Selasa, 22 November 2011

DHCP for Newbie

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For those of you observers of computer network problems must have often heard the term DHCP. For those who do not understand about DHCP, so this time we will present a variety of answering questions about DHCP, especially for those who are beginners.
What is DHCP?DHCP stands for Dynamic Host Configuration Protocol.
What is the use of DHCP?The purpose of DHCP is huge in a computer network. DHCP is used for computers that are contained on a computer network can retrieve configuration (be it an IP address, DNS address etc.) to those from a DHCP server. The point with the DHCP it will be able to reduce the work in administering a network of large IP-based computer. Imagine if a computer network consisting of 1000 computers and you have to set the IP address on each computer manually. Sucks is not it?

 
Frequently Asked Questions Regarding DHCP (Dynamic Host Configuration Protocol)

    
Who created the DHCP? How do they create the DHCP?
    
DHCP is created and designed by Dynamic Host Configuration working group on the Internet Engineering Task Force (IETF). IETF is the organization itself that defines the various protocols in conjunction with the Internet. Furthermore, the definition of DHCP it self poured into a document RFC (Request for Comments) and then Internet Activities Board (IAB) review the status to later become a standard on the internet. As of March 1996, the status of DHCP is an Internet Proposed Standard Protocol and is Elective. Meanwhile BOOTP when it is Internet Draft Standard Protocol and is Recommended. To see more about the Internet standardization at the time, please access or read RFC1920.
    
How are they different DHCP compared to BOOTP and RARP?
    
Based on BOOTP and DHCP are still compatible with previous technology. The main difference is the BOOTP was designed for manual pre-configuration of the host information in a database server, while it used DHCP to provide dynamic allocation of network addresses and other important configuration for new hosts join the network. Additionally, DHCP allows a method of recovery and also the relocation of a network address via a mechanism leasing.RARP is a protocol used by Sun and other vendors which allows a computer to find its own IP number, which is one-parameter protocol parameters given to the client system by DHCP or BOOTP. RARP does not support other parameters and use them. A server is only able to serve a single LAN. Meanwhile, DHCP and BOOTP are designed so that they can be routed on the network.

    
What if the client IP address assigned automatically without using a DHCP server?
    
Theoretically this is possible, when the client or the computer may take any IP address for himself and then to broadcast a request to the other computers to see whether the IP address is already in use or not. Appletalk is designed with an idea like that and on Apple's MacTCP can be configured like this. However, the method of allocation of IP as it has several drawbacks, namely:

        
Computers that require permanent IP address can be turned off and it made him lose his IP address and IP address can be used by other computers. This can result in difficulty finding service problems that exist on the network and also the risk of security problems.

        
If giving IP address must be given by following a certain range, then this will cause problems because we have to determine its range on each computer. It will be led to hidden configuration errors and difficulties in replacing its range at a later date.

    
Can DHCP assigning an IP address into a static network?
    
Yes. This can be likened to that of each client in a computer network that implements DHCP will always receive the same IP forever. It's very possible and implemented according to RFC documents, it is an address allocation is done manually but centralized.

    
Can a BOOTP client boot from a DHCP server?
    
It could be as long as the DHCP server is specifically written to also handle BOOTP queries.

    
Can a DHCP client boot from a BOOTP server?
    
It could be as long as the DHCP client is written specifically to answer a message from a BOOTP server.

    
Can a DHCP server be a backup for another DHCP server?
    
You can have multiple DHCP servers in a network. During the DHCP servers are identical and have the same allocation for all clients in the network, the DHCP server if one dies, the configuration data can be retrieved from another DHCP server is still alive. It required a method of communication server-to-server on the DHCP servers.

    
Where DHCP defined?
    
You can read the document RFC1541, RFC1534 and RFC1533. To read it please you go to http://ds.internic.net/ds/dspg1intdoc.html

    
Where I can read and read it more broadly about this DHCP?
    
Feel free to address http://www.bucknell.edu/ ~ droms / dhcp / or to http://info.isoc.org/HMP/PAPER/127/html/paper.html or as usual, you can search in Google or Yahoo! with DHCP keyword tutorials.

    
What features are offered by DHCP?
    
DHCP server recognize three kinds of allocation, namely:

        
Manual allocation: in which the server administrator to make configuration on the server that records the MAC address of each computer and for each MAC address is set each of its IP address.

        
Automatic allocation: in which the server administrator to make configuration on the server which contains only the IP address that will be given to the client computer. Once an IP address associated with a MAC address on the computer, then he will be permanently associated with the MAC address of the server administrator to change it manually.

