What are Ethernet cables?

ethernet cable

Ethernet is the traditional technology for connecting wired local area networks (LANs), enabling devices to communicate with each other via a protocol — a set of rules or common network language.

Ethernet describes how network devices can format and transmit data packets so other devices on the same local or campus area network segment can recognize, receive and process them. An Ethernet cable is the physical, encased wiring over which the data travels.

Compared to wireless LAN technology, Ethernet is typically less vulnerable to disruptions — whether from radio wave interference, physical barriers or bandwidth hogs. It can also offer a greater degree of network security and control than wireless technology, as devices must connect using physical cabling — making it difficult for outsiders to access network data or hijack bandwidth for unsanctioned devices.

How they work

wired lan ethernet data link layer 4 638

The Institute of Electrical and Electronics Engineers Inc. (IEEE) specifies in the family of standards called IEEE 802.3 that the Ethernet protocol touches both Layer 1 — the physical layer — and Layer 2 — the data link layer — on the OSI network protocol model. Ethernet defines two units of transmission: packet and frame. The frame includes not just the payload of data being transmitted, but also:

  • the physical media access control (MAC) addresses of both the sender and receiver;
  • VLAN tagging and quality of service information; and
  • error correction information to detect transmission problems.

Each frame is wrapped in a packet that contains several bytes of information to establish the connection and mark where the frame starts.

Ethernet initially ran over coaxial cables, while a typical Ethernet LAN today uses special grades of twisted pair cables or fiber optic cabling. Early Ethernet connected multiple devices into network segments through hubs — Layer 1 devices responsible for transporting network data.

If two devices that share a hub try to transmit data at the same time, however, the packets can collide and create connectivity problems. To alleviate these digital traffic jams, the IEEE developed the Carrier Sense Multiple Access with Collision Detection (CSMA/CD) protocol, which allows devices to check whether a given line is in use before initiating new transmissions.

How do you choose an ethernet cable

The easiest way to select a cable is to pick the one with the range and performance you need. But what do you need?

Start with the speed of your home internet connection. If you have gigabit internet, an old Ethernet cable will hold you back. But if you have a slower connection, say 10 or 20 megabits per second, you’re good with anything Cat 5 or newer.

Next, consider the speed you need for your network. This is frankly irrelevant for most home users. But if you move big files between computers frequently, or you stream extremely high-bandwidth video content, a better Ethernet cable can make a difference.

Finally, consider your router. Some cheap routers only support Ethernet up to 100 megabits per second, so it will bottleneck anything newer than Cat 5. Even the best home routers rarely support more than gigabit Ethernet, so Cat 6a and Cat 7 are of questionable use.

With all of the above to consider, a Cat 6 cable is the one you’ll most likely need. Most homes can get away with Cat 5e.

What is "Cat" ?

If you’ve ever browsed cables online, you’ve probably noticed that they’re nearly always classified as “Cat-5,” “Cat6e,” or something similar. “Cat” simply stands for “Category,” and the number that follows indicates the specifications to which the cable was manufactured. A general rule of thumb is that the higher numbers represent faster speeds and higher frequencies, measured in Mhz. As is the case with most technologies, newer cables tend to support higher bandwidths, and therefore increased download speeds and faster connections.

Keep in mind that longer Ethernet cables will result in slower transmission speeds, though cables bought for personal use rarely exceed 100 meters; and so are unlikely to experience much speed drop-off. Take a look at the table below to see the differences.

CategoryShieldingMax Transmission Speed (at 100 meters)Max Bandwidth
Cat 3Unshielded10 Mbps16 MHz
Cat 5Unshielded10/100 Mbps100 MHz
Cat 5eUnshielded1,000 Mbps / 1 Gbps100 MHz
Cat 6Shielded or Unshielded1,000 Mbps / 1 Gbps250 MHz
Cat 6aShielded10,000 Mbps / 10 Gbps500 MHz
Cat 7Shielded10,000 Mbps / 10 Gbps600 MHz
Cat 7aShielded10,000 Mbps/10 Gbps1,000Mhz

Cat 3 and Cat 5

Both Cat 3 and Cat 5 Ethernet cables are, at this point, obsolete. It’s not unheard of to find Cat 5 cables still in use, but you shouldn’t even think about trying to buy either of these Ethernet cables. They’re slow, and nobody makes them anymore.

Cat 5e

The “e” in Cat 5e stands for “enhanced.” There are no physical differences between Cat 5 and Cat 5e cables, but 5e Ethernet is built under more stringent testing standards to eliminate crosstalk — i.e., the unwanted transfer of signals between communication channels. Cat 5e is currently the most common type of Ethernet cable, mainly due to its low production cost and ability to support faster speeds than the original Cat 5 cables.

