TEKNIK KOMPUTER dan JARINGAN

Tahukah anda ? Kenapa Windows 2000 , dan windows Xp dapat diinstall di drive selain drive c: ?

Tidak seperti windows 95 ,windows 98 atau windows ME yang hanya bisa diinstall di drive c:  . Windows 2000 dan windows Xp , systemnya bisa diinstall di drive lain misalnya , drive d: , e: dan seterusnya itu, karena sebenarnya ada minimal 3 file yang harus ada di drive c:

Ke-tiga file tersebut adalah:

1.Ntldr , Ntldr adalah file system yang ada  windows 2000 atau windows Xp ,yang berfungsi sebagai penghubung antara MBR (Master Boot Record) dan System Operasi agar System bisa booting,atau kalau di windows 98 seperti command.com.Tanpa file ini bila komputer kita nyalakan maka akan keluar tampilan ntldr missing.

2. Ntdetect.com, file ini adalah file system yang ber fungsi untuk mendeteksi di mana ada folder system (windows 2000/windows xp) berada. Dengan adanya file ini System windows bisa di install sampai 3 system operasi (atau lebih) sekaligus , misalnya windows 98 ,  windows 2000 , windows xp. Tanpa adanya file ntdetect.com , windows akan restart terus menerus ataupun akan tampil blue screen.

3. Boot.ini , file ini dapat diakses melalui msconfig atau My Computer Click kanan > Properties >Advanced > pilih setting startup and recovery, di sytem startup inilah kita bisa edit file boot.ini. Yang  sebenarnya file ini bertempat /  ada di C:\boot.ini

Kalau melalui msconfig , caranya ketik di menu run : msconfig >pilih tab boot.ini , disini kita bisa menentukan pilihan startup yang kita kehendaki.

Untuk keamanan Operating system saya, sarankan untuk meng-copy file ini (sebagai back up) dan ditempatkan di tempat terserah, sesuai selera anda.Yang penting suatu saat kalau diperlukan dapat anda kembalikan lagi.

Penting!!! Bagi yang meng-install dual boot misalnya Windows 98 dan windows xp ,bila windows 98 mau dihapus, jangan langsung format dan restart karena windows xp menaruh tiga file tersebut diatas di drive c: tempat windows 98. Jika terlanjur di format tempatkan lagi 3 file tersebut (ntldr , ntdetect.com , boot.ini) di drive c: sebelum direstart.

File tersebut attributnya hidden system .untuk menampilkannya kita ke folder option > pilih view >pilih show hidden files and folders dan hilangkan check (unchecked) pada hide protected operating system files (Recommended)

WANs are built to provide communication solutions for organizations or people who need to exchange digital information between two distant places (in one country or in two different countries). Since the distance is long, the local telecommunication company is involved, in fact, WANs are usually maintained by the country's public telecommunication companies (PTT's - like AT&T, Sprint, BEZEQ), which offer different communication services to the population.
The main purpose of a WAN is to provide reliable, fast and safe communication between two or more places (Nodes) with low delays and at low prices. WANs enable an organization to have one integral network between all its departments and offices, even if they are not all in the same building or city, providing communication between the organization and the rest of the world. In principle, this task is accomplished by connecting the organization (and all the other organizations) to the network nodes by different types of communication strategies and applications. Since WANs are usually developed by the PTT of each country, their development is influenced by each PTT's own strategies and politics.

Basic WANs
The basic WAN service which the PTT usually offers (for many years) is a Leased Line. A Leased Line is a point-to-point connection between two places, implemented by different transmission media (usually through PSTN Trunks), which creates one link between its nodes. An organization whose networks are based on such lines has to connect each office with one line, meaning that each office is connected to as many lines as the number of offices it is connected to, as shown in the figure below.
In the past, leased lines were just 4 wires connected between the two places, and the responsibility for communication fell on the organization and the good will of the PTT's personnel. These lines were not managed and often suffered from a lot of noise. Moreover, these lines consumed the PTT's bandwidth even when no transmission was occurring. Today, leased lines are usually point-to-point digital lines, which are implemented by creating a permanent channel, with known bandwidth, between the two nodes and transferring the data by a dedicated digital network, which enables automatic management on the line and minimizes noise interference.

For ages, the communication strategies of organizations were based on those lines and were usually built in a star configuration in order to minimize the amount of lines needed. It's easy to see that this configuration has a very weak point at its center.

In the 1970's, some PTTs built digital circuit switched communication networks which enabled creating a non permanent digital connection between two places (like telephone), but those networks did not provide the breakthrough in the communication technologies.

Packet Switched WANs
The Packet Switched WAN appeared in the 1960's, and defined the basis for all communication networks today. The principle in Packet Switched Data Network (PSDN) is that the data between the nodes is transferred in small packets. This principle enables the PSDN to allow one node to be connected to more than one other node through one physical connection. That way, a fully connected network, between several nodes, can be obtained by connecting each node to one physical link, as shown in the figure below.
Another advantage for Packet Switching was the efficient use of resources by sharing the Network bandwidth among the users (instead of dividing).
Today, X.25 transfer rates are considered to be very low, and this service is expected to be replaced with new services by the end of the century.

