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In the document viewer below you will find notes pertaining to Network+. These notes include information on topics such as networking fundamentals, network devices, the OSI model, major networking operating systems, network installation, network security, disaster recovery, troubleshooting, and more. All of these notes are consistent with Network+ college courses offered today.

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Network Fundamentals

Network Elements

Network - describes two or more connected computers that can share resources such as data, a printer, an Internet connection, applications, or a combination of these.

Local Area Network

Local Area Network (LAN) - is limited to a specific area, usually an office, and cannot extend beyond the boundaries of a single building.

Workgroup - is a collection of individuals (a sales department, for example) who share the same files and databases over the LAN.

Wide Area Network

WAN - is any network that crosses metropolitan, regional, or national boundaries.

WANs differ from LANs in the following ways:

• WANs cover greater distances.
• WAN speeds are slower.
• WANs can be connected on demand or permanently connected; LANs have permanent connections between stations.
• WANs can use public or private network transports; LANs primarily use private network transports.
• WANs can use either full- or half-duplex communications. LANs have typically used half-duplex communications, although many local area networks today use full-duplex communications.

The Internet is a collection of networks that are interconnected and, therefore, is technically an internetwork (Internet is short for the word internetwork). A WAN can be centralized or distributed. A centralized WAN consists of a central computer (at a central site) to which other computers and dumb terminals connect. The Internet, on the other hand, consists of many interconnected computers in many locations. Thus, it is a distributed WAN.

Full-Duplex vs. Half-Duplex Communications

With half-duplex, communications happen in both directions, but in only one direction at a time. When two computers communicate using half-duplex, one computer sends a signal and the other receives; then, at some point, they switch sending and receiving roles.

Full-duplex, on the other hand, allows communication in both directions simultaneously. Both stations can send and receive signals at the same time.

Host, Workstation, and Server

The three most common network entities are the host, workstation, and server.

Understanding Workstations

Workstation – normally refers to any computer that is connected to the network and used by an individual to do work.

Client - is any network entity that can request resources from the network; a workstation is a computer that can request resources.

Understanding Servers

A server does exactly what the name implies: It provides resources to the clients on the network (“serves” them, in other words). Servers are typically powerful computers that run the software that controls and maintains the network. This software is known as the network operating system. Servers are often specialized for a single purpose. Here are some examples of servers that are dedicated to a single task:

• File Server Holds and distributes files.
• Print Server Controls and manages one or more printers for the network.
• Proxy Server Performs a function on behalf of other computers. (Proxy means “on behalf of.”)
• Application Server Hosts a network application.
• Web Server Holds and delivers web pages and other web content using the Hypertext Transfer Protocol (HTTP).
• Mail Server Hosts and delivers e-mail. It’s the electronic equivalent of a post office.
• Fax Server Sends and receives faxes (via a special fax board) for the entire network without the need for paper.
• Remote Access Server Listens for inbound requests to connect to the network from the outside. Remote access servers provide remote users (working at home or on the road) with a connection to the network, either via modems or an IP connection.
• Telephony Server Functions as a “smart” answering machine for the network. It can also perform call center and call-routing functions.

Regardless of the specific role (or roles) these servers play, they should all have the following in common:

• Hardware and/or software for data integrity (such as backup hardware and software)
• The capability to support a large number of clients

Understanding Hosts

Host - covers pretty much every other networking device, but it can also refer to a workstation and server and is most commonly used when discussing TCP/IP-related services and functions. For the Network+ exam, however, you should stick to the classic definition used here (i.e., workstations, servers, and other network devices).

Peer-to-Peer vs. Client/Server Architecture

The purpose of networking is to share resources. The two most common network types are peer-to-peer and client/server.

Physical vs. Logical Concepts

Physical aspects of a network, we’re referring to some aspect of the network that you can touch or that has physical substance (like electrons, electrical pulses, or the way cables are run). Logical concepts, on the other hand, are more imaginary and esoteric and deal with things like how data flows in a network.

Peer-to-Peer Network

In peer-to-peer networks, the connected computers have no centralized authority. From an authority viewpoint, all of these computers are equal. In other words, they are peers. Each computer in a peer-to-peer network can be both a client that requests resources and a server that provides resources. This is a great arrangement, provided the following conditions are met:

• Each user is responsible for local backup.
• Security considerations are minimal.
• A limited number of computers are involved.

Client/Server Network

A client/server network uses a network operating system designed to manage the entire network from a centralized point, which is the server. Client/server networks have some definite advantages over peer-to-peer networks. For one thing, the network is much more organized. It is easier to find files and resources because they are stored on the server. Also, client/server networks generally have much tighter security. All usernames and passwords are stored in the same database (on the server), and individual users can’t use the server as a workstation. Finally, client/server networks have better performance and can scale almost infinitely. It is not uncommon to see client/server networks with tens of thousands of workstations.

Physical Topologies

A topology is basically a map of a network. The physical topology of a network describes the layout of the cables and workstations and the location of all network components. Logical topologies define how the information or data flows within the network. The cables or connections in a physical topology are often referred to as network media (or physical media).

