DataNetworking

Lesson 1:Introduction to

Data Networking

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

Data Networking

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 Networking

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

Data Networking

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

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Network Topologies

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Star Topology

Switch

Server

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Star Bus Hybrid Topology

Switch Backbone

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Partial Mesh Topology

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Full Mesh Topology

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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

Data Networking

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

Data Networking

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)

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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)

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OSI Reference Model

Layer Layer NumberApplication 7Presentation 6Session 5Transport 4Network 3Data link 2Physical 1

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Network Communication

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OSI Protocol Examples

Application-layer protocolsSIP, H.323, MGCP, SMTP, POP3, HTTP, DNS, BOOTP, FTP, Telnet, LDAP

Presentation-layer protocolsASN.1, Codecs

Session-layer protocolsRTCP, NetBIOS, SQL, ASP

Transport-layer protocolsRTP, TCP, UDP, ATP

Network-layer protocolsIP, ICMP, ARP, DDP

Data link-layer protocols802.2, 802.3, 802.11

Physical layer Network hardware or technologies

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Packet Creation – Adding Headers

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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

Data Networking

Packets

Packet structure:– Header– Data– Trailer

Trailer

Data

Header

Data Networking

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

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TCP/IP Model vs. OSI Model

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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

Data Networking

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

Data Networking

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

Data Networking

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

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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

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DSH and T-Carrier Equivalents

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T-Carrier vs. E-Carrier Speeds

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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

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Synchronous Optical Network (SONET)

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Synchronous Digital Hierarchy (SDH)

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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

T1Line

E3Line

DS4Line

SDHLineMultiplexer

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Common Peripheral Ports

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

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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

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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

Data Networking

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

Data Networking

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

Data Networking

PS/2 connectors

• Used to connect a keyboard or a mouse to a computer

• 6-pin circular connector• Used on all laptops and PCs

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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)

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Amphenol Connectors

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

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Transmission Media

Free space transmission media:– Infrared– Short-range wireless– Microwave– Satellite

Cable transmission media:– Twisted-pair cable– Coaxial cable– Fiber-optic cable

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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

Data Networking

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

Data Networking

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

Data Networking

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

Data Networking

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:

Data Networking

Common Coax Cable Types

Type 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)

Data Networking

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

Data Networking

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

Data Networking

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

Data Networking

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

Data Networking

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

Data Networking

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

Data Networking

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), 802.11i/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

Data Networking

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

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Common Network Components

• Network interface card (NIC)

• Repeaters • Hubs • Bridges • Routers

• Switches • Gateways • Network termination

equipment (NTE) • Firewalls• Modems

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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

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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

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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

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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

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Hubs

• Connect multiple devices into the same collision domain

• Operate at the physical layer (Layer 1) of the OSI/RM

Hub

Hub

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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

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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

Router

Network1

Network2

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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

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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

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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

Data Networking

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)

Data Networking

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

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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

CSU/DSU Router Network

TelecomNetwork

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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

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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

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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 802.2 – Logical Link Control (LLC)

function– IEEE 802.3 – Ethernet – IEEE 802.3u – Fast Ethernet– IEEE 802.3z and 802.3ab – Gigabit Ethernet– IEEE 802.3ae (supplement) – 10-Gigabit

Ethernet

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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)

Data Networking

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

Data Networking

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)

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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

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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

Data Networking

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

Data Networking

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

Data Networking

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

Data Networking

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

Data Networking

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

Data Networking

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

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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

Data Networking

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)

Data Networking

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)

Data Networking

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)

Data Networking

Services Provided by Encryption

Service 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

Data Networking

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

Data Networking

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

Data Networking

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)

Data Networking

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

Data Networking

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

Data Networking

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

Data Networking

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

Data Networking

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

Data Networking

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

Data Networking

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

Data Networking

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

Data Networking

WiFi and Dual Cell Phones

• WiFi (Wireless Fidelity) – generically refers to any type of 802.11 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

Data Networking

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

Data Networking

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)

Ethernet SwitchWireless node

Wireless node

Wireless node

Wireless node

Ad hocMode

Wireless node

Wireless node

Access Point

InfrastructureMode

Data Networking

Wireless Ethernet Equipment

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

Data Networking

IEEE 802.11 Wireless Standards

• 802.11 (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

Data Networking

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

Data Networking

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 802.11x wireless networks

• Remote Authentication Dial-In User Service (RADIUS) – a popular method for centralizing remote user access

Data Networking

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

Data Networking

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

Data Networking

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

Data Networking

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

Data Networking

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), 802.11i/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

Data Networking

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

Data Networking

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)

Data Networking

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

Data Networking

TCP/IP Architecture

Data Networking

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

Data Networking

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

Data Networking

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

Data Networking

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

Data Networking

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

Data Networking

Internal vs. ExternalRouting 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)