New Technologies
The communication target today is the ATM (and B-ISDN services). However, until applications and technologies for ATM become more developed, two main mid-time services are popularly used in the world today.
The first service is Frame Relay, which is considered to be the next generation for X.25, and enables faster communication rate (up to T3/E3) and better communication protocol. Until all its standards will be completed, Frame Relay is mainly a point-to-point service and replaces the leased lines. The second network service is ISDN, which is a fully digitized service, enabling communication for most types of data (voice, computer data and images) at all the network nodes (meaning in every house). This service is at its peak today and is been implemented mostly in Europe.
Those two communication networks are not fully developed yet, and will be spread in the world in the next years.

Future WANs
The ATM network and B-ISDN services, which provide solutions for all types of data (including video) are been developed today and are beginning to be implemented.
But even today, new networks are been designed for future demands. Those new networks are aimed to work at enormous rates of Giga-bps, and are providing new challenges for their designers.
For example in a medium speed of 64Kbps, transferring a file of 10KBit over a distance of 3000Km will take 0.015625sec plus a minimum of 10 microseconds is needed for light to reach from 1 point to the other. In a Giga-Net of speed 10E+10bps, transferring that same file will take 1 microsecond (plus 10 microseconds for light), meaning that the file will reach the network before the first bit will reach its destination. This example, and other issues make the next generation of WANs a very challenging one.

The WAN, has come a long way since the days of analog leased lines and is taking more and more tasks from the old separated networks into one integral network which enables good communication for any type of data or application.

Sebenarnya subnetting itu apa dan kenapa harus dilakukan? Pertanyaan ini bisa dijawab dengan analogi sebuah jalan. Jalan bernama Gatot Subroto terdiri dari beberapa rumah bernomor 01-08, dengan rumah nomor 08 adalah rumah Ketua RT yang memiliki tugas mengumumkan informasi apapun kepada seluruh rumah di wilayah Jl. Gatot Subroto.


Ketika rumah di wilayah itu makin banyak, tentu kemungkinan menimbulkan keruwetan dan kemacetan. Karena itulah kemudian diadakan pengaturan lagi, dibuat gang-gang, rumah yang masuk ke gang diberi nomor rumah baru, masing-masing gang ada Ketua RTnya sendiri-sendiri. Sehingga ini akan memecahkan kemacetan, efiesiensi dan optimalisasi transportasi, serta setiap gang memiliki previledge sendiri-sendiri dalam mengelola wilayahnya. Jadilah gambar wilayah baru seperti di bawah:


Konsep seperti inilah sebenarnya konsep subnetting itu. Disatu sisi ingin mempermudah pengelolaan, misalnya suatu kantor ingin membagi kerja menjadi 3 divisi dengan masing-masing divisi memiliki 15 komputer (host). Disisi lain juga untuk optimalisasi dan efisiensi kerja jaringan, karena jalur lalu lintas tidak terpusat di satu network besar, tapi terbagi ke beberapa ruas-ruas gang. Yang pertama analogi Jl Gatot Subroto dengan rumah disekitarnya dapat diterapkan untuk jaringan adalah seperti NETWORK ADDRESS (nama jalan) dan HOST ADDRESS (nomer rumah). Sedangkan Ketua RT diperankan oleh BROADCAST ADDRESS (192.168.1.255), yang bertugas mengirimkan message ke semua host yang ada di network tersebut.


Masih mengikuti analogi jalan diatas, kita terapkan ke subnetting jaringan adalah seperti gambar di bawah. Gang adalah SUBNET, masing-masing subnet memiliki HOST ADDRESS dan BROADCAST ADDRESS.


Terus apa itu SUBNET MASK? Subnetmask digunakan untuk membaca bagaimana kita membagi jalan dan gang, atau membagi network dan hostnya. Address mana saja yang berfungsi sebagai SUBNET, mana yang HOST dan mana yang BROADCAST. Semua itu bisa kita ketahui dari SUBNET MASKnya. Jl Gatot Subroto tanpa gang yang saya tampilkan di awal bisa dipahami sebagai menggunakan SUBNET MASK DEFAULT, atau dengan kata lain bisa disebut juga bahwa Network tersebut tidak memiliki subnet (Jalan tanpa Gang). SUBNET MASK DEFAULT ini untuk masing-masing Class IP Address adalah sbb:

CLASS	OKTET PERTAMA	SUBNET MAS DEFAULT	PRIVATE ADDRESS
A	1-127	255.0.0.0	10.0.0.0-10.255.255.255
B	128-191	255.255.0.0	172.16.0.0-172.31.255.255
C	192-223	255.255.255.0	192.168.0.0-192.168.255.255