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Network+ Study Guide (N10-004)

This is our free study guide for CompTIA's Network+ certification exam (N10-004). If you would like to report an erroror contribute additional information, please use the contact link at the bottom of the site, or post in our forums. We hopeyou find this guide useful in your studies.

Domain 1.0: Network Technologies

Domain 1.1: Common Networking Protocols

TCP - TCP 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 - This is a connectionless protocol, which means that a session is not created before sending data. IP isresponsible for addressing and routing of packets between computers. It does not guarantee delivery and doesnot give acknowledgement of packets that are lost or sent out of order as this is the responsibility of higher layerprotocols such as TCP.UDP - A connectionless, datagram service that provides an unreliable, best-effort delivery.ICMP - Internet Control Message Protocol enables systems on a TCP/IP network to share status and errorinformation such as with the use of PING and TRACERT utilities.SMTP - 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 IPaddress to establish communication. It is connection oriented (i.e. verifies that packets reach destination).TFTP - Same as FTP but not connection oriented.ARP - provides IP-address to MAC address resolution for IP packets. A MAC address is your computer's uniquehardware number and appears in the form 00-A0-F1-27-64-E1 (for example). Each computer stores an ARP cacheof other computers ARP-IP combinations.POP3 - Post Office Protocol. A POP3 mail server holds mail until the workstation is ready to receive it.IMAP - Like POP3, Internet Message Access Protocol is a standard protocol for accessing e-mail from your localserver. IMAP (the latest version is IMAP4) is a client/server protocol in which e-mail is received and held for youby your Internet server.TELNET - Provides a virtual terminal or remote login across the network that is connection-based. The remoteserver 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 andaddressing of HTTP requests and responses.HTTPS - Signifies that a web page is using the Secure Sockets Layer (SSL) protocol and is providing a secureconnection. This is used for secure internet business transactions.NTP - Network Time Protocol is a protocol that is used to synchronize computer clock times in a network ofcomputers.SNMP - Stands for Simple Network Management Protocol and is used for monitoring and status information on anetwork. SNMP can be used to monitor any device that is SNMP capable and this can include computers, printers,routers, servers, gateways and many more using agents on the target systems. The agents report informationback to the management systems by the use of traps which capture snapshot data of the system. This trapinformation could be system errors, resource information, or other information. The SNMPv2 standard includesenhancements to the SNMPv1 SMI-specific data types, such as including bit strings, network addresses, andcounters. In SNMPv3 security was addressed. Because all of the trap information sent was in clear text, anymonitoring information being sent and collected for operational purposes could also be pulled off the wire by amalicious personSIP Stands for Session Initiation Protocol and is a signaling protocol, widely used for controlling multimediacommunication sessions such as voice and video calls over Internet Protocol (IP). Other feasible applicationexamples include video conferencing, streaming multimedia distribution, instant messaging, presence informationand online games. The protocol can be used for creating, modifying and terminating two-party (unicast) ormultiparty (multicast) sessions consisting of one or several media streams. The modification can involve changingaddresses or ports, inviting more participants, adding or deleting media streams, etc.RTP Real-time Transport Protocol is the audio and video protocol standard used to deliver content over theInternet. RTP is used in conjunction with other protocols such as H.323 and RTSP.IGMP Internet Group Management Protocol is used to manage Internet Protocol multicast groups. IP hosts andadjacent multicast routers use IGMP to establish multicast group memberships. IGMP is only needed for IPv4networks, as multicast is handled differently in IPv6 networks.TLS - Transport Layer Security is a cryptographic protocol that provides security for communications overnetworks such as the Internet. TLS and SSL encrypt the segments of network connections at the Transport Layerend-to-end. Several versions of the protocols are in wide-spread use in applications like web browsing, electronicmail, Internet faxing, instant messaging and voice-over-IP (VoIP).

Domain 1.2: Identify Commonly Used TCP/UDP Ports

Ports are what an application uses when communicating between a client and server computer. Some common portsare:

Protocol Type Number

FTP TCP 20,21

SSH TCP 22

TELNET TCP 23

SMTP TCP 25

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DNS TCP/UDP 53

DHCP UDP 67

TFTP UDP 69

HTTP TCP 80

POP3 TCP 110

NTP TCP 123

IMAP4 TCP 143

SNMP UDP 161

HTTPS TCP 443

Domain 1.3: Identify the Following Address Formats

IPv4 - Every IP address can be broken down into 2 parts, the Network ID(netid) and the Host ID(hostid). All hosts onthe same network must have the same netid. Each of these hosts must have a hostid that is unique in relation to thenetid. IP addresses are divided into 4 octets with each having a maximum value of 255. We view IPv4 addresses indecimal notation such as 124.35.62.181, but it is actually utilized as binary data.

IP addresses are divided into 3 classes as shown below:

Class Range

A 1-126

B

many hosts on a private network.

SNAT Secure Network Address Translation an extension of the standard Network Address Translation (NAT) service.SNAT is done through one to one IP address translation of one internal IP address to one external IP address where NATis effectively one external address to many internal IP addresses.

DHCP - Dynamic Host Configuration Protocol provides a solution that automatically assigns IP addresses to computerson a network. When a client is configured to receive an IP address automatically, It will send out a broadcast to theDHCP server requesting an address. The server will then issue a "lease" and assign it to that client. Some of the benefitsof DHCP include the following:

Prevents users from making up their own IP addresses.Prevents incorrect gateway or subnet masks from being entered.Decreases amount of time spent configuring computers especially in environments where computers get movedaround all the time.

APIPA Stands for Automatic Private Internet Protocol Addressing. Client systems that are configured for automatic IPaddress assignment / dynamic IP assignment will attempt to use DHCP to make a request for an IP address lease for agiven network. When the DHCP server is unavailable the service on the client will automatically configure the systemwith an APIPA IP address in the 169.254.0.1 through 169.254.255.254 address range with a subnet mask of 255.255.0.0.

Unicast - the sending of information packets to a single network node. This type of network transmission is used wherea private or unique resource such as media servers are being requested for two way connections that are needed tocomplete the network communication. So in the media server example, a client system may make the request forstreaming content from the single source and the responding system may leverage unicast as part of the response to thesession request to deliver the content.

Multicast a single source address responding to multiple destination addresses with information to be sent. In a mediaserver example, the single source address may need to send the data to multiple clients; it does this by sending the datawith multiple destination IP addresses. All the clients that see this network traffic will check to see if it is meant forthem with the supplied information. If it is not the client does not receive the data. If a network node does see that thedata is intended for them the device will respond by receiving the packet.

Broadcast traffic sent out from a network node that will reach every other node on the subnet / broadcast domainbecause the message is sent with the intent of reaching all nodes. The network node that is sending the traffic will usethe broadcast address for that subnet and every device in that broadcast domain will receive the broadcast information.Generally the broadcast address is the last IP address of that segment. As an example, in the IP address range of192.168.0.0 this broadcast address would be 192.168.255.255 and the traffic would reach all available nodes on thesubnet. Additionally 255.255.255.255 could be used which is the broadcast address of the zero network (0.0.0.0).Internet Protocol standards outline that the zero network stands for the local network so only those node on the localnetwork would hear the broadcast traffic across the 255.255.255.255 address.

Domain 1.5: Common IPv4 and IPv6 Routing Protocols

Link State routing protocols are one of the two main classes of routing protocols used in packet switching networksand includes protocols such as Open Shortest Path First (OSPF) and Intermediate System to Intermediate System(IS-IS). The link-state protocol is performed on every router on the network, where every routing node constructs amap of the connectivity to the network by showing which nodes are connected to each other. Each router calculates thenext best logical hop from it to every possible known destination which forms the node's routing table.

Open Shortest Path First (OSPF) is a dynamic routing protocol and is used on Internet Protocol (IP) basednetworks of all sizes large to small. OSPF is an interior gateway protocol (IGP) that routes IP packets within asingle routing domain and was designed to support variable-length subnet masking (VLSM) and Classless Inter-Domain Routing (CIDR) addressing.Intermediate System to Intermediate System (IS-IS) a link state protocol that operates by forwardingnetwork topology information throughout a network of routers. Each router then independently builds a picture ofthe network's topology based on the data received and the best topological path through the network to thedestination. IS-IS is an Interior Gateway Protocol (IGP) typically used on larger networks.

