Senin, 12 Mei 2014

4IA10_SOFTSKILL_PENGANTAR KOMPUTASI MODERN_GALIH MUHAMMAD RIDLO_TUGAS3

A. Quantum Computing
Quantum Computation or quantum computer is a tool for the calculation , which uses direct calculation of quantum mechanical phenomena such as superposition and the computation and entanglement to perform operations on data. Quantum computers are different from traditional computers based on transistors . Differences with a quantum computer on a classical computer is a classical computer has a memory made ​​up of bits , where each bitmewakili either one or zero . While a quantum computer is maintaining the order qubit.Sebuah single qubit can represent a one , a zero , or , crucially . The basic principle of quantum computers is that the quantum properties of particles can be used to represent data and data structures , and that quantum mechanics can be used to perform operations with this data . In this case the system to develop a quantum computer needed a new logic in accordance with the principles of quantum .

The idea of ​​a quantum computer comes from some physicists , among others, Charles H. Bennett of IBM , Paul A. Benioff of Argonne National Laboratory , Illinois , David Deutsch of the University of Oxford , and Richard P. Feynman of the California Institute of Technology ( Caltech ) . At first the idea of the Feynman suggested that a quantum system can also perform the counting process . Fenyman also suggested that this system could be a simulator for quantum physics experiments . Furthermore, the scientists began doing research on the quantum system , they are also trying to find logic in accordance with the system . Until now it has dikemukaan two new algorithms that can be used in quantum systems and algorithms are algorithms shor grover .

Although quantum computing is still in development , has conducted experiments in which quantum computational operations carried out on a small number of qubits . Research both in theory and in practice continues in a fast pace , and many national government and military funding agencies support quantum computing research to the development both for the people and national security issues such as cryptanalysis.

Has been entrusted with a very broad , that if large -scale quantum computers can be made , then the computer can solve some problems much faster than a normal computer . Different quantum computers with classical DNA computers and computer -based transistors , although these types of computers might use principles of quantum mechanics . Some computing architectures such as optical computers despite using classical superposition of electromagnetic waves , but without a specific source sepertiketerkaitan quantum mechanics , then there could potentially have a computing speed as owned by a quantum computer .

B. Entanglement

The physicists from the University of Maryland has been one step closer to quantum computer by demonstrating the existence of entanglement between two quantum bits , each made with a type of dense circuit known as a Josephson junction .

Published in the journal Science this week , these results demonstrate the latest advances in scientific endeavors properties of quantum physics apply to the manufacture of computers are much better than existing supercomputers .
The team of physicists led by Professor Fred Wellstood from Center for Superconductivity

Research ( a research center belonging to the Department of Physics University of Maryland ) said their findings are the first to indicate the success of the creation of entanglement between qubits Josephson junction . Entanglement is a quantum mechanical effect that blurs the distance between individual particles so difficult to describe the particles separately even though you are trying to move them .

So what is Entanglement ? Entanglement is the essence of quantum computing because it is interwoven quality associated with a lot more information in quantum bits than the bits of classical computing , "said Andrew Berkley , one of the researchers . The latest findings bring the path to quantum computers , and indicates that the Josephson junction could eventually be used to build a super computer .

C. Pengopeasian the data qubits

Quantum information science begins with the fundamental resources generalize classical information - bit - into quantum bits , or qubits . As bits are ideal objects are abstracted from the principles of classical physics , qubits are quantum objects are abstracted ideal of the principles of quantum mechanics . Can be represented by a bit - magnetic region on the disc , the voltage on the circuit , or sign graphite pencil on paper made ​​. Functioning of classical physical statuses as bits do not depend on the details of how they are realized . Similarly , the attributes qubit is independent of specific physical representation of the atomic nucleus as a centrifuge or , say , the polarization of a photon of light .
Illustrated by the status bits , 0 or 1 . Similarly , the qubit is described by quantumnya status . Two potential for qubit quantum state is equivalent to the classical bits 0 and 1 . But in quantum mechanics , any object that has two different status certainly has a series of other potential state , called superposition , that led up to the status of second -degree manifold . Qubit statuses are allowed exactly is all the status that must be achieved , in principle , by the classical bits are transplanted into the quantum world . Status - qubit state is equivalent to the points on the surface of the ball , where 0 and 1 as the south pole and the north [ see box below ] . Continuum between 0 and 1 status fostered many outstanding attributes of quantum information .



