Data Networking.

Data Networking

Lesson 1: Introduction to Data Networking

Objectives Define common network topologies and identify structured cable distribution schemes Identify the major industry bodies and standards, and obtain and read standards documents Identify the layers of the Open Systems Interconnection reference model (OSI/RM), and describe the function of each layer Relate networking and convergence protocols, services and equipment to each OSI/RM layer Explain data encapsulation in relation to frame assembly and function on the network Relate common networking and convergence protocols, services and equipment to each of the four layers of the TCP/IP model

Networks Defined Network – two or more connected computers that share data Host – a computer that participates in a network, often providing services to other computing systems Most networks are: Local area networks (LANs) Wide area networks (WANs)

Data Networks and Convergence
The public switched telephone network (PSTN) is an integral part of the Internet infrastructure Internet Protocol (IP) telephony – a technology that uses packet-switched connections to exchange voice, fax and other forms of data Voice over IP (VoIP) – voice information delivered in digital form as packets of data using IP Communications over Internet Protocol (CoIP) – a set of emerging standards defining transmission of multimedia (text, images, video) over the Internet

Networking Elements and Models
Network elements: Protocols – communication rules on which all network elements must agree Transmission media – media (such as cables or wireless technologies) that enable all networking elements to interconnect Network services – resources that all network users share Networking models: Mainframe – centralized; all processing is performed by the mainframe Client/server – distributed; reduces congestion by dividing processing and storage tasks between the client and the server Web-based – increasingly decentralized and more affordable networking

Network Topologies

Star Topology

Star Bus Hybrid Topology

Partial Mesh Topology

Full Mesh Topology

Network Connections and Cable Distribution
Backbone cabling – used to connect LANs together Campus distributor (CD) – used between routers and switches to connect LANs in different buildings within one general location Vertical cabling – considered part of the backbone and runs between floors in a multi-floor building Building distributor (BD) – the main interface between public or private telecommunications lines coming into a building and the internal network wiring Horizontal wiring – connects individual users to the data or telecommunications network Cross-connect – the point at which one type of wiring or cabling is connected with another

Network Connections and Cable Distribution (cont'd)
Wiring closet – a room or closet that houses all equipment associated with telecommunications wiring systems Floor distributor (FD) – a rack that interconnects wiring between a BD and workstations Patch panel – a group of sockets (usually consisting of pin locations and ports) mounted on a rack Punchdown block – a device that connects one group of wires to another group of wires through a system of metal pins to which the wires are attached

Networking and Telephony Standards Organisations
International Organization for Standardization (ISO) International Telecommunications Union (ITU) Institute of Electrical and Electronics Engineers (IEEE) Electronic Industries Alliance / Telecommunications Industry Association (EIA/TIA) Communications Information Technology Association (CITA) European Telecommunications Standards Institute (ETSI)

Networking and Telephony Standards Organisations (cont'd)
Independent Committee for the Supervision of Standards of Telephone Information Services (ICSTIS) American National Standards Institute (ANSI) Telcordia (formerly Bellcore) Internet Society (ISOC) Internet Architecture Board (IAB) Internet Research Task Force (IRTF) Internet Engineering Task Force (IETF)

OSI Reference Model Layer Layer Number Application 7 Presentation 6
Session 5 Transport 4 Network 3 Data link 2 Physical 1

Network Communication

OSI Protocol Examples Application-layer protocols
SIP, H.323, MGCP, SMTP, POP3, HTTP, DNS, BOOTP, FTP, Telnet, LDAP Presentation-layer protocols ASN.1, Codecs Session-layer protocols RTCP, NetBIOS, SQL, ASP Transport-layer protocols RTP, TCP, UDP, ATP Network-layer protocols IP, ICMP, ARP, DDP Data link-layer protocols 802.2, 802.3, Physical layer Network hardware or technologies

Packet Creation – Adding Headers

Data Encapsulation Data – the application, presentation and session layers Segment – the transport layer Packet – the network layer Frame – the data link layer Cyclical redundancy check (CRC) – verifies whether a packet is valid Imagine a packet as a package being shipped to you: The CRC would be considered a packing slip or a bill of lading

Packets Packet structure: Header Data Trailer

Introduction to TCP/IP
Transmission Control Protocol / Internet Protocol (TCP/IP) – the current de facto standard for both local and wide area networking TCP/IP four-layer model: Application layer – interacts with the transport-layer protocols to send or receive data Transport layer – provides the flow of information between two hosts Network/Internet layer – addresses and routes packets on TCP/IP networks Link/network access layer – accepts higher-layer packets, creates frames and transmits them over the attached network

TCP/IP Model vs. OSI Model

Summary Define common network topologies and identify structured cable distribution schemes Identify the major industry bodies and standards, and obtain and read standards documents Identify the layers of the Open Systems Interconnection reference model (OSI/RM), and describe the function of each layer Relate networking and convergence protocols, services and equipment to each OSI/RM layer Explain data encapsulation in relation to frame assembly and function on the network Relate common networking and convergence protocols, services and equipment to each of the four layers of the TCP/IP model

Lesson 2: Transmission, Communication and Wiring

Objectives Compare and contrast the use of E-carrier, T-carrier, SONET/SDH and ISDN technologies for data and voice networks, including bandwidths of common technologies Identify cable terminators Define and contrast data communications equipment (DCE) and data terminating equipment (DTE) Identify network media, and identify proper cabling procedures in specific environments Compare and contrast straight-through, crossover, rolled and null-modem cabling

Transmission Types Synchronous transmission
Access device and network device share a clock Asynchronous transmission No clock in the transmission media Data transmission flow Simplex – data travels in only one direction Half duplex – data travels in two directions, but in only one direction at a time Full duplex – data travels in two directions simultaneously Baseband and broadband transmissions Baseband – uses entire media bandwidth for a single channel Broadband – divides the media bandwidth into multiple channels, and each channel carries a separate signal

Digital Signaling Digital signal level zero (DS0) – the basic level of digital communication upon which all other digital signaling levels are built Digital Signal Hierarchy (DSH) – an electrical (as opposed to optical) hierarchy used to classify the speed capacities of multiplexed lines T-carrier system – a North American high-speed digital carrier system used to transmit data E-carrier system – a European high-speed digital carrier system used to transmit data in almost all countries outside the United States, Canada and Japan

Digital Signaling (cont'd)
Integrated Services Digital Network (ISDN) – a completely digital service capable of carrying voice, fax, imaging or data communications Synchronous Optical Network (SONET) – a North America high-speed fiber-optic system for optical transmissions Synchronous Digital Hierarchy (SDH) – an international high-speed fiber-optic system for optical transmissions

DSH and T-Carrier Equivalents

T-Carrier vs. E-Carrier Speeds

Integrated Services Digital Network (ISDN)
ISDN configurations: 2B+D – also known as Basic Rate Interface (BRI). Intended for home use. Uses two 64-Kbps B channels and one 16-Kbps D channel 23B+1D – available in the United States and Japan. Intended for business use. Designed for 23 B channels plus one D channel 30B+2D – also known as Primary Rate Interface (PRI). Available in Europe. Intended for business use. Designed for 30 B channels and two D channels