Distance-vector routing protocols are one of the two main classes of routing protocols used in packet switchingnetworks and includes Routing Information Protocol (RIP) and Interior Gateway Routing Protocol (IGRP). uses distanceas one factor and the vector as the other to determine against the known routing tables to deliver data to source anddestination locations. Routers using the distance-vector routing protocol will update other routers of topology changesperiodically when a change is detected in the topology of a network.

Routing Information Protocol (RIPv1) RIP is a distance-vector routing protocol using hop count as arouting metric. The maximum number of hops allowed for RIP is 15 which effectively limits the size of networksthat RIP can support.Routing Information Protocol (RIPv2) improved upon RIPv1 by having the ability to include subnetinformation with its updates which allows for Classless Inter-Domain Routing (CIDR) support. The 30 secondproactive broadcast has been eliminated in favor of multicast advertisements for its updates. The 15 hop countlimit remains so that the devices are backwards compatible with RIPv1 devices.Border Gateway Protocol (BGP) is the core routing protocol of the Internet. It maintains a table of IPnetworks and the data that designates where and how to reach each network through autonomous systems (AS).BGP makes routing decisions based on path, network policies and / or rule sets.Enhanced Interior Gateway Routing Protocol (EIGRP) a proprietary hybrid protocol from Cisco that is adistance vector routing protocol that functions like a link state routing protocol. EIGRP collects information andstores it in three tables; the Neighbor Table which stores the information about neighboring routers, the TopologyTable which contains only the information and data regarding the routing tables from directly connected neighborsand the Routing table which stores the actual routes to all destinations.

Domain 1.6: The Purpose and Properties of Routing

Interior Gateway Protocol (IGP) routing protocol that is used within an autonomous system which is sometimesreferred to as an administrative domain. One type of Interior Gateway Protocol are the Distance-vector routing protocolssuch as Routing Information Protocol (RIP), Interior Gateway Routing Protocol (IGRP) and Enhanced Interior GatewayRouting Protocol (EIGRP). Another type are the Link-state routing protocols such as Open Shortest Path First (OSPF) andIntermediate system to intermediate system (IS-IS)

Exterior Gateway Protocol (EGP) routing protocol that is used across different autonomous systems /administrative domains. It was the routing protocol leveraged for Internet connected devices in the early 1980s. BorderGateway Protocol (BGP) is the replacement standard for Internet routing over EGP.

Static Router Updates a router with manually configured routing tables. For these types of devices, a network


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administrator will manually build and make updates to the routing table for all routes in the administrative domain.Static routers are best suited for small internetworks; due to the need of the manual administration, they do not scalewell to large networks where routing information is often changed, updated and appended. Static routers are not faulttolerant because when another network device goes down the manually input information may not necessarily providealternate pathing to a destination which makes it unreachable (unless quick, manual administrative updates are made.)

Dynamic Router Updates A router with dynamically configured routing tables. This type of automatic configuration ismade up of routing tables that are built and maintained by ongoing communication between the routers only (by default this does not include initial setup and configuration or administrative needs for a persistent route configuration).Dynamic routing is fault tolerant; if a router or link goes down, the routers sense the change in the network topologywhen the learned route expires in the routing table and cannot be renewed due to the outage. This change is thendisseminated to other routers so that all the routers learn of the network changes. Routing Information Protocol (RIP)and Open Shortest Path First (OSPF) routing protocols for IP and RIP for IPX are some of examples of protocols that canbe used for these dynamic updates.

Next Hop defined as the next place that a data packet needs to go. In most cases, routers do not need all of theinformation regarding where the originating source of the data transmission was. In most cases routers just need toknow where there data needs to go next and the next referred to as the next hop because all they are trying to do isdeliver it to the specified destination IP address that is included in the header information of the data being sent. If thatrouter is the last hop and can deliver it to the specified IP address it does otherwise it refers to its routing tables to figureout which router to hand it off to in the effort to get the data packet where it needs to go.

Routing Tables sometimes referred to as a Routing Information Base (RIB), is the database information that storesall the rout information for the routing network devices. The routing table holds the route information regarding thetopology of the network immediately around the device to other network destinations and it will often include the metric/ cost associated for the route. There are three main route entries that are generally found in the routing tables -Network Route, Host Route and the Default Route. The Network Route is route to a specific Network ID on the network.The Host Route is a route to a specific network address. A Default route is the path used if a physical router or othernetwork routing device cannot find a route for the specified destination.

Convergence achieved when all of the available topology information from routing devices have been passed along toall of the other deceives in totality and all when the information gathered is not in a contradiction state to any otherrouter's informed topology information. When all of the network routing devices "agree" on what the network topologylooks like it is said to have full convergence.

Domain 1.7: Characteristics of Wireless Standards

Wireless networks allow computers to comunicate without the use of cables using IEEE 802.11 standards, also knownas Wi-Fi. A connection is made from a device, which is usually a PC or a Laptop with a wireless network interface card(NIC), and an Access Point (AP), which acts as a bridge between the wireless stations and Distribution System (DS) orwired networks. An 802.11 wireless network adapter can operate in two modes, Ad-Hoc and Infrastructure. Ininfrastructure mode, all your traffic passes through a wireless access point. In Ad-hoc mode your computers talkdirectly to each other and do not need an access point. The table below shows the various standards.

Standard Speed Distance Frequency

802.11a 54 mbps 100 ft 5 GHz

802.11b 11 mbps 300 ft 2.4 GHz

802.11g 54 mbps 300 ft 2.4 GHz

802.11n 540 mbps 600 ft 5 GHz and/or 2.4 GHz

Authentication and Encryption:

WEP - Wired Equivalent Privacy is a security encryption algorithm that is easily cracked. For this reason, it hasbeen replaced by other technologies.WPA - The original WPA standard used TKIP, but was later replaced by WPA2 which uses a more secureAES-based algorithm. WPA uses a 256 bit key to encrypt data. This key may be entered either as a string of 64hexadecimal digits, or as a passphrase of 8 to 63 characters. It is susceptible to brute force attacks when a weakpassphrase is used.RADIUS - Remote Authentication Dial In User Service (RADIUS) is a networking protocol that providescentralized Authentication, Authorization, and Accounting (AAA) management for computers to connect and use anetwork service. RADIUS is often used by ISPs and enterprises to manage access to the Internet or internalnetworks, and wireless networks. Microsoft's answer to corporate wireless security is the use of RADIUSauthentication through its Internet Authentication Services (IAS) product.TKIP - Temporal Key Integrity Protocol was designed as a solution to replace WEP without requiring thereplacement of legacy hardware. TKIP suffered from similar flaws as WEP and has been replaced by more secureencryption schemes.

Domain 2.0: Network Media and Topologies

Domain 2.1: Standard Cable Types and Their Properties

Cable Types:

Type Description

CAT3Unshielded twisted pair capable of speeds up to 10Mbit/s. Used with 10Base-T, 100Base-T4, and100Base-T2 Ethernet.

CAT4Unshielded twisted pair capable of speeds up to 20Mbit/s. Not widely used. Used with 10Base-T,100Base-T4, and 100Base-T2 Ethernet.

CAT5Unshielded twisted pair capable of speeds up to 100Mbit/s. May be used with 10Base-T, 100Base-T4,100Base-T2, and 100Base-TX Ethernet.

CAT5eEnhanced Cat 5 is similar to CAT5, but exceeds its performance. Improved distance over previouscategories from 100m to 350m. May be used for 10Base-T, 100Base-T4, 100Base-T2, 100BaseTX and1000Base-T Ethernet.


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CAT6Can transmit data up to 220m at gigabit speeds. It has improved specifications for NEXT (Near End CrossTalk), PSELFEXT (Power Sum Equal Level Far End Cross Talk), and Attenuation. Cat 6 is backwardcompatible with lower Category grades and supports the same Ethernet standards as Cat 5e.

MultimodeFiber

Multimode fibers have large cores. They are able to carry more data than single mode fibers though theyare best for shorter distances because of their higher attenuation levels.

Single ModeFiber

Single Mode fibers have a small glass core. Single Mode fibers are used for high speed data transmissionover long distances. They are less susceptible to attenuation than multimode fibers.

RG59 andRG6

These are both shielded coaxial cables used for broadband networking, cable television, and other uses.

Serial

A serial cable is a cable that can be used to transfer information between two devices using serialcommunication, often using the RS-232 standard. Typically use D-subminiature connectors with 9 or 25pins. Cables are often unshielded, although shielding cables may reduce electrical noise radiated by thecable.