D. Quantum Gates

In quantum computers and quantum circuit model of computation in particular , a quantum logic gates or quantum gates are the basic operations of quantum circuits on a small number qubit.Mereka are the building blocks of quantum circuits , such as logic gates for circuits digitalkonvensional classic .


E. Shor's Algorithm

Shor's algorithm is a further example of the basic paradigm ( how much computational time required to find a factor of n - bit integers ? ) , But this algorithm seems isolated from most of the other findings of quantum information science . At first glance, it is just as ingenious programming tricks with little fundamental significance . Appearances are deceptive ; researchers have shown that Shor's algorithm can be interpreted as an example of a procedure to assign the energy levels of quantum systems , a process that is fundamental . As time goes on and we charge more on the map , should be so easy to understand the principles underlying Shor's algorithm and other quantum algorithms and , we hope , develop new algorithms .

Senin, 28 April 2014

Cloud Computing

Cloud computing in general can be portrayed as a synonym for distributed computing over a network, with the ability to run a program or application on many connected computers at the same time. It specifically refers to a computing hardware machine or group of computing hardware machines commonly referred as a server connected through acommunication network such as the Internet, an intranet, a local area network (LAN) or wide area network (WAN) and individual users or user who have permission to access the server can use the server's processing power for their individual computing needs like to run an application, store data or any other computing need. Therefore, instead of using a personal computer every-time to run the application, the individual can now run the application from anywhere in the world, as the server provides the processing power to the application and the server is also connected to a network via internet or other connection platforms to be accessed from anywhere. All this has become possible due to increasing computer processing power available to humankind with decrease in cost as stated in Moore's law.In common usage, the term "the cloud" is essentially a metaphor for the Internet. Marketers have further popularized the phrase "in the cloud" to refer to software, platforms and infrastructure that are sold "as a service", i.e. remotely through the Internet. Typically, the seller has actual energy-consuming servers which host products and services from a remote location, so end-users don't have to; they can simply log on to the network without installing anything. The major models of cloud computing service are known as software as a service, platform as a service, and infrastructure as a service. These cloud services may be offered in a public, private or hybrid network. Google, Amazon, IBM, Oracle Cloud, Rackspace, Salesforce, Zoho and Microsoft Azure are some well-known cloud vendors. Network-based services, which appear to be provided by real server hardware and are in fact served up by virtual hardware simulated by software running on one or more real machines, are often called cloud computing. Such virtual servers do not physically exist and can therefore be moved around and scaled up or down on the fly without affecting the end user, somewhat like a cloud becoming larger or smaller without being a physical object.
From the above explanation of cloud computing , there are many benefits that we can take from cloud computing , namely :
1.    Scalability , ie cloud computing we can increase our storage capacity without having to purchase additional equipment , such as hard drives , etc. . We simply add the capacity provided by the cloud computing service providers .
2.    Accessibility , ie we can access data whenever and wherever we are , as long as we are connected to the Internet , making it easier for us to access the data when important .
3.    Security , we can be assured that the data security of its cloud computing service provider , so for IT based company , the data can be stored securely in the cloud computing provider . It also reduces the cost required to secure corporate data .
4.    Creation , ie the user can do / develop their creations or projects without having to submit their projects directly to the company , but the user can send it through the cloud computing service providers .
5.    Anxiety , when a natural disaster strikes our proprietary data stored safely in the cloud even though we damaged hard drive or gadget