Synchronous Optical Network (SONET)

Synchronous Digital Hierarchy (SDH)

Benefits of Using SONET/SDH
It is possible to use multiplexers and routers to combine different data lines and streams onto one line One heterogeneous network can communicate with another distant heterogeneous network

Common Peripheral Ports
Serial ports Universal Serial Bus (USB) FireWire (IEEE 1394) Parallel ports PS/2 connectors Small computer system interface (SCSI) Amphenol connectors

Serial Ports Serial ports are computer sockets that connect serial devices to a computer Use two types of connectors: DB-9 (9-pin) – usually COM1 DB-25 (25-pin) – usually COM2 and used for modem

Universal Serial Bus (USB)
USB interface may replace serial and parallel ports USB allows up to 127 devices to be daisy-chained using one USB port Two USB standards: USB 1.0 offers transfer rate of 12 Mbps for fast devices (and 1.5 Mbps for slow devices) USB 2.0 offers transfer rate of up to 480 Mbps Two USB connectors: Type A is rectangular and relatively small. All permanent connections use the Type A connector Type B is square and is only used for devices that use a separate cable

FireWire (IEEE 1394) A serial bus especially popular for attaching video devices to computers Allows up to 63 devices to be daisy-chained Supports hot swapping Guarantees bandwidth for multimedia Two FireWire versions: IEEE 1394a supports data transfer rates of up to 400 Mbps IEEE 1394b supports data transfers of 800 to 1,200 Mbps

Parallel Ports Parallel ports are computer sockets that connect a printer or any other parallel device to a computer Enhanced using the IEEE 1284 standard, which provides bi-directional transfers and increased speeds Parallel cables can be 32 feet long

PS/2 connectors Used to connect a keyboard or a mouse to a computer
6-pin circular connector Used on all laptops and PCs

Small Computer System Interface (SCSI)
SCSI is a parallel interface that allows two devices to communicate at the same time Allows seven to 15 devices to be daisy-chained Last device in a daisy chain must have a SCSI terminator Three types of SCSI connectors: 25-pin (SCSI-1) 50-pin (SCSI-2) 68-pin (SCSI-3)

Amphenol Connectors Often used in patch cables for connecting 66 and 110 punchdown blocks

Transmission Media Free space transmission media: Infrared
Short-range wireless Microwave Satellite Cable transmission media: Twisted-pair cable Coaxial cable Fiber-optic cable

Free Space Transmission
Infrared (IR) – wireless communication in which signals are sent via light waves that are longer than those of the visible light spectrum Short-range wireless – used for networking PCs and for connecting a PC to peripherals The most common standard for peripheral device communications is Bluetooth Microwave – signals sent by line-of-sight transmission via parabolic antennas mounted on towers Satellite – transmits information between two stations that are not within the line of sight of each other

Twisted-Pair Cable Maximum segment length of 100 metres
Available in two basic types: Shielded (STP) – twisted copper wrapped in a metal sheath; more difficult to install and maintain than UTP Unshielded (UTP) – most common; less expensive than STP, but prone to electromagnetic interference STP and UTP are available in two varieties: Stranded – most common; flexible and easy to handle around corners and objects Solid – can span longer distances, but less flexible and will break if bent multiple times

Twisted-Pair Categories
Category Description 1 Used for voice only, not data 2 4 Mbps; used for voice and data 3 10 Mbps; standard station wire 4 16 Mbps; used for voice 5 100 Mbps; Ethernet and Fast Ethernet 5e Fast Ethernet and Gigabit Ethernet; largely replaces Cat 5 6 Gigabit Ethernet; more fragile than other categories of twisted pair 7 1 Gbps; will replace coax cable because it can support cable TV

Twisted-Pair Cable Types
Straight-through cable – the transmit wires on one end of the cable connect to the transmit wires on the opposite end of the cable Crossover cable – the transmit wires on one end will connect to the receiving wires on the other end, and vice versa Rolled cable – a serial cable in which one end of the cable is wired as the mirror image of the other end Null-modem cable – an RS-232 serial cable in which the transmit and receive lines are cross-linked

Coaxial Cable Used for video and communication networks
Provides higher bandwidth than twisted-pair cable Designed for baseband, broadband and television networks Supports data transfer rates from 1 Mbps to 100 Mbps Transfer rate of 10 Mbps common for LAN Common types: RG-6, RG-11, RG-59 Uses the F-type connector:

Common Coax Cable Types
Segment Length Use RG-6 N/A TV and video; similar to RG-59 but for longer distances RG-11 500 m Broadband LAN connections RG-59 305 m Cable TV, video; often for short distances (e.g., 6 feet)

Fiber-Optic Cable Sends data as pulses of light over threads of glass
Transfer rates in the gigabits-per-second range Transmissions can travel for miles without attenuation Immune to electromagnetic interference (EMI) Two major types: Single-mode fiber (SMF) – offers extremely high bandwidth and long distances (up to 70 km) Multimode fiber (MMF) – allows for use of inexpensive light sources and used for short distances (less than 200 m); typically specified for LANs and WANs

Fiber-Optic Connectors
ST (straight tip) connector – connects one optical fiber using a one-piece bayonet mounting system; widely implemented in commercial wiring SC (subscriber or standard) connector – connects fiber-optic cable using a plug and socket with a push-pull latch Fiber LC (local) connector – half the size of a standard ST or SC connector; designed to save space on patch panels MT-RJ (mechanical transfer registered jack) – about the same shape and size as an RJ-45, and can be used with single-mode or multimode fiber

Proper Cabling Procedures
When pulling cable: Ensure that you have cleared a proper path Avoid sharp bends in the cable Take care to eliminate sharp edges in conduits and other areas where cable might get worn or cut Make sure that wiring does not interfere with mechanical equipment Avoid passing wire close to fluorescent lights

Proper Cabling Procedures (cont'd)
The standard jacket of a UTP or STP cable is made of polyvinyl chloride (PVC), which if burned creates toxic polyvinyl chloride gas Two options to PVC cabling are available: Encase the cable in a protective metal conduit Use limited combustible cabling, which has a Teflon or Kevlar jacket

Summary Compare and contrast the use of E-carrier, T-carrier, SONET/SDH and ISDN technologies for data and voice networks, including bandwidths of common technologies Identify cable terminators Define and contrast data communications equipment (DCE) and data terminating equipment (DTE) Identify network media, and identify proper cabling procedures in specific environments Compare and contrast straight-through, crossover, rolled and null-modem cabling

Lesson 3: LANs and WANs

Objectives Relate networking and convergence protocols, services and equipment to each OSI/RM layer Identify the functions of routers, switches, firewalls, core and edge networks, modems and hubs in relation to data networking hardware Explain the format and function of Media Access Control (MAC) addresses Define the Spanning Tree Protocol (STP) Define networking methods, standards and protocols, and their characteristics Explain the concept of protocol tunneling, and identify elements and benefits of using a Virtual Private Network (VPN) in a convergent network

