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Data
Networking
Lesson 1:
Introduction to
Data Networking
Objectives
• Define common network topologies and identify structured
cable distribution schemes
• Identify the major industry bodies and standards, and obtain
and read standards documents
• Identify the layers of the Open Systems Interconnection
reference model (OSI/RM), and describe the function of
each layer
• Relate networking and convergence protocols, services and
equipment to each OSI/RM layer
• Explain data encapsulation in relation to frame assembly
and function on the network
• Relate common networking and convergence protocols,
services and equipment to each of the four layers of the
TCP/IP model
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
Data Networking
Star Bus Hybrid Topology
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
Application
Presentation
Session
Transport
Network
Data link
Physical
Layer Number
7
6
5
4
3
2
1
Data Networking
Network Communication
Data Networking
OSI Protocol Examples
Application-layer
Transport-layer protocols
protocols
RTP, TCP, UDP, ATP
SIP, H.323, MGCP,
Network-layer protocols
SMTP, POP3, HTTP,
IP, ICMP, ARP, DDP
DNS, BOOTP, FTP,
Data link-layer protocols
Telnet, LDAP
802.2, 802.3, 802.11
Presentation-layer
Physical layer
protocols
Network hardware or
ASN.1, Codecs
technologies
Session-layer protocols
RTCP, NetBIOS, SQL, ASP
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
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 transportlayer 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 higherlayer 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
Data Networking
Lesson 2:
Transmission, Communication
and Wiring
Objectives
• Compare and contrast the use of E-carrier,
T-carrier, SONET/SDH and ISDN technologies for
data and voice networks, including bandwidths of
common technologies
• Identify cable terminators
• Define and contrast data communications
equipment (DCE) and data terminating
equipment (DTE)
• Identify network media, and identify proper
cabling procedures in specific environments
• Compare and contrast straight-through,
crossover, rolled and null-modem cabling
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
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 crosslinked
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
Data Networking
Lesson 3:
LANs and WANs
Objectives
• Relate networking and convergence protocols,
services and equipment to each OSI/RM layer
• Identify the functions of routers, switches, firewalls,
core and edge networks, modems and hubs in
relation to data networking hardware
• Explain the format and function of Media Access
Control (MAC) addresses
• Define the Spanning Tree Protocol (STP)
• Define networking methods, standards and
protocols, and their characteristics
• Explain the concept of protocol tunneling, and
identify elements and benefits of using a Virtual
Private Network (VPN) in a convergent network
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
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
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
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
PVCs
Corporation
Ports
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 DialIn 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)
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
Data Networking
Lesson 4:
TCP/IP Suite and
Internet Addressing
Objectives
• Identify common ports and services
• Define common internal and external routing protocols, and
distinguish between internal and external routing protocol
functions
• Explain dynamic, static and default routes, and describe the
function of routing tables
• Compare and contrast connection-oriented and
connectionless transport
• Define and identify well-known, registered and
random/dynamic ports
• Compare and contrast the IPv4 and IPv6 address formats
• Determine the network address/number when given a host
address and subnet mask
• Identify network, host and broadcast addresses
• Define unicasting, broadcasting, multicasting and
anycasting
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. External
Routing Protocols
• Internal routing protocols – used within an
organisation’s network
– Routing Information Protocol (RIP)
– Open Shortest Path First (OSPF)
• External routing protocols – used outside an
organisation’s network
– Exterior Gateway Protocol (EGP)
– Border Gateway Protocol (BGP)
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
Bit
Value
128
64
32
16
8
4
2
1
• 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
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
Starting
Binary
Value
0 Network (1 byte)
Host (3 bytes)
126 Networks
16,777,214 Hosts
Class B: Range 128.0.0.0 to 191.255.255.255
Starting
Binary
Value
1 0
Network (2 bytes)
16,384 Networks
Host (2 bytes)
65,534 Hosts
Class C: Range 192.0.0.0 to 223.255.255.255
Starting
Binary
Value
1 1 0
Network (3 bytes)
Host (1 byte)
2,097,152 Networks
254 Hosts
Class D: Range 224.0.0.0 to 239.255.255.255
Starting
Binary
Value
1 1 1 0
Multicasting—network (4 bytes)
Class E: Range 240.0.0.0 to 247.255.255.255
Starting
Binary
Value
1 1 1 1 0
Experimental/reserved for future use
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-toone 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
.(root)
ie
se
com
mx
net
ch
xyz
user1
iso
ftp
user2
www
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 email 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)
Data Networking
Lesson 5:
QoS, VLANs
and Troubleshooting
Objectives
• Describe the need for Quality of Service (QoS) in converged
networks, including identifying problems that occur without
QoS
• Summarize the importance of QoS to real-time solutions
• Compare and contrast QoS with Class of Service (CoS)
• Compare and contrast best-effort delivery and QoS with
traffic shaping
• Identify QoS technologies, describe network neutrality issues,
and identify proprietary and open-source solutions
• Describe the Type of Service (TOS) field in an IP packet
• Explain the roles of 802.1p, 802.1q and 802.1d when
providing QoS, including implementation of traffic shaping
using VLANs or protocols
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) – highpriority 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
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Introduction to Data Networking
Transmission, Communication and Wiring
LANs and WANs
TCP/IP Suite and Internet Addressing
QoS, VLANs and Troubleshooting
Data Networking