Download 01 Fundamentals of Networking

Fundamentals of Networking
(Topic 1)
Textbook:
Networking Basics, CCNA 1 Companion Guide, Cisco Press
Cisco Networking Academy Program, CCNA 1 and 2,
Companion Guide, Cisco Press, Latest Edition
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Common Networking Icons
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Networks
• “A network is a set of devices (nodes)
connected by media links. A node can be a
computer, printer, or any other device
capable of sending and/or receiving data
generated by other nodes on the network.
The links connecting the devices are often
called communication channels.”
• E.g. two PCs connected with a cable, the
Internet
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Requirements for Internet
Connection
• Physical connection
– Network Interface Card (NIC)
– Cable? Wireless
• Logical connection
– A logical connection uses standards call protocols
– A protocol is a set of rules and conventions that
govern how devices on a network communicate
– Transmission Control Protocol / Internet Protocol
(TCP/IP) is a key protocol used in the Internet
• Applications
– E.g. Web Browsers
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PC Basics
• Transistor, Integrated circuit (IC), Resistor, Capacitor,
CPU, memory etc.
• Motherboard, Power Supply, Hard disk, CDROM, Video
Card, Sound Card, etc.
• Serial Port, USB Port, Parallel Port
• Modem
– A modem is an electronic device that is used for data
communications through telephone lines
• Network Interface Card (NIC)
– An expansion board that provides a network communication
connection to and from a PC.
– Build in circuit
– 10 Mbps, 100 Mbps, 1000 Mbps
– Media Access Control (MAC) address
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Binary Representation of Data
• Computers can only understand and use data
that is in binary (two-state, on/off, 0/1) format
• Each binary digit is called a bit
• Each grouping of eight bits is called a byte
• Kilo (1024), Mega (1024*1024), Giga, Tera
• American Standard Code for Information
Interchange (ASCII) is the most commonly used
code for representing alphanumeric data in a
computer. E.g. 65 is A, 66 is B
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Base 10 Number System
• Symbols: 0,1,2,3,4,5,6,7,8,9
Base
Exponent
103
102
101
100
Place
Value
e.g. 2134
1000
100
10
1
2*103
1*102
3*101
4*100
• 2134 (decimal) = 2*103 + 1*102 + 3*101 + 4*100
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Base 2 Number System
• Symbols: 0,1
Base
Exp
27
26
25
24
23
22
21
20
Place
Value
128 64
32
16
8
4
2
1
e.g.
10110
0
0
1
0
1
1
0
0
• 10110 (binary) = 1*24 + 1*22 + 1*21 = 22 (decimal)
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Base 16 Number System
• Symbols: 0,1,2,3,4,5,6,7,8,9,A,B,C,D,E,F
Base
Exponent
163
162
161
160
Place
Value
e.g. 0A08
4096
256
16
1
0*163
10*162
0*161
8*160
• 0A08 (hex) = 0*163 + 10*162 + 0*161 + 8*160
= 2568 (decimal)
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Converting Decimal Numbers to
Binary Numbers
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Converting Binary Numbers to
Decimal Numbers
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Converting Decimal to
Hexadecimal
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Converting Hexadecimal to
Decimal
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Converting Binary to Hexadecimal
• Binary -> Decimal -> Hexadecimal
• Short Cut: 4 bits -> 1 Hexadecimal digit
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Basic Logic Operations
0
0
1
1
0
1
0
1
0
1
AND
0
0
0
1
OR
0
1
1
1
XOR
0
1
1
0
NOT
1
0
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Types of Networks
• Local Area Network (LAN)
– LAN is usually privately owned and links the devices
in a single office, building, or campus
– Designed to allow resources to be shared
• Metropolitan Area Network (MAN)
– Designed to extend over an entire city
– May involve service provided by public companies,
e.g. local telephone company
• Wide Area Network (WAN)
– Provides long-distance transmission of data over
large geographical areas
• Virtual Private Network (VPN), Intranet etc.
