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With the increasing use of VPNs, many have started deploying VPN connectivity on routers for additional security and encryption of data transmission by using various cryptographic techniques. Setting up VPN services on a router allows any connected device to use the VPN network while it is enabled. This also creates VPN services on devices that do not have native VPN clients such as smart-TVs, gaming consoles etc. Many router manufacturers, such as Cisco, Linksys, Asus, and Netgear supply their routers with built-in VPN clients.

Mobile virtual private networks are used in settings where an endpoint of the VPN is not fixed to a single IP address, but instead roams across various networks such as data networks from cellular carriers or between multiple Wi-Fi access points. Mobile VPNs have been widely used in public safety, where they give law enforcement officers access to mission-critical applications, such as computer-assisted dispatch and criminal databases, while they travel between different subnets of a mobile network. They are also used in field service management and by healthcare organizations, among other industries. Increasingly, mobile VPNs are being adopted by mobile professionals who need reliable connections. They are used for roaming seamlessly across networks and in and out of wireless coverage areas without losing application sessions or dropping the secure VPN session. A conventional VPN can not withstand such events because the network tunnel is disrupted, causing applications to d

Tunnelling protocols can operate in a point-to-point network topology that would theoretically not be considered as a VPN, because a VPN by definition is expected to support arbitrary and changing sets of network nodes. But since most router implementations support a software-defined tunnel interface, customer-provisioned VPNs often are simply defined tunnels running conventional routing protocols. Provider-provisioned VPN building-blocks        Depending on whether a provider-provisioned VPN (PPVPN)operates in layer 2 or layer 3, the building blocks described below may be L2 only, L3 only, or combine them both. Multi-protocol label switching (MPLS) functionality blurs the L2-L3 identity. RFC 4026 generalized the following terms to cover L2 and L3 VPNs, but they were introduced in RFC 2547. More information on the devices below can also be found in Lewis, Cisco Press. Customer (C) devices A device that is within a customer's network and not directly connecte

A virtual private network (VPN) extends a private network across a public network, such as the Internet. It enables users to send and receive data across shared or public networks as if their computing devices were directly connected to the private network, and thus are benefiting from the functionality, security and management policies of the private network. A VPN is created by establishing a virtual point-to-point connection through the use of dedicated connections, virtual tunnelling protocols, or traffic encryption. A VPN spanning the Internet is similar to a wide area network (WAN). From a user perspective, the extended network resources are accessed in the same way as resources available within the private network. Traditional VPNs are characterized by a point-to-point topology, and they do not tend to support or connect broadcast domains. Therefore, communication, software, and networking, which are based on OSI layer 2 and broadcast packets, such as NetBIOS used in W

This approach is described as full virtualization of the hardware, and can be implemented using a type 1 or type 2 hypervisor: a type 1 hypervisor runs directly on the hardware, and a type 2 hypervisor runs on another operating system, such as Linux or Windows. Each virtual machine can run any operating system supported by the underlying hardware. Users can thus run two or more different "guest" operating systems simultaneously, in separate "private" virtual computers. The pioneer system using this concept was IBM's CP-40, the first (1967) version of IBM's CP/CMS (1967–1972) and the precursor to IBM's LPAR VM family (1972–present). With the VM architecture, most users run a relatively simple interactive computing single-user operating system, CMS, as a "guest" on top of the VM control program (VM-CP). This approach kept the CMS design simple, as if it were running alone; the control program quietly provides multitasking and resource m

        A process VM, sometimes called an application virtual machine, or Managed Runtime Environment (MRE), runs as a normal application inside a host OS and supports a single process. It is created when that process is started and destroyed when it exits. Its purpose is to provide a platform-independent programming environment that abstracts away details of the underlying hardware or operating system, and allows a program to execute in the same way on any platform. A process VM provides a high-level abstraction – that of a high-level programming language (compared to the low-level ISA abstraction of the system VM). Process VMs are implemented using an interpreter; performance comparable to compiled programming languages can be achieved by the use of just-in-time compilation. This type of VM has become popular with the Java programming language, which is implemented using the Java virtual machine. Other examples include the Parrot virtual machine, and the .NET Framework,

System virtual machine advantages Multiple OS environments can co-exist on the same primary hard drive, with a virtual partition that allows sharing of files generated in either the "host" operating system or "guest" virtual environment. Adjunct software installations, wireless connectivity, and remote replication, such as printing and faxing, can be generated in any of the guest or host operating systems. Regardless of the system, all files are stored on the hard drive of the host OS. Application provisioning, maintenance, high availability and disaster recovery are inherent in the virtual machine software selected. Can provide emulated hardware environments different from the host's instruction set architecture (ISA), through emulation or by using just-in-time compilation. The main disadvantages of VMs are: A virtual machine is less efficient than an actual machine when it accesses the host hard drive indirectly. When multiple VMs are concurren

         In computing, a virtual machine (VM) is an emulation of a particular computer system. Virtual machines operate based on the computer architecture and functions of a real or hypothetical computer, and their implementations may involve specialized hardware, software, or a combination of both.        Various different kinds of virtual machines exist, each with different functions. System virtual machines (also known as full virtualization VMs) provide a complete substitute for the targeted real machine and a level of functionality required for the execution of a complete operating system. A hypervisor uses native execution to share and manage hardware, allowing multiple different environments, isolated from each other, to be executed on the same physical machine. Modern hypervisors use hardware-assisted virtualization, which provides efficient and full virtualization by using virtualization-specific hardware capabilities, primarily from the host CPUs. Process virtual machin

Unix shell A Unix shell is a command-line interpreter or shell that provides a traditional Unix-like command line user interface. Users direct the operation of the computer by entering commands as text for a command line interpreter to execute, or by creating text scripts of one or more such commands. Users typically interact with a Unix shell using a terminal emulator, however, direct operation via serial hardware connections, or networking session, are common for server systems. All Unix shells provide filename wildcarding, piping, here documents, command substitution, variables and control structures for condition-testing and iteration. Concept The most generic sense of the term shell means any program that users employ to type commands. A shell hides the details of the underlying operating system and manages the technical details of the operating system kernel interface, which is the lowest-level, or "inner-most" component of most operating systems. In