Objectives (cont'd) Identify wireless networking equipment functionality and standards Identify and describe common security issues inherent to wireless networks Explain the functions of Wired Equivalent Privacy (WEP), i/WiFi Protected Access (WPA), 802.1x and Remote Authentication Dial-In User Service (RADIUS) Identify critical settings in an access point (AP) Describe wireless client settings, including authentication, encryption, preferred networks, channels

Basics of LANs and WANs Local area network (LAN):
A group of computers connected by transmission media within a confined geographic area Often consists of workstations and servers Wide area network (WAN): A group of computers connected over an expansive geographic area, such as a state or country Often connects two LANs using the communications lines of a public carrier, such as the PSTN

Common Network Components
Network interface card (NIC) Repeaters Hubs Bridges Routers Switches Gateways Network termination equipment (NTE) Firewalls Modems

Network Interface Card (NIC)
Makes the physical connection between the computer and the network cabling Operates at the data link layer (Layer 2) of the OSI/RM Requires a device driver Every NIC has a MAC address Can be attached to a computer by: PCI card PCMCIA card USB FireWire Wireless

Protocols and the NIC Network Device Interface Specification (NDIS) and Open Data-Link Interface (ODI): Allow a NIC to be chosen independently from the protocols, network operating system (NOS) or applications that will be used Enable multiple protocols to be bound to a single NIC Enable the use of multiple NICs in the same computer Note: ODI is similar to NDIS but was defined by Novell and Apple to simplify driver development

MAC Addresses Unique addresses that are burned on a NIC by the manufacturer Use 12 hexadecimal digits to form a 48-bit address Organisationally Unique Identifier (OUI) – identifies the vendor that created the NIC Interface Serial Number – a number unique to the vendor

Repeaters Repeat or regenerate the electronic signal from one LAN cable to another, extending the range of the signal Operate at the physical layer (Layer 1) of the OSI/RM

Hubs Connect multiple devices into the same collision domain
Operate at the physical layer (Layer 1) of the OSI/RM

Bridges Filter frames to determine whether a specific frame belongs on a local segment or another LAN segment Connect networks with the same or different data link protocols Operate at the data link layer (Layer 2) of the OSI/RM Independent of all upper-layer protocols Largely replaced by switches in modern Ethernet networks because switches are faster

Routers Forward, or route, data from one network to another
Operate at the network layer (Layer 3) of the OSI/RM Instead of using MAC addresses, routers use IP or IPX addresses to forward or route data from one network to another

Switches Direct the flow of information from one node to another
Operate at the data link layer (Layer 2) of the OSI/RM Types of switches: Layer 1 – connects individual systems Layer 2 – forwards traffic based on MAC addresses Layer 3 – connects networks Layer 4 – forwards traffic between source and destination hosts

Spanning Tree Protocol (STP)
Redundancy in a network eliminates the possibility of single points of failure STP identifies one switch from each pair of redundant switches as the designated switch STP allows switches to communicate with one another to bypass a failed switch STP is defined in the IEEE 802.1d standard Rapid Spanning Tree Protocol (RSTP) – an evolved version of 802.1d, which allows for faster spanning-tree convergence after a network topology change GARP VLAN Registration Protocol (GVRP) – a protocol that allows for automatic configuration of switches in a VLAN environment

Benefits of Using Switches
Simple installation – Unplug connections from existing devices and plug the connections into the switch ports Higher speeds – Switches allow full bandwidth between any two users or segments More server bandwidth – Servers can connect directly to switches Creation of virtual LANs (VLANs) – VLANs allow you to organise systems according to their logical functions on the network, as opposed to their physical locations More default security – Using a VLAN, you can isolate individual systems

Gateways Also called protocol converters
Can operate from the transport layer (Layer 4) through the application layer (Layer 7) of the OSI/RM Convert one protocol stack into another Can be used to connect networks with dissimilar protocols or architectures Note: Do not confuse a gateway (protocol converter) with a default gateway (router)

Network Termination Equipment (NTE)
The location where customer data or telephone equipment connects to external lines from the carrier Protects the public and private networks from power spikes Provides a testing interface Converts the carrier's signals into signals for use on the LAN Provides timing information Performs multiplexing and signaling

CSU/DSU Channel Service Unit / Data (or Digital) Service Unit
Terminates physical connections Required when using dedicated circuits such as T1 lines Operates at the physical layer (Layer 1) of the OSI/RM

Firewall A secure computer system placed between a trusted network and an untrusted one, such as the Internet Acts as a barrier against potential malicious activity Allows a “door” for people to communicate between a secured network and the open, unsecured network A network firewall is most commonly placed between a corporate LAN and the Internet

Modems Traditionally, a modem is a device that enables computers to communicate over phone lines by translating digital data into audio/analogue signals and then back into digital form “Modem” now refers to any device that adapts a computer to a phone line or cable TV network, whether it is digital or analogue Analogue modems translate digital data into analogue signals and then back into digital form DSL and cable modems are all-digital

IEEE LAN Standards Institute of Electrical and Electronics Engineers (IEEE) – an organisation of professionals that creates standards for computers and communications IEEE 802 network standards: IEEE – Logical Link Control (LLC) function IEEE – Ethernet IEEE 802.3u – Fast Ethernet IEEE 802.3z and 802.3ab – Gigabit Ethernet IEEE 802.3ae (supplement) – 10-Gigabit Ethernet

WAN Methods and Standards
X.25 Fast packet switching Frame relay Asynchronous transfer mode (ATM) Peer-to-peer networking Point-to-Point Protocol (PPP) Point-to-Point Protocol over Ethernet (PPPoE)

X.25 Defines how connections between user devices and network devices are established and maintained Implemented at the network layer (Layer 3) of the OSI/RM Uses two types of virtual circuits: Switched virtual circuit (SVC) – a temporary connection used for sporadic data transfers Permanent virtual circuit (PVC) – a permanently established connection used for frequent and consistent data transfers

Fast Packet Switching Tasks such as error correction, packet sequencing and acknowledgments are not performed by the network Implemented at the MAC sublayer of the OSI/RM data link layer (Layer 2) Technologies include frame relay and asynchronous transfer mode (ATM)

Frame Relay A packet-switching technology used for WANs and LAN-to-LAN connections that supports data and voice Organises data into variable-length packets called frames

Asynchronous Transfer Mode (ATM)
A cell-switching or cell-relay technology ATM replaces variable-length packets with uniform 53-octet cells Primarily a connection-oriented service that supports real-time voice and video, as well as data Can transport both connection and connectionless services Performs at the data link layer (Layer 2) of the OSI/RM

