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Network Review


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Title: Network Review

Network Review
Advanced Computer Networks
By Mahdi Sadeghizadeh
Network Review
  • Computer network A collection of computing
    devices that are connected in various ways in
    order to communicate and share resources.
  • Advantages of networks
  • Communications
  • Data Resources sharing
  • Reliability
  • Cost reduction
  • Scalability .
  • Disadvantages of networks
  • Security Issues
  • Rapid spread of Viruses
  • Expensive Setup
  • Dependency on the Main File Server

Network Architectures
  • Client/Server Architecture
  • Peer-to-Peer Architecture

Types of Servers
  • File Server
  • Internet Server
  • Email Server
  • DNS Server
  • RAS Server
  • Application Service Provider (ASP)
  • Storage Service Provider (SSP)

Network Topologies
  • Various configurations, called topologies
  • Bus topology
  • Ring topology
  • Star topology
  • Mesh topology
  • Tree topology

Types of Networks
  • Personal Area Network
  • Home Area Network
  • Local Area Networks
  • Campus Area Network
  • Metropolitan Area Networks
  • Wide Area Networks

Comparison Of Networks
  • An internet is a group of networks linked
    together with routers in a way that allows an
    application program on any station on any network
    in the internet to be able to communicate with an
    application program on another station on any
    other network.

Internet Usage
  • Traditional applications (1970 1990)
  • E-mail
  • News
  • Remote login
  • File transfer

Architecture of the Internet
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Network Equipments
Transmission Media
Network links
  • Guided ? wires, cables
  • Twisted-Pair cables
  • Coaxial cables
  • Fiber-optic cables
  • Unguided ? wireless transmission,
  • e.g. radio, microwave, infrared, sound, sonar

Network Equipments
Network nodes
  • network interface controller (NICs)
  • repeater
  • hub
  • bridge
  • switch
  • router
  • modem
  • firewall

A repeater is an electronic device that receives
a network signal, cleans it of unnecessary noise,
and regenerates it. The signal is retransmitted
at a higher power level, or to the other side of
an obstruction, so that the signal can cover
longer distances without degradation.
A bridge can connect two different types of
topologies. Or, A network bridge connects and
filters traffic between two network segments at
the data link layer (layer 2) of the OSI model to
form a single network.
Modems (MOdulator-DEModulator) are used to
connect network nodes via wire not originally
designed for digital network traffic, or for
wireless. To do this one or more frequencies are
modulated by the digital signal to produce an
analog signal that can be tailored to give the
required properties for transmission. Modems are
commonly used for telephone lines, using a
Digital Subscriber Line technology.
A firewall is a network device for controlling
network security and access rules. Firewalls are
typically configured to reject access requests
from unrecognized sources while allowing actions
from recognized ones.
A router is an internetworking device that
forwards packets between networks by processing
the routing information included in the packet or
datagram (Internet protocol information from
Network layer (layer 3)).
A network switch is a device that forwards and
filters OSI layer 2 datagrams between ports based
on the MAC addresses in the packets. A switch is
distinct from a hub in that it only forwards the
frames to the physical ports involved in the
communication rather than all ports connected. It
can be thought of as a multi-port bridge.
A network interface controller (NIC) is computer
hardware that provides a computer with the
ability to access the transmission media, and has
the ability to process low-level network
A hub is a multiport repeater that retransmits a
signal on all ports
  • In telecommunications and computer networks,
    multiplexing is a method by which multiple analog
    message signals or digital data streams are
    combined into one signal over a shared medium.
    The aim is to share an expensive resource.
  • The multiplexed signal is transmitted over a
    communication channel, which may be a physical
    transmission medium. A reverse process, known as
    demultiplexing, can extract the original channels
    on the receiver side.
  • Types of multiplexing
  • Space-division multiplexing (SDM)
  • Frequency-division multiplexing (FDM)
  • wavelength-division multiplexing (WDM)
  • Time-division multiplexing (TDM)
  • Polarization-division multiplexing (PDM)
  • Orbital angular momentum multiplexing
  • Code-division multiplexing (CDM)

In wired communication, space-division
multiplexing simply implies different
point-to-point wires for different channels. In
wireless communication, space-division
multiplexing is achieved by multiple antenna
elements forming a phased array antenna.
Switching Decision
  • In large networks there might be multiple paths
    linking sender and receiver. Information may be
    switched as it travels through various
    communication channels. There are four typical
    switching techniques available for digital
  • Circuit Switching
  • Packet Switching
  • Message Switching
  • Cell Switching

Circuit switching is a methodology of
implementing a telecommunications network in
which two network nodes establish a dedicated
communications channel (circuit) through the
network before the nodes may communicate. The
circuit guarantees the full bandwidth of the
channel and remains connected for the duration of
the communication session.
Packet switching is a digital networking
communications method that groups all transmitted
data regardless of content, type, or structure
into suitably sized blocks, called packets.
Communications protocols
  • A communications protocol is a set of rules for
    exchanging information over network links.
  • Ethernet
  • Internet Protocol Suite
  • Asynchronous Transfer Mode

Network Software
  • Layer Programming
  • The OSI Reference Model
  • The TCP/IP Reference Model
  • Communications protocols A communications
    protocol is a set of rules for exchanging
    information over network links.
  • Layer services Connection-Oriented
    Connectionless services.

