Chapter 1

Topology (Star)

A star topology uses a hub or switch to connect all network connections to a single physical location. Today it is the most popular type of topology for a LAN. With a star: • All network connections are located in a single place, which makes it easy to troubleshoot and reconfigure. • Nodes can be added to or removed from the network easily. • Cabling problems usually affect only one node.

Cat 6 RJ45

Cat 6 supports 10 Gbps Ethernet and high-bandwidth, broadband communications. Cat 6 cables often include a solid plastic core that keeps the twisted pairs separate and prevents the cable from being bent too tightly.

Cat 6a RJ45

Cat 6a is designed to provide better protection against EMI and crosstalk than Cat 6 cabling. Cat 6a provides better performance than Cat 6, especially when used with 10 Gbps Ethernet.

Management (Subnet)

A subnet is a portion of a network with a common network address. • All devices on the subnet share the same network address, but they have unique host addresses. • Each subnet in a larger network has a unique subnet address. • Devices connected through hubs or switches are on the same subnet. Routers are used to connect multiple subnets.

Vertical cross connect

A vertical cross connect connects the MDF on the main floor to IDFs on upper floors. Cabling runs vertically between the MDF and the IDFs.

Geography (WAN)

A wide area network is a group of LANs that are geographically isolated, but are connected to form a large internetwork.

Geography (WLAN)

A wireless LAN covers an area that is roughly the same size as a standard LAN. However, it uses radio signals instead of wires to connect systems together.

Intermediate Distribution Frame (IDF)

An intermediate distribution frame is a smaller wiring distribution point within a building. IDFs are typically located on each floor directly above the MDF, although additional IDFs can be added on each floor as necessary.

Participation (Intranet)

An intranet is a private network that uses Internet technologies. Services on an intranet are only available to hosts that are connected to the private network. For example, your company might have a website that only employees can access.

Open circuit

An open circuit is when a cut in the wire prevents the original signal from reaching the end of the wire. An open circuit is different from a short in that the signal stops (electricity cannot flow because the path is disconnected).

Cat 3 RJ45

Cat 3 is designed for use with 10 megabit Ethernet or 16 megabit token ring.

Cat 5 RJ45

Cat 5 supports 100 megabit Ethernet and ATM networking. Cat 5 specifications also support gigabit (1000 Mb) Ethernet.

Cat 5e RJ45

Cat 5e is similar to Cat 5 but provides better EMI protection. It supports 100 megabit and gigabit Ethernet.

Open impedance mismatch (echo)

Impedance is the measure of resistance within the transmission medium. • Impedance is measured in ohms (Ω). • All cables must have the same impedance rating. The impedance rating for the cable must match the impedance of the transmitting device. • Impedance is mostly a factor in coaxial cables used for networking. Be sure to choose cable with the correct rating (50 or 75 ohm) based on the network type. Never mix cables with different ratings. • When signals move from a cable with one impedance rating to a cable with another rating, some of the signal is reflected back to the transmitter, distorting the signal. With video (cable TV), impedance mismatch is manifested as ghosting of the image. • Cable distance does not affect the impedance of the cable.

Participation (Internet)

The Internet is a large, world-wide, public network. The network is public because virtually anyone can connect to it, and users or organizations make services freely available on the Internet. • Users and organizations connect to the Internet through an Internet service provider (ISP). • The Internet uses a set of communication protocols (TCP/IP) for providing services. • Individuals and organizations can make services (such as a website) available to other users on the Internet.

Internet

The Internet layer is comparable to the Network layer of the OSI model. It is responsible for moving packets through a network. This involves addressing hosts and making routing decisions to identify how the packet traverses the network. Protocols associated with the Internet layer include Address Resolution Protocol (ARP), Internet Control Message Protocol (ICMP), and Internet Group Management Protocol (IGMP).

Network Access

The Internet layer is comparable to the Network layer of the OSI model. It is responsible for moving packets through a network. This involves addressing hosts and making routing decisions to identify how the packet traverses the network. Protocols associated with the Internet layer include Address Resolution Protocol (ARP), Internet Control Message Protocol (ICMP), and Internet Group Management Protocol (IGMP).

Manchester

The Manchester line code uses a different encoding scheme. Instead of measuring positive or negative voltage, Manchester simply uses the transition from one voltage level to another to represent binary data. For example, the transition from a low voltage level to a higher voltage level can be used to represent the binary value 1. The transition from a higher voltage level to a lower one can represent the binary value 0.

Layer 3

The Network layer describes how data are routed across networks and on to the destination. Network layer functions include: • Identifying hosts and networks by using logical addresses. • Maintaining a list of known networks and neighboring routers. • Determining the next network point to which data should be sent. Routers use a routing protocol that takes into account various factors, such as the number of hops in the path, link speed, and link reliability, to select the optimal path for data. Data at the Network layer are referred to as packets.