Peer-to-Peer Networking
A networking model in which each computer has both client and server capabilities P2P is a peer-to-peer network on the Internet P2P advantages: Cost – Because P2P networks are used on the Internet, an existing, reliable infrastructure is already in place Reliability – Clients use their own network connections, creating a reliable network Load distribution – Clients download files from multiple locations, which helps keep any one location from being overburdened

Point-to-Point Protocol (PPP)
A communications protocol that allows a computer to connect to the Internet over a phone line Used to send and receive IP data packets using a modem Enables TCP/IP to run on a Layer 1 link Multilink Point-to-Point Protocol (MLPPP) – combines two PPP connections into one, thereby enabling a higher transmission speed

Point-to-Point Protocol over Ethernet (PPPoE)
A communications protocol based on PPP that is used with direct Internet connections Enables a point-to-point connection using Ethernet as the transport Used mainly with ADSL services

Remote Access Concepts
Term Description Connection medium The physical connection method used in any given network Remote access server A dedicated server or collection of servers configured to accept connections Perimetre The outer edge of the network, as defined by a firewall Topology The physical layout of a particular network Firewall A dedicated device that helps create a network perimetre by filtering out packets

Remote Access Methods Term Description Virtual Private Network (VPN)
The use of encryption to establish a dedicated, encrypted connection between two hosts Remote Authentication Dial-In User Service (RADIUS) A means of centralizing authentication information in dial-up connections IPsec A series of protocols and methods designed to encrypt transmissions between hosts at the network layer (Layer 3) of the OSI/RM IEEE 802.1x A method for securing wireless networks by centralizing authentication between multiple wireless access points

Authentication and Authorization
Authentication – the process of determining the identity of a user, a network host or an application process Authorization – the act of recognizing an authenticated user, network host or process defined on a particular host or authentication system

Encryption A security technique designed to prevent access to information by converting it into a scrambled (unreadable) form of text Three encryption models: Symmetric-key Asymmetric-key Hash

Symmetric-Key (Single-Key) Encryption
One key is used to encrypt and decrypt messages All parties must know and trust one another completely, and have confidential copies of the key Three most common symmetric algorithms: Data Encryption Standard (DES) Triple DES Advanced Encryption Standard (AES)

Asymmetric-Key (Public-Key) Encryption
Uses a key pair in the encryption process Key pair – a mathematically matched key set in which one key encrypts and the other key decrypts One of these keys is made public, whereas the other is kept private Two most common asymmetric-key algorithms: Rivest, Shamir, Adleman (RSA) Digital Signature Algorithm (DSA)

Hash (One-Way) Encryption
Uses an algorithm to convert information into a fixed, scrambled bit of code Any data that has been run through a hash algorithm cannot be decrypted Two most common hash algorithm families: Message Digest (MD) MD2 MD4 MD5 Secure Hash Algorithm (SHA)

Services Provided by Encryption
Explanation Method Data confidentiality Ensures that only the intended recipients of information can view it Symmetric-key, asymmetric-key Data integrity Applies digital signatures to ensure that data is not illicitly decrypted Hash Authentication Proves identity Asymmetric-key, in conjunction with hash Non-repudiation Proves that a transaction has, in fact, occurred Asymmetric-key, hash

Digital Certificates and Digital Signatures
Digital certificates are small files that provide authoritative identification A certificate authority (CA) verifies the legitimacy of a digital certificate Digital certificates contain digital signatures, which are unique identifiers that authenticate messages Digital signatures provide the following services: Authentication Non-repudiation Data integrity Note: Digital signatures do not provide data confidentiality

Virtual Private Networks (VPNs)
VPN is an encrypted tunnel that provides secure, dedicated access between two hosts across an unsecured network Three types of VPNs: Workstation-to-server Firewall-to-firewall Workstation-to-workstation

VPNs and Protocol Tunneling
Tunneling protocol – a protocol that encapsulates data packets into other network packets Tunneling Component Description Passenger protocol The protocol being placed into the encrypted tunnel Encapsulation protocol Responsible for properly encrypting data to provide confidentiality and integrity Transport protocol Carries the tunnel packets that contain the passenger protocol(s)

Point-to-Point Tunneling Protocol (PPTP)
Used to create VPN connections between a client and a centralized server Capable of tunneling and encrypting connections across multiple networks PPTP works at the data link layer (Layer 2) of the OSI/RM PPTP supports only IP

Layer 2 Tunneling Protocol (L2TP)
Primarily used to support VPNs over the Internet for non-TCP/IP protocols L2TP is an open standard L2TP uses enhanced compression techniques L2TP supports various network types L2TP supports RADIUS and many different protocols L2TP does not provide encryption by itself

IP Security (IPsec) An IETF standard that provides packet-level encryption, authentication and integrity between firewalls or between hosts in a LAN Contains two elements: Authentication Header (AH) – signs the packets to ensure authentication and data integrity Encapsulating Security Payload (ESP) – encrypts the data payload Two connection modes: Tunnel mode – the header and the data packet are encrypted Transport mode – only data is encrypted

VPN Benefits Expand connectivity – VPNs allow you to use the Internet to log on to an internal network Save money – Companies can implement VPNs between their remote offices and eliminate the use of expensive private leased lines Improve security – VPN transmissions are usually encrypted Support telecommuting – Users can securely log on to the corporate network from home

VPN Vulnerabilities Man-in-the-middle attacks – Weak VPN connections are vulnerable to attempts to alter messages in transit Old access accounts and permissions – VPN servers use their own accounts databases; old accounts may be present, which could allow unauthorised access to the network Access from unsecured systems – Remote systems may present a new infection source to the network Security dependent on VPN clients – If employees use unsecured connections at their end, network privacy and security can become compromised

Wireless Technologies
Enable the operation of mobile phones and wireless network connections Schemes for allocating channels in a mobile network: Frequency Division Multiple Access (FDMA) – divides the frequency band into channels, each of which can carry a voice conversation or data Time Division Multiple Access (TDMA) – allows several users to share the same frequency channel Code Division Multiple Access (CDMA) – assigns a unique code to each voice call

Global System for Mobile Communications (GSM)
A digital cellular phone technology that supports voice and short message service Based on TDMA Currently the most popular mobile phone system in the world

General Packet Radio Service (GPRS)
Mobile data service used for wireless AP access, short message service, and Internet access Three capability classes: Class A – device can be connected to GPRS service and GSM service, and can use both at the same time Class B – device can be connected to GPRS and GSM service, but can use only one or the other at a given time Class C – device is connected to either GPRS or GSM service

WiFi and Dual Cell Phones
WiFi (Wireless Fidelity) – generically refers to any type of wireless network WiFi provides high-speed data connections between mobile devices and WiFi access points using short-range wireless transmissions Dual cell phones – phones that can use both a cell network and a WiFi network

Wireless Signals Wireless networks use the following types of spread spectrum transmissions: Frequency Hopping Spread Spectrum (FHSS) – changes the frequency of a transmission at regular intervals Direct Sequence Spread Spectrum (DSSS) – signal is spread over the entire band at once Orthogonal Frequency Division Multiplexing (OFDM) – splits a signal into smaller sub-signals that are transmitted simultaneously on different frequencies

