• Electronics engineering is a designing order which uses non-direct and dynamic electrical segments, (for example, semiconductor gadgets, particularly transistors, diodes and incorporated circuits) to plan electronic circuits, gadgets, Microprocessors/Microcontrollers and frameworks including VHDL Modeling for Programmable rationale gadgets and FPGAs.
• The control regularly additionally outlines inactive electrical parts, typically in view of printed circuit sheets.

• The first and most thing you should do as a starting step to be a professional engineer, is to get a degree in electronics and communication.
• If you want to be a professional engineer in Embedded System design or VLSI design (two most prominent field of electronics), there are institutes like CDAC, Vector India, VEDAIIT, Maven Silicon and many more which offer short term or long term courses in these fields. Not only that you also get the advantage of being placed in any leading electronics company.
• If you want to be a professional engineer in PCB designing, you need to have good working knowledge on design tools like CAD, ORCAD, and Eagle etc. You even need to have basic knowledge about PCB designing and mounting.
• If you want to be a professional engineer in VLSI or chip designing, you must have working knowledge in tools like Xilinx, Magic etc and of course must have good VLSI programming skills.
• It is not only the knowledge of software tools that can make you a professional engineer, but also good technical skills.
• These skills can be having practical knowledge in circuit mounting, soldering or PCB designing , practical knowledge in installation of networking products like routers, switches etc, practical knowledge of working with home automation devices like PLCs or practical knowledge of operating electronic equipments like Oscilloscopes, Wave Generators, Pulse Generators etc.
• As a fresher, you can apply for the position of trainee or intern at any reputed company. If you are GATE or NET qualified, you can always apply for the position of research fellowships at any Government recognized research institutes.
• A fresher with good theoretical knowledge about subjects related to electronics and communication can also opt for being a technical writer in the field of electronics and communication. Remember this might prove to be a great asset in increasing your exposure to the field of electronics.

• RX Lev Full means Mobile transmit the measurement report(SACCH multiframe) for every 480ms.
• This multiframe containes 104 TDMA frames, in 104 TDMA frames 4 TDMA frames for Decode the BSIC and remaining 100 TDMA frames for Average measurment of serving cell and neighbouring cell.
• This average measurment of 100 TDMA frames are RX Lev Full.

• DTX is a discontinuous trasmission, When the mobile conversation 40% of the time either Transmitter or Receive is idle. When DTX is ON, DTX will switch off the Transmitter or Receiver when they is no speech Pulses.
• Only few TDMA frames will transmit, the average of this TDMA frames is called RX Lev Sub, give you proper measurement of RX level.

• A link budget is accounting of all of the gains and losses from the transmitter, through the medium (free space, cable, waveguide, fiber, etc.) to the receiver in a telecommunication system.

• The BTS used in a GSM network comprises the radiotransmitter receivers. It is the defining element for each cell .
• The BTS communicates with the mobiles and the interface between the two is known as the Um interface with its associated protocols.
• The BSC forms the next stage back into the GSM network. It controls a group of BTSs, and is often co-located with one of the BTSs in its group.
• It manages the radio resources and controls items such as handover within the group of BTSs, allocates channels.
• It communicates with the BTSs over what is termed the Abis interface.
• The main element within the core network area of the overall GSM network architecture is the Mobile switching Services Centre (MSC).
• It provides registration, authentication, call location, inter-MSC handovers and call routing to a mobile subscriber.

• Current used in GSM telecom equipment is DC current.

• Logic is very simple. AC can’t be stored and DC can be stored.
• Example : Mobile is a GSM device in which DC is used to charge the batteries.

• GSM (Global System for Mobile Communications) is a second-generation digital mobile telephone standard using a variation of Time Division Multiple Access (TDMA).
• It is used for three digital wireless telephone technologies such as CDMA (Code Division Multiple Access), GSM and TDMA.
• GSM digitizes and compresses voice data, then sends it down a channel with two other streams of user data, each in its particular time slot.
• It works at either the 900, 1800 or 1,900MHz frequency bands.

• UDP vs TCP – TCP/IP means Transmission Control Protocol and Internet Protocol. It is the network model used in the current Internet architecture as well.
• Protocols are set of rules which govern every possible communication over a network.
• These protocols describe the movement of data between the source and destination or the internet. They also offer simple naming and addressing schemes.