Four most common topologies:

• Bus
• Star
• Ring
• Mesh

Bus Topology

In a bus topology, all computers are attached to a single continuous cable that is terminated at both ends, which is the simplest way to create a physical network. On the pro side, a bus topology has the following characteristics:

• Is simple to install
• Is relatively inexpensive
• Uses less cable than other topologies

The following characteristics describe the con side of a bus topology:

• Is difficult to move and change
• Has little fault tolerance (a single fault can bring down the entire network)
• Is difficult to troubleshoot

Star Topology

Each computer in a star topology is connected to a central point by a separate cable or wireless connection. The central point is a device known by such names as hub, MAU, concentrator, switch, and access point, depending on the underlying technology. The increasing popularity of the star topology is mainly due to the large number of advantages, which include the following:

• New stations can be added easily and quickly.
• A single cable failure won’t bring down the entire network.
• It is relatively easy to troubleshoot.

The disadvantages of a star topology include the following:

• Total installation cost can be higher because of the larger number of cables, but prices are constantly becoming more and more competitive.
• It has a single point of failure (the hub, or other central device).

Ring Topology

In the ring topology, each computer is connected directly to two other computers in the network. Data moves down a one-way path from one computer to another On the pro side, the ring topology is relatively easy to troubleshoot. A station will know when a cable fault has occurred because it will stop receiving data from its upstream neighbor. On the con side, a ring topology has the following characteristics:

• Expensive, because multiple cables are needed for each workstation.
• Difficult to reconfigure.
• Not fault tolerant. A single cable fault can bring down the entire network.

Mesh Topology

In a mesh topology, a path exists from each station to every other station in the network, resulting in the most physical connections per node of any topology. While not usually seen in LANs, a variation on this type of topology—the hybrid mesh—is used on the Internet and other WANs in  a limited fashion. Hybrid mesh topology networks can have multiple connections between some locations, but this is done only for redundancy. In addition, it’s called a hybrid because other types of topologies might be mixed in as well. Also, it is not a full mesh because there is not a connection between each and every node, just a few for backup purposes. A mesh topology can become quite complex as wiring and connections increase exponentially. For every n stations, you will have n(n–1)/2 connections. For example, in a network of 4 computers, you will have 4(4–1)/2 connections, or 6 connections.

Backbones and Segments

With complex networks, we must have a way of intelligently identifying which part of the network we are discussing. For this reason, we commonly break networks into backbones and segments.

Understanding the Backbone

Backbone - is the part of the network to which all segments and servers connect.

Understanding Segments

Segment - is a general term for any short section of the network that is not part of the backbone. Just as servers connect to the backbone, workstations connect to segments. Segments are connected to the backbone to allow the workstations on them access to the rest of the network.

Selecting the Right Topology

Generally speaking, you should balance the following considerations when choosing a physical topology for your network:

• Cost
• Ease of installation
• Ease of maintenance
• Cable fault tolerance

Physical Media

Three types of cables:

• Coaxial
• Twisted pair
• Fiber optic

Coaxial Cable

Coaxial cable (or coax) contains a center conductor, made of copper, surrounded by a plastic jacket, with a braided shield over the jacket. A plastic such as polyvinyl chloride (PVC) or fluoroethylenepropylene (FEP, such as DuPont’s Teflon) covers this metal shield. The Teflontype covering is frequently referred to as a plenum-rated coating. That simply means that the coating doesn’t begin burning until a much higher temperature, doesn’t release as many toxic fumes as PVC when it does burn, and is rated for use in air plenums that carries breathable air, usually as nonenclosed fresh-air return pathways that share space with cabling. This type of cable is more expensive but may be mandated by local or municipal fire code whenever cable is hidden in walls or ceilings. Plenum rating applies to all types of cabling and is an approved replacement for all other compositions of cable sheathing and insulation, such as PVC-based assemblies.

Using Thin Ethernet

Thin Ethernet, also referred to as Thinnet or 10Base-2, is a thin coaxial cable. It is basically the same as thick coaxial cable except that the diameter of the cable is smaller (about 1/4? in diameter). Thin Ethernet coaxial cable is RG-58. With Thinnet cable, you use BNC connectors to attach stations to the network. It is beyond my province to settle the long-standing argument over the meaning of the abbreviation BNC. BNC could mean BayoNet Connector, Bayonet Nut Connector, or British Navel Connector. But it is most commonly referred to as the Bayonet Neill- Concelman connector. What is relevant is that the BNC connector locks securely with a quartertwist motion. The BNC connector can be attached to a cable in two ways. The first is with a crimper, which looks like funny pliers and has a die to crimp the connector. Pressing the levers crimps the connector to the cable. Choice number two is a screw-on connector, which is very unreliable. If at all possible, avoid the screw-on connector!

 

Using F-Type Connectors

The F-Type connector is a threaded, screw-on connector that differs from the BNC connector of early Ethernet mainly in its method of device attachment. Additionally, as alluded to earlier, you typically find F-Type connectors with 75ohm coaxial media and BNC connectors with 50ohm applications. As with most other coax applications, the F-Type connector uses the center conductor of the coaxial cable as its center connecting point. The other conductor is the metal body of the connector itself, which connects to the shield of the cable.

Twisted-Pair Cable

Twisted-pair cable consists of multiple, individually insulated wires that are twisted together in pairs. Sometimes a metallic shield is placed around the twisted pairs. Hence, the name shielded twisted-pair (STP). (You might see this type of cabling in Token Ring installations.) More commonly, you see cable without outer shielding; it’s called unshielded twisted-pair (UTP). UTP is commonly used in twisted-pair Ethernet (10Base-T, 100Base-TX, etc.), star-wired networks. When electromagnetic signals are conducted on copper wires that are in close proximity (such as inside a cable), some electromagnetic interference occurs. In this scenario, this interference is called crosstalk. This cable type is the most common today. It is popular for several reasons:

• It’s cheaper than other types of cabling.
• It’s easy to work with.
• It permits transmission rates considered impossible 10 years ago.

