Transcript Networking Fundamentals - SXU Computer Science

Networking
Fundamentals
CMPSC 255
Fall 2004
Aims
 By the end of this Module you should be able to:
 Briefly outline the history of networking.
 Identify devices used in networking.
 Understand the role of protocols in networking.
 Define LAN, WAN, MAN, and SAN.
 Explain VPNs and their advantages.
 Describe the differences between intranets and extranets.
 Explain bandwidth in networking as units of measurement.
 Explain the difference between bandwidth and throughput.
 Calculate data transfer rates.
 Describe the OSI Model in relation to Layers, Functions, Protocols and Devices
 Identify the four layers of the TCP/IP model and describe the similarities and
differences between the two models.
Network Evolution
 Sneakernet
 Used when few computers
were available
 Stand alone computers
 Files transferred by copying
to disk and physically
delivering it to destination
 Makes it difficult to track
current file version
 Wastes time
Network Evolution
 Local Area Networks
 Connected computers on a
shared medium
 Enabled users to share files
electronically
 More efficient
 Standards developed to allow
equipment from different
vendors to interoperate
Network Evolution
 Wide Area Networks
 As corporations grew wider
communication was needed
 Each branch of a corporation
became isolated
 Files sent by post or courier
 Solution
 WAN standards developed
 Companies were able to
communicate with other
networks globally
Network Terminology
 Network Devices
Topologies
 Network Topologies Describe
 Structure of the network
 Physical Layout of Cabling (Physical Topology)
 How the media is accessed by communicating hosts (Logical
Topology)
 Common Physical Topologies
Bus Topology
 Uses a single backbone cable that is
terminated at both ends.
 All the hosts connect directly to this backbone
 Bandwidth is shared between the number of
hosts on Network
 Can be Logical or Physical
Star Topology
 A star topology connects all cables to a central point of
concentration
 Can be a Logical Bus or Ring
 Concentrator can be a
 Hub
 Switch
 MSAU
Ring Topology
 Connects one host to the next and the last host
to the first
 This creates a physical ring of cable
 Can be Logical or Physical
Extended Star Topology
 Links individual star wired network segments
together
 Uses hubs and/or switches
 This topology can extend the scope and
coverage of the network
Hierarchical Topology
 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
Mesh Topology
 Implemented to provide as much protection as possible
from interruption of service
 The use of a mesh topology in the networked control
systems of a nuclear power plant would be an excellent
example
 Each host has its own connections to all other hosts.
 Internet has multiple paths to any one location but it
does not adopt the full mesh topology.
Logical Topologies
 Defines how the hosts communicate across the medium
 The two most common types of logical topologies are:

Broadcast topology
 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 as will be explained later in the
course.

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.
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.
 Protocols control data communication, which include the
following:
 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
Network Protocols
 Protocols are created and maintained by
organizations and committees such as:
 Institute of Electrical and Electronic Engineers (IEEE)
 American National Standards Institute (ANSI)
 Telecommunications Industry Association (TIA)
 Electronic Industries Alliance (EIA)
 International Telecommunications Union (ITU)
Local Area Networks (LANs)
 LANs consist of the following
components:
 Computers
 Network interface cards
 Peripheral devices
 Networking media
 Network devices
LAN Components
 LANs are designed to:
 Operate in a limited geographical area
 Allow multiple access to high-bandwidth media
 Control the network privately under local administrative control
 Provide full time connectivity to local services
 Connect physically adjacent devices
WAN Components
 WANs are designed to:
 Operate over a large geographical area
 Allow access over serial interfaces at lower speeds
 Provide full and part time connectivity
 Connect devices separated over wide, even global areas
LAN and WAN Technologies
 Common LAN technologies are:
 Ethernet
 Token Ring
 FDDI
 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)
Metropolitan Area Network
 A network that spans a
metropolitan area such as
a city or suburban area.
 Usually consists of two or
more LANs in a common
geographic area.
 A service provider is used
to connect two or more
LAN sites
 Can also be created using
wireless technology
Storage Area Network
 A dedicated, highperformance network
used to move data
between servers and
storage resources.
 SAN technology allows
high-speed server-tostorage,
 Offers the following
features:
 Availability
 Scalability
Virtual Private Networks
 A private network
that is constructed
within a public
network
infrastructure such
as the Internet
 Uses a secure tunnel
through the Internet
between the
telecommuter’s PC
and a VPN router in
the headquarters
Intranet and Extranet VPNs
Bandwidth
 Why Bandwidth is important
 Bandwidth is limited by Physics and Technology
 Regardless of the media used to build the network there are limits on the
capacity of that network to carry information.
 Bandwidth is limited by the laws of physics and by the technologies used to
place information on the media.