Shielded twisted pair (STP) - differs from UTP in that it has a foil jacket that helps prevent cross talk. Cross talk issignal overflow from an adjacent wire.

EMI - Electrical devices such as printers, air conditioning units, and television monitors can be sources ofelectromagnetic interference, or EMI. Some types of network media have more resistance to EMI than others. StandardUTP cable has minimal resistance to EMI, while fiber optic cable is highly resistant.

Plenum grade cabling - is required if the cabling will be run between the ceiling and the next floor (this is called theplenum). Plenum grade cabling is resistant to fire and does not emit poisonous gasses when burned.

Simplex - Signals can be passed in one direction only.Half Duplex - Half duplex means that signals can be passed in either direction, but not in both simultaneously.Full Duplex - Full duplex means that signals can be passed in either direction simultaneously.

Domain 2.2: Common Connector Types

BNC - This connector has found uses with both broadcast television equipment and computernetworks. With regards to networking, this connector was used on early 10Base-2 (Thinnet)Ethernet networks. It has a center pin connected to the center coaxial cable conductor and ametal tube connected to the outer cable shield. A rotating ring outside the tube locks the cableto the female connector.

RJ-11 - Short for Registered Jack-11, a four or six-wire connector used primarily to connecttelephone 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 walloutlet.

RJ-45 - Short for Registered Jack-45, it is an eight-wireconnector used commonly to connect devices on Ethernet LANs.RJ-45 connectors look similar to RJ-11 connectors used forconnecting telephone equipment, but they are larger.

ST - The ST connector is a fiber optic connector which uses a plug and socket which is lockedin place with a half-twist bayonet lock. The ST connector was the first standard for fiber opticcabling. ST Connectors are half-duplex.

SC - The SC connector is a fiber optic connector with a push-pulllatching mechanism which provides quick insertion and removalwhile also ensuring a positive connection. SC Connectors arehalf-duplex.

LC - The LC connector is just like a SC connector only it is half the size. Like SC connectors, LCconnectors are half-duplex.

RS-232 - A standard for serial binary data interconnection betweena DTE (Data terminal equipment) and a DCE (Data communicationequipment). Commonly found in use with bar code scanners,measuring tools, and laboratory instruments are designed tointerface to a computer using a standard RS232 serial cableconnection. Many of these uses are being replaced with USB enabled devices. The connector is a DB-9 or DB-25connector.

Domain 2.3: Common Physical Network Topologies

Star - The star topology uses twisted pair (10baseT or 100baseT) cabling and requires that all devicesare connected to a hub. Advantages are centralized monitoring, and failures do not affect others unlessit is the hub, easy to modify. The disadvantage is that the hub is a single point of failure. If it goesdown, there are no communications possible.

Mesh - In a true mesh topology every node has a connection to every other node in the network. A fullmesh provides redundancy in case of a failure between links, but is impractical due the complexity andthe expensive amount of cabling required.

Bus - This topology is an old one and essentially has each of the computers on the network daisy-chained to each other. Packets must pass through all computers on the bus. This type is cheap, andsimple to set up, but causes excess network traffic, a failure may affect many users, and problems aredifficult to troubleshoot.


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Ring - A ring topology has a physical and logical ring and is used on SONET and FDDI networks (notethat Token Ring networks are actually a hybrid star ring topology). Any station can send a packetaround the ring but only the station with the token can do so. The token is passed around the ringgiving all stations an opportunity to communicate. This is a very fast and simple network. However ifany part of the ring goes down, the entire LAN goes down. If there is a problem at a station, it may bedifficult to locate it. Ring networks are not very common.

Point-to-point - This topology generally refers to a connection restricted to two endpoints. Point-to-point is sometimes referred to as P2P (not the same as peer-to-peer file sharing networks), or Pt2Pt,or variations of this. Examples of this topology include RS-232 serial connections as well as lasernetwork connections between buildings.

Point-to-Multipoint - Also known as P2MP, this is a method of communication between a series ofreceivers and transmitters to a central location. The most common example of this is the use of awireless access point that provides a connection to multiple devices.

Hybrid - Hybrid topologies are combinations of the above and are common on very large networks.For example, a star bus network has hubs connected in a row (like a bus network) and has computers

connected to each hub as in the star topology.

Domain 2.4: Wiring Standards

568A and 568B - The number 568 refers to the order in which the individual wires inside a CAT 5 cable are terminated.The only difference between the two standards is that the green and orange pins are terminated to different pins. Thereis no difference in signal and both the 568A and 568B are used as patch cords for Ethernet connections.

Straight through vs Crossover - A straight through cable uses either the 568A or 568B wiring standard and is used forconnecting devices to routers, hubs, switches, etc. An crossover cable is used to connect computing devices togetherdirectly (i.e. connecting 2 computers directly together). A crossover cable uses the 568A standard on one end and 568Bon the other end.

Rollover - Rollover cable (also known as Cisco console cable) is a type of null-modem cable that is most commonly usedto connect a computer terminal to a router's console port. This cable is typically flat and has a light blue color. It gets thename rollover because the pinouts on one end are reversed from the other, as if the wire had been rolled over and youwere viewing it from the other side.

Loopback - A loopback cable redirects the output back into itself and is used for troubleshooting purposes (loopbacktest). This effectively gives the NIC the impression that it is communicating on a network, since its able to transmit andreceive communications.

Domain 2.5: WAN Technology Types and Properties

Frame Relay - Frame relay is a secure, private network that utilizes a logical path or virtual circuit to allocatebandwidth for high performance transmissions. Frame relay is the premier high-speed packet-switching protocolcommunicating data, imaging, and voice between multiple locations. Frame relay is available in a range of bandwidthsfrom 56 Kbps to full T1 (1.54 Mbps).

T-1/T-3 - A T-1 is a dedicated phone connection supporting data rates of 1.544Mbps. A T-1 line actually consists of 24individual channels, each of which supports 64Kbits per second. Each 64Kbit/second channel can be configured to carryvoice or data traffic. Most telephone companies allow you to buy just some of these individual channels, known asfractional T-1 access. T-1 lines are a popular leased line option for businesses connecting to the Internet and for InternetService Providers (ISPs) connecting to the Internet backbone. The Internet backbone itself consists of faster T-3connections. T-1 comes in either copper or fiber optics.

ATM - ATM stands for Asynchronous Transfer Mode and is a high-speed, packet-switching technique that uses shortfixed length packets called cells. ATM can transmit voice, video, and data over a variable-speed LAN and WANconnections at speeds ranging from 1.544Mbps to as high as 622Mbps. ATM is capable of supporting a wide range oftraffic types such as voice, video, image and data.

SONET - SONET and SDH are a set of related standards for synchronous data transmission over fiber optic networks.SONET is short for Synchronous Optical NETwork and SDH is an acronym for Synchronous Digital Hierarchy. SONET is theUnited States version of the standard and SDH is the international version. SONET defines a base rate of 51.84 Mbps anda set of multiples of the base rate known as "Optical Carrier levels." (OCx). Speeds approaching 40 gigabits per secondare possible.

ISDN - Integrated Services Digital Network (ISDN) is comprised of digital telephony and data-transport servicesoffered by regional telephone carriers. ISDN involves the digitalization of the telephone network, which permits voice,data, text, graphics, music, video, and other source materials to be transmitted over existing telephone wires. There are2 types of ISDN channels:

B (bearer) - Transfers data at 64Kbps. An ISDN usually contains 2 B channels for a total of 128kbps.D (data) - Handles signalling at either 16Kbps or 64Kbps(sometimes limited to 56Kbps) which enables the Bchannel to strictly pass data

Connection Speed Medium

ISDN BRI 64kbps/channel Twisted-pair

ISDN PRI 1,544kbps Twisted-pair

POTS Up to 56 Kbps Twisted pair

PSTN 64kbps/channel Twisted-pair

Frame Relay 56kbps-45mbps Varies

T-1 1.544 Mbps Twisted-pair, coaxial, or optical fiber

ADSL 256Kbps to 24Mbps (ADSL 2+) Twisted-pair

SDSL 1.544mbps Twisted-pair

VDSL 100mbps Twisted-pair

Cable modem 512 Kbps to 52 Mbps Coaxial

Satellite 1gbps (avg 1-5mbps) Air

T-3 44.736 Mbps Twisted-pair, coaxial, or optical fiber

OC-1 51.84 Mbps Optical fiber


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OC-3 155.52 Mbps Optical fiber

Wireless 1gbps Air

ATM 10gbps Optical fiber

SONET 10gbps Optical fiber

Packet and Circuit Switching - Packet switching refers to protocols in which messages are divided into packets beforethey are sent. Each packet is then transmitted individually and can even follow different routes to its destination. Onceall the packets forming a message arrive at the destination, they are recompiled into the original message. Most modernWide Area Network (WAN) protocols, including TCP/IP and Frame Relay are based on packet-switching technologies. Incontrast, normal telephone service is based on a circuit-switching technology, in which a dedicated line is allocated fortransmission between two parties. Circuit-switching is ideal when data must be transmitted quickly and must arrive inthe same order in which it is sent. This is the case with most real-time data, such as live audio and video. Packetswitching is more efficient and robust for data that can withstand some delays in transmission, such as e-mail messagesand Web pages.

