chap 8 suppl logical
TRANSCRIPT
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A Logical Explanation
The Business/IT Highway:
How Does IT Work?
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Objectives
Analyze the layered models
Review common protocols
Logical addressing
Understand the encapsulation process
Reliability issues How does my data get to its destination?
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Part 1 Overview of theOSI Model
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Benefits ofOSI Model
Reduce complexity
Standardize interfaces
Facilitate modular engineering
Ensure interoperable technologies
Accelerate evolution
Simplify teaching and learning
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What isOSI Model ?
Open System Interconnection (OSI) model is a set of
protocols that define and standardize the datacommunications process
The OSI model is set by the International Standards
Organization (ISO)
The OSI model has the support of most major
computer and network vendors
OSI model divides the process into seven groups,
called layers which are fitted with protocol standards
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OSI Layers
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TheOSI Model
Physical Layer (L1 or Layer 1) Connections and connector types
Cables
Wireless
Fiber
Signaling standards
Voltages, attenuation, noise, etc
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OSI Layers
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OSI Layers
Data Link Layer (L2 or Layer 2)
Physical addressing MAC Framing
Network topology
Error detection
Access to media
Sub-Layers MAC and LLC
Ethernet
LAN Switches are L2 devices
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OSI Layers
Data Link LayerProtocols
SLIP Serial Line Internet Protocol PPP Point to Point Protocol
HDLC High Level data link control
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OSI Layers
Provides connectivity and path selection between two host
Provides Logical address
No error correction, best effort delivery.
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OSI Layers
Network Layer (L3 or Layer 3)
Logical addressing IP address Packets
Connection-less, best effort
Best path selection
Routers are Layer 3 devices
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OSI Layers
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OSI Layers
Transport Layer (L4 or Layer 4)
Segmentation of Data Error correction
Reliability
End-to-end communication
Windowing
TCP and UDP
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OSI Layers
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OSI Layers
Session Layer
Two way alternate vs. two way simultaneous Synchronization between applications
Some protocols: NFS & SQL
This layer is part of the TCP/IP models Application layer
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OSI Layers
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OSI Layers
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OSI Layers
Application Layer (L7 or Layer 7)
Closest to the user This is NOT the application you interact with
This is the underlying protocol of the application
HTML for web browsers
SMTP and POP3 for email
This layer is part of the TCP/IP models Application layer
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Peer-to-Peer Communication
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Compare:OSI and TCP/IP models
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PART 2 The Details
Lets look at these layers a bit closer but lets
turn it around.
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Layer 7 Application Layer
Identifying and establishing the availability of
intended communication partners Synchronizing cooperating applications
Establishing agreement on procedures for
error recovery
Controlling data integrity
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Layer 7 Application Layer
Common Application layer protocols
HTTP Telnet
FTP
SNMP
DNS FTP and TFTP
SMTP
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DNS
The Domain Name System (DNS) is a systemused for translating names into IP addresses.
There are more than 200 top-level domainson the Internet
Uses port 53
.us United States.uk United Kingdom
.edu educational sites
.com commercial sites
.gov government sites.org non-profit sites
.net network service
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FTP and TFTP
FTP is a reliable, connection-oriented
service that uses TCP to transfer filesbetween systems that support FTP. Uses ports 20 and 21
TFTP is a connectionless service that uses
User DatagramP
rotocol (UDP
). TFTP is designed to be small and easy to
implement.
Use port 69
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HTTP
Hypertext TransferProtocol
Uses port 80
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SMTP
E-mail servers communicate with each otherusing the Simple Mail Transport Protocol(SMTP) to send and receive mail (POP3).
Uses port 25, 110
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SNMP
The Simple Network Management Protocol (SNMP) is anapplication layer protocol that facilitates the exchange of
management information between network devices.
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Telnet
Telnet client software provides the ability to log
in to a remote Internet host that is running aTelnet server application and then to executecommands from the command line.
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Layer 6 Presentation Layer
Responsible for
Data format - ASCII, jpeg, mp3, etc. Compression
Encryption
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Layer 5 Session Layer
Establish, maintain and terminate sessions
between applications. Dialog control - the session layer decides whether
to use two-way simultaneous communication or
two-way alternate communication.
