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What is CDDi?

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βˆ™ 2009-05-24 09:45:40

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For a local area network (LAN), CDDI (Copper Distributed Data Interface) is a standard for data transmission based on FDDI (Fiber Distributed Data Interface) that uses shielded twisted-pair (STP) or unshielded twisted pair (UTP) copper wire instead of fiber optic lines. CDDI supports a dual-ring capacity of 200 Mbps. CDDI's maximum distance is up to 200 meters, which is much shorter than FDDI. CDDI is defined by the American National Standards Committee X3-T9.5 and conforms to the Open Systems Interconnection (OSI) model of functional layering. CDDI is officially named the Twisted-Pair Physical Medium Dependent (TP-PMD) standard and is also referred to as Twisted Pair Distributed Data Interface (TP-DDI).

2009-05-24 09:45:40
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Q: What is CDDi?
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What is FDDI Explain in detail?

Fiber distributed data interface (FDDI), which is an optical data communication standard used for long distance networks provides communication with fiber optic lines up to 200 kilometers at a speed of 100 megabit per second (Mbps).It should be noted that relatively recently, a related copper specification, called Copper Distributed Data Interface (CDDI) has emerged to provide 100-Mbps service over copper. CDDI is the implementation of FDDI protocols over twisted-pair copper wire.FDDI uses a dual-ring architecture with traffic on each ring flowing in opposite directions (calledcounter-rotating). The dual-rings consist of a primary and a secondary ring. During normal operation, the primary ring is used for data transmission, and the secondary ring remains idle and available for backup. The primary purpose of the dual rings, as will be discussed in detail later in this chapter, is to provide superior reliability and robustness. FDDI was later extended to FDDI-2 for long distance voice and multimedia communication.

Advantages and disadvantages of the Fiber Distributed Data Interface FDDI?

FDDI Advantages: ~Supports real time allocation of network bandwidth. ~Supports a lot of different types of network traffic. ~Is fault-tolerant because it uses dual fiber cables. If one cable fails FDDI moves the data to the other dual cable. FDDI Disadvantages: ~It's expensive ~There is always a chance of multiple ring failures and as the ring grows, that chance increases. ~It's not used frequently due to cost, companies prefer to use copper (CDDI) if they are taking the ring approach.

What are the components of LAN and functions?

Logical or physical network topologies:1) A Star network is defined as a network where all computers connect to a central computer or server. It looks like this:2) A bus network is defined as a network where all computers share a central backbone to connect all computers together. It looks like this:3) A mesh network is defined as a network where all computers are connected to each other. It looks like this:Remember that while the figure depicting a mesh network is very commonly used, it is not accurate. Computers are rarely connected directly to each other. They usually go through an intermediate network device. Correctly depicted, the devices connecting to each other should be network devices such as switches or routers. Indeed, some form of mesh or partial mesh between network devices is very common in enterprise networks.4) A ring network is defined as a network where one computer connects to another to form a ring. It looks like this:Features of 802.x standards and FDDI (Fiber Distributed Data Interface) networking technologies1) 802.2 LLC [Logical Link Control (IEEE 802.2, ISO, OSI)]Speed: speed depends on the networkAccess method: Used with CSMA/CD and token passing.Topology: Used in Ethernet and Token-Ring networks.Media: Used with ethernet and token-ring, defines putting the signal on the media.2)802.3 EthernetSpeed: Speed ranges from 10 MBPS to 10 GBPS.Access method: CSMA/CDTopology: Commonly used in bus and star configurations.Media: Either copper or fiber optic based media.3) 802.5 Token RingSpeed: 4 MBPS to 1 GBPSAccess method: Token passingTopology: Star (even though it says Ring, its physical topology is a star)Media: IBM "Type-1" Shielded Twisted Pair (copper)4)802.11x wirelessSpeed: 1 MBPS to 108 MBPSAccess method: CSMA/CATopology: Wireless - uses wireless access-points to connect users.Media: Wireless - radio frequencies5) FDDISpeed: 100 to 200 MBPSAccess method: Token passingTopology: Token RingMedia: Fiber or copper (called CDDI if copper is used, and not FDDI)Cable Standards Characteristics1) 10BASE-TSpeed: 10 MBPSLength: 100 metersTopology: EthernetCable type: CAT 3 or better2) 10BASE-FLSpeed: 10 MBPSLength: 2000 metersTopology: EthernetCable type: Fiber optic3) 100BASE-TXSpeed: 100 MBPS (200 mbps - full duplex)Length: Network segments limited to 100 metersTopology: EthernetCable type: cat 5 cable4) 100BASE-FXSpeed: 100 MBPSLength: 400 meters half duplex or 2000 meters for full duplexTopology: EthernetCable type: Fiber optic5)1000BASE-TSpeed: 1 GBPSLength: each network segment is limited to 100 meters.Topology: EthernetCable type: Cat 5e ("category 5 enhanced") or cat 6 cable.6) 1000BASE-CXSpeed: 1 GBPSLength: 25 meters per network segmentTopology: EthernetCable type: Copper based - STP (shielded twisted pair)7) 1000BASE-SXSpeed: 1 GBPSLength: 550 meters.Topology: EthernetCable type: Multi-mode fiber optics with 0.85 micrometer core.8) 1000BASE-LXSpeed: 1 GBPSLength: 5000 meters.Topology: EthernetCable type: Single mode fiber optic cable.9) 10 GBASE-SRSpeed: 10 GBPSLength: 300 metersTopology: EthernetCable type: Multi-mode fiber optics.10) 10 GBASE-LRSpeed: 10 GBPSLength: 2000 metersTopology: EthernetCable type: Single-mode fiber optics. Used over dark fiber connected to SONET equipment.11) 10 GBASE-ERSpeed: 10 GBPSlength: 40,000 metersTopology: EthernetCable type: Uses either single or multi-mode fiber. Used over dark fiber connected to SONET equipment.Network DevicesHubsPurpose: A common connection point for devices in a network. Hubs are commonly used to connect segments of a LAN. A hub contains multiple ports. When a packet arrives at one port, it is copied to the other ports so that all segments of the LAN can see all packets. Not so common now.SwitchesPurpose: Similar to a hub, in that it provides a central connection between two or more computers on a network, but with some intelligence. They provide traffic control for packets Rather than forwarding data to all the connected ports, a switch forwards data only to the port on which the destination system is connected. It maintains a MAC address table for this purpose.BridgesPurpose: A Bridge is a networking device which connects multiple LANs and forwards or filters data packets between them based on their destination address. A bridge prevents unnecessary data from crossing connected networksRoutersPurpose: Routers are network devices that literally route data around the network. By examining data as it arrives, the router can determine the destination address for the data; then, by using tables of defined routes, the router determines the best way for the data to continue its journey. It connects networks together and routes information between them so that unnecessary data is not sent to the other networks by using the IP address. The function of a Router is to determine the next point a data packet needs to be forwarded to on to its destination.GatewaysPurpose: A gateway is a networking device which translates between two dissimilar protocols. A gateway links and translates between local area networks with different protocols. This makes it possible to receive different formatted data and translate to a format which your computer can understandCSU/DSU (Channel Service Unit / Data Service Unit)Purpose: A hardware device used to interface between a serial port and a digital circuit. Allows for the connection of networks far apart from each other. The function of a CSU/DSU is to act as a translator between the LAN data format and the WAN data formatNICs (Network Interface Card)Purpose: is a device which plugs into a computer and adapts the network interface to the appropriate standard. The NIC card is used to connect your computer to the networkISDN (Integrated Services Digital Network) adapterPurpose: A device which allows your computer to transmit over ISDN linesWAPs (Wireless Access Point)Purpose: is a transceiver or radio component in a wireless LAN that acts as the transfer point between wired and wireless signal and vice versaFeatures: Connects your wired and your wireless devices togetherFunctions: The function of a WAP is to connect your wireless devices to your wired network setupModemPurpose: is a device which enables a computer to transmit data over analogue telephone lines. Connects your computer to the internet using a modem (dial up account)FirewallsPurpose: a networking device, either hardware or software based, that controls access to your organization's network. It allows for control of administration on your network. The function of a Firewall is to prevent outside sources from connecting to your networksProtocols and StandardsEach and every Ethernet device interface to the network media (e.g., network adapter, port on a hub) has a unique MAC address, which is "burned" into the hardware when it is manufactured. MAC addresses uniquely identify each node in a network at the Media Access Control layer, the lowest network layer, the one that directly interfaces with the media, such as the actual wires in a twisted-pair Ethernet. In modern Ethernets the MAC address consists of six bytes which are usually displayed in hexadecimal; e.g., 00-0A-CC-32-FO-FDMAC addresses have two parts:1) the first half of the numbers (ie. 00-0A-CC) are the manufacture's code. You can use this code to find out who built the network interface card (NIC).2) The second half of the numbers (ie. 32-FO-FD) are the card's individual serial number.The OSI (Open Systems Interconnect) modelThere are seven layers of the OSI model. When a network devices wants to sent data over the network it begins at layer 7 and moves to layer 1 (encoding). From there it is sent to the receiving computer and the computer decodes that message by beginning at layer 1 and moving to layer 7. An easy way of remembering the layers is to keep this saying in mind "Please do not throw small people around."Layer 7ApplicationDescription: Applications and application interfaces for OSI networks. Provides access to lower layers and functions.Layer 6PresentationDescription: Negotiates syntactic representations and performs data transformations , e.g. compression and code conversion.Layer 5sessionDescription: Coordinates connection and interaction between applications, established dialog, manages and synchronizes data flow direction.Layer 4transportDescription: Ensures end-to-end data transfer and integrity across the network. Assembles packets for routing by layer 