Here is how the data storage and replication of data on the use of cloud computing technology . With Cloud Computing is no longer a local computer should run the heavy computational work required to run the application , no need to install a software package for every computer , we only perform the installation of the operating system on application . Computer networks that make up the cloud ( Internet ) handles them instead . This server will be running all applications ranging from e - mail , word processing , to complex data analysis programs . When users access the cloud ( internet ) for a popular website , many things can happen . Users of Internet Protocol ( IP ) for example can be used to determine where the user is located ( geolocation ) . Domain Name System ( DNS ) services can then redirect the user to a server cluster that is close to the users so that the site can be accessed quickly and in their local language . The user is not logged into the server , but they login to their services using a session id or cookie that has been obtained is stored in their browser . What users see in the browser usually comes from a web server . Webservers run the software and interface presents the user with the means used to collect orders or instructions from the user ( click , type, upload , etc. ) These commands are then interpreted by webservers or processed by the application server . Information is then stored in or retrieved from a database server or file server and the user is then presented with a page that has been updated . The data is synchronized across multiple servers around the world for global access quickly and also to prevent data loss.
Characteristic of Cloud Computing :
1 . On Demand Self Service ( yourself when self-service is needed )
Users can order and manage services without human interaction with the service provider , for example by using a , a web portal and interface management . Procurement of services and equipment as well as related resources occur automatically on providers
2 . Broad Network Access ( access to large networks )
Services available are connected via broadband networks , especially for adequately accessible through the Internet , either using a thin client , thick clien , or other media such as smartphones .
3 . Resource Pooling (resource fused )
Cloud service providers provide services through resources that are grouped in one or multiple locations of data centers consisting of a number of servers with multi - tenant mechanism . This mechanism allows a multi- tenant computing resource is shared by several users , where those resources either in the form of physical or virtual, can be allocated dynamically to the needs of users / customers on demand . Thus , customers do not need to know how and where the demand for computing resources met by the service providers . Importantly , all requests can be fulfilled . The computing resources include storage , memory , processor , network band , the virtual machine .
4 . The Rapid Elasticity ( rapid elasticity )
Computing capacity that can be provided rapidly and elastically supplied , be it in the form of the addition or reduction of the required capacity .
5 . Measured Service ( measurement )
Available cloud resources should be managed and optimized its use , with a measurement system that can measure the usage of each computing resource use ( storage , memory , processor , bandwidth , and user activity , etc. ) . Thus , the amount of resources used can be measured in a transparent manner which will be the basis for the user to pay for the cost of using the service .
The relative security of cloud computing services is a contentious issue that may be delaying its adoption. Physical control of the Private Cloud equipment is more secure than having the equipment off site and under someone else's control. Physical control and the ability to visually inspect data links and access ports is required in order to ensure data links are not compromised. Issues barring the adoption of cloud computing are due in large part to the private and public sectors' unease surrounding the external management of security-based services. It is the very nature of cloud computing-based services, private or public, that promote external management of provided services. This delivers great incentive to cloud computing service providers to prioritize building and maintaining strong management of secure services.[146] Security issues have been categorised into sensitive data access, data segregation, privacy, bug exploitation, recovery, accountability, malicious insiders, management console security, account control, and multi-tenancy issues. Solutions to various cloud security issues vary, from cryptography, particularly public key infrastructure (PKI), to use of multiple cloud providers, standardisation of APIs, and improving virtual machine support and legal support
When talking about cloud computing system , the system is divided into two sections : the front end and back end . They are connected to each other through a network , usually the Internet . The front end is the side the computer user (user ) , or the client ( the client ) , see . The back is the " cloud " part of the system . The front end includes the client computer ( or computer network ) and the application is required to access the cloud computing system .