Non-Return-to-Zero

The Non-Return-to-Zero line code is similar to the Return-to-Zero. Binary 1s are represented by positive voltage while 0s are represented by negative voltage. However, unlike Return-to-Zero, there is no neutral (zero) voltage state between bits.

Layer 1

The Physical layer of the OSI model sets standards for sending and receiving electrical signals between devices. Protocols at the Physical layer identify: • How digital data (bits) are converted to electric pulses, radio waves, or pulses of light. • Specifications for cables and connectors. • The physical topology. Data at the Physical layer are referred to as bits.

Layer 6

The Presentation layer formats or "presents" data into a compatible form for receipt by the Application layer or the destination system. Specifically, the Presentation layer ensures: • Formatting and translation of data between systems. • Negotiation of data transfer syntax between systems by converting character sets to the correct format. • Encapsulation of data into message envelopes by encryption and compression. • Restoration of data by decryption and decompression.

Layer 5

The Session layer manages the sessions in which data are transferred. Session layer functions include: • Management of multiple sessions (each client connection is called a session). A server can concurrently maintain thousands of sessions. • Assignment of a session ID number to each session to keep data streams separate. • The setting up, maintenance, and tearing down of communication sessions.

Layer 4

The Transport layer provides a transition between the upper and lower layers of the OSI model, making the upper and lower layers transparent from each other. Transport layer functions include: • End-to-end flow control. • Port and socket numbers. • Segmentation, sequencing, and combination. • Connection services, either reliable (connection-oriented) or unreliable (connectionless) delivery of data. Data at the Transport layer are referred to as segments.

Main Distribution Frame (MDF)

The main distribution frame is the main wiring point for a building. It is usually located on the bottom floor or basement. The LEC typically installs the demarc to the MDF.

Management (Network)

The term network often describes a computer system controlled by a single organization. This could be a local area network at a single location or a wide area network used by a single business or organization. If two companies connected their internal networks to share data, you could call it one network. In reality, however, it is two networks, because each network is managed by a different company.

Fiber Optic

To connect computers using fiber optic cables, you need two fiber strands. One strand transmits signals, and the other strand receives signals. The following are the components of fiber optic cabling: • The core carries the signal. It is made of plastic or glass. • The cladding maintains the signal in the center of the core as the cable bends. • The sheathing protects the cladding and the core.

LC Connector

• Used with single mode and multimode cabling. • Composed of a plastic connector with a locking tab, similar to a RJ45 connector. • A single connector with two ends keeps the two cables in place. • Uses a ceramic ferrule to ensure proper core alignment and to prevent light ray deflection. • Is half the size of other fiber optic connectors.

MT-RJ Connector

• Used with single mode and multimode cabling. • Composed of a plastic connector with a locking tab. • Uses metal guide pins to ensure that it is properly aligned. • A single connector with one end holds both cables. • Uses a ceramic ferrule to ensure proper core alignment and to prevent light ray deflection.

ST Connector

• Used with single mode and multimode cabling. • Has a keyed, bayonet-type connector. • Also called a push-in and twist connector. • Each wire has a separate connector. • Nickel plated with a ceramic ferrule to ensure proper core alignment and to prevent light ray deflection. • As part of the assembly process, the exposed fiber tip must be polished to ensure that light is passed on from one cable to the next with no dispersion.

SC Connector

• Used with single mode and multimode cabling. • Has a push-on/pull-off connector type that uses a locking tab to maintain connection. • Each wire has a separate connector. • Uses a ceramic ferrule to ensure proper core alignment and to prevent light ray deflection. • As part of the assembly process, the exposed fiber tip must be polished.

Disadvantages (Fiber Optic)

• Very expensive • Difficult to work with • Special training required to attach connectors to cables

Host (Client server)

In a client-server network, hosts have specific roles. For example, some hosts are assigned server roles, which allow them to provide network resources to other hosts. Other hosts are assigned client roles, which allow them to consume network resources. Advantages of client-server networks include the following: • Easy to expand (scalable) • Easy to support • Centralized services • Easy to back up Disadvantages of client-server networks include the following: • Expensive server operating systems • Extensive advanced planning required

Host (P-to-P)

In a peer-to-peer network, each host can provide network resources to other hosts or access resources located on other hosts. Each host is in charge of controlling access to those resources. Advantages of peer-to-peer networks include the following: • Easy implementation • Inexpensive Disadvantages of peer-to-peer networks include the following: • Difficult to expand (not scalable) • Difficult to support • Lack centralized control • No centralized storage

RG-58

10Base2 Ethernet networking (also called Thinnet) 50 ohms

RG-8

10Base5 Ethernet networking (also called Thicknet) 50 ohms

Layers in order

7 Application 6 presentation 5 session 4 transport 3 network 2 data link 1 physical

Incorrect termination or bad connector

An incorrect termination occurs when an incompatible or incorrect connector is used. This can result in reduced performance or complete connection loss. A bad connector is a damaged connector that is causing connectivity issues. For example, a broken locking tab on an RJ45 connector can cause intermittent connection problems.

