LAN (Local Area Network): Oktober 2009

Jumat, 09 Oktober 2009

Voice over Internet Protocol (VoIP) of Network

Voice over Internet Protocol (VoIP) is a general term for a family of transmission technologies for delivery of voice communications over IP networks such as the Internet or other packet-switched networks. Other terms frequently encountered and synonymous with VoIP are IP telephony, Internet telephony, voice over broadband (VoBB), broadband telephony, and broadband phone.

For over a decade now the prospect of using the internet to carry voice calls has been ‘next years technology’. Although there has not yet been any revolution in the way we route our phone calls, a number of enabling technologies, services and providers are now in place which can finally deliver a reliable, high-quality solution at very low cost.Most businesses and individuals who are serious internet users now have un-timed and effectively un-limited connection to the internet. Users can spend all day downloading data from the other side of the world at no added cost. And yet, when those same users make a phone call they are charged by the minute, whether the call is local, national or international. In practice the data may well travel over exactly the same route, on the same wires, owned by the same people. Only the billing mechanism and price is different. Wouldn’t it be better for the end user if the telephone call went with the internet traffic with the attendant price saving?Another attractive application for many businesses would be to connect home workers and sub-offices. The only on-going cost at each site would be the charge for an always-on internet connection. The remote sites could use the internet connection to log-in to the main office network and also run their telephones as extensions to the main office phone system.

A third use of Voice-over-IP technology is to replace the expensive telephone system that most companies require. The idea is to use existing computer hardware such as servers and Ethernet cabling to handle telephone traffic. Telephone system functions such as call-transfer and hold could be handled by software and telephone devices could just be plugged into a network point instead of dedicated wiring.
The three applications outlined above can be summarised as:

Long-distance call routing.
Point-to-point connections.
In-house PBX systems.

Benefits VoIP

Lower cost for long distance connections. The main emphasis of VoIP is the cost. With two locations are connected to the internet then the cost becomes very low conversation.
Utilizing the data network infrastructure already exists for the vote. Useful if the company already has a network. Where possible the existing network of VoIP networks can be built easily. Not required additional monthly fee for adding voice communication.
Use a smaller bandwidth than ordinary telephone. With advances Technologi bandwidth usage for voice now becomes very small. Data compression technique allows voice only takes about 8kbps bandwidth.
Allows combined with the local telephone network that already exists. With a network of VoIP gateways can be connected with the existing PABX office. Communication between the office can use a regular telephone.
Various types of VoIP networks can be combined into a large network. Examples in Indonesia is a VoIP Merdeka.
Variations use of existing equipment, for example from a PC connect to regular phone, IP phone handsets

VoIP voice quality is influenced by several parameters of bandwidth, packet loss rate and delay time occurred in the network. Bandwidth capacity is the availability of network resources in the form of bandwidth used to transmit data packets. Packet loss level is a parameter that states the amount the rate of errors that occurred during packet data transmission path from sender to recipient. Time delay is a parameter that states the timeframe required to send packages from sender to receiver.

Modem

Modem stands for Modulator comes from demodulator. Modulator is part of changing the information signal into the carrier signal (Carrier) and is ready to be sent, while the demodulator is the part that separates the information signal (which contain data or messages) of the carrier signal (carrier) that accepted that the information can be received well. Modem is a merger of both, it means the modem is a two-way communication tool. Each remote communications device of two-way commonly use the so-called "modern", such as VSAT, microwave radio, etc., but generally the more modern term known as the hardware is often used for communications on the computer.
Modem function is to change the signal digital voice signals and also this sebaliknya.Dewasa
modem has been developed with adequate facilities useful, for example, voice modem. With facilities. This voice modem, modem to change the function not only as a connecting to the internet, but more than that, the modem can a radio channel, audio, telephone conversations to
streaming video.

router network

router

Routers connect two or more logical subnets, which do not necessarily map one-to-one to the physical interfaces of the router. If you were really mean you could even go and block the person from being able to access their own router, and if that person was smart enough they would just use the reset button typically located on the back of the unit. Where’s the problem though? If the person doesn’t realize that they should be using any kind of wireless security or know to change the default password, then they will probably not notice that they can reset the router to see if that works. A router uses a routing table to decide where the packet should be sent so if the router cant find the preferred address then it will look down the routing table and decide which is the next best address to send it to.

