Interface generally refers to an abstraction that an entity provides of itself to the outside. This separates the methods of external communication from internal operation (for example two different functions written in C language have the same interface if they have the same arrangements of arguments and the same type of return value, but the function body may be implemented in different way), and allows it to be internally modified without affecting the way outside entities interact with it, as well as provide multiple abstractions of itself. It may also provide a means of translation between entities which do not speak the same language, such as between a human and a computer. Because interfaces are a form of indirection, some additional overhead is incurred versus direct communication. The interface between a human and a computer is called a user interface. Interfaces between hardware components are physical interfaces. This article deals with software interfaces, which exist between separate software components and provide a programmatic mechanism by which these components can communicate.
Interfaces in practice
A piece of software provides access to computer resources (such as memory, CPU, storage, etc.) by its underlying computer system; the availability of these resources to other software can have major ramifications—sometimes disastrous ones—for its functionality and stability. A key principle of design is to prohibit access to all resources by default, allowing access only through well-defined entry points, i.e. interfaces.[citation needed] The types of access that interfaces provide between software components can include: constants, data types, types of procedures, exception specifications and method signatures. In some instances, it may be useful to define variables as part of the interface. It often also specifies the functionality of those procedures and methods, either by comments or (in some experimental languages) by formal logical assertions. The interface of a software module A is deliberately kept separate from the implementation of that module. The latter contains the actual code of the procedures and methods described in the interface, as well as other "private" variables, procedures, etc.. Any other software module B (which can be referred to as a client to A) that interacts with A is forced to do so only through the interface. One practical advantage of this arrangement is that replacing the implementation of A by another one that meets the same specifications of the interface should not cause B to fail—as long as its use of A complies with the specifications of the interface (see also Liskov substitution principle).
A computer network allows computers to communicate with many other and to share resources and information. The Advanced Research Projects Agency (ARPA) funded the design of the "Advanced Research Projects Agency Network" (ARPANET) for the United States Department of Defense. It was the first operational computer network in the world.
Network classification
The following list presents categories used for classifying networks.
Connection method
Computer networks can also be classified according to the hardware and software technology that is used to interconnect the individual devices in the network, such as Optical fiber, Ethernet, Wireless LAN, HomePNA, Power line communication or G.hn. Ethernet uses physical wiring to connect devices. Frequently deployed devices include hubs, switches, bridges and/or routers. Wireless LAN technology is designed to connect devices without wiring. These devices use radio waves or infrared signals as a transmission medium. ITU-TG.hn technology uses existing home wiring (coaxial cable, phone lines and power lines) to create a high-speed (up to 1 Gigabit/s) local area network. Wired Technologies Twisted-Pair Wire - This is the most widely used medium for telecommunication. Twisted-pair wires are ordinary telephone wires which consist of two insulated copper wires twisted into pairs and are used for both voice and data transmission. The use of two wires twisted together helps to reduce crosstalk and electromagnetic induction. The transmission speed range from 2 million bits per second to 100 million bits per second. Coaxial Cable – These cables are widely used for cable television systems, office buildings, and other worksites for local area networks. The cables consist of copper or aluminum wire wrapped with insulating layer typically of a flexible material with a high dielectric constant, all of which are surrounded by a conductive layer. The layers of insulation help minimize interference and distortion. Transmission speed range from 200 million to more than 500 million bits per second. Fiber Optics – These cables consist of one or more thin filaments of glass fiber wrapped in a protective layer. It transmits light which can travel over long distance and higher bandwidths. Fiber-optic cables are not affected by electromagnetic radiation. Transmission speed could go up to as high as trillions of bits per second. The speed of fiber optics is hundreds of times faster than coaxial cables and thousands of times faster than twisted-pair wire. Wireless Technologies Terrestrial Microwave – Terrestrial microwaves use Earth-based transmitter and receiver. The equipment look similar to satellite dishes. Terrestrial microwaves use low-gigahertz range, which limits all communications to line-of-sight. Path between relay stations spaced approx. 30 miles apart. Microwave antennas are usually placed on top of buildings, towers, hills, and mountain peaks. Communications Satellites – The satellites use microwave radio as their telecommunications medium which are not deflected by the Earth's atmosphere. The satellites are stationed in space, typically 22,000 miles above the equator. These Earth-orbiting systems are capable of receiving and relaying voice, data, and TV signals. Cellular and PCS Systems – Use several radio communications technologies. The systems are divided to different geographic area. Each area has low-power transmitter or radio relay antenna device to relay calls from one area to the next area. Wireless LANs – Wireless local area network use a high-frequency radio technology similar to digital cellular and a low-frequency radio technology. Wireless LANS use spread spectrum technology to enable communication between multiple devices in a limited area. Example of open-standard wireless radio-wave technology is IEEE 802.11b. Bluetooth – A short range wireless technology. Operate at approx. 1Mbps with range from 10 to 100 meters. Bluetooth is an open wireless protocol for data exchange over short distances. The Wireless Web – The wireless web refers to the use of the World Wide Web through equipments like cellular phones, pagers,PDAs, and other portable communications devices. The wireless web service offers anytime/anywhere connection.
