Showing posts with label cables. Show all posts
Showing posts with label cables. Show all posts

Sunday, November 15, 2015

Networking - Structured Cabling

 

Structured Cabling

Although the physical layout of a network will to some extent be determined by its size and the type of networking technology chosen, the cabling system is a critical element of any network. It is generally accepted that a significant number of network failures are caused primarily by cable-related problems. Getting the cabling system right, therefore, is essential for an effective data communications system. With this need in mind, the development of industry standards for cabling standards has accompanied developments in network and communication technology. National and international telecommunications cabling standards have been widely adopted, all of which are based on the American ANSI/TIA/EIA cabling standards. The standards have been evolving since the mid-1980s, with the aim of creating a structured system for data communications cabling systems used in buildings that would support multi-vendor networking products and environments. The result was the TIA/EIA 568 Commercial Building Telecommunication Cabling standard, released in 1991. The ISO/IEC-11801 Generic Customer Premises Cabling standard is an international cabling standard based on the ANSI/TIA/EIA-568 cabling standard. Related European standards include EN 50173 and EN 50174.

The standards define how to design, build, and manage a cabling system that is structured, meaning that the system consists of a number of discrete sub-systems or blocks, each of which has specific performance characteristics. The blocks are organised hierarchically within a unified communication system. A workgroup LAN block, for example, has lower-performance requirements than a network backbone block, which usually requires high-performance fibre-optic cable. The standards have evolved to support high-speed networking technologies such as Gigabit Ethernet, and advanced cable types such as Category 6 and Category 7 twisted pair cable.

Structured cabling (sometimes referred to as premise wiring) defines a generic telecommunication wiring system for commercial buildings, and comprises the cabling, connectors and accessories used to connect local area network and telephone system equipment within a building. It breaks cabling systems down into two main elements, horizontal wiring and vertical (or backbone) wiring. Structured cabling standards define the media, topology, termination and connection points, and administrative practice to be used.
Some terms of reference are defined below:

  • Horizontal wiring - all cabling between the telecommunications outlet in a work area and the horizontal cross-connect (also known as a floor distributor) in the telecommunications closet, including the telecommunications outlet itself, an optional consolidation point (or transition point) connector, and the horizontal cross-connect. Horizontal wiring, as the name suggests, usually runs horizontally (e.g. above suspended ceilings or below computer flooring) and does not go up or down between floors in a building. The maximum distance allowed between the telecommunications closet and the communication outlets is 90 metres, regardless of cable type. An additional 6 meters is allowed for patch cables at the telecommunication closet and in the work area, but the combined length of these patch cables cannot exceed 10 meters. The horizontal cable should be four-pair 100Ω UTP cable (the latest standards specify Category 5E as a minimum), two-fibre 62.5/125-mm fibre-optic cable, or 50/125-mm multimode fibre-optic cable.
  • Vertical (or backbone) wiring - runs up through the floors of a building (risers) or across a campus, and is the cable used between telecommunications closets, entrance facilities, equipment rooms and buildings, including all cables, cable terminations, and intermediate and main cross connects. Backbone wiring runs between telecommunications closets, equipment rooms and entrance facilities on the same floor, from floor to floor, and even between buildings. The standards specify a hierarchical star topology for backbone cabling, in which all wiring radiates from a central location called a main cross-connect (usually the telecommunications closet). Each telecommunications closet or entrance facility is either cabled directly to the main cross-connect, or via intermediate cross connects. The distance limitations for this cabling depend on the type of cable used and the facilities it connects (twisted pair cable is limited to 90 meters).
  • Work area - a building space in which operatives utilise telecommunications equipment. It includes all cable components between communication outlets (wall sockets) and end-user telecommunications equipment, such as telephones, workstations and printers, including the communication outlet itself. Work area cabling systems are designed to be flexible, but still require careful management. Standard structured cabling installation procedures should be observed when installing work area outlets, and cable terminations should be carried out using the same standard (T568A or T568B) throughout the system to avoid problems like crossed pairs which may arise if standards are mixed. T568B is the more commonly used standard in data applications. The standard requires that two outlets should be provided at each wall plate - one for voice, and one for data.
  • Telecommunications  room/closet (or wiring) - an enclosed area, such as a room or a cabinet, for housing telecommunications equipment, distribution frames, cable terminations and cross connects. In other words, all the hardware required to connect horizontal wiring to vertical wiring. This area will often also house auxiliary equipment, including network file servers. Every building must have at least one wiring closet, and the standard recommends one per floor. Specific closet sizes are also recommended, depending on the size of the service area. There must be sufficient space for service personnel to perform maintenance and carry out other duties, as well as for all of the required hardware. Lighting, power supplies and environmental conditions should also meet the requirements specified by the standard.
  • Equipment room - the space that houses building telecommunications systems such as PBXs, servers, switches etc., and the mechanical terminations of the telecommunications wiring system. It is considered to be different from a telecommunications closet because of the complexity of the components it houses. An equipment room can either take the place of a telecommunications closet or be a separate facility. The functions of an equipment room may even be incorporated in a wiring closet. The equipment room provides a termination point for vertical (backbone) cabling that is connected to one or more telecommunication closets. It may also be the main cross-connection point for the entire facility. In a campus environment, each building may have its own equipment room, to which telecommunication closet equipment is connected, and the equipment in this room may then be connected to a central campus facility that provides the main cross-connect for the entire campus.
  • Entrance facility - contains the telecommunication service entrance to the building, and may also contain campus-wide backbone connections. It also contains the network demarcation point, which is the interconnection to the local exchange carrier's telecommunication facilities. The demarcation point is typically 12 inches from where the carrier's facilities enter the building, but the carrier may designate otherwise.
  • Cabling administration - this is a process that includes all aspects of premise wiring activities related to documenting, managing, and testing the system, as well as compiling and maintaining the architectural plans for the system.