Domain 2.6: LAN Technology Types and Properties

Ethernet - Ethernet is the most widely-installed local area network ( LAN) technology. Specified in a standard, IEEE802.3, Ethernet was originally developed by Xerox from an earlier specification called Alohanet (for the Palo AltoResearch Center Aloha network) and then developed further by Xerox, DEC, and Intel. Early ethernet networks usescoaxial connections. The most common types currently use twisted pair cabling, however, fiber optic cabling is becomingmuch more common as standards and speeds increase. Below are some of the ethernet standards:

ConnectionType

Cable Type ConnectorMaximumLength

Speed

10Base-TCategory 3 or better UTPcable

RJ-45100 meters(328 ft)

10mbps

100Base-TX Cat 5 twisted pair RJ-45100 meters(328 ft)

100mbps

100Base-FX Fiber Optic ST, SC 2000 meters100mbps

1000Base-T CAT5e or higher RJ-45100 meters(328 ft)

1 gbps

1000Base-LX Laser over fiber SCUp to 5000meters

1 gbps

1000Base-SXShort wavelength laserover fiber

SCUp to 550meters

1 gbps

1000Base-CXTwinax or short haulcopper

9-Pin shielded D-subminiature connector, or8-pin ANSI fiber channel type 2 (HSSC)connector.

25 meters 1 gbps

10GBASE-SRShortwave laser overmulti-mode fiber optics

LC, SC 300 meters 10 Gbps

10GBASE-LRLaser over single-modefiber optics


10GBASE-ERLaser over either singleor multi-mode fiber

LC, SC 40 kilometers 10 Gbps

10GBASE-SWShortwave laser overmulti-mode fiber optics


10GBASE-LWLaser over single-modefiber optics


10GBASE-EWLaser over either singleor multi-mode fiber

LC, SC 40 kilometers 10 Gbps

10GBASE-TCat 5e (or higher) twistedpair

RJ-45100 meters(328 ft)

10 Gbps

CSMA/CD (Carrier Sense Multiple Access with Collision Detection) - In the early days of ethernet, when twohosts would send packets at the same time, a collision would occur. A standard had to be created that would have thehosts follow rules relating to when they could send data and when they could not. This standard is Carrier Sense MultipleAccess with Collision Detection, referred to as CSMA/CD. CSMA/CD forces computers to listen to the wire beforesending in order to make sure that no other host on the wire is sending. If a collision is detected, both of the senders willsend a jam signal over the Ethernet. This jam signal indicates to all other devices on the Ethernet segment that therehas been a collision, and they should not send data onto the wire.How Ethernet CSMA/CD Works

Bonding (AKA Link Aggregation, Port Trunking, EtherChannel, etc.) - Uses multiple network cables/ports inparallel to increase the link speed beyond the limits of any one single cable or port, and to increase the redundancy forhigher availability.

Domain 2.7: Common Logical Network Topologies

Peer to Peer - A peer to peer network is one in which lacks a dedicated server and every computer acts as both a clientand a server. This is a good networking solution when there are 10 or less users that are in close proximity to eachother. A peer to peer network can be a security nightmare, because the people setting permissions for shared resourceswill be users rather than administrators and the right people may not have access to the right resources. Moreimportantly the wrong people may have access to the wrong resources, thus, this is only recommended in situationswhere security is not an issue. P2P file sharing networks work under a similar architecture, however, there aredifferences between them and the LAN networking architecture.

Client/Server - This type of network is designed to support a large number of users and uses dedicated server/s toaccomplish this. Clients log in to the server/s in order to run applications or obtain files. Security and permissions can bemanaged by 1 or more administrators which who set permissions to the servers' resources. This type of network also


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allows for convenient backup services, reduces network traffic and provides a host of other services that come with thenetwork operating system.

VPN - A virtual private network is one that uses a public network (usually the Internet) to connect remote sites or userstogether. Companies use site to site VPN to support critical applications to connect offices to remote users. Instead ofusing a dedicated, real-world connection such as leased line, a VPN uses "virtual" connections routed through theInternet from the company's private network to the remote site or employee.

VLAN - A virtual LAN is a local area network with a definition that maps workstations on a basis other than geographiclocation (for example, by department, type of user, or primary application). The virtual LAN controller can change or addworkstations and manage load-balancing and bandwidth allocation more easily than with a physical picture of the LAN.Network management software keeps track of relating the virtual picture of the local area network with the actualphysical picture.

Domain 2.8: Install components of Wiring Distribution

Vertical Cross Connect is a location within a building where cables originate and / or are terminated, reconnectedusing jumpers or pass throughs or are connected to patch panels or other similar devices where the locations are fromupper or lower floors in the building. These cables could be of multiple different types and mediums such as phonenetworks, data lines, copper based, fiber channel, etc.

Horizontal Cross Connect similar to Vertical Cross Connect locations; these are within a building where cablesoriginate and / or are terminated but these locations are all on the same floor or building level. As with Vertical CrossConnect configurations, these locations can be of multiple different network types and mediums.

Patch Panel wall or rack mounted collection of data connections where all of the network media converges. Theserooms are generally some form of telecommunications closet in a facility and it is used to connect all of the differenttypes of incoming and outgoing media types on the LAN. When they all span the same floor of a building they aresometimes referred to as Horizontal Cross Connect locations and when they span different levels of a location / differentfloors of a building they are sometimes referred to as Vertical Cross Connect locations. The main Patch Panel room willoften be the connection point for the LAN to be connected to the WAN and / or the internet.

66 Block is a legacy type of punch down block used to connect sets of 22 through 26 American Wire Gauge (AWG)solid copper wire in a telephone system. They have a 25-pair standard non-split capacity and generally are unsuited fortraffic and data network communications above 10 megabits per second (Mbps).

Main Distribution Frame (MDF) is a wire distribution frame for connecting equipment inside a facility to cables andsubscriber carrier equipment outside of the facility. One example of this is where all of the phone cabling inside a facilityis run to planned phone locations (e.g. offices) back to the MDF. When the local telephone company makes the externalconnections then all circuits are completed.

Intermediate Distribution Frame (IDF) is another place much like a Horizontal Cross Connect location or a VerticalCross Connect location where network administrators can physically change the network media around and where theycan house other needed network equipment such as routers, switches, repeaters and so forth.

25 Pair is a grouping of 25 pairs of wires all inside a single covering / housing or outer insulation casing. It is bestsuited for telephone / voice cable runs rather than data cable runs and is generally used as a feeder cable.

100 Pair is a larger cabling segment to its 25 pair cousin but used in the same manner; all of the 100 pairs of wiresare inside a single covering / housing or outer insulation casing. It is best suited for telephone / voice cable runs ratherthan data cable runs and is generally used as a feeder cable.

110 Block is the more modern replacement of the legacy 66 Block and is used as a wiring distribution point for wiredtelephone systems (voice) and other types of wired networking (data). On one side of the block wires are punched downinto RJ-11 connectors for voice and RJ-45 connectors for data communications.

Demarc is the point of operational and administrative control change in a network. One example of this is the MainDistribution Frame (MDF) point in a facility. This is where the wire distribution frame for connecting equipment inside afacility to cables and subscriber carrier equipment outside of the facility occurs and this is considered a demarcation pointof the operational control of the internal systems where it changes over to the control of the external presence.