Dialog separation - orderly initiate, terminate, andmanage transactions
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Layer 4 Transport Layer
Segments data
Adds a logical identifier (port number) Provides for reliability by ensuring segments
delivered are acknowledged
Provides for retransmission of segments no
acknowledged Reassembles segments at destination
Provides for congestion avoidance andcontrol
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Layer 4 Transport Layer
Primary Transport LayerProtocols
TCP Connection oriented
Reliable
UDP
Connection-less
Unreliable
Best effort like IP
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Layer 4 Transport Layer
Both TCP and UDP use port (socket) numbers to passinformation to the upper layers.
Port numbers identify specific
Application layerprotocols.
Numbers below 1024 are considered well-knownports numbers.
Numbers above 1024 are dynamically assignedports numbers.
Registered port numbers are those registered forvendor-specific applications. Most of these areabove 1024.
Well known ports: 80 = HTTP, 23 = telnet
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Layer 3 Network Layer
Layer 3 is responsible for:
Logical addressing (IP and others) Routing
Path selection
Packet switching
Encapsulation of Segments intoPA
CKETS
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Layer 3 Network Layer
Internet Protocol
IP is a connectionless, best-effort protocol Unreliable
It relies on TCP for reliability
It provides the ability for a logical address
Network (and subnetwork) Node
A mask is used to distinguish between net & node
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Layer 3 Network Layer
What is an IP address?
Logical address Two parts: network id and host id
32 bit address
Written in dotted decimal notation
4 sets of 8 bits written as decimal numbers192.168.1.1
205.200.3.24
10.3.5.254
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Layer 3 Network Layer
Private and reserved IP addresses
Some addresses are reserved for specialpurposes.
Some identify the Network ID and some Identify the
broadcast address for the entire network.
Some are considered Private and do not traverse the
internet
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Layer 3 Network Layer
Private and reserved IP addresses (cont.)
Some are for multicasting 224.0.0.0 through 239.255.255.255
Some are for testing purposes
127.0.0.0
Some are link-local
169.254.0.0 Some are reserved for no good reason
240.0.0.0 255.255.255.255
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Layer 3 Network Layer
IP version 6
Do I need to know this? Be aware of it. An IPv6 address is a 128 bit address
Written in hexadecimal notation2001:1234:0000:fb5d:0000:0000:0abc:def0/64
Can be shortened to:2001:1234:0:fb5d::abc:def0/64
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Layer 3 Network Layer
Ah.the IPPACKET
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Layer 3 Network Layer
The Router
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Layer 3 Network Layer
The Router a network layer device
Used to connect different logical networks Determines best path (routing protocols)
Switches packets (routed protocols) from
incoming interface to outgoing interfaces
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Layer 3 Network Layer
The router is responsible for determining bets path
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Layer 2 Data Link
LLC Logical Link Control
LLC is specified in IEEE 802.2 It is the upper sub-layer of layer 2.
It provides a logical service to the Network layer
It is independent of topology
It is independent of technology
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Layer 2 Data Link
MAC Media Access Control
This is the lower sub-layer of Layer 2 Topology dependent
Media dependent
Technology dependent
Physical addressing (naming) Encapsulating Packets into FRAMES
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Layer 2 Data Link
The LAN switch a layer 2 device*
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L3 vs. L2
Comparing layer 3 and layer 2 devices
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Layer 1
Layer 1 (We spoke in detail about layer one in the Lets Get Physical workshop)
Bits and signaling Cabling
Connectors and connection standards
Electricity
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Putting it together
Each layer accepts whatever is passed into it
from the upper layer. It then encapsulates that information.
Each layers encapsulation has a name, this
is called a Protocol Data Unit orPDU.
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Putting it together
Data flow example
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Summary
We use layers to simplify learning andunderstanding of data flow
Data is encapsulated into packets thenframes before being transmitted as bits
Routing protocols are used to determine thebest path to a destination
TCP/IP is the protocol suite of the internet IP is connectionless and unreliable
TCP provides connection-oriented service andreliability