Scale
Networks are often classified as Local Area Network (LAN), Wide Area Network (WAN), Metropolitan Area Network (MAN), Personal Area Network (PAN), Virtual Private Network (VPN), Campus Area Network (CAN), Storage Area Network (SAN), etc. depending on their scale, scope and purpose. Usage, trust levels and access rights often differ between these types of network - for example, LANs tend to be designed for internal use by an organization's internal systems and employees in individual physical locations (such as a building), while WANs may connect physically separate parts of an organization to each other and may include connections to third parties.
Functional relationship (network architecture)
Computer networks may be classified according to the functional relationships which exist among the elements of the network, e.g., Active Networking, Client-server and Peer-to-peer (workgroup) architecture.
Network topology
Computer networks may be classified according to the network topology upon which the network is based, such as bus network, star network, ring network, mesh network, star-bus network, tree or hierarchical topology network. Network topology signifies the way in which devices in the network see their logical relations to one another. The use of the term "logical" here is significant. That is, network topology is independent of the "physical" layout of the network. Even if networked computers are physically placed in a linear arrangement, if they are connected via a hub, the network has a Star topology, rather than a bus topology. In this regard the visual and operational characteristics of a network are distinct; the logical network topology is not necessarily the same as the physical layout. Networks may be classified based on the method of data used to convey the data, these include digital and analog networks.
Types of networks
Below is a list of the most common types of computer networks in order of scale.
Personal area network
A personal area network (PAN) is a computer network used for communication among computer devices close to one person. Some examples of devices that are used in a PAN are personal computers, printers, fax machines, telephones, PDAs, scanners, and even video game consoles. Such a PAN may include wired and wireless connections between devices. The reach of a PAN is typically at least about 20-30 feet (approximately 6-9 meters), but this is expected to increase with technology improvements.
Local area network
A local Area Network (LAN) is a computer network covering a small physical area, like a home, office, or small group of buildings, such as a school, or an airport. Current wired LANs are most likely to be based on Ethernet technology, although new standards like ITU-TG.hn also provide a way to create a wired LAN using existing home wires (coaxial cables, phone lines and power lines)[2]. For example, a library may have a wired or wireless LAN for users to interconnect local devices (e.g., printers and servers) and to connect to the internet. On a wired LAN, PCs in the library are typically connected by category 5 (Cat5) cable, running the IEEE 802.3 protocol through a system of interconnected devices and eventually connect to the Internet. The cables to the servers are typically on Cat 5e enhanced cable, which will support IEEE 802.3 at 1 Gbit/s. A wireless LAN may exist using a different IEEE protocol, 802.11b, 802.11g or possibly 802.11n. The staff computers (bright green in the figure) can get to the color printer, checkout records, and the academic network and the Internet. All user computers can get to the Internet and the card catalog. Each workgroup can get to its local printer. Note that the printers are not accessible from outside their workgroup.
Typical library network, in a branching tree topology and controlled access to resources
All interconnected devices must understand the network layer (layer 3), because they are handling multiple subnets (the different colors). Those inside the library, which have only 10/100 Mbit/s Ethernet connections to the user device and a Gigabit Ethernet connection to the central router, could be called "layer 3 switches" because they only have Ethernet interfaces and must understand IP. It would be more correct to call them access routers, where the router at the top is a distribution router that connects to the Internet and academic networks' customer access routers. The defining characteristics of LANs, in contrast to WANs (Wide Area Networks), include their higher data transfer rates, smaller geographic range, and lack of a need for leased telecommunication lines. Current Ethernet or other IEEE 802.3 LAN technologies operate at speeds up to 10 Gbit/s. This is the data transfer rate. IEEE has projects investigating the standardization of 40 and 100 Gbit/s.[3]
Campus area network
A campus area network (CAN) is a computer network made up of an interconnection of local area networks (LANs) within a limited geographical area. It can be considered one form of a metropolitan area network, specific to an academic setting. In the case of a university campus-based campus area network, the network is likely to link a variety of campus buildings including; academic departments, the university library and student residence halls. A campus area network is larger than a local area network but smaller than a wide area network (WAN) (in some cases). The main aim of a campus area network is to facilitate students accessing internet and university resources. This is a network that connects two or more LANs but that is limited to a specific and contiguous geographical area such as a college campus, industrial complex, office building, or a military base. A CAN may be considered a type of MAN (metropolitan area network), but is generally limited to a smaller area than a typical MAN. This term is most often used to discuss the implementation of networks for a contiguous area. This should not be confused with a Controller Area Network. A LAN connects network devices over a relatively short distance. A networked office building, school, or home usually contains a single LAN, though sometimes one building will contain a few small LANs (perhaps one per room), and occasionally a LAN will span a group of nearby buildings.