Demarc Extension where the end of the line of the external administrative control is extended beyond that actualendpoint. Example you are one business inside of a large high rise building on the 15th floor only and the MainDistribution Frame (MDF) point is on the ground floor. Your responsibility probably ends at the Intermediate DistributionFrame (IDF) on your floor and the external administration (example Phone Company) ends at the Main DistributionFrame (MDF) on the ground floor. The building administration owns all the cabling responsibility between the MainDistribution Frame (MDF) on the ground floor and your Intermediate Distribution Frame (IDF) on your floor. That cablingis effectively the Demarc Extension

Smart Jack is a network connection device that is used to connect your internal network to an external serviceprovider network. The device handles all of the code and protocol differences between the two networks and is often theactual demarcation point between the two service entities.

Wiring Installation is the physical installation of internal wiring in a facility. This may be the pulls of copper phoneand data lines to the running of fiber optic medium from the different cross connect locations.

Wiring Termination is the end point of networked cable runs that will generally end either in a patch panel or a jacklocation in an office. This has historically been the copper wire runs associated with phone lines to the RJ-11 jacks /blocks to the data lines on the RJ-45 connections. Wire termination is also a consideration on fiber optic pulls as wellwhich requires a higher set of skill level.

Domain 3.0: Network Devices

Domain 3.1: Common Network Devices

Hub - A physical layer network device used to connect multiple Ethernet devices together. Activehubs act as a repeater and boost the signal in order to allow for it to travel farther, while passivehubs simply pass the signal through. Most hubs have an uplink port that allows them to connect toother hubs, a router, or other network devices.

Repeater: - A physical layer device that boosts signals in order to


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allow a signal to travel farther and prevent attenuation.Attentuation is the degradation of a signal as it travels farther from its origination.Repeaters do not filter packets and will forward broadcasts. Both segments must usethe same access method, which means that you can't connect a token ring segment to

an Ethernet segment. Repeaters can connect different cable types as shown in the image.

Modem - The modem is a device that converts digital information to analog by MODulating it on thesending end and DEModulating the analog information into digital information at the receiving end.Most modern modems are internal, however, they can be internal or external. External modems areconnected to the back of the system board via a RS-232 serial connection. Internal modems areinstalled in one of the motherboard's PCI or ISA expansion slots depending on the modem. Themodem contains an RJ-11 connection that is used to plug in the telephone line. Modems have different transmissionmodes as follows:

Simplex - Signals can be passed in one direction only.Half Duplex - Half duplex means that signals can be passed in either direction, but not in both simultaneously.Half-duplex modems can work in full-duplex mode.Full Duplex - Full duplex means that signals can be passed in either direction simultaneously.

Modems can also be classified by their speed which is measured by the BAUD rate. One baud is one electronic statechange per second. Since a single state change can involve more than a single bit of data, the Bits Per Second(BPS) unitof measurement has replaced it as a better expression of data transmission speed. Common modem speeds are V.34 at28.8 kbps, V.34+ at 33.6 kbps and V.90 at 56 Kbps.

Network Interface Card - A Network Interface Card, often abbreviated as NIC, is anexpansion board you insert into a computer so the computer can be connected to a network.Most NICs are designed for a particular type of network, protocol and media, although somecan serve multiple networks.

Media Converters - simple networking devices that make it possibleto connect two dissimilar media types such as twisted pair with fiber

optic cabling. They were introduced to the industry nearly two decades ago, and are importantin interconnecting fiber optic cabling-based systems with existing copper-based, structuredcabling systems. They are also used in MAN access and data transport services to enterprisecustomers. Fiber media converters support many different data communication protocolsincluding Ethernet, Fast Ethernet, Gigabit Ethernet, T1/E1/J1, DS3/E3, as well as multiplecabling types such as coax, twisted pair, multi-mode and single-mode fiber optics. Mediaconverter types range from small standalone devices and PC card converters to high port-density chassis systems thatoffer many advanced features for network management.

Switch - A switch is a network device that filters and forwards packets between LANsegments and ensures that data goes straight from its origin to its proper destination.Switches remember the address of every node on the network, and anticipate wheredata needs to go. A switch only operates with the computers on the same LAN. Thisreduces competition for bandwidth between devices on the network. It isn't smart

enough to send data out to the internet, or across a WAN. These functions require a router.

Bridge - Functions the same as a repeater, but can also divide a network in order to reducetraffic problems. A bridge can also connect unlike network segments (ie. token ring andethernet). Bridges create routing tables based on the source address. If the bridge can't findthe source address it will forward the packets to all segments. Bridging methods:

Transparent - Only one bridge is used.Source-Route - Bridging address tables are stored on each PC on the networkSpanning Tree - Prevents looping where there exists more than one path between segments

Wireless Access Point - A Wireless Access Point is a radio frequency transceiver which allows yourwireless devices to connect to a network. The WAP usually connects to a wired network, and can relaydata between the wireless devices (such as computers or printers) and wired devices on the network. Awireless access point will support up to 32 wireless devices. The range of the wireless signal dependsgreatly on obstructions such as walls. For more information about wireless standards, see domain 1.7.

Router - Functioning at the network later of the OSI model, a router is similarto a switch, but it can also connect different logical networks or subnets andenable traffic that is destined for the networks on the other side of the routerto pass through. Routers create or maintain a table of the available routes andcan be configured to use various routing protocols to determine the best route for a given data packet. Routers canconnect networks that use disimilar protocols. Routers also typically provide improved security functions over a switch.

Firewall - Either a hardware or software entity (or a combination of both) thatprotects a network by stopping network traffic from passing through it. In most cases,a firewall is placed on the network to allow all internal traffic to leave the network(email to the outside world, web access, etc.), but stop unwanted traffic from theoutside world from entering the internal network. This is achieved by granting anddenying access to resources based on a set of configurable rules.

DHCP Server - A server that is responsible for assiging unique IP address to thecomputers on a network. A DHCP server prevents the assignment of duplicate IP

addresses to clients and reduces administrative effort in network configuration. A DHCP server is actually more of aservice that is found on network operating systems such as Windows 2002/2008 server, or on network devices such asrouters.

Domain 3.2: Specialized Network Devices

Multilayer Switch - A multilayer switch (MLS) is a computer networking device that switches on OSI layer 2 like anordinary network switch and provides extra functions on higher OSI layers. Some MLSs are also able to route betweenVLAN and/or ports like a common router. The routing is normally as quick as switching (at wirespeed). Some switchescan use up to OSI layer 7 packet information; they are called layer 4-7 switches, content-switches, web-switches orapplication-switches.

Content Switch - The main function of a content switch is to inspect the network data that it receives so that it candecide where on the network that data (or request) needs to be forwarded to. Once this is determined the data is sent tothe appropriate server which can handle the data. In most cases the switch looks to see what type of application orsoftware the request is targeted at. It does this by looking to see what port the requests is directed at. For example if


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the data is targeted at an ftp port then the request will be sent to an ftp sever. The main benefit of this approach is thatthe switch acts as a load balancer as it can balance data or requests across the different type of application servers usedby the business. A second major function that this type of switch can perform is to look at the incoming requests and seewhich websites are targeted. This is important for large enterprises or hosting companies. If for example a web hostingcompany was hosting several thousand websites the switch could direct requests to the specific servers that the websitesare running on. These devices tend to be very expensive.

IDS/IPS - These terms stand for Intrusion Detection System and Intrusion Prevention System respectively. IDS is adevice (or application) that monitors network and/or system activities for malicious activities or policy violations. IDS isa passive system that gives alerts when something suspicious is detected and logs the events into a database forreporting. IPS, on the other hand, sits inline with traffic flows on a network, actively shutting down attempted attacks astheyre sent over the wire. It can stop the attack by terminating the network connection or user session originating theattack, by blocking access to the target from the user account, IP address, or other attribute associated with thatattacker, or by blocking all access to the targeted host, service, or application. Vendors are increasingly combining thetwo technologies into a single box, now referred to as IDPS. These devices are used with, not instead of, a firewall.

Load Balancer - A load balancer is a hardware and/or software solution that provides load balancing services. Loadbalancing is used to distribute workloads evenly across two or more computers, network links, CPUs, hard drives, orother resources, in order to get optimal resource utilization, maximize throughput, minimize response time, and avoidoverload. Using multiple components with load balancing, instead of a single component, may increase reliabilitythrough redundancy. As an example, Google receives many, many more search requests than a single server couldhandle, so they distribute the requests across a massive array of servers.

Mutlifunction Network Devices - As you might guess, multifunction network devices combine the function ofindividual devices into a single unit. An example is wireless access points which often include one or more of thefollowing: firewall, DHCP server, wireless access point , switch, gateway, and router.

