chapter 3 protocols and the tcp/ip suite - networ-based...
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Chapter 3Protocols and the TCP/IP Suite
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3.1 The Need for a Protocol Architecture
need for a standard communication tasks by layers architecture peer protocol: a set of rules or conventions to
exchange data syntax semantics timing
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3.2 TCP/IP Protocol Architecture
architecture for ARPANET packet switching network funded by DARPA Internet standards by Internet Activities
Board (IAB)
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TCP/IP Layers three agents of communication
applications: distributed applications, e.g., e-mail and file transfer
computers: supports multiple applications at a time
networks
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communication tasks organized into five layers physical layer network access layer internet layer host-to-host (or transport) layer application layer
physical layer physical interface between computer and
network
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network access layer data exchange between a computer (end
system) and the network from source to destination computer within
a network requires destination address and possibly
priority internet layer
transfer of data over multiple interconnected networks
routing across multiple networks internet protocol (IP)
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host-to-host or transport layer independent of the network type and the
application type collection of functions for reliable data exchange assurance of delivery, correctness, and correct
order transmission control protocol (TCP)
application layer to support the various user applications a separate module needed for each different
type of application
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Operations of TCP and IP network comprised of subnetworks
network access protocol: sending data within a subnetwork or to routers
IP: moving data to a destination via routers TCP: reliable data transfer from source to
destination
two levels of addressing
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TCP segment segmented user data + control information
(TCP header: port, sequence number, checksum)
IP datagram TCP segment + control information (IP header:
host address) packet or frame
IP datagram + control information (network header: subnetwork address, priority)
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router stripping network header checking destination host address sending it as another datagram
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TCP/IP Applications simple mail transfer protocol (SMTP) file transfer protocol (FTP)
two connections: control and data transfer control connection for user access
TELNET remote logon
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3.3 The OSI Model
International Standardization Organization (ISO) Open Systems Interconnection (OSI)
reference model open denotes the ability of connecting two
systems conforming to the standards
Overall Architecture layering issues of layering
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OSI model as a framework for standardization
TCP/IP as a de facto standard
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Physical Layer: physical interface between devices and
the rules for passing bits from one to another RS-232-C
Data Link Layer: make the physical link reliable
provide means to activate, maintain, and deactivate the link
error detection and control HDLC (High-level Data Link Control)
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Network Layer: transfer of information between end
systems across some type of network relieving higher layers of the need to know
what types of switching and data transmission are used
specification of destination address and request for network facilities such as priority
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a direct point-to-point link between stations
stations connected across a single network such as a circuit-switching or packet-switching network
X.25 covering the lower three layers
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Transport Layer: reliable information exchange between
end systems error-free, in sequence, no loss, no
duplication duplication of layer 2
size and complexity depends on the type of the layer 3
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Session Layer: controlling dialogue between two end
systems little or no need for session layer service in
many cases dialogue discipline
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Presentation Layer: define the format of the data to be
exchanged data compression data encryption
Application Layer: provide means for applications to
access the OSI environment management functions support for distributed applications general-purpose applications
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3.4 Internetworking
internet
interconnected set of different subnetworks
the Internet
intranet
end system (ES)
intermediate system (IS)
bridge: interconnection at OSI layer 2
router: interconnection at OSI layer 3
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