Metropolitan area network
A metropolitan area network (MAN) is a network that connects two or more local area networks or campus area networks together but does not extend beyond the boundaries of the immediate town/city. Routers, switches and hubs are connected to create a metropolitan area network.
Wide area network
A wide area network (WAN) is a computer network that covers a broad area (i.e. any network whose communications links cross metropolitan, regional, or national boundaries [1]). Less formally, a WAN is a network that uses routers and public communications links. Contrast with personal area networks (PANs), local area networks (LANs), campus area networks (CANs), or metropolitan area networks (MANs), which are usually limited to a room, building, campus or specific metropolitan area (e.g., a city) respectively. The largest and most well-known example of a WAN is the Internet. A WAN is a data communications network that covers a relatively broad geographic area (i.e. one city to another and one country to another country) and that often uses transmission facilities provided by common carriers, such as telephone companies. WAN technologies generally function at the lower three layers of the OSI reference model: the physical layer, the data link layer, and the network layer.
Global area network
A global area networks (GAN) (see also IEEE 802.20) specification is in development by several groups, and there is no common definition. In general, however, a GAN is a model for supporting mobile communications across an arbitrary number of wireless LANs, satellite coverage areas, etc. The key challenge in mobile communications is "handing off" the user communications from one local coverage area to the next. In IEEE Project 802, this involves a succession of terrestrial WIRELESS local area networks (WLAN).[4]
Virtual private network
A virtual private network (VPN) is a computer network in which some of the links between nodes are carried by open connections or virtual circuits in some larger network (e.g., the Internet) instead of by physical wires. The data link layer protocols of the virtual network are said to be tunneled through the larger network when this is the case. One common application is secure communications through the public Internet, but a VPN need not have explicit security features, such as authentication or content encryption. VPNs, for example, can be used to separate the traffic of different user communities over an underlying network with strong security features. A VPN may have best-effort performance, or may have a defined service level agreement (SLA) between the VPN customer and the VPN service provider. Generally, a VPN has a topology more complex than point-to-point. A VPN allows computer users to appear to be editing from an IP address location other than the one which connects the actual computer to the Internet.
Internetwork
An Internetwork is the connection of two or more distinct computer networks or network segments via a common routing technology. The result is called an internetwork (often shortened to internet). Two or more networks or network segments connect using devices that operate at layer 3 (the 'network' layer) of the OSI Basic Reference Model, such as a router. Any interconnection among or between public, private, commercial, industrial, or governmental networks may also be defined as an internetwork. In modern practice, interconnected networks use the Internet Protocol. There are at least three variants of internetworks, depending on who administers and who participates in them:
Intranet
Extranet
Internet
Intranets and extranets may or may not have connections to the Internet. If connected to the Internet, the intranet or extranet is normally protected from being accessed from the Internet without proper authorization. The Internet is not considered to be a part of the intranet or extranet, although it may serve as a portal for access to portions of an extranet.
Intranet
An intranet is a set of networks, using the Internet Protocol and IP-based tools such as web browsers and file transfer applications, that is under the control of a single administrative entity. That administrative entity closes the intranet to all but specific, authorized users. Most commonly, an intranet is the internal network of an organization. A large intranet will typically have at least one web server to provide users with organizational information.
Extranet
An extranet is a network or internetwork that is limited in scope to a single organization or entity but which also has limited connections to the networks of one or more other usually, but not necessarily, trusted organizations or entities (e.g., a company's customers may be given access to some part of its intranet creating in this way an extranet, while at the same time the customers may not be considered 'trusted' from a security standpoint). Technically, an extranet may also be categorized as a CAN, MAN, WAN, or other type of network, although, by definition, an extranet cannot consist of a single LAN; it must have at least one connection with an external network.
Internet
The Internet consists of a worldwide interconnection of governmental, academic, public, and private networks based upon the networking technologies of the Internet Protocol Suite. It is the successor of the Advanced Research Projects Agency Network (ARPANET) developed by DARPA of the U.S. Department of Defense. The Internet is also the communications backbone underlying the World Wide Web (WWW). The 'Internet' is most commonly spelled with a capital 'I' as a proper noun, for historical reasons and to distinguish it from other generic internetworks. Participants in the Internet use a diverse array of methods of several hundred documented, and often standardized, protocols compatible with the Internet Protocol Suite and an addressing system (IP Addresses) administered by the Internet Assigned Numbers Authority and address registries. Service providers and large enterprises exchange information about the reachability of their address spaces through the Border Gateway Protocol (BGP), forming a redundant worldwide mesh of transmission paths.