Data Networking

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)

Data Networking

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)

Data Networking

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 Networking

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

Data Networking

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)

Data Networking

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

Data Networking

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

Data Networking

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 01111001, you can determine the decimal value by adding the corresponding bit values that equal 1

01111001 = 0 + 64 + 32 +16 +8 +0 +0 +1 =121

Bit Value 128 64 32 16 8 4 2 1

Data Networking

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

Data Networking

Internet Address Classes Class A: Range 0.0.0.0 to 127.255.255.255

Class B: Range 128.0.0.0 to 191.255.255.255

Class C: Range 192.0.0.0 to 223.255.255.255

Class D: Range 224.0.0.0 to 239.255.255.255

Class E: Range 240.0.0.0 to 247.255.255.255

0 Host (3 bytes)

Host (2 bytes)

Host (1 byte)

126 Networks

16,384 Networks

2,097,152 Networks

16,777,214 Hosts

65,534 Hosts

254 Hosts

Network (1 byte)

Network (2 bytes)

Network (3 bytes)

Multicasting—network (4 bytes)

Experimental/reserved for future use

01

11 0

11 01

11 11 0

StartingBinaryValue

StartingBinaryValue

StartingBinaryValue

StartingBinaryValue

StartingBinaryValue

Data Networking

Internet Address Classes (cont'd)

• Class A – range 0.0.0.0 to 127.255.255.255 • Class B – range 128.0.0.0 to 191.255.255.255 • Class C – range 192.0.0.0 to 223.255.255.255 • Class D – range 224 to 239 (network address

only)• Class E – range 240 to 247 (network address

only – reserved for future use)

Data Networking

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

– 0.0.0.0 – 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

Data Networking

Private IP Addressing

• Private network addresses are not Internet-addressable

Class Private IP Address Range Subnet Mask

Class A 10.0.0.0 to 10.255.255.255 255.0.0.0

Class B 172.16.0.0 to 172.31.255.255 255.240.0.0

Class C 192.168.0.0 to 192.168.255.255 255.255.0.0

Data Networking

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

Data Networking

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

Data Networking

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

Data Networking

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

Data Networking

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

Data Networking

IP-Enabled Device Configuration Parametres

Basic configurations:– IP address– Subnet mask– Default gateway– DHCP client– DNS server

Data Networking

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

Data Networking

IP-Enabled Device Configuration Parametres (cont'd)

Name resolution configurations:– Host name– Domain name– DNS server– NetBIOS name– WINS server

Data Networking

Domain Name System (DNS)

• DNS translates IP addresses into easily recognizable names

• Domain name syntax:

Data Networking

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

Data Networking

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

Data Networking

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

Data Networking

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 e-mail 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

Data Networking

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

Data Networking

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

Data Networking

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

Data Networking

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

Data Networking

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

Data Networking

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

Data Networking

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

Data Networking

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

Data Networking

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

Data Networking

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)

Data Networking

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

Data Networking

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

Data Networking

QoS Technologies

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

Data Networking

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

Data Networking

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

0 000 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

Data Networking

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

Data Networking

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

Data Networking

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

Data Networking

QoS on Wireless Networks

• On wireless LANS based on the 802.11 standard:– All users share the network bandwidth– No one packet gets priority over any other

• 802.11 uses two coordination functions:– Distributed Coordination Function (DCF)– Point Coordination Function (PCF)

• Neither DCF nor PCF differentiate between traffic types or sources

Data Networking

IEEE 802.11e

• IEEE 802.11e – 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

Data Networking

WiFi Multimedia (WMM)

• WMM – prioritizes wireless network traffic and provides basic QoS services

• A subset of the 802.11e 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)

Data Networking

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

Data Networking

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:

Data Networking

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)

Data Networking

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 Undefined

0 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

Data Networking

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

Data Networking

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

Data Networking

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

Data Networking

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?

Data Networking

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

Data Networking

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

Data Networking

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

Data Networking

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

Data Networking

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

Data Networking

General Network Troubleshooting Commands

Use the following commands to assist with general network troubleshooting:

– ping– tracert / traceroute– netstat– telnet

Data Networking

The ping Command

• Tests connectivity between source and destination systems

• Syntax: ping ip_address• Includes several options:

Data Networking

ping Output

Data Networking

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

Data Networking

tracert Output

Data Networking

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:

Data Networking

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

Data Networking

Name and Address Commands

The following commands are helpful when troubleshooting name resolution problems:

– ipconfig / ifconfig – arp

Data Networking

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

Data Networking

ipconfig Output

Data Networking

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

Data Networking

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

Data Networking

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?

Data Networking

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

Data Networking

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)

Data Networking

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

Data Networking

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

Data Networking

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