Application and Layered Architecture

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Application and layered

architecturesBTech EXTC

Trim IX

Faculty: Prof. Sonia Relan


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Unit Contents Layering architecture

The OSI Reference model.

Unified view of layers

Protocols and services

Overview of TCP/IP architecture

TCP/IP Protocol


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The interac t ion between layers in

the OSI model


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Encapsulation A packet at level 7 is encapsulated at level 6.

The whole packet then is encapsulated at level 5 and so on.


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1. Physical Layer The physical layer is responsible for movements of individual bits

from one hop (node) to the next.

It deals with the electrical and mechanical specifications of the

interface and transmission medium.

Also describes procedures and functions that physical devices

and interfaces have to perform for transmission to occur.

Physical layer concerned with the following

1. Physical characteristics of interface and medium

2. Representation of bits.

3. Data rate

4. Synchronization of bits.5. Line configuration

6. Physical topology

7. Transmission mode


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Physical layer


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2. Data Link Layer Transforms the physical layer, a raw transmission facility, to a reliable

link.

It makes the physical layer appear error free to the upper layer (n/w

layer).

The data link layer is responsible for moving frames from one hop

(node) to the next.

Responsibilities of data link layer

1. Framing

2. Physical addressing

3. Flow control

4. Error control5. Access control


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Data link layer


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Hop-to-hop delivery


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3. Network layer Responsible for source to destination delivery of packets, possibly

across multiple networks (links).

Where as the datalink layer oversees the delivery of packets only

between two systems on the same network.

If two systems are attached to different networks with connecting

devices, there is often a need of network layer to accomplish source to

destination packet delivery.

Responsibilities of N/w layer:

1. Logical addressing

2. Routing

3. Source to destination delivery


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Source-to-destination delivery


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4. Transport layer The transport layer is responsible for the delivery of a message from

one process to another. A process is an application program running on a host, whereas n/w

layer oversees source to destination delivery of individual packets.

Ensures whole message has arrived in order, overseeing both error

control and flow control.

Responsibilities of transport layer are:

1. Service point addressing

2. Segmentation and reassembly

3. Connection control

4. Flow control5. Error control


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Transport layer

R li bl t


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Reliable process-to-process

delivery of a message


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5. Session layer Service provided by the first three layers are not sufficient for

some processes. The session layer is responsible for dialog control and

synchronization.

It establishes, maintains and synchronizes the interaction among

communicating systems.

Specific responsibilities of the Session layer are as follows:

1. Dialog control

2. Synchronization


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Session layer


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6. Presentation layer Concerned with the syntax and semantics of the information

exchanged between two systems. The presentation layer is responsible for translation,

compression, and encryption.

Responsibilities of presentation layer includes:

1. Translation

2. Encryption

3. Compression


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7. Application layer


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Summary of layers


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TCP/IP PROTOCOL SUITE The layers in the TCP/IP proto co l suitedo not exact ly m atch thos e

in th e OSI model. The or ig inal TCP/IP proto col suite was defined as having four

layers: host- to-network, internet, t ranspor t, and appl icat ion.

However, when TCP/IP is compared to OSI, we can say that the

TCP/IP pro toco l su ite is made of f ive layers: physica l, data link,

network, t ranspor t, and appl icat ion.


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TCP/IP and OSI model


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R l t i h i f l d


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Relat ionsh ip o f layers and

addresses in TCP/IP


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Examp le 2.1

In Figu re 2.19 a node with physical address 10 send s a frame to a

nod e with ph ysic al address 87. The two nod es are connected by al ink (bus topology LAN). As the f igure shows, the computer wi th

phys ical address 10is the sender, and the computer with phys ical

address 87is the receiver.


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Physical address

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Application and Layered Architecture