Protokol, Arsitektur Protokol dan Model Lapisan OSIAnhar19@gmail.com

Organisasi Komputer Dihubungkan ke Jaringan KomputerComputer AApplication Program Network Protocol

Computer BApplication Program Network Protocol

Wire (Computer Network)07/04/2013 2

Perlunya Protokol Used for communications between entities in a system Must speak the same language Entities User applications e-mail facilities terminals

Systems Computer Terminal Remote sensor07/04/2013 3

Perlunya protokol

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Protokol KomunikasiDefinisi Protocol Jaringan:

Satu set aturan yang mengatur komunikasi antarar dua host dimplementasikan sbg software Contoh - TCP - IP

- IPX/SPX (Novel Netware)07/04/2013 5

Elemen Kunci dr Protokol Syntax Data formats Signal levels

Semantics Control information Error handling

Timing Speed matching Sequencing07/04/2013 6

Arsitektur Protokol? Task of communication broken up into modules For example file transfer could use three modules File transfer application Communication service module Network access module

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Konsep file transfer sederhana

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Model Tiga Lapisan Network Access Layer Transport Layer Application Layer

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Network Access Layer Exchange of data between the computer and the network Sending computer provides address of destination Dpt menuntut level layanan (mis. Prioritas..) Dependent on type of network used (LAN, packet switched etc.)

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Transport Layer Reliable data exchange Independent of network being used Independent of application

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Application Layer Support for different user applications e.g. e-mail, file transfer

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Perlunya Pengalamatan Two levels of addressing required Each computer needs unique network address Each application on a (multi-tasking) computer needs a unique address within the computer The service access point or SAP

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Arsitektur Protokol dan Jaringan

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Protokol-protokol dlm arsitektur yg sederhana

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Protocol Data Unit (PDU) At each layer, protocols are used to communicate Control information is added to user data at each layer Transport layer may fragment user data Each fragment has a transport header added Destination SAP Sequence number Error detection code

This gives a transport protocol data unit07/04/2013 16

Jaringan PDU Adds network header network address for destination computer Facilities requests

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Arsitektur Protokol TCP/IP Developed by the US Defense Advanced Research Project Agency (DARPA) for its packet switched network (ARPANET) Used by the global Internet No official model but a working one. 07/04/2013

Application layer Host to host or transport layer Internet layer Network access layer Physical layer18

Physical Layer Physical interface between data transmission device (e.g. computer) and transmission medium or network Characteristics of transmission medium Signal levels Data rates etc.

Network Access Layer Exchange of data between end system and network Destination address provision Invoking services like priority

Internet Layer (IP) Systems may be attached to different networks Routing functions across multiple networks Implemented in end systems and routers

Transport Layer (TCP) Reliable delivery of data Ordering of delivery

Model TCP/IP

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Model OSI Open Systems Interconnection Developed by the International Organization for Standardization (ISO) Seven layers A theoretical system delivered too late! TCP/IP is the de facto standard

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Tujuh Layers ?Layer 7 Layer 6 Layer 5 Layer 4 Layer 3 Layer 2 Layer 1 Application Presentation

SessionTransport Network Data Link Physical

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OSI vs TCP/IP

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Layer-layer Dlm hal tujuan dan tanggung jawab, tiap layer terpisah dan independen Masing-masing punya fungsi sendiri, tetapi juga menyediakan service ke layer di atas dan di bawahnya Model sebagai bantuan utk memahami komunikasi pada jaringan dan berguna dalam memilah kesalahan/troubles yg mungkin terjadi pd jaringan Memungkinkan baik software engineer dan hardware manufacturers menjamin produk mereka bisa bekerja sama07/04/2013 27

Kerja layer-layerNODE A Sending Device Layer 7 Application Layer Layer 6 Presentation Layer Layer 5 Session Layer Layer 4 Transport Layer Layer 3 Network Layer Layer 2 Data Link Layer Layer 1 Physical Layer Supports the communication between applications over the network Presents data to the receiver in a form it recognises Establishes a connection and terminates it when no longer required Acknowledges the flow of data including re-transmission where required Adds the appropriate network addresses to packets NODE B Receiving Devic e Layer 7 Application Layer Layer 6 Presentation Layer Layer 5 Session Layer Layer 4 Transport Layer Layer 3 Network Layer Layer 2 Data Link Layer Layer 1 Physical Layer

