Technology

According to Wikipedia

Voice-over-Internet Protocol (VoIP) is a methodology and group of technologies for the delivery of voice communications and multimedia sessions over Internet Protocol (IP) networks, such as the Internet. Other terms commonly associated with VoIP are IP telephony, Internet telephony, voice over broadband (VoBB), broadband telephony, IP communications, and broadband phone service.

What is VoIP?

Voice over Internet Protocol (VoIP) is a technology which is used to carry voice communication over internet protocol (IP) network. Basically it means your voice (analog format) get transmitted over digital network. VoIP is often referred to as IP telephony (IPT) because it uses Internet protocols to make enhanced voice communications possible. The Internet protocols are the basis of IP networking, which supports corporate, private, public, cable, and even wireless networks.

Before digital networking took off, everyone had to use plain old telephone service. It runs over a network called the PSTN, or public switched telephone network.

Existing phone systems are driven by a very reliable but somewhat inefficient method for connecting calls called circuit switching. Data networks do not use circuit switching. Instead, data networks simply send and retrieve data as you need it. This is called packet switching.(more)

Why to use?

For customers, the costs related to the regulated circuit-switched PSTN remain much higher than they need to be. Consumers as well as companies have to rely on telephone system on a daily basis for communication. The good news is that VoIP is an alternative that can greatly reduce or eliminate old telephone system related costs. You can call your co-worker who is in office / outside office over IP network.

What you require?

If you want to establish the call within your local network and your VoIP server in within network, then there is no need of internet connection. But either the VoIP server is outside the network or you want to establish call outside the local network then, then internet connection is must.
There are 3 ways you can establish a VoIP call,

1. Using ATA: ATA ( Analog Telephone Adaptor), it allows standard PSTN phone to your computer or directly to internet. ATA convert voice (analog) to digital data which is ready to send over network.
2. IP Phones: These are phones which look like normal phones with handsets and buttons. But instead of having RJ11 phone connector, it has RJ45 Ethernet connector. IP phone directly connect to network and have necessary application to make the VoIP call.
3. Computer/Phone: This is easiest way to use VoIP. You just need the computer/Phone which is connected to network, headset and application required to make VoIP calls. Some free application are also widely used which provides such service. E.g. Skype, Viber etc. Also there is application named softphone which gives you an ability to connect your VoIP server and make call, just like you normal phones. It can be installed on phone/ computer.

So how we do it?

We provide the facility to make VoIP call within the local network on LAN side of controller. We have the VoIP server running on the controller and controller host the SIP extension and password mapped to particular username.

We prefer softphone to establish a call, as its free and available for phone and computer, thus eliminating the cost of hardware.

So here is how it's works,

1. User connects to wireless/wired network through his phone/computer, on which softphone is installed.
2. If softphone is not configured, then it has to be configured with SIP Extension, Password and VoIP server address
3. After configuration, softphone tries to authenticate itself with server.
4. After successful authentication, softphone get connected to local network.
5. By using same mechanism other softphones get registered to network.
6. So after, if somebody requires to call anyone, he simply dials other's extension number from his softphone and the other's phone starts ringing.
7. Since we provide this facility over wireless also, it’s easy to call roaming person in same premises.
8. We also provide facility to setup Conference Bridge.

Default gateways

Default gateways serve an important role in TCP/IP networking. They provide a default route for TCP/IP hosts to use when communicating with other hosts on remote networks.

The following illustration shows the role played by two default gateways (IP routers) for two networks: Network 1 and Network 2.
Role of default gateways

In order for Host A on Network 1 to communicate with Host B on Network 2, Host A first checks its routing table to see if a specific route to Host B exists. If there is no specific route to Host B, Host A forwards its TCP/IP traffic for Host B to its own default gateway, IP Router 1.

The same principle applies if Host B is sending to Host A. Without a specific route to Host A, Host B forwards any TCP/IP traffic destined for Host A to its own default gateway, IP Router 2.
Why gateways work

Default gateways are important to make IP routing work efficiently. In most cases, the router that acts as the default gateway for TCP/IP hosts--either a dedicated router or a computer that connects two or more network segments--maintains knowledge of other networks in the larger network and how to reach them.