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Structured cabling elements

The diagrams below show the relationship between the horizontal cabling elements in a structured cabling system for both a cross-connect and aninterconnect arrangement. In both cases, the permanent link is the telecommunications outlet (TO), the horizontal cabling, and the horizontal interconnect (patch panel). An optional transition point (TP) is allowed within the 90 metres of horizontal cabling.

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Horizontal cabling elements

The channel is the work area cable (the patch lead) from the terminal equipment into the terminal outlet, the permanent link as already described, a patch cord linking two patch panels, and a final equipment cable into the LAN equipment. The use of two patch panels (a cross-connect) is optional. In many systems, only one is used (an interconnect). Note that in the interconnect version, the maximum combined length of patch cords A and B is 10 metres. In the cross-connect arrangement, the maximum combined length of patch cords A, B and C is also 10 metres.


Some requirements and recommendations

  • Permanent links must not exceed 90 metres.
  • The combined length of patch cords in any channel must not exceed 10 metres.
  • There should be no more than two levels of cross-connect in the backbone. This allows a horizontal cross-connect between the horizontal cabling and the building backbone, and an intermediate cross-connect between the building backbone and a campus backbone, with all campus cables terminating in the main cross-connect.
  • A total of 2000 metres of backbone cabling may be employed, consisting of up to 500 metres of building backbone and 1500 metres of campus backbone.
  • Campus cabling links communications facilities in different buildings and is likely to be optical fibre.
  • A minimum of one horizontal cross connect (or floor distributor) should be provided for every floor (one per 1000 m2 of office space is recommended). One telecommunications outlet should be provided at each work area. A minimum of two per 10 m2 of floor space is recommended.

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Backbone cabling (including campus cabling) and horizontal cabling

Recommended Cabling

Horizontal

Vertical

100Ω 4-pair UTP cabling is recommended, as it has a relatively low cost and supports a range of applications. Enhanced Category 5 (Cat5E) is the suggested minimum specification, as it will support data rates of up to 1 Gbps. Many new installations are now employing Category 6 cabling to support current and future high-bandwidth applications.

150Ω 2-pair STP is generally used for Token Ring applications, although due to its extended bandwidth it can also be used for broadband video applications up to 300 MHz, or for 155-Mbps ATM.

Coaxial cable is not recommended for horizontal wiring.