3.Layer 3networkDescription: Routes and relays data units across a network of nodes. Manages flow control and call establishment procedures.Layer 2data linkDescription: Transfers data units from one network unit to another over transmission circuit. Ensures data integrity between nodes.Layer 1PhysicalDescription: Delimits and encodes the bits onto the physical medium. Defines electrical, mechanical, and procedural formats.Layer 1 - Hubs, NICs and WAPsLayer 2 - Switches and bridgesLayer 3 - RoutersThe purpose of subnetting is to form smaller networks from one larger network. By doing this we end up getting a faster network because of reduced overhead (broadcast traffic).Static - A static IP address is a 32 bit number that is assigned to a computer or network device by a network administrator or Internet service provider (ISP) to be its permanent address on the network.Dynamic - An IP address that is assigned to a host (computer) when they connect to the network by a DHCP server. When the host disconnects, that IP address is once again free to give to another host. A dynamic IP address is not necessarily different every time a host connects.Self-assigned (APIPA (Automatic Private Internet Protocol Addressing)). A feature of Microsoft Windows, APIPA is a DHCP failover mechanism. With APIPA, DHCP clients can obtain IP addresses when DHCP servers are non-functional. APIPA exists in all popular versions of Windows except Windows NT. When a DHCP server fails, APIPA allocates addresses in the private range to Clients verify their address is unique on the LAN using ARP. When the DHCP server is again able to service requests, clients update their addresses automatically. In APIPA, all devices use the default network mask and all reside on the same subnet.VPN (Virtual Private Network) - A virtual private network (VPN) is a private communications network often used by companies or organizations, to communicate confidentially over a public network. VPN traffic can be carried over a public networking infrastructure (e.g. the Internet) on top of standard protocols, or over a service provider's private network with a defined Service Level Agreement (SLA) between the VPN customer and the VPN service provider. A VPN can send data (e.g., voice, data or video, or a combination of these media) across secured and encrypted private channels between two points.FirewallsIn today's network environments, firewalls are being used to protect systems from external as well as internal threats. Although firewalls initially became popular in corporate environments, many home networks with a broadband Internet connection now also implement a firewall to protect against Internet borne threats.Essentially, a firewall is an application, device, system, or group of systems that controls the flow of traffic between two networks. The most common use of a firewall is to protect a private network from a public network such as the Internet. However, firewalls are also increasingly being used as a means to separate a sensitive area of a private network from less-sensitive areas.At its most basic, a firewall is a device (it could be a computer system or a dedicated hardware device) that has more than one network interface and manages the flow of network traffic between those interfaces. How it manages the flow and what it does with certain types of traffic depends on its configuration.A basic firewall implementationStrictly speaking, a firewall performs no action on the packets it receives besides the basic functions just described. However, in a real-world implementation, a firewall is likely to offer other functionality, such as Network Address Translation (NAT) and proxy server services. Without NAT, any host on the internal network that needs to send or receive data through the firewall needs a registered IP address. Although there are such environments, most people have to settle for using a private address range on the internal network and therefore rely on the firewall system to translate the outgoing request into an acceptable public network address.Although the fundamental purpose of a firewall is to protect one network from another, you need to configure the firewall to allow some traffic through. If you don't need to allow traffic to pass through a firewall, you can dispense with it entirely and completely separate your network from others.LANs and WANs:A local area network (LAN) is a computer network that spans a relatively small area, such as a single office or office building, and typically offers high-speed communications. Most LANs are confined to a single building or group of closely located buildings. However, one LAN can be connected to other LANs over any distance via telephone lines, coaxial cable, satellite, etc. creating a WAN (see below). Most LANS of today utilize Ethernet and/or Wi-Fi connections.A wide area network (WAN) is a computer network that spans a relatively large geographical area. Typically, a WAN consists of two or more local-area networks (LANs). Computers connected to a wide-area network are often connected through public networks, such as the telephone system, leased lines (ISDN), satellite, microwave, or other connection methods. The connected LANS can be in another building, or as far away as in another country. The largest WAN in existence is the Internet.Wireless Networking:As the name implies, wireless networks allow computers to comunicate without the use of cables. The wi-fi standards are covered by IEEE 802.11x. The two most commonly used are IEEE 802.11b operating at 11Mbps and IEEE 