Routers operate in two different planes
Control panel, in which the router learns the outgoing interface that is most appropriate for forwarding specific packets to specific destinations, Forwarding plane, which is responsible for the actual process of sending a packet received on a logical interface to an outbound logical interface. Edge Router: Placed at the edge of an ISP network, it speaks external BGP (eBGP) to a BGP, Subscriber Edge Router: Located at the edge of the subscriber's network, nter-provider Border Router: Interconnecting ISPs, this is a BGP speaking router that maintains BGP sessions with other BGP speaking routers.

Ethernet networking

Ethernet is a family of frame-based computer networking technologies for local area networks (LANs). The name comes from the physical concept of the ether. It defines a number of wiring and signaling standards for the Physical Layer of the OSI networking model, through means of network access at the Media Access Control (MAC) /Data Link Layer, and a common addressing format. Ethernet function is to translate the data from the computer to the Internet can be used as a network in the Internet.

Kamis, 08 Oktober 2009

Transmission Control Protocol/Internet Protocol (TCP/IP)

History of TCP / IP (Transmission Control Protocol / Internet Protocol) start of the birth of the ARPANET network digital switching package funded by DARPA (Defense Advanced Research Projects Agency) in 1969. TCP / IP is the standard communication data used by the community Internet in the process of exchange data from one computer to others in the Internet network.

Transmission Control Protocol/Internet Protocol (TCP/IP) be protocol exist in internet and world network. Protocol architecture model TCP/IP formed from 2 components that is Transmission Control Protocol (TCP) and internet protocol (IP). aim from TCP/IP build a connection delivers network (network), where usually called internetwork, or internet, prepare communication service delivers network that has physical form various. clear aim connect owner (hosts) in different network, or may be dissociated geographically in area vast.

Internet can diversified to be several group network, among others:

backbone: big network that connects to deliver another network. example: nsfnet that be network backbone world at America, ebone be network backbone at europe, and another.
Regional network, example: network delivers campus.
Network has commercial where prepare connection aims backbone to the customer.
Local network, example: network in a campus.

Aspect other important from TCP/IP form a standardization in communication.
every physical form a has technology that varies, so that need programming or special function to be used in communication. TCP/IP give special facilities on programming or special function from each physical network. so that architecture form from physical network disguised from user and network application maker. with TCP/IP, user not necessary again think network physical form to does a communication. To can identify host be need a address, called address IP (IP address). when a host has several network wares (interfaces), like router, so every interfaces must has a IP address unique. IP address consist from 2 parts, that is:

IP address = layer (layer) in protocol TCP/IP :
layer application is used in program to communicating to use TCP/IP. application example among others telnet and transfer file protocol (FTTP). interfaces that used to mutual communicating number port and socket. Layer transport give data delivery function according to end-to-end to side remote. application various can do communication according to together (simulaneously). protocol in layer transport most often used Transmission Control Protocol (TCP), where give data delivery function according to connection-oriented, data duplication prevention, congestion control and flow control. another protocol User Datagram Protocol (UDP), where give delivery function connectionless, stripe not reliabel. UDP many used in application that want speed tall towards data damage. Layer internetwork usually called also layer internet or layer network, where give “vitual network” in internet. Internet Protocol (IP) protocol most important. ip give function routing in network in data delivery. another protocol among others: ip, icmp, igmp, arp, rarp. Layer network interfaces is called also layer link or layer link data, be hardware in network. example: IEEE 802.2, X.25, ATM, FDDI and SNA.

Excellence TCP / IP :

Open Protocol Standard.
Independent of the physical network hardware.
How to be unique in addressing the global scale.
TCP / IP routing facilities and the types of Other services that enable applied the internetwork.
High levels of standard protocols.

Open Systems Interconnection (OSI) model is a reference for understanding data communications between two interconnected systems. OSI layer divides the communication process into seven layers. Each layer functions to perform specific functions to support the layer above it and also offers a service to layer underneath. Three bottom layer will focus on traffic pass through the network to a final system. Four top layer will play the final system to complete the communication process.