        
Dynamic allocation: this is like automatic allocation, but the server will record the status of lending IP addresses (leases) and will provide an IP address that was already expired lease to a DHCP client or any other computer.

Senin, 21 November 2011

Learn ERP basic

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Schematic UTP Cable (CAT5 / CAT5e)

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UTP Cable (CAT5 / CAT5e)
Connector can be used for CAT5 UTP Cable is RJ-45. To use a computer connection, known as 2 pieces of this type of UTP cable splicing, that is straight cable and crossover cable. The function of each different type of connection, straight cable used to connect the client to the hub / router, while the crossover cable used to connect the client to the client or in certain cases be used to connect the hub to hub.


Straight Cable
Connecting one end to the other end with one color, in terms of the number one tip is a tip number two at the other end. Actually, the color sequence of each cable is not a problem, but there are international standards that are used for straight cable :
Connection-based minimum standards EIA/TIA-568B RJ-45 Wiring Scheme:
Pair#2 is connected to pins 1 and 2 like this:
Pin 1 wire color: white/orange
Pin 2 wire color: orange
Pair#3 is connected to pins 3 and 6 like this:
Pin 3 wire color: white/green
Pin 6 wire color: green
While the rest of his cable is connected as follows:
Pair#1
Pin 4 wire color: blue
Pin 5 wire color: white/blue
Pair#4
Pin 7 wire color: white/brown
Pin 8 wire color: brown






Crossover Cable:

Basic Connection To UTP Crossover Cable

pin 1 -> pin 3, pin 2 -> pin 6, pin 3 -> pin 1, and pin 6 -> pin 2. Other pins left unconnected

Thin VS Thick Coaxial Cable

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Thick coaxial cable (Kabel Coaxial “gemuk”)
This type of coaxial cable specified by the IEEE 802.3 10Base5 standard, where the cable has an average diameter of 12mm, and usually are colored yellow; cable of this type commonly referred to as a standard ethernet or thick Ethernet, or simply abbreviated ThickNet, or even referred to as yellow cable.

This Coaxial Cable (RG-6) when used in the network have the specifications and rules as follows:

  •  Each end should be terminated with 50-ohm terminator (recommended to use a terminator that has been assembled, instead of using a single 50-ohm resistors 1 watt, for voltage dissipation resistor has a fairly wide).
  • Maximum of three segments with the connected equipment (attached devices) or a populated segments.
  • Every network card has an additional transmitter (external transceiver).
  • Each segment contains a maximum of 100 network devices, including repeaters in this case.
  • Maximum cable length per segment is 1640 feet (or about 500 meters).
  • The maximum distance between the segment is 4920 feet (or about 1500 meters).
  • Each segment should be grounded.
  • The maximum distance between tap or Taper from the main cable to the device (device) is 16 feet (about 5 meters).
The minimum distance inter-tap is 8 feet (about 2.5 meters).


Thin coaxial cable (Kabel Coaxial “Kurus”)


This type of coaxial cable widely used in amateur radio circles, especially for the transceiver that does not require a large power output. To be used as network devices, this type of coaxial cable must meet the standards of IEEE 802.3 10BASE2, where the average diameter of about 5mm and usually black or other dark colors. Each device (device) connected to a BNC T-connector. The cable type is also known as thin Ethernet or thinnet.

This type of coaxial cable, such as the type RG-58 A / U or C / N, if implemented with

Tconnector and terminator in a network, must follow the rules as follows:

  • Each end of the cable were given 50-ohm terminator.
  • The maximum length of cable is 1,000 feet (185 meters) per segment.
  • Each segment is a maximum of 30 network devices (devices)
  • Enough network card using onboard transceiver, do not need extra transceivers, except for the repeater.
  • Maximum there are 3 segments connected to each other (populated segments).
  • Each segment should be equipped with a ground.
  • Minimum length among the T-Connector is 1.5 feet (0.5 meters).
  • Maximum cable length in one segment is 1.818 feet (555 meters).
  • Each segment has a maximum of 30 devices connected.

Introduction of Cable Types in Network

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It feels incomplete, like "food without salt", when talking about the network does not touch on the wiring, because we know that the cable is one of the most important in terms of network connection, the following will briefly explain about the type and the type of cable used in a network .. though a bit long and not wide, but hopefully can be useful.

Each cable type has different capabilities and specifications, the introduction of cable types. There are three types of cables are known in general,

  •      UTP unshielded twisted pair,
  •      STP shielded twisted pair
  •      Coaxial cable.

