The document discusses the OSI reference model, which was introduced in the late 1970s by the International Organization for Standardization (ISO) to establish a standard for network communication. The OSI model defines seven layers of network functionality, including the physical, data link, network, transport, session, presentation, and application layers. Each layer has a specific role, with lower layers focusing on physical connectivity and higher layers dealing with process-to-process communication between applications. The document also covers addressing schemes like MAC addresses, IP addresses, and port addresses used in TCP/IP networks.
2. We use the concept of layers in our daily life. As an
example, let us consider two friends who communicate
through postal mail. The process of sending a letter to a
friend would be complex if there were no services available
from the post office.
Established in 1947, the International Standards
Organization (ISO) is a multinational body dedicated to
worldwide agreement on international standards. An ISO
standard that covers all aspects of network communications
is the Open Systems Interconnection (OSI) model. It was
first introduced in the late 1970s.
Layered Tasks of the OSI Model
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8. Layer1: Physical Layer
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-Physical Characteristics of interfaces and medium
-Representation of bits: Stream of bits 0s and 1s
-Data Rate
-Synchronization of bits
-Line configuration: Connection
-Physical topology
-Transmission mode: Simplex,Half/Full duplex
9. Layer2: Data Link Layer
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-Framing: convert from up layer to frame
-Physical addressing: MAC (Media Access Control)
-Flow/Error/Access control: Make error free to upper
10. Layer3: Network Layer
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Responsible for the source to destination delivery of a packet.
-Routing
-Logical addressing: IP Address
11. Layer4: Transport Layer
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Responsible for process-to-process delivery of the entire
message:
-Flow/Error control
-Connection control: Connectionless and connection
oriented
18. Physical Address: MAC Address
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Most local-area networks use a 48-bit (6-byte) physical
address written as 12 hexadecimal digits; every byte (2
hexadecimal digits) is separated by a colon, as shown
below:
07:01:02:01:2C:4B
A 6-byte (12 hexadecimal digits) physical address.
19. Logical Address: IP Address
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An IPv4/IPv6 addresses is a 32/128-bit address that
uniquely and universally defines the connection of a device
(for example, a computer or a router) to the Internet. Figure
below is the sample of IPv4 address.
20. Port Address
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A port address is a 16-bit address represented by one
decimal number as shown.
753
A 16-bit port address represented
as one single number.