• Support for a flexible architecture. Adding more machines to a network was easy.
• The network was robust, and connections remained intact until the source and destination machines were functioning.

• Lowest layer of the all.
• Protocol is used to connect to the host, so that the packets can be sent over it. Varies from host to host and network to network.

• Selection of a packet switching network which is based on a connectionless internetwork layer is called a internet layer. This layer which holds the whole architecture together.
• It helps the packet to travel independently to the destination.
• Order in which packets are received is different from the way they are sent.
• IP (Internet Protocol) is used in this layer.

• Delivering IP packets.
• Performing routing.
• Avoiding congestion.

• It decides if data transmission should be on parallel path or single path.
• Functions such as multiplexing, segmenting or splitting on the data is done by transport layer.
• The applications can read and write to the transport layer.
• Transport layer adds header information to the data.
• Transport layer breaks the message (data) into small units so that they are handled more efficiently by the network layer.
• Transport layer also arrange the packets to be sent, in sequence.

• The TCP/IP specifications described a lot of applications that were at the top of the protocol stack. Some of them were TELNET, FTP, SMTP, DNS etc.
  • TELNET is a two-way communication protocol which allows connecting to a remote machine and run applications on it.
  • FTP (File Transfer Protocol) is a protocol, that allows File transfer amongst computer users connected over a network. It is reliable, simple and efficient.
  • SMTP (Simple Mail Transport Protocol) is a protocol, which is used to transport electronic mail between a source and destination, directed via a route.
  • DNS (Domain Name Server) resolves an IP address into a textual address for Hosts connected over a network.
• It allows peer entities to carry conversation.
• It defines two end-to-end protocols : TCP and UDP
  • TCP (Transmission Control Protocol) : It is a reliable connection-oriented protocol which handles byte-stream from source to destination without error and flow control.
  • UDP (User-Datagram Protocol) : It is an unreliable connection-less protocol that do not want TCPs, sequencing and flow control. For Example One-shot request-reply kind of service.

• It operated independently.
• It is scalable.
• Client/server architecture.
• Supports a number of routing protocols.
• Can be used to establish a connection between two computers.

• In this layer does not guarantee delivery of packets.
• The model cannot be used in any other application.
• Replacing protocol is not easy.
• It has not clearly separated its services, interfaces and protocols.

• Switching is the most valuable asset of computer networking.
• Everytime in computer network you have access the internet or another computer network outside your immediate location, or your messages are sent through a maze of transmission media and connection devices.
• The mechanism for exchange of information between different computer networks and network segments is called switching in Networking.
• On the other words we can say that any type signal or data element directing or Switching toward a particular hardware address or hardware pieces.
• Hardware devices that can be used for switching or transferring data from one location to another that can use multiple layers of the Open Systems Interconnection (OSI) model.

• There are basically three types of switching methods are available.
  • Circuit Switching
  • Packet Switching
  • Message Switching

• Circuit-switching is the real-time connection-oriented system. In Circuit Switching a dedicated channel (or circuit) is set up for a single connection between the sender and recipient during the communication session.
• In telephone communication system, the normal voice call is the example of Circuit Switching. The telephone service provider maintain a unbroken link for each telephone call.
• Circuit switching is pass through three phases, that are circuit establishment, data transfer and circuit disconnect.

• The basic example of Packet Switching is the Internet. In Packet Switching, data can be fragmented into suitably-sized pieces in variable length or blocks that are called packets that can be routed independently by network devices based on the destination address contained certain “formatted” header within each packet.
• The packet switched networks allow sender and recipient without reserving the circuit. Multiple paths are exist between sender and recipient in a packet switching network.
• They does not require a call setup to transfer packets between sender and recipient.

• There are two type of Packet Switching connectionless or Connection-Oriented.

• It is also known as datagram switching. In this type of network each packet routed individually by network devices based on the destination address contained within each packet.
• Due to each packet is routed individually, the result is that each packet is delivered out-of-order with different paths of transmission, it depend on the networking devices like (switches and routers) at any given time.
• After reaching recipient location, the packets are reassemble to the original form.

• It is also known as virtual circuit switching. In this type of Networking packets are send in sequential order over a defined route.

• Message switching does not set up a dedicated channel (or circuit) between the sender and recipient during the communication session.
• In Message Switching each message is treated as an independent blocks.
• In this type of networking, each message is then transmitted from first network device to second network device through the internetwork i.e. message is transmitted from the sender to intermediate device.