Protocol Hierarchies
  • Layers, protocols, and interfaces

Protocol Hierarchies
  • Example information flow supporting virtual
    communication in layer 5

Reference Models
  • The OSI Reference Model
  • The TCP/IP Reference Model

OSI Reference Model
  • Network layer
  • main Functions of the network layer include
  • Routing and addressing Provides connectivity and
    path selection between two systems
  • Congestion Control
  • Solve the problem of Heterogeneous Networks
  • Protocols
  • IPv4/IPv6, Internet Protocol
  • ICMP, Internet Control Message Protocol
  • IGMP, Internet Group Management Protocol
  • IPsec, Internet Protocol Security
  • IPX, Internetwork Packet Exchange
  • RIP, Routing Information Protocol
  • DDP, Datagram Delivery Protocol
  • ARP, Address Resolution Protocol
  • Physical layer
  • The purpose of the physical layer is to govern
    the transmission of bits one at a time over a
    wire, radio, or other connection between a
    station and a switch, between pairs of switches,
    or between a switch and a router.
  • Defines mechanical, functional, procedural and
    electrical aspects of networking
  • Includes connectors, circuits, voltage levels and
  • Data Link layer
  • Faraming Converts data from upper layers into
    logical packages or frames or Encapsulation of
    network layer data packets into frames
  • Converts logical frames into raw bits that are
    transmitted by the Physical layer
  • Error detection and correction The data link
    layer provides a reliable link between two
    directly connected nodes, by detecting and
    possibly correcting errors that may occur in the
    physical layer.
  • Flow control Solve the problem of mismatch
    between the transmitter and receiver speed.
  • Transport layer
  • Provides a virtual end-to-end connection so that
    data transferred between two hosts will arrive
    without errors and in the correct order.
  • The transport layer provides convenient services
  • connection-oriented data stream support,
  • Reliability solve the problem of Packet Loss
  • flow control
  • Multiplexing Ports can provide multiple
    endpoints on a single node.
  • Protocols
  • Application layer
  • The application layer is the OSI layer closest to
    the end user, which means both the OSI
    application layer and the user interact directly
    with the software application.
  • Application-layer functions typically include
  • identifying communication partners
  • determining resource availability
  • synchronizing communication
  • Protocols
  • Remote login category Telnet, SSH
  • File transfer category FTP, TFTP
  • Electronic mail category SMTP, IMAP, POP
  • Support services category DNS, RARP,
  • Web HTTP,
  • Presentation layer
  • The presentation layer is responsible for the
    delivery and formatting of information to the
    application layer for further processing or
    display. Services
  • Data conversion Translates data from the
    Application layer into an intermediary format
  • Encryption, Decryption and compresses data
  • Character code translation
  • Protocols
  • Apple Filing Protocol (AFP)
  • Independent Computing Architecture (ICA)
  • Lightweight Presentation Protocol (LPP)
  • Network Data Representation (NDR)
  • Telnet (a remote terminal access protocol)
  • eXternal Data Representation (XDR),
  • Session layer
  • The session layer controls the dialogues
    (connections) between computers. It establishes,
    manages and terminates the connections between
    the local and remote application.
  • Allows two applications on different computers to
    establish dialog control
  • Regulates which side transmits
  • Determines the time and length of the
  • It provides for
  • Authentication and Authorization
  • full-duplex, half-duplex, or simplex operation
  • Session restoration (checkpointing and recovery)
  • Adjournment, termination and restart procedures
  • TCP, Transmission Control Protocol
  • UDP, User Datagram Protocol
  • ATP, AppleTalk Transaction Protocol
  • FCP, Fiber Channel Protocol

Voltage levels To represent 1s and 0s
  • NBF, NetBIOS Frames protocol
  • RDP, Reliable Datagram Protocol
  • SPX, Sequenced Packet Exchange
  • SST, Structured Stream Transport

Transmission Media
OSI Reference Model
Comparing OSI and TCP/IP Models
  • There is exact separation between Services,
    interfaces and protocols concepts in OSI model.
  • The OSI Reference Model is based on OOP.
  • OSI designers had not enough designing
  • TCP/IP is a practical standard.
  • There is not enough security in TCP/IP

Thank You