Wireless Networking Modes
Ad-hoc – systems use only their NICs to connect with each other Infrastructure – systems connect via a centralized wireless access point (AP)

Wireless Ethernet Equipment
Essential wireless Ethernet elements include: Wireless NIC Wireless access point (AP) Configuration software Antenna Beacon Service Set Identifier (SSID)

IEEE 802.11 Wireless Standards
(WiFi) – original specification providing for data rates of 1 Mbps or 2 Mbps in the 2.4-GHz band using either FHSS or DSSS 802.11a – operates at 54 Mbps in the 5-GHz band; uses OFDM 802.11b – operates at 11 Mbps in the 2.4-GHz band; uses DSSS 802.11e – provides Quality of Service (QoS) standards for wireless networks 802.11g – operates at up to 54 Mbps in the 2.4-GHz band; uses OFDM or DSSS 802.11h – solves problems with wireless networks operating in the 5-GHz band from interfering with satellites and radar 802.11i – specifies wireless security enhancements

Wireless Network Security Issues
Common security problems with wireless networks include: Cleartext transmissions Access control Unauthorised APs and wireless systems Corporate users participating in ad hoc networks Weak and/or flawed encryption Encryption and network traffic War driving

Wireless Network Security Solutions
Wired Equivalent Privacy (WEP) – encrypts all data packets sent between wireless clients and the AP MAC address filtering – limits access to your network by configuring the AP to allow only certain system MAC addresses to communicate with the rest of the network WiFi Protected Access (WPA) – a specification of security enhancements for WiFi networks IEEE 802.1x – authenticates users who want to access x wireless networks Remote Authentication Dial-In User Service (RADIUS) – a popular method for centralizing remote user access

Wireless Network Configuration Settings
Access point settings: SSID Channel Broadcast of SSID frames Authentication mode – either open or shared key Keys for shared key access, if shared key authentication is to be used Encryption level – 40-bit, 64-bit, 128-bit or 256-bit

Wireless Network Configuration Settings (cont'd)
Wireless client settings: The networks to which you want to connect The channel used by each network The authentication mode (whether open or shared key) used by the access point Security settings, which include a shared key (if shared-key authentication is used) and the encryption level

Attaching an Access Point to a Wired Network
A wireless access point also has an RJ-45 plug that allows you to attach it to a standard, wired Ethernet network All wireless clients will then be able to access all of the services available to standard Ethernet clients

Summary Relate networking and convergence protocols, services and equipment to each OSI/RM layer Identify the functions of routers, switches, firewalls, core and edge networks, modems and hubs in relation to data networking hardware Explain the format and function of Media Access Control (MAC) addresses Define the Spanning Tree Protocol (STP) Define networking methods, standards and protocols, and their characteristics Explain the concept of protocol tunneling, and identify elements and benefits of using a Virtual Private Network (VPN) in a convergent network

Summary (cont'd) Identify wireless networking equipment functionality and standards Identify and describe common security issues inherent to wireless networks Explain the functions of Wired Equivalent Privacy (WEP), i/WiFi Protected Access (WPA), 802.1x and Remote Authentication Dial-In User Service (RADIUS) Identify critical settings in an access point (AP) Describe wireless client settings, including authentication, encryption, preferred networks, channels

Lesson 4: TCP/IP Suite and Internet Addressing

Objectives Identify common ports and services
Define common internal and external routing protocols, and distinguish between internal and external routing protocol functions Explain dynamic, static and default routes, and describe the function of routing tables Compare and contrast connection-oriented and connectionless transport Define and identify well-known, registered and random/dynamic ports Compare and contrast the IPv4 and IPv6 address formats Determine the network address/number when given a host address and subnet mask Identify network, host and broadcast addresses Define unicasting, broadcasting, multicasting and anycasting

Objectives (cont'd) Explain private network addressing
Identify the importance of the subnet mask Identify the subnet mask by bit count and by dotted decimal notation, and define Classless Interdomain Routing (CIDR) Determine the number of host addresses in a subnet Describe the impact of proxies on convergent network communications Explain Network Address Translation (NAT) Identify Domain Name System (DNS) features and functions Explain functions and benefits of automatic addressing including protocol steps, and troubleshooting handsets, PCs and all IP-enabled devices Determine which Internet Protocol (IP) version to implement (e.g., IPv4 vs. IPv6)

TCP/IP Transmission Control Protocol / Internet Protocol (TCP/IP) – allows computers from different vendors with various operating systems and capabilities to communicate Internet Protocol (IP) address – The numerical address assigned to a specific computer that uniquely identifies and distinguishes a node from any other node on the Internet

TCP/IP Architecture

Introduction to Routing
Routing – the process of selecting a path over which to send packets in a network Router – a device that routes data packets between networks based on network-layer addresses The network layer (Layer 3) performs the routing function Two general classifications: Direct routing Indirect routing

Direct vs. Indirect Routing
Direct routing – when two computers on the same physical network need to communicate, the packets do not require a router Indirect routing – When two computers that are not on the same physical network need to communicate, they must send the IP packet to a router for delivery because they are located on remote networks

The Routing Process Routing involves the following two key elements:
The host must know which router to use for a given destination; the router is determined by the default gateway The router must know where to send the packet; the destination is determined by the router's routing information table

Routing Information Tables
Routing information table – a database maintained by a router Contains the location of all networks in relation to the router's location

Static vs. Dynamic Routing
Static router – contains a routing information table that must be built and updated manually by a system administrator Dynamic router – communicates with other dynamic routers to calculate routes automatically using routing protocols such as RIP and OSPF Default route – the network route used by a router when no other known route exists for a given destination IP address

Internal vs. External Routing Protocols
Internal routing protocols – used within an organisation’s network Routing Information Protocol (RIP) Open Shortest Path First (OSPF) External routing protocols – used outside an organisation’s network Exterior Gateway Protocol (EGP) Border Gateway Protocol (BGP)

Distance-Vector Routing Protocols
Distance-vector routing protocol – designed to allow a router to inform neighbouring routers about the contents of its routing table Four common distance-vector routing protocols: Routing Information Protocol 2 (RIPv2) Interior Gateway Routing Protocol (IGRP) Enhanced Interior Gateway Routing Protocol (EIGRP) Exterior Gateway Protocol (EGP)

Link-State Routing Protocols
Link-state routing protocol – gathers network statistics to create a network map so that routing tables can be altered accordingly Two common link-state routing protocols: Open Shortest Path First (OSPF) Border Gateway Protocol v4 (BGPv4)

Internet Group Management Protocol (IGMP)
Internet Group Management Protocol (IGMP) – used on routers that support multicast groups Multicast – a transmission that is sent to a group of network hosts via a single IP address IP hosts use IGMP to register their membership in a multicast group