100 pair cable

A 100 pair cable consists of 100 pairs of copper wires in a single bundle (containing 200 wires). • 100 pair wires use the same coloring scheme as 25 pair wires, repeated 4 times. • Generally, each bundle of 25 wires is wrapped together with a colored nylon string to help separate wires of the same color.

110 block

A 110 block is a punchdown block used for connecting individual wires together. • The 110 block comes in various sizes for connecting pairs of wires (for example 50, 100, or 300 pair). • The 110 block has rows of plastic slots. Each plastic slot connects two wires together: o Place the first wire into the plastic slot on the 110 block. o Insert a connecting block over the wire and slot. The connecting block has metal connectors that pierce the plastic cable sheath. o Place the second wire into the slot on the connecting block. • C-4 connectors connect four pairs of wires; C-5 connectors connect five pairs of wires. • When connecting data wires on a 110 block, you typically connect wires in the following order: o White wire with a blue stripe, followed by the solid blue wire. o White wire with an orange stripe, followed by the solid orange wire. o White wire with a green stripe, followed by the solid green wire. o White wire with a brown stripe, followed by the solid brown wire. Use BLOG (BLue-Orange-Green) to remember the wire order, and remember to start with the white striped wire first. 110 blocks can be used for both telephone and data, and are better suited for Cat5 installations. When using 110 blocks for Cat5 wiring, be sure to preserve the twists in each wire pair to within one-half of an inch of the connecting block.

25 pair cable

A 25 pair cable consists of 25 pairs of copper wires in a single bundle (containing a total of 50 wires). 25 pair cables are often used for telephone installations that have multiple telephone lines, for replacing multiple Cat3/5/5e/6 cables in a single bundle, and for horizontal and vertical cross connects between the MDF and IDFs. Individual wires within the 25 pair cable use the following color coding scheme: • A total of 10 colors are used in two different groups: o Group 1 colors are white, red, black, yellow, and violet. o Group 2 colors are blue, orange, green, brown, and slate. • There are 5 wires of each color. • Every colored wire in group 1 is paired with each color in group 2. For example, you will have the following pairs for the white wires: o White with blue o White with orange o White with green o White with brown o White with slate • Instead of using solid colors, some schemes use striped wires to uniquely identify each wire and its matching wire. For example, a white wire with a blue stripe would be twisted with a blue wire with a white stripe, and a red wire with an orange stripe would be twisted with an orange wire with a red stripe. You can use an RJ21 connector to connect 25 pair cable to other wiring devices, or you can manually connect each wire to the necessary location.

66 block

A 66 block is a punchdown block used for connecting individual copper wires together. • The 66 block has 25 rows of four metal pins. Pushing a wire into a pin pierces the plastic sheath on the wire, making contact with the metal pin. • There are two different 66 block configurations: o With the 25 pair block (also called a non-split block), all 4 pins are bonded (electrically connected). Use the 25 pair block to connect a single wire with up to 3 other wires. o With the 50 pair block (also called a split block), each set of 2 pins in a row are bonded. Use the 50 pair block to connect a single wire to one other wire. • With a 50 pair block, use a bridge clip to connect the left two pins to the right two pins. Adding or removing the bridge clip is an easy way to connect wires within the row for easy testing purposes. 66 blocks are used primarily for telephone applications. When used for data applications: • Be sure to purchase 66 blocks rated for Cat5. • When inserting wires in the block, place both wires in a pair through the same slot to preserve the twist as much as possible.

Topology (Bus)

A bus topology consists of a trunk cable with nodes either inserted directly into the trunk or tapped into the trunk using offshoot cables called drop cables. With a bus: • Signals travel from one node to all other nodes. • A device called a terminator is placed at both ends of the trunk cable. • Terminators absorb signals and prevent them from reflecting repeatedly back and forth on the cable. • It can be difficult to isolate cabling problems. A broken cable anywhere on the bus breaks the termination and prevents communications between any devices on the network.