Basic hardware components
All networks are made up of basic hardware building blocks to interconnect network nodes, such as Network Interface Cards (NICs), Bridges, Hubs, Switches, and Routers. In addition, some method of connecting these building blocks is required, usually in the form of galvanic cable (most commonly Category 5 cable). Less common are microwave links (as in IEEE 802.12) or optical cable ("optical fiber"). An ethernet card may also be required.
Network interface cards
A network card, network adapter, or NIC (network interface card) is a piece of computer hardwareMAC addresses. designed to allow computers to communicate over a computer network. It provides physical access to a networking medium and often provides a low-level addressing system through the use of
Repeaters
A repeater is an electronic device that receives a signal and retransmits it at a higher power level, or to the other side of an obstruction, so that the signal can cover longer distances without degradation. In most twisted pair Ethernet configurations, repeaters are required for cable which runs longer than 100 meters.
Hubs
A network hub contains multiple ports. When a packet arrives at one port, it is copied unmodified to all ports of the hub for transmission. The destination address in the frame is not changed to a broadcast address.[5]
Bridges
A network bridge connects multiple network segments at the data link layer (layer 2) of the OSI model. Bridges do not promiscuously copy traffic to all ports, as hubs do, but learn which MAC addresses are reachable through specific ports. Once the bridge associates a port and an address, it will send traffic for that address only to that port. Bridges do send broadcasts to all ports except the one on which the broadcast was received. Bridges learn the association of ports and addresses by examining the source address of frames that it sees on various ports. Once a frame arrives through a port, its source address is stored and the bridge assumes that MAC address is associated with that port. The first time that a previously unknown destination address is seen, the bridge will forward the frame to all ports other than the one on which the frame arrived. Bridges come in three basic types:
Local bridges: Directly connect local area networks (LANs)
Remote bridges: Can be used to create a wide area network (WAN) link between LANs. Remote bridges, where the connecting link is slower than the end networks, largely have been replaced with routers.
Wireless bridges: Can be used to join LANs or connect remote stations to LANs
Switches
A network switch is a device that forwards and filters OSI layer 2datagrams (chunk of data communication) between ports (connected cables) based on the MAC addresses in the packets.[6] This is distinct from a hub in that it only forwards the packets to the ports involved in the communications rather than all ports connected. Strictly speaking, a switch is not capable of routing traffic based on IP address (OSI Layer 3) which is necessary for communicating between network segments or within a large or complex LAN. Some switches are capable of routing based on IP addresses but are still called switches as a marketing term. A switch normally has numerous ports, with the intention being that most or all of the network is connected directly to the switch, or another switch that is in turn connected to a switch.[7] Switch is a marketing term that encompasses routers and bridges, as well as devices that may distribute traffic on load or by application content (e.g., a Web URL identifier). Switches may operate at one or more OSI model layers, including physical, data link, network, or transport (i.e., end-to-end). A device that operates simultaneously at more than one of these layers is called a multilayer switch. Overemphasizing the ill-defined term "switch" often leads to confusion when first trying to understand networking. Many experienced network designers and operators recommend starting with the logic of devices dealing with only one protocol level, not all of which are covered by OSI. Multilayer device selection is an advanced topic that may lead to selecting particular implementations, but multilayer switching is simply not a real-world design concept.
Routers
A router is a networking device that forwards packets between networks using information in protocol headers and forwarding tables to determine the best next router for each packet. Routers work at the Network Layer of the OSI model and the Internet Layer of TCP/IP.