Data Fragmentation and the Maximum Transmission Unit (MTU)
Data fragmentation – if a packet is too large for any of the routers encountered along the way, the oversized packets will be fragmented Maximum transmission unit (MTU) – the maximum size of a packet or frame on the network; most networks impose a limit on bytes of data per packet

Connection-Oriented vs. Connectionless Protocols
Connection-oriented protocols – gain a system's attention, prepare it to receive information, then send the information An example of a connection-oriented protocol is Transmission Control Protocol (TCP) Connectionless protocols – rely on a “best-effort” technology that sends the information, hoping that it will reach the other system An example of a connectionless protocol is Internet Protocol (IP)

Port Numbers Port Number Range Description Uses 0 to 1023
Well-known (reserved) port numbers Used by TCP and UDP to identify well-known services that a host can provide 1024 to 49151 Registered port numbers Any process or user can open this range of ports 49152 to 65535 Dynamic port numbers Any client-side application can open these ports randomly when accessing remote hosts

Internet Addressing Internet addresses are specified by four fields, separated by periods: field1.field2.field3.field4 Each field represents one byte of data, and has a value ranging from 0 to 255 In a dotted quad IP address, the first set of numbers on the left represents the largest network; the last number in the address (on the far right) identifies the specific computer

Decimal vs. Binary Format
To determine the value of an Internet address, you must convert from decimal to binary If the binary value of an IP address is , you can determine the decimal value by adding the corresponding bit values that equal = =121

Decimal vs. Hexadecimal
The hexadecimal numbering system uses the digits 0 through 9, and the letters A through F A=10; B=11; C=12; D=13; E=14; F=15

Internet Address Classes

Internet Address Classes (cont'd)
Class A – range to Class B – range to Class C – range to Class D – range 224 to 239 (network address only) Class E – range 240 to 247 (network address only – reserved for future use)

IP Addressing Rules Loopback address 127 address range
Broadcast address 255 Network address If the host portion of an IP address is all zeros, then that address is a network address Special-case source address – used for requesting an IP address from a DHCP or BOOTP server Multicasting Allows a device to send to a group of devices through one IP address

Private IP Addressing Private network addresses are not Internet-addressable Class Private IP Address Range Subnet Mask Class A to Class B to Class C to

Subnetworks Subnetworks offer a way to organise hosts within a network into logical groups Subnet masks: Distinguish the network and host portions of an IP address Specify whether a destination address is local or remote ANDing is a function that a computer uses with its local IP address and local subnet mask in order to determine whether a destination address is local or remote

Custom Subnet Masks Step 1: Determine the number of subnets needed
Step 2: Determine the number of bits to borrow from the host portion Step 3: Determine the subnet mask Step 4: Determine the maximum number of hosts per subnetwork Step 5: Determine the subnetwork addresses for each subnet Step 6: Determine the address ranges for each subnetwork

Classless Interdomain Routing (CIDR)
Classless Interdomain Routing (CIDR) – a method used to minimize the number of routing table entries The basic concept in CIDR is to allocate multiple IP addresses so they can be summarized into a smaller number of routing table entries This strategy relieves routers of additional workload

IP Address Conservation
Proxy servers: Replace the network IP address with another, contingent address. Allow a network to be represented by one IP address on the Internet Network Address Translation (NAT): The process of translating one IP address into another NAT allows system administrators to use any IP addressing scheme internally, and one or more registered IP addresses externally

Network Address Translation (NAT)
Types of NAT: Port Address Translation (PAT) – multiple IP addresses are translated into one valid IP address Static address translation – multiple IP addresses are mapped to valid IP addresses in a one-to-one relationship Dynamic address translation – multiple IP addresses are mapped to valid IP addresses randomly

IP-Enabled Device Configuration Parametres
Basic configurations: IP address Subnet mask Default gateway DHCP client DNS server

IP-Enabled Device Configuration Parametres (cont'd)
Additional TCP/IP services: Service Description Domain Name System (DNS) service Resolves names to IP addresses Windows Internet Naming Service (WINS) A Windows system name resolution service that runs automatically and does not require configuration Automatic Private IP Addressing (APIPA) Used if a modern Windows client fails to obtain an address from a DHCP server

IP-Enabled Device Configuration Parametres (cont'd)
Name resolution configurations: Host name Domain name DNS server NetBIOS name WINS server

Domain Name System (DNS)
DNS translates IP addresses into easily recognizable names Domain name syntax:

DNS Hierarchy Root-level domain – contains entries for each top-level domain Top-level domain – consists of categories found at the end of domain names (such as .com or .uk) Second-level domain – include the businesses and institutions that register their domain names with the top-level domains

DNS Components DNS consists of two key components:
Name server – a server that supports name-to-address translation and runs the DNS service Name resolver – software that uses the services of one or more name servers to resolve unknown requests

DNS Server Types DNS follows the standard client/server model: The client makes a request, and the server attempts to fulfill that request Server types included in the DNS model: Root server Primary server Secondary server Caching-only server Forwarding server

DNS Records DNS Record Function Name Server (NS)
Identifies DNS servers for the DNS domain Start Of Authority (SOA) Identifies the DNS server that is the best source of information for the DNS domain Address (A) Associates a host to a 32-bit IPv4 address Address (AAAA) Associates a host name to a 128-bit IPv6 address Canonical Name (CNAME) Creates an alias for a specified host Pointer (PTR) Maps an IPv4 address to the canonical name for that host Mail Exchanger (MX) Identifies a server used to process and deliver messages for the domain Service (SRV) Allows you to specify a server for a particular address Naming Authority Pointer (NAPTR) Used to store rules used by Dynamic Delegation Discovery System (DDDS) applications

BOOTstrap Protocol (BOOTP)
A TCP/IP application-layer protocol that enables diskless workstations to determine IP addresses and parametres BOOTP can return information such as IP addresses, subnet masks, default gateway addresses and name server addresses BOOTP is a client/server program

Dynamic Host Configuration Protocol (DHCP)
A protocol that assigns IP addresses automatically on a TCP/IP network Along with an IP address, DHCP can specify: Subnet mask Default gateway DNS server WINS server IP addresses can be reserved by mapping an IP address in the DHCP pool to a client’s MAC address

Internet Protocol Version 6 (IPv6) Addressing Essentials
IPv4 vs. IPv6 addresses Different length IPv4 – 32 bits divided into four 8-bit integers IPv6 – 128 bits divided into eight 16-bit integers Different notation IPv4 – dotted decimal IPv6 – colon notation Different number system IPv4 – decimal IPv6 – hexadecimal

IPv6 Address Types IPv6 supports three types of addresses:
Unicast – a point-to-point address that is assigned to a single entity Multicast – a single IP address assigned to a group; multicasting is a one-to-many communication Anycast – similar to multicast; when communicating to an anycast address, the closest member of the anycast group is found, and the message is sent only to that member of the group