Category for twisted pair (so far), that is:

Giving 1/2/3/4/5/6 category is a category of specifications for each of the copper wires and also for the jack. Each is a series of revisions to the quality of cable, quality cable wrapping (insulator) and also for the quality of "entanglement" (twist) of each pair of wires. In addition, to determine the amount of frequency that can pass on the cable facilities, and also the quality of the insulator so that it can reduce the effects of induction between the wires (noise can be suppressed in such a way).

It should be noted also, specifications between CAT5 and CAT5 enchanced have the same industry standard, but in CAT5e already equipped with insulation to reduce the effect of induction or electromagnetic interference. CAT5e cable can be used to connect networks of up to 1Gbps speeds.

As for coaxial cable, there are two types, that is thick coaxial cable (has a fairly large diameter) and thin coaxial cable (has a smaller diameter).

Learning what is FTP for Newbie

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File Transfer Protocol (FTP) is a protocol that serves for the exchange of files in a network that supports TCP / IP protocol. Two important things that exist in the FTP is an FTP server and FTP Client. FTP servers running the software used to exchange files, which are always ready to give FTP service when received requests from FTP clients. FTP client is a computer that is requesting a connection to the FTP server for the purpose of exchanging files (upload or download files). The purpose FTP server is as follows:
1. To download a data sharing.2. To provide indirect or implicit remote computer.3. Place To provide storage for the user.4. To provide reliable data transfer and efficient.
FTP is actually a way that is not safe to transfer files because the files are transferred without encryption first, but through clear text. Text mode is used for data transfer format is ASCII or Binary format. By default, ftp using ASCII mode for data transfer. Because of its delivery without encryption, then the username, password, data transferred, and the commands sent to the sniffing by using a protocol analyzer (sniffer). The solution used is to use SFTP (SSH FTP) FTP is based on using SSH or FTPS (FTP over SSL) so that the first data sent is encrypted (encoded).
FTP usually uses two ports are ports 20 and 21 and runs exclusively over TCP. Listen FTP server on port 21 for incoming connections from FTP clients. Typically port 21 for command port and port 20 to port data. On the FTP server, there are 2 modes of connection that is active mode and passive mode.
To using the ftp software you can download your own or just through comment. I usually use application to upload and download is WsFtp_LE, why do I use the application because the application was fairly simple and lightweight for use. so even though we have computers that minimum but we will be mild to run it.
How to use software that I think is quite simple wsftp you stay logged in and keep the premises continue to drag the files which you want to upload or download.
There we can use the default ftp usually pass comment on the windows. for its use are the steps. we go to the Start menu->> Run, continue typing the "command", then you specify the folder where the files you want to upload or where we put the files that we want to download.
After entering into a folder on your intent then typing
"ftp", for example ftp otopas.net and then that will connect to the server we're just like the others we also have to enter our ftp user and password. After you enter it you will go to the home our menu. Then your ftp can see the contents of the home is with the ls command  then you will see details of files and folders that we have. if you want to go into another folder. regular-usually the same crate that is by entering the command as cd an example is  cd public_html. after you go to the folder we want to go then we can just upload or download. to the commands if you do not already know then you live input only a "?" as an example ftp>? it will appear lish-lish the commands that can be used here. to upload their own files using  PUT command as an example ftp> put otopas.jpg it will immediately file uploads from your computer to the server. or you can also download files that exist on the server to our computer by using the get command as an example ftp> get deden.jpg and then the file will be copied from the server to our computer. when you have finished with all the process then you can close or exit the ftp service using the command bye.

