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The Communication Backbone

Properly Designing IP Networks for Media-Rich Homes

Less than a decade ago, few homes had more than one computer and little need for a network. For many years since, home networks have essentially looked like toys compared with large enterprise networks.

No more. Todays residential network, while serving those basic data-sharing needs, is just as likely to be running some type of quality of service (QoS), and shuttling audio and video streams from media servers to clients in many locations throughout the home. This all can happen while someone in the home uses Skype or another form of voice-over-IP (VoIP) to speak with a friend or business contact halfway around the world, while their son engages in a networked multi-player battle on his video game console.

The residential network is moving from being a data-only plumbing system to the communications backbone of the home, handling voice, video, multichannel audio, automation/control, monitoring, and security. It has evolved from a step-saving alternative to sneaker-net to mission-critical communication, command and control (C3) system for the home. All of which dramatically raises the ante when it comes to designing the residential networks for your clients new homes.

Given a choice between wired and wireless LANs, Id go wired, if I can, said Mario Leone, senior partner in the Philadelphia-area integration firm Electronic Solutions Company, and a CEDIA trainer. If you want a reliable network, wired is the way to go.

Leone added that a lot of clients these days are saying that they dont want to pay for wiring, figuring that they can go wireless through the home. And, unfortunately this sentiment does not stop with networks. They want you to do wireless lighting control, wireless music, securityeverything, Leone said. When you start bringing a lot of wireless stuff into the house, nothing is going to work, because everything has to contend with everything else.

In Leones opinion, clients are well advised to only use a wireless LAN (WLAN) in those applications where theres an absolute need for it. If a client has desktop computers all over the house, there should be a wire going to each one of them, he said.

A major portion of the overall networks cost is in the cabling infrastructure. Its also the most difficult and expensive portion to upgrade. As requirements change and technology evolves, its relatively easy to swap out internetworking hardware (switches, routers, and network interface cards) as long as the cabling infrastructure is up to snuff. The cabling system is the armature upon which everything else is hung.

Mark Hubert, IT director at Chicago-area integration firm Baumeister Electronic Architects, said that he tries to instill in his sales team the idea that they should wire everything. One of the concepts that we sell is future-proofing, which is making sure that the infrastructure has future capacity for whatever may be coming along, he said. So, we make sure we have high-quality unshielded twisted-pair (UTP) wiring running to as many locations as we possibly can.

Beyond that, Hubert explained, Baumeister also makes sure to run extra capacity between structured wiring panels and the equipment on the rack. One of the things that weve found is, as control systems go TCP/IP and onto the ethernet network, they have demands, he said. They have time-sensitive packets. There are also devices out there that are extremely chatty. So one of our manufacturers standard recommendations is to create a separate network for control. To do this, we have to make sure that we have the cabling infrastructure in place to create two networks within the home, so that we can separate the data network from the control system, if it happens to be using TCP/IP.

It is crucial to follow all cabling and design best practices, most of which are codified in the Telecommunication Industry Associations TIA-570B standard for residential communications cabling systems. Here are just a few of the crucial points:

The right cable and connecting hardware. Jamey Calloway, RCDD, and a product manager at Tyco Electronics AMP Netconnect business, pointed out that, The TIA-570B standard calls for Enhanced Category 5 (Cat-5e) cabling as a minimum, and Category 6 as the recommend UTP cabling for voice and data.

100-meter maximum link length. No individual cabling drop may exceed 100 meters, end to end. In fact, to ensure this, the standard specifies that the permanent, in-the-wall portion of each link (running from the wall-plate at the user area, back to the patch panel or punch-down block in the structured wiring panel) may not exceed 90 meters. This allows for a five-meter patch cord connecting the outlet at the wall plate to the ethernet port on the users PC (or other networked device) and another five-meter patch cord at the other end, connecting the port on the patch panel to an ethernet switch or router port in the SWP.

150 meters from demarc to any outlet. The cabling distance measured from the service providers point of demarcation to the furthest network jack must not exceed 150 meters. So, if any of the horizontal cabling drops are 100 meters (90 meters in the wall, plus two five-meter patch cords), the cable running from the service entry point to the SWP cannot exceed 50 meters.