In cryptography, encryption is the process of transforming information (referred to as plaintext) using an algorithm (called cipher) to make it unreadable to anyone except those possessing special knowledge, usually referred to as a key. The result of the process is encrypted information (in cryptography, referred to as ciphertext). In many contexts, the word encryption also implicitly refers to the reverse process, decryptionsoftware for encryption” can typically also perform decryption), to make the encrypted information readable again (i.e. to make it unencrypted). (e.g. “ Encryption has long been used by militaries and governments to facilitate secret communication. Encryption is now commonly used in protecting information within many kinds of civilian systems. For example, in 2007 the U.S. government reported that 71% of companies surveyed utilized encryption for some of their data in transit.[1] Encryption can be used to protect data "at rest", such as files on computers and storage devices (e.g. USB flash drives). In recent years there have been numerous reports of confidential data such as customers' personal records being exposed through loss or theft of laptops or backup drives. Encrypting such files at rest helps protect them should physical security measures fail. Digital rights management systems which prevent unauthorized use or reproduction of copyrighted material and protect software against reverse engineering (see also copy protection) are another somewhat different example of using encryption on data at rest. Encryption is also used to protect data in transit, for example data being transferred via networks (e.g. the Internet, e-commerce), mobile telephones, wireless microphones, wireless intercom systems, Bluetoothautomatic teller machines. There have been numerous reports of data in transit being intercepted in recent years.[2] Encrypting data in transit also helps to secure it as it is often difficult to physically secure all access to networks. devices and bank Encryption, by itself, can protect the confidentiality of messages, but other techniques are still needed to protect the integrity and authenticity of a message; for example, verification of a message authentication codedigital signature. Standards and cryptographic software and hardware to perform encryption are widely available, but successfully using encryption to ensure security may be a challenging problem. A single slip-up in system design or execution can allow successful attacks. Sometimes an adversary can obtain unencrypted information without directly undoing the encryption. See, e.g., traffic analysis, TEMPEST, or Trojan horse. (MAC) or a One of the earliest public key encryption applications was called Pretty Good Privacy (PGP), according to Paul Rubens. It was written in 1991 by Phil Zimmermann and was purchased by Network Associates (now PGP Corporation) in 1997. There are a number of reasons why an encryption product may not be suitable in all cases. First, e-mail must be digitally signed at the point it was created to provide non-repudiation for some legal purposes, otherwise the sender could argue that it was tampered with after it left their computer but before it was encrypted at a gateway according to Paul. An encryption product may also not be practical when mobile users need to send e-mail from outside the corporate network.
As bandwidth demand grew the technology called Plesiochronous Digital Hierarchy (PDH) was developed by ITU-T G.702, whereby the basic primary multiplexer 2.048Mb/s trunks were joined together by adding bits (bit stuffing) which synchronised the trunks at each level of the PDH. 2.048Mb/s was called E1 and the hierarchy is based on multiples of 4 E1s.
E2, 4 x E1 - 8Mb/s
E3, 4 x E2 - 34Mb/s
E4, 4 x E3 - 140Mb/s
E5, 4 x E4 - 565Mb/s
The E3 tributaries are faster than the E2 tributaries, E2 tributaries are faster than the E1 tributaries and so on. These need to be synchronised with other tributaries, so extra bits are added called Justification bits. These tell the multiplexers which bits are data and which are spare. Multiplexers on the same level of the hierarchy remove the spare bits and are synchronised with each other at that level only. Multiplexers on one level operate on a different timing from multiplxers on another level. For instance, the timing between Primary Rate Muxes (combines 30 x 64Kb/s channels into 2.048Mb/s E1) will be different from the timing between 8Mbit muxes (combines up to 4 x 2Mb/s into 8Mb/s).
Inserting and dropping out traffic from different customers can only happen at the level at which the customer is receiving the traffic. This means that if a 140Mb/s fibre is near a particular site and a new customer requires a 2Mb/s link, then a whole set of demultiplexers are required to do this.
The Transmission System is traditionally seen as the link between main WAN switching centres. These Transmission Systems consist of large bandwidth highways that form the backbone to the network. They typically serve many customers each with their own requirements so the systems have to be reliable, resilient and flexible.
Rather than have two wires for every voice or data conversation, Time Division Multiplexing is used. ITU-T G.704 defines 32 channels of 64Kb/s to form 2.048Mb/s where channel 0 is used for framing. You will often see the standard G.703 mentioned with G.704, this is because G.703 defines the unframed physical interface coaxial (75 ohm) or RJ48 (120 ohm) used for the E1/T1 connection at the client premises. Channel 0 is for timing used to synchronise the multiplexers at each end of the link. Channels 1 to 15 and 17 to 31 are for voice or data whilst channel 16 is used for Common Channel Signalling (CCS) or Channel Associated Signalling (CAS). Every 3.91 microseconds 8 bits from one channel is sent down the line followed by 8 bits from the next channel during the next 3.91 microseconds and so on in a round robin fashion throughout all the channels, thus 32 channels are used once every 125 microseconds.
The connection at the end is either a 75 ohm coax, 120 ohm coax or a 150 ohm UTP/STP.
Management is very inflexible in PDH, so SDH was developed. Synchronous Digital Hierarchy (SDH) originates from Synchronous Optical Network (SONET) in the US. It includes capabilities for bandwidth on demand and is also made up of multiples of E1. STM-1 (155Mb/s) is 63 x E1, STM-4 (622Mb/s) is 4 x STM-1 and STM-16 (2.5Gb/s) is 4 x STM-4.
The benefits of SDH are:
Different interfaces or different bandwidths can connect (G708, G781).
Network topologies are more flexible.
There is flexibility for growth.