• The intermediate device stores the message for a time being, after inspects it for errors, intermediate device transmitting the message to the next node with its routing information. Because the message switching networks are called store and forward networks in networking.

• Routing refers to establishing the routes that data packets take on their way to a particular destination.
• This term can be applied to data traveling on the Internet, over 3G or 4G networks, or over similar networks used for telecom and other digital communications setups. Routing can also take place within proprietary networks.

• Every network Routing protocol performs three basic functions:
  • Discovery – Identify other routers on the network.
  • Route Management – Keep track of all the possible destinations (for network messages) along with some data describing the pathway of each.
  • Path Determination – Make dynamic decisions for where to send each network message.

• Static Routing is a process in which we have to manually add routes in Routing table.

• No Routing overhead for router CPU which means a cheaper router can be used to do Routing.
• It adds security because only administrator can allow Routing to particular networks only.
• No bandwidth usage between routers.

• For a large network, it is a difficult task for administrator to manually add each route for the network in the Routing table on each router.
• The administrator should have good knowledge of the topology.
• If a new administrator comes, then he has to manually add each route so he should have very good knowledge of the routes of the topology.

• This method where the router is configured to send all packets towards a single router (next hop).
• It is very useful method for small networks or networks with a single entry and exit point.
• Basically this method used in addition to Static and/or Dynamic routing.
• It is generally used with stub routers. A stub router is a router which has only one route to reach all other networks.

• • Dynamic Routing makes automatic adjustment of the routes according to the current state of the route in the Routing table.
  • Dynamic Routing uses protocols to discover network destinations and the routes to reach it.
  • RIP and OSPF are the best examples of dynamic Routing protocol. Automatic adjustment will be made to reach the network destination if one route goes down.

Dynamic Routing

• A dynamic protocol have following features,
  • The routers should have the same dynamic protocol running in order to exchange routes.
  • When a router finds a change in the topology then router advertises it to all other routers.

• Easy to configure.
• More effective at selecting the best route to a destination remote network and also for discovering remote network.

• Consumes more bandwidth for communicating with other neighbours.
• Less secure than static Routing.

• An optical network is a type of data communication network built with optical fiber technology.
• It utilizes optical fiber cables as the primary communication medium for converting data and passing data as light pulses between sender and receiver nodes.
• An optical network is also known as an optical fiber network, fiber optic network or photonic network.

• There are various types of optical networking

• • Passive Optical Network
  • Active Optical Network
  • Synchronous Optical Network
  • Star networking

• This type of optical networking in which only single stand of fiber optics can take part and build a connection between the multiple computer networking clients from different areas is called as the passive optical networking.
• But some times customers complained that it can lower the rate of internet connection.

• Active optical network relies on electrically powered network equipment to distribute the signal, such as a switch or router.
• Usually, the data need optical-electrical-optical transformation in the Active optical network.
• Each signal leaving the central office is directed only to the customer for whom it is intended.

• This type of optical networking that deals with the data transmission is the synchronous optical networking.
• In this case optical networks can screen that all the data related to the information can pass easily from one place to another.
• It is more effective then the physical networking. It also observes the type of data; the type of data should be of one form and can be relayed properly.

• Networking carried out with the help of star networks is called as the star networking.
• Star networks deals with connection between the main computer systems to the other multiple computers over the network.
• They are also able to enhance the performance of the connection’s an the network.

• The optical networking depends upon the different components used in the optical networks such as the fiber optical cables.
• In optical networking with the help of fiber optics user scan deliver the date between two points at higher speed with similar to that of the light.
• Core is the main source of transmission in the optical networking. These cores are packed in a special type of layer which maintains the light signals in it. This wrapping also prevents the light to move outward from the cores of fiber optics.
• This step really prevents the data losing during transmission. According to this optical networks works on large distances and facilitate the users at long areas.

• Optical networks have three important attributes:
  • speed,
  • range,
  • capacity.
• Optical networking reduces latency between endpoints on the network. Where an electric current moves data at about 10% of the speed of light around 18,600 miles per second or 30,000 kilometers per second optical signals in fiber optic cable travel 10 times faster, at the speed of light 186,000 miles per second or 300,000 kilometers per second.
• Optical networks can also move more data across a cable at longer distances: Using electronics and copper, speeds top out at around 100 Gbps over short distances.
• Fiber can move data at 100 Gbps over a single data channel and across multi-kilometer distances and even further with amplification.
• Even greater speeds can be obtained by dividing a single optical cable into multiple data channels.

