why it causes collisions. I also don't know why it has to mention enterprise equipment and racks.

    One thing it also fails to mention are home Wi-Fi routers. They are all in one devices that almost have four extra LAN ports for connecting a LAN cable. These ports are made possible as they have an integrated "switch" device. If that is sufficient then a consumer might not need a switch.

    In some larger homes, you might want to add a switch connected to a Wi-Fi router to increase the number of available of ports. First reason, a homeowner might need LAN ports immediately in wall outlets. Second, for installing and filling the home with Wi-Fi access points. Third reason is for other IP devices such as security cameras, IP phones, and others. So, one major feature excluded in the article is PoE. An advanced home network might need to deploy a PoE switch if it has security cameras and Wi-Fi access points at the same time to avoid the need of using power adapters for each networking device. PoE discussion can be expanded as it has two power level standards which can be an issue with Wi-Fi ac standard access points.


    You are pretty critical of a "Switch 101" summary on a web site. You want to read about home wifi routers and PoE in a "Switch 101" article that does a good job of bringing the definition of the basic functionality of a switch to people. Maybe you're looking for the wrong information in an article that clearly isn't called "here's how you connect and configure your entire home network 101".

    This article sticks to the subject of switches and brings it down to a pretty understandable level for most people. It really is well organized and summarizes things at a general level.

    I would think PoE and the like could be addressed in a 102 article that describes what else a switch is capable of and also get into topics on managed switches and their value.
    2
  • ghavadi
    Quote:
    Router vs Switch.. That's what I wanted to read about.
    you can't compare two different things.you only can compare layer 3 switches with routers.but still not the same functionality.
    0
  • joex444
    You can easily compare a router and a switch. Switches have ports that are treated equally and do not have a DHCP server built into them. Routers have one port that is designated a WAN port, meant to connect to the Internet, and shares that connection to its LAN ports (and wireless clients) thanks to its built-in DHCP server.
    1
  • joex444
    To be clearer, if you have a DHCP server *somewhere* on your network and you connect an Ethernet cable that ultimately connects to your DHCP server to one port of, say, a 5 port switch then the other 4 ports will automatically become DHCP clients of the DHCP server that is "upstream" via this 5th port. This is why connecting a desktop to a switch that is connected to a router also works.
    1
  • ghavadi
    Anonymous said:
    You can easily compare a router and a switch. Switches have ports that are treated equally and do not have a DHCP server built into them. Routers have one port that is designated a WAN port, meant to connect to the Internet, and shares that connection to its LAN ports (and wireless clients) thanks to its built-in DHCP server.

    Hmm great point.But layer 3 switches like the Cisco 3750 you can create Dhcp-pools,and can work as a dhcp server.
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  • falcompsx
    full duplex vs half duplex is not the cause / solution to collisions on a network. That is mostly caused by a hub vs a switch. Hubs function as repeaters, every packet of data that a port receives, is sent out every other port. This creates a lot of unnecessary traffic. On a switch, there is a MAC address table and every packet is routed to the port that has the destination MAC address connected and only to that port. Collisions occur when two devices are sending simultaneously and their transmissions "collide" causing a spike in voltage and the data is then destroyed. TCP/IP protocols handle this event by detecting the increased voltage and basically doing a reset(i'll not go into the specifics of how this happens, but it does). The reason a hub can cause this to happen and switches are almost immune to the problem is simple. Imagine you have a 4 port hub, if two devices transmit at the same time, bam, collision. If you replace that hub with a switch, assuming the two sending devices are sending to different recipients, the switch is smart enough to basically route the data to the correct port. Its almost like having a traffic light instead of an uncontrolled intersection. In an example with a 4 port hub, this doesn't really present a problem, but as you grow to a larger and larger hub with more and more connections, the problem grows exponentially and happens more and more frequently. Switches on the other hand, just keep on sending data only to one port or the other.

    Back to duplex, assuming an ethernet connection, half duplex vs full duplex will NEVER cause a collision because transmit and receive are on seperate wires. The real difference between half and full duplex are bandwith. Full duplex is effectively double the bandwith of a half duplex connection. 100mbps half, can send, or receive at 100mbps max. Full duplex can send AND receive at 100mbps in each direction at the same time without any delays, so effectively you have 200mbps of bandwith. What is useful about this is for troubleshooting purposes, if you have a slow network connection, one of the first things to check is the negotiated speed. If you have a gigabit network, you should see 1gbps as your connection speed(1gbps is always full duplex, 1gbps half duplex doesn't exist in ethernet specs) if you see 100/half, you know something is wrong. Either a bad cable, driver, or some other issue is preventing your connection from negotiating properly at the maximum supported speed.
    3
  • ubercake
    Anonymous said:
    You can easily compare a router and a switch. Switches have ports that are treated equally and do not have a DHCP server built into them. Routers have one port that is designated a WAN port, meant to connect to the Internet, and shares that connection to its LAN ports (and wireless clients) thanks to its built-in DHCP server.