802.11g operating at 54Mbps. 802.11 defines two pieces of equipment, a wireless station, which is usually a PC or a Laptop with a wireless network interface card (NIC), and a Wireless Access Point (WAP), which acts as a bridge between the wireless stations and Distribution System (DS) or wired networks. An 802.11 wireless network adapter can operate in two modes, Ad-Hoc and Infrastructure. In infrastructure mode, all your traffic passes through a wireless 'access point'. In Ad-hoc mode your computers talk directly to each other in a peer-to-peer mode and do not need an access point at all. To set up an Ad Hoc wireless network, all those who want to access it need to agree on a SSID and have an IP address in the same subnet.Bluetooth (IEEE 802.15.1), was originally developed by Ericsson in 1994 and later formalized by the Bluetooth Special Interest Group (SIG). It is named after King Harald Blatan (Bluetooth) of Denmark. It is a specification for wireless personal area networks that facilitate the exchange of data between electronic devices, such as mobile phones, PDAs, laptops, personal computers, printers and digital cameras. Due to hopping spread spectrum technique that changes its signal 1600 times per second, interference from other devices doesn't stop the transmission, although its speed may be slowed down.There are three Bluetooth power classes - class 1 (not very common; allows transmission distance of up to 100 meters); class 2 (the most common; allows transmission distance of 10 meters) and class 3 (very rare; allows transmission distance of about 10 cm with a maximum of 1 meter).Bluetooth technology is available in three versions, including 1.1 (allowing transmission data speeds of up to 1 Mbps in the); 1.2 (allows devices to be discovered more reliably, have better audio quality and better reliability under interference conditions) and 2.0 (allowing transmission data speeds of up to 3 Mbps with lower power consumption).Infrared technology uses light beams to transmit data and uses a line-of-sight connection. Line-of-sight means that the devices communicating with each other must have an unobstructed "view" of each other. They can be used for transmitting data between PDAs or cell phones. This technology previously connected at a speed of about 115 Kbps while advanced technologies for connecting 2 networks together between buildings can run as high as 10 Gbps and extend several miles. Windows XP supports VFIR (Very Fast Infrared) which can transmit at up to 16Mbps and has become common.StandardFrequencyDescriptionMaximum LengthSpeed802.11b - WiFi2.4 GhzWireless networking commonly used in homes and SOHO environments. Being replaced by the faster 802.11g standard. Uses a wireless access point (WAP) to connect to other wireless computers.150+ feet11 mbps802.11g - WiFi2.4 GhzWireless networking commonly used in homes and SOHO environments. Uses a wireless access point (WAP) to connect to other wireless computers. Backward compatible with 802.11b150+ feet54 mbpsInfrared - IrDAUses light, not radio frequenciesUses line of sight connections making it useful for sharing data between personal devices.4Mbps, (VFIR = 16Mbps)Bluetooth2.4 GhzSee aboveUp to 30 feet721 kbpsCabling:The most common form of LAN uses Ethernet which is a collection of standards and specifications that define wiring and signalling for the network. There are a wide variety of standards and cable types. The most common cable types are discussed below:Coaxial - Older Ethernet technologies such as 10Base5 and 10Base2 used coaxial cable (RG-58). These network types are no longer in use. This type of network connection has made a recent comeback and is being used for broadband cable internet connections (RG-59).Unshielded Twisted Pair (UTP) - UTP is a cable type that consists of two or more insulated copper conductors in which each pair of conductors are twisted around each other. Category 1 UTP cables are used for telephony connections. Category 3 and higher are used for Ethernet LAN connections. UTP is inexpensive and easy to work with.Shielded twisted pair (STP) - This type of cable is the same as unshielded twisted pair (UTP), except that it has shielding around it to provide more protection against electromagnetic interference (EMI). Because of its higher cost, it is typically only used in environments where it is necessary.Fiber Optic - Previously only used for WAN connections, fiber optic cabling is now increasingly being used on LANs as well for its capacity for longer distance and higher speeds. A fiber-optic system is similar to the copper wire system (UTP/STP), however, fiber-optics use light pulses to transmit information down fiber lines instead of using electronic pulses to transmit information down copper lines. Fiber cables are made of transparent glass or plastic fibers which allow light to be guided from one end to the other. There are 2 types of fiber cabling - Single-mode fiber (SMF) and multi-mode fiber (MMF). MMF is the most common type used, however, SMF can support longer distances and higher speeds.A plenum area is the air return for an air conditioning system. In most buildings, the plenum area above a drop ceiling is used as the source of air for the air conditioning systems. Wire and cable are usually installed in this area, and if that wire burns during a fire, it will emit toxic fumes. The fumes could carry to the rest of the building through the air conditioner, and, as a result, the fumes could harm others. Plenum grade cabling is required in these types of installations because it is resistant