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Local Area Network (LAN)
• Designed to
–
–
–
–
Operate within a limited geographic area
Allow many users to access high-bandwidth media
Provide full-time connectivity to local services
Connect physically adjacent devices
• Some common LAN technologies
– Ethernet
– Token Ring
– FDDI
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Wide Area Network (WAN)
• Designed to
– Operate over large, geographically separated areas
– Allow users to engage in real-time communication
with other users
– Provide full-time remote resources connected to local
services
– Provide e-mail, WWW, file transfer, e-commerce
services
• Some common WAN technologies
– Modems, ISDN,
– DSL, Frame Relay
– T1 or E1 leased lines
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Virtual Private Network (VPN)
• A VPN is a private network that is
constructed within a public network
infrastructure (e.g. Internet)
• Provides a secure tunnel
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Bandwidth
• The amount of information that can flow through
a network connection in a given period of time.
• Analogy: the width of a pipe, the number of
lanes on a highway
• Measurement: bps
• Why important
– Bandwidth is finite
– Bandwidth is not free
– Bandwidth is a key factor in analyzing network
performance and designing new networks
– Demand for bandwidth is ever-increasing
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Throughput
• Bandwidth of a LAN is usually 100Mbps,
can you transfer file at that rate?
• Throughput refers to actual measured
bandwidth
• Factors
– Client, Server, Other users, Routing, Topology,
Type of data, Time of day……
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Network Protocols (1)
• Protocol suites are collections of protocols that
enable network communication from one host
through the network to another host
• A protocol is a formal description of a set of rules
and conventions that govern a particular aspect
of how devices on a network communicate. It
determines the format, timing, sequencing, and
error control
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Network Protocols (2)
• Protocols are created and maintained by many
Standards organizations and committees
–
–
–
–
–
–
Institute of Electrical and Electronic Engineers (IEEE)
American National Standards Institute (ANSI)
Telecommunications Industry Association (TIA)
Electronic Industries Alliance (EIA)
International Telecommunications Union (ITU)
International Organization of Standardization (ISO)
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Networking Models
• Conceptual Model
– helps you understand the action that occurs during
communication from one computer to another
• Network communications is a very complex process,
difficult to understand it as a whole, so break it down into
a series of layers
• Each layer is responsible for a specific part of network
communication
• Layers interact with the layer above and below them only
• Two common models
– Open System Interconnection (OSI) reference model
– TCP/IP reference model
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OSI Model (1)
• Released in 1984, by ISO
• Provides vendors with a set of standards
that ensure greater compatibility and
interoperability among various types of
network technologies
• Defines the network functions that occur at
each layer
• Acts as a framework for understanding the
network
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OSI Model (2)
• 7 layers
–
–
–
–
–
–
–
7: Application layer
6: Presentation layer
5: Session layer
4: Transport layer
3: Network layer
2: Data link layer
1: Physical layer
• Layer 5,6,7 are concerned with application
issues
• Layer 4,3,2,1 are concerned with data-transport
issues
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OSI Model (3)
• Advantages of layering
– Standardizes network components to allow
multiple-vendor development and support
– Allows different types of network hardware
and software to communicate
– Prevents changes in one layer from affecting
the other layers
– Breaks into smaller components to make
learning easier
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Layer 7: Application Layer
• Closest to the user
• Provides network services to the user’s
applications
• E.g. telnet, http
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Layer 6: Presentation Layer
• Ensures that the information that the application
layer of one system sends out can be read by
the application layer of another system
• Provides services to layer 7
• Translates (if need) among multiple data formats
by using a common format
• Encryption and Decryption
• E.g. layer 6 formats: TIFF, JPEG, MIDI, MPEG
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Layer 5: Session Layer
• Establishes, manages, and terminates
sessions between two communicating
hosts
• Synchronizes dialogue between the two
host’s presentation layers and manages
their data exchange
• Provides services to layer 6
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Layer 4: Transport Layer
• Segments data from the sending host’s system and
reassembles it into data stream on the receiving host’s
system
• Provides a data-transport service which handles issues
like
– Reliability of transport
– Establishment, maintenance, and proper termination of Virtual
circuits
• Transport error detection, recovery, Information flow
control
• Provides services to layer 5
• E.g. Transmission Control Protocol (TCP), User
Datagram Protocol (UDP), Sequenced Packet Exchange
(SPX)
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Layer 3: Network Layer
• Provides connectivity and path selection
(routing) between two host systems that
might be on separated networks
• Concerned with logical addressing
• Provides services to layer 4
• E.g. Internet Protocol (IP), Internetwork
Packet Exchange (IPX)
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Layer 2: Data Link Layer
• Provides reliable transit of data across a
physical link
• Concerned with physical address, network
topology, network access, error notification,
ordered delivery of frames, and flow
control
• Provides services to layer 3
• E.g. protocols include Ethernet, Token
Ring, ISDN, PPP, and Frame Relay
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Layer 1: Physical Layer
• Defines the electrical, mechanical,
procedural, and functional specifications
for activating, maintaining, and
deactivating the physical link between end
systems
• E.g. voltage levels, timing of signal,
physical data rates, physical connectors,
etc.