Learn Simple BAsic of Network

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Network: the network (network) is a collection of two or more computer systems connected. There are many types of computer networks:
a. Local-Area Network (LAN) connected computers are in place adjacent to geografis (eg a building).
b. Wide-Area Network (WAN) that connects computers located in a remote place and connected by telephone lines or radio waves. in addition, a computer network can also be classified based on the following criteria:
Topology: connection settings between computer systems. There are a variety of topologies such as bus, star, and ring.
Protocol: the protocol defines a bunch of rules and signals used by computers on the network to communicate. The most popular LAN protocol is Ethernet. Other LAN protocol that is widely used is the IBM token-ring network.c. architecture: the network can be classified into the architecture of peer-to-peer or client / server.
NIC: NIC (network interface card) is an expansion board that is used so that computers can be connected to the network. Most NICs are designed for networks, protocols, and certain media. Commonly called the NIC LAN card (Local Area Network Card).
Backbone: Backbone is a channel or high-speed connection to the main path in a network. Bandwidth: Bandwidth to show the capacity to carry information. This term can be used in many ways: phone, cable networks, buses, radio frequency signals, and monitors. Most appropriate, bandwidth is measured in rounds per second (cycles per second), or hertz (Hz), ie the difference between the lowest and highest frequency that can be transmitted. But it is also frequently used measure of bits per second (bps).
Bridge: Bridge is a device that forwards traffic between network segments based on the data link layer information. This segment has the same network layer address. Every network should only have a major bridge.
DNS: DNS (domain name system) is a system that translates Internet domain, such as www.microsoft.com into Internet addresses, a series of numbers that look like 101.232.12.5. The term control related to the conventions for naming hosts on the Internet and how to handling these names.
Ethernet: Ethernet is a LAN protocol developed by Xerox Corporation in cooperation with DEC and Intel in 1976. Ethernet uses a bus or star topology and call for support for data transfer up to 10 Mbps. A newer version of Ethernet, called 100Base-T (or Fast Ethernet), supports data transfer up to 100 Mbps, and the newest version, Gigabit Ethernet, supports data transfer up to 1 Gigabit per second or 1000 Mbps.
Fast Ethernet: Fast Ethernet as usual, but with a speed faster data transfer, up to 100 mbps. It also called 100BaseT Ethernet.
Gateway: The term gateway refers to hardware or software that bridges the two applications or networks that are not compatible, so the data can be transferred between different computers. One example of the use of an email gateway, so that email exchanges can be performed on different systems.
GPS: GPS (Global Positioning System) navigation system uses satellite 24 MEO (medium earth orbit or middle earth orbit) around the earth and the recipients of the earth. Satellites orbiting at an altitude of approximately 12,000 miles above the earth and is able to circle the earth twice in 24 hours. GPS satellites continuously transmit digital radio signals containing satellite location data and time corresponding to the recipient. GPS satellites equipped with atomic clocks with a precision of one per one million seconds. Based on this information, the receiving station knows how long it will be used to send signals to the receiver on earth. The longer the time spent to get to the recipient, the more distant position from the satellite receiving station. by knowing the position of satellites, the receiver knows that the satellite is located at a certain position on the surface of the imaginary sphere centered on the satellite. By using three satellites, GPS can calculate the latitude and longitude based on the intersection of the third recipient of the imaginary sphere. By using four satellites, it can also be determined height. GPS was developed and operated by the U.S. Defense Department. GPS, originally known as NAVSTAR (Navigation System with Timing and ranging). Prior to the broader purposes, GPS is used to provide navigation capabilities at all times and in all weather for military land, sea and air forces. In addition to navigation and geographic positioning, GPS can also be used in between for mapping, forestry, mineral exploration, management of wild habitats, and migration control.
Host: Host is a computer system that is accessed by users who work in remote locations. Typically, this term is used if there are two computer systems connected by modems and telephone lines. The system contains data that is called the host, the system was used to assess from a distance is called the remote terminal. The term is also used to refer to a host computer connected to a TCP / IP, including the Internet. Each host has a unique IP address. In addition, the term also refers to the host computer services infrastructure. For example, many companies that host Web servers, which means that the company provides hardware, software, and communication channels required by the server, but the content server (data) is controlled by another party. ISP (Internet Service Provider): ISP (Internet service provider) is a provider of Internet services. Most ISPs have a network of servers (mail, news, Web), routers, modems are connected with the "backbone" of a permanent Internet and high speed. ISP customers can get an Internet connection with modem and telephone. To access the ISP's Internet subscribers have to dial into the network by pressing a certain number of ISPs.
Internet: The Internet is a global network connecting millions of computers. Since 1999 the Internet has had 200 million users worldwide, and this number is increasing rapidly. More than 100 countries connected to the Internet to exchange data, news, and other information. Every computer connected to the Internet is called the host.
ISDN: ISDN (Integrated Services Digital Network) is an international communications standard for sending voice, video and data over digital telephone lines or normal telephone wires. ISDN has a data transfer rate of 64 Kbps. Most ISDN lines offered by telephone companies which allows the two channels, called B channels (B channels). One line can be used for voice and another for the other and both have data transfer rates of 128 Kbps. Initial version of ISDN uses baseband transmission. Other versions of ISDN, the B-ISDN, uses broadband transmission and can support data transmission speed of 1.5 Mbps.