• Authorization is a security mechanism to determine access levels or user/client privileges related to system resources.
• Including files, services, computer programs, data and application features.
• This is the process of granting or denying access to a network resource which allows the user access to various resources based on the user’s identity.
• There are two types of authorization
  • Server-side Authorization
  • Client-side Authorization

• The server has three authorization modes. Depending on the authorization mode we choose, the server will decide if it accepts or declines an incoming invocation.

• This is the simplest type of authorization. No authorization will be performed.

• A client will be allowed to use a grid service if the client’s identity is the same as the service’s identity.

• A gridmap is a list of ‘authorized users’ akin to an ACL (Access Control List).
• When this type of authorization is used, only the users that are listed in the service’s gridmap may invoke it.

• This allows the client to figure out when it will allow a grid service to be invoked.
• This might seem like an odd type of authorization, since authorization is generally seen from the server’s perspective (“Do I allow client FOO to connect to grid service BAR?”).
• However, in GSI, clients have every right to be picky about the services they can access.

• No authorization will be performed.

• The client will authorize an invocation if the service’s identity is the same as the client.
• If we use both client-side and server-side Self authorization, a service can be invoked if and only if its identity matches the client’s.

• The client will authorize an invocation if the host returns an identity containing the hostname.
• This is done using host certificates.

A port has the following characteristics −

• External devices are connected to a computer using cables and ports.
• Ports are slots on the motherboard into which a cable of external device is plugged in.
• Examples of external devices attached via ports are the mouse, keyboard, monitor, microphone, speakers, etc.

• A port number is the logical address of each application or process that uses a network or the Internet to communicate.
• A port number uniquely identifies a network-based application on a computer.
• Each application/program is allocated a 16-bit integer port number.
• This number is assigned automatically by the OS, manually by the user or is set as a default for some popular applications.

• Protocol is a special set of rules for communication data.
• Network protocol = Rules and conventions/conditions for communication between network devices.
• Network protocols defines the mechanism of devices to identify and establish the connections between each other + formatting rules that specify how data is packaged into messages sent and received.

• A Media Access Control (MAC) address is a 48-bit address stored in the network Interface card.
• It is used for communication between two hosts in an Ethernet environment.
• It is nothing but a hardware /physical address of a computer.
• A MAC address is supposed to be globally unique and this will not be duplicated.
• The 48 bit contains – First 24 bits ( User ID -> Card Buyer ID ) + second 24 bits (card manufacturer)
• The address is written in the form of 12 hexadecimal digits. For example, consider the following MAC address:
  • D8-D3-85-EB-12-E3

• Every hexadecimal character represents 4 bits, so the first six hexadecimal characters represent the vendor (in this case, Hewlett Packard).

• Four levels of addresses are used in an internet employing the TCP/IP protocols:
  • Physical Addresses
  • Logical Addresses
  • Port Addresses
  • Specific Addresses

• Click the Network Icon on Taskbar
• Click the connected network and click the properties which are shown in the figure

• The network setting window open and shows the mac address.

• Open command prompt and type getmac to get the mac address

• Navigate to Control Panel > Network and Internet > Network Connections
• Right click the connection and click status within the dropdown

• Click Details buttons in the status window
• Then the Network Details windows open and shows the MAC address(Physical address)

• Open command prompt and type ipconfig /all (have a gap between g and /).

• Spoofing is that the act of disguising a communication from an unknown resource as being from a well-known, trusted resource.
• Spoofing will apply to emails, phone calls, and websites, or will be a lot of technical, like a pc spoofing an IP address, Address Resolution Protocol (ARP), or Domain name System (DNS) server.
• Spoofing will be used to gain access to a target’s personal information, describe malware through infected links or attachments, bypass network access controls, or distribute traffic to conduct a denial-of-service attack.
• Spoofing is usually the means a vulgar actor gains access so as to execute a bigger cyber attack like a complicated persistent threat or a man-in-the-middle attack.
• Successful attacks on organizations will cause infected pc systems and networks, data breaches, and/or loss of revenue-all vulnerable to have an effect on the organization’s public reputation.
• Additionally, spoofing that ends up in the rerouting of web traffic will overwhelm networks or lead customers/clients to malicious sites aimed at stealing info or distributing malware.

