Transcript Module 2: Networking Fundamentals

Module 2:
Networking Fundamentals
James Chen
[email protected]
2015/7/18
YuDa College of Business
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Outline
 2.1 Networking Terminology
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Analogies
Measurement
Limitations
Throughput
Data transfer calculation
Digital versus analog
Data networks
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Network history
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Networking devices
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Network topology
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Network protocols
Local-area networks (LANs)
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Wide-area networks (WANs)
 2.3 Networking Models
Metropolitan-area networks
 Using layers to analyze problems
in a flow of materials
(MANs)
 Using layers to describe data
Storage-area networks (SANs)
communication
Virtual private network (VPN)
 OSI model
Benefits of VPNs
 OSI layers
Intranets and extranets
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 2.2 Bandwidth
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Importance of bandwidth
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Peer-to-peer communications
TCP/IP model
Detailed encapsulation process
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 2.1 Networking Terminology
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Data networks
 There was no efficient way of sharing data among multiple
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microcomputers
Floppy disks
Sneakernet created multiple copies of the data
If two people modified the file and then tried to share it, what will
happen ?.
Businesses needed a solution to address the following
problems:
 How to avoid duplication of equipment and resources
 How to communicate efficiently
 How to set up and manage a network
networking technology could increase productivity while saving
money.
In the mid-1980s, each company that created network hardware
and software used its own
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Data networks (cont.)
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company standards
Network technologies were incompatible with each other
Difficult to communicate with each other
This often required the old network equipment to be removed to
implement the new equipment.
 LAN standards provided an open set of guidelines for creating
network hardware and software, the equipment from different
companies could then become compatible.
 In a LAN system, each department of the company is a kind of
electronic island.
 WANs could connect user networks over large geographic areas.
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Network history
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Network history (cont.)
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Network history (cont.)
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Networking devices
 Equipment that connects directly to a network segment is
referred to as a device.
 End-user devices : They include computers, printers,
scanners, and other devices that provide services directly to
the user.
 Network devices : They include all the devices that connect
the end-user devices together to allow them to communicate.
 End-user devices that provide users with a connection to the
network are also referred to as hosts.
 The host devices can exist without a network, but without the
network the host capabilities are greatly reduced.
 A NIC is a printed circuit board that fits into the expansion slot of
a bus on a computer motherboard, or it can be a peripheral
device. It is also called a network adapter.
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Networking devices (cont.)
 Network devices provide transport for the data that needs to be
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transferred between end-user devices.
Network devices provide extension of cable connections,
concentration of connections, conversion of data formats, and
management of data transfers.
Networking devices :
Repeater : Repeaters regenerate analog or digital signals
distorted by transmission loss due to attenuation. The purpose
of a network repeater is to regenerate and retime network
signals at the bit level. This allows them to travel a longer
distance on the media. A repeater does not perform intelligent
routing like a bridge or router.
Hubs : They concentrate connections. In other words, they take
a group of hosts and allow the network to see them as a single
unit. This is done passively, without any other effect on the data
transmission. Active hubs not only concentrate hosts, but they
also regenerate signals. Multi-ported Repeater.
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Networking devices (cont.)
 Bridges : They provide connections between LANs. Not only do
bridges connect LANs, but they also perform a check on the
data to determine whether it should cross the bridge or not. This
makes each part of the network more efficient.
 Workgroup switches : They add more intelligence to data
transfer management. Not only can they determine whether data
should remain on a LAN or not, but they can transfer the data
only to the connection that needs that data. Another difference
between a bridge and switch is that a switch does not convert
data transmission formats. Multi-ported Bridge.
 Routers : They have all the capabilities listed above. Routers
can regenerate signals, concentrate multiple connections,
convert data transmission formats, and manage data transfers.
They can also connect to a WAN, which allows them to connect
LANs that are separated by great distances. None of the other
devices can provide this type of connection.
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Networking devices (cont.)
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Networking devices (cont.)
Cisco 1503 Micro Hub
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Networking devices (cont.)
Cisco Catalyst 1924 Switch
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Networking devices (cont.)
Cisco 2621 Router
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Network topology
 Network topology defines the structure of the
network.
 Physical topology, which is the actual layout
of the wire or media.
 Logical topology, which defines how the
media is accessed by the hosts for sending
data.
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Network topology (cont.)
 Physical topologies :
 Bus topology
It uses a single backbone cable that is terminated at both
ends.
 All the hosts connect directly to this backbone.
 Ring topology
 It connects one host to the next and the last host to the first.
 This creates a physical ring of cable.
 Star topology
 It connects all cables to a central point of concentration.
 Extended star topology
 It links individual stars together by connecting the hubs
and/or switches.