to fire and does not emit poisonous gasses when burned. PVC cable (the standard variety), while cheaper, will emit poisonous gases in extreme heat or fire. Plenum grade cabling is quite a bit more expensive.The various cable types vary in their capacity to transmit data. The definition of the word "bandwidth" can get complicated, but for the purposes of the A+ exam, this term will mean the transmission speed on a network. This next table lists the transmission speeds/bandwidth of the various cable types.Transmission MediumTransmission Speedcat 3 twisted pair10 mbpscat 5 twisted pair100 mbpscat 5e twisted pair1 gbpscat 6 twisted pair10 gbpsFiber Optic100 mbps - 1 gbpsConnectors:Just like there are a variety of cable types, there are a variety of connectors used with these cables. Let's take a look at the most common ones - please note that the images are not to scale.BNC - This connector has found uses with both broadcast television equipment and computer networks. With regards to networking, this connector was used on early 10Base-2 (Thinnet) Ethernet networks. It has a centre pin connected to the center coaxial cable conductor and a metal tube connected to the outer cable shield. A rotating ring outside the tube locks the cable to the female connector.F Connector - This connector is the one used for home broadband cable connections with coaxial cable. This male connector screws onto the female counterpart. The connection typically runs coax from the wall outlet to the cable modem. The cable modem will have a RJ-45 jack for connection a computer or wireless access point.RJ-11 - Short for Registered Jack-11, a four or six-wire connector used primarily to connect telephone equipment in the United States (POTS). The cable itself is called category 1 (Cat 1) and is used for dial-up connections. Modems have rj-11 jacks that connect them to the wall outlet.RJ-45 - Short for Registered Jack-45, it is an eight-wire connector used commonly to connect devices on Ethernet LANs. RJ-45 connectors look similar to RJ-11 connectors used for connecting telephone equipment, but they are larger.ST Connector - The ST connector is a fibre optic connector which uses a plug and socket which is locked in place with a half-twist bayonet lock. The ST connector was the first standard for fiber optic cabling. ST Connectors are half-duplex.SC Connector - The SC connector is a fibre optic connector with a push-pull latching mechanism which provides quick insertion and removal while also ensuring a positive connection. SC Connectors are half-duplex.LC - The LC connector is just like a SC connector only it is half the size. Like SC connectors, LC connectors are half-duplex.MT-RJ - Stands for Mechanical Transfer Registered Jack. It is a newer fiber optic connector that somewhat resembles a RJ-45 connector. It has a small size, low cost, easy installation, and supports full-duplex.Ethernet LAN Types:The following table lists the most common Ethernet types in use today.NameCable TypeConnectorMaximum LengthSpeed10Base-TCategory 3 or better UTP cableRJ-45100 meters(328 ft)10 mbps10Base-FLFiber optic cableST, SC, LC, MT-RJ2000 meters10 mbps100Base-TXCat 5 twisted pairRJ-45100 meters(328 ft)100 mbps100Base-FXFiber OpticST, SC, LC, MT-RJ2000 meters100 mbps1000Base-TCAT5e or higherRJ-45100 meters(328 ft)1 gbpsNote that there are emerging fibre optic technologies such as laser over fibre that have faster speeds and longer distances, but are outside the scope of this course at present.Remote Access:For the purposes of the A+ exam, you will need to be familiar with the following methods of connecting to the internet:Network TypeSpeedConnectionDescriptionDial-up connection (POTS)Up to 56 KbpsTwisted pair with RJ-11 connector.Rapidly being replaced by broadband technologies such as DSL and cable.Integrated Services Digital Network (ISDN)128 kbpsTwister pair with RJ-11 connector.Business accessDigital Subscriber Line (DSL)256 Kbps to 8 MbpsTwisted-pair with RJ-45 connector.Home, small business, and enterprise access using existing phone lines.Cable modem512 Kbps to 52 MbpsCoaxial cable with F connector.Home, business, school accessSatellite400 kbpsSatellite DishRural and remote areasCellular BroadbandUp to 2.4 mbpsCell phoneAccess on the go.Additional Notes:Dial-up networking is fading away with the adoption of faster technologies.ISDN service is an older, but still viable technology offered by phone companies in some parts of the U.S.. ISDN requires an ISDN adapter instead of a modem, and a phone line with a special connection that allows it to send and receive digital signals.ADSL allows you to connect to the internet via your phone line, but allows you to use your phone while connected to the internet. Unlike a cable modem, the speed is stable.Cable modems are much faster generally than ADSL, however, your mileage will vary depending on how many other people are using the bandwidth on your segment.Satellite connections come in two types - 1-way and 2-way. 1-way satellites only accept signals and 2-way connections send and receive. Satellite connections can be affected by weather.ProtocolsThe function of a network is to share resources between computers. In order for this to happen the computers must be able to "talk" to each other which is accomplished with the use of protocols which are essentially a set of "rules" that govern communication over a network. Computers must be configured with a common protocol in order to be able to communicate. Below are some of the most common protocols:TCP/IP - the most commonly used protocol