The optical interface is standard (G957).
Network Management is easier to perform (G774 and G784).
Existing PDH can interface into SDH. There are three G transmission series recommendations that are very important:
G.707 - SDH Bit Rates
G.708 - The SDH Network Node Interface.
G.709 - Synchronous Multiplexing structure.
With the exception of 8Mb/s, different PDH outputs are 'mapped' into Containers (C) and then into fixed size Virtual Containers (VC). When the VC is aligned in the Tributary Unit (TU) a Pointer is added which indicates the phase of the particular VC. TU's are then grouped, via Time Division Multiplexing (TDM), into Tributary Unit Groups (TUG).
The TUGs are collated into Administrative Units (AU) via more VCs where more pointers are added (these being fixed relative to the frame). The VCs and the pointers are incorporated into the section overhead of the Synchronous Transport Module (STM). One AU forms an STM-1, 4 AUs form an STM-4. You can also get STM-16 and STM-64.
Let us follow a 2Mb/s pipe through the hierarchy.
The 2Mb/s PDH first enters a container C12 which compensates for the varying speeds via the use of stuff bits (R). Stuff opportunities are identified by S1 and S2 and these are controlled by the control bits C1 and C2 respectively. If the C bits are are 0s then the corresponding S bits contain data and if the C bits are 1s then the S bits are not defined. In the diagram below, O represents Overhead channel bits and I represents Information bits
To create the VC12 a Path Overhead (POH) is added. The POH uses Bit Interleaved Parity (BIP) to monitor errors. In addition, there are fault indicators, Far End Block Error (FEBE), Remote Fail Indicator (RFI) and Far End Receive Failure (FERF). The Signal Label is normally set at 2 to indicate asynchronous data.
A pointer is added to the VC12 which defines the phase alignment of the VC12 and this changes during transmission. Phase variation can be due to Jitter (from regeneration and multiplexing equipment) and Wander (temperature differences within the transmission media). VC12s created by different multiplexers may not be synchronous so the TU adds a pointer at a fixed position within the TU. The value of the pointer indicates the start of the VC12. If the phase of the VC12 changes then the value of the pointer changes such that if data is running faster than the TU then the pointer value is increased and if the data speed is slower then the pointer value is decreased. This difference in speed can be up to one byte per frame in SDH.
The TU12 is multiplexed into a TUG 2 along with 2 other TU12s. This is achieved by interleving the bytes of each TU12 in turn. Next, seven TUG 2s are byte interleaved into a TUG 3 and then three TUG 3s can be byte interleaved to form the VC4 (see the SDH diagram above). You can see that 3 x 7 x 3 = 63 2Mb/s circuits can be contained in VC 4.
Fact: Millions of people "dream" of starting their own business in cyberspace. After all, this "final frontier" for entrepreneurs is churning out new business success stories faster than Ken Starr can blurt out "impeach!"
Fact: For millions of would-be cyberpreneurs, the dream will remain just that, a dream.
Why the sobering reality?
Well, the fact is, most people lack two key ingredients necessary to turn the dreams of their own business into reality. They lack 1) the time and 2) the knowledge.
Although their intentions are genuine when they start, as they quickly learn how much effort it takes to grow their own business, many fall back into the comfort of their 9-5 jobs. And hey, many people are happier knowing they have a check every week. There's certainly nothing wrong with that.
Then there are the entrepreneurs. The people who are willing to sacrifice a little security and lot of time for a chance at something more. What is that something more you ask? Well, here are just a few of the perks that successful entrepreneurs enjoy:
No boss.
Your own hours. (although they can be longer that a 9-5 job, they are more rewarding)
Unlimited income potential. (Nearly all "jobs" have salary caps, a business of your own means virtually limitless income potential!
So if you fall into the category of new entrepreneur, today's tip is dedicated to you.
Many of you are familiar with the rather ordinary path I took to get here. If you are not, I invite you to read about it in my recent press release: PR
And since I've been down the road (the cyberbusiness trail, that is) I'm sure I can help you. If you really want to grow a business of your own on the internet, print today's issue (and part 2 next week).
So how can I help? Well, for starters, I must tell you that the "time" ingredient I spoke of is up to you. I can't help you there. You'll have to scare up some extra time yourself. When I started out back in 1996, I sacrificed some time in front of the TV. (About a dozen sit-coms every week.) Heck, that was six hours right there! Wherever you can squeeze time out of your schedule is up to you. Just be sure the hours you set aside are uninterrupted blocks of time.
