Structured Cabling: Strengthening the Backbone

Testing is Vital
It is not just important to choose the right cabling and quality of installation, but also its field testing and maintenance are equally imperative.

New trends in copper, the installation has become more difficult and stringent; new parameters have made field testing for equal-level far-end crosstalk (ELFEXT), Powersum equal-level far-end crosstalk and Alien Crosstalk, etc far more complex. These require highly skilled installers and also field testing equipment that has Level 4 specification and gives accurate results as proposed by ISO/IEC to test Class F links.

In fiber, the new developments of OM3 and OM3+ multimode cables require fiber testers that have fiber modules with laser sources to ensure standards compliant certification.

Cabling Trends

India is now at the forefront of adopting new cabling technologies. Although Cat6A and Cat7 have shown slow adoption rate, the signs are encouraging. Intelligent cabling is another preferred tool that is being lapped up by enterprises and data centers. The speculation that Category 6 technology would start to replace Cat 5e technology is becoming a reality today. From a market share of just 20% in 2005, Cat6 is poised to grab a prominent share of 35% this year.

10GE on the Rise: The year 2007 will see a substantial growth in demand for 10GE especially by large data centers. This provides ten times the speed of a standard Gbps network. The good thing is that it has been tested on both fiber and copper. The latter will help data centers have high bandwidth at low cost. 10G adds a sub-layer in the PHY (physical) layer of the OSI model, and uses a different encoding scheme (64/66b) for better error rate detection during data transfer. Plus, it supports full duplex transmission only.

10GE will facilitate bandwidth-intensive applications such as VoIP and digital video conferencing. Enterprises can locate their data centers and disaster recovery centers in a different city, and yet get faster access. The cost of moving from Gigabit to 10 Gb will be two to three times more, but the performance gain might make it worth the effort. The cost of 10G products is expected to decrease.

Cat 7 Cabling: It is essentially the latest and fastest Ethernet cabling standard, which gives full backward compatibility to 10/100/1000 Mbps networks. It's the only cabling standard in copper that supports high-speed data transfers. But there is one limitation in Cat 7 over fiber; with fiber you can connect two end-points within a distance of 45 Km, but while using copper you can go only up to 100 m. So, if you are planning to build a MAN, then there is no option other than going for fiber.

Managed Structured Cabling: Also commonly referred to as intelligent cabling solution, this is another key trend in structured cabling today. As data centers become more complex with more equipment coming in, you need something like this to manage the connectivity. It is a real-time Layer-1 management system for networks.

Such an intelligent system consists of an end-to-end structured cabling system with intelligent patch panels and software agents that provide a complete view of physical layer connectivity and connect it to logical layers. It collects real-time information used to automatically maintain database connectivity, and is capable of presenting data in a compressed format, enabling administrators to troubleshoot and document the network efficiently.

You can, for example, immediately trace broken links and rectify them. Being real time, the system allows administers to resolve all issues quickly. When this is coupled with today's manageable switches the efficiency increases tremendously. As a result the admin will not only be able to find and manage SNMP enabled devices from a central location but also be able to check for data patterns running through the network. With the growth of multi-location office and large and multiple campus areas, the importance of properly managing network resources has become very important and intelligent cabling lets you do this.

Intelligent cabling will reduce the cost of network ownership by solving issues like unplanned downtime, inefficient manual moves, adds and changes, redundant ports, inaccurate records, etc. It increases the network management efficiency and network security considerably.

Fiber gets an Edge: Choice between fiber and copper cabling is also getting more defined as adoption of bandwidth-intensive applications is increasing in the enterprises. Interest towards deploying fiber optic cabling is high among Asia Pacific companies, and India is no exception.

The share of the twisted pair copper is very high compared to fiber optic in the horizontal market, which might probably be less than 10% but in the long run, fiber may displace twisted pair.

Today, both fiber and copper have major advances in bandwidth capability, to support the next generation of LANs at 10G. Multimode fiber has advanced to new levels to support laser-based systems where as the industry is developing twisted pair cabling that will provide at least a three-fold increase in bandwidth, but with limitation on distance.

Fiber optic is the dominant type of cable for connecting separate buildings on campuses and connecting floor distributors to building distributors. Because of its high cost on the LAN equipment side it has been limited to the backbones. If we compare the cost of a fiber port on the active equipment and that of Gigabit copper port on the active equipment, the fiber is almost six times higher.