Through this article we will understand each layer of the OSI seven layers, including the functions and relationships between these layers. This will give you a general overview of the network process, which could later become a framework for more detailed understanding of computer networks.

In addition, this article will also discuss about the comparison between the OSI model with its theoretical model of TCP / IP is functional in nature. Although TCP / IP is used in the communication network prior to the adoption of the OSI model, but the TCP / OP also supports the functions and features similar to the arrangement of different layers.

Architecture of TCP / IP :

Physical Layer.

Physical layer in the OSI model defines the connectors and interface specifications, and also needs the medium (cable). Specifications electrical, mechanical, functions and procedures provided for the delivery of a bit stream on a computer network.

Components of the physical layer of them is:

Network Interface Card (NIC).
Hubs, repeaters and patch panel specifications.
Components of the wireless system patch panel specifications.
Parallel SCSI (Small Computer System Interface).
Connector design and functions of each pin.
Media adapter that connects to the physical interface.
Wiring system components.

In the LAN environment, category 5e UTP cable (unshielded Twisted Pair) is usually used in physical layer to connect the individual devices. Wiring with fiber optic cable typically used in the physical layer in a vertical relationship or Riser backbone. Bodies such as the IEEE, EIA / TIA / ANSI and other standards bodies to make the standard for this layer.

Network Access Layer

Has a function similar to the Data Link layer in the OSI. These layers organize the data distribution of data frames on the physical media used reliable. This layer usually provides services for the detection and error correction of transmitted data. Some examples of protocols that used in this layer is X.25 public networks, Ethernet for networking
Etehernet, network AX.25 Packet Radio etc.

Internet Layer

Defines how the relationship can occur between two parties who are on different networks such as the Network Layer of OSI. In the Internet network consisting of tens of millions of hosts and hundreds of thousands of local network, this layer served to ensure that a packet that is sent to find the goal wherever located. Therefore, this layer has a particularly important role in realizing internetworking covering vast areas (worldwide internet). Some of the important tasks in this layer are:

Addressing, which complement each datagram to the Internet address of the destination. Address of this protocol known as Internet Protocol Address (IP Address). Because addressing (addressing) the TCP / IP is at this level (software), then the TCP / IP network independent of the type of media and computer use.
Routing, which determines where the datagram will be sent in order to achieve the desired objectives. This function is the most important function of the Internet Protocol (IP). As the protocol is connectionless, the routing process is completely determined by the network. The sender has no control over the package he sent to reach the goal. Routers on a TCP / IP is a very decisive in delivering a datagram from the receiver to the destination.

Transport Layer
Defines the ways to perform data transmission between end-to-end in a reliable host. This layer ensures that the information received at the receiver side is the same as the information sent to the sender. Therefore, this layer has several important functions including:

Flow Control. Sending data that has been broken into these packages must be arranged in such a way that the sender not to send data at a speed that exceeds the ability of recipients to receive the data.
Error Detection. Sender and recipient also complement the data with some information that can be used to examine the data that is sent free of errors. If you found an error in the received data packet, then the recipient will not receive the data. The sender will resend the data packets that contain errors earlier. However, this can cause significant delays.

Application Layer
is the last layer in the architecture of TCP / IP that serves to define the applications that run on the network. Because of that, there are many protocols in this layer, according to the number of applications TCP / IP that can be run. Examples are SMTP (Simple Mail Transfer Protocol) for sending e-mail, FTP (File Transfer Protocol) to transfer files, HTTP (Hyper Text Transfer Protocol) for web applications, NNTP (Network News Transfer Protocol) for the distribution of news group and others. Each application generally uses TCP and IP protocols, so the whole family is named with the protocol TCP / IP.

TCP/IP architecture

TCP is a protocol that allows application programs to access / use the communication services are connection-oriented. TCP able to provide service delivery reliable (reliable) both are flow-controlled.

TCP characteristics

Connection-oriented, That kind of service that require prior connection. Analogues such as when we call

Data transmission mechanism using connection-oriented service

Reliable

Reliable means that data is transferred to the destination in a sequence as when sent. Transport services on the Internet, a reliable delivery of a sequence of unicast model. Example: TCP.