today. It is the one used on the internet and most other networks.IPX/SPX - These protocols were developed by Novell and are/were used with Novell Netware. IPX is the fastest routable protocol and is not connection oriented. IPX addresses are up to 8 characters in hexadecimal format. SPX is connection oriented.NWLink - Microsoft's implementation of the Novell NetWare IPX/SPX protocol for Windows NT Server and Workstation. Not very common anymore.NetBeui - Stands for "NetBIOS Extended User Interface". It was the standard protocol used by older Microsoft operating systems. It is NetBEUI that allowed the "shares' between machines. In reference to the NetBIOS distinction, NetBIOS is the applications programming interface and NetBEUI is the transport protocol. NetBEUI is a non-routable protocol meaning it will not allow communication through a router. This protocol is not used much anymore.TCP/IP Protocol Suite:The TCP/IP protocol suite is made of many other protocols that perform different functions. Below is a list of some of them:TCP - Transport Control Protocol breaks data into manageable packets and tracks information such as source and destination of packets. It is able to reroute packets and is responsible for guaranteed delivery of the data.IP - Internet Protocol is a connectionless protocol, which means that a session is not created before sending data. IP is responsible for addressing and routing of packets between computers. It does not guarantee delivery and does not give acknowledgement of packets that are lost or sent out of order as this is the responsibility of higher layer protocols such as TCP.ICMP - Internet Control Message Protocol enables systems on a TCP/IP network to share status and error information such as with the use of PING and TRACERT utilities.SMTP - Simple Mail Transfer Protocol is used to reliably send and receive mail over the Internet.FTP - File transfer protocol is used for transferring files between remote systems. Must resolve host name to IP address to establish communication. It is connection oriented (i.e. verifies that packets reach destination).ARP - Address Resolution Protocol provides IP-address to MAC address resolution for IP packets. A MAC address is your computer's unique hardware number and appears in the form 00-A0-F1-27-64-E1 (for example). Each computer stores an ARP cache of other computers ARP-IP combinations.POP3 - Post Office Protocol. A POP3 mail server holds mail until the workstation is ready to receive it.IMAP - Internet Mail Access Protocol. Can be used for Internet email in place of POP3.TELNET - Provides a virtual terminal or remote login across the network that is connection-based. The remote server must be running a Telnet service for clients to connect.HTTP - The Hypertext Transfer Protocol is the set of rules for exchanging files (text, graphic images, sound, video, and other multimedia files) on the World Wide Web. It is the protocol controlling the transfer and addressing of HTTP requests and responses. HTTPS is the secure version.TCP/IP Ports:Ports are what an application uses when communicating between a client and server computer. Some common ports are:21 FTP23 TELNET25 SMTP80 HTTP110 POP3143 IMAP443 HTTPS3389 Remote desktop default portTCP/IP Addressing:Every IP address can be broken down into 2 parts, the Network ID (netid) and the Host ID (hostid). All hosts on the same network must have the same netid. Each of these hosts must have a hostid that is unique in relation to the netid. IP addresses are divided into 4 octets with each having a maximum value of 255. We view IP addresses in decimal notation such as, but it is actually utilized as binary data.IP addresses are divided into 3 classes as shown below:ClassRangeA1-126B128-191C192-223NOTE: 127.x.x.x is reserved for loopback testing on the local system and is not used on live systems. The following address ranges are reserved for private networks (ie not used on the Internet): - - - previous information on TCP/IP has referred to IPv4, however, this addressing scheme is running out of available IP addresses due to the large influx of internet users and expanding networks. As a result, a new addressing scheme to deal with this situation is IPv6. This new addressing scheme utilizes a 128 bit address (instead of 32) and utilizes a hex numbering method in order to avoid long addresses such as132. hex address format will appear in the form of 3FFE:B00:800:2::C for example.VOIP (Voice Over Internet Protocol)Also known as Internet Telephony, VOIP is the technology that allows voice traffic to be transmitted and routed over a data network using the Internet Protocol. The advantage of VOIP is that it is low cost (in some cases free) in comparison to using traditional POTS (Plain Old Telephone Systems) for voice communications. Companies such as Vonage and Comcast Cable are currently offering VOIP phone services and Skype is a freeware program that provides free long distance communications with other Skype users.Network Devices:A network is composed of computers, servers, printers, and other devices. The computer, printer, etc. (also known as a client) will have a network interface card (NIC) that one end of the cable plugs into. The NIC can be built into the motherboard or can be an expansion card. In either case, it will need to have the correct driver loaded like any other expansion card.On most Ethernet networks, there are hubs or switches that serve as the central location that all of the clients plug in to. On larger networks, there is usually a wiring closet with at least