Unit 2 cnd_22634_pranoti doke

TCP/IP
Protocol
Suite
Prof. Pranoti R. Doke
Presented by,

2
Computer Networks
Unit 2
Protocols and the TCP/IP
Protocol Suite

3
Protocols
• Cooperative action is necessary
– computer networking is not only to exchange bytes
– huge system with several utilities and functions. For examples
• error detection
• Encryption
• Routing etc.
• For proper communication, entities in different systems
must speak the same language
– there must be mutually acceptable conventions and rules
about the content, timing and underlying mechanisms
• Those conventions and associated rules are referred
as “PROTOCOLS”

4
Protocol Architecture
• Task of data transfer is broken up into some
modules
– Why?
– How do these modules interact?
• For example, file transfer could use three
modules
– File transfer application
– Communication service module
– Network access module

5
A Real World Example to Protocol
Architecture philosopher-translator-
secretary architecture
Issues:
• peer-to-peer
protocols are
independent of
each other
–for example,
secretaries may
change the
comm. medium to
email
–or the translators
may agree on
using another
common
language
•Each layer adds
a header

6
Simplified File Transfer
Architecture
File Transfer Application Layer: Application specific commands,
passwords and the actual file(s) – high level data
Communications Service Module: reliable transfer of those data – error
detection, ordered delivery of data packets, etc.
Network Module: actual transfer of data and dealing with the network – if
the network changes, only this module is affected, not the whole system

7
General protocol architecture
principles that we have seen
so far
• Layered structure
– Protocol stack
• Each layer provides services to upper layer; expect services
from lower one
– Layer interfaces should be well-defined
• Peer entities communicate using their own protocol
– peer-to-peer protocols
– independent of protocols at other layers
– if one protocol changes, other protocols should not
get affected

Introduction TCP/IP
• The Internet Protocol Suite (commonly known as
TCP/IP) is the set of communications protocols used for
the Internet and other similar networks.
• It is named from two of the most important protocols in
it:
• Transmission Control Protocol (TCP) and
• Internet Protocol (IP), which were the first two
networking protocols defined in this standard.

TCP/IP and OSI Model

11
A General Three Layer
Model
• Generalize the previous example for a generic application
– we can have different applications (e-mail, file transfer, …)
• Network Access Layer
• Transport Layer
• Application Layer

APPLICATION LAYER
• This layer is comparable to the application,
presentation, and session layers of the OSI model all
combined into one.
• It provides a way for applications to have access to
networked services.
• It is widely-known layer for the exchange of user
information

-- The Hypertext Transfer Protocol (HTTP) is used to
transfer files that make up the Web pages of the World
Wide Web.
-- The File Transfer Protocol (FTP) is used for
interactive file transfer.
-- The Simple Mail Transfer Protocol (SMTP) is used
for the transfer of mail messages and attachments.
APPLICATION LAYER

• Presentation Layer does Encryption-Decryption and
Compression-Decompression of Data.
• This layer allows a process to add checkpoints which are
considered as synchronization points into stream of data.
APPLICATION LAYER

TRANSPORT LAYER
• This layer acts as the delivery service used by the
application layer.
• Two protocols used are TCP and UDP.
• The choice is made based on the application's
transmission reliability requirements.
• The transport layer also handles all error detection and
recovery.

-- It uses checksums, acknowledgements, and timeouts
to control transmissions and end to end verification.
-- Unlike the OSI model, TCP/IP treats reliability as an
end-to-end problem
-- TCP provides a one-to-one, connection-oriented,
reliable communications service.
-- UDP provides a one-to-one or one-to-many,
connectionless, unreliable communications service.
TRANSPORT LAYER

• A message is divided into segments; each segment
contains sequence number, which enables this layer in
reassembling the message.
TRANSPORT LAYER

• Message is reassembled
correctly upon arrival at the destination and replaces
packets which were lost in transmission.
Connection Control : It includes 2 types :
1. Connectionless Transport Layer :Each segment is
considered as an independent packet and delivered to
the transport layer at the destination machine.
2. Connection Oriented Transport Layer :Before
delivering packets, connection is made with transport
layer at the destination machine.
TRANSPORT LAYER

NETWORK LAYER
• This layer is also known as Internet Layer.
• The main purpose of this layer is to organize or handle
the movement of data on network.
• By movement of data, we generally mean routing of
data over the network.
• This layer is responsible for addressing, packaging,
and routing functions.

• The core protocols of the Internet layer are IP, ARP,
ICMP, and IGMP.
• The Internet Protocol (IP) is a routable protocol
responsible for IP addressing, routing, and the
fragmentation and reassembly of packets.
• The Address Resolution Protocol (ARP) is responsible for
the resolution of the Internet layer address to the Network
Interface layer address such as a hardware address.
NETWORK LAYER

• The Internet Control Message Protocol (ICMP) is
responsible for providing diagnostic functions and
reporting errors due to the unsuccessful delivery of IP
packets.
• The Internet Group Management Protocol (IGMP) is
responsible for the management of IP multicast
groups.
NETWORK LAYER

• It translates logical network address into physical
address. Concerned with circuit, message or packet
switching.
• Routers and gateways operate in the network layer.

DATA LINK LAYER
• Data link layer is most reliable node to node delivery
of data.
• It forms frames from the packets that are received
from network layer and gives it to physical layer.
• It also synchronizes the information which is to be
transmitted over the data. Error controlling is easily
done.

