Transcript Network architecture

Networks – Network Architecture
• Network architecture is specification of design
principles (including data formats and procedures) for
creating a network configuration to ensure the reliable
transfer of information
• Network architecture is represented as a set of network
protocols
• Protocol is a set of definitions and rules used for
communication between function units in different
system (in the general sense)
• Protocol is „the speech in the same language“ enabling
variable function modules to communicate each to other
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• The basic standard for network architectures is Open
Systems Interconnection Reference Model (OSI)
• The OSI Model defines internetworking in terms of a
vertical stack of seven layers.
– The upper layers (7 to 4) of the OSI model represent software
that implements network services like file transfer, mail
service, connection and remote session management and so on.
– The lower layers (3 to 1) of the OSI model implement more
primitive, hardware-oriented functions like routing, addressing,
and flow control
OSI model remains a practical framework that use many of
today's key network technologies
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Upper Layers
Lower Layers
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The layers functionality description (upper layers)
• Layer 7 (The Application layer) is the layer at which
communication partners are identified, user authentication and
privacy are considered, and any constraints on data syntax are
identified. Application layer enables clients the access to the
network services.
• Layer 6 (The Presentation layer) converts incoming and outgoing
data from one presentation format to another
• Layer 5 (The Session layer) sets up, coordinates, and terminates
conversations, exchanges, and dialogs between the applications at
each end.
• Layer 4 (The Transport layer) manages the end-to-end control
(for example, determining whether all packets have arrived) and
error checking. It ensures complete data transfer.
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The layers functionality description (lower layers)
• Layer 3 (The Network layer) handles the routing of
the data, i.e. sending packets in the right direction
toward the right destination.
• Layer 2 (The Data-link layer) provides error control
and synchronization for the physical level.
• Layer 1 (The Physical layer) conveys the bit stream
through the network as the signals. It provides the
hardware means of sending and receiving data.
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OSI Reference Model
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• In network protocols, two concepts are fundamental
– Messages
– Encapsulation
• Messages between entities consit of two parts: header and
payload.
• Data from upper layer are put into the payload.
• The header contains control information used to synchronize
with the remote peer. The header contains “instructions” that
tell the remote peer what to do with the message.
• Encapsulation is sending a data packet in one format within
a packet of another format
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TCP/IP (Transmission Control Protocol/Internet
Protocol) Architecture
• TCP/IP is the favorite communication protocol suite of
the worldwide network Internet
• TCP/IP protocol can be used also for communications via
private networks called intranets and in extranets too.
• Each computer on Internet is provided with TCP/IP
implementation operation system.
• The TCP/IP protocol implementation is the first
requirement for enabling an access to the Internet from any
computer.
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Implementation of TCP/IP architecture in the network
operating system
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• TCP/IP Protocol Suit is a four-layered protocol suite
• Relation TCP/IP to the OSI Reference Model
• Location of the important protocols inthe TCP/IP layers
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The TCP/IP protocols functionality
• Network interface provides the access to the
transmission media and the control of the data links.
• IP protocol supports communication between network
devices and provides routing facilities based on the
implementation of a global addressing scheme.
• Transport layer provides data transport services
between two end-user processes. The transport layer
includes two transport protocols:
– TCP protocol
– UDP protocol
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• Application layer provides the users access to the Internet
services
– There are many different protocols belonging to the
application layer. Some of them use the TCP transport
service and others use the UDP transport service
– Most of application protocols are based on the
client/server communication model.
– The client/server model of communication is that, in
which a one computer (a client) requests and is provided
with a service (such as sending a Web page) by another
computer (by a server).
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Examples of user application layer protocols, which
enable us to use the Internet services
• The World Wide Web's Hypertext Transfer Protocol (HTTP)
enabling users access to WWW information system
• The File Transfer Protocol (FTP) for files transfer from one file
system to another one
• The Telnet Protocol which lets users to logon to remote
computers
• The Simple Mail Transfer Protocol (SMTP) supporting
electronic mail service
• The Internet Message Access Protocol (IMAP) and Post Office
Protocol (POP) enabling users access to mailboxes from remote
machines
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The addressing scheme implemented in TCP/IP
• IP addressing schema allows for over a billion devices
to be uniquely identified and contacted across a network
• IP address is a 32-bit number that identifies both unique
network number and a host number, which is unique within the
network (123.56.118.1, 195.178.82.112……)
• Since networks vary in size, there are 3 different address formats
or classes
– Class A – for very large networks (up to 16 M nodes)
– Class B – for large networks (up to 65 k nodes)
– Class C – for middle to small networks (up to 250 nodes)
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Internet Domain Name System
• The numerical IP address is usually represented by a
name or series of names called the domain name
• A domain name locates an organization or other
entity on the Internet. For example, the domain name
akela.mendelu.cz locates an Internet address for
"mendelu.cz" and a particular host server named
„akela" at Internet point 195.113.194.135
• All domain names binding to IP addresses create
hierarchical administrative name space supporting
Internet domain name service (DNS)
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• Domain names need to be converted to IP
addresses, as this is required by lower layer
protocols (IP protocol).
• The conversion of domain names to IP addresses
is performed by function implementing DNS
(Domain Name System) protocol.
• Since an implementation of the DNS protocol is
built into every network application program, the
conversion is fully transparent to end users.
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Routing
• Routing is the process of moving information across an
Internet from the source to destination. Along the way, at
least one intermediate device is typically encountered.
Such a device is called a router
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Router
• Router is a device, which connects two physically different
segments of the particular network or two or more different
networks.
• Router is usually a specific device.
• If a router joins n different networks, it has n different
network interfaces and forwards data packets between them.
• A router takes routing information from the routing table.
It has entry for each identified route within common
network.
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• Routers (Cisco Systems, Inc.)
• Router logo (Cisco Systems, Inc.)
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• Routing path – „the best path“ from source to
destination
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Routing in the context of the OSI Model
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