UTP cable is rated in the following categories:

• Category 1 Two twisted wire pairs (four wires). Voice grade (not rated for data communications). The oldest UTP. Frequently referred to as POTS, or plain old telephone service. Before 1983, this was the standard cable used throughout the North American telephone system. POTS cable still exists in parts of the Public Switched Telephone Network (PSTN). Supports signals limited to a frequency of 1MHz.
• Category 2 Four twisted wire pairs (eight wires). Suitable for up to 4Mbps, with a frequency limitation of 10MHz.
• Category 3 Four twisted wire pairs (eight wires) with three twists per foot. Acceptable for transmissions up to 16MHz. A popular cable choice since the mid-1980s, but now limited mainly to telecommunication equipment.
• Category 4 Four twisted wire pairs (eight wires) and rated for 20MHz.
• Category 5 Four twisted wire pairs (eight wires) and rated for 100MHz .
• Category 5e Four twisted wire pairs (eight wires) and rated for 100MHz, but capable of handling the disturbance on each pair caused by transmitting on all four pairs at the same time, which is needed for Gigabit Ethernet.
• Category 6 Four twisted wire pairs (eight wires) and rated for 250MHz. Became a standard in June 2002.

Connecting UTP

Clearly, a BNC connector won’t fit easily on UTP cable, so you need to use an RJ (Registered Jack) connector. You are probably familiar with RJ connectors. Most telephones connect with an RJ-11 connector. The connector used with UTP cable is called RJ-45. The RJ-11 has four wires, or two pairs, and the network connector RJ-45 (also known as an 8P8C connector when referring to the plug instead of the jack) has four pairs, or eight wires

Signaling Methods

The amount of a cable’s available bandwidth (overall capacity, such as 10Mbps) that is used by each signal depends on whether the signaling method is baseband or broadband. With baseband, the entire bandwidth of the cable is used for each signal (using one channel). It is typically used with digital signaling. With broadband, on the other hand, the available bandwidth is divided into discrete bands. Multiple signals can then be transmitted within these different bands. Some form of tuning device, or demodulator, is required to choose the specific frequency of interest, as opposed to baseband receiving circuitry, which can be hardwired to a specific frequency.

Ethernet Cable Descriptions

Ethernet cable types are described using a code that follows this format: N<Signaling>-X. Generally speaking, N is the signaling rate in megabits per second, and <Signaling> is the signaling type, which is either base or broad (baseband or broadband). X is a unique identifier for a specific Ethernet cabling scheme. Let’s use a generic example: 10BaseX. The two-digit number 10 indicates that the transmission speed is 10Mb, or 10 megabits. The value X can have different meanings. For example, the 5 in 10Base5 indicates the maximum distance that the signal can travel—500 meters. Similarly, there are also standards for 100Base, 1000Base, and 10GBase cabling. Let’s take a closer look at these standards:

• 100Base-TX As network applications increased in complexity, so did their bandwidth requirements. Ten-megabit technologies were too slow. Businesses were clamoring for a higher speed standard so that their data could be transmitted at an acceptable rate of speed. A 100- megabit standard was needed. Thus the 100Base-TX standard was developed. The 100Base-TX standard is a standard for Ethernet transmission at a data rate of 100Mbps. This Ethernet standard is also known as Fast Ethernet. It uses two UTP pairs (four wires) in a minimum of Category 5 UTP cable.
• 1000Base-TX 1000Base-TX, most commonly known as Gigabit Ethernet, allows 1000Mbps throughput on standard twisted-pair, copper cable (rated at Category 5e or higher).
• 1000Base-SX The implementation of Gigabit Ethernet running over multimode fiber-optic cable (instead of copper, twisted-pair cable) and using short wavelength laser.
• 1000Base-LX The implementation of Gigabit Ethernet over single-mode and multimode fiber using long wavelength laser.
• 1000Base-CX An implementation of Gigabit Ethernet over balanced, 150ohm copper cabling and uses a special 9-pin connector known as the High Speed Serial Data Connector (HSSDC).
• 10GBase-SR An implementation of 10 Gigabit Ethernet that uses short wavelength lasers at 850 nanometers(nm) over multimode fiber. It has a maximum transmission distance of between 2 and 300 meters, depending on the size and quality of the fiber.
• 10GBase-LR An implementation of 10 Gigabit Ethernet that uses long wavelength lasers at 1310 nm over single-mode fiber. It also has a maximum transmission distance between 2 meters and 10 kilometers, depending on the size and quality of the fiber.
• 10GBase-ER An implementation of 10 Gigabit Ethernet running over singlemode fiber. It uses extra long wavelength lasers at 1550 nm. It has the longest transmission distances possible of the 10-Gigabit technologies: anywhere from 2 meters up to 40 kilometers, depending on the size and quality of the fiber used.