Going Wireless: A significant market trend is that providers of wiring infrastructure have expanded their offerings, as widespread wireless LAN deployment appears inevitable. As wireless increasingly infiltrates the "wired" world, people everywhere are working where they want with access to the information they need. Through new standards and technologies, the growth of wireless LANs (WLANs) in the premises environment has risen to an all-time high, making the network more flexible than ever while increasing worker mobility and productivity.

Room for Expansion
It is important to keep in mind the physical orientation of the building. Telecommunications rooms, entrance facilities (EF), main distribution frames (MDF) and intermediate distribution frames (IDFs) should allow for 20% expansion of equipment.

Placing telecommunications IDFs in central locations in the data center enables easy cable management as well as the efficient addition of future equipment. Planning for future equipment population and adjacencies facilitates pathway design for expansion space, which in turn provides near-new construction efficiency for future cable installation.

Installation Practices
Installation of structured cabling product is equally important like the product selection. Following the right installation practices and adherence to standards is very important when it comes to new applications that require higher data rate transfer.

Proper installation is critical to the performance of the system. Qualified installers know how to handle the wire during installation and to be aware of such factors as pull strength, minimum bend radius, proper termination techniques, separation of communication cables from electrical wiring, and the importance of maintaining tight twists.

Category 5, 5E, 6 and 7 Performance Specification Chart
Parameter	Category 5	Category 5E	Category 6	Category 7
Specified frequency range (MHz)	1-100	1-100	1-250	1-600
Attenuation (dB)	24	24	21.7	20.8
NEXT (dB)	27.1	30.1	39.9	62.1
Power-sum NEXT (dB)	N/A	27.1	37.1	59.1
ACR (dB)	3.1	6.1	18.2	41.3
ELFEXT (dB)	17	17.4	23.2	N/A
Propagation delay (nsec)	548	548	548	504
Delay skew (nsec)	50	50	50	20
What it all Means
NEXT (Near End Crosstalk): Adjacent pairs are susceptible to cross-talk, ie strong signals from one pair might be picked up by adjacent pair(s) PSNEXT (Power Sum NEXT): Sum of individual NEXT effects on each pair by the other three pairs ACR (Attenuation to Crosstalk Ratio): Difference between cross-talk loss and attenuation FEXT (Far End Crosstalk): Similar to NEXT, except that the signal is sent from the near end and crosstalk is measured at the far end ELFEXT (Equal Level Far End Crosstalk): FEXT with attenuation subtracted from it. Thus, it gives a more accurate picture and is preferred Propagation Delay: Time required for a signal to propagate from one end of the circuit to the other Delay Skew: The difference in propagation delay between the fastest and the slowest pairs in a UTP cable. If it is too high, it may not be possible to reconstruct the signal at the receiving end

As one expects better transmission capacities, say 10 Gbps over copper or use of fiber optics till desk top (FTTD), the transmission medium and the physical layer needs to be treated with care, especially installations in equipment rooms, where one gets convergence of all kinds of LAN cables, also at the points of termination.

As the physical layers becomes more and more complex, due to use of LAN for many additional non data applications like voice, video, HAVC systems, fire alarms, CCTV, public address systems, etc systematic installation, proper labeling systems, and even use of intelligent cabling improves maintenance efficiencies.

Indian market is mainly a UTP market and Category5e, Category6, Category6A are the three UTP cabling systems that are available for data communication

It is possible to provide a cabling design without knowing where any of the devices will be located as per the open-office cabling practice. The entire design for the cabling can be based on the maximum usage of the size and type of space. For example, a typical voice and data work area for an office can be located every 100 sq ft (9 sq m), and the building management systems (BMS) devices can be calculated based on every 250 sq ft (23 sq m). Even if an open-office cabling approach is not utilized, costs can still be reduced by consolidating the cable-delivery methods for the voice, data, video, and BMS services.

Historically, voice and data horizontal cabling has not been installed during the construction phase. Installing cabling during the construction phase is easier, minimizes damage to finished surfaces, and is reusable for the life of the structure when designed properly.

New cabling does not have to be installed every time the tenants move, or when systems are changed or upgraded. This helps to eliminate cluttered floor and ceiling spaces. In addition, constant rewiring within a structure tends to cause modifications that may affect the physical structure of the building and the integrity of the technology deployed in the structure.

Malovika Rao
malovikar@cybermedia.co.in