Owned by the reliability of this protocol due to several mechanisms. The following mechanisms:

Checksum: all TCP segments carrying checksum will be used by the recipient (receiver device) to check whether any errors were errors in the data or the header of TCP itself.
Duplicate Data Detection: TCP's ability to maintain each byte is received for these bytes are not experiencing a doubling (read: received more than once).
Retransmisson: TCP's ability to implement the scheme for the repeated delivery of the shipment data broken or missing.
Sequencing: TCP's ability to develop data segments that have been received. This will create a TCP can send data back to an application with the correct order
Timers: TCP uses two timers at once in data transmission. Two of the timer timer timer static and dynamic. Protocol will wait for the sender of the recipient within a certain time period for an "Acknowledge". If the timer period has expired, the sender can send back (Retransmit) segment that will be sent.

Type of Network Cable

Twisted pair cable

bnc connector

coaxcial cable

fiber optic

Type of network cable :

Twisted pair cable
coaxial cable
Fiber Optic

twisted pair cables there are two kinds of, first shielded with a wrapping membrane (STP) Shielded Twisted Pair, second unshielded sheath that does not have a wrapper (UTP) Unshielded Twisted Pair. This cable has the characteristics of a pair of wire-twist on one another in order to reduce electrical interference, can consist of two, three or more wire pairs, can spend up to 10-100 mbps signal, can only handle one data channel (baseband). twisted pair connection using RJ-11 connectors or RJ-45, STP is more resistant to interference than UTP and can operate at higher speeds up to 100 mbps, but it is more difficult to handle physically.

coaxial cable properties as follows, has a wide bandwidth for broadband communications.
kinds of coaxial cable, 10Base5 known, for the installation of backbone Ethernet network between buildings.

thin coaxial better known as RG-58, cheapernet, 10Base2, thinnet, for workstations and network topologies for the ring because BUS and physically manageable.

Fiber-optic communication is a method of transmitting information from one place to another by sending pulses of light through an optical fiber. The light forms an electromagnetic carrier wave that is modulated to carry information. First developed in the 1970s, fiber-optic communication systems have revolutionized the telecommunications industry and have played a major role in the advent of the Information Age. Because of its advantages over electrical transmission, optical fibers have largely replaced copper wire communications in core networks in the developed world.

Rabu, 07 Oktober 2009

Function of a Computer Network HUB

Function of a Computer Network HUB
Hub is a general term used to describe a central connection point for computers on the network. The basic functions performed by the hub is receiving signals from a computer and transmits to the other computer. Hub can be active or passive. A network hub is a fairly unsophisticated broadcast device. Hubs do not manage any of the traffic that comes through them, and any packet entering any port is broadcast out on all other ports. Since every packet is being sent out through all other ports, packet collisions result—which greatly impedes the smooth flow of traffic. A network hub or repeater hub is a device for connecting multiple twisted pair or fiber optic Ethernet devices together and thus making them act as a single network segment. Hubs work at the physical layer (layer 1) of the OSI model. The device is thus a form of multiport repeater. Repeater hubs also participate in collision detection, forwarding a jam signal to all ports if it detects a collision. Most hubs (intelligent hubs) detect typical problems, such as excessive collisions on individual ports, and partition the port, disconnecting it from the shared medium. Thus, hub-based Ethernet is generally more robust than coaxial cable-based Ethernet, where a misbehaving device can disable the entire collision domain. Even if not partitioned automatically, an intelligent hub makes troubleshooting easier because status lights can indicate the possible problem source or, as a last resort, devices can be disconnected from a hub one at a time much more easily than a coaxial cable. They also remove the need to troubleshoot faults on a huge cable with multiple taps.
Additional functions other than as a central connection point, hub provides the following capabilities:

workstation. increasing distance network (as a repeater function).
facilitate the addition, removal or transfer .
tolerance (insulation damage) provides a centralized service management (collection of information, diagnostics).
provides flexibility to support different interfaces.
Passive hubs simply act as a connection box; he split / separate the incoming signal to the transmitted to the entire network .