IEEE Standard 1394 (FireWire)

One unique cabling type that is used in a limited sense is IEEE standard 1394, more commonly known as FireWire (or as Sony calls it, i.Link). Developed by Apple Computer, FireWire runs at 100, 200, 400Mbps (800Mbps in the 1394b standard), but in its standard mode it has a cable length limitation of 15 feet (4.5 meters), which limits it to specialized applications like data transfer between two computers located in close proximity or data transfer between a computer and another device (like an MP3 player). FireWire uses two types of connectors: the 6 pin and the 4 pin. The 6-pin connector is for devices that need to be powered from the computer. FireWire cables with the 6-pin connector contain two pairs (four conductors) of copper wire for carrying data and one pair for powering devices, all within a common, braided metal shield. Cables using the 4-pin connector are for data transfer only, and they contain only the four conductors for data, none for power.

Universal Serial Bus (USB)

Over the past few years, computer peripherals have been moving away from parallel or serial connection and to a new type of bus. That bus is the Universal Serial Bus (USB). The built-in serial bus of most motherboards generally offers a maximum of 2 external interfaces for connectivity to a PC, although add-on adapters can take that count up to as many as 16 serial interfaces. USB, on the other hand, can connect a maximum of 127 external devices. Also, USB is a much more flexible peripheral bus than either serial or parallel. USB supports connections to printers, scanners, and many other input devices (such as keyboards, joysticks, and mice). Although you can connect up to 127 devices, it is impractical in reality. Most computers with USB interfaces will support around 12 USB devices.

Fiber-Optic Cable

Because fiber-optic cable transmits digital signals using light impulses rather than electricity, it is immune to Electromagnetic Interference (EMI) and Radio Frequency Interference (RFI). Light is carried on either a glass or a plastic core. Glass can carry the signal a greater distance, but plastic costs less. Regardless of which core is used, the core is surrounded by a glass or plastic cladding, which is more glass or plastic with a different index of refraction that refracts the light back into the core. Around this is a layer of flexible plastic buffer. This can be then wrapped in an armor coating (where necessary), typically Kevlar, and then sheathed in PVC or plenum. The cable itself comes in two different styles: single-mode fiber (SMF) and multimode fiber (MMF). The difference between single-mode fibers and multimode fibers is in the number of light rays (and thus the number of signals) they can carry. Generally speaking, multimode fiber is used for shorter-distance applications and single-mode fiber for longer distances. If you happen to come across a strand of fiber in the field and want to know if it’s single mode or multimode, here are some general guidelines. First of all, if it’s got a yellow jacket, it’s probably single mode. If it’s got an orange jacket, it’s most likely multimode. Also, check the writing on the cable itself. You’ll find a number like 62.5/125. These are the outside diameters of the core and the cladding (respectively). If the first number is a 8, 9, or 10, it is most likely a single mode. On the other hand, if the numbers read as before (62.5/125), it’s most likely a multimode strand of fiber. Use these two tips to help you identify that errant strand of fiber. Although fiber-optic cable may sound like the solution to many problems, it has pros and cons just as the other cable types.

Here are the pros:

• Is completely immune to EMI or RFI
• Can transmit up to 40 kilometers (about 25 miles)

Here are the cons of fiber-optic cable:

• Is difficult to install
• Requires a bigger investment in installation and materials

Fiber-Optic Connectors

Fiber-optic cables can use a myriad different connectors, but the two most popular and recognizable are the straight tip (ST) and subscriber (or square) connector (SC) connectors. The ST fiber-optic connector, developed by AT&T, was one of the most widely used fiber-optic connectors. It uses a BNC attachment mechanism similar to the Thinnet connection mechanism, which makes connections and disconnections relatively easy. Its ease of use is one of the attributes that makes this connector so popular. Notice the BNC attachment mechanism. The SC connector (sometimes known also as a square connector) is another type of fiber-optic connector.

SC connectors are latched connectors. This latching mechanism holds the connector in securely while in use and prevents it from just falling out. SC connectors work with either single-mode or multimode optical fibers, and they will last for around 1000 matings. They are seeing increased use but aren’t as popular as ST connectors for LAN connections.

Small Form Factor Fiber-Optic Connectors

One of the more popular styles of fiber-optic connectors is the small form factor (SFF) style of connector. SFF connectors allow more fiber-optic terminations in the same amount of space over their standard-sized counterparts. The two most popular are the mechanical transfer registered jack (MT-RJ or MTRJ), designed by AMP, and the Local Connector (LC), designed by Lucent.

MT-RJ

The MT-RJ fiber-optic connector was the first small form factor fiber-optic connector to see widespread use. It is one-third the size of the SC and ST connectors it most often replaces. It had the following benefits:

• Small size
• TX and RX strands in one connector
• Keyed for single polarity
• Pre-terminated ends that require no polishing or epoxy
• Easy to use

LC

Local Connector is a newer style of SFF fiber-optic connector that is overtaking MT-RJ as a fiber-optic connector. It is especially popular for use with Fiber Channel adapters and Gigabit Ethernet adapters. It has similar advantages to MT-RJ and other SFF-type connectors but is easier to terminate. It uses a ceramic insert as standard-sized fiber-optic connectors do.