Dont hardwire anything. As Calloway pointed out, in-the-wall cabling should never be hardwired to anything. It should be terminated at the user areas (the various rooms in the home) with an RJ-45 modular jack (which should match the category rating of the cable). At the SWP, it is terminated on a patch panel (again, one that matches the category rating of the cable). From there, a patch cord is used to connect it to one of the ports on an ethernet switch or router, for example. Alternatively, if this link is an analog telephone extension, it should be patched (at the SWP) to an analog telephone module.

Keep low-voltage wiring away from AC wiring. To minimize unwanted electrical signal coupling between the two, avoid running UTP (and other low-voltage wiring) parallel to the homes AC electrical wiring. (Of course, its bound to be parallel to some of the AC wiring, somewhere. In those cases, Calloway recommended 12 inches or more separation between the low-voltage and high-voltage wiring.) Where the two must cross, they should cross at right angles.

Obey codes. Find out the local code requirements, and be sure that you are in compliance. The key, Calloway said, is open architecture. Planning for the future means designing for flexibility.

Analog telephone and analog television are two examples of legacy services that are transitioning to VoIP and IPTV. Analog applications are slowly going away, and more devices and services are going to ethernet and IP, Calloway observed. The idea that, Im going to put in telephone wiring, and Im also putting in a network, is obsolete thinking. The UTP cabling infrastructure, if properly designed, will support analog phone extensions, ethernet and IP, A-BUS audio distribution, packetized IP-based audio distribution, and IP videoall from the same Cat-5e or Cat-6 cabling system.

Using Category 6 cabling doesnt yield a network that performs to the Category 6 specifications if you terminate it with Category 5 connectors. By the same token, even when using the correct cable and connecting hardware, installation mistakes can easily prevent a network from meeting the published performance criteria. But how does anyone know, if you dont test it?

You dont want to take your cabling infrastructure for granted, said Frank Koditek, residential market manager for cabling manufacturer Belden. Its important to make sure, when you do an installation, that you test it after installation.

Commercial installers tend to adhere much more strictly to testing practices than do residential installers. Many business clients, in fact, are unwilling to make final payment on a cabling installation without proof that the installed network is working up to its specifications. In commercial networks, its a foregone conclusion that testing is done, Koditek said.

Almost any home network is likely to employ some wireless links, so be sure to plan for them, as well. Youll need UTP cabling drops to every point where youll be positioning a wireless access point (AP).

To get good RF coverage, you have to do a site survey, Leone explained. What I do is set up a wireless AP, he said, and run something like NetStumber on my laptop, or use some other device thats a power meter. Then, I can move around the house and see what kind of signal level I have in the various locations. You have to make sure that youve got good WLAN signal strength throughout the house, including the farthest reaches, in all four major corners.

If you cant find one AP location thatll allow you to cover all of the house, then youll need to put two or more APs in, Leone continued. But after you have tentatively identified AP mounting locationsand verified that the client is OK with those mounting pointsyou have to physically walk the house, to make sure that no matter where you are, you can connect with the network.

Many of the latest 802.11n APs require Gigabit ethernet uplinks, or their potential throughput will be bottlenecked by the wired backbone. This isnt a problem, as both Cat-5e and Cat-6 support Gig-E. Just make sure that these cabling runs are patched into Gig-E switch ports.

Many WLAN APs utilize power-over-ethernet (PoE), which means that the AP gets its electrical power over the same UTP cable that is carrying the network traffic. (PoE powering schemes require PoE-capable network switches, or separate power injectors to inject the power supply current onto the network cable.) PoE-capable WLAN APs are handy, as they eliminate the need for an electrical outlet at the APgiving you a lot more placement flexibility.

A key point to bear in mind if using 802.11n APs is that they need more power than current PoE technology (per standard 802.3af) delivers. Work is underway on a new, higher-power PoE standard (802.3at), but until this is in place, you will probably need to power your 11n APs from AC wall outlets.

Hubert cautioned designers to be sure to use encryption on the WLAN. Wired Equivalent Privacy (WEP) hardly counts as encryption these days, as it is too easily cracked. Use WiFi Protected Access (WPA), instead.

Alan R. Frank ([email protected]) is a networking consultant and freelance writer covering the fields of communications, networking, and digital entertainment.