• Email spoofing is that the fake of an email header so the message seems to have originated from somebody or somewhere apart from the particular source.
• Email spoofing may be a plan of action utilized in phishing and spam campaigns because people are more likely to open an email after they assume it’s been sent by a legitimate source.
• The goal of email spoofing is to need recipients to open, and probably even answer, a solicitation.

• IP (Internet Protocol) forms the third layer of the ISO model. It is the network protocol which is used for the transmission of messages over the internet. Every email message sent has details in the message header of the IP address of the sender (source address). Hackers and scammers alter the header details to mask their true identity by editing the source address. The emails then look to have been transmitted by a trusted source. There are two types of IP spoofing.
  • Man in the Middle Attacks
  • Denial of Service (DoS) Attacks

• Caller ID spoofing is when a caller with intent fakes the information transmitted to your caller ID display to disguise their identity.
• Spoofing is often used as part of an attempt to trick someone into giving away valuable personal information so it can be used in fraudulent activity or sold illegally, but also can be used legitimately, for example, to display the toll-free number for a business.

• ARP poison routing (APR) or ARP cache poisoning, a method of attacking an Ethernet LAN by updating the target computer’s.
• ARP cache with both a fake ARP request and reply packets in an effort to change the Layer 2 Ethernet MAC address (i.e., the address of the network card) to one that the attacker can monitor.
• Because the ARP replies have been fake, the target computer sends frames that were meant for the original destination to the attacker’s computer first so the frames can be read.
• A successful APR attempt is invisible to the user.

• DNS (Domain Name System) servers resolve URLs and email addresses to corresponding IP addresses.
• DNS spoofing allows attackers to distract traffic to a different IP address, leading victims to sites that extent malware.

• Website spoofing means when a website is designed to copycat an existing site known and/or trusted by the user.
• Attackers use these sites to gain login and other personal information from users.

• IP stands for Internet Protocol which is the communications protocol of digital message formats and rules for exchanging messages between computers across a single network or a series of interconnected networks, using the Internet Protocol Suite (often referred to as TCP/IP
• Internet Protocol is connectionless and unreliable protocol. It ensures no guarantee of successfully transmission of data.
• Messages are exchanged as datagrams, also known as data packets or just packets.
• IP consisting of four abstraction layers : link layer (lowest), Internet layer, transport layer and application layer (highest).

• The Domain Name System (DNS) is the phonebook of the Internet. Humans access information online through domain names, like wikitechy.com. Web browsers interact through Internet Protocol (IP) addresses. DNS translates domain names to IP addresses so browsers can load Internet resources.
• Each device connected to the Internet has a unique IP address which other machines use to find the device. DNS servers eliminate the need for humans to memorize IP addresses such as 192.168.1.1 (in IPv4), or more complex newer alphanumeric IP addresses such as 2400:cb00:2048:1::c629:d7a2 (in IPv6).
• The DNS uses TCP Port 53 for zone transfers, for maintaining coherence between the DNS database and the server.

• DND means Do Not Disturb.This is an initiative by TRAI (Telecom Regulatory Authority of India) to save consumers from unsolicited calls/SMS.
• Register with the service provider’s Do No Disturb registry to avoid receiving unwanted telemarketing calls and messages.
• In turn the service provider register your number at the National Do Not Call (NDNC) registry within 45 days.
• Telemarketers have to verify the calling number list in the NDNC registry before making a call.
• So rest assured, the telemarketers will not trouble you else they will be fined for calling you.

• It allows phone users to disable audible ringing for incoming calls.
• When DND is enabled, incoming calls do not ring on the phone, however there is visual alerting and the call information displays, and a call can be answered if desired.
• When a phone calls in the DND state, the message “Ring out DND” displays on the calling phone that indicate the target phone is in the DND state.

• DHCP (Dynamic Host Configuration Protocol) is a protocol used to provide quick, automatic, and central management for the distribution of IP addresses within a network.
• DHCP is also used to configure the proper subnet mask, default gateway, and DNS server information on the device.
• DHCP allows hosts to obtain required TCP/IP configuration information from a DHCP server.