one switch. Often, the network devices plug into a wall jack that is wired to the switches in the wiring closet.On even larger networks, routers are often needed to divide the network into different segments. Routers are also used as a gateway to the outside world (i.e. connection to ISP).Dial-up Connection:This type of connection is being used less frequently all the time with the emergence of faster and better broadband options. However, you may still need to know how to deal with this type of network connection. Dial-up and ISDN connections use a modem which converts digital signals from your computer to analogue for transmission over phone lines. On the receiving end is another modem which converts the signal back to digital. From a physical standpoint, setting up this type of connection is as simple as connecting a phone cord from your computer to the wall jack.The easiest way to configure this type of connection is to right click on My Network Places and select Properties. Next, click on Create a New Connection which will launch the New Connection Wizard. This wizard can be used to set up a wide variety of connection types including the ones below that are described manually. Once we complete the wizard, a new icon appears in our Network Connections window.The dial-up icon was not there previous to completing the wizard. Now we can go in and configure our dial-up connection. To do this, right click on the dial-up connection icon and select Properties. From here you can configure the modem itself, the connection options, protocols, security, internet connection sharing and other settings.Local Area Network Connection:Once your client is physically plugged into the network, you then need to set things up on the software side. In newer versions of Windows, this has become pretty simple. First, we are going to set up a connection on a LAN. To get started, right click on the "My Network Places" icon on the desktop and select "Properties". This will bring up the network connections dialog box shown below.As you can see in the image, this window lists your current network connections and their status. Here we have a LAN connection that does not have a cable plugged in, a wireless connection that is currently connected, and a 1394 net adapter which is for a firewire network connection.On the left side, you should see "Create a new connection". When you click this, Windows launches the Network Connection Wizard which allows you to configure your cable or DSL connection, dial-up or VPN to a corporate network, and peer-to-peer connections such as serial or infrared.After you have completed the wizard, your new connection should appear in the Network Connections dialogue box. Now the network needs to be configured. To do this, right click on your new connection and click "properties".From here, you can configure your network card (NIC) by clicking on the configure button, although in most cases nothing needs to be done here. This will take you to the same place as viewing the NICs properties in Device Manager.Next we may need to configure our protocol(s). In this case, our network is using TCP/IP, however if you need to use a protocol that isn't there, click on the "Install" button. This will bring up a list of protocols that can be installed. If you still don't see the one you need, then you probably need a disk that contains the installation files for that protocol. This should be very rare. In any event, first highlight the "Internet Control Protocol (TCP/IP)" and click the "properties" button and you will see the screen below.If our network has a DHCP server, then we probably don't need to configure anything at all and should leave the "Obtain an IP address automatically" radio button selected. Checking the other radio buttons will allow you to manually enter IP address, subnet mask, default gateway, and DNS Servers. Once this is done, you should have a connection to your network.Shared Connection With ICS:In the above example, we connected to an existing LAN. What if we want to connect a single computer to a DSL or cable connection? This is as simple as connecting the NIC on the computer to the DSL router or cable modem and following the configuration instructions from the broadband vendor. But, what if we need to connect a few computers to a broadband connection? One option is to get a router and run NAT - the other is to let Windows solve the problem. Windows 2000 and XP include a service called Internet Connection Sharing (ICS). This allows one computer to be connected to the internet, and the others to share the connection. One caveat of this configuration is that the host computer must have 2 network cards installed unless you are using dial-up - one to connect to the cable modem or DSL router and the other to connect to the LAN.To get started, you must have 2 connections in your Network Connections. First, right click on the cable modem or DSL connection and select properties. This will bring up the Local Area Connection Properties window.Next, you need to click on the advanced tab. Here you simply check the box that says, "Allow other network users to connect through this computer's internet connection".Next, we need to configure the clients. This is as easy as going to our TCP/IP properties window shown earlier and making sure that the connection is set to use DHCP. In other words make sure that the "Obtain an IP address automatically" radio button is selected and all other fields are clear.Wireless Connection:Wireless connections are somewhat plug and play and it is fairly easy to