 This topology can extend the scope and coverage of the
network.
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Network topology (cont.)
 Hierarchical topology
 It is similar to an extended star.
 Instead of linking the hubs and/or switches together,
the system is linked to a computer that controls the
traffic on the topology.
 Tree
 Mesh topology
 Each host has its own connections to all other hosts.
 It provides much protection as possible from
interruption of service.
 Nuclear power plant
 Although the Internet has multiple paths to any one
location, it does not adopt the full mesh topology.
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Network topology (cont.)
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Network topology (cont.)
 The logical topology of a network is how the hosts communicate across
the medium. The two most common types of logical topologies are
broadcast and token passing.
 Broadcast topology
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It simply means that each host sends its data to all other hosts on the
network medium.
There is no order that the stations must follow to use the network. It is
first come, first serve. Ethernet works this way..
 Token passing
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Token passing controls network access by passing an electronic token
sequentially to each host.
When a host receives the token, that host can send data on the
network. If the host has no data to send, it passes the token to the next
host and the process repeats itself.
Two examples of networks that use token passing are Token Ring and
Fiber Distributed Data Interface (FDDI). A variation of Token Ring and
FDDI is Arcnet. Arcnet is token passing on a bus topology.
Token Bus
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Network topology (cont.)
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Network protocols
 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.
 Protocols determine the format, timing, sequencing, and error control in
data communication. Without protocols, the computer cannot make or
rebuild the stream of incoming bits from another computer into the
original format.
 Protocols control all aspects of data communication, which include the
following:
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How the physical network is built
How computers connect to the network
How the data is formatted for transmission
How that data is sent
How to deal with errors
 IEEE, ANSI, TIA, EIA, ITU, CCITT.
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Network protocols (cont.)
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Local-area networks (LANs)
 LANs consist of the following components:
Computers
 Network interface cards
 Peripheral devices
 Networking media
 Network devices
Locally share files and printers efficiently
It makes internal communications possible. They tie data, local
communications, and computing equipment together.
Some common LAN technologies are:
 Ethernet
 Token Ring
 FDDI
Repeaters, Hubs, Bridges, Switches, Routers
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Wide-area networks (WANs)
 WANs connect user networks over a large geographical area
 It allows computers, printers, and other devices on a LAN to
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share and be shared with distant locations.
Allow access over serial interfaces operating at lower speeds
Provide full-time or part-time connectivity to local services
Provide e-mail, World Wide Web, file transfer, and e-commerce
services
Some common WAN technologies are:
 Modems
 Integrated Services Digital Network (ISDN)
 Digital Subscriber Line (DSL)
 Frame Relay
 US (T) and Europe (E) Carrier Series – T1, E1, T3, E3
 Synchronous Optical Network (SONET)
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Metropolitan-area networks (MANs)
 A MAN is a network that spans a metropolitan area
such as a city or suburban area.
 A MAN usually consists of two or more LANs in a
common geographic area.
 For example, a bank with multiple branches may
utilize a MAN. Typically, a service provider is used to
connect two or more LAN sites using private
communication lines or optical services.
 A MAN can also be created using wireless bridge
technology by beaming signals across public areas.
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Metropolitan-area networks (cont.)
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Storage-area networks (SANs)
 A SAN is a dedicated, high-performance network used to move
data between servers and storage resources.
 SAN technology allows high-speed server-to-storage, storageto-storage, or server-to-server connectivity.
 Separate network infrastructure
 SANs offer the following features:
 Performance – SANs enable concurrent access of disk or
tape arrays by two or more servers at high speeds, providing
enhanced system performance.
 Availability – SANs have disaster tolerance built in,
because data can be mirrored using a SAN up to 10
kilometers (km) or 6.2 miles away.
 Scalability – Like a LAN/WAN, it can use a variety of
technologies. This allows easy relocation of backup data,
operations, file migration, and data replication between
systems.
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Storage-area networks (cont.)
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Virtual private network (VPN)
 A VPN is a private
network that is
constructed within a
public network
infrastructure such as
the global Internet.
 A secure tunnel
between the
telecommuter’s PC
and a VPN router in
the headquarters.
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Benefits of VPNs
 A VPN is a service that offers secure, reliable connectivity over a shared
public network infrastructure such as the Internet.
 The most cost-effective method of establishing a point-to-point connection
between remote users and an enterprise customer's network. (vs. Leased
lines)
 The following are the three main types of VPNs:
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Access VPNs – Access VPNs provide remote access to a mobile worker
and small office/home office (SOHO) to the headquarters of the Intranet or
Extranet over a shared infrastructure. Access VPNs use analog, dialup,
ISDN, digital subscriber line (DSL), mobile IP, and cable technologies to
securely connect mobile users, telecommuters, and branch offices.