 

Common Network Connectivity Devices

Because these devices connect network entities, they are known as connectivity devices:

• The network interface card (NIC)
• The hub
• The switch
• The bridge
• The router
• The gateway
• Other devices

NIC

The network interface card (NIC), as its name suggests, is the expansion card you install in your computer to connect, or interface, your computer to the network. NIC cards generally all have one or two light emitting diodes (LEDs) that help in diagnosing problems with their functionality. If there are two separate LEDs, one of them may be the Link LED, which illuminates when proper connectivity to an active network is detected. This often means that the NIC is receiving a proper signal from the hub/MAU or switch, but it could indicate connectivity to and detection of a carrier on a coax segment or connectivity with a router or other end device using a crossover cable. The other most popular LED is the Activity LED. The Activity LED will tend to flicker, indicating the intermittent transmission or receipt of frames to or from the network.

Hub

A hub is the device that connects all the segments of the network together. Every device in the network connects directly to the hub through a single cable. Any transmission received on one port will be sent out all the other ports in the hub, including the receiving pair for the transmitting device, so that CSMA/CD on the transmitter can monitor for collisions. So, if one station sends it, all the others receive it; but based on addressing in the frame, only the intended recipient listens to it. This is to simulate the physical bus that the CSMA/CD standard was based on. It’s why we call the use of a hub in an Ethernet environment a physical star/logical bus topology. It is important to note that hubs are nothing more than glorified repeaters, which are incapable of recognizing frame boundaries and data structures; that’s why they act with such a lack of intelligence. A broadcast sent out by any device on the hub will be propagated to all devices connected to the hub. Any two or more devices connected to the hub have the capability of causing a collision with each other, just as in the case of a physical bus.

Switch

Like a hub, a switch connects multiple segments of a network together, with one important difference. Whereas a hub sends out anything it receives on one port to all the others, a switch recognizes frame boundaries and pays attention to the destination MAC address of the incoming frame as well as the port on which it was received. The benefit of a switch over a hub is that the switch increases performance because it is able to support full wire speed on each and every port with a nonblocking backplane, meaning the electronics inside the switch are at least equivalent in speed to the sum of the speeds of all ports.

Bridge

A bridge, specifically a transparent bridge, is a network device that connects two similar network segments together. The primary function of a bridge is to keep traffic separated on both sides of the bridge. Traffic is allowed to pass through the bridge only if the transmission is intended for a station on the opposite side. The main reasons for putting a bridge in a network are to connect two segments together and to divide a busy network into two segments.

Router

A router is a network device that connects multiple, often dissimilar, network segments into an internetwork. The router, once connected, can make intelligent decisions about how best to get network data to its destination based on network performance data that it gathers from the network itself.

Gateways

A gateway is any hardware and software combination that connects dissimilar network environments. Gateways are the most complex of network devices because they perform translations at multiple layers of the OSI model. For example, a gateway is the device that connects a LAN environment to a mainframe environment. The two environments are completely different. LAN environments use distributed processing, baseband communications, and the ASCII character set. Mainframe environments use centralized processing, broadband and baseband communications, and the EBCDIC character set. Each of the LAN protocols is translated to its mainframe counterpart by the gateway software.

Other Devices

In addition to these network connectivity devices, there are several devices that, while maybe not directly connected to a network, participate in moving network data:

• Modems
• ISDN terminal adapters
• Wireless access points
• CSU/DSUs
• Transceivers (media converters)
• Firewalls

Modems

A modem is a device that modulates digital data onto an analog carrier for transmission over an analog medium and then demodulates from the analog carrier to a digital signal again at the receiving end. The term modem is actually an acronym that stands for  MOdulator/DEModulator. When we hear the term modem, three different types should come to mind:

• Traditional (POTS)
• DSL
• Cable

Traditional (POTS)

These modems convert the signals from your computer into signals that travel over the plain old telephone service (POTS) lines.

DSL

In addition, you can make regular phone calls while online. DSL uses higher frequencies (above 3200Hz) than regular voice phone calls use, which provides greater bandwidth (up to several megabits per second) than regular POTS modems provide while still allowing the standard voice frequency range to travel at its normal frequency to remain compatible with traditional POTS phones and devices, an advantage over ISDN. DSL “modems” are the devices that allow the network signals to pass over phone lines at these higher frequencies.

Cable

Cable modems connect an individual PC or network to the Internet using your cable television cable. The cable TV companies use their existing cable infrastructure to deliver data services on unused frequency bands.

ISDN Terminal Adapters

Integrated Services Digital Network (ISDN) is another form of high-speed Internet access. It delivers digital services (over 64Kbps channels) over conditioned telephone copper pairs. The device you must hook up to your computer to access ISDN services is properly known as an ISDN Terminal Adapter. It’s not a modem in the truest sense of the word because a modem changes from digital to analog for transmission. An ISDN TA doesn’t change from digital to analog. It just changes between digital transmission formats.

Wireless Access Points (WAPs)

A wireless access point (WAP) allows mobile users to connect to a wired network wirelessly via radio frequency technologies. WAPs also allow wired networks to connect to each other via wireless technologies. Essentially, they are the wireless equivalent of a hub or a switch in that they can connect multiple wireless (and often wired) devices together to form a network.

CSU/DSUs

The Channel Service Unit/Data Service Unit (CSU/DSU) is a common device found in equipment rooms when the network is connected via a T-series data connection or other digital serial technology (e.g., a T1 or Digital Data Server [DDS]). It is essentially two devices in one

that are used to connect a digital carrier (the T-series or DDS line) to your network equipment (usually to a router). The Channel Service Unit (CSU) terminates the line at the customer’s premises. It also provides diagnostics and remote testing, if necessary. The Data Service Unit (DSU) does the actual transmission of the signal through the CSU. It can also provide buffering and data flow control.