Topology (Ring)

A bus topology consists of a trunk cable with nodes either inserted directly into the trunk or tapped into the trunk using offshoot cables called drop cables. With a bus: • Signals travel from one node to all other nodes. • A device called a terminator is placed at both ends of the trunk cable. • Terminators absorb signals and prevent them from reflecting repeatedly back and forth on the cable. • It can be difficult to isolate cabling problems. A broken cable anywhere on the bus breaks the termination and prevents communications between any devices on the network.

Cable tester (troubleshooting)

A cable tester (or line tester) verifies that the cable can carry a signal from one end to the other and that all wires are in the correct positions. • Higher-end cable testers can check for various miswire conditions (wire mapping, reversals, split pairs, shorts, or open circuits). • You can use a cable tester to quickly tell the difference between a crossover and a straight-through cable. • Most testers have a single unit that tests both ends of the cable at once. Many testers come with a second unit that can be plugged into one end of a long cable run to test the entire cable.

Demarc extension

A demarc extension extends the demarcation point from its original location to another location within the building. • The demarc extension usually consists of a single wire bundle that attaches to the existing demarc and supplies a termination point to a different location. • You might need a demarc extension if your network occupies an upper floor of a building. The LEC will typically install the demarc into the MDF on the bottom floor, and you will need to install an extension to place the demarc into the IDF on your floor. • You are responsible for installing the demarc extension, but the LEC might do it for an additional charge.

Horizontal cross connect

A horizontal cross connect connects IDFs on the same floor. Cabling runs horizontally between the IDFs.

Geography (LAN)

A local area network is a network in a small geographic area, like an office. A LAN typically uses wires to connect systems together.

Loopback plug (TroubleShooting)

A loopback plug reflects a signal from the transmit port on a device to the receive port on the same device. Use the loopback plug to verify that a device can both send and receive signals. • A failure in the loopback test indicates a faulty network card. • A successful loopback test means the problem is in the network cabling or another connectivity device. You can purchase premade loopback plugs, or you can make an inexpensive one by cutting the end off a cable and manually connecting the transmit wires to the receive wires (connect the wire from pin 1 to the wire at pin 3, and the wire at pin 2 to the wire at pin 6).

Geography (MAN)

A metropolitan area network is a network that covers an area as small as a few city blocks to as large as an entire metropolitan city. MANs are typically owned and managed by a city as a public utility. Be aware that many IT professionals do not differentiate between a wide area network and a MAN, as they use essentially the same network technologies.

Miswired

A miswired cable is caused by incorrect wire positions on both connectors. Several wiring problems might exist: • A reverse connection is when a cable is wired using one standard on one end and another standard on the other end, creating a crossover cable. While this condition might be intentional, it can cause problems when a crossover cable is used instead of a straight-through cable. • Wiremapping refers to the matching of a wire with a pin on one end with the same pin on the other end. For example, an error in the wiremapping results when the wire at pin 1 connects to pin 4. • A split pair condition is when a single wire in two different pairs is reversed at both ends. For example, if instead of the solid green wire, the solid brown wire is matched with the green/white wire in pins 1 and 2. With a split pair configuration, the cable might still work (especially if it is short), but it could introduce crosstalk. o When the 568A/B standards for making drop cables are followed, one pair is split to meet the standards. In this case, a common split pair error is simply placing all wire pairs in order in the connector instead of splitting the pair according to the standard. o When connecting cables using a punchdown block, pairs are not split.

Management (Internetwork)

A network with geographically disperse (WAN) connections that connect multiple LANs is often called an internetwork. Additionally, connecting two networks under different management is a form of internetworking, because data must travel between two networks.

Patch panel

A patch panel is a device that is commonly used to connect individual stranded wires into female RJ45 connectors. For example, you might connect 4 pairs of wires from a punchdown block to a port on the patch panel. On the patch panel, you then connect drop cables (cables with RJ45 connectors) to the patch panel on one end and a computer on the other end.

Geography (PAN)

A personal area network is a very small network used for communicating between personal devices. For example, a PAN may include a notebook computer, a wireless headset, a wireless printer, and a smart phone. A PAN is limited in range to only a few feet. A PAN is typically created using Bluetooth wireless technologies.

Phone cable RJ11

A phone cable is used to connect a PC to a phone jack in a wall outlet to establish a dial-up Internet connection. It has two pairs of twisted cable (a total of 4 wires).

Shorts

An electrical short occurs when electrical signals take a path other than the intended path. In the case of twisted pair wiring, a short means that a signal sent on one wire arrives on a different wire. Shorts occur when two wires touch; this can be caused by worn wire jackets, crushed wires, or a metal object piercing two or more wires

Participation (Extranet)

An extranet is a private network that uses Internet technologies, but its resources are made available to external (but trusted) users. For example, you might create a website on a private network that only users from a partner company can access.