Okay, on with the show. What follows is a breakdown of the key steps a new cyberpreneur will need to make... Phase 1:
Setting Up For Success- Steps 1 through 3:
1. Keep your job - for now!
2. Connect with an ISP.
3. Get an email program. Step 1: Keep your job - for now!
There's no reason to put tons of pressure on yourself by quitting your day job. The time for that is when your business is making as much or more than your regular paycheck. This took me almost a year. Give yourself between 1 - 3 years. You'll know when the time is right. Actually quitting your job may seem far-fetched when you're starting out, but the time may come faster than you think.
Step 2: Connect with an ISP. (ISP stands for Internet Service Provider)
I started out on AOL. AOL is great for some things and I still have my AOL account to this day. I hardly ever use it for business purposes though. Simply put, it was just too slow, unreliable and the email interface still does not offer enough features to properly handle business email. (see step 3)
If you have never tried a true ISP, you should. You can locate one in your area by going to this URL: The List Step 3: Download a Free Email Program.
Once you connect to the net through an ISP you will be able to utilize a powerful email program. This is a basic necessity for any serious cyberbusiness owner. It will allow you to do things like mail to multiple addresses at once, sort messages automatically into multiple folders and autoreply to messages. I suggest starting with a free program such as Eudora Light or Pegasus Mail by David Harris.
Once you have downloaded your email program of choice, install it and start using it right away. Sample and become familiar with every feature. Your email program will become your new best friend.
Phase 2:
Moving Ahead with a Plan - Steps 4 through 6. Step 4: Decide what you are going to market.
That's right, you're going to have to "sell" to make money online. Whether you sell a product or a service, sales are what drives income. If you are uncomfortable with the idea of selling, I suggest you read the following article by yours truly. It explains how the internet can help even the most anti-sales person become a super-marketer: http://bizweb2000.com/sales.htm How to Sell
As far as WHAT you will market, they biggest secret is this: Sell something of your own! Whether you plan to write an information product or design web sites, it is important to develop at least one product or service that you control completely. For more on this, read http://bizweb2000.com/secret.htm The Big Secret Step 5: Marketing is the Key.
Okay, you've got an idea of what you plan on selling. But how do you actually sell it? That is the biggest obstacle for many new business owners. The fact is, anyone can learn to market effectively, especially online. For my best advice on "how" it's done, I'll refer you to a recent article I authored on the subject... http://bizweb2000.com/cyber2.htm The 2-Step
Pay particular attention to the section on ezines. If you are starting a business online, I cannot stress the value of regular email contact enough. An ezine is a great way to establish regular email contact with your prospects and customers. Learn more on the why and how of regular email contact at: http://bizweb2000.com/contact.htm Keep In Touch
Okay, I think that's enough to keep you busy a while! Next week, I'll continue with this tip by picking up on step 6: Setting up a Professional Web Site.
Then we'll move into the next phase and steps 7 -10. You'll learn tips and resources that will be helpful once you've started getting established, including... How to Leverage Technology and Automation.
The Keys to Growth.
And more...
1.Businesses that run with the internet media
all kinds of businesses that run on the internet called the online business. For example, if I open an online computer store, it means I'm running an online business
2.Online business is not easy
Do not be fooled by the lure of that business online is mudah.Karena on some websites that I have ever found, often found the writing "A month to get 50 jt with just typing". Remember, in addition you also need to type in the business. Today want that kind of get a money not easy. It takes sacrifice
3.Online business of many kinds
Online business world is growing rapidly and too many kinds. Starting from pay per click, pay to click, affiliate and others. There are free, there is also a need to pay in advance for the follow-up of business
4.Can be run from anywhere
Online business can be run from anywhere, which is important you have an internet connection. You can control your business when you're in the toilet, or when you're working in the office.
5.Relatively small capital
Online business capital is not much when compared to conventional business. At least you only need a website for this business
Being a technopreneur (entrpreneur in the field of IT) is not difficult, only two factors that needed to be a technopreneur succes.First is creativity. The second is consistency. In addition, too little science course.
Creativity here is one of creativity in a "learning target market". After that, other things to note is that we once.Remember business marketing technology that is still low in Indonesia will require an extra tool in the marketing (not just through flyers, banners , ad).
Doing business in the field of IT is the business community. That is, join a community the right (such as: mailing observers of information technology, public forums are hooked IT) will accelerate the familiar and trusted our business in the market.
Join the community can make us as a technopreneur more "aware" of the needs of the people in the community. Questions such as how to use computers that they wanted to learn, IT trends emerging in the market, and the need for easy to know if you join a community (the right course).
Thus, we can determine what a business focus that can be marketed in communities A, B, and others.Another can know "the customer wants", joined the community can accelerate the marketing of our business. Of course in those communities we must take an active role as members so that the people in the community to pay attention to us.
After interest arises and the relationship existed as between friends, we can begin to market our business. That and I'm sure it really will! If in my language, can be called that one key to success in running a business is to keep the friendship.
