Cabling for LAN and Premise Architecture

July 31, 2013 at 10:00 AM

 

Diagram of Wiring Closet Rack

It's hard to fathom just how quickly Ethernet technology has grown. Today no modern office building would be functional without premise wiring, or the cabling run throughout the building to connect computers to the LAN.

 

We may be on the verge of a wireless revolution with new technologies like DAS and MESH, but for now you should at least understand the basic architecture of LAN cabling.

 

LAN wiring is often broken into three types: backbone, horizontal runs, and patch cabling, each with its own purpose and requirements. In an especially large building or in a campus of buildings, the backbone is the wiring that connects server locations together and to the Internet through an ISP. Since a large amount of data may be carried back and forth by these cables, they are typically designed for bandwidth, like T1 lines or fiber optic cables (usually multi-fiber lines like breakout or distribution style, or even ribbon fibers).

 

Close Up View of Solid Conductor Category-rated Cable

The horizontal runs are the individual cables coming from the servers to the Work Areas. Work Areas are the points where the cable is terminated in a wall plate or jack so a user can plug their computer or other device into it.

 

It is often deceptive to assume that a single horizontal run will connect to a single computer. More likely than not, it is connected into a local Ethernet switch or wireless access point, and many computers may be connected to that. For this reason, the actual data carried on a single horizontal cable could vary greatly, and if you are planning your LAN architecture, this is the trickiest thing to get right. It can also be the most expensive piece to change if you get it wrong as you may need to fish the cable back out of a wall or conduit to re-arrange it.

 

Horizontal runs are currently most often solid-conductor Category rated copper cable. This is slowly changing over to fiber optic cabling as the price gap between the two narrows and fiber optic technology improves. Note that the horizontal cable may also require special jacket types to comply with building fire codes.

 

Right Angle Ethernet Cable Assembly

The patch cabling in a LAN is often overlooked, but is also very important. In general it is used to connect two devices together in a rack in a server room, or to connect a device to a wall jack where a horizontal cable is terminated. Being exposed (not behind a wall or on a rack ladder) and possibly being moved frequently, a patch cable needs to be robust and flexible.

 

While patch cables are easily available and can be bought relatively cheap, you might want to consider that cheap cables may introduce problems to your LAN. Cheap cables often use substitute materials such as copper clad aluminum or feature low quality plugs not rated for the application. Cheap cables seldom pass the testing required for the network and will degrade your network performance.

 

With more devices requiring power (POE), the cheaper cables often cannot carry the added burden due to undersized conductors and low grade copper. For a single user's computer, the impact of this may be limited, but in a server room low quality cables can have a disastrous effect on the entire LAN. If the cable manufacturer you purchase from has a robust QC process, it will help.

 

Other features to consider are molded right angle connectors to ensure the connector isn't bent to fit into limited space, cable boots to make depressing the connector latch easier, and high-flex construction and oil resistant jackets for demanding environments.

 

L-com stocks components for every facet of your LAN, from Ethernet cables, plugs and jacks, to bulk copper or fiber cable, to active media converters. We also go beyond that, to reliable racks, panels and cable management accessories, lightning and surge protectors, Power-over-Ethernet components and everything for wireless deployment.

 

Tutorial on Wireless Networking

June 12, 2013 at 10:00 AM

 

Wireless network antenna and devices

Entire cities and even countries are looking into ways to expand communications access for their residents as the Internet has shifted from a luxury to an imperative. The most promising solution: wireless networking.

 

Why? Wireless networking allows a non-physical (well, at least non-cabled) connection to a wireless LAN (WLAN) and onto the World Wide Web for users. So what are you waiting for? Cut the cord!

 

Be mindful of this though- issues such as network and band congestion, security, signal range and propagation, power demands, and more make WLANs tricky to implement for all but the most informed network engineers and IT professionals. Yet there's no stopping this technology in its rapid advance, with solutions such as distributed antenna systems (DAS) and MESH networks beginning to show promise. For you to get started, here's a basic wireless tutorial on terminology and concepts.

 


Wireless Standards

 

Radio frequency signals can take a lot of different forms, so in order for devices made by different manufacturers to communicate, the IEEE has provided several standards including the mainstay for wireless Ethernet: 802.11.

 

The 802.11 standard specifies the band and IP protocol used to transmit data, and provides guidelines to maximize the speed of transmission. 802.11a, for instance, uses the 5Ghz band and can typically transmit at speeds up to 54 Mbps in shorter ranges. 802.11b, 802.11g, 802.11n, and the new 802.11ac all use various methods to increase the speed and range. The latest IEEE wireless standard, 802.11ac boasts transmission speeds of up to 1 Gbps!

 

Each standard typically requires wireless routers, access points, and other transmission equipment to match its designation, though there are many that can operate in multiple standards (such as routers that are 802.11b/g/n compliant).

 


Wireless Bands

 

In attempt to maintain order within the entire radio frequency spectrum that is available to us, the FCC and other global communications standardization organizations have designated or set aside specific ranges of frequencies for specific uses. We call these "ISM bands". ISM stands for industrial, scientific and medical to denote where these frequencies are used.  ISM bands (specifically the 2.4 GHz and 5 GHz frequencies) are also used in commercial wireless networks. 

 

Typically access points, antennas, and amplifiers all use either the 2.4 GHz band, 5.8 GHz band, or both for WiFi. Other ISM bands have been set aside for things like cell phone use, RFID chips, emergency/municipal use, and military use.

 


Wireless Security

 

As mentioned previously, one of the big emerging issues with wireless networking is security. Without a physical cable that can be plugged and unplugged, the only method to control who can do what on a network is to build it into the software and protocol. That means it is critical to set up a wireless network with appropriate security measures and to be aware of the security status of any network you connect to.

 

For most small networks, methods such as WPA, WPA2, or WPA-PSK allow the safe identification of nodes that should be allowed on a network with passwords and other controls. Wireless routers can also use access passwords to allow administrators to adjust or update security features as required.

 
If you have questions about a wireless project or application, contact L-com's technical support line for a live response and expert advice!
 

Cat 6 Shielded vs. Unshielded

June 5, 2013 at 10:00 AM


Category 6 cable with drain wire

Category 6 or Cat6 Ethernet cable is designed to provide up to 1 Gbps Ethernet transmission, and is required for 1000 Base-T style networks. However, the choice to use unshielded twisted pairs (UTP) or shielded (or screened) twisted pairs (STP or ScTP) depends on the location of the installation.

 

Typically, the shield is only required in cases where the cable is run through an area of high electro-magnetic interference or radio frequency interference (EMI/RFI), such as output by strong power lines, motors, magnets, and radio antennas. Outside of these situations, the shield does not help provide a faster or clearer signal, and can add more problems than it solves.

 

Pros and cons 

 

Without a shield, Cat 6 UTP cable is already resistant to minor and typical forms of EMI/RFI, such as having a fluorescent light or small motor nearby. In these cases, you should always run the cable at a 90° angle to the source of the interference in order to minimize exposure. Otherwise UTP is cheaper, lighter, and just as effective as STP.

 

If you need STP cable, you have to remember that the shield itself must drain, otherwise EMI/RFI can build up on it and degrade the signal inside. Drainage is typically done at the connection site by using a shielded coupler or jack that is connected to ground.

 

Also note that the weight of shielded cable, while not very heavy, can be significant if you are running multiple cables in an area. In some cases, heavy cabling run above a ceiling or behind a wall has caused collapses and structural damage over time.

 

Quick note: Visit L-com's Ethernet Product Center for a huge selection of common and hard-to-find Ethernet cabling solutions, including shielded, harsh-environment, special jacketed and more.
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