dcet ccn 3 internetworking
TRANSCRIPT
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Why have Computer Networks?
Resource sharing
Communication
Information sharing
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Different Types of Computer
Networks Switched Networks and Broadcast
Networks
Local Area Networks - LANs Metropolitan Area Networks - MANs
Wide Area Networks - WANs
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Switched Networks and
Broadcast Networks In switched networks the message travels
from one node to another on its path from
source to destination. The message onlytravels through the nodes that are
necessary to pass from a given source to
a destination. Example Telephone
Network.
In Broadcast networks the message is
sent to all the nodes on the network.
Example Ethernet Local Area Network.
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Local Area Networks
Small geographical area. Less than 1 km.
A floor or a building.
Owned by a department or anorganization.
Very high speeds and low latency.
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Metropolitan Area Networks
Medium size geographical area. 10 km.
A campus or a city.
Owned by a large organization or a groupof organizations.
High speeds and medium latency.
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Wide Area Networks
Long distances. 100 km.
Owned by very large organizations,
governments, telcos. Low to high speed and high latency.
Two Types Of WAN
Circuit Switching Packet Switching
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Circuit-Switching
Definition: Communication in which a dedicatedcommunications path is established between two
devices through one or more intermediate switching
nodes Oldest Networking Technology - more than a
hundred years old
Dominant in both voice and data communications
today
e.g. PSTN is a circuit-switched network
Relatively inefficient (100% dedication even without
100% utilization)
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Circuit Switching
In circuit switching network any two
stations wishing to communicate first
establish a connection by requesting to the
network.
The network responds by arranging a
connection in such a way that a
dedicated/physical path is establishedbetween the two parties
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Circuit Switching Networks
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Packet Switching
Packet Switching refers to protocols in which
messages are divided into packets before they
are sent. Each packet is then transmitted
individually and can even follow different routesto its destination. Once all the packets forming a
message arrive at the destination, they are
recompiled into the original message.
Examples X.25, and Frame Relay, are based on
packet-switching technologies
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Packet Switching Networks
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What is the Internet?
A world-wide network of networks.
The whole thing started in the late 1960s when the
US Government through its Advanced Research
Project Agency (ARPA) decided to set up contractwork with universities and corporate research
community representatives to interconnect world-
wide computers in a single network.
In 1969 the first internetwork (ARPANET) occurredwith 4 nodes using routing devices that allowed data
packet deliveries between otherwise incompatible
computers.
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OSI Reference Model
Application
Presentation
Session
Transport
Network
Datalink
Physical
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Open Systems Interconnection
(OSI) Reference Model
y The Open Systems Interconnection ( OSI ) reference
model describes how information from a software
application in one computer moves through a network
medium to a software application in another computer.
y The OSI reference model is a conceptual model
composed of seven layers, each specifying particular
network functions.
y The model was developed by the International
Organization for Standardization (ISO) in 1984, and it is
now considered the primary architectural model for
intercomputer communications.
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Protocols
y The OSI model provides a conceptual framework
for communication between computers, but the
model itself is not a method of communication.
Actual communication is made possible by using
communication protocols.
yA protocol is a formal set of rules and conventions
that governs how computers exchange information
over a network medium.
y A protocol implements the functions of one or
more of the OSI layers.
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Headers and data can be
encapsulated during information
exchange.
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Physical Layer
The Physical Layerdescribes the physical
properties of the various communications media,
as well as the electrical properties and
interpretation of the exchanged signals. Ex: thislayer defines the size of Ethernet coaxial cable,
the type of BNC connector used, and the
termination method.
Electrical - Signals specifications and properties,
Electrical Properties (impedance)
Mechanical - Physical Media dimensions,
Connectors
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Datalink Layer
y The data link layer provides
y physical addressing
Physical addressing as opposed to network addressing defines how
devices are addressed at the data link layer.,
y network topology,
Network topology consists of the data-link layer specifications that
often define how devices are to be physically connected, such as in
a bus or a ring topology
y error notification, Error notification alerts upper-layer protocols that a transmission
error has occurred
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sequencing of frames
The sequencing of data frames reorders frames that are
transmitted out of sequence
flow control.
flow control moderates the transmission of data so that the
receiving device is not overwhelmed with more traffic than it can
handle at one time.