DNS Server - DNS is an Internet and networking service that translates domain names into IP addresses. The internetis based on numerical IP addresses, but we use domain names because they are easier to remember. DNS is the servicethat looks up the IP address for a domain name allowing a connection to be made. This process is very similar to callinginformation. You call them with a name, they check their database and give you the phone number. The DNS service isincluded with server operating systems (Windows 2003/2008, Linux, etc.) and network devices such as routers.

Bandwidth Shaper - Describes the mechanisms used to control bandwidth usage on the network. Bandwidth shaping istypically done using software installed on a network server. From this server, administrators can control who usesbandwidth, for what, and when. Bandwidth shaping establishes priorities to data traveling to and from the Internet andwithin the network. A bandwidth shaper essentially performs two key functions: monitoring and shaping. Monitoringincludes identifying where bandwidth usage is high and at what time of day. After that information is obtained,administrators can customize or shape bandwidth usage for the best needs of the network. I am unaware why CompTIAlisted this in the "network devices" section of their objectives, but bandwidth shapers are typically software.

Proxy Server - A proxy server acts as a middle-man between clients and the Internet providing security, administrativecontrol, and caching services. When a user makes a request for an internet service and it passes filtering requirements,the proxy server looks in its local cache of previously downloaded web pages. If the item is found in cache, the proxyserver forwards it to the client. This reduces bandwidth through the gateway. If the page is not in the cache, the proxyserver will request the page from the appropriate server. Nowadays, the functions of proxy servers are often built intofirewalls.

CSU/DSU - A Channel Service Unit/Data Service Unit (CSU/DSU) acts as a translator between the LAN data format andthe WAN data format. Such a conversion is necessary because the technologies used on WAN links are different fromthose used on LANs. Although CSU/DSU's look similar to modems, they are not modems, and they don't modulate ordemodulate between analog and digital. All they really do is interface between a 56K, T1, or T3 line and serial interface(typically a V.35 connector) that connects to the router. Many newer routers have CSU/DSUs built into them.

Domain 3.3: Advanced Features of a Switch

PoE - Generally speaking, Power over Ethernet technology describes a system to safely pass electrical power, along withdata, on Ethernet cabling. Standard versions of PoE specify category 5 cable or higher. Power can come from a powersupply within a PoE-enabled networking device such as an Ethernet switch or from a device built for "injecting" poweronto the Ethernet cabling. IP Phones, LAN access points , and WiFi switches to RFID readers and network securitycameras. All of these require more power than USB offers and very often must be powered over longer runs of cablethan USB permits. In addition, PoE uses only one type of connector, an 8P8C (RJ45), whereas there are four differenttypes of USB connectors.

Spanning Tree Protocol - Spanning Tree is one of three bridging methods a network administrator can use. Whichmethod you use usually will be determined by the networks size. The simplest method is transparent bridging, whereonly one bridge or switch exists on the network. The next is Source-Route, in which bridging address tables are storedon each PC on the network. Then theres what you came for, spanning tree, which prevents loops where there existsmore than one path between segments. STP was upgraded to Rapid Spanning Tree Protocol (RSTP).

VLAN - A broadcast domain is normally created by the router. With VLANs, a switch can create the broadcast domain.This allows a virtual network, independent of physical location to be created.


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Trunking - VLANs are local to each switch's database, and VLAN information is not passed between switches. Trunk linksprovide VLAN identification for frames traveling between switches. The VLAN trunking protocol (VTP) is the protocol thatswitches use to communicate among themselves about VLAN configuration.

Port Mirroring - Used on a network switch to send a copy of network packets seen on one switch port (or an entireVLAN) to a network monitoring connection on another switch port. This is commonly used for network appliances thatrequire monitoring of network traffic, such as an intrusion-detection system.

Port Authentication - The IEEE 802.1x standard defines 802.1x port-based authentication as a client-server basedaccess control and authentication protocol that restricts unauthorized clients from connecting to a LAN through publiclyaccessible ports. The authentication server validates each client connected to a switch port before making available anyservices offered by the switch or the LAN.

Domain 3.4: Implement a Basic Wireless Network

Install Client the actual steps taken to set up a computer, laptop or other network connected device to the network.This may be in the form of just getting it correctly configured to use TCP/IP or more involved such as installing asoftware suite so that specific network parameters can be leveraged for proper connectivity to network resources orresources on the domain.

Network Connections Dialog Box used to configure different aspects of the network connections by way of agraphical user interface (GUI) within the Microsoft Windows operating systems (Windows XP, Windows Vista, Server2003, etc). With respect to peer to peer networks, you can use the Network Tasks pane to Create a New Connection, Setup a Home or small office network as well as change the Windows Firewall settings and view available wirelessnetworks.

Wireless Network Connection Dialog Box the graphical user interface (GUI) within the Microsoft Windowsoperating systems used to configure the wireless devices and their settings. On the General tab you can configure thespecific hardware settings (parameters, drivers, etc) as well as the protocols (e.g. TCP/IP) and the network client thatthe device will use (e.g. Client for Microsoft Networks). Additionally, you can install services from this screen as well(e.g. Virtual Machine Network Service). The Wireless Networks tab will show you the available networks and allow youto configure preference for each of the networks encountered.

Access Point Placement correctly positioning your Wireless Access Points will allow for the seamless use ofwireless devices on your network. By correctly placing the devices, users will not generally experience signal loss of theirconnection to the network. It is important to understand that there are many things that affect the wireless access pointsignal with respect to broadcast and receiving strength that include the construction and architecture of the buildingwhere the devices are distributed as well as general disruption of the frequency range that the access points operate onby other devices (e.g. microwave ovens, cordless phones, etc).

Physical Locations of Wireless Access Points (WAPs) device placement best practices include planning for morethan just nominal half distances between devices. Consideration needs to be given to what type of obstructions may becurrently in the way (physical fire breaks in between walls; metal superstructure, etc) as well as future plans tosubdivide offices. Electrical motors and other higher current carrying lines need to be considered as well to keepinterference to a minimum.

Wired or Wireless Connectivity planning for WAP to WAP connections only or a mix of wired and wirelessconnections. Its easier to connect WAP to WAP in a daisy chain signal relay configuration but when you do this you needto realize that a physical failure in one WAP device may take out all the devices. It is more work and it costs more intime money and effort to connect the WAPs using wired connections back to a switch or a router but it greatly reducesthe potential connectively loss on the network; the loss of a single WAP where the WAPs are wired back results in onlyimpacting the users of that one WAP instead of all WAPs up and downstream.

Install Access Point another term for the Wireless Access Point(s) that will allow you to correctly gain access to thenetwork with your device. This point onto the network will allow the client device to configure itself with the necessaryencryption (if required) and any other network required settings or else risk being defaulted off the network.

Configuring Encryption with respect to wireless clients these are the settings most commonly used. Disabled simplymeans that everything is passed as clear text. Wired Equivalent Privacy (WEP) is the lowest form of the types ofencryption available and is generally only used today to allow legacy devices that cannot handle more robust encryptionprotocols to gain somewhat secured access to the network. WEP has been challenged and defeated for a number of


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years mainly due to the increase in computing power and the fact that the keys are alphanumeric or hexadecimalcharacters that are configured in 40 bit, 64 bit, 128 bit, 153 bit and 256 bit strength. Wi Fi Protected Access (WPA) wascreated by the Wi-Fi Alliance to better secure wireless networks and was created in response to the weaknessesresearchers found in Wired Equivalent Privacy (WEP). Temporal Key Integrity Protocol (TKIP) is used in WPA to encryptthe authentication and encryption information that was initially passed on the wire in clear text before a network nodecould secure its communications on the network. Wi Fi Protected Access version 2 (WPA2) offers additional protectionbecause it uses the strongest authentication and encryption algorithms available in the Advanced Encryption Standard(AES).

Configuring Channels and Frequencies most wireless routers work in the 2.4GHz frequency range and requirenetwork administrators to set up the channels for the devices to use. 1, 6 and 11 are the main channels used becausethey generally will not be interfered with from other devices such as cordless phones and Bluetooth devices that alsowork at this frequency range.

Setting ESSID and Beacon Extended Service Set identifier (ESSID) is the advertisement from the Wireless AccessPoint that basically announces its availability for network devices to make a connection. The announcement signal that issent out is called the beacon.