Intranet VPNs – Intranet VPNs link regional and remote offices to the
headquarters of the internal network over a shared infrastructure using
dedicated connections. Intranet VPNs differ from Extranet VPNs in that
they allow access only to the employees of the enterprise.
Extranet VPNs – Extranet VPNs link business partners to the
headquarters of the network over a shared infrastructure using dedicated
connections. Extranet VPNs differ from Intranet VPNs in that they allow
access to users outside the enterprise.
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Benefits of VPNs (cont.)
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Intranets and extranets
 Intranet
 Intranets are designed to permit access by users who
have access privileges to the internal LAN of the
organization.
 ex : username / password
 Extranet
 Extension of intranet.
 Applications and services that are Intranet based
 Secure access to external users or enterprises.
 ex : username / password
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Intranets and extranets (cont.)
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 2.2 Bandwidth
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Importance of bandwidth
 Why bandwidth is important :
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Bandwidth is finite
Bandwidth is not free
Bandwidth requirements are growing at a
rapid rate
Bandwidth is critical to network performance
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Importance of bandwidth (cont.)
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Bandwidth is finite
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Bandwidth is limited by the laws of physics and by the
technologies used to place information on the media.
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56 kbps modems with twisted-pair phone wires.
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Newer technologies, DSL also use the same twisted-pair
phone wires, it provides much greater bandwidth than
conventional modems.
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Optical fiber has the physical potential to provide virtually
limitless bandwidth.
Bandwidth is not free
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It is possible to buy equipment for a LAN that will provide
nearly unlimited bandwidth over a long period of time.
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For WAN connections, it is almost always necessary to buy
bandwidth from a service provider.
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A network manager needs to make the right decisions
about the kinds of equipment and services to buy.
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Importance of bandwidth (cont.)
 Bandwidth requirements are growing at a rapid rate
New network technologies and infrastructures are built to
provide greater bandwidth.
 New applications are created to take advantage of the
greater capacity.
 Streaming video and audio.
 IP telephony systems.
 The successful networking professional must anticipate the
need for increased bandwidth and act accordingly.
 Bandwidth is critical to network performance
 It is a key factor in analyzing network performance,
designing new networks, and understanding the Internet.
 Information flows as a string of bits from computer to
computer throughout the world.
 The Internet is bandwidth.
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Analogies
 Bandwidth has been defined as the amount
of information that can flow through a network
in a given time.
 There are two analogies that may make it
easier to visualize bandwidth in a network.
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Bandwidth is like the width of a pipe.
Bandwidth is like the number of lanes on a
highway.
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Analogies (cont.)
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Analogies (cont.)
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Measurement
 Bandwidth is the measure of how much information, or bits, can flow
from one place to another in a given amount of time, or seconds.
 In digital systems, the basic unit of bandwidth is bits per second (bps).
 thousands of bits per second (kbps)
 millions of bits per second (Mbps)
 billions of bits per second (Gbps)
 trillions of bits per second (Tbps)
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Measurement (cont.)
 Bandwidth vs. Speed
 They are not exactly the same thing.
 One may say, for example, that a T3 connection at
45Mbps operates at a higher speed than a T1
connection at 1.544Mbps ??
 If only a small amount of their data-carrying capacity is
being used, each of these connection types will carry
data at roughly the same speed.
 It is usually more accurate to say that a T3 connection
has greater bandwidth than a T1 connection.
 This is because the T3 connection is able to carry
more information in the same period of time, not
because it has a higher speed.
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Limitations
 Bandwidth varies depending upon the
 Type of media : twisted-pair copper wire,
coaxial cable, optical fiber, and air.
 LAN and WAN technologies used.
 The actual bandwidth is determined by the
signaling methods, network interface cards
(NICs), and other items of network equipment
that are chosen.
 The bandwidth is not determined solely by
the limitations of the medium.
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Limitations (cont.)
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Limitations (cont.)
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Throughput
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Bandwidth is the measure of the amount of information that can move through the
network in a given period of time.
Throughput refers to actual measured bandwidth, at a specific time of day, using
specific Internet routes, and while a specific set of data is transmitted on the
network.
Throughput is often far less than the maximum possible digital bandwidth of the
medium that is being used.
Throughput <= Digital Bandwidth of a medium
The factors that determine throughput
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Internetworking devices
Type of data being transferred
Network topology
Number of users on the network
Routing within the “Cloud”
Time of day
User computer
Server computer
Power conditions
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Data transfer calculation
 transfer time = size of file / bandwidth
(T=S/BW)
 The result is an estimate only
 The file size does not include any overhead
added by encapsulation.