Not all cloud computing systems have the same user interface . Services such as Web - based e - mail program utilizes existing Web browsers such as Internet Explorer or Firefox . Other systems have unique applications that provide network access to clients . At the back end of the system are the various computers , servers and data storage systems that create the " cloud " of computing services . In theory , a cloud computer system can include almost any computer program you can imagine , from the data processing to video games . Typically , each application will have its own dedicated server . cloud computing servers centrally manage the system , monitoring traffic and client demands to ensure everything runs smoothly . These systems follow a set of rules called protocols and uses a special kind of software called middleware . Middleware network allows computers to communicate with each other . Mostly, the server is not running at full capacity . That means no processing power unused waste products . It will require a way . This technique is called server virtualization . By maximizing the output from each server , server virtualization reduces the need for the machine to work . 

Rabu, 26 Maret 2014

Mobile Computing Application

Mobile computing is human–computer interaction by which a computer is expected to be transported during normal usage. Mobile computing involves mobile communication, mobile hardware, and mobile software. Communication issues include ad hoc and infrastructure networks as well as communication properties, protocols, data formats and concrete technologies. Hardware includes mobile devices or device components. Mobile software deals with the characteristics and requirements of mobile applications. - Wikipedia

Examples of applications such as mobile banking :

Push Email
Push email is an email system that provides an always-on capability, in which new email is actively transferred (pushed) as it arrives by the mail delivery agent (MDA) (commonly called mail server) to the mail user agent (MUA), also called the email client. Email clients include smartphones and, less strictly, IMAP personal computer mail applications.
In Blackberry, BlackBerry uses wireless mail user agent devices and a BlackBerry Enterprise Server(BES) attached to a traditional email system. The BES monitors the email server, and when it sees new email for a BlackBerry user, it retrieves (pulls) a copy and then pushes it to the BlackBerry handheld device over the wireless network.
BlackBerry became very popular, in part because it offers remote users "instant" email; new emails appear on the device as soon as they arrive, without the need for any user intervention. Thehandheld becomes a mobile, dynamically updating, copy of the user's mailbox. As a result of the success of BlackBerry, other manufacturers have developed push email systems for other handheld devices, such as Symbian- and Windows Mobile-based mobile phones. However, they only support push email for some email services.
With the release of the BlackBerry 10 operating system for its new generation of mobile device, BES is no longer available for non-corporate client email delivery. Instead, BlackBerry 10 offers POP, IMAP, or ActiveSync for transferring email to and from a device. Of these, the latter two can provide push email delivery if the server supports it.

Mobile Banking
Mobile banking is a system that allows customers of a financial institution to conduct a number offinancial transactions through a mobile device such as a mobile phone or personal digital assistant.
Mobile banking differs from mobile payments, which involve the use of a mobile device to pay for goods or services either at the point of sale or remotely,analogously to the use of a debit or creditcard to effect an EFTPOS payment.
The earliest mobile banking services were offered over SMS, a service known as SMS banking. With the introduction of smart phones with WAP support enabling the use of the mobile web in 1999, the first European banks started to offer mobile banking on this platform to their customers.
Mobile banking has until recently (2010) most often been performed via SMS or the mobile web. Apple's initial success with iPhone and the rapid growth of phones based on Google's Android (operating system) have led to increasing use of special client programs, called apps, downloaded to the mobile device. With that said, advancements in web technologies such as HTML5, CSS3 and JavaScript have seen more banks launching mobile web based services to complement native applications. A recent study (May 2012) by Mapa Research suggests that over a third of banks have mobile device detection upon visiting the banks' main website. A number of things can happen on mobile detection such as redirecting to an app store, redirection to a mobile banking specific website or providing a menu of mobile banking options for the user to choose from.

From the above explanation, we can conclude that Mobile computing applications are required to inform a news or information in the state of moving (mobile).
From Mobile computing applications make us easy  to do something more fast.  We just need install the application what we need on our mobile computing.  There are free and paid.  This is mobile computing appliation that many people use :
  • Database queries over the static network for information such as weather,or  trac conditions, and performing share transactions, or home shopping.
  • Client{server applications, such as World Wide Web (WWW) browsing, electronic mail, Usenet news, and remote sessions on static computers.
  • Multimedia applications, such as a video phone, television broadcasts, video mail, and video on demand.
  • Collaborative working, requiring a group protocol for distributed transactions and floor control.
Referensi : 
http://en.wikipedia.org/wiki/Push_email
http://en.wikipedia.org/wiki/Mobile_banking
http://teknophobia.blogspot.com/2014/03/mobile-computing-applications.html

Selasa, 25 Maret 2014

Client Server

Arsitektur jaringan Client Server merupakan model konektivitas pada jaringan yang membedakan fungsi computer sebagai Client dan Server. Arsitektur ini menempatkan sebuah komputer sebagai Server. Server ini yang bertugas memberikan pelayanan kepada terminal-terminal lainnya yang terhubung dalam sistem jaringan atau yang kita sebut Clientnya. Server juga dapat bertugas untuk memberikan layanan berbagi pakai berkas (file server), printer (printer server), jalur komunikasi (server komunikasi).

Pada model arsitektur ini, Client tidak dapat berfungsi sebagai Server, tetapi Server dapat berfungsi menjadi Client (server non-dedicated). Prinsip kerja pada arsitektur ini sangat sederhana, dimana Server akan menunggu permintaan dari Client, memproses dan memberikan hasil kepada Client, sedangkan Client akan mengirimkan permintaan ke Server, menunggu proses dan melihat visualisasi hasil prosesnya.
Sistem Client Server ini tidak hanya diperuntukkan bagi pembangunan jaringan komputer skala luas. Sistem ini menggunakan protokol utama Transmision Control Protocol/Internet Protocol (TCP/IP), sedangkam sistem operasi yang digunakan antara lain Unix, Linux dan Windows NT.
Lingkungan Database Client/Server di Internet
  • Menggunakan LAN untuk mendukung jaringan PC
  • Masing-masing PC memiliki penyimpan tersendiri
  • Berbagi hardware atau software

