International Research Journal of Engineering and Technology (IRJET) e-ISSN: 2395-0056 Volume: 04 Issue: 11 | Nov -2017 www.irjet.net p-ISSN: 2395-0072 Review on protocols of Virtual Private Network Shaikh Shahebaz1, Sujay Madan2, Sujata Magare3 1 Student, Dept. Of MCA [JNEC College] Cidoco N-6, Aurangabad, Maharashtra, India 2 Student Dept. of MCA [JNEC College] Cidoco N-6, Aurangabad, Maharashtra, India 3AssistantProfessor, Dept. of MCA, [JNEC College]Cidoco N-6, Aurangabad, Maharashtra, India ---------------------------------------------------------------------***--------------------------------------------------------------------- Abstract – Virtual: Virtual means not real or in a different is used to maintain the PPTP tunnel [3].PPTP allows a PPP state of being. In a VPN, private communication between two session, with non-TCP/IP protocols, to be tunneled through or more devices is achieved through a public network the an IP network. The authentication protocols used by PPTP Internet. Therefore, the communication is virtually but not are: Extensible Authentication Protocol (EAP), Microsoft physically there. Challenge-Handshake uthentication Protocol (MCHAP), Shiva Password Authentication Protocol (SPAP), and Password Private: Private means to keep something a secret from the Authentication Protocol (PAP). general public. Although those two devices are communicating with each other in a public environment, there is no third [B]. Layer 2 Tunneling Protocol (L2TP) party who can interrupt this communication or receive any data that is exchanged between them. Asynchronous Transfer Mode, Frame Relay and X.25 networks use L2TP as tunneling protocol for data Key Words: VPN Tunneling, VPN protocols, Point 2 Point transmission between the communicating nodes. L2TP is Tunneling protocol, Layer 2 Tunneling Protocol. also operated at the layer 2 of OSI architecture. One tunnel can allow multiple connections. Layer two tunneling 1. INTRODUCTION protocol encapsulates data in PPP frames and is capable of transmitting non-IP protocols over an IP network. L2TP The VPN connection allows users working at home or on the connections use the same authentication mechanisms as PPP road to connect in a secure fashion to a remote corporate connections, such as EAP, CHAP, and MSCHAP. L2TP server using the routing infrastructure provided by public tunneling is accomplished through multiple levels of internetworks (such as the Internet). From the user’s encapsulation. The PPP data is encapsulated within a PPP perspective, the VPN connection is a point-to-point header and an L2TP header. The encapsulated L2TP packet connection between the user’s computer & a corporate is further encapsulated in a UDP header. The final packet is server. The nature of the intermediate internetworks is encapsulated with an IP header containing the source and irrelevant to the user because it appears as if the data is destination IP addresses of the VPN client and VPN server. being sent over a dedicated private link. VPN connection also allows a corporation to connect to branch offices or to other [C].Secured Socket Layer companies over a public internetwork (such as the Internet), while maintaining secure communications. The VPN An SSL VPN (Secure Sockets Layer virtual private network) connection across the Internet logically operates as a wide is a form of VPN that can be used with a standard Web area network (WAN) link between the sