Guide to the considerations of a network design and installation project

General

Circuit Numbering

A numbering system should be implemented to ensure that each circuit from a cabling centre to a desktop outlet is unique. The circuit identifier should consist of three parts:

The cabling centre ID – a number allocated to the cabling centre

The patch panel ID – a letter identifying the patch panel within a cabling centre. This will run from ‘A’ through to ‘Z’ but omitting ‘I’ and ‘O’ as these can be misinterpreted

The circuit on the patch panel – a number running from ‘1’ at the beginning of a patch panel to the last socket number on the patch panel (typically 24 or 48). This number re-starts at ‘1’ on each patch panel within the cabling centre.

The label at the desk outlet should reflect its location and appropriate documentation should link this to the panel identifier/location.

Cabling Centres

A cabling centre is the location where the cabling from the desktop sockets and the backbone cabling meet. It consists of one or more cabinets containing active data equipment (such as switches) and patch leads / cords connecting these and the backbone circuits (e.g. telephone) to the desktop circuits.

A cabling centre is known as a horizontal distributor in BS EN 50173 series and ISO/IEC 11801 and a horizontal cross-connect in ANSI/TIA/EIA-568-B.

Cabinet Layouts

A typical cabinet layout should consist of the following segmented areas.

The fibre optic circuits are presented at the top of the cabinet, the active equipment below that, then the desktop circuits and finally the telephone circuits at the bottom.

Patch Leads / Cords

In order to avoid confusion as to the function of patches within the cabinet, different colours should be used for patch leads / cords.  The Category of the cord shall match the Category of the installed cables and connectors.

Category-6 and beyond

Category 6 is now widely available in the market place and Category 7 is coming into existence. As described in Table 1 – Glossary of network cabling terms – Category 6 provides improved performance over Category 5e with negligible cost difference and the emergin Category 7 standard will represent even further performance enhancements.

Horizontal Cabling Standard

Horizontal cabling permanent links (from the local cabling centre to the desk outlets) shall be specified to be Class D performance (min) in accordance with BS EN 50173-2. (An equivalent alternative is to specify that the performance shall meet Category 5e (min) in accordance with ANSI/TIA/EIA-568-B).

Unless Category 7 components are used, both ends of the balanced cabling shall be terminated “RJ-45” connectors of the appropriate Category to meet the desired cabling performance.  If Class F performance of BS EN 50173-2 is specified the connections shall be in accordance with IEC 61076-3-104 (Tera interface).

Where the performance specified exceeds the minimum requirement, full details of the specification should be provided with the operational and technical benefits.

Cable Type

The cables shall contain four balanced pairs and have a low fire hazard sheath material.

Horizontal cables (from the local cabling centre to the desk outlets) shall be specified to be unscreened Category 5 (min) in accordance with BS EN 50173-2.

An equivalent alternative is to specify that the cables shall meet Category 5e (min) in accordance with ANSI/TIA/EIA-568-B.

Where the screened cabling is specified or where the performance specified exceeds the minimum requirement, full details of the specification should be provided with the operational and technical benefits.

Cable Sheath

The cables shall contain four balanced pairs and have a low fire hazard sheath material.

Cable Lengths

The TIA specifies that horizontal cable lengths should not exceed 90 metres.  It is the responsibility of the installer to ensure that all cables are within length prior to the installation.

Horizontal cables must not contain any joints; they must be continuous from the patch panel to the termination point.

Cable Routes

All UTP cable should be run internally to the building. External grade UTP cable is available for runs where a network point is within 200m of a network switch; fibre should be installed for runs in excess of this. Cable routes should be agreed with your client in advance. All vertical cables should be secured to installed trays at intervals as recommended by the cabling manufacturer. Care must be taken to avoid close proximity of cabling to pipe work.

Walls and Floors

Holes drilled through walls and floors for the routing of cables should be suitably sleeved to prevent damage to the installed cables. Where cables pass through floors, protection should be extended to at least skirting height. Where cables, trunking, traywork or conduit pass through floors or walls, suitable fire sealing should be provided in accordance with IEE 16th edition cabling regulations (BS7671: 1992).