 A more accurate estimate can be attained if
throughput is substituted for bandwidth in the
equation.
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Data transfer calculation (cont.)
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Digital versus analog
 Analog bandwidth is measured by how much of the
electromagnetic spectrum is occupied by each signal.
 The basic unit of analog bandwidth is hertz (Hz), or
cycles per second.
 The analog video signal that requires a wide
frequency range for transmission cannot be
squeezed into a smaller band. Therefore, if the
necessary analog bandwidth is not available, the
signal cannot be sent.
 In digital signaling all information is sent as bits,
regardless of the kind of information it is. Unlimited
amounts of information can be sent over the smallest
or lowest bandwidth digital channel.
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Digital versus analog (cont.)
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 2.3 Networking Models
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Using layers to analyze problems in a flow of
materials
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Using layers to describe data communication
 A data communications
protocol is a set of rules
or an agreement that
determines the format
and transmission of
data.
 It is important that all
the devices on the
network must speak the
same language or
protocol on each layer.
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OSI model
 The early development of networks was
disorganized in many ways.
 International Organization for Standardization
(ISO)
 The Open System Interconnection (OSI)
reference model released in 1984.
 It is considered the best tool available for
teaching people about sending and receiving
data on a network.
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OSI model (cont.)
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OSI layers
 The OSI reference model is a framework that is used
to understand how information travels throughout a
network.
 Advantages
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It breaks network communication into smaller, more
manageable parts.
It standardizes network components to allow multiple
vendor development and support.
It allows different types of network hardware and
software to communicate with each other.
It prevents changes in one layer from affecting other
layers.
It divides network communication into smaller parts to
make learning it easier to understand.
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OSI layers (cont.)
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OSI layers (cont.)
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OSI layers (cont.)
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OSI layers (cont.)
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OSI layers (cont.)
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OSI layers (cont.)
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OSI layers (cont.)
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Peer-to-peer communications
 Peer-to-peer : In order for data to travel from the source to the
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destination, each layer of the OSI model at the source must
communicate with its peer layer at the destination.
Each layer of communication on the source computer
communicates with a layer-specific PDU (Protocol Data Unit),
and with its peer layer on the destination computer.
The lower layer uses encapsulation to put the PDU from the
upper layer into its data field; then it adds whatever headers and
trailers the layer needs to perform its function.
Next, as the data moves down through the layers of the OSI
model, additional headers and trailers are added.
Segments : layer 4 PDU
Packets
: layer 3 PDU
Frames
: layer 2 PDU
Bits
: layer 1 PDU
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Peer-to-peer communications (cont.)
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Peer-to-peer communications
(cont.)
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TCP/IP model
 The U.S. Department of Defense (DoD)
created the TCP/IP reference model.
 For military purposes
 TCP/IP
 TCP is a connection-oriented protocol.
 Best path determination and packet
switching occur at IP layer.
 IP can be thought to point the way for the
packets, while TCP provides a reliable
transport.
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TCP/IP model (cont.)
TCP/IP Common Protocols
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TCP/IP model (cont.)
 Application layer protocols
File Transfer Protocol (FTP)
 Hypertext Transfer Protocol (HTTP)
 Simple Mail Transfer Protocol (SMTP)
 Domain Name System (DNS)
 Trivial File Transfer Protocol (TFTP)
 Transport layer protocols
 Transport Control Protocol (TCP)
 User Datagram Protocol (UDP)
 Internet layer
 Internet Protocol (IP)
 Network access layer
 refers to any particular technology used on a specific network.
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TCP/IP model (cont.)
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TCP/IP model (cont.)
 Similarities include:
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Both have layers.
Both have application layers, though they include very different services.
Both have comparable transport and network layers.
Both models need to be known by networking professionals.
Both assume packets are switched. This means that individual packets may
take different paths to reach the same destination. This is contrasted with
circuit-switched networks where all the packets take the same path.
 Differences include:
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TCP/IP combines the presentation and session layer issues into its
application layer.
TCP/IP combines the OSI data link and physical layers into the network
access layer.
TCP/IP appears simpler because it has fewer layers.
TCP/IP protocols are the standards around which the Internet developed, so
the TCP/IP model gains credibility just because of its protocols. In contrast,
networks are not usually built on the OSI protocol, even though the OSI
model is used as a guide.
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TCP/IP model (cont.)
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Detailed encapsulation process
 5 conversion steps in order to encapsulate
data:
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Build the data.
Package the data for end-to-end transport.
Add the network IP address to the header.
Add the data link layer header and trailer.
Convert to bits for transmission.
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Detailed encapsulation process (cont.)
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Detailed encapsulation process (cont.)
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 END
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