• Protocols of this layer determine which of the devices
has control over the link at any given time, when two
or more devices are connected to the same link.

• Error control is achieved by adding a trailer at the end of
the frame.
• Duplication of frames are also prevented by using this
mechanism.
• Frames are the streams of bits received from the network
layer into manageable data units.
• This division of stream of bits is done by Data Link
Layer.
DATA LINK LAYER

Switch and Bridge are used in this layer
DATA LINK LAYER

PHYSICAL LAYER
Physical layer is the lowest layer of all. It is
responsible for sending bits from one computer to
another.
This layer is not concerned with the meaning of the
bits and deals with the physical connection
This layer defines electrical and physical details
represented as 0 or a 1.

• This layer defines the rate of transmission which
is the number of bits per second.
• It deals with the synchronization of the
transmitter and receiver. The sender and receiver are
synchronized at bit level.
• Devices must be connected using the following
topologies: Mesh, Star, Ring and Bus.
PHYSICAL LAYER

Physical Layer defines the direction of transmission
between two devices: Simplex, Half Duplex, Full
Duplex
PHYSICAL LAYER

• Deals with baseband and broadband
transmission.
• Hubs and Repeater are used in this layer
PHYSICAL LAYER

OSI Model
• The OSI reference model
• Services in the OSI model

• OSI Reference Model - internationally
standardised network architecture.
• OSI = Open Systems Interconnection:
deals with open systems, i.e. systems open
for communications with other systems.
• Specified in ISO 7498.
• Model has 7 layers.
OSI Reference Model

• Layers 1-4 relate to
communications
technology.
• Layers 5-7 relate to user
applications.
7-Layer OSI Model
Layer 7
Layer 6
Layer 5
Layer 4
Layer 3
Layer 2
Layer 1
Application Layer
Presentation Layer
Session Layer
Transport Layer
Network Layer
Data Link Layer
Physical Layer Communications subnet boundary

• Level at which applications access network
services.
– Represents services that directly support software
applications for file transfers, database access, and
electronic mail etc.
Layer 7: Application Layer

• Related to representation of transmitted data
– Translates different data representations from the
Application layer into uniform standard format
• Providing services for secure efficient data
transmission
– e.g. data encryption, and data compression.
Layer 6: Presentation Layer

• Allows two applications on different computers to
establish, use, and end a session.
– e.g. file transfer, remote login
• Establishes dialog control
– Regulates which side transmits, plus when and how long it
transmits.
• Performs token management and
synchronization.
Layer 5: Session Layer

• Manages transmission packets
– Repackages long messages when necessary into
small packets for transmission
– Reassembles packets in correct order to get the
original message.
• Handles error recognition and recovery.
– Transport layer at receiving acknowledges packet
delivery.
– Resends missing packets
Layer 4: Transport Layer

• Manages addressing/routing of data within the subnet
– Addresses messages and translates logical addresses and names into
physical addresses.
– Determines the route from the source to the destination computer
– Manages traffic problems, such as switching, routing, and controlling
the congestion of data packets.
• Routing can be:
– Based on static tables
– determined at start of each session
– Individually determined for each packet, reflecting the current network
load.
Layer 3: Network Layer

• Packages raw bits from the Physical layer into
frames (logical, structured packets for data).
• Provides reliable transmission of frames
• It waits for an acknowledgment from the receiving
computer.
• Retransmits frames for which acknowledgement
not received
Layer 2: Data Link Layer

• Transmits bits from one computer to another
• Regulates the transmission of a stream of bits over a physical
medium.
• Defines how the cable is attached to the network adapter and
what transmission technique is used to send data over the cable.
Deals with issues like
– The definition of 0 and 1, e.g. how many volts
represents a 1, and how long a bit lasts?
– Whether the channel is simplex or duplex?
– How many pins a connector has, and what the function
of each pin is?
Layer 1: Physical Layer

• Explicit Presentation
and session layers
missing in Internet
Protocols
• Data Link and
Network Layers
redesigned
Internet Protocols vs OSI
Application
Presentation
Session
Transport
Network
Data Link
Physical
Application
TCP
IP
Network Interface
Hardware

• In OSI model, each layer provide services
to layer above, and ‘consumes’ services
provided by layer below.
• Active elements in a layer called entities.
• Entities in same layer in different machines
called peer entities.
Services in the OSI Model

• Layer N provides service to layer N+1
Layering Principles
(N+1) Entity
Service User
(N) Entity
Service Provider
(N+1) Entity
Service User
(N) Entity
Service Provider
Layer N Service
Access Point (SAP)
Layer N protocol
N+1
PDU
Layer N+1 protocol
SDU
PDU - Protocol Data Unit
SDU - Service Data Unit
N
PDU
N
PDU

• Layers can offer connection-oriented or
connectionless services.
• Connection-oriented like telephone system.
• Connectionless like postal system.
• Each service has an associated Quality-of-
service (e.g. reliable or unreliable).
Connections

• Reliable services never lose/corrupt data.
• Reliable service costs more.
• Typical application for reliable service is file
transfer.
• Typical application not needing reliable
service is voice traffic.
• Not all applications need connections.
Reliability

• Service = set of primitives provided by one
layer to layer above.
• Service defines what layer can do (but not
how it does it).
• Protocol = set of rules governing data
communication between peer entities, i.e.
format and meaning of frames/packets.
• Service/protocol decoupling very important.
Topics

Unit 2 cnd_22634_pranoti doke

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