Summary Identify common ports and services
Define common internal and external routing protocols, and distinguish between internal and external routing protocol functions Explain dynamic, static and default routes, and describe the function of routing tables Compare and contrast connection-oriented and connectionless transport Define and identify well-known, registered and random/dynamic ports Compare and contrast the IPv4 and IPv6 address formats Determine the network address/number when given a host address and subnet mask Identify network, host and broadcast addresses Define unicasting, broadcasting, multicasting and anycasting

Summary (cont'd) Explain private network addressing
Identify the importance of the subnet mask Identify the subnet mask by bit count and by dotted decimal notation, and define Classless Interdomain Routing (CIDR) Determine the number of host addresses in a subnet Describe the impact of proxies on convergent network communications Explain Network Address Translation (NAT) Identify Domain Name System (DNS) features and functions Explain functions and benefits of automatic addressing including protocol steps, and troubleshooting handsets, PCs and all IP-enabled devices Determine which Internet Protocol (IP) version to implement (e.g., IPv4 vs. IPv6)

Lesson 5: QoS, VLANs and Troubleshooting

Objectives Describe the need for Quality of Service (QoS) in converged networks, including identifying problems that occur without QoS Summarize the importance of QoS to real-time solutions Compare and contrast QoS with Class of Service (CoS) Compare and contrast best-effort delivery and QoS with traffic shaping Identify QoS technologies, describe network neutrality issues, and identify proprietary and open-source solutions Describe the Type of Service (TOS) field in an IP packet Explain the roles of 802.1p, 802.1q and 802.1d when providing QoS, including implementation of traffic shaping using VLANs or protocols

Objectives (cont'd) Describe QoS on wireless networks (802.11e), including Wireless Multimedia Extensions (WME) / WiFi Multimedia (WMM) Describe fundamental VLAN functions, features and concepts Identify benefits of using a VLAN Identify typical problems that occur without a VLAN List common troubleshooting steps Use the Internet Control Message Protocol (ICMP) to determine connectivity Identify common configuration errors in IP devices Explain the effects of Network Address Translation (NAT) and Port Address Translation (PAT) on convergence solutions such as Session Initiation Protocol (SIP), including workarounds and solutions

Quality of Service (QoS)
Quality of Service (QoS) – a defined system for measuring and improving end-to-end performance in communications networks Three levels of QoS: Best-effort service – provides no guarantees of delivery, speed or order of delivery Differentiated service (Class of Service) – marks some traffic to indicate that it should be treated with priority over the rest of the traffic Guaranteed service – confirms an absolute reservation of network resources for specific traffic

Class of Service (COS) Class of Service (CoS) – A set of QoS technologies and software mechanisms that determine packet priority in IP networks on a hop-by-hop basis Three basic CoS technologies: 802.1p Layer 2 tagging IP Precedence (use of the Type of Service [TOS] field in an IP packet header) Differentiated Services (DiffServ)

Traffic Shaping Traffic shaping – the process of controlling the volume and rate of traffic sent in to a network Traffic-shaping mechanisms include: Buffers – incoming traffic is buffered to help with flow control Queues – outgoing traffic is separated into distinct data flows and then directed to the appropriate queues on a forwarding device Traffic-shaping algorithms – control the amount of data injected into the network

Problems that Occur Without QoS
Problems encountered in best-effort delivery networks: Delay – packets are held up in a queue or arrive later because they took different routes Jitter – quality problems caused by different delays Dropped packets – packets may be dropped when a router's buffer is full Corrupted packets – packets may be corrupted during transmission Disordered packet delivery – packets may arrive out of sequence

QoS Technologies QoS standards and protocols:
Differentiated Services (DiffServ) Integrated Services (IntServ) Multiprotocol Label Switching (MPLS) 802.1p and 802.1q

Differentiated Services (DiffServ)
DiffServ – differentiates data packets into classes to ensure preferential treatment for higher-priority traffic Type of Service (TOS) field – stipulates the level of service that the data requires TOS elements: Precedence bits Delay bit Throughput bit Reliability bit Cost bit Bit 7

DiffServ Priority Levels
Using the three Precedence bits of the TOS field (0, 1 and 2), a network administrator could assign priority levels from 0 (default) to 7 (highest) to classify and prioritize types of traffic at Layer 3, as shown: Priority Level Precedence Bits Traffic Type 000 Routine 1 001 Priority 2 010 Immediate 3 011 Flash 4 100 Flash Override 5 101 Critical 6 110 Internetwork Control 7 111 Network Control

Integrated Services (IntServ)
IntServ – an architecture that uses RSVP to reserve the total bandwidth along the entire network path before data transmission takes place Resource Reservation Protocol (RSVP) – an IETF standard that allows an application to request the QoS it needs by sending end-to-end control messages along the data's path IntServ and RSVP operate by reserving capacity in the network, based on the needs of a session, before the session is set up

Multiprotocol Label Switching (MPLS)
MPLS – a QoS technology that allows routers and switches to instantly recognise a packet and pass it along a set of predetermined paths MPLS integrates Layer 2 information about network links into Layer 3 within a particular system Label Edge Router (LER) – a 32-bit header added to a packet when the packet enters an MPLS network The MPLS LERs enable the MPLS network to route once and switch thereafter The major advantage to MPLS is speed

IEEE 802.1p, 802.1q and 802.1d IEEE 802.1p – prioritizes network traffic at the MAC sublayer of the OSI data link layer (Layer 2) IEEE 802.1q – defines the creation of VLAN tags, which are used by the 802.1p standard to prioritize network traffic IEEE 802.1d (Spanning Tree Protocol [STP]): Builds a loop-free network when redundant paths are present Activates standby links when a primary path becomes unavailable

QoS on Wireless Networks
On wireless LANS based on the standard: All users share the network bandwidth No one packet gets priority over any other uses two coordination functions: Distributed Coordination Function (DCF) Point Coordination Function (PCF) Neither DCF nor PCF differentiate between traffic types or sources

IEEE e IEEE e – defines QoS mechanisms for wireless networks Enhances DCF and PCF through the Hybrid Coordination Function (HCF), which has two methods of channel access: Enhanced DCF Channel Access (EDCA) – high-priority traffic has a higher chance of being sent than low-priority traffic HCF Controlled Channel Access (HCCA) – enables applications such as VoIP and streaming video to function more effectively on WiFi networks

WiFi Multimedia (WMM) WMM – prioritizes wireless network traffic and provides basic QoS services A subset of the e standard Categorizes and prioritizes traffic Does not provide guaranteed throughput Four access categories: Voice (highest priority) Video Best effort Background (lowest priority) Also known as Wireless Multimedia Extensions (WME)

Virtual LANs (VLANs) Virtual local area networks (VLANs):
Are a group of nodes in the same broadcast domain Are created with software instead of hardware Are implemented on switches Eliminate collision domains Operate on the data link layer (Layer 2) of the OSI/RM Function without depending on the physical topology of the LAN

802.1q Frames 802.1q – defines the process by which frames can be tagged as belonging to a specific VLAN Standard Ethernet frame: 802.1q frame:

Tag Control Information (TCI) Field
Includes the following three components: A 3-bit user_priority field A 1-bit canonical format identifier (CFI) A 12-bit VLAN ID field (VID)

802.1p Header Includes a 3-bit priority field that allows frames to be grouped into eight traffic classes: Priority Level Traffic Type Examples 1 Background The lowest priority 2 Undefined Best Effort Typical network traffic 3 Excellent Load Business-critical 4 Controlled Load Streaming multimedia 5 Video Video-conferencing 6 Voice IP telephony 7 Network Control Reserved Network-management traffic

Assigning VLAN Membership
Port group-based VLANs – membership based on manual configuration of ports on a switch MAC-based VLANs – membership based on MAC address of device connected to a given switch port Layer 3-based VLANs – membership based on Layer 3 information (protocol type or network layer address) Authentication-based VLANs – membership based on authentication credentials of user or device using 802.1x protocol

VLAN Benefits Benefits of VLANs:
Vital to the successful function of time-sensitive applications The ability to prioritize and smooth traffic allows network devices to perform load balancing Makes network management a little easier Allows for protocol management on the network Convergence without VLANs: Convergence applications may not get the bandwidth and network access they require Time-sensitive applications suffer from extended delays, causing jitter

Troubleshooting Overview
Successful troubleshooting steps can be categorized into four areas: Analyzing the scope of the problem Applying troubleshooting methods Using troubleshooting indicators Using troubleshooting tools

Analyzing the Scope of the Problem
Knowing a problem's scope helps you determine its severity Consider the following questions: How many machines or network segments are affected? How frequently does the problem occur? Can the problem be duplicated?

Applying Troubleshooting Methods
Use the DETECT acronym to remember appropriate troubleshooting methods: D – Discover the problem E – Evaluate the scope of the problem T – Track approaches to solving the problem E – Execute an approach C – Check for problem resolution T – Transfer knowledge

Using Troubleshooting Indicators
Network operating systems include error-logging and reporting utilities: Windows systems – Application log, Security log and System log Windows Event Viewer utility Linux operating systems log errors in the /var/log/messages file Mac OS X and BSD systems log errors in the /var/system.log file Indicator lights – point out reliable connections, errors and activity

Using Troubleshooting Tools
Common troubleshooting tools include: Crossover cables – can eliminate hubs and switches as potential causes of connectivity problems Hardware loopback devices – can determine whether the device can communicate with itself, indicating that the TCP stack is functioning correctly on the device Tone generators and tone locators (fox and hound) – can identify network cabling

Overview of TCP/IP Troubleshooting Tools
Every administrator of a TCP/IP network should be familiar with the following two network files: The services file – contains port numbers for well-known services The protocol(s) file – identifies the Internet protocols used on a network

Internet Control Message Protocol (ICMP)
ICMP – a protocol that relays messages when a host is unavailable Known as the troubleshooting protocol of TCP/IP A required part of the TCP/IP stack Allows Internet hosts and gateways to report errors: Source-quench error messages – generated when packets arrive too quickly for a host or gateway to process Echo-request and echo-reply query messages – used by the ping command to test reachability results

General Network Troubleshooting Commands
Use the following commands to assist with general network troubleshooting: ping tracert / traceroute netstat telnet

The ping Command Tests connectivity between source and destination systems Syntax: ping ip_address Includes several options:

ping Output

The tracert Command Used to determine the path between the source and destination systems Provides information on round-trip propagation time between each router and the source system You can use tracert to locate failures far from your local network Note: UNIX uses traceroute

tracert Output

The netstat Command Displays information about packets processed by your system on the network Shows the state of sockets If executed without specifying options, the netstat command displays established active connections:

The telnet Command Allows users to log on to a remote computer, provided that permission has been granted Ideal for troubleshooting because you can log on to a system from wherever you are and work as if you were sitting in front of it

Name and Address Commands
The following commands are helpful when troubleshooting name resolution problems: ipconfig / ifconfig arp

The ipconfig and ifconfig Commands
The ipconfig command is used to display IP configurations in Windows Syntax: ipconfig options Options include: /all – shows all IP-related configuration information /release – releases IP addresses obtained from a DHCP server /renew – renews IP addresses obtained from a DHCP server The ifconfig command is used to display IP configuration settings in UNIX-based systems, including Linux; has much of the same functionality as the Windows ipconfig command

ipconfig Output

The arp Command Displays and modifies the Internet-to-MAC-address translation tables used by the Address Resolution Protocol (ARP) ARP resolves software (IP) addresses into hardware (MAC) addresses

Network Analyzers Used for:
Monitoring network traffic to identify network trends Identifying network problems and sending alert messages Identifying specific problems Testing network connections, devices and cables Also known as protocol analyzers

Troubleshooting Considerations
DNS name resolution Is the address for the DNS server correct? Hosts file configuration Is the lmhosts file accurate? Static vs. dynamic IP addressing Are two nodes attempting to use the same IP address? Default gateway and subnet mask Is the default gateway specified correctly? Is the proper subnet mask specified?

Common Configuration Errors in IP Devices
Firmware updates – can provide additional features and functionality for various types of devices Proxy settings – you must configure both the server and your IP devices to work together Communication mode – When an IP device operates in half-duplex, other devices will fall back to half-duplex when communicating with that device

NAT and PAT Issues NAT and PAT can pose problems for VoIP communications that use SIP If you need to implement SIP in a network where NAT and PAT are used, consider the following workarounds: Simple Traversal of UDP through Network Address Translators (STUN) Traversal Using Relay NAT (TURN) Universal Plug and Play (UPnP) Application Layer Gateway (ALG)

Summary Describe the need for Quality of Service (QoS) in converged networks, including identifying problems that occur without QoS Summarize the importance of QoS to real-time solutions Compare and contrast QoS with Class of Service (CoS) Compare and contrast best-effort delivery and QoS with traffic shaping Identify QoS technologies, describe network neutrality issues, and identify proprietary and open-source solutions Describe the Type of Service (TOS) field in an IP packet Explain the roles of 802.1p, 802.1q and 802.1d when providing QoS, including implementation of traffic shaping using VLANs or protocols

Summary (cont'd) Describe QoS on wireless networks (802.11e), including Wireless Multimedia Extensions (WME) / WiFi Multimedia (WMM) Describe fundamental VLAN functions, features and concepts Identify benefits of using a VLAN Identify typical problems that occur without a VLAN List common troubleshooting steps Use the Internet Control Message Protocol (ICMP) to determine connectivity Identify common configuration errors in IP devices Explain the effects of Network Address Translation (NAT) and Port Address Translation (PAT) on convergence solutions such as Session Initiation Protocol (SIP), including workarounds and solutions

Data Networking Introduction to Data Networking
Transmission, Communication and Wiring LANs and WANs TCP/IP Suite and Internet Addressing QoS, VLANs and Troubleshooting

Data Networking.

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