Komponen dasar Client Server
Pada dasarnya Client Server terdiri dari 3 komponen pembentuk dasar, yaitu Client, Middleware, dan Server. Gubungan dari ketiganya dapat digambarkan sebagai berikut:


Senin, 17 Maret 2014

Protocol Layer

Protokol merupakan sebuah rule, prosedur dan pengaturan sejumlah operasi peralatan komunikasi data, dalam komunikasi data, aturan-aturan meliputi cara membuka hubungan, mengirim paket data, menginformasi jumlah data yang diterima, dan meneruskan pengiriman data. Protokol dapat diterapkan pada perangkat keras, perangkat lunak atau kombinasi dari keduanya. Pada tingkatan yang terendah, protokol mendefinisikan koneksi perangkat keras.
Prinsip dalam membuat protokol ada tiga hal yang harus dipertimbangkan, yaitu efektivitas, kehandalan, dan Kemampuan dalam kondisi gagal di network. Protokol distandarisasi oleh beberapa organisasi yaitu IETF, ETSI, ITU, dan ANSI.
Tugas yang biasanya dilakukan oleh sebuah protokol dalam sebuah jaringan diantaranya adalah :
1.      Melakukan deteksi adanya koneksi fisik atau ada tidaknya komputer / mesin lainnya.
2.      Melakukan metode “jabat-tangan” (handshaking).
3.      Negosiasi berbagai macam karakteristik hubungan.
4.      Bagaimana mengawali dan mengakhiri suatu pesan.
5.      Bagaimana format pesan yang digunakan.
6.      Yang harus dilakukan saat terjadi kerusakan pesan atau pesan yang tidak sempurna.
7.      Mendeteksi rugi-rugi pada hubungan jaringan dan langkah-langkah yang dilakukan selanjutnya.
8.      Mengakhiri suatu koneksi.

Dalam Model OSI terdapat 7 layer dimana masing-masing layer mempunyai jenis protokol sesuai dengan peruntukannya. Sebuah standar protokol yang dikenal sebagai OSI (Open System Interconection) model dengan aisitrktur sebagai berikut.
Arsitektur OSI dibuat berlapis-lapis dengan fungsi yang berbeda pada setiap lapisannya. Lapisan yang lebih tinggi menyembunyikan kerumitan dari operasi di lapisan yang lebih rendah dan suatu lapisan hanya dapat di akses oleh lapisan yang ada di atasnya atau di bawahnya.Hal tersebut di maksudkan untuk memberi kemudahankepada para pembuat perangkat keras dan perangkat lunak komunikasi dalam mengembangkan berbagai protokol yang berbeda sesuai kebutuhan. Namun tetap mereka harus mematuhi standar yang telah di berikan OSI.

Lapisan layer protokol tersebut dapat di golongkan lebih jauh menjadi:
1.      Low level Layers
2.      Transport Layers
3.      Higher Level Layer

