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 .
OmGals
Senin, 12 Mei 2014
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.
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:
Materi Selanjutnya : http://yayagia.blogspot.com/2014/03/client-server.html
Sumber :
http://dhedee29.staff.gunadarma.ac.id/Downloads/files/34455/CLIENT+SERVER.pdf
http://blogeko3.blogspot.com/2012/07/pengertian-clent-server-dan-peer-to-peer.html
http://komputer-techno.blogspot.com/2014/01/pengertian-client-server-dan-peer-to.html
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.
Referensi :
Langganan:
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