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DATA COMMUNICATION
02--Protocol Architecture
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The Need For A Protocol Architecture
Data exchange can involve complex
procedures, e.g. file transfer
Better if task is broken into subtasks
Implemented separately in stack
• Each layer provides functions needed to perform
communications for layers above
• Using functions provided by layers below
Peer layers communicate with a protocol
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Key Elements of a Protocol
Syntax: Concerns the format of the data
blocks
Semantics: Includes control information for
coordination and error handling
Timing: Includes speed matching and
sequencing
The TCP/IP Protocol Architecture
Developed by the Defense Advanced Research
Projects Agency (DARPA)
For ARPANET packet-switched network
Used by global internet
protocol suite consists of a large collection of
protocols that have been issued as Internet
standards by the Internet Activities Board
(IAB)
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Simplified Network Architecture
TCP/IP Layers
Application layer
Host-to-host, or transport layer
Internet layer
Network access layer
Physical layer
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Physical Layer
Concerned with physical interface between a
data transmission device (e.g., workstation,
computer) and a transmission medium or
network
Concerned with issues like
• characteristics of the transmission medium
• nature of the signals
• the data rate, and related matters
Network Access Layer
exchange of data between an end system
(server, workstation, etc.) and the network to
which it is attached
Concerned with issues like
• Destination address provision
• Invoking specific services like priority
• Access to and routing data across a network lik
between two attached systems
Allows layers above to ignore link specifics
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Internet Layer (IP)
Routing functions across multiple networks
For systems attached to different networks
Using IP protocol
Implemented in end systems and routers
Routers connect two networks and relays data
between them
Transport Layer(TCP)
Common layer shared by all applications
Provides reliable delivery of data
In same order as sent
Commonly uses TCP
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Application Layer
Provides support for user applications
Need a separate module for each type of
application
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Operation of TCP and IP
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Addressing Requirements
Two levels of addressing required
Each host on a subnet needs a unique global
network address: its IP address
Each application on a (multi-tasking) host
needs a unique address with the host : a port
address
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Operation of TCP/IP
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Transmission Control Protocol(TCP)
Usual transport layer is TCP
Provides a reliable connection for transfer of
data between applications
A TCP segment is a basic protocol unit
TCP tracks segments between entities for
duration of each connection
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TCP Header
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User Datagram Protocol(UDP)
An alternative to TCP
No guaranteed delivery
No preservation of sequence
No protection against duplication
Minimum overload
Adds port addressing to IP
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UDP Header
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IP Header
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IPv6 Header
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TCP/IP Applications
Have a number of standards TCP/IP
application such as
• Simple Mail Transfer Protocol(SMTP)
• File Transfer Protocol(FTP)
• Telnet
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Some TCP/IP Protocols
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OSI
Open Systems Interconnection
Developed by the International organization
(ISO)
Has seven layers
Is a theoretical system delivered too late
TCP/IP is the de facto standard
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OSI Layers
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OSI vs TCP/IP
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Standardized Protocol Architectures
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Layer Specific Standards
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Service Primitives and Parameters
Define services
between adjacent
layers using:
Primitives to specify
function performed
Parameters to pass data
and control information
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Primitive Types
REQUEST A primitive issued by a service user to invoke some service to
pass the parameters needed to specify fully the requested
service
INDICATION A primitive issued by a service provider either to: indicate that
a procedure has been invoked by the peer service user on the
connection and to provide the associated parameters, or notify
the service users of a provider- initiated action
RESPONSE A primitive issued by a service user to acknowledge or
complete some procedure previously invoked by an indication
to that user
CONFIRM A primitive issued by a service provider to acknowledge or
complete some procedure previously invoked by a request by
the service user
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Traditional vs Multimedia Applications
Traditional Internet dominated by information
retrieval applications
• Typically using text and image transfer
• Eg. Email, file transfer ,web
See increasing growth in multimedia
applications
• Involving massive amounts of data
• Such as streaming audio and video
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