Attenuation

Attenuation is the loss of signal strength from one end of a cable to the other. This is also known as dB loss. • The longer the cable, the more attenuation. For this reason, it is important never to exceed the maximum cable length defined by the networking architecture. • Cables at a higher temperature experience more attenuation than cables at a lower temperature. • A repeater regenerates the signal and removes the effects of attenuation.

RG-59

Cable TV and cable networking 75 ohms

RG-6

Cable TV, satellite TV, and cable networking RG-6 has less signal loss than RG-59 and is a better choice for networking applications, especially when longer distances (over a few feet) are involved. 75 ohms

Coaxial cable

Coaxial cable is an older technology that is usually implemented with a bus topology. It is not suitable for ring or star topologies, because the ends of the cable must be terminated. It is composed of two conductors that share a common axis within a single cable. Coaxial cable is built with the following components: • Two concentric metallic conductors: o The inner conductor carries data signals. It is made of copper or copper coated with tin. o The mesh conductor is a second physical channel that also grounds the cable. It is made of aluminum or copper coated tin. • An insulator that surrounds the inner conductor and keeps the signal separated from the mesh conductor. It is made of PVC plastic. • A mesh conductor that surrounds the insulator and grounds the cable. It is made of aluminum or copper coated tin. • A cable encasement that surrounds and protects the wire. It is made of PVC plastic.

Cable Crossover

Computers can connect directly to one another using a crossover cable. The easiest way to create a crossover cable is to arrange the wires using the T568A standard in the first connector and the T568B standard in the second connector.

Cable Straight-through

Computers connect to the network through a hub or switch with a straight-through cable. There are two standards for creating straight-through cables: • T568A—To use this standard, arrange the wires from pins 1 to 8 in each connector in the following order: GW, G, OW, B, BW, O, BrW, Br. • T568B—To use this standard, arrange the wires from pins 1 to 8 in each connector in the following order: OW, O, GW, B, BW, G, BrW, Br. It doesn't matter which standard you use, but once you choose a standard, you should use the same one for all your cables to avoid confusion later on during troubleshooting.

Crosstalk

Crosstalk is interference that is caused by signals within the twisted pairs of wires. For example, current flow on one wire causing a current flow on an adjacent wire. • The twisting of wires into pairs helps reduce crosstalk between wires. • Each pair of wires is twisted at a different rate to reduce crosstalk between pairs. • Crosstalk is often introduced within connectors, where the twists are removed to add the connector. Crosstalk can also occur where wires are crushed or where the plastic coating is worn. There are several forms of crosstalk: • Near end crosstalk (NEXT) is measured on the same end as the transmitter. For example, when a signal is sent on one wire, near end crosstalk measures the interference on an adjacent wire at the same connector end. • Far end crosstalk (FEXT) is measured on the opposite end from the transmitter. For example, when a signal is sent on one wire, far end crosstalk measures the interference on an adjacent wire at the opposite connector end. • Alien crosstalk is introduced from adjacent, parallel cables. For example, a signal sent on one wire causes interference on a wire that is within a separate twisted pair cable bundle.

Electromagnetic interference (EMI) and radio frequency interference (RFI)

Electromagnetic interference and radio frequency interference are external signals that interfere with normal network communications. Common sources of EMI/RFI include nearby generators, motors (such as elevator motors), radio transmitters, welders, transformers, and fluorescent lighting. To protect against EMI/RFI: • Use fiber optic instead of copper cables. Fiber optic cables are immune to EMI/RFI. • Use shielded twisted pair cables. Shielded cables have a metal foil that encloses all of the wires. Some cables might also include a drain wire (a bare wire in the cable that absorbs EMI/RFI). • Avoid installing cables near EMI/RFI sources.

File transfer File Transfer Protocol (FTP)

FTP provides a generic method of transferring files. It can protect access to files by requiring usernames and passwords, and it allows file transfer between dissimilar computer systems. FTP can transfer both binary and text files, including HTML, to another host. FTP URLs are preceded by ftp:// followed by the DNS name of the FTP server. To log in to an FTP server, use ftp://username@servername. The FTP protocol does not use encryption. All data, including usernames, passwords, and files, are sent over the network as clear text.

