Transcript Standards

Part E:
Standards
Layered Standards Architectures
TCP, IP, and TCP/IP
Other Architectures
Standards
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Standards are rules of operation that most or all
vendors follow

Open standards are created and owned by public
standards organizations
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No single vendor controls these standards
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Standards Are Layered
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For Internet Access to a Webserver, standards are
set at five layers
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Application
Transport
Internet
Data Link
Physical
Together, these standards provide all that is needed
for application programs on different hosts on
different networks to work together
Internet Standards
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Application Layer Standards
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Standards at the application layer specify how two
application programs communicate
For example, browser on user PC and webserver
application program on webserver
Webserver
Application
Browser
Program
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Internet Standards
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HTTP (HyperText Transfer Protocol)
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World Wide Web standard for browser-webserver
application program exchanges
Other applications (E-mail, etc.) have different
application standards
Webserver
Application
Program
Browser
HTTP
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Internet Standards
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Transport Layer Protocols
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Standards at the transport layer specify how two host
computers will work together, even if they are of
different platform types (PCs, workstations,
mainframes, and so forth)
For instance, PC and non-PC webserver
PC
PC or
Other Computer
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Internet Standards
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The Transport Layer Gives Platform
Independence
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Two computers do not have to be of the same platform
type
A PC user does not even know what kind of
computer the webserver is
PC
?
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Internet Standards
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HTTP Requires the Use of the TCP Transport
Standard
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Transmission Control Protocol
TCP messages are called TCP segments
TCP
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Internet Standards
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Internet Layer Protocols
– Standards at the internet layer specify how hosts and
routers will act to route packets end to end, from the
source host to the destination host, across many single
networks (subnets) connected by routers
Route
Host
Host
Single Network
(Subnet)
Internet Standards
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The Internet Protocol (IP) is the Main Protocol for
Routing Packets Across the Internet
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The IP in “TCP/IP”
IP messages are called packets
All internet layer messages are called packets
Packet
IP
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Internet Standards
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Subnets
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Single networks (LANs, WANs, point-to-point link) on
the Internet
A packet will pass through several subnets along its
route across the Internet
Subnet
Subnet
Subnet
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Internet Standards
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Different Subnets Can Have Different Subnet
Protocols
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IP at the internet layer routes across different protocols
at the subnet layer
LAN Subnet
Protocol 3
Point-to-Point Subnet
Protocol 1
WAN Subnet
Protocol 2
Subnets Standards
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Subnets are Single Networks on the Internet
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Subnet Standards Divided into Two Layers
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Physical layer standards govern the transmission of
individual bits within a subnet
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Data Link layer standards govern the transmission of
messages within a subnet
 Organize
individual bits into structured messages
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Internet Standards
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Data Link Layer Standards
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Standards at the data link layer specify how to transmit
messages within a single network
Messages at the data link layer are called frames
Frame
10010001001
Data Link
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Internet Standards
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Data Link Layer Standards
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For accessing the Internet from home ...
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Point-to-Point Protocol (PPP) dominates
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Only used between home and ISP!
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Other subnets connecting routers are likely to use
different subnet protocols!
?
PPP
ISP
Internet Standards
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Physical Layer Standards
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While the data link layer is concerned with the
organization and transmission of organized messages,
standards at the physical layer specify how to transmit
single bits one at a time
Work bit by bit; no frame organization
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Internet Standards
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Physical Layer Standards in Internet Access from
Home
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Telephone jack (RJ11)
Telephone wire
Serial port connection to external modem
Modem
Serial
Port
External Modem
Telephone
Wire
Wall Jack
Internet Standards
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Subnet Versus Internet Layer Standards
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Internet layer provides routing across multiple subnets
Subnet layer standards (data link and physical) provide
for transmission within a single network
Internet
Layer
Subnet Layer
Internet Standards
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Analogy for Subnet versus Internet
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Take a vacation
Route from beginning to end (like internet layer)
For different parts, may travel by car, airplane, or boat
(like subnet layer)
Internet
Layer
Subnet Layer
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Standards Organizations and Architectures
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Architecture is a Design for Standards Creation
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Specifies what types of standards are needed
(application, transport, etc.)
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After architecture is designed, individual standards of
each type are created
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Analogy: architecture of house specifies what rooms
will be needed and their relationships.
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After architecture is settled, individual rooms are
designed
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Standards Organizations and Architectures
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TCP/IP Standards
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Created by the Internet Engineering Task Force (IETF)
Named after its two most widely known standards, TCP
and IP
 TCP/IP is the architecture, while TCP and IP are
individual standards
 However, these are not its only standards, even at
the transport and internet layers
IETF standards dominate in corporations at the
application, transport, and internet layers
 However, application, transport, and internet
standards from other architectures are still used
Standards Organizations and Architectures
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OSI Standards
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Reference Model of Open Systems Interconnection
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Created by the International Telecommunications
Union-Telecommunications Standards Sector (ITU-T)
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And the International Organization for Standardization
(ISO)
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OSI standards dominate the data link and physical
layers
 Other
architectures specify the use of OSI standards
at these layers
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Internet Standards
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5-Layer Hybrid TCP/IP-OSI Architecture
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Most widely used architecture in organizations today
Used on the Internet
Application
TCP/IP
Transport
TCP/IP
Internet
TCP/IP
Data Link
OSI
Physical
OSI
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Internet Standards
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Recap: Accessing the WWW from Home
App
HTTP
App
Trans
TCP
Trans
Int
IP
Int
IP
Int
DL
PPP
DL
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DL
Phy
Modem
Phy
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Phy
User PC
Router
Webserver
TCP/IP versus OSI
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Box
Lowest Four Layers are Comparable in
Functionality
TCP/IP
OSI
Application
Application
Presentation
Session
Transport
Network
Data Link
Physical
Transport
Internet
Data Link (use OSI)
Physical (use OSI)
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OSI Divides the Application Layer
Box
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OSI Session Layer
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Sets up a connection between two application programs
on different machines
Manage streams of transactions (session); if there is a
break, can resume at the last roll-back point
Transactions
OSI Divides the Application Layer
Box
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OSI Presentation Layer
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Handles presentation differences between the two
machines (how data are stored and represented)
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Two presentation layer processes select and use a
common format for exchanging data
Application Data
Exchange in
Common Format
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OSI Divides the Application Layer
Box
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OSI Application Layer
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Governs application-to-application communication
freed from concerns about presentation format and
transaction management
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