A virtual private network (VPN) extends a private network across a public network, and enables users to send and receive data across shared or public networks as if their computing devices were directly connected to the private network. Applications running across a VPN may therefore benefit from the functionality, security, and management of the private network. Encryption is a common though not an inherent part of a VPN connection.
VPN technology was developed to allow remote users and branch offices to access corporate applications and resources. To ensure security, the private network connection is established using an encrypted layered tunneling protocol and VPN users use authentication methods, including passwords or certificates, to gain access to the VPN. In other applications, Internet users may secure their transactions with a VPN, to circumvent geo-restrictions and censorship, or to connect to proxy servers to protect personal identity and location to stay anonymous on the Internet. However, some websites block access to known VPN technology to prevent the circumvention of their geo-restrictions, and many VPN providers have been developing strategies to get around these roadblocks.
A VPN is created by establishing a virtual point-to-point connection through the use of dedicated circuits or with tunneling protocols over existing networks. A VPN available from the public Internet can provide some of the benefits of a wide area network (WAN). From a user perspective, the resources available within the private network can be accessed remotely.
Early data networks allowed VPN-style connections to remote sites through dial-up modem or through leased line connections utilizing X.25, Frame Relay and Asynchronous Transfer Mode (ATM) virtual circuits, provided through networks owned and operated by telecommunication carriers. These networks are not considered true VPNs because they passively secure the data being transmitted by the creation of logical data streams. They have been replaced by VPNs based on IP and IP/Multi-protocol Label Switching (MPLS) Networks, due to significant cost-reductions and increased bandwidth provided by new technologies such as digital subscriber line (DSL) and fiber-optic networks.
VPNs can be characterized as host-to-network or remote access by connecting a single computer to a network, or as site-to-site for connecting two networks. In a corporate setting, remote-access VPNs allow employees to access the company's intranet from outside the office. Site-to-site VPNs allow collaborators in geographically disparate offices to share the same virtual network. A VPN can also be used to interconnect two similar networks over a dissimilar intermediate network; for example, two IPv6 networks over an IPv4 network.
VPN systems may be classified by:
VPNs cannot make online connections completely anonymous, but they can usually increase privacy and security. To prevent disclosure of private information, VPNs typically allow only authenticated remote access using tunneling protocols and encryption techniques.
The VPN security model provides:
Secure VPN protocols include the following:
Tunnel endpoints must be authenticated before secure VPN tunnels can be established. User-created remote-access VPNs may use passwords, biometrics, two-factor authentication or other cryptographic methods. Network-to-network tunnels often use passwords or digital certificates. They permanently store the key to allow the tunnel to establish automatically, without intervention from the administrator.
Tunneling 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.
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.
A device that is within a customer's network and not directly connected to the service provider's network. C devices are not aware of the VPN.
A device at the edge of the customer's network which provides access to the PPVPN. Sometimes it is just a demarcation point between provider and customer responsibility. Other providers allow customers to configure it.
A PE is a device, or set of devices, at the edge of the provider network which connects to customer networks through CE devices and presents the provider's view of the customer site. PEs are aware of the VPNs that connect through them, and maintain VPN state.
A P device operates inside the provider's core network and does not directly interface to any customer endpoint. It might, for example, provide routing for many provider-operated tunnels that belong to different customers' PPVPNs. While the P device is a key part of implementing PPVPNs, it is not itself VPN-aware and does not maintain VPN state. Its principal role is allowing the service provider to scale its PPVPN offerings, for example, by acting as an aggregation point for multiple PEs. P-to-P connections, in such a role, often are high-capacity optical links between major locations of providers.
Virtual LAN (VLAN) is a Layer 2 technique that allow for the coexistence of multiple local area network (LAN) broadcast domains, interconnected via trunks using the IEEE 802.1Q trunking protocol. Other trunking protocols have been used but have become obsolete, including Inter-Switch Link (ISL), IEEE 802.10 (originally a security protocol but a subset was introduced for trunking), and ATM LAN Emulation (LANE).
Developed by Institute of Electrical and Electronics Engineers, Virtual LANs (VLANs) allow multiple tagged LANs to share common trunking. VLANs frequently comprise only customer-owned facilities. Whereas VPLS as described in the above section (OSI Layer 1 services) supports emulation of both point-to-point and point-to-multipoint topologies, the method discussed here extends Layer 2 technologies such as 802.1d and 802.1q LAN trunking to run over transports such as Metro Ethernet.