Fiber Cable Other Facts

For long cable running between floors or overhead, you might hire an experienced contractor to install the cable and the necessary connectors. Adding connectors onto a fiber optic cable takes some practice; remember to do the following: • Keep the area as clean as possible. • Cut the cable with a clean 90 degree cut. • Polish the end of the cable prior to adding the connector. Use special polishing film and tools for polishing cable ends. • Glue or crimp the connector onto the cable. • Cover or cap any connectors that won't be hooked up immediately. • If necessary, you can directly splice two cable ends together; however, this requires expensive and specialized equipment. When working with fiber optic cabling, you can use media converters to switch between different network media. For example, you can convert: • Single mode fiber to copper Ethernet wiring • Multimode fiber to copper Ethernet wiring • Single or multimode fiber to coaxial wiring • Single mode fiber to multimode fiber

Web Services Hypertext Transfer Protocol (HTTP)

HTTP is used by web browsers and web servers to exchange files (such as web pages) through the World Wide Web and intranets. HTTP can be described as an information requesting and responding protocol. It is typically used to request and send web documents, but is also used as the protocol for communication between agents using different TCP/IP protocols.

Web services HTTP over SSL (HTTPS)

HTTPS is a secure form of HTTP that uses SSL to encrypt data before it is transmitted.

Return-to-zero

In the Return-to-Zero line code, each individual bit in the binary data is identified by dropping the signal to zero between pulses. The way this is done depends upon the media being used: • For copper wiring, binary 0s and 1s are transmitted by sending voltage pulses, with the voltage returning to zero between pulses. For example, a binary value of 1 is represented by setting the voltage to +5 volts, and then dropping it back to 0 volts. A binary 0 is represented by setting the voltage to -5 volts, and then dropping it back to 0 volts again. • For fiber optic wiring, the Return-to-Zero Inverted line code is used. A binary value of 0 is represented by sending a light pulse. A binary value of 1 is represented by sending no light pulse.

Attenuation (Trouble Shooting)

Light signals being transmitted through a fiber optic cable experience attenuation as they pass through the cable. Several factors contribute to signal loss: • Cable length • Connectors • Splices You can use these factors to calculate how much signal loss (measured in dB) you should reasonably expect in a given run of fiber optic cabling. Signal loss is calculated by summing the average loss of all the components used in the cable run to generate an estimate of the total attenuation that will be experienced end-to-end. This estimate is called a loss budget. When calculating a loss budget for a segment of fiber optic cable, use the following guidelines: • Connectors: 0.3 dB loss each • Splices: 0.3 dB loss each • Multimode cabling: 1-3 dB loss per 1000 meters, depending on the thickness and quality of the cable. • Single mode cabling: 0.4-0.5 dB loss per 1000 meters, depending on the thickness and quality of the cable. The total attenuation should be no more than 3 dB less than the total power at the transmission source. This is called the link loss margin. For example, if the total power output at the transmission source of a cable run is 15 dB, then the total attenuation over the cable run should not exceed 12 dB. This ensures that the cable will continue to function as its components (e.g., LED light transmitters and connectors) degrade with age and use.

Media Adapters

Many network switches and routers allow you to insert a gigabit interface converter (GBIC) in an empty slot to convert the interface from copper wiring to fiber optic. Other devices use a small form-factor pluggable (SFP) module to accomplish the same goal. Several issues that can occur when using fiber optic media adapters: • Some GBIC/SFP modules use multimode fiber, while others use single mode. Make sure that you use the correct type of fiber optic cable and connector required by the specific adapter. • Media adapter modules malfunction on occasion. If you have lost connectivity on one of these links, ensure the adapter module is working correctly.

Known-good spares (troubleshooting)

One valuable troubleshooting method is to keep a set of components that you know are in proper functioning order. If you suspect a problem in a component, swap it with the known-good component. If the problem is not resolved, troubleshoot other components. Examples of using this strategy include the following: • Changing the drop cable that connects a computer to the network • Replacing a NIC with a verified working one • Moving a device from one switch port to another

Security protocols Secure Sockets Layer (SSL)

SSL secures messages being transmitted on the Internet. It uses RSA for authentication and encryption. Web browsers use SSL to ensure safe web transactions. URLs that begin withhttps:// trigger your web browser to use SSL.

Cabling

Several issues can occur when working with fiber optic cabling: • Fiber optic cabling is much less forgiving of physical abuse than copper wiring. The fiber core is fragile and can be easily damaged by rough handling. For example, bending a fiber cable at too tight of a radius will break the core. • Wavelength mismatch will cause serious issues with fiber optic cables. You cannot mix and match different types of cable. For example, if you connect single mode fiber to multimode fiber, you will introduce a catastrophic signal loss of up to 99%. Even connecting cables of the same type that have different core diameters can cause a loss of up to 50% of the signal strength.