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Peer-to-Peer Communications
• Each layer of the OSI model at the source must
communicate with its peer layer at the
destination
• The protocols at each layer exchange
information, called protocol data units (PDU),
between peer layers
• Layer 4 (Segments)
• Layer 3 (Packets)
• Layer 2 (Frames)
• Layer 1 (Bits)
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Encapsulation
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De-Encapsulation
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Networking Devices (1)
• Network Interface Card (NIC)
– Each carries a unique code, Media Access Control (MAC)
address
• Repeaters
– To regenerate and retime network signals, allowing them to
travel a longer distance on the medium
– Work at Layer 1, physical layer, of the OSI reference Model
• Hubs
– To regenerate and retime signals, a common connection point
for devices in a network
– Connect segments of a LAN
– No filtering, no switching, no routing
– Work at Layer 1
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Networking Devices (2)
• Bridges
– A Layer 2 device designed to create two or more LAN
segments, each of which is a separate collision
domain
– To filter traffic on a LAN to keep local traffic local
(using MAC address) yet allow connectivity to other
segments
– More intelligent than hubs, with filtering capability
– Create more collision domains, allowing more than
one device to transmit simultaneously without causing
a collision
– Maintain MAC address tables (bridge tables)
– Broadcast: to all segments, i.e. one broadcast domain
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Networking Devices (3)
• Layer 2 Switches
– Like bridges, switches connect LAN segments, use a
table of MAC addresses to determine the on which a
frame needs to be transmitted, and reduce traffic
– Operate at much higher speeds than bridges
(performed in hardware)
– Consider each switch port is a microbridge, and gives
each host the medium’s full bandwidth
(microsegmentation)
– Broadcast: to all segments, i.e. one broadcast domain
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Switch
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Networking Devices (4)
• Routers
– Internetworking device that passes data
packets between networks based on Layer 3
addresses
– Make decisions regarding the best path for
delivery of data (based on network addresses)
• Examine incoming packets (Layer 3 data)
• Choose the best path
• Switch them to the proper outgoing port
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Networking Devices (4)
• Voice gateway
– For handling packetized voice and data traffic
• Digital Subscriber Line Access Multiplexers
(DSLAMs)
– Used at the service provider’s central office for
concentrating DSL modem connections from homes
• Cable Modem
• Wireless Access Point
• Many more
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Network Topologies (1)
• A network topology defines how computers,
printers, network devices, and other devices are
connected
• Describes the layout of the wire and devices and
the paths used by data transmissions
• Physical Topology
– Refers to the physical layout of the devices and
media
– Bus, Ring, Star, Extended Star, Hierarchical, Mesh
• Logical Topology
– Defines how the medium is accessed by the hosts
sending data
– Broadcast, TokenCIMpassing
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Network Topologies (2)
• Bus
– Connects all the devices using a single cable
– Main cable segment must end with a
terminator
– Adv?
– Disadv?
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Network Topologies (3)
• Star
– Made up of a central connection point that is a
device such as hub, switch, or router, where
all the cabling segments meet. Each host in
the network is connected to the central device
with its own cable
– Commonly used in Ethernet LANs
– Adv?
– Disadv?
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Network Topologies (4)
• Ring
– Hosts are connected in a circle
– Data frame travels around the ring, stopping at each
node. If a node wants to transmit data, it adds data
and the destination address to it. The frame then
continues around the ring until it reaches the
destination node, which takes the data out.
– Adv: no collision
– Single Ring (one direction) Vs Dual Ring (both
directions, fault tolerance)
– Usually logical in ring but physical in star
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Network Topologies (5)
• Full-Mesh and Partial-Mesh
– Full-mesh topology connects all devices to
each other for redundancy and fault tolerance
– Adv?
– Disadv?
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Network Topologies (6)
• Logical Topology
– How the hosts communicate across the medium
– Broadcast
• Data frame is broadcasted to all hosts
• No order that the stations must follow to use the network
• Collision?
– Token ring
• Control network access by passing an electronic token
sequentially to each host
• The host gets an empty token has the right to send data
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