Cable Trunking

All cables should be installed within suitable containment such as PVC trunking, cable tray, basketwork, steel trunking or steel conduit. Containment should have sufficient expansion capacity to cater for doubling of the cabling contained. All cables in corridor ceiling spaces must be contained. Cables must not be left lying on the top surface of suspended ceilings, nor should they be in contact with any heating pipes located above the ceiling.

Segregation

BS6701 states requirements for segregation between telecommunications cables and mains power cables for purpose of protection (safety) and references the requirements for segregation in EN 50174-2 for electromagnetic interference.

These requirements shall be applied apply unless the cable manufacturer requires more stringent segregation.

Cable Termination

Where RJ-45 connections are used to terminate 4 pair cables the following pair-pin sequence shall be used:

Pin 1: Orange/White

Pin 2: Orange

Pin 3: Green/White

Pin 4: Blue

Pin 5: Blue/White

Pin 6: Green

Pin 7: Brown White

Pin 8 : Brown

This regime is also termed TIA/EIA T568B and ATT 258A.

Each outlet shall be labelled with the appropriate identifier.  In cabinets this is the circuit identifier, at outlets this shall be as defined for the project.

Patch Panels

Patch panels should be clearly labelled with a securely attached label showing the patch panel identifier

Each socket on the patch panel should also be labelled with the full circuit identifier.

Outlets

Outlets should be provided with shutters that automatically close when device leads are removed and any unused faceplate apertures should be provided with blanking plates.

Cables

All UTP cables should be labelled at each end. The label should be located near the termination point at either end, such that the circuit can still be identified if the termination is removed.

Manufacturers Instructions

All cabling systems and other materials should be installed in compliance with the manufacturer’s instructions.

Testing

There are two forms of testing that should take place on new installations: acceptance testing and witness testing.

Acceptance testing is to be undertaken by the supplier. Witness testing is also to be undertaken by the supplier but in the presence of the client.

Acceptance Testing

Testing shall be performed using test equipment in accordance with IEC 61935-1 to ensure that the required transmission performance Class of BS EN 50173-2 has been met.

Alternatively, if TIA/EIA-568-B specification has been used this can state that:-

Testing shall be performed using test equipment in accordance with IEC 61935-1 to ensure that the required transmission performance Category of ANSI/TIA/EIA-568-B has been met.

The test documentation shall be as specified in IEC 61935-1.

The supplier should provide all necessary test equipment.

Witness Testing

Your client should specify the percentage of tests to be witnessed in order to satisfy themselves that the installation has been successful.

Documentation

Completion Documentation

Upon final completion, the supplier will provide copies of the cable installation completion certificate and of the full test results.

Warranty

There are two levels of warranty; simple – component and complex – link or channel.

A component warranty addresses the failure to function or perform at the specified level. Material warranties of this nature are best given by the manufacturer not the installer and normally carry the requirement to be installed by an “approved installer”.

A complex warranty applies to the cabling in its installed state.  The first of these - a link warranty -covers the performance of the terminated installed cabling.  It is a component warranty combined with some installation requirements.  A link warranty typically guarantees the performance of the installed cabling when measured using specific test equipment.

Over and above the link warranty, a channel warranty additionally covers the performance of the installed cabling delivered through any additional active or passive components – i.e. from patch lead / cords and through devices such as switches.

Test results are currently specific to the test equipment used therefore should a dispute arise, the client should ensure that the “specified test system” of the warrantor will be the one referred to and used.
BS 6701 makes the requirements for BS EN 50174-1, -2 and -3 mandatory and should therefore be the basis for cabling warranties.

Backbone Optical Fibre Standard

Optical fibre is used to provide the data backbone connections between cabling centres. Multimode optical fibre is normally used within and between buildings. Singlemode optical fibre is also used for longer runs between buildings.

The selection of the type and performance of multimode optical fibre from the Categories OM1, OM2 and OM3 of BS EN 50173-2 is ffs.

Cable Construction

Cable should be capable of withstanding temperatures in the range -10°C to 50°C without degradation in performance.

