Transcript Chapter 2 Internetworking

Computer
Chapter 2
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INTERNETWORKING
TOPIC
Internetworking Basics
 Internetworking Model
 The OSI Reference Model
 Ethernet Networking
 Wireless Networking
 Data Encapsulation

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Computer
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INTERNETWORK BASIC
POSSIBLE CAUSES OF LAN TRAFFIC
CONGESTION ARE
 Too
 Adding
hubs for connectivity to the
network
A
large amount of ARP or IPX traffic (IPX
is a Novell
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many hosts in a broadcast domain
 Broadcast storms
 Multicasting
 Low bandwidth
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NETWORK SEGMENTATION

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Collision domain
 Broadcast domain
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TWO ADVANTAGES OF USING
ROUTERS IN YOUR NETWORK ARE
They don’t forward broadcasts by default.

They can filter the network based on layer
3
(Network layer) information (i.e., IP address).
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
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FOUR ROUTER FUNCTIONS IN YOUR
NETWORK CAN BE LISTED AS
Packet switching
 Packet filtering
 Internetwork communication
 Path selection

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INTERNETWORKING MODEL
The Layered Approach
 Advantages of Reference Models

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It divides the network communication process into
smaller and simpler components, thus aiding component
development, design, and troubleshooting.
It allows multiple-vendor development through
standardization of network components.
It encourages industry standardization by defining
what functions occur at each layer of the model.
It allows various types of network hardware and
software to communicate.
It prevents changes in one layer from affecting other
layers, so it does not hamper development.
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
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THE OSI REFERENCE MODEL
The upper layers

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THE LOWER LAYERS
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LAYER FUNCTIONS
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INTERFACES: VERTICAL (ADJACENT
LAYER) COMMUNICATION
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PROTOCOLS: HORIZONTAL
(CORRESPONDING LAYER) COMMUNICATION
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DATA ENCAPSULATION
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TCP/IP PROTOCOLS
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TCP/IP PROTOCOLS
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PROTOCOL DATA UNITS (PDUS) AND
SERVICE DATA UNITS (SDUS)
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INDIRECT DEVICE CONNECTION AND
MESSAGE ROUTING
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APPLICATION LAYER

Sample ->
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World Wide Web (WWW)
E-mail gateways
Electronic data interchange (EDI)
Special interest bulletin boards
Internet navigation utilities
Financial transaction services
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
The Application layer of the OSI model marks the
spot where users actually communicate to the
computer.
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THE PRESENTATION LAYER
It presents data to the Application layer and is
responsible for data translation and code
formatting.
 This layer is essentially a translator and provides
coding and conversion functions. A successful
data-transfer technique is to adapt the data into
a standard format before transmission.

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THE SESSION LAYER
 The
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Session layer is responsible for setting
up, managing, and then tearing down
sessions between Presentation layer
entities.
 This layer also provides dialogue control
between devices, or nodes. It coordinates
communication between systems, and
serves to organize their communication by
offering three different modes: simplex,
half duplex, and full duplex.
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THE TRANSPORT LAYER
 The
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Transport layer segments and
reassembles data into a data stream.
 Services located in the Transport layer
both segment and reassemble data from
upper-layer applications and unite it onto
the same data stream.
 They provide end-to-end data transport
services and can establish a logical
connection between the sending host and
destination host on an internetwork.
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The Transport layer is responsible for providing
mechanisms for multiplexing upper-layer
applications, establishing sessions, and tearing
down virtual circuits.
 The Transport layer can be connectionless or
connection-oriented.
 Some of you are probably familiar with TCP and
UDP already.

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FLOW CONTROL
 Data
The segments delivered are acknowledged
back to the sender upon their reception.
 Any segments not acknowledged are
retransmitted.
 Segments are sequenced back into their proper
order upon arrival at their destination.
 A manageable data flow is maintained in order
to avoid congestion, overloading, and data loss.

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integrity is ensured at the Transport
layer by maintaining flow control and by
allowing users to request reliable data
transport between systems.
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CONNECTION-ORIENTED
COMMUNICATION

a call setup, or a three way handshake
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TRANSMITTING SEGMENTS WITH
FLOW CONTROL
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ACKNOWLEDGMENTS
 It
 This
is achieved through something called
positive acknowledgment with
retransmission a technique that requires a
receiving machine to communicate with
the transmitting source by sending an
acknowledgment message back to the
sender when it receives data.
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guarantees that the data won’t be
duplicated or lost.
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WINDOWING
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THE NETWORK LAYER
 The
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Data packets : routed protocol
Route update packets : routing protocol
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Network layer (also called layer 3)
manages device addressing, tracks the
location of devices on the network, and
determines the best way to move data,
which means that the Network layer must
transport traffic between devices that
aren’t locally attached.
 Two types of packets are used at the
Network layer:
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ROUTING TABLE USED IN A ROUTER
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HERE ARE SOME POINTS ABOUT ROUTERS THAT YOU
SHOULD REALLY COMMIT TO MEMORY:
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Routers, by default, will not forward any broadcast or
multicast packets.
Routers use the logical address in a Network layer header
to determine the next hop router to forward the packet to.
Routers can use access lists, created by an administrator,
to control security on the types of packets that are allowed
to enter or exit an interface.
Routers can provide layer 2 bridging functions if needed
and can simultaneously route through the same interface.
Layer 3 devices (routers in this case) provide connections
between virtual LANs (VLANs).
Routers can provide quality of service (QoS) for specific
types of network traffic.
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THE DATA LINK LAYER
The Data Link layer provides the physical
transmission of the data and handles error
notification, network topology, and flow control.
 The Data Link layer formats the message into
pieces, each called a data frame, and adds a
customized header containing the hardware
destination and source address.

