Download Chapter 2 Internetworking

Internetworking
Chapter 2
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Agenda
Internetworking Basics
 Internetworking Model
 The OSI Reference Model
 Ethernet Networking
 Wireless Networking
 Data Encapsulation
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Possible causes of LAN traffic
congestion are
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Too many hosts in a broadcast domain
Broadcast storms
Multicasting
Low bandwidth
Adding hubs for connectivity to the network
A large amount of ARP or IPX traffic (IPX is a
Novell
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Network Segmentation
Collision domain
 Broadcast domain

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Two advantages of using routers in
your network are
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They don’t forward broadcasts by default.
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They can filter the network based on layer
3 (Network layer) information (i.e., IP
address).
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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
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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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The OSI Reference Model

The upper layers
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The lower layers
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Layer functions
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Application Layer
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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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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 services13
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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
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The 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
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The 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
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Data integrity is ensured at the Transport layer
by maintaining flow control and by allowing
users to request reliable data transport between
systems.
 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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Connection-Oriented Communication
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a call setup, or a three way handshake
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Transmitting segments with flow
control
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Windowing
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Acknowledgments
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It guarantees that the data won’t be duplicated
or lost.
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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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Transport layer reliable delivery
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The Network Layer
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The 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:
 Data
packets : routed protocol
 Route update packets : routing protocol
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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:
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Media 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,
Logical Link Control (LLC) 802.2 Responsible
for identifying Network layer protocols and then
encapsulating them.
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Switches and Bridges at the Data Link Layer
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Layer 2 switching is considered hardware-based
bridging because it uses specialized hardware
called an application-specific integrated circuit
(ASIC).
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The Physical Layer
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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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Ethernet Networking
Lecture 2-2
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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
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We 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 (100Base-TX)
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NRZI Encoding Examples (100Base-FX)
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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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Wireless Networking
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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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Data Encapsulation
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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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