Understanding PoE & PoE Switch

Enterprises are quickly evolving with new network devices to improve communication and security. Power over Ethernet (PoE), a way to deliver electrical power over LAN cables to network devices, has been widely deployed to provide power to various endpoints in the enterprise environments. If you want to upgrade you network to PoE, one way is to deploy a PoE switch. This paper will provide an overview of the PoE technology and PoE switches.

What Is a PoE in Networking?

Power over Ethernet, also known as PoE, is a networking feature defined by the IEEE 802.3af and 802.3at standards. PoE is able to combine the two connections into one Ethernet cable so that single network cable will transmit both data and 25W of electricity. By this way, it can minimize the number of wires when installing the network, which realize the lower cost, less downtime, easier maintenance, and greater installation flexibility in networking.

POE-working-principle

Why Use PoE?

Because PoE is allowed to use one cable for both power and data transmission, PoE can save money on purchasing and running cable for networking equipment. It can brings many advantages to the network as follows.

  • Time and cost savings

Network cables do not require a qualified electrician to install them, and can be located anywhere, so PoE eliminates the time and cost of hiring professional electrical installers.

  • Flexibility

Network administrators can deploy devices (eg: IP cameras and wireless access points) at wherever they are needed most, and redeploy easily if required.

  • Safety

Because PoE utilizes a relatively low voltage, it presents low risks of electrical hazards.

  • Scalability

PoE makes it simple to add new equipment to a network.

What is a PoE Switch Used for?

A POE switch is a network switch that has a built-in PoE injection. It can connect other network devices as normal, and the switch will detect whether they are PoE-compatible and enable power automatically. PoE switches are available to suit all applications, ranging from low-cost unmanaged edge switches with a few ports, to complex multi-port rack-mounted units with sophisticated management. They can run PoE up to 100 meters from the switch or hub to the NIC, regardless of where the power is injected. The limitation is not the power, it’s the Ethernet cabling standards that limit the total length of cabling to 100 meters.

POE Switch

Which FS Switches Are PoE-capable?

FS.COM provides fully managed PoE switches, which are available with 8, 24 or 48 PoE Gigabit Ethernet ports of auto-sensing IEEE 802.3af/at. The PoE Switches are ideal for small business networks that need to inexpensively use PoE to deploy wireless access points and IP-based network surveillance cameras. They deliver robust performance and intelligent switching for growing networks, so PoE switches will be a best choice to install and manage your devices. The model details of FS’s PoE switches are listed below.

fs-poe-switches

How to Ensure Successful PoE Deployments?
1. Provide Sufficient Power to the Remote Powered Device

According to the IEEE 802.3af standard, the powered remote device can draw up to 12.95 watts of power. Considering the loss of the cable length, the power sourcing equipment (PSE) must have the ability to provide 15.4 watts of power to each port. For example, a 24-port Ethernet switch needs approximately 370 watts of power to supply the necessary power to each port. The PoE switches should have in excess of 370 watts available in view of the size of the power supply used in each device. It depends on how much power their switching functions require.

2. Connect the Power Source to Uninterruptible and Redundant Power

Connect the critical power-sourcing devices to an uninterruptible power supply, and use devices with dual redundant power supplies to ensure that your critical devices never lose power.

3. Deploy Only IEEE 802.3af-compliant Devices

Carefully read the technical documentation and contact the technical-support number to determine compatibility. Failure to do so will leave you frustrated and will cost you time and money.

4. Pay Attention to Cabling-performance Specifications

Pay close attention to the manufacturer’s specifications and look for Cat5e and Cat6a compliance. Also, you should remember per TIA standards, only four connectors can exist between the switch or hub and the network interface card (NIC). A midspan device should be counted and treated as one of these connection points.

5. Use the Most Cost-effective PoE Method for Your Network

The business motivation behind deploying IP-based technologies like WiFi and VoIP is to decrease networking costs. A significant benefit of PoE is that it runs on your existing infrastructure.

Conclusion

PoE is a recently-developed technology, and it simplifies the enterprise deployment with lower operating expense, higher availability, and faster deployment. FS has provided PoE switches in a variety of specifications, which may make your trip as comfortable as possible. For more information, please welcome to www.fs.com.

Fundamentals of Power over Ethernet (PoE)

With the introduction of new Ethernet-enabled devices expanding geometrically, the need to power these devices from standard AC power outlets has become a limiting factor. IP telephones, wireless access points, IP cameras and device servers are examples of devices limited by the need to have an AC power outlet nearby to plug in a DC power adapter. At best, power supply installation and wiring adds labor and results in the mess of extra wiring; worst case, the lack of nearby AC power means devices cannot be installed where they are needed.

In response to this need, IEEE developed IEEE802.3af to standardize a system of supplying low voltage power to networked devices via the communications line. It is more commonly referred to as Power over Ethernet (POE). This article focus on introducing some fundamental elements about PoE.

Basic Concepts of PoE

PoE is defined across a single network link that includes three basic components. The first one is an equipment delivering power to the cable (often referred to as a PSE, which stands for power sourcing equipment). The second component is a device receiving power from the cable (also known as a powered device, or PD). The third is the cable itself.

Typical PDs include IP cameras, wireless access points, and the PSE would normally be a PoE switch or a midspan power injector, patched in to add PoE capability to a non-PoE network switch channel or similar. These two configurations are shown in the following picture.

PoE

Advantages of PoE

The most prominent advantages of PoE are time saving and cost effective. By reducing the time and expense of having electrical power cabling installed, network cables do not require a qualified electrician to fit them, thus it can be located anywhere. Besides, it has great flexibility. Without being tethered to an electrical outlet, the PDs (IP cameras, wireless access points) could be located wherever they are needed most. Safety is the third advantage. PoE delivery is intelligent and it is designed to protect network equipment from overload, or incorrect installation. Also it has reliability and scalability. 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.

Applications of PoE

The original PoE application is VoIP phones, which have a single connection to a wall socket, and can be remotely powered down, just like with the older analog systems. PoE could also be used in IP cameras. It is ubiquitous on networked surveillance cameras where it enables fast deployment and easy repositioning. Wifi and bluetooth APs and RFID (radio frequency identification devices) readers are commonly PoE-compatible, to allow remote location away from AC outlets, and relocation following site surveys.

How PoE Works

PoE is designed to operate over standard network cable: Cat 3, Cat 5, Cat 5e or Cat 6 (often collectively referred to as Cat 5), using conventional RJ45 connectors. The principles of carrying electrical power over Cat5 are of no difference to those of other power distribution systems, but as the power is being transferred over light-duty cable for long distances, the effects of the power loss and voltage drop become significant.

The arrangement and connection to the cabling used for PoE also differ slightly from conventional power wiring, in order to work around the existing standard for Ethernet data. Cat 5 network cables contain a bundle of eight wires, arranged as four twisted pairs shown in the following picture. In the most common type of Ethernet, 100BASE-T or Fast Ethernet, only two of the four pairs are used to carry data; each pair carrying a signal in one direction. These are known as the data pairs, and the remaining two are unused and are referred to as the spare pairs.

PoE working

Although each data signal can be carried within a single pair, PoE treats each pair of wires as a single conductor (a reason for this is that using both wires halves the overall resistance). As electrical current must flow in a loop, two pairs are required to allow power to be carried by the cable, and either the data or spare pairs can be used for this. The PD must be able to accept power from whichever pairs the PSE delivers it to.

Conclusion

PoE is a convenient and now ubiquitous method for delivering power to a wide variety of loads on standard Cat 5 Ethernet cables. It is no doubt that Power over Ethernet will become increasingly important in the near future.