Cat 6

Cat 6 cables support much higher bandwidths than Cat 5 and Cat 5e cables, but they’re also more expensive. Cat 6 cables are more tightly wound than their predecessors and are often outfitted with foil or braided shielding. This shielding protects the twisted pairs of wires inside the Ethernet cable, helping to prevent crosstalk and noise interference. Cat 6 cables can technically support speeds up to 10 Gbps, but can only do so for up to 55 meters.

 

Cat 6a

The “a” in Cat 6a stands for “augmented.” In comparison to the regular Cat 6 cables, 6a cables support twice the maximum bandwidth and are capable of maintaining higher transmission speeds over longer cable lengths. Cat 6a cables are always shielded, and their sheathing — which is thick enough to eliminate crosstalk completely — makes for a much denser, less flexible cable than Cat 6.

Cat 7

Cat 7 cables utilize the newest widely available Ethernet technology and support higher bandwidths and significantly faster transmission speeds than Cat 6 cables. They’re proportionally more expensive than other Ethernet cables, though their performance reflects their premium price tag. Cat 7 cables are capable of reaching up to 100 Gbps at a range of 15 meters, making them an excellent choice for connecting modems or routers directly to your devices. Cat 7 cables are always shielded and use a modified GigaGate45 connector, which is backward compatible with regular Ethernet ports.

Cat 7a

Although not widely available and with few supporting networking hardware options, Cat 7a currently offers the highest-specification Ethernet cables you can buy. Although the transmission speed is no different than that of Cat 7, Cat 7a cables offer a more than 50 percent improvement in overall bandwidth, which in certain settings may be useful. They are far more expensive than any other options though, and so they should only really be considered in very niche cases.

Cat 8

Cat 8 cables aren’t yet widely available but may become so in 2019. We can expect them to hit the market with faster maximum speeds and higher maximum bandwidths than Cat 7a cables.

Ethernet glossary

The differences between the various types of Ethernet cables are actually pretty simple, but it’s easy to get confused by some of the nomenclature. To help out, we’ve put together a quick rundown on what different terms mean, and what you should expect if you buy a cable with those designations.

Cat: Stands for “category.”

TP: Twisted Pairs. This terminology refers to the way that the wires inside the cable are twisted together. Twisted Pairs have been an industry standard for years, and are only inferior to fiber-optic cabling in terms of maximum length and speed drop-off.

UTP: Unshielded Twisted Pairs. Cables designated UTP won’t have foil or braided shielding, which makes the cable cheaper to produce and more flexible, but you’ll sacrifice signal quality and increase vulnerability for crosstalk.

STP: Shielded Twisted Pairs. Cables with STP or SSTP designations are protected with braided shielding, which is usually made of copper or another conductive polymer. Shielding reduces noise and improves connection quality.

FTP: Foiled Twisted Pairs. Cables with FTP or SFTP designations are protected with foil shielding, which helps reduce noise and improves connection quality.

 

What is Power over ethernet(PoE)

Power over Ethernet (POE) is a technology that lets network cables carry electrical power.

For example, a digital security camera normally requires two connections to be made when it is installed:

A network connection, in order to be able to communicate with video recording and display equipment

A power connection, to deliver the electrical power the camera needs to operate

However, if the camera is POE-enabled, only the network connection needs to be made, as it will receive its electrical power from this cable as well.

Benefits of PoE

Time and cost savings – by reducing the time and expense of having electrical power cabling installed.  Network cables do not require a qualified electrician to fit them, and can be located anywhere.

Flexibility – without being tethered to an electrical outlet, devices such as IP cameras and wireless access points can be located wherever they are needed most, and repositioned easily if required.

Safety – POE delivery is intelligent, and designed to protect network equipment from overload, underpowering, or incorrect installation.

Reliability – POE power comes from a central and universally compatible source, rather than a collection of distributed wall adapters.  It can be backed-up by an uninterruptible power supply, or controlled to easily disable or reset devices.

Scalability – having power available on the network means that installation and distribution of network connections is simple and effective.

Devices that have Power over ethernet

POE has many applications, but the three key areas are:

VoIP phones – the original POE application.  Using POE means phones have a single connection to a wall socket, and can be remotely powered down, just like with the older analog systems.

IP cameras – POE is now ubiquitous on networked surveillance cameras, where it enables fast deployment and easy repositioning.

Wireless – Wifi and Bluetooth APs and RFID readers are commonly PoE-compatible, to allow remote location away from AC outlets, and relocation following site surveys.

To find out about the myths and misconceptions about Power over Ethernet, options for high-power POE, and a little more about how the technology works, please continue to POE Explained, Part 2.

 

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