Adds the MAC addresses to packets

Transmits the data on the medium

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Bagaimana Data Mengalir?Saat data dikirim dari application pd komputer sumber hal berikut terjadi Data dlm bentuk suatu packet bergerak turun melalui layer-layer Saat mencapai Physical Layer siap dikirim melalui media Pd Physical Layer bit-bit bisa analogue atau digital, dlm bentuk electrikal, cahaya atau gelombang radio

Bagaimana Data Mengalir?(2) Data ditransmisikan ke device tujuan Bergerak melalui layer-layer dari model OSI, mencapai user Dlm pergerakan melalui layer-layer data di encapsulated yaitu informasi tambahan ditambahkan sbg headers atau trailers Data di dlm paket tdk berubah

Functions Encapsulation Segmentation and reassmebly Connection control Ordered delivery Flow control Error control Addressing Multiplexing Transmission services

EncapsulationApplicat ion Present at ion Session Transport Net work Dat a Link PhysicalP resentation Header

DATA PH PH PH PH PH DATA DATA DATA DATA DATA DLTData Link Trailer

Session Header

SH SH SH SH

Transp ort Header

TH TH TH

Network Header

NH

Data Link Header

DLH NH

Bit s To Destination Device

Konsep PaketTanpa Packet User Data Computer Network User Data

Internet

Dengan Packet User Data

Packet

Computer Network User DataInternet

(mis. destination address) Packet Header (mis. packet sequence #)

Konsept Packet Encapsulation: Layered Protocol ArchitectureOSI 7-Layer ModelUser Data

TCP/IP ModelUser Data

7 layers

4 layers

Host Computer

Host Computer

Network Cable

Network Cable

Packet Encapsulation Visualisasi (1):Protocol Data Unit (PDU) Header TCP Layer IP Layer Datalink Layer Physical Layer User Data (User Data Packet) TCP Packet IP Packet Network Layer Frame Physical Layer Frame

Header = Information spesifik ke tiap protocol layer Packet = Header + PDU

Packet Encapsulation Visualisasi (2):

Protocol Data Unit (PDU) Header TCP Layer IP Layer Datalink Layer Physical Layer User Data (User Data Packet) TCP Packet IP Packet Network Layer Frame Physical Layer Frame Packet Encapsulation

Packet Encapsulation Visualisasi (3):A packet in TCP layer TCP Layer User Data

TCP Packet

IP Layer

IP Packet

PDU in IP layer A packet (header + PDU) pd upper protocol layerPDU pd protocol layer berikutnya=

Packet Encapsulation Visualisasi (3):A packet in TCP layer TCP Layer

TCP PacketIP Packet PDU in IP layer

IP Layer

Pd IP protocol layer, informasi pd header TCP Akan ditangani sbg bagian dari user data Packet Encapsulation Segala perubahan pd TCP tdk akan Mempengaruhi disain internal dr IP

Packet Encapsulation:User Data

Komunikasi menggunakan Informasi pd packet header

User Data

4 3 2 1

4 3 2 1

NW InternetProtocol layer yg berkoresponden dp berkomunikasi

Segmentation (Fragmentation) Data blocks are of bounded size Application layer messages may be large Network packets may be smaller Splitting larger blocks into smaller ones is segmentation (or fragmentation in TCP/IP) ATM blocks (cells) are 53 octets long Ethernet blocks (frames) are up to 1526 octets long

Checkpoints and restart/recovery

Why Fragment? Advantages More efficient error control More equitable access to network facilities Shorter delays Smaller buffers needed

Disadvantages Overheads Increased interrupts at receiver More processing time

Connection Control Connection Establishment Data transfer Connection termination May be connection interruption and recovery Sequence numbers used for Ordered delivery Flow control Error control

Connection Oriented Data Transfer

Ordered Delivery PDUs may traverse different paths through network PDUs may arrive out of order Sequentially number PDUs to allow for ordering

