Data Networking. Lesson 1: Introduction to Data Networking.
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Transcript of Data Networking. Lesson 1: Introduction to Data Networking.
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
Data Networking
Network Topologies
Data Networking
Star Topology
Switch
Server
Data Networking
Star Bus Hybrid Topology
Switch Backbone
Data Networking
Partial Mesh Topology
Data Networking
Full Mesh Topology
Data Networking
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)
Data Networking
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)
Data Networking
OSI Reference Model
Layer Layer NumberApplication 7Presentation 6Session 5Transport 4Network 3Data link 2Physical 1
Data Networking
Network Communication
Data Networking
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
Data Networking
Packet Creation – Adding Headers
Data Networking
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
Data Networking
TCP/IP Model vs. OSI Model
Data Networking
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
Data Networking
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
Data Networking
DSH and T-Carrier Equivalents
Data Networking
T-Carrier vs. E-Carrier Speeds
Data Networking
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
Data Networking
Synchronous Optical Network (SONET)
Data Networking
Synchronous Digital Hierarchy (SDH)
Data Networking
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
Data Networking
Common Peripheral Ports
• Serial ports• Universal Serial Bus (USB)• FireWire (IEEE 1394)• Parallel ports• PS/2 connectors• Small computer system interface (SCSI)• Amphenol connectors
Data Networking
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
Data Networking
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
Data Networking
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)
Data Networking
Amphenol Connectors
Often used in patch cables for connecting 66 and 110 punchdown blocks
Data Networking
Transmission Media
Free space transmission media:– Infrared– Short-range wireless– Microwave– Satellite
Cable transmission media:– Twisted-pair cable– Coaxial cable– Fiber-optic cable
Data Networking
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
Data Networking
Common Network Components
• Network interface card (NIC)
• Repeaters • Hubs • Bridges • Routers
• Switches • Gateways • Network termination
equipment (NTE) • Firewalls• Modems
Data Networking
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
Data Networking
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
Data Networking
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
Data Networking
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
Data Networking
Hubs
• Connect multiple devices into the same collision domain
• Operate at the physical layer (Layer 1) of the OSI/RM
Hub
Hub
Data Networking
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
Data Networking
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
Data Networking
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
Data Networking
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
Data Networking
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
Data Networking
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
Data Networking
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
Data Networking
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
Data Networking
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
Data Networking
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)
Data Networking
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
Data Networking
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
Data Networking
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