Bandwidth is not free
 WAN connectivity must be purchased from a service provider

Bandwidth requirements are growing at a rapid rate
 More and more companies are using WAN services which require more and
more bandwidth

Bandwidth is critical to network performance
 The higher the bandwidth the more information can be transferred in a shorter
time
Bandwidth
 Bandwidth Analogy 1
Bandwidth
 Bandwidth Analogy 2
Bandwidth
 Units of Bandwidth
 Bandwidth is the measure of how much information, or bits, can flow
from one place to another in a given amount of time
 Although bandwidth can be described in bits per second, usually
some multiple of bits per second is used.
Limitations
 Bandwidth is limited by a number of
factors
 Media
 Network devices
 Physics
 Each have their own limiting factors
 Actual bandwidth of a network is
determined by a combination of the
physical media and the technologies
chosen for signaling and detecting
network signals
Media bandwidth and limitations
Media
Max Length
Max Bandwidth
50 Ohm Coaxial Cable
(10Base2) Thin Ethernet
185m
10Mbps
50 Ohm Coaxial Cable
(10Base5) Thick Ethernet
500m
10Mbps
Category 5 Unshielded Twisted Pair (UTP)
(10BaseT) Ethernet
100m
10Mbps
Category 5 Unshielded Twisted Pair (UTP)
(100BaseTX) Ethernet
100m
100Mbps
Category 5 Unshielded Twisted Pair (UTP)
(1000BaseTX) Ethernet
100m
1000Mbps
Multimode Optical Fibre
62.5/125mm 100BaseFX Ethernet
2000m
100Mbps
Multimode Optical Fibre
62.5/125mm 1000BaseSX Ethernet
220m
1000Mbps
Multimode Optical Fibre
50/125mm 1000BaseSX Ethernet
550m
1000Mbps
Single mode Optical Fibre
9/125mm 1000BaseLX Ethernet
5000m
1000Mbps
Throughput
 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.
 Is determines by the following factors
 Internetworking devices
 Type of data being transferred
 Network topology
 Number of users on the network
 User computer
 Server computer
 Power conditions
Transfer Time Calculation
 Data Transfer Calculation
 Best Download: T=S/BW
 Typical Bandwidth: T=S/P
 Where
 T = Transfer time in seconds
 S = Size of file in Bits
 BW = Maximum theoretical bandwidth (slowest link
between source and destination devices
 P = Actual throughput at moment of transfer in Bps
Layered models
 Using a layered model
 Breaks network communication into smaller, more
manageable parts.
 Standardizes network components to allow multiple vendor
development and support.
 Allows different types of network hardware and software to
communicate with each other.
 Prevents changes in one layer from affecting other layers.
 Divides network communication into smaller parts to make
learning it easier to understand.
OSI Model
 Open Standards
Interconnection Model
(OSI Model)
 Released by International
Standards Organisation (ISO) in
1984
 Standardised communications
between different vendor hardware
and software
 Consists of 7 Layers
 Each layer described a specific
aspect of network communication
Layer 1
 The physical layer is
concerned with
transmitting raw bits
over a medium
 Wires
 Connectors
 Voltages
 Data rates
Layer 2
 Controls the direct
link to the media
 How media is
accessed
 Physical addressing
 Network topology
 Flow control
 Error Notification
Layer 3
 Logical Addressing
 Best Path Determination
 “Best Effort” delivery of data
between networks
Layer 4
 End-to-end Connections
 Concerned with transportation
issues between hosts
 Reliable delivery of data
 Establishes, maintains and
terminates virtual circuits
 Error recovery and data flow
Layer 5
 Host to host
communication
 Establishes, manages and
terminates sessions between
applications
Layer 6
 Data representation
 Ensure data is readable with
receiving system
 Data format
 Data Structure
 Negotiates data transfer
syntax for application layer
Layer 7
 Provides network
services for
applications
 e-mail, file transfer, terminal
emulation
Peer to Peer Communication
Host 1
Host 2
TCP/IP Model
 Developed by the US
DoD
 Designed as an open
standard
 Is robust enough to
survive any conditions
(even nuclear war)
 Is the standard used for
communication on the
Internet
TCP/IP Vs OSI
TCT/IP
OSI
Labs
 Lab 2.3.6
 OSI Model and TCP/IP Model
 Lab 2.3.7
 OSI Model Characteristics and Devices
TCP/IP Protocols
Protocols and TCP/IP
Data Encapsulation
Analog Vs Digital
 Is measured by how much of the electromagnetic
spectrum is occupied by each signal
 The basic unit of analog bandwidth is hertz (Hz)
 Units of measurement that are commonly seen are
 kilohertz (KHz)
 megahertz (MHz)
 gigahertz (GHz).
 These are the units used to describe the bandwidths of
cordless telephones
 Operate at either 900 MHz or 2.4 GHz.
 These are also the units used to describe the bandwidths
of IEEE 802.11a and 802.11b wireless networks
 operate at 5 GHz and 2.4 GHz.