Fibre optic cable, although both more expensive more difficult to install than other types of cable, is the recommended transmission medium for backbone cabling, because it offers high speed transmission, high bandwidth, and carries data over much greater distances than copper cable. It is also immune to electromagnetic interference, and less likely to require replacement (fibre can also be used for horizontal wiring runs exceeding 100 metres).


100Ω 4-pair UTP cabling can also be used in short-to-medium distance vertical cabling in voice and data networks.
150Ω 2-pair STP can be used for Token Ring networks.


50Ω 10Base2 coaxial cable is recognised by the TIA/EIA standard as a suitable choice for economical vertical wiring, but it is rarely, if ever, used in new installations.

Based On

Tuesday, November 22, 2011

TDR test in Cisco Devices - Cable Testing

I love finding stuff like this. In the course of my daily Internet browsing, today I came across this post from a while back on the CCNP Recertification blog. It turns out a number of Cisco switches (apparently the 3560/3750, and some 4500 and 6500 modules) have a TDR (Time Domain Reflectometer) embedded in each interface. How cool is that?

Cisco's documentation shows the simple but very handy two-part command syntax.

   Switch# test cable-diagnostics tdr interface g0/1

TDR test started on interface Gi0/1

A TDR test can take a few seconds to run on an interface

Use 'show cable-diagnostics tdr' to read the TDR results.
   Switch# show cable-diagnostics tdr int g0/1


TDR test last run on: March 01 00:09:06

Interface Speed Local pair Pair length Remote pair Pair status
--------- ----- ---------- ------------------ ----------- -----
Gi0/1 auto Pair A 20 +/- 4 meters N/A Open

Pair B 20 +/- 4 meters N/A Open

Pair C 21 +/- 4 meters N/A Open

Pair D 20 +/- 4 meters N/A Open
This output shows a cable approximately 20 meters in length connected to interface G0/1, with nothing attached to the far end. If you're like me, your first thought is "very cool, but is it accurate?" I grabbed a couple spare cables of various lengths and set about an unscientific benchmark. I measured each cable in three manners: by hand, with my Fluke TDR, and with a Catalyst 3560G-24PS-S. My observed results are below.

Cable Length Fluke 3560 ----------------------------------------------

A 69 ft 69 ft 20 +/- 4m (~66 ft)

B 21 ft 21 ft 6 +/- 4m (~20 ft)

C 83 ft 83 ft 25 +/- 4m (~82 ft)

As you can see, the 3560 is impressively accurate, even without its allowed 4m variance. My next consideration was whether a TDR test would disrupt interface operation. Trying it on a live port while running a constant ping yielded no observable effect, not even a brief disconnection pop-up. This is clearly a very handy tool. I only wish Cisco would do more to publicize cool features like this.
Taken From: http://packetlife.net/blog/2008/mar/28/investigating-ciscos-built-in-tdr/

Monday, September 29, 2008

Extract Cab Files From EXE - Pocket PC

Hi there,

I recently bougth a HTC Diamond, which unfortunately is not linux based.

I started to download some aplications and noticed that many off them were exe files for Windows XP or Vista, so i had to use Windows XP or Vista via Active Sync to install them, and that some were cab which i could copy to my PDA via Windows or Linux if when i pluged in the usb cable i select the disk option an not active sync, which made my PDA apear as a USB Pen Drive.

Later on e noticed that the Windows XP or Vista exe, only copied a cab file and executed.
So i tried to find were did the cab was and found that the cab file was temporaly in:

Windows\AppMgr\Install

so i thougth that i could catch the cab rigth before installing it, and i succeded.


Basicly what i did was to execute the exe in Windows Xp, them PDA asked if i wanted to install the cab that the exe on Windows XP tranfered i said yes, and that's when you reach the below screen




Now i hit the home button on the PDA to select the file explorer in order to copy the cab, that is temporarily at Windows\AppMgr\Install to another location on PDA, so that you can store it on your PC so that when you want to install it i can do it from linux.

So i selected the explorer as shown bellow.





And went to Windows\AppMgr\Install where the cab was temporarily and copied it to another location on my PDA and canceled the install process in the first picture, but if you wan you can install.

I have tried to copy the cab before the screen on the first picture when it asks if you want to install, but it keep disapering, and the instalation being canceled.

And thats it! Happy Cab Hunt!