• A DHCP server is used to concern single IP address and automatically configure other network information.
• Maximum the home and small businesses, the router acts as the DHCP server. In large networks, a single computer might act as the DHCP server.
• A device (the client) requests an IP address from a router (the host), after which the host assigns an available IP address to allow the client to communicate on the network.
• Once a device is turned on and connected to a network that has a DHCP server, it will send a request to the server, called a DHCPDISCOVER request.
• After the DISCOVER packet reaches the DHCP server, the server goes to hold on to an IP address that the device can use, and then offers the client the address with a DHCPOFFER packet.
• Once the offer has been made for the chosen IP address, the device responds to the DHCP server with a DHCPREQUEST packet to accept it, after which the server sends an ACK that’s used to confirm that the device has that specific IP address and to define the amount of time that the device can use the address before getting a new one.
• If the server decides that the device cannot have the IP address, it will send a ACK.

• Ensuring cybersecurity requires the coordination of efforts throughout an information system, which includes:
  • Network security
  • Application security
  • Endpoint security
  • Data security
  • Identity management
  • Database and infrastructure security
  • Cloud security
  • Mobile security
  • Disaster recovery/business continuity planning
  • End-user education
• The most difficult challenge in cyber security is the ever-evolving nature of security risks themselves.
• The traditional approach has been to focus resources on crucial system components and protect against the biggest known threats, which meant leaving components undefended and not protecting systems against less dangerous risks.
• Today, this approach is insufficient, as the threats advance and change more quickly than organizations can keep up with. As a result, advisory organizations promote more proactive and adaptive approaches to cyber security.

• Ransomware is a type of malware that involves an attacker locking the victim’s computer system files — typically through encryption — and demanding a payment to decrypt and unlock them.
• Malware is any file or program used to harm a computer user, such as worms, computer viruses, Trojan horses and spyware.
• Social engineering is an attack that relies on human interaction to trick users into breaking security procedures in order to gain sensitive information that is typically protected.
• Phishing is a form of fraud where fraudulent emails are sent that resemble emails from reputable sources; however, the intention of these emails is to steal sensitive data, such as credit card or login information.

• A whitelist is a list of e-mail addresses or domain names from which an e-mail blocking program will allow messages to be received.
• The list can be gradually compiled over a period of time, and can be edited whenever the user wants.
• When a whitelist is used, all entities are denied access, except those included in the whitelist.

• A network administrator may be configure a firewall with a whitelist that allows only specific IP addresses to access the network.
• A protected directory within a website uses whitelist for the purpose of provide limit access to certain IP addresses.
• Some e-mail system users use whitelist for receiving only accept messages from the e-mail addresses.
• Programmers can use whitelists within a program to ensure only certain objects are modified.

• An end-user asks their browser to make a secure connection to a website
• The browser obtains the IP address of the site from a DNS server then requests a secure connection to the website.
• To initiate this secure connection, the browser requests that the server identifies itself by sending a copy of its SSL certificate to the browser.
• The browser checks the certificate to ensure:
  • That it is signed by a trusted CA.
  • That it is valid – that it has not expired or been revoked.
  • That it confirms to required security standards on key lengths and other items.
  • That the domain listed on the certificate matches the domain that was requested by the user.
• When the browser confirms that the website can be trusted, it creates a symmetric session key which it encrypts with the public key in the website’s certificate. The session key is then sent to the web server.
• The web server uses its private key to decrypt the symmetric session key.
• The server sends back an acknowledgement that is encrypted with the session key.
• From now on, all data transmitted between the server and the browser is encrypted and secure.

• Hardware firewalls are systems that are independent of the computers they protect that filter the Internet as information passes into a computer.
• Most broadband Internet routers have their own firewall built in.
• In general, hardware firewalls work by examining the data that flows in from the Internet and verifying whether that information is safe.
• The ZyXEL ZyWALL, which is a Unified Security Gateway with a firewall and other security features.
• Cost: $100 to ~$500
• NAT, DCHP, Email Notification.
• Easier for computers to locally share folders/Printers.
• Additional function available & can protect other devices.

• Software firewalls are designed to protect a computer by blocking certain programs from sending and receiving information from a local network or the Internet.
• The Windows Firewall, an example of a firewall software program included with Microsoft Windows.
• Cost: Free to $30 per computer.
• Each machine need to be configured.
• Firewall may be interfere with local network sharing.