Transceivers (Media Converters)

Another small device that is commonly seen on a network is the external transceiver (also known as a media converter). These are relatively simple devices that allow a NIC or other networking device to connect to a different type of media than it was designed for. Many NICs have special connectors that will allow this, as do hubs and switches. For example, if you have a 100Base-TX switch and would like to connect it to another switch using fiber-optic cabling, you would connect a fiber transceiver to each switch’s transceiver port and then connect the two transceivers together with the appropriate fiber-optic cabling.

Firewalls

A firewall is probably the most important device on a network if that network is connected to the Internet. Its job is to protect LAN resources from attackers on the Internet. Similarly, it can prevent computers on the network from accessing various services on the Internet. It can be used to filter packets based on rules that the network administrator sets. These rules state what kinds of information can flow into and out of a network’s connection to the Internet.

The OSI Model

Open Systems Interconnect (OSI) model

How data travels through the OSI model layers

The OSI Model’s Lower Layers

• The Physical Layer
• The Data Link Layer

– Media Access Control (MAC)

– Logical Link Control (LLC)

Sublayers of the Data Link Layer

IEEE 802 Networking Standards

802.1 LAN/MAN Management (and Media Access Control Bridges)

802.2 Logical Link Control

802.3 CSMA/CD

802.4 Token Bus

802.5 Token Ring

802.6 Distributed Queue Dual Bus (DQDB) Metropolitan Area

Network (MAN)

802.7 Broadband Local Area Networks

802.8 Fiber Optic LANs and MANs

802.9 Integrated Services (IS) LAN Interface

The OSI Model’s Middle Layers

• The Network Layer
• The Transport Layer

The OSI Model’s Upper Layers

• The Session Layer
• The Presentation Layer
• The Application Layer

Networking Protocols

• TCP/IP
• IPX/SPX
• Net BEUI
• AppleTalk

IPX Network Address

 

TCP/IP Fundamentals

Main Topics

• Introducing TCP/IP
• The Transmission Control Protocol
• The Internet Protocol
• The Application Protocols
• Ports and Sockets Explained
• Understanding IP addresses
• Name Resolution Methods
• Configuring TCP/IP on Windows Workstations

A comparison of the 7-layer OSI layer, the 4-layer DoD model, and how TCP/IP maps to each model

 

A datagram with its TCP header

 

A datagram with TCP & IP headers

 

The Application Protocols

• Simple Network Management Protocol (SNMP)
• File Transfer Protocol (FTP)
• Trivial File Transfer Protocol (TFTP)
• Simple Mail Transfer Protocol (SMTP)
• Post Office Protocol (POP)
• Internet Message Access Protocol (IMAP)
• Telnet
• Internet Control Message Protocol (ICMP)
• Hypertext Transfer Protocol (HTTP)
• Address Resolution Protocol (ARP)
• Network Time Protocol (NTP)

Port Numbers for Common Protocols

• UDP Port 15 NETSTAT
• TCP Ports 20 & 21 FTP data and control
• TCP Port 22 SSH
• TCP Port 23 Telnet
• TCP Port 25 SMTP
• TCP & UDP Port 53 DNS
• UDP Port 69 TFTP
• TCP Port 70 Gopher
• TCP Port 79 Finger
• TCP & UDP Port 80 HTTP
• TCP Port 110 POP3
• UDP Port 111 RPC
• TCP Port 119 NNTP
• TCP Port 123 NTP
• UDP Port 137 NetBIOS name server
• TCP Port 143 IMAP4
• UDP Port 161 SNMP network monitor
• TCP Port 443 HTTPS

The IP address structure

 

Name Resolution Methods

• Internet Domain Organization
• Using HOSTS
• Using DNS
• Using WINS

TCP/IP Utilities

Main Topics

• Using the Address Resolution Protocol (ARP)
• Using netstat
• The nbtstat Utility
• The File Transfer Protocol (FTP) Utility
• The Ping Utility
• The winipcfg and ipconfig Utilities
• The tracert Utility
• The Telnet Utility
• The nslookup utility

Address Resolution Protocol (ARP)

• The ARP table in Windows is a list of TCP/IP addresses and their corresponding MAC addresses

ARP Switches

• -a
• -g
• -s
• -d

netstat

• Shows incoming and outgoing connections on the computer it is run on.
• Shows packet statistics.

netstat Switches

• -a
• -e
• -r
• -s
• -n
• -p

nbtstat

• Track NetBIOS over TCP/IP statistics
• Show the details of incoming and outgoing NetBIOS over TCP/IP connections
• Resolve NetBIOS names

nbstat Switches

• -a
• -A
• -c
• -n
• -r
• -R
• -S
• -s

FTP Utility

• Used to transfer files to or from another computer
• Navigation Commands:

– ls (lists the files and folders in a directory)

– cd (changes directories)

– pwd (print working directory)

– lcd (changes local directories)

The Ping Utility

Is used

• To find out if you can reach a host
• To find out if a host is responding

Syntax is

• Ping <hostname or IP address>

winipcfg and ipconfig

• Can be used to:

– Show current IP address

– Release IP address

– Renew IP address

– View DHCP information

nslookup Utility

• Used to query a name server and find out which name resolves to which IP address