    You don't even need a DHCP server running to connect devices to the internet through a router.
    0
  • beetlejuicegr
    Nice article, i am having a very simple gigabit switch here at home but due to some PC relocation temporarily, my pc was stuck with the ethernet ports of the router. You can't imagine my frustration at working with 100Mbps. Hope they start making gigabit routers as a base. I wonder why they dont tbh.
    0
  • Kewlx25
    Quote:
    full duplex vs half duplex is not the cause / solution to collisions on a network. That is mostly caused by a hub vs a switch.


    Full-duplex cannot have collisions. The only reason hubs have collisions is because they cannot be full-duplex. Switches can have collision only when in half-duplex mode. So yes, collisions is a duplex issue.
    -1
  • trifler
    Indeed. Too many people jump on wireless without thinking. Wireless obviously has its conveniences, but one should not give up on wired for fixed location devices.

    Another thing I find most people don't think of is that printers can be connected directly to a switch using Ethernet instead of using USB to connect to a computer. This allows all of your devices to use it without having to turn on the computer, as you need to with a USB connection. You also don't have to use network sharing. It's easy and convenient.
    0
  • zodiacfml
    He has a point. Considering the audience here in TH are home users, the article does not touch on this Wi-Fi router and switch comparison. Many of us wouldn't need to purchase a switch if there's an existing Wi-Fi router already as the switch is only to expand the number of LAN ports. These days, wireless convenience trumps the performance and reliability of cable connectivity.

    Quote:
    Quote:
    Router vs Switch.. That's what I wanted to read about.
    you can't compare two different things.you only can compare layer 3 switches with routers.but still not the same functionality.
    1
  • zodiacfml
    Quote:
    Quote:
    full duplex vs half duplex is not the cause / solution to collisions on a network. That is mostly caused by a hub vs a switch.


    Full-duplex cannot have collisions. The only reason hubs have collisions is because they cannot be full-duplex. Switches can have collision only when in half-duplex mode. So yes, collisions is a duplex issue.


    He is right. It is due to a hub device. You cannot buy a hub anymore which is why we don't have issues anymore with collisions. Switches/Wi-Fi routers are cheap enough these times. I was not even able to buy or touch a hub device ever. It could have one advantage though, over a switch, it doesn't need power or power adapters to work which can be useful in times where there is no easy way to get to a power outlet.
    1
  • InvalidError
    Anonymous said:
    I was not even able to buy or touch a hub device ever. It could have one advantage though, over a switch, it doesn't need power or power adapters to work which can be useful in times where there is no easy way to get to a power outlet.

    Hubs aren't plain passive devices: they have a chip that takes the data from whichever port it detects incoming data from and then drives the data out on all TX pairs. Smarter hubs detect which port sent data first and then blank out all other ports until the current port's packet is done to reduce wire time wasted on collisions and jabber, almost guaranteeing that one packet will always get through.

    For most intents and purposes, hubs died with 10Base-T some 15+ years ago.
    1
  • jehanne
    Remember, the 7-layer OSI is a reference model; the 4-layer IP model is a protocol model. Unless you are a student preparing for the CCNA exam, it does not help "Joe 6-pack" much to discuss the OSI model. Ditto for Layer 3 switching (which, refers to the IP model and not the OSI one); a Layer 3 switch, in addition to switch frames (a Layer 2 function), also switches packets, a Layer 3 function typically done by a Router. A home router combines the router with a 4-port switch!
    1
  • Ryangrant
    I'm finding that Link Aggregation is becoming more popular among small businesses and home users that do heavy media transfering over their LAN. Link Aggregation support is not supported on many of todays routers/switches and is something the consumer needs to look out for if they're wanting to consider aggregation on their network. The LACP protocol is a very popular one among the link aggregation community for consumers and businesses.
    0
  • computertech82
    Missing the part where some switches are INTELLIGENT switches and have built in dhcp server (aka assigns ip address). A non-intelligent switch = no ip assigned, needs something else to assign them, or static ips.
    Article all over the place. Makes something simple, hard........
    -1
  • willie nugs
    The only part of this article that I've read so far is the first section called "Network Switch Basics" and I feel fully qualified by now to say this article sucks.

    Now I want to go write a proper Network Switch 101 article and submit it to tomshardware.com for publication.

    I'm sorry for the harsh words, Eric Bliss. But this article truly does suck.
    2