It can be concluded to be a necessary technopreneur things the following:
1. Carefulness in view momen Example: when the monetary crisis in 1998, at the time many companies out of business, Mr Timothy S by Zyrex her (company) go ahead even though promotion is because Mr. minimal.Mr Timothy saw as a moment to introduce and inform Zyrex community that the company is still "alive" that is believed to be          good company. Long-term benefit is the core ..
As a young professional, entrepreneurial spirit we need to develop. Develop your own business and pursue a career in business can be run simultaneously, as long as we maximize the potential of smart. As young professionals, we must determine our career goals. Yet, we can also explore entrepreneurial spirit within us. Manage your own business is now commonplace. If it's to maximize our potential, why not? But as a potential entrepreneur, the things we need to consider not only financial capital but also non-financial capital. What is meant by non-financial capital is the soul of our entrepreneurs in good enough or start a business because of the emotional distress caused by work under the control of others? Now, before you build a business, it helps us learn the tips below.
IMPORTANT THINGS BEFORE entrepreneurship
Having consideration. Try looking at SWOT analysis - Strength, Weakness, Opportunity, and Treat. All four criteria must always underlie every decision, including starting your own business.
Dare take the risk. Need extraordinary courage to entrepreneurship. So, do not immediately tempted fortune. The important thing is you want to work hard.
Able to build partnerships and partners who baik.Salah a business success factor is to build partnerships and business partners. This can be obtained at the office of social development or social life is also in general.
Involve people you trust, such sendiri.Apalagi family if you start a business with no large capital. Involving the family will minimize the risk because you are more familiar, so it could be more reliable. However, we must remain professional. We need to investigate whether the family members he has the criteria that we expect or not.
While entrepreneurship
How do we divide the time when still working in a company and have responsibilities, while the need to control their own company? Both these areas should not be sacrificed. What time do we have to work at the company, do the best. Then the rest of the time we use to control their own business. What is certain is that it requires us to work optimally. It was a risk that we must be responsible and professional in two areas in which we live. However, do not do the things that can interfere with operational offices in your company. So, do not try to do things that can cause negative impacts. We must remember that "the walls are also an ear".
ANO ENTREPRENEURS ARE EXPERT IN ANY FIELD, CAN?
An executive professionals do not need to know all fields in detail, but enough to read it. If an entrepreneur who leads all areas must be expert in all things, for example in accounting, computers, communications, and public relations, it was wasting time. We do not have time to learn and do everything. But not until we can not read the field. If you can not read, our weaknesses will be exploited others. For example, computerization. Maybe we are not too expert with the software, but we know that there is now a new system. We just need expert in one area and just "know" the other fields. There's no way someone expert in several fields. Maybe only one or two areas, but the other may not be as good as the first.
Polite entrepreneurship
All entrepreneurs must always start first with the study. Able to see the efforts of others, can also learn through books. A true entrepreneur does not stop to learn. The business world is always changing very quickly. It may be that certain products business this year boom, but instead dropped next year. So, we need to gel to see opportunities. But we need to know the rules too. It is not ethical if we imitate other people's products or trademarks of their scalp. Be creative to find new ways to develop business, but not to use any means just to profit.
Own business means that we must be prepared to work hard and not easily give up. We must dare to look at weaknesses and to improve self-discipline. So, keep improving.
Infopreneur comes from the word "information" and "entrepreneurs"
Infopreneur is the main business is selling information sharing and electronic,Create a blog / website,To market their own products / others
Definition :
Generally is an entrepreneurs who make money by selling information through the Internet
This profession existed before the Internet was growing rapidly. Usually they sell the information through an audio cd, cd rom, video, talk show, conference
With the Internet, they can sell the information through the Internet
The share of the broader market since the Internet can be accessed from around the world
What are the requirements
Website and blog
Presents useful information
High Traffic
Marketing
Search engine friendly
How
·Adsense
·Adwords for promotion
·Sell products or services
·Affiliate
·Referral
Formula
Content - Traffic - Presell - Monetize CTPM
Content (1)
Making websites
The goal: more towards a news provider, sms service, the discussion service, directory services, or general things that other people want
Website: Catalog, Online store, Forum
Services: services to create a website, the program
Content (2)
Providing advertising space With an existing script
Traffic
Search engines (XML)
Post Ads / adwords the right is the google adwords to get visitors that many (paid traffic) Banner interesting
A successful website: the website visited by many people (1000 visitors per day) Need a process to generate 1000 visitors
Presell
Provide product recommendations by comparing several products
Used on the website with the type Blogs, Reviews, Comparation
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"Because of that I liked and willing in the torture ... In the difficulties ... In the persecution and distress because of Christ ... Because If I am weak then I am strong (2 Corinthians 12:10)