Verifying Installation - the process that is outlined for making sure that all the settings needed to connect a networknode to the wireless device. The best practice steps generally include on initial installation of the Wireless Access Point(WAP) to do so without any security to verify that a client can get on the network. Once that is successful you would thenincorporate the security protocol that you wanted to use and to make sure the client can operate on the network again.Once this is successfully done it is assumed all other network nodes would be able to successfully repeat the same stepsto access the network securely and with the traffic encrypted.

Domain 4.0: Network Management

Domain 4.1: OSI Model

The OSI networking model is divided into 7 layers. Each layer has a different responsibility, and all the layers worktogether to provide network data communication.

Layer Description

ApplicationRepresents user applications, such as software for file transfers, database access, and e-mail. It handlesgeneral network access, flow control, and error recovery. Provides a consistent neutral interface forsoftware to access the network and advertises the computers resources to the network.

PresentationDetermines data exchange formats and translates specific files from the Application layer format into acommonly recognized data format. It provides protocol conversion, data translation, encryption,character-set conversion, and graphics-command expansion.

Session

Handles security and name recognition to enable two applications on different computers tocommunicate over the network. Manages dialogs between computers by using simplex(rare), half-duplexor full-duplex. The phases involved in a session dialog are as follows: establishment, data-transfer andtermination.

TransportProvides flow control, error handling, and is involved in correction of transmission/reception problems. Italso breaks up large data files into smaller packets, combines small packets into larger ones fortransmission, and reassembles incoming packets into the original sequence.

Network

Addresses messages and translates logical addresses and names into physical addresses. It alsomanages data traffic and congestion involved in packet switching and routing. It enables the option ofspecifying a service address (sockets, ports) to point the data to the correct program on the destinationcomputer.

Data Link

The interface between the upper "software" layers and the lower "hardware" Physical layer. One of itsmain tasks is to create and interpret different frame types based on the network type in use. The DataLink layer is divided into two sub-layers: the Media Access Control (MAC) sub-layer and the Logical LinkControl (LLC) sub-layer.

LLC sub-layer starts maintains connections between devices (e.g. server - workstation).MAC sub-layer enables multiple devices to share the same medium. MAC sub-layer maintainsphysical device (MAC) addresses for communicating locally (the MAC address of the nearest routeris used to send information onto a WAN).

PhysicalThe specification for the hardware connection, the electronics, logic circuitry, and wiring that transmit theactual signal. It is only concerned with moving bits of data on and off the network medium. Most networkproblems occur at the Physical layer.

Here is an idiotic, yet easy way to remember the 7 layers. Memorize the following sentence: All People Seem To NeedData Processing. The first letter of each word corresponds to the first letter of the layers starting with Application andending with the physical layer.

Domain 4.3: Evaluate the Network Based on Configuration Management Documentation

The topics covered in this section are either already covered elsewhere, or are too expansive for the purposes of thisguide. Consult your book(s) for more information about these topics.

Domain 4.4: Conduct Network Monitoring to Identify Performance and Connectivity Issues

The topics covered in this section are either already covered elsewhere, or are too expansive for the purposes of thisguide. Consult your book(s) for more information about these topics.

Domain 4.5: Explain Different Methods and Rationales for Network PerformanceOptimization

Quality of Service - (QoS) is a set of parameters that controls the level of quality provided to different types ofnetwork traffic. QoS parameters include the maximum amount of delay, signal loss, noise that can be accommodated fora particular type of network traffic, bandwidth priority, and CPU usage for a specific stream of data. These parametersare usually agreed upon by the transmitter and the receiver. Both the transmitter and the receiver enter into anagreement known as the Service Level Agreement (SLA). In addition to defining QoS parameters, the SLA also describes


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remedial measures or penalties to be incurred in the event that the ISP fails to provide the QoS promised in the SLA.

Traffic Shaping (also known as "packet shaping" or ITMPs: Internet Traffic Management Practices) is the control ofcomputer network traffic in order to optimize or guarantee performance, increase/decrease latency, and/or increaseusable bandwidth by delaying packets that meet certain criteria. More specifically, traffic shaping is any action on a set ofpackets (often called a stream or a flow) which imposes additional delay on those packets such that they conform tosome predetermined constraint (a contract or traffic profile).Traffic shaping provides a means to control the volume oftraffic being sent into a network in a specified period (bandwidth throttling), or the maximum rate at which the traffic issent (rate limiting), or more complex criteria such as GCRA. This control can be accomplished in many ways and formany reasons; however traffic shaping is always achieved by delaying packets. Traffic shaping is commonly applied atthe network edges to control traffic entering the network, but can also be applied by the traffic source (for example,computer or network cardhttp://en.wikipedia.org/wiki/Traffic_shaping - cite_note-2) or by an element in the network.Traffic policing is the distinct but related practice of packet dropping and packet marking.

Load Balancing - is a technique to distribute workload evenly across two or more computers, network links, CPUs,hard drives, or other resources, in order to get optimal resource utilization, maximize throughput, minimize responsetime, and avoid overload. Using multiple components with load balancing, instead of a single component, may increasereliability through redundancy. The load balancing service is usually provided by a dedicated program or hardwaredevice (such as a multilayer switch or a DNS server).

High Availability - (aka Uptime) refers to a system or component that is continuously operational for a desirablylong length of time. Availability can be measured relative to "100% operational" or "never failing." A widely-held butdifficult-to-achieve standard of availability for a system or product is known as "five 9s" (99.999 percent) availability.

Since a computer system or a network consists of many parts in which all parts usually need to be present in order forthe whole to be operational, much planning for high availability centers around backup and failover processing and datastorage and access. For storage, a redundant array of independent disks (RAID) is one approach. A more recentapproach is the storage area network (SAN).

Some availability experts emphasize that, for any system to be highly available, the parts of a system should bewell-designed and thoroughly tested before they are used. For example, a new application program that has not beenthoroughly tested is likely to become a frequent point-of-breakdown in a production system.

Cache Engine - (aka server) is a dedicated network server or service acting as a server that saves Web pages orother Internet content locally. By placing previously requested information in temporary storage, or cache, a cacheserver both speeds up access to data and reduces demand on an enterprise's bandwidth. Cache servers also allow usersto access content offline, including media files or other documents. A cache server is sometimes called a "cache engine."A cache server is almost always also a proxy server, which is a server that "represents" users by intercepting theirInternet requests and managing them for users. Typically, this is because enterprise resources are being protected by afirewall server. That server allows outgoing requests to go out but screens all incoming traffic. A proxy server helpsmatch incoming messages with outgoing requests. In doing so, it is in a position to also cache the files that are receivedfor later recall by any user. To the user, the proxy and cache servers are invisible; all Internet requests and returnedresponses appear to be coming from the addressed place on the Internet. (The proxy is not quite invisible; its IP addresshas to be specified as a configuration option to the browser or other protocol program.)

Fault-tolerance - describes a computer system or component designed so that, in the event that a component fails,a backup component or procedure can immediately take its place with no loss of service. Fault tolerance can be providedwith software, or embedded in hardware, or provided by some combination. In the software implementation, theoperating system provides an interface that allows a programmer to "checkpoint" critical data at pre-determined pointswithin a transaction. In the hardware implementation (for example, with Stratus and its VOS operating system), theprogrammer does not need to be aware of the fault-tolerant capabilities of the machine.

At a hardware level, fault tolerance is achieved by duplexing each hardware component. Disks are mirrored. Multipleprocessors are "lock-stepped" together and their outputs are compared for correctness. When an anomaly occurs, thefaulty component is determined and taken out of service, but the machine continues to function as usual.

Parameters Influencing QOS

Bandwidth - is the average number of bits that can be transmitted from the source to a destination over the networkin one second.

Latency - (AKA "lag") is the amount of time it takes a packet of data to move across a network connection. When apacket is being sent, there is "latent" time, when the computer that sent the packet waits for confirmation that thepacket has been received. Latency and bandwidth are the two factors that determine your network connection speed.Latency in a packet-switched network is measured either one-way (the time from the source sending a packet to thedestination receiving it), or round-trip (the one-way latency from source to destination plus the one-way latency fromthe destination back to the source). Round-trip latency is more often quoted, because it can be measured from a singlepoint. Note that round trip latency excludes the amount of time that a destination system spends processing the packet.Many software platforms provide a service called ping that can be used to measure round-trip latency. Ping performs nopacket processing; it merely sends a response back when it receives a packet (i.e. performs a no-op), thus it is arelatively accurate way of measuring latency.