Major Network Operating Systems

Main Topics

• Microsoft Windows
• Novell Netware
• UNIX/Linux
• Macintosh

Microsoft Windows

Features

• Client Support
• Interoperability
• Authentication
• File And Print Services
• Application Support
• Security

Windows Features

• The Windows Interface
• Third-Party Support

Interoperability

• Gateway Services for NetWare (GSNW)
• Client Services for NetWare (CSNW)
• File and Print Services for NetWare (FPNW)

Novell NetWare

Features

• Client Support
• Interoperability
• Authentication
• Directory Structure
• File and Print Services
• Application Support
• Security

Features of NetWare

• The directory service (NDS)
• The simple user interface
• Fairly minimal hardware requirements
• Scalable hardware support
• Third-party support
• Interoperability with many types of computer systems

Interoperability

• Windows 95/98/Me
• Windows NT/2000/XP
• Mac OS
• VMS
• OS/400
• UNIX
• OS/2

Authentication

All NetWare versions since version 4.0 use Novell Directory Services (NDS) for resource access and authentication.

There are three main types of directory services for NetWare:

• Bindery
• Novell Directory Services (NDS)
• EDirectory

Unix Flavors

• Linux
• SCO Unix
• Solaris Unix

UNIX/Linux

Features

• Client Support and Interoperability
• Authentication
• File And Print Services
• Application Support
• Security

Macintosh

Features

• Client Support
• Interoperability
• Authentication
• File and Print Services
• Application Support
• Security

Network Installations & Upgrades

Main Topics

• Before You Install New Hardware or Software
• Network Components
• Network Connectors
• Installing a Network Interface Card (NIC)
• Workstation Configuration
• Network Installation Tools

Before Installing New Hardware or Software

• Standard Operating Procedures
• Environmental Issues
• Error Messages and Log Files
• Current Configuration and Baselines
• Other Documentation

Standard Operating Procedures (SOPs)

• Internet access
• Printing
• Storage allocation
• E-mail usage
• User administration

Naming Conventions

• Servers
• Printers
• User accounts
• Group accounts
• Test and service accounts

Environmental Issues

• Power problems
• ESD problems
• EMI problems
• RFI problems
• Climate problems

Additional Information Sources

• Error Messages and Log Files
• Current Configuration and Baselines
• Other Documentation:

– README files

– Manufacturer’s website or CDs

Windows Event Viewer

• Log files

Network Components

• Patch Panel
• Repeater
• Hub
• Bridge, Router, & Brouter
• The Network Interface Card (NIC)
• The Print Server
• The Disk Subsystem
• Peripherals

Patch Panel

• Upgrading is easier.
• Troubleshooting is easier.
• You can avoid physical damage to the cable since it isn’t necessary to move it when you upgrade the network.

Network Connectors

• D-type Connectors
• BNC Connectors
• RJ Connectors
• The IBM Data Connector

Configuring the NIC

• Jumpers
• DIP switches
• EEPROM
• Plug and Play

Workstation Configuration

• Connecting a Windows 9x or 2000 workstation to:

– Windows NT/2000 Server

– NetWare

– Unix/Linux

– Macintosh

Network Installation Tools

• Wire Crimper
• Media Testing Tools

– Wire Map Testers

– Continuity Testers

– Tone Generators

– Optical Loss Test Set

– Multifunction Cable Testers

• Punchdown Tool

WAN & Remote Access

Main Topics

• Remote Access Connection Configuration Requirements
• Remote Access Connection Methods
• Remote Access Protocols

Remote Access Connection Configuration Requirements

• Hardware Requirements

– Configuring internal modems

– Configuring external modems

• Software Requirements

COM Port IRQ and Default I/O Addresses

 

Remote Access Connection Methods

• The Public Switched Telephone Network (PSTN)
• Integrated Services Digital Network (ISDN)
• Other Digital Options

– DSLs

– T-carrier circuits

POTS

Pros

• It is inexpensive & easy to set up.
• There are no LAN cabling costs.
• Connections are available in many countries throughout the world.

Con

• Limited bandwidth

ISDN

Pros

• Fast connection.
• Higher bandwidth than POTS.
• No conversion from digital to analog.

Con

• It’s more expensive than POTS.
• Specialized equipment is required at both ends.
• Not all equipment can connect to ISDN.

Other Digital Options

• xDSL
• Frame relay
• T-carrier

Remote Access Protocols

• Serial Line Internet Protocol (SLIP)
• Point-to-Point Protocol (PPP)
• Point-to-Point Tunneling Protocol (PPTP)
• Layer-2 Tunneling Protocol (L2TP)
• Windows Remote Access Services (RAS)

PPTP Disadvantages

• PPTP is not available on all types of servers.
• PPTP is not a fully accepted standard.
• PPTP is more difficult to set up than PPP.
• Tunneling can reduce throughput

Network Access & Security

Main Topics

• Accessing Network Resources
• Client Selection
• Managing User Account and Password Security
• Using Firewalls
• Attack and Defense
• DoD Security Standards
• Understanding Encryption
• Security Policies

Client Selection and Installation

• Windows 9x and NT/2000 Client
• Netware Client
• UNIX Client
• Selecting a Primary Client