Protocol (protocol): Language or procedures used by a computer system with other systems so the two can be mutually berhububngan. To be able to communicate. Both systems must use the same protocol. PPP (Point To Point Protocol): Protocol TCP / IP that allows the relationship between the host and the network between the router with a router or can be used for the serial connection between two systems.
Repeater: A device installed at certain points in the network to update the signals transmitted in order to achieve the strength and shape of the original, in order to extend the distance that can be in use. This is needed because the signals have weakening and changes shape during transmission.
Router: A device that serves to connect a LAN to an internetworking / WAN and manage the distribution of data traffic in it. Routing: The process of determining a path in use to send data to a specific destination.
RJ-45: RJ-45 (Registered Jack-45) is an eight wire connector is typically used to connect computers to a local-area network (LAN), especially Ethernets. RJ-45 connector is similar to the RJ-11 connector used in telephone connections, but bigger.
Server: A functional unit for storing information and for managing a network server komputer.komputer will serve the whole client or worstation connected to its network.
TCP / IP: TCP / IP Transmission Control Protocol are two protocols that were developed by the U.S. military that allows computers on the network can be interconnected. IP is used to transfer data packets antarsimpul. TCP are used to verify the delivery of the client to the server. TCP / IP is the foundation of the Internet and can be found on all modern operating systems, like Unix and Windows.
Topology: The topology of computer networks is a form of connection settings between computer systems. there are a variety of topologies such as bus, star, ring.
UTP: UTP (Unshielded Twisted Pair) is a type of cable that consists of two wires was wrapped in a spiral. UTP cable is used in local-area networks (LANs) and telephone connections for cheaper. UTP cable is not as good as coaxial cable and fiber optics in terms of providing banwidth and resistance to interference.
VLAN: VLAN (virtual local-area network) is a computer network as if connected using the same wire even though it may be physically located in another part of the LAN. VLANs are configured through software and not hardware, which makes it very fleksible.Salah one advantage of VLANs is that when a computer is physically moved to another location, the computer remains on the same VLAN without any hardware reconfiguration.
VPN: VPN (virtual private network) is a private Internet connections are secure and encrypted to ensure that only entitled users can access it and transfer the data that do not be disturbed.
VSAT: VSAT (Very Small Aperture Terminal) earth stations that are used in satellite communications of data signals, voice, and video, except for television broadcasting. VSAT consists of two parts: a transceiver that is placed in the open so it can directly receive signals from a satellite and a device that is placed in the room to connect the transceiver and the end user communication device (end user), such as PC.Transceiver receive and send signals to the transponder satellites in outer space. The satellite sends and receives signals from an earth station computer that serves as a hub system. Any users that are connected with stasiunhub through the satellite, forming a star topology. hub to control all operations on the network. All transmissions for communication between the user must pass stasiunhub to kepengguna VSAT satellite and others. VSAT can transmit data up to speeds of 56 Kbps.
WAN: WAN wide area network is the computer that is connected at a remote place and relationship with a phone line or radio waves. See also LAN and network.
Wi-Fi: Wi-Fi Wireless Fidelity is the official trade name for IEEE 802.11b created by the Wireless Ethernet Compatibility Alliance (WECA). The term Wi-Fi to replace 802.11b as well as replacing the term Ethernet IEEE 802.3. Products certified by WECA as Wi-Fi can operate together even though made by different companies.
Workstation: On a computer network, computer workstations are connected with a local-area network (LAN). The term workstation is also used to refer to computers that are used for engineering applications (CAD / CAM), desktop publishing, software development, and other applications that require level of computing and graphics capabilities are quite tinggi.Workstation usually consists of a large graphics display with a high revolution, at least 64 MB of RAM, a built-in network support, and graphical user interface.Sebagian workstation also has a large storage devices such as disk drives, but the type specialized workstations, called diskless workstations, do not have a disk drive. The operating system is widely used for workstations are UNIX and Windows NT. Like the PC, most of the computer workstation is a single user, however, basically a workstation connected to the local area network, although it can also stand-alone system sebgian stand alone.
100BaseT: 100BaseT is another name that has a fast Ethernet transmission speeds up to 100 mbps. This type is more expensive than 100BaseT 10BaseT and more rarely used in local area network (LAN).
10Base2: 10Base2 is a type of standard Ethernet (IEEE802.3) for local area network (LAN). Standard 10 Base-2 (also called thinnet) using 50 ohm coaxial cable (RG-58A / U) with a maximum length of 185 meter.kabel is smaller and more flexible than those used for standard 10 Base 5. 10 Base-2 system operates at 10 Mbps and uses baseband transmission methods.
10 Base5: 10 Base-5 adalqh initial standards for Ethernet that uses coaxial cable. 10 Base5 name based on the fact that the maximum data transfer speed is 10 Mbps. Baseband transmission, and a maximum cable length is 500 meters. 10 Base5 also called Thick Wire or Net thick.
10BaseT: 10BaseT Ethernet is the most common type. These names show that the maximum transmission speed is 10Mbps. 10BaseT uses copper cable and a standard card to connect computers to local area network (LAN).
 

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