Connectors

Several issues can occur when working with fiber optic connectors: • For light to pass through a fiber optic connector, the fiber within the jack must line up perfectly with the fiber in the connector. Using the wrong connector will result in misaligned fibers, disrupting the light signal, even if the connector is successfully locked into the jack. • Dirty connectors can also impede or disrupt the light signal, so it's important that they are kept clean. Several cleaning methods can be used with fiber optic connectors: o For connectors where the ferrule protrudes out of the connector, such as the FC connector, you can wipe the end of the ferrule with a lint-free cloth that has a small amount of denatured alcohol applied. Immediately wipe the ferrule dry with a dry, lint-free cloth. o For fiber optic connectors where the end of the ferrule is less accessible, you must use a specialized cleaning tool. Some cleaning tools allow you to plug in the fiber optic cable and then clean it by pumping the tool's handle. o To clean the jacks on fiber optic network interfaces, you can purchase a specialized fiber optic cleaning stick to remove foreign material.

Smart jack (troubleshooting)

Smart jack A smart jack is a special loopback plug installed at the demarcation point for a WAN service. Technicians at the central office can send diagnostic commands to the smart jack to test connectivity between the central office and the demarc. When you contact a WAN service provider for assistance, they might execute a test using the smart jack. A successful test indicates that the problem is within your customer premises equipment (CPE).

Security protocols Transport Layer Security (TLS)

TLS ensures that messages being transmitted on the Internet are private and tamper proof. TLS is implemented through two protocols: • TLS Record can provide connection security with encryption (with DES for example). • TLS Handshake provides mutual authentication and choice of encryption method. TLS version 1.2 (TLS1.2) is an updated version that improves on past security flaws found in TLS 1.0 and 1.1.

Layer (application)

The Application layer corresponds to the Session, Presentation, and Application layers of the OSI model. Protocols associated with the Application layer include FTP, HTTP, Telnet, SMTP, DNS, and SNMP.

Layer 7

The Application layer integrates network functionality into the host operating system and enables network services. The Application layer does not include specific applications that provide services, but rather provides the capability for services to operate on the network. Most Application layer protocols operate at multiple layers down to the Session and even Transport layers. However, they are classified as Application layer protocols because they start at the Application layer (the Application layer is the highest layer where they operate). Services typically associated with the Application layer include: • HTTP • Telnet • FTP • TFTP • SNMP

Layer 2 (LLC and MAC)

The Data Link layer defines the rules and procedures for hosts as they access the Physical layer. These rules and procedures specify or define: • How hosts on the network are identified (physical or MAC address). • How and when devices can transmit on the network medium (media access control and logical topology). • How to verify that the data received from the Physical layer are error free (parity and CRC). • How devices control the rate of data transmission between hosts (flow control). Data at the Data Link layer are referred to as frames.

Host-To-Host

The Host-to-host layer is comparable to the Transport layer of the OSI model. It is responsible for error checking and reliable packet delivery. Here, the data stream is broken into segments that must be assigned sequence numbers so they can be reassembled correctly on the remote side after they are transported. Protocols associated with the Host-to-host layer include Transport Control Protocol (TCP) and User Datagram Protocol (UDP).

Twisted Pair Cables

Twisted pair cables support a wide variety of fast, modern network standards. The following are facts about the components of twisted pair cabling: • Two wires carry data signals (one conductor carries a positive signal; the other carries a negative signal). They are made of 22 or 24 gauge copper wiring. • Either PVC or plenum plastic insulation surrounds each wire. Plenum cable is fire resistant and non-toxic; it must be used when wiring above ceiling tiles. PVC cable cannot be used to wire above ceilings, because it is toxic when burned. • The two wires are twisted to reduce the effects of electromagnetic interference (EMI) and crosstalk. Because the wires are twisted, EMI affects both wires equally and should be cancelled out. • Multiple wire pairs are bundled together in an outer sheath. Twisted pair cable can be classified according to the makeup of the outer sheath, as described: o Shielded Twisted Pair (STP) has a grounded outer copper shield around the bundle of twisted pairs or around each pair. This provides added protection against EMI. o Unshielded Twisted Pair (UTP) does not have a grounded outer copper shield. UTP cables are easier to work with and are less expensive than shielded cables

PunchDown

Use a punchdown tool to insert wires into 66 or 110 blocks. • The punchdown tool pushes the wire into the block and cuts off the excess wire. • Be sure to position the blade on the side of the clip toward the end of the wire. • The blade for a 66 block is straight, while the blade for a 110 block has a notch in the blade.

Demarcation point (demarc)

When you contract with a local exchange carrier (LEC) for data or telephone services, they install a physical cable and a termination jack onto your premises. The demarcation point is the line that marks the boundary between the telco equipment and the private network or telephone system. • Normally, the LEC is responsible for all equipment on one side of the demarc, and the customer is responsible for all equipment on the other side of the demarc. • The demarc is also called the minimum point of entry (MPOE) or the end user point of termination (EU-POT). • The demarc is typically located on the bottom floor of a building, just inside the building. For residential service, the demarc is often a small box on the outside of the house. • For business installations, the demarc is often identified by an orange plastic cover on the wiring component.