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DATA LINK LAYER WITH THE ETHERNET
AND IEEE SPECIFICATIONS.
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THE IEEE ETHERNET DATA LINK
LAYER HAS TWO SUBLAYERS:
 Media
 Logical
Link Control (LLC) 802.2
Responsible for identifying Network layer
protocols and then encapsulating them.
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Access Control (MAC) 802.3
Defines how packets are placed on the
media. Contention media access is “first
come/first served” access where everyone
shares the same bandwidth—hence the
name. Physical addressing is defined here,
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SWITCHES AND BRIDGES AT THE DATA
LINK LAYER
 Layer
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based bridging because it uses specialized
hardware called an application-specific
integrated circuit (ASIC).
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THE PHYSICAL LAYER
we find that the Physical layer does two things: It
sends bits and receives bits. Bits come only in
values of 1 or 0—a Morse code with numerical
values.
 The Physical layer specifies the electrical,
mechanical, procedural, and functional
requirements for activating, maintaining, and
deactivating a physical link between end
systems.
 This layer is also where you identify the interface
between the data terminal equipment (DTE) and
the data communication equipment (DCE).

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HUBS AT THE PHYSICAL LAYER

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A hub is really a multiple-port repeater. A
repeater receives a digital signal and
reamplifies or regenerates that signal, and
then forwards the digital signal out all active
ports without looking at any data.
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Computer
Lecture 2-2
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ETHERNET NETWORKING
THE SUCCESS OF ETHERNET IS DUE
TO THE FOLLOWING FACTORS:
Simplicity and ease of maintenance
 Ability to incorporate new technologies
 Reliability
 Low cost of installation and upgrade

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802.3 ETHERNET IN RELATION TO THE
OSI MODEL
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IEEE 802.X STANDARDS
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ETHERNET TECHNOLOGIES MAPPED TO THE
OSI MODEL
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ETHERNET ADDRESSING
 We
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get into how Ethernet addressing
works. It uses the Media Access Control
(MAC) address burned into each and
every Ethernet Network Interface Card
(NIC).
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MAC ADDRESS FORMAT
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GENERIC FRAME FORMAT
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IEEE 802.3
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ETHERNET II FRAME FORMAT
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ETHERNET II AND IEEE 802.3 FRAME
FORMAT
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MEDIA ACCESS CONTROL (MAC)
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MAC RULES AND COLLISION
DETECTION/BACKOFF
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MAC RULES AND COLLISION
DETECTION/BACKOFF
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ETHERNET TIMING
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INTERFRAME SPACING
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BACKOFF
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ERROR HANDLING
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TYPES OF COLLISIONS
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THE EFFECTS OF HAVING A CSMA/CD NETWORK
SUSTAINING HEAVY COLLISIONS INCLUDE
Delay
 Low throughput
 Congestion

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ETHERNET ERRORS
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ETHERNET ERRORS
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FCS ERRORS
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PARAMETERS FOR 10 MBPS
ETHERNET OPERATION
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MANCHESTER ENCODING EXAMPLES
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PARAMETERS FOR 100-MBPS ETHERNET
OPERATION
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MLT-3 ENCODING EXAMPLE (100BASETX)
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NRZI ENCODING EXAMPLES (100BASEFX)
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PARAMETERS FOR GIGABIT
ETHERNET OPERATION
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ACTUAL 1000BASE-T SIGNAL
TRANSMISSION
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GIGABIT ETHERNET LAYERS
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GIGABIT ETHERNET MEDIA COMPARISON
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PARAMETERS FOR 10-GBPS ETHERNET
OPERATION
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10GBASE LX-4 SIGNAL
MULTIPLEXING
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Computer
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WIRELESS NETWORKING
BENEFITS OF WLANS
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EVOLUTION OF WIRELESS LANS
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UNLICENSED FREQUENCY BANDS
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WIRELESS TECHNOLOGIES
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DISTANCE VERSUS SPEED
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WIRELESS TECHNOLOGIES
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IN-BUILDING WLANS
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THE IEEE 802 STANDARDS
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IEEE 802.11 PROTOCOLS
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IEEE 802.11 STANDARDS
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Computer
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DATA ENCAPSULATION
DATA ENCAPSULATION
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SUMMARY



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
OSI model—the seven-layer model used to help application
developers design applications that can run on any type of
system or network. Each layer has its special jobs and
select responsibilities within the model to ensure that solid,
effective communications do, in fact, occur.
Remember that hubs are Physical layer devices and repeat
the digital signal to all segments except the one it was
received from.
Switches segment the network using hardware addresses
and break up collision domains.
Routers break up broadcast domains (and collision
domains) and use logical addressing to send packets
through an internetwork.
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