Managing User Accounts

• Network Resource-Sharing Security Models

– Share-Level Security

– User-Level Security

• Managing Accounts

– Disabling Accounts

– Anonymous Accounts

– Limiting Connections

– Maintenance Accounts

Managing Passwords

• Strong Passwords
• NOS Password Management Features

– Automatic Account Lockouts

– Password Expirations

– Unique Passwords

– Password Histories

Firewall Technologies

• Access Control Lists (ACL)
• The Demilitarized Zone (DMZ)
• Protocol Switching
• Dynamic Packet Filtering
• Proxy Servers

– IP Proxy

– Web Proxy

– FTP Proxy

– SMTP Proxy

Security Protocols

• L2TP
• IPSec
• SSL
• Kerberos

Firewall Operating Systems

• UNIX Operating System
• NetWare
• Windows NT/2000/2003
• The Black Box

Common Attacks

• IP Spoofing
• The Ping of Death
• WinNuke
• SYN Flood

Intrusion Detection and Defense Techniques

• Active Detection
• Passive Detection
• Proactive Defense

DoD Security Standards

• Trusted Computer System
• Trusted Network Interpretation
• Certified Operating Systems and Networks

Understanding Encryption

• Uses for encryption
• How encryption works
• Encryption keys

– Private Key Encryption

• The Data Encryption Standard (DES)
• Skipjack and Clipper

– Public Key Encryption

• RSA Data Security
• retty Good Privacy (PGP)

Security Policies

• Security Audit
• Clean Desk Policy
• Recording Equipment
• Other Common Security Policies
• Breaking Policy
• The Exit Interview

Fault Tolerance & Disaster Recovery

Main Topics

• Assessing fault tolerance and disaster recovery needs
• Power management
• Disk system fault tolerance
• Backup considerations
• Virus protection
• Software patches

Assessing Fault Tolerance and Disaster Recovery

• Hot Sites

– Clustering Technology

– Failover Clustering

– True Clustering

• Warm Site
• Cold Site

Power Management

• Battery Backup Systems
• Standby Power Supplies (SPS)
• Uninterruptible Power Supplies (UPS)
• Line Conditioners

Disk System Fault Tolerance

• Disk Mirroring
• Disk Duplexing
• Disk Striping

Disk Mirroring

• The drives do not have to be identical, but it helps.
• Both drives must have the same amount of free space to allow a mirror to be formed.

– If you have 4GB drives; one has 3GB free, the other has 2GB free. You can create one 2GB mirrored system.

Disk Duplexing

· Disk duplexing saves data to a mirror drive.

· The major difference between duplexing and mirroring is that duplexing uses two separate disk controllers (one for each disk).

Disk Striping

· Disk striping breaks up the data to be saved to disk into small portions and sequentially writes the portions to all disks simultaneously in small areas called stripes.

-     These stripes maximize performance because all the read/write heads are working constantly.

Redundant Array of Inexpensive (or Independent) Disks (RAID)

· RAID is a technology that uses an array of less-expensive hard disks instead of one enormous hard disk and that provides several methods for writing to those disks to ensure redundancy.

Redundant Array of Inexpensive (or Independent) Disks (RAID)

· RAID 0 (commonly used)

· RAID 1 (commonly used)

· RAID 2

· RAID 3 (commonly used)

· RAID 4

· RAID 5 (commonly used)

Backup Considerations

· A backup plan includes information such as:

- What to back up

- Where, when and how often to back up

- Who should be responsible for backups

- Where media should be stored

- How often to test backups

- The procedure to follow in case of data loss

Backup Media

· Small Capacity Removable Disks

· Large Capacity Removable Disks

· Removable Optical Disks

· Magnetic Tape

Backup types

· ? Full

· ? Differential

· ? Incremental

Virus Protection

· Types of Viruses

· Macro Viruses

· Boot Sector Viruses

· Updating Antivirus Components

· Antivirus Engine

· Definition Files

· Virus Scanning

· On-Demand

· On-Access

· Emergency Scans

Software Patches

· Is it necessary?

· Where to get patches

· How to apply patches

Network Troubleshooting

Main Topics

· Narrowing Down the Problem

· Troubleshooting Steps

· Troubleshooting Resources

· Troubleshooting Tips

Narrowing Down the Problem

· The following are items which may come as “simple” solutions to larger problems:

· Correct login procedure and rights

· Link lights and collision lights

· Power switch

· Operator error

· Is it a workstation or server problem?

· Which segments of the network are affected?

· Cabling Issues

Troubleshooting Steps

· Establish symptoms

· Identify the affected area

· Establish what has changed

· Select the most probable cause

· Implement a solution

· Test the results

· Recognize the potential effects of the solution

· Document the solution

The Troubleshooter’s Resources

· Log Files

· Netware Log Files

· console.log

· abend.log

· sys$log.err

· Windows NT and Later Log Files

· The system log

· The security log

· The application log

· Manufactures’ Troubleshooting Resources

· README files

· Telephone Support

· Technical Support CDs

· Technical Support Websites

· Hardware Troubleshooting Tools

· Crossover Cables

· Hardware Loopback

· Tone Generator and Tone Locator

· Software Troubleshooting Tools

· Protocol Analyzer

· Performance Monitoring Tools

Troubleshooting Tips

· Don’t overlook the small stuff

· Prioritize your problems

· Check the software configuration

· Don’t overlook physical conditions

· Don’t overlook cable problems

· Check for viruses

· Last-in, first-out

· Change only one thing at a time