Flow Control Done by receiving entity Limit amount or rate of data Stop and wait Credit systems Sliding window

Needed at application as well as network layers

Error Control Guard against loss or damage Error detection Sender inserts error detecting bits Receiver checks these bits If OK, acknowledge If error, discard packet

Retransmission If no acknowledge in given time, re-transmit

Performed at various levels

Addressing Addressing level Addressing scope Connection identifiers Addressing mode

Addressing level Level in architecture at which entity is named Unique address for each end system (computer) and router Network level address IP or internet address (TCP/IP) Network service access point or NSAP (OSI)

Process within the system Port number (TCP/IP) Service access point or SAP (OSI)

Address Concepts

Addressing Scope Global nonambiguity Global address identifies unique system There is only one system with address X

Global applicability It is possible at any system (any address) to identify any other system (address) by the global address of the other system Address X identifies that system from anywhere on the network

e.g. MAC address on IEEE 802 networks

Connection Identifiers Connection oriented data transfer (virtual circuits) Allocate a connection name during the transfer phase Reduced overhead as connection identifiers are shorter than global addresses Routing may be fixed and identified by connection name Entities may want multiple connections - multiplexing State information

Addressing Mode Usually an address refers to a single system Unicast address Sent to one machine or person

May address all entities within a domain Broadcast Sent to all machines or users

May address a subset of the entities in a domain Multicast Sent to some machines or a group of users

Multiplexing Supporting multiple connections on one machine Mapping of multiple connections at one level to a single connection at another Carrying a number of connections on one fiber optic cable Aggregating or bonding ISDN lines to gain bandwidth

Transmission Services Priority e.g. control messages

Quality of service Minimum acceptable throughput Maximum acceptable delay

Security Access restrictions

End-to-End dan Point-to-Point

Host A

Point-to-point

Host B

NIC

Intermediate Routers End-to-end

Model Seven Layer OSIApplication Program Tujuan Interface ke program user Data filters (compression, encryption) Manage koneksi end-to-end Menyediakan koneksi end-to-end Koneksi/pemgiriman paket ke tujuan Menyediakan koneksi point-to-point handal Berhub dg sinyal elektriksignals

Layer 7Layer 6 Layer 5 Layer 4 Layer 3 Layer 2 Layer 1NIC

Application Layer Presentation Layer Session Layer Transport Layer Network Layer Datalink Layer Physical Layer

Wire (Network Cable)

Model Seven Layer OSILayer 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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Model Seven Layer OSILayer 2: Data Link Layer Fungsi Utama: Deteksi dan koreksi error sinyal, jika ada 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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Model Seven Layer OSILayer 3: Network Layer

Fungsi Utama:

Best effort delivery service- Meroutekan paket dari sumber ke tujuan - Translasi address - Continue to check the status of a connection - Delete a connection when it is done

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Model Seven Layer OSILayer 4: Transport LayerFungsi Utama: Deteksi dan koreksi error paket (error control) utk E2E

Melaksanakan flow control- Jika penerima ingin slow down, mengurang laju transmisi TX - Jika network congesti, mengurang laju transmisi Layer 5: Session Layer Fungsi Utama: Establish/Manage/Delete koneksi (E2E) Kontrol Full-Duplex/Half-Duplex QoS (specifikasi toleransi delay maximum

Model Seven Layer OSILayer 6: Presentation Layer Encryption Raw Data Presentation Layer Encrypted Data Fungsi Utama: Encryption, compression, dll Compression Raw Data

Presentation LayerCompressed Data

Layer 7: Application Layer Fungsi Utama: Interface ke application programs Contoh: Network API (Application Program Interface)

Kesimpulan

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Latihan Sebutkan kerugian2 dari pendekatan protokol lapisan. Diskusikan kegunaan utk sebuah lapisan network dalam suatu jaringan broadcast. Ketika anda melakukan koneksi internet, alamat apa saja yg digunakan? Hubungan alamat tsb dng layer yg ada di OSI Jika pengecekan error sudah dilakukan hop by hop, kenapa masih perlu pengecekan error antar link?07/04/2013 66