3.Communication Protocol

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COMMUNICATION

PROTOCOL


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Function of Protocol in Network

Communication

The importance of protocols and how they areused to facilitate communication over data

networks A protocol is a set of predetermined rules

A standard is a process or protocol that has been endorsed by thenetworking industry and ratified by a standards organization


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The Role of Protocol

Networking protocols suites describe processessuch as:

The format or structure of the message

The process by which networking devices shareinformation about pathways with other networks

How and when error and system messages arepassed between devices

The setup and termination of data transfersessions


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Benefit Of Using Layered Model

To visualize the interaction between various protocols, it is commonto use a layered model.

There are benefits to using a layered model to describe networkprotocols and operations. Using a layered model:

Assists in protocol design, because protocols that operate at a specificlayer have defined information that they act upon and a definedinterface to the layers above and below.

Fosters competition because products from different vendors can worktogether.

Prevents technology or capability changes in one layer from affectingother layers above and below.

Provides a common language to describe networking functions andcapabilities.


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Protocol and Reference Model

There are two basic types of networking

models:

protocol models

reference models.


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Protocol Model

A protocol model provides a model that closelymatches the structure of a particular protocolsuite.

The hierarchical set of related protocols in asuite typically represents all the functionalityrequired to interface the human network with thedata network.

The TCP/IP model is a protocol model becauseit describes the functions that occur at eachlayer of protocols within the TCP/IP suite.


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Reference Model

A reference model provides a common reference formaintaining consistency within all types of networkprotocols and services.

A reference model is not intended to be animplementation specification or to provide a sufficientlevel of detail to define precisely the services of thenetwork architecture.

The primary purpose of a reference model is to aid inclearer understanding of the functions and processinvolved.

The Open Systems Interconnection (OSI) model is themost widely known internetwork reference model. It isused for data network design, operation specifications,and troubleshooting.


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TCP/IP and OSI models are the primary modelsused when discussing network functionality,designers of network protocols, services, ordevices can create their own models torepresent their products.

Ultimately, designers are required tocommunicate to the industry by relating theirproduct or service to either the OSI model or theTCP/IP model, or to both.


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OSI MODEL

Initially the OSI model was designed by the

International Organization for Standardization

(ISO) to provide a framework on which to build asuite of open systems protocols.

The vision was that this set of protocols would

be used to develop an international network that

would not be dependent on proprietary systems.


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Model Seven Layer OSI

Wire (Network Cable)

Application Program

Layer 7

Layer 6

Layer 5

Layer 4

Layer 3

Layer 2

Layer 1

Application Layer

Presentation Layer

Session Layer

Transport Layer

Network Layer

Datalink Layer

Physical Layer Berhub dg sinyal elektrik

Menyediakan koneksi point-to-point handal

Koneksi/pemgiriman paket ke tujuan

Menyediakan koneksi end-to-end

Manage koneksi end-to-end

Data filters (compression, encryption)

Interface ke program user

signals

Tujuan

NIC


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Layer 1: Physical Layer

Fungsi Utama: Berhubungan dg sinyal elektrik

Contoh: Manchester Signal Encoding

NRZI Signal Encoding

Bipolar-AMI Signal Encoding

Mendefinisikan bagaimana sinyal direpresentasikan

Interpretasi sinyal elektrik, representasikan sbg 1 atau 0



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Layer 2: Data Link Layer

Deteksi dan koreksi error sinyal, jika ada

Fungsi Utama:

Meneruskan/Forward sinyal yg diterima ke network layer

Jika error tdk dp dikoreksi, memberikan error warning ke network layer

Menyediakan Media Access Control (MAC)

- Utk shared network, kontrol siapa yg dp menggunakan network

Contoh penggunaan bersama Network:

Ring Bus

Star (=hub)



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Layer 3: Network Layer

Fungsi Utama:

Best effort delivery service

- Translasi address

- Meroutekan paket dari sumber ke tujuan



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Layer 4: Transport Layer

Fungsi Utama:

Deteksi dan koreksi error paket (error control) utk E2E

Melaksanakan flow control

- Jikapenerima ingin slow down, mengurang laju transmisi TX

- Jika network congesti, mengurang laju transmisi

congestion control

Layer 5: Session Layer

Fungsi Utama:

Establish/Manage/Delete koneksi (E2E)

Kontrol Full-Duplex/Half-Duplex

QoS (specifikasi toleransi delay maximum)



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Layer 6: Presentation Layer Fungsi Utama: Encryption, compression, dll

Presentation Layer

Encrypted Data

Raw Data

Encryption

Presentation Layer

Compressed Data

Raw Data

Compression

Fungsi Utama: Interface ke application programs

Layer 7: Application Layer

Contoh: Network API (Application Program Interface)



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Model Seven Layer OSI - Summary


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Bagaimana Data Mengalir?

Saat data dikirim dari application pd komputersumber hal berikut terjadi Data dlm bentuk suatu segmentbergerak turun

melalui layer-layer Saat mencapai Physical Layer siap dikirim melalui

media Pd Physical Layer bit-bit bisa analogatau digital, dlm

bentuk elektrikal, cahayaataugelombang radio


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End-to-End dan Point-to-Point

Host A Host B

Intermediate Routers

Point-to-point

NIC

End-to-end


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Sekian

Documents

3.Communication Protocol