As used in this context, a VPLS is a Layer 2 PPVPN, emulating the full functionality of a traditional LAN. From a user standpoint, a VPLS makes it possible to interconnect several LAN segments over a packet-switched, or optical, provider core; a core transparent to the user, making the remote LAN segments behave as one single LAN.
In a VPLS, the provider network emulates a learning bridge, which optionally may include VLAN service.
PW is similar to VPLS, but it can provide different L2 protocols at both ends. Typically, its interface is a WAN protocol such as Asynchronous Transfer Mode or Frame Relay. In contrast, when aiming to provide the appearance of a LAN contiguous between two or more locations, the Virtual Private LAN service or IPLS would be appropriate.
EtherIP (RFC 3378) is an Ethernet over IP tunneling protocol specification. EtherIP has only packet encapsulation mechanism. It has no confidentiality nor message integrity protection. EtherIP was introduced in the FreeBSD network stack and the SoftEther VPN server program.
A subset of VPLS, the CE devices must have Layer 3 capabilities; the IPLS presents packets rather than frames. It may support IPv4 or IPv6.
This section discusses the main architectures for PPVPNs, one where the PE disambiguates duplicate addresses in a single routing instance, and the other, virtual router, in which the PE contains a virtual router instance per VPN. The former approach, and its variants, have gained the most attention.
One of the challenges of PPVPNs involves different customers using the same address space, especially the IPv4 private address space. The provider must be able to disambiguate overlapping addresses in the multiple customers' PPVPNs.
In the method defined by RFC 2547, BGP extensions advertise routes in the IPv4 VPN address family, which are of the form of 12-byte strings, beginning with an 8-byte route distinguisher (RD) and ending with a 4-byte IPv4 address. RDs disambiguate otherwise duplicate addresses in the same PE.
PEs understand the topology of each VPN, which are interconnected with MPLS tunnels, either directly or via P routers. In MPLS terminology, the P routers are Label Switch Routers without awareness of VPNs.
The virtual router architecture, as opposed to BGP/MPLS techniques, requires no modification to existing routing protocols such as BGP. By the provisioning of logically independent routing domains, the customer operating a VPN is completely responsible for the address space. In the various MPLS tunnels, the different PPVPNs are disambiguated by their label, but do not need routing distinguishers.
Some virtual networks use tunneling protocols without encryption for protecting the privacy of data. While VPNs often do provide security, an unencrypted overlay network does not neatly fit within the secure or trusted categorization. For example, a tunnel set up between two hosts with Generic Routing Encapsulation (GRE) is a virtual private network, but neither secure nor trusted.
Native plaintext tunneling protocols include Layer 2 Tunneling Protocol (L2TP) when it is set up without IPsec and Point-to-Point Tunneling Protocol (PPTP) or Microsoft Point-to-Point Encryption (MPPE).
Trusted VPNs do not use cryptographic tunneling, and instead rely on the security of a single provider's network to protect the traffic.
From the security standpoint, VPNs either trust the underlying delivery network, or must enforce security with mechanisms in the VPN itself. Unless the trusted delivery network runs among physically secure sites only, both trusted and secure models need an authentication mechanism for users to gain access to the VPN.
Users utilize mobile virtual private networks 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. Field service management and by healthcare organizations, among other industries, also make use of them.
Increasingly, mobile professionals who need reliable connections are adopting mobile VPNs. 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 disconnect, time out, or fail, or even cause the computing device itself to crash.
Instead of logically tying the endpoint of the network tunnel to the physical IP address, each tunnel is bound to a permanently associated IP address at the device. The mobile VPN software handles the necessary network-authentication and maintains the network sessions in a manner transparent to the application and to the user. The Host Identity Protocol (HIP), under study by the Internet Engineering Task Force, is designed to support mobility of hosts by separating the role of IP addresses for host identification from their locator functionality in an IP network. With HIP a mobile host maintains its logical connections established via the host identity identifier while associating with different IP addresses when roaming between access networks.
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. Home users usually deploy VPNs on their routers to protect devices, such as smart TVs or gaming consoles, which are not supported by native VPN clients. Supported devices are not restricted to those capable of running a VPN client.
Setting up VPN services on a router requires a deep knowledge of network security and careful installation. Minor misconfiguration of VPN connections can leave the network vulnerable. Performance will vary depending on the Internet service provider (ISP).