TCP/IP hosts rely on default gateways for most of their communication needs with hosts on remote network segments. In this way, individual hosts are freed of the burden of having to maintain extensive and continuously updated knowledge about individual remote IP network segments. Only the router that acts as the default gateway needs to maintain this level of routing knowledge to reach other remote network segments in the larger internetwork.

If the default gateway fails, communication beyond the local network segment may be impaired. To prevent this, you can use the Advanced TCP/IP Settings dialog box (in Network Connections) for each connection to specify multiple default gateways. You can also use the route command to manually add routes to the routing table for heavily used hosts or networks.

This is a great and very common question, and one that I hear at least every week. It's also important to understand the answer, as controller implementation serves as a primary differentiation in enterprise-class systems (the other being management features). Let's start with the big picture. The purpose of a WLAN system is of course to move data in essentially the same manner as a wired LAN. But there's a much higher degree of variability in the architecture of WLAN systems and solutions, and we therefore have developed a model, based on the concept of planes, to describe the internal functions of a given WLAN architecture. These planes are as follows:

Data Plane – This describes how data moves within the WLAN. The biggest question is whether data from an access point (AP) can be forwarded directly to its destination, or whether this data must flow through a separate physical element, called a controller.

Management Plane – This describes how the system is configured, monitored, and how many other required functions are implemented. The management function is almost always centralized in a single location, even for large, distributed, and multi-vendor solutions. The point of residence can also be in a controller, or a separate appliance or server.

Control Plane – This plane can be thought of as the “operating system” of the WLAN, executing policies defined by the Management Plane and optimizing the flow of data in the Data Plane. And, you guessed it, such functionality also often resides in a controller (which can even be virtual in some products), or can be distributed across the APs. Controller functionality can also move among elements in some implementations.

We can probably agree that the Data Plane should be as distributed as possible, and that the Management Plane must be centralized. So it's the Control Plane that presents the greatest opportunity for controversy, as it can be fully distributed and implemented in an AP, reside in a server, or, again, live in a separate box, the controller. While vendor arguments are plentiful and often persuasive, there's not enough empirical (based on appropriate benchmarks) or analytical (the results of mathematical models of system behavior given specific configuration and loading) to provide a definitive argument either way. One can certainly make the argument that a controller adds cost (and that additional or redundant controllers may be required to handle certain loads and/or provide fault tolerance), but one must consider the total cost of a given solution, not the cost of individual elements. And one can make the argument that a controller-based implementation provides a more global view of system condition and behavior, and thus could yield higher performance especially over time – but, again, there are no definitive studies (yet) one way or the other. The degree of architectural diversity around this question is indeed significant, and we expect to see additional architectural variability before any definitive solution is recognized as such.

Do you need a controller? Much depends upon what your supplier proposes. Careful analysis of the arguments presented by vendors during the purchasing process and appropriate benchmarking tests based on local requirements are the only guides at present.

A mesh network is a network topology in which each node (called a mesh node) relays data for the network. All nodes cooperate in the distribution of data in the network.

A mesh network can be designed using a flooding technique or a routing technique. When using a routing technique, the message is propagated along a path, by hopping from node to node until the destination is reached. To ensure all its paths' availability, a routing network must allow for continuous connections and reconfiguration around broken or blocked paths, using self-healing algorithms. A mesh network whose nodes are all connected to each other is a fully connected network. Fully connected wired networks have the advantages of security and reliability: problems in a cable affect only the two nodes attached to it. However, in such networks, the number of cables, and therefore the cost, goes up rapidly as the number of nodes increases.

Mesh networks can be seen as one type of ad hoc network. Mobile ad hoc networks (MANETs) and mesh networks are therefore closely related, but a MANET also must deal with problems introduced by the mobility of the nodes.

The self-healing capability enables a routing-based network to operate when one node breaks down or a connection goes bad. As a result, the network is typically quite reliable, as there is often more than one path between a source and a destination in the network. Although mostly used in wireless situations, this concept is also applicable to wired networks and software interaction.