Hub is a general term used to describe a central connection point for computers on the network. The basic functions performed by the hub is receiving signals from a computer and transmits to the other computer. A hub can be active or passive. Active hubs act as repeaters regenerate and he sends the amplified signal. Passive hubs simply act as he shares the connection box / separate incoming signals to be transmitted to the whole is central to network.Hub star topology and allows the computers to be added or removed on the network with relative ease.

RJ45 connector functions:

tang crip

RJ45 connector

Function connector: Easily the replacement aircraft for telephone or facilitate removable and easy to be revoked without fear stung by the flow of electricity
If installed in accordance with installation instructions will save the phone bill up to 30%. By using this tool it will get an added value to communicate. jack (RJ) is a network of physical standards - both in construction and wiring pattern jack - to connect the telecommunications, data or equipment (commonly, a telephone jack) or computer networking equipment to services provided by local exchange service, long distance service, or network data in the case of a RJ-45 connector.

Technique is the cheapest and most satisfying is to use UTP cable. UTP cables are unshielded Twisted Pair stands, is the cable consisting of 4 pairs (blue, orange, green, and brown) wires are twisted according to certain rules and are used to transfer / receive data.
his cable consists of several types of

Cat 5 UTP, 100Base-T technology, the frequency of 16 MHz. Data bandwidth up to 100 Mbps (theoretical) .
UTP cat 5e, 1000Base-T technology, the frequency of 100 MHz. Achieve data bandwidth 1000 Mbps (theoretical) .
UTP cat 6, 1000Base-T technology, the frequency of 250 MHz. Data bandwidth to 2,500 Mbps (theoretical) .

rimp tools / Crimping tool is a tool for installing UTP cable into the RJ-45 connector / RJ-11 depending on needs. Various shapes is large with many functions, such as can cut the cable, peeling and so on. There is also the only dedicated to Crimp RJ-45 or RJ-11 only.

For the type of cross was used to connect directly between two PCs, or are generally used to connect between the hub. How to install also really easy, just like a straight type, pin is used also only have 4 pins, namely pins 1, 2, 3 and 6. What is different is the way pair. If the type of cross, pin 1 is connected to pin 3 on the other end, pin 2 to 6, pin 3 to pin 1 and 6 to 2. Practical way, at the end of the first pin you can set up standards for the type of "straight", whereas in the other end of the pin you set up standards for the type of "cross". Still confused? Here's how easy it is: The first tip:

young orange
old orange
green
blue
navy
dark green
brown
sepia

So at the other end must be made :

green
dark green
young orange
blue
navy
old orange
brown
sepia

It's a little more understanding? So here's position number 1, 2, 3 and 6 are exchangeable. Later when tested using the LAN tester, then later led 1, 2, 3 and 6 will be exchanged. If the type of straight running sequence, while there are cross type jumping. But who would have each led is lit all of the numbers 1 to 8.OK, congratulations to build computer networks.

Type of Computer Network

Topology STAR

Topology BUS

Topology RING

network has a different type of form each other and function and loss of that type.

Type of network consists of:
Topology Network Computer
Topology BUS topology using a single cable to the network, between client and server. benefits of the bus topology is the development of networks or the addition of new workstations can be done easily without disrupting the other workstations. weakness of the BUS topology when there is interference along the cable on another computer network center will be disturbed.

Topology Star

each workstation connected directly to the HUB/Connecting devices in a computer-computer network (LAN) to the server, especially the star-shaped network. Many have the hub port and every port filled with one computer. advantage of a separate cable for each workstation to the server, when there is interference at one point the cable disruption occurs only in the communication between the relevant workstation with a network server so that overall there is not interference. weakness requires huge funds and long cables.

Topology RING

all workstations and servers are connected to form a circle or ring pattern, each workstation or server will receive and pass information from one computer to another, if the address is appropriate it will be accepted if not then not received the information. weaknesses of each node in the network will always come to manage the information passed in the network, so that if an interruption occurs at a node the whole network is disrupted. excellence is not the collision or the collision of data transmission such as the BUS topology, because only one node can transmit data one time.

LAN (Local Area Network)

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