A limitation of traditional VPNs is that they are point-to-point connections, and do not tend to support broadcast domains. Therefore, communication, software, and networking, which are based on layer 2 and broadcast packets, such as NetBIOS used in Windows networking, may not be fully supported as on a local area network. Variants on VPN, such as Virtual Private LAN Service (VPLS), and layer 2 tunneling protocols, are designed to overcome this limitation.
OpenConnect is a client for Cisco's AnyConnect SSL VPN [...] OpenConnect is not officially supported by, or associated in any way with, Cisco Systems. It just happens to interoperate with their equipment.
[...] VPNs using dedicated circuits, such as Frame Relay [...] are sometimes called trusted VPNs, because customers trust that the network facilities operated by the service providers will not be compromised.
AceVPN (or Ace VPN) is a U.S.-based virtual private network (VPN) subscription provider. It offers private network services over a public network.
AceVPN has been used to circumvent IP restrictions in certain areas to access internet and app functions.Beginning in May 2013, Ace VPN usage soared when the Turkish government shut down Facebook and Twitter access within its borders in retaliation of the Gezi Park protests. The crackdown on internet usage was seen as a major human rights violation and VPNs became popular in the nation and elsewhere. Ace VPN has remained one of the most popular VPNs in Turkey as the nation's Parliament has begun debating the controversial topic of internet censorship.Ace VPN currently holds an active Warrant canary.Avast SecureLine VPN
Avast SecureLine VPN is a subscription based virtual private network (VPN) service developed by Avast. It is available for Android, Microsoft Windows, macOS and iOS operating systems.SecureLine VPN encrypts the user's internet traffic and redirects the traffic through a tunnel via Avast data centers. This changes the geolocation of the IP address of the user to that of the selected VPN server and makes the user appear to be in a different location.It also anonymizes the user's online activity, protects users from hacking, can avoid some forms of surveillance, and allows unrestricted access to the Internet. A VPN also prevents user's detailed browsing data and history from being collected and sold by ISPs or other entities that may otherwise have access to them. The VPN can be set to automatically turn on when the user connects to a public Wi-Fi.Axtel
Axtel S.A.B. de C.V., known as Axtel, is a Mexican telecommunications company headquartered in San Pedro, near Monterrey. It offers telephone, internet, and television services through FTTH in 45 cities of Mexico as well as IT Services. It is the second largest landline telephone service provider and a relevant virtual private network operator.AzireVPN
AzireVPN is a personal virtual private network (VPN) service.Dynamic Multipoint Virtual Private Network
Dynamic Multipoint Virtual Private Network (DMVPN) is a dynamic tunneling form of a virtual private network (VPN) supported on Cisco IOS-based routers, Huawei AR G3 routers and USG firewalls, and on Unix-like operating systems.ExpressVPN
ExpressVPN is a virtual private network service offered by the British Virgin Islands-based company Express VPN International Ltd. The software is marketed as a privacy and security tool that encrypts users’ web traffic and masks their IP addresses.In 2018, TechRadar named the services its Editors’ Choice.Hola (VPN)
Hola is a freemium web and mobile application which provides a form of virtual private network services to its users through a peer-to-peer network. It also uses peer-to-peer caching. When a user accesses certain domains that are known to use geo-blocking, the Hola application redirects the request to go through the computers and Internet connections of other users in non-blocked areas, thereby circumventing the blocking. This also means that other users might access the Internet through one's own computer, and that part of one's upload bandwidth might be used for serving cached data to other users. Paying users can choose to redirect all requests to peers but are themselves never used as peers.Hotspot Shield
Hotspot Shield is a public virtual private network (VPN) service, operated by AnchorFree, Inc. By establishing an encrypted connection with the Hotspot Shield servers, the service protects its users' Internet traffic from eavesdropping. Hotspot Shield was used to bypass government censorship during the Arab Spring protests in Egypt, Tunisia, and Libya.Layer 2 Forwarding Protocol
L2F, or Layer 2 Forwarding, is a tunneling protocol developed by Cisco Systems, Inc. to establish virtual private network connections over the Internet. L2F does not provide encryption or confidentiality by itself; It relies on the protocol being tunneled to provide privacy. L2F was specifically designed to tunnel Point-to-Point Protocol (PPP) traffic.Mobile virtual private network