The Institute of Electrical and Electronics Engineers (IEEE) hassubdivided the data-link layer into two sublayers: Logical Link
Control (LLC) and Media Access Control (MAC)
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Network Layer
y The network layer provides routing and related
functions that enable multiple data links to be
combined into an internetwork. This is
accomplished by the logical addressing as
opposed to the physical addressing of devices.
y The network layer supports both connection-
oriented and connectionless service from higher-
layer protocols.
y Some Examples include Border Gateway Protocol(BGP); Open Shortest Path First (OSPF); and
Routing Information Protocol (RIP),
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Transport Layer
y The transport layer implements reliable
internetwork data transport services that are
transparent to upper layers.
y
Transport-layer functions typically includey flow control
Flow control manages data transmission between
devices so that the transmitting device does not send
more data than the receiving device can process.
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ymultiplexing,
Multiplexing enables data from several applications tobe transmitted onto a single physical link.
y virtual circuit management,
Virtual circuits are established, maintained, and
terminated by the transport layer.
y error checking and recovery.
Error checking involves creating various mechanisms
for detecting transmission errors, while error recovery
involves taking an action, such as requesting thatdata be retransmitted, to resolve any errors that
occur.
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Basic difference between this layer and lower
layers is that it provides an end-to-end reliable
transfer of data packet
Some examples are Transmission Control
Protocol,(TCP) is the protocol in the TCP/IP suite
that provides reliable transmission of data.
UDP Connectionless protocol
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Session Layer
Establishes, manages, and terminatesconnections (sessions) between applicationprocesses
Gives a session service by tokenmanagement
Responsible for check pointing recovery bysynchronization
The Session Layer provides the means fortwo application layer entities to synchronizeand manage their data exchange.
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y Some examples of session-layer implementations
include Zone Information Protocol (ZIP), the
AppleTalk protocol; and Session Control Protocol
(SCP),
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Presentation Layer
y The presentation layer provides a variety of coding
and conversion functions that are applied to
application layer data.
y . Some examples of presentation-layer coding andconversion schemes include
y common data representation formats,
y conversion of character representation
formats ,such as EBCDIC and ASCII
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y common data compression schemes, ,such as Some well-known standards for video
include QuickTime and Motion (MPEG). For the
graphic image formatsar
e Graphics InterchangeFormat (GIF), Joint Photographic Experts Group
(JPEG), and Tagged Image File Format (TIFF).
y common data encryption schemes.
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Application Layer
y The application layer is the OSI layer closest to the
end user, which means that both the OSI
application layer and the user interact directly with
the software application.
Two key types of application-layer implementations are
y TCP/IP applications
TCP/IP applications are protocols, such as Telnet, File
Transfer Protocol (FTP), and Simple Mail TransferProtocol (SMTP)
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Networking Devices
Hubs, Repeaters, Concentrators
Switches, Bridges
Routers
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Repeaters ,Bridges, Switches
and Routers
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Repeaters
Operate at the Physical Layer
Attempt to forward all Frames
Error Frames will be forwarded
Collision domains are not isolated Broadcast domains are not isolated
A repeater receives and then immediatelyretransmits each bit.
A repeater has no memory and does not dependon any particular protocol. It duplicateseverything, including the collisions.
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Bridges
A bridge is a device which has two or more
ports which can be connected to a variety of
media types, and provides a mechanism for
the filtering and forwarding of data framesamong the ports while building one large
logical network.
Operate at the Data Link Layer
Selectively forwards frames Error Frames will not be forwarded
Collision domains are isolated
Broadcast domains are not isolated
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Routers
Operate at the Network Layer
Selectively forwards frames
Error Frames will not be forwarded Collision domains are isolated
Broadcast domains are isolated
Protocols can be Filtered Has an effect on MAC Addresses but no
effect on Network Addresses