Cable Routes

All cables should be either:

• Enclosed in trunking

• Pulled in duct

• Securely fastened to tray

Cable Joints

All cables should be complete between termination points, no cable joints should be permitted. Fibres may only be spliced within termination points. Fibre optic splicing involves joining two fibre optic cables together. Fibre splicing typically results in lower light loss and back reflection than termination making it the preferred method when the cable runs are too long for a single length of fibre or when joining two different types of cable together. Splicing is also used to restore fibre optic cables when a buried cable is accidentally severed. There are two methods of fibre optic splicing, fusion splicing & mechanical splicing.

Cable Protection

Holes drilled through walls or floors for the routing of cables should be suitably sleeved to prevent damage to installed cables. Where cables pass through floors, such protection should be extended to at least a height of 2 metres.

Fire Protection

Where cables, trunking, tray-work or conduit pass through floors or walls, suitable fire sealing should be provided in accordance with IEE 16th Edition Cabling Regulations (BS7671: 1992).

Cable Termination

All optical fibre cables should be terminated within purpose-built patch panels mounted within communications cabinets.

Labelling

All connectors and splices in the termination housings should be clearly labelled using a defined code.

Termination Enclosure Management

Suppliers should provide all necessary cable guides, rings and troughs to ensure that patching can be achieved in a neat and organised manner in line with the manufacturer’s specification. Each fibre should be assigned a unique number to clearly identify it.  The presentation of each fibre should be in accordance with the requirements of the network equipment being installed.

Cables

All cables should be clearly marked at 5 metre intervals and at points of entry and exit for concealment, indicating the assigned identifier. Cables should be labelled within one metre of the termination enclosures at both ends. Fibres should be individually colour coded to aid identification.

Fibre Optic Testing

Suppliers should make provision for testing each individually terminated fibre with an OTDR (Optical Time Domain Reflectometer).

The test shall be undertaken at 850nm/1300nm for multimode optical fibre and 1310/1550nm for singlemode optical fibre.

The test results shall be provided in electronic format together with the required software to read them.

The supplier should provide all necessary test equipment.

Manufacturer’s information is required regarding bandwidth of multimode optical fibre.

Manufacturer’s information is required regarding the specification of singlemode optical fibre.

Completion Documentation

In addition to the completion documentation as specified for horizontal cabling, schematics should also be provided to detail all cable runs and termination points, the installed cable capacity and cable identification references. Lengths and types of cable should also be identified

Warranty

All materials and workmanship should be guaranteed for at least 12 months following completion of the cable installation and acceptance by the client. Suppliers should confirm that physical defects should be repaired free of charge for materials and labour during the warranty period. Appendix C section 2.14.2 contains a full reference to the different type of warranties available.

Cabinets and Frame Room

Equipment Cabinets

All cabinets should be tested for electrical safety in accordance with the IEEE 16th Edition Cabling Regulations.

Suppliers and contractors should provide documentary evidence that all required testing has been completed and the installation is in accordance with the IEEE 16th Edition Cabling Regulations (BS7671:1992).

Cabinet Rooms (Communications Cabling Centres – CWC’s)

All purpose built communications cabling centres (CWC’s) should adhere to the minimum size and standards specifications detailed by or in conjunction with your client.

Cabinet Locations

Cabinet locations should be of minimum size and space for access to rear and sides. A minimum of 500mm should be allowed between the side and back of cabinets where these are floor mounted. Front access should allow for a minimum of 1m clearance. It should be dust free, have suitable ventilation, lighting and security.

Electrical

Adequate power consumption and distribution should be assessed for present and future requirements.

Cabling Frames

Where purpose designed cable frames are specified or proposed (e.g. Krone), each frame should be provided with:

A 1U blanking plate located at the top of the cabinet and engraved with an identification code to be confirmed by the client.

A means of being secured to floor, ceiling or overhead racking as appropriate.

Documentation wallet.

Cable management in the front of the cabinet for routing of patch cords both horizontally and vertically.

Completion Documentation

Each cabinet should be provided with a documentation wallet to be located inside the cabinet, in an accessible location.