Thursday, May 3, 2007

How to wire Ethernet and Console Cable (Cisco - Roll Over)

Cables form layer 1 of the network — the physical layer. Properly connecting cables is fundamental to healthy network communication. Faulty connections could interrupt service or cause packets to be dropped. Without a clear understanding of cabling, you won’t be able to troubleshoot or design your LAN or WAN. Additionally, knowledge of cable types is important for certification tests like the Cisco CCNA/CCENT.


Cabling basics for network admins

  • Your cable works at layer 1 — Physical of the OSI Model. Also at that layer are the 1’s and 0’s that traverse the cable as an electrical or light signal (depending on what type of cabling you are using).
  • Unshielded twisted pair (UTP) copper cable is used for many functions in network cabling: Ethernet, Serial, ISDN, Console, and more.
  • While you could put different ends on a UTP cable, typically it will have a RJ45 end with 8 pins.
  • With a normal Ethernet cable, the wires run straight through, from one end to the other. Straight-through cables are used to connect a PC to a switch, as in Figure A-1 and Figure A-2. Where each one uses one off the cabling standards, the T568B and T568B
 Figure A-1 - Straight-Through Cable 


Figure A-2 - Straight-Through Cable 

Graphic Courtesy of Cisco Systems
  • With a crossover cable (Figure B), the source and destination of the UTP wires are crossed. This allows you to use it to connect a PC to PC, switch to switch, or router to router.
  • In a crossover cable we use both off the cabling standads, T568A and T568B, one in each end, if one end uses T568B the other uses T568A, and vice-versa.



Figure B - Cross Over Cable 


Graphic Courtesy of Cisco Systems
Now, how is cabling for Cisco routers and switches different?


Cisco console and AUX port cabling
There are a few differences between Cisco cabling and other network device cabling. Two things immediately come to mind:
  • Cisco routers, switches, and firewalls use a special “rolled” cable for console and auxiliary port access.
  • Cisco offers intelligent serial cabling.
One of the most confusing things to Cisco newcomers is the concept of the console cable. Other SMB and home-networking devices don’t usually have a console port. With those devices, they receive a DHCP IP address and then you can configure them over the network from there. With Cisco devices, there is no IP address on the device, and you must first use the console port and console cable to configure the router, switch, or firewall OOB (out of band).
The Cisco console cable is a special cable. It isn’t wired like an Ethernet cable. However, if you didn’t have a console cable, you could cut off the end of a straight-through Ethernet cable, change the pin out, and recrimp it to make it a console cable.
Below, you can see the pin out of a console cable. The console cable is a “rolled” cable, because if you look at the pins from one end to the other, it is as if the end was rolled over (the order is flipped), as in Figure C.

Figure C - Console Cable (Rolled Cable)

Graphic Courtesy of Cisco Systems
Traditionally Cisco console cables were RJ45-RJ45 and then you would use a RJ45-DB9 adaptor to connect it to your PC’s serial port (COM port). Today, new Cisco devices come with console cables that have a DB9 adaptor integrated/molded to the cable on one end (Figure D). Keep in mind that the data moving across the console cable is serial data (not Ethernet).

Figure D - RJ45-DB9 adaptor


Graphic Courtesy of Cisco Systems
For those equipements tha don't have an integrated DB9 ports, here how you can make your own DB9 adapter:


Click on the images to enlarge
While what I said above concerning console cables is true for most Cisco devices, there are variations on the console cable. For more detailed information about Cisco console and AUX port cabling (including the pin-out for a console cable so that you can make your own), see this Cisco document Cisco Cabling Guide for Console and AUX Ports.

David Davis has worked in the IT industry for 15+ years and holds several certifications, including CCIE, CCNA, CCNP, MCSE, CISSP, VCP. He has authored hundreds of articles and numerous IT training videos. Today, David is the Director of Infrastructure at Train Signal.com. Train Signal, Inc. is the global leader in video training for IT Professionals and end users.

Taken From: http://blogs.techrepublic.com.com/networking/?p=649
and added some stuff about the cabling standards (like here)


Another good reference for building ethernet cables is:
http://www.ertyu.org/steven_nikkel/ethernetcables.html