A mobile virtual private network (mobile VPN or mVPN) is a VPN which is capable of persisting during sessions across changes in physical connectivity, point of network attachment, and IP address. The "mobile" in the name refers to the fact that the VPN can change points of network attachment, not necessarily that the mVPN client is a mobile phone or that it is running on a wireless network.Mobile VPNs are used in environments where workers need to keep application sessions open at all times, throughout the working day, as they connect via various wireless networks, encounter gaps in coverage, or suspend-and-resume their devices to preserve battery life. A conventional VPN cannot survive such events because the network tunnel is disrupted, causing applications to disconnect, time out, fail, or even the computing device itself to crash. Mobile VPNs are commonly used in public safety, home care, hospital settings, field service management, utilities and other industries. Increasingly, they are being adopted by mobile professionals and white-collar workers.Netsentron
NetSentron is a network security appliance designed and sold by Kobelt Development Inc. (KDI), a Surrey, British Columbia-based IT services company. The NetSentron appliance is a firewall, website content filter, and virtual private network remote access device.NordVPN
NordVPN is a personal virtual private network (VPN) service provider. It has desktop applications for Windows, macOS, and Linux, mobile apps for Android and iOS, as well as an application for Android TV. Manual setup is available for wireless routers, NAS devices and other platforms. In 2017, PC Magazine rated NordVPN as the year's best VPN service.NordVPN is based in Panama, as the country has no mandatory data retention laws and does not participate in the Five Eyes or Fourteen Eyes alliances. An independent audit by PricewaterhouseCoopers has described the company's claims of not logging users' data as accurate.In 2018, NordVPN became the first official cybersecurity partner of Liverpool F.C.OPNsense
OPNsense is open source, FreeBSD-based firewall and routing software developed by Deciso, a company in the Netherlands that makes hardware and sells support packages for OPNsense. It is a fork of m0n0wall, which was built on FreeBSD. It was launched in January 2015. When m0n0wall closed down in February 2015 its creator, Manuel Kaspar, referred its developer community to OPNsense.OPNsense has a web-based interface and can be used on i386 and x86-64 platforms. Along with acting as a firewall, it has traffic shaping, load balancing, and virtual private network capabilities, and others can be added via plugins.In November 2017, a World Intellectual Property Organization panel found that Netgate, the copyright holder of pfSense, had been using the domain opnsense.com in bad faith to discredit OPNsense, and obligated Netgate to transfer the domain to Deciso. The Netgate party tried to invoke the fair use clause and claimed that the domain name "has been used for a parody website"; it was rejected on the basis that free speech does not cover registration of domain names.Private Internet Access
Private Internet Access (PIA) is a personal virtual private network (VPN) service. It supports multiple VPN technologies such as PPTP, L2TP/IPsec, SOCKS5 and OpenVPN. In 2018, former Mt. Gox CEO Mark Karpelès was named chief technology officer of PIA's parent company, London Trust Media.ProtonVPN
ProtonVPN is a virtual private network (VPN) service provider operated by the Swiss company ProtonVPN AG. The company is a beneficiary of Proton Technologies AG, the company behind the email service ProtonMail. According to ProtonVPN's official website, ProtonVPN and ProtonMail operate on "completely segregated infrastructures" for technical security reasons.SaferVPN
SaferVPN is a Virtual Private Network utility developed by Safer Social, Ltd. The network protects user data from Wi-Fi security risks through end-to-end encryption of user connections. SaferVPN has provided free accounts to dissidents in Turkey, Iran, and Bangladesh.TunnelBear
TunnelBear (also known as the TunnelBear VPN) is a public virtual private network (VPN) service based in Toronto, Canada. The company was founded by Daniel Kaldor and Ryan Dochuk in 2011. In March 2018, TunnelBear was acquired by McAfee.VPN.ht
VPN.ht Openvpn Client is a personal VPN service made famous for the ads on the free BitTorrent streaming service, Popcorn Time. It supports multiple VPN technologies such as PPTP, L2TP/IPSec, SOCKS5 and OpenVPN. and offers several features:
Full compatibility with all OS and devices
File Sharing Allowed
Zero logs policy
Multiple VPN Gateways
Unlimited BandwidthIn 2016, the MPAA successfully obtained an interim injunction, in Canada, against VPN.ht and the popular online torrent streaming service, PopcornTime.io. Further demands asked for both services to be shutdown. VPN.ht claimed their company was not subject to Canadian jurisdiction and users should not be concerned. As of December, 2017 the site is stilling accepting new sign ups.VPNBook
VPNBook is a free virtual private network service. The service is financed by advertising and donations.
The service connects to a VPN via OpenVPN client or a PPTP connection. There are minimal variety of geographic locations. Available servers include the United States, Canada and Romania. VPNBook can be used to bypass some governmental restrictions.
Virtual private networking
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Internet censorship circumvention technologies