1.      a.      Low level Layers
Yang termasuk Low layers adalah lapisan-lapisan sebagi berikut:
1.      Physical Layer: Spesifikasi dan implementasi dari bit-bit dan proses transmisi dari pengirim ke penerima. Berfungsi untuk mendefinisikan media transmisi jaringan, metode pensinyalan, sinkronisasi bit, arsitektur jaringan (seperti halnya Ethernet atau Token Ring), topologi jaringan dan pengkabelan. Selain itu, level ini juga mendefinisikan bagaimana Network Interface Card (NIC) dapat berinteraksi dengan media kabel atau radio.
2.      Data Link Layer: Bertanggung jawab mengurusi perubahan bit=bit data menjadi frame untuk mengatasi error dan penontrolan pengiriman frame. Befungsi untuk menentukan bagaimana bit-bit data dikelompokkan menjadi format yang disebut sebagai frame. Data link layer melakukan tugasnya dengan meletakkan pola bit khusus pada awal dan akhir dari setiap frame untuk menandai mereka, serta komputasi checksum dengan menjumlahkan semua byte dalam bingkai dengan cara tertentu.
Ketika frame tiba, penerima recomputes checksum dari data dan membandingkan hasilnya dengan checksum mengikuti frame. Jika setuju, frame dianggap benar dan diterima. Jika mereka tidak setuju, penerima meminta pengirim untuk retrasmit itu. Frame ditugaskan nomor urut (di header), sehingga semua orang dapat memberitahukan yang mana.
1.      Network Layer: Mengatur bagaimana paket-paket di arahkan berdasarkan alamat logik. lapisan bertanggung jawab untuk menerjemahkan alamat logis jaringan ke alamat fisik jaringan. Berfungsi untuk mendefinisikan alamat-alamat IP, membuat header untuk paket-paket, dan kemudian melakukan routing melalui internetworking dengan menggunakan router dan switch layer. Lapisan ini juga member identitas alamat, jalur perjalanan pengiriman data, dan mengatur masalah jaringan misalnya pengiriman paket-paket data.
Saat ini, mungkin protokol jaringan yang paling banyak digunakan adalah IP connectionless (Internet Protocol), yang merupakan bagian dari protokol internet. Sebuah paket IP dapat dikirim tanpa pengaturan apapun. Setiap paket IP diarahkan ke tujuan yang independen dari semua orang lain. Tidak ada jalur internal dipilih dan diingat.

1.      b.      Transport Layers
Merupakan lapisan yang memberi fasilitas komunikasi bagi kebanyakan sistem tersebar. Berfungsi untuk memecah data ke dalam paket-paket data serta memberikan nomor urut ke paket-paket tersebut sehingga dapat disusun kembali pada sisi tujuan setelah diterima. Selain itu, pada level ini juga membuat sebuah tanda bahwa paket diterima dengan sukses (acknowledgement), dan mentransmisikan ulang terhadap paket-paket yang hilang di tengah jalan.
Pada lapisan ini terdapat dua macam protokol yang sering digunakan, yaitu:
1.      Transport Control Protocol (TCP) adalah protocol yang connection-oriented, yang berarti komunikasi yang melewatinya membutuhkan handshaking untuk mengatur koneksi end-to-end. Koneksi dapat dibuat dari client ke server, dan kemudian banyak data dapat dikirimkan melalui konesi itu. TCP memiliki karakteristik sebagai berikut:
1.      Connection-oriented merupakan sistem yang akan berkomunikasi harus terlebih dulu saling mengetahui dan sepakat
2.      Reliable, tersedia mekanisme menjamin paket yang rusak atau hilang dikirim ulang
3.      Stream –oriented communication
4.      Membutuhkan sumberdaya komputasi dan jaringan lebih dari UDP
5.      User Datagram Protocol (UDP) adalah protocol connectionless message-based yang lebih sederhana. Di protocol connectionless, tidak ada usaha yang dibuat untuk koneksi end-to-end. Koumikasi dicapai dengan mengirimkan informasi satu arah, dari source ke destination tanpa mengecek untuk melihat apakah tujuan masih ada, atau apakah koneksi disiapkan untuk menerima informasi. Paket UDP melewati jaringan dalam unit-unit yang berdiri sendiri. UDP memiliki karakteristik sebagai berikut:
1.      Connectionless, tidak memerlukan adanya saling mengetahui dan kesepakatan
2.      Unreliable datagram communication, tidak tersedianya mekanisme yang menjamin paket rusak atau dikirim ulang.