Where precision is important, one-way latency for a link can be more strictly defined as the time from the start of packettransmission to the start of packet reception. The time from the start of packet transmission to the end of packettransmission at the near end is measured separately and called serialization delay. This definition of latency depends onthe throughput of the link and the size of the packet, and is the time required by the system to signal the full packet tothe wire.

Some applications, protocols, and processes are sensitive to the time it takes for their requests and results to betransmitted over the network. This is known as latency sensitivity. Examples of latency sensitive applications includeVOIP, video conferencing, and online games. In a VOIP deployment, high latency can mean an annoying andcounterproductive delay between a speakers words and the listeners reception of those words. Network managementtechniques such as QoS, load balancing, traffic shaping, and caching can be used individually or combined to optimize thenetwork and reduce latency for sensitive applications. By regularly testing for latency and monitoring those devices thatare susceptible to latency issues, you can provide a higher level of service to end users.

Jitter - Jitter is the deviation in or displacement of some aspect of the pulses in a high-frequency digital signal. As the


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name suggests, jitter can be thought of as shaky pulses. The deviation can be in terms of amplitude, phase timing, orthe width of the signal pulse. Another definition is that it is "the period frequency displacement of the signal from its ideallocation." Among the causes of jitter are electromagnetic interference (EMI) and crosstalk with other signals. Jitter cancause a display monitor to flicker; affect the ability of the processor in a personal computer to perform as intended;introduce clicks or other undesired effects in audio signals, and loss of transmitted data between network devices. Theamount of allowable jitter depends greatly on the application.

Packet Loss - is the failure of one or more transmitted packets to arrive at their destination. This event can causenoticeable effects in all types of digital communications.

The effects of packet loss:

In text and data, packet loss produces errors.In videoconference environments it can create jitter.In pure audio communications, such as VoIP, it can cause jitter and frequent gaps in received speech.In the worst cases, packet loss can cause severe mutilation of received data, broken-up images, unintelligiblespeech or even the complete absence of a received signal.

The causes of packet loss include inadequate signal strength at the destination, natural or human-made interference,excessive system noise, hardware failure, software corruption or overburdened network nodes. Often more than one ofthese factors is involved. In a case where the cause cannot be remedied, concealment may be used to minimize theeffects of lost packets.

Echo - is when portions of the transmission are repeated. Echoes can occur during many locations along the route.Splices and improper termination in the network can cause a transmission packet to reflect back to the source, whichcauses the sound of an echo. To correct for echo, network technicians can introduce an echo canceller to the networkdesign. This will cancel out the energy being reflected.

High Bandwidth Applications - A high bandwidth application is a software package or program that tends torequire large amounts of bandwidth in order to fulfill a request. As demand for these applications continues to increase,bandwidth issues will become more frequent, resulting in degradation of a network system. One way to combat theeffects of these applications on a network is to manage the amount of bandwidth allocated to them. This allows users tostill use the applications without degrading the QoS of network services.

Examples:

Thin ClientsVoice over IPReal Time VideoMulti-media

Domain 4.6: Implement the Following Network Troubleshooting Methodology

Gather Information on the ProblemIn a contact center network, problems are typically discovered and reported by one of the following types of users:

External customers dialing into a call center to order products, obtain customer service, and so forth.Internal agents receiving incoming calls from a call queue or initiating outbound collection calls to customers.Internal users using administrative phones to call employees in other company locations or PSTN destinations,and perform basic actions such as call transfers and dialing into conferences.

As the network administrator, you must collect sufficient information from these users to allow you to isolate theproblem. Detailed, accurate information will make this task easier. As you turn up your network, you may considerputting these questions in an on-line form. A form will encourage users to provide more details about the problem andalso put them into the habit of looking for particular error messages and indicators. Capturing the informationelectronically will also permit you to retrieve and re-examine this information in the future, should the problem repeatitself.

Identify The Affected AreaDetermine if the problem is limited to one workstation, or several workstations, one server, one segment, or the entirenetwork. If only one person is experiencing a certain problem, the problem is most likely at the workstation. If groups ofworkstations are affected, the problem might lie at a part of the network that users all have in common, such as aparticular software application or database, a server, the network segment, or the network configuration.

Determine If Anything Has ChangedTo determine what has changed, ask question such as:

Could you do this task before? If this is a new task, perhaps the user needs different sysetm permissions, oradditional hardware of software.If you could do it before, when did you first notice you couldnt do it anymore? Try do find out what happened justbefore the problem came up, or at least try to pinpoint the time, since the source of the problem might be relatedto other changes elsewhere on the network.What has changed since the last time you were able to do this task? Users can give you information about eventsthat mightaffect their local systems. You can help them with leading questions such as, Did someone addsomething to your computer? or Did you do something differently this time?.

Establish The Most Probable CauseT o establish the most probable cause, use a systematic approach. Eliminate possible causes, starting with the obviousand simplest one and working back through other causes. Do not overlook straightforward and smple corrections thatcan fix a range of problems and do not cost much time or effort to try. You might find you can resolve the issue on thespot.

Determine If Escalation Is NecessaryWhile troubleshooting a network problem, you might find the cause of the problem is not an issue that can be resolvedover the phone or at the users desktop. It may be necessary to contact a fellow employee who has specializedknowledge, or a more senior administrator with the appropriate permissions and authoration. In these cases, theproblem should be escalated to the appropriate personel to be resolved as quickly as possible. Create an Action Plan andSolution, Identifying Potential Effect Once you have determined the probable cause, you should create an action planbefore changes are made, detailing each step taken while attempting to resolve the issue. One should also be certainthat the original state (before troubleshooting) can be returned to in case things do not go as planned. Also consider the


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how the plan will affect the user or other aspects of the network. Thinking ahead can help ensure productivity doesntsuffer and that downtime is minimized.

Implement and Test the SolutionImplement the action plan step by step to fix the problem. If multiple changes are made at once, you will be unable toverify exactly what effect each adjustment had. Be sure to document each step because you can lose sight of what youhave tried in complex troubleshooting scenarios. Test the solution. Make sure the solution implemented actually solvesthe problem and didnt cause any new ones. Use several options and situations to conduct the tests. Sometimes testingover time is needed to ensure the solution is the correct one.

Identify the Results and Effects of the SolutionVerify that the user agrees that the problem is solved before you proceed with final documentation and closing therequest. Even if the problem is solved, and the solution was well thought- out and documented, there might cascadingeffects elsewhere on the local system or on the network. Test for this before closing out the issue. If a major change wasmade, it is advisable to continue monitoring and testing for several days or even weeks after the problem appears to beresolved.

Document the Process and SolutionDocument the problem and process used to arrived at the solution. Maintain the records as part of an overalldocumentation plan. This will provide and ever-growing database of information specific to your network and also it willbe valuable reference material for future troubleshooting instances.especially if the problem is specific to theorganization. Creating a troubleshooting template with required information included in all trouble reports will ensure alltrouble reports are accurate and consistent no matter who completes them.

Domain 4.7: Troubleshoot Common Connectivity Issues and Select an Appropriate Solution

CrosstalkSymptoms: Slow network performance and/or an excess of dropped or unintelligible packets. In telephony applications,users hear pieces of voice or conversations from a separate line.

Causes: Generally crosstalk occurs when two cables run in parallel and the signal of one cable interferes with the other.Crosstalk can also be caused by crossed or crushed wire pairs in twisted pair cabling.

Resolution: the use of twisted pair cabling or digital signal can reduce the effects of crosstalk. Maintaining properdistance between cables can also help.

Near-End CrosstalkSymptoms: Signal loss or interference

Causes: Near-end crosstalk is crosstalk that occurs closer along the cable to the transmitting end. Often occurs in or nearthe terminating connector.

Resolution: Test with cable tester from both ends of the cable and correct any crossed or crushed wires. Verify that thecable is terminated properly and that the twists in the pairs of wires are maintained.

AttenuationSymptoms: Slow response from the network.

Causes: Attenuation is the degradation of signal strength.

Resolution: Use shorter cable runs, add more access points, and/or add repeaters and signal boosters to the cable path.Or, evaluate the environment for interference. The interference you would look for would depend on the spectrum used.

CollisionsSymptoms: High latency, reduced network performance, and intermittent connectivity issues.

Causes: Collisions are a natural part

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