set up a basic connection. The first step is to connect the wireless access point (WAP) to a computer using the ethernet cable that came with the WAP. Almost all WAPs have an internal web page that can be viewed by entering the default IP address that it is programmed with. This is usually something like and the default username is usually something like "admin" and "password" respectively. Check the documentation that comes with the WAP for this information. Once logged into the web page, you can configure a wide variety of settings for the access point including IP settings, SSID, wireless channel, WEP and WPA security, and more. The first thing you should do is change the SSID to a unique identifier for your network and change the default username and password. You may need to change the IP settings depending on your situation. Next, it is a good idea to set up security. WPA2 is the best available, although some access points only support WPA. After all of the settings are configured, connect the WAP to the network as appropriate.Now, we need to configure our Wi-Fi client to connect to the access point. Windows includes a wizard that simplifies this process, but we are going to look at the manual method. To get started, first right click on My Network Places and select properties. This will bring up the Network Connections window that we saw in previously discussed connections. There should be a wireless connection icon that will appear after you install the wireless network adapter on the computer. Right click on this icon and select properties. This will bring up the Wireless Network Connection Properties window that is very similar to the Local Area Connection Properties window we saw earlier, and you can configure your TCP/IP properties for your wireless connection in the same manner described earlier.The major difference between this window and the Local Area Connection Properties window is that this one has a Wireless Networks tab that when clicked brings up this window. This allows you to view available wireless networks and connect to them.The next step is to select your preferred wireless network. Your network will show up using the SSID that you configured on the WAP earlier. Once selected, click the properties button where you can configure your security settings depending on what selections you made when configuring the WAP. After all of these steps, you should be able to connect to your wireless network. You can check your connection's "health" by going to My Network Places and double-clicking on the wireless network connection icon.This shows your signal strength, connection speed, and other information that is useful for troubleshooting when there is a problem. If you want to see which networks are available to connect to, simply click on the View Wireless Networks button.Command line network utilitiesIPCONFIG - This utility allows you to quickly check the TCP/IP configuration of a computer from the command line. When used with the /all switch (ipconfig /all), virtually every TCP/IP setting is displayed including the IP address, subnet mask, default gateway, DNS servers, MAC address, and more. When having a network problem, this is one of the most useful tools for checking for configuration problems.PING (Packet InterNet Groper) - PING is a command-line utility used to verify connections between networked devices. PING uses ICMP echo requests that behave similarly to SONAR pings. The standard format for the command is ping ip_address/hostname. If successful, the ping command will return replies from the remote host with the time it took to receive the reply. If unsuccessful, you will likely receive and error message.NSLOOKUP - This is a command that queries a DNS server for machine name and address information. Originally written for Unix operating systems, this command is now available on Windows and other operating systems. To use nslookup, type "nslookup" followed by an IP address, a computer name, or a domain name. NSLOOKUP will return the name, all known IP addresses and all known aliases (which are just alternate names) for the identified machine. NSLOOKUP is a useful tool for troubleshooting DNS problems.TELNET - Telnet is a protocol that allows you to connect to remote computers over the Internet. There is a telnet server on the remote host, which the telnet client negotiates with to establish a connection. Once connected, the client becomes a virtual terminal, and allows you to interface with the host computer via command line from your computer. In most cases, you'll be asked to log into the remote system. This usually requires an account on that host. Telnet uses port 23. Because of security issues with Telnet, Secure Shell (SSH) is becoming the new standard.TRACEROUTE - A command-line troubleshooting tool that enables you to view the route to a specified host. This will show how many hops the packets have to travel and how long it takes. In Windows operating systems, the command used is "TRACERT".The OSI Model:OSI Model (Open Systems Interconnection Model) was developed by the International Standards Organization (ISO). The OSI reference model is a 7 layer networking framework that divides the networking process into logical layers which are often used as a framework for troubleshooting. The 7 layers are: Physical, Data Link (which has sub-layers called Media Access Control and Logical Link Control), Network, Transport, Session, Presentation, and Application. You won't need to know in-depth information about this for the exam, but you should be familiar with it.