Polishing

Whenever a connector is installed on the end of fiber optic cable, a degree of signal loss occurs. This is calledinsertion loss. Additionally, some of the light that is lost is reflected directly back down the cable towards the source. This is called back-reflection, or optical return loss (ORL), which can corrupt data being transmitted and even damage the transmitter. For a connector to work properly, there must be as little insertion loss and ORL as possible. The better the polish on the connector, the better the light will pass through without reflection. Fiber optic equipment manufacturers rate their connectors using the following polish grading designations: • Physical Contact (PC) polishing is usually used with single mode fiber. The ends of the fiber are polished with a slight curvature so that when the cable end is inserted into the connector, only the cores of the fiber actually touch each other. • Super Physical Contact (SPC) and Ultra Physical Contact (UPC) polishing uses a higher grade of polish and has more of a curvature than PC polishing, further reducing ORL reflections. • Angled Physical Contact (APC) polishing is used to reduce back reflection as much as possible. An APC connector has an 8-degree angle cut into the ferrule, which prevents reflected light from traveling back down the fiber. Any reflected light is bounced out into the cable cladding instead. You can only use angle-polished connectors with other angle-polished connectors. Using an angle-polished connector with a non-angle-polished connector causes excessive insertion loss. APC connectors are colored green to prevent them from being mixed with non-APC connectors.

Single Mode (Fiber Cables)

• Data transfers through the core using a single light ray (the ray is also called a mode). • The core diameter is around 10 microns. • At distances up to 3 km, single mode delivers data rates up to 10 Gbps. • Cable lengths can extend a great distance.

Multimode (Fiber Cables)

• Data transfers through the core using multiple light rays. • The core diameter is around 50 to 100 microns. • At distances of under 2 km, multimode delivers data rates up to 1 Gbps. • Cable lengths are limited in distance.

RJ11

• Has 4 connectors • Supports up to 2 pairs of wires • Uses a locking tab to keep the connector secure in an outlet • Used primarily for telephone wiring

RJ45

• Has 8 connectors • Supports up to 4 pairs of wires • Uses a locking tab to keep the connector secure in an outlet • Used for Ethernet and some token ring connections There is another connector type called RJ48c that is almost identical to RJ45. RJ48c uses the same connector as an RJ45, but it is used for specific WAN connections, such as a T1 line, and is wired differently.

Advantages ( Coaxial Cables)

• Highly resistant to EMI (electromagnetic interference) • Highly resistant to physical damage

AUI

• Is a DB15 serial connector • Used in 10Base5 Ethernet networks

BNC

• Molded onto the cable • Used in 10Base2 Ethernet networks

Disadvantages (Coaxial Cables)

• More expensive than UTP • Inflexible construction (more difficult to install) • Unsupported by newer networking standards

Ethernet cable

• Pin 1: Tx+ • Pin 2: Tx- • Pin 3: Rx+ • Pin 4: Unused • Pin 5: Unused • Pin 6: Rx- • Pin 7: Unused • Pin 8: Unused

Advantages (Fiber Optic)

• Totally immune to EMI (electromagnetic interference) • Highly resistant to eavesdropping • Supports extremely high data transmission rates • Allows greater cable distances without a repeater

F-Type

• Twisted onto the cable • Used to create cable and satellite TV connections • Used to connect a cable modem to a broadband cable connection

Random Cable Info

• Use a crimping tool designed for RJ45 connectors to attach connectors to UTP cable. • Cat 5/5e/6/6a cables come with wires that have either solid cores or stranded cores. Use solid core cables for longer runs inside walls or the ceiling; use stranded core wires for drop cables where frequent movement occurs and flexibility is needed. • There are different connectors for solid and stranded core wires; be sure to use the correct connector type. • To reduce crosstalk, keep the pairs twisted as much as possible right up to the connector. • Making Cat 6-compliant cables is difficult. If you do not add the connectors correctly, the cable will function only as a Cat 5 cable

Fiber Coupler

• Used in optical fiber systems with one or more input fibers and one or several output fibers. • Light entering an input fiber can appear at one or more outputs. • Power distribution potentially depends on the wavelength and polarization. • Wavelength-sensitive couplers are used as multiplexers.

FC Connector

• Used only with single mode cabling. • Each wire has a separate connector. • Uses a threaded connector. • Designed to stay securely connected in environments where it may experience physical shock or intense vibration.