Manfaat TCP dibandingkan dengan UDP adalah bahwa ia bekerja andal melalui jaringan apapun. Kelemahan yang jelas adalah bahwa TCP memperkenalkan overhead yang jauh lebih, terutama dibandingkan dengan kasus-kasus di mana jaringan yang mendasarinya sangat handal, seperti dalam sistem area lokal. Ketika kinerja dan kehandalan yang dipertaruhkan, solusi alternatif selalu untuk menggunakan UDP, dan mengkombinasikannya dengan kesalahan tambahan dan kontrol aliran yang dioptimalkan untuk aplikasi tertentu. Kelemahan dari pendekatan ini adalah bahwa pekerjaan pembangunan banyak ekstra perlu dilakukan, tetapi juga bahwa solusi proprietary diperkenalkan, yang mempengaruhi keterbukaan sistem.
Apa yang membuat TCP begitu menarik dalam banyak kasus, adalah bahwa hal itu tidak disesuaikan untuk mendukung jawaban perilaku permintaan sinkron interaksi klien yang paling server. Dalam keadaan normal, ketika pesan tidak tersesat, menggunakan TCP untuk interaksi client server hasil seperti yang ditunjukkan pada gambar 2-4 (a). Pertama, klien memulai setup sambungan, yang dilakukan dengan menggunakan tiga cara protokol jabat tangan, ditampilkan sebagai tiga pesan pertama di gambar 2-4 (a). Protokol ini diperlukan untuk kedua belah pihak untuk mencapai kesepakatan pada urutan penomoran untuk paket yang akan dikirim melalui sambungan. Ketika koneksi telah dibentuk, client mengirimkan permintaannya (pesan 4), langsung diikuti oleh paket memberitahu server untuk menutup koneksi (pesan 5).
Gambar 2-4 (a) Pengoperasian normal TCP. (B) Transaksional TCP
Server merespon dengan segera mengakui bahwa ia menerima permintaan klien, piggybacked dengan pengakuan bahwa koneksi akan clossed bawah (pesan 6). Server kemudian melakukan pekerjaan yang diminta dan mengirimkan jawaban kepada klien (pesan 7), diikuti dengan permintaan untuk melepaskan koneksi juga (pesan 8). Klien hanya perlu merespon dengan pengakuan untuk menyelesaikan komunikasi dengan server (pesan 9).
Jelas, banyak overhead dalam TCP berasal dari benar-benar mengelola koneksi. Ketika TCP digunakan untuk interaksi client server, itu jauh lebih murah untuk menggabungkan pengaturan koneksi dengan segera mengirimkan permintaan, dan seperti bijaksana untuk menggabungkan mengirimkan jawaban dengan menutup koneksi. Protokol yang dihasilkan disebut TCP untuk Transaksi, disingkat T / TCP, dan esensi dari bagaimana ia beroperasi di bawah kondisi normal ditunjukkan pada gambar 2-4 (b).
Apa yang terjadi dalam keadaan normal, adalah bahwa klien mengirimkan pesan tunggal (ditampilkan sebagai pesan 1) yang berisi tiga potongan informasi: permintaan untuk mengatur koneksi, permintaan layanan yang sebenarnya, dan permintaan memberitahu server yang segera bisa merobek turun koneksi sesudahnya.

Server merespon setelah ia dilayani permintaan yang sebenarnya, sehingga dapat mengirim jawaban bersama dengan data yang diperlukan untuk menerima koneksi, dan segera meminta rilis, ditampilkan sebagai pesan pada Gambar 2. 2-4 (b). Sekali lagi, klien hanya perlu mengakui rilis final dari koneksi (pesan 3).

Selasa, 11 Maret 2014

PERMASALAHAN PADA SISTEM TERDISTRIBUS

Dalam sebuah sistem berbasis komputer yang besar hampir semuanya  menerapkan sistem terdistribusi. Sistem terdistribusi adalah sistem pemrosesan informasi yang didistribusikan kepada beberapa komputer dan tidak terbatas hanya pada satu mesin saja.



Ada beberapa tipe sistem yang utama yaitu :
1.         Sistem Personal yang tidak terdistribusikan dan dirancang untuk satu  
workstation saja.
2.         Sistem Embeded yang berjalan pada satu prosessor atau pada kelompok prosessor
yang terintegrasi.
3.         Sistem terdistribusi dimana perangkat lunak sistem berjalan pada kelompok prosessor
yang bekerja sama dan terintegrasi secara longgar, dengan dihubungkan oleh jaringan.


Kelemahan Pada Sistem Terdistribusi,meliputi berberapa aspek yang salingberkaitan :

·            Kompleksitas
            Sistem terdistribusi bersifat lebih kompleks daripada sistem sentral.

·            Kesulitan dalam Software
Maksudnya masalah yang akan dihadapi antara lain mengenai Bahasa Pemrograman yang harus digunakan maupun sebuah sistem operasi dan lain-lain.

·            Jaringan 
Sistem terdistribusi di implementasikan dalam jaringan komputer,maka yang berkaitan dengan jaringan komputer akan menjadi pertimbangan utama dalam merancang dan mengimplementasikan Sistem. 

·            Keamanan
Pada sistem terdistribusi berbagi data atau pun sumber daya merupakan hal yang mutlak maka muncul masalah-masalah yang berkaitan dengan keamanan data.


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