Each equipment cabinet should be provided with a 1U blanking plate to be located at the top of the cabinet and engraved with an identification code to be confirmed by the client.

A proposed cabinet layout schematic for each equipment cabinet must be provided.

Completion documentation should include as installed schematics for each equipment cabinet, cabling frame or network installation.

Introduction to Wireless Networks

For the home or small office a wireless network can represent the best overall solution to enable equipment, information and Internet access to be shared.

The communication protocols for wireless networking are defined by the IEEE 802.11 standard, which incorporates the 802.11a, 802.11b and 802.11g protocols. Wireless-G, or 802.11g, is a newer protocol that is becoming more widely adopted as it is capable of speeds up to 54Mbps rather than the 11Mbps of 802.11b devices.

Bluetooth is a wireless protocol designed to connect equipment such as mobile phones and PDAs.

Although it is possible to connect two computers together via Bluetooth adaptors - and Bluetooth access points are available - they cannot compete with the flexibility or throughput of a wireless network. The range of Bluetooth is only about 10m and the data rate is only 723Kbps with a typical throughput of only 300Kbps, making it virtually unusable except for small file transfers.

Another wireless option is the Infrared protocol known as IrDA (Infrared Data Association). Many notebook computers are equipped with IrDA wireless adaptors, and these allow simple file transfers between nearby computers as well as the downloading of photos from digital cameras. The IrDA protocol is rated at 4Mbps with a high-speed version called VFIR rated at 16Mbps.

HomeRF 2.0 is a competing wireless standard that is claimed to be up to 2.5 times faster than 802.11b although it is rated at only 10Mbps. While access points, USB and PCI adaptors are available for less than their 802.11 counterparts, the technology is not compatible with any 802.11 device and is widely expected to be unsupported in the near future.

Access Point

An access point is required to connect equipment with wireless cards to an existing network. An access point acts as a translator between wireless network traffic and cabled network traffic, acting as a gateway between the two.

As well as being located on the network, an access point is also the centre of a wireless network.

Wireless devices in the vicinity can connect to the access point via radio waves and these transmissions are converted by the access point into traffic on the network.

Some access points are also capable of communicating with other access points using a protocol called Ethernet over AP. It is quite common for access points to have integrated routers and, sometimes, broadband modems. The router component allows the device to connect to remote networks such as the Internet for maximum connectivity.

Wireless ranges

Although wireless transmission ranges vary greatly and lowering the bandwidth will increase the coverage area, a standard 802.11b or 802.11g device will typically have a range of about 30m indoors and up to 120m line-of-sight outdoors. Devices using the higher frequency 802.11a protocol will have a range of about 12m indoors and 30m line-of-sight outdoors.

The main reason for the variance between indoors and line-of-sight coverage is that walls and other objects impede the wireless signal. Because wireless transmissions are actually low frequency radio waves, they will pass through walls and other solid matter relatively easily - but as the distance increases, the throughput decreases. This is because lower signal strength will result in dropped packets and result in a general decrease in network efficiency.

Advantages of wireless

Wireless networks have several advantages over cabled networks:

Mobility: Wireless networks can provide users with access to real-time information anywhere in their organisation  - there are now thousands of universities, hotels and public places with public wireless connection. These free you from having to be at home or at work to access the Internet.

Installation speed and simplicity: Installing a wireless network can be fast and easy and can eliminate the need to pull cable through walls and ceilings.

Operating speed and security: The recent improvements in wireless networking standards under 802.11g provide improved speed and the introduction of WPA over WEP gives higher levels of security.

Disadvantages of wireless

However there are also some disadvantages that need to be taken into consideration:-

Security: Whilst the new WPA security standard is an improvement, it is still widely accepted that a cabled network is more difficult to hack into.

Interference:  Other devices may interfere with connectivity or data transfer, walls can cause obstruction and weather can also cause interference

Speed: Speeds for wireless networking depend on which standards you use, but are usually lower and more variable than speeds on conventional network connections. Modern networks allows speeds of up to 100Mbs, and even older networks will achieve 10Mbs. With the exception of new systems, most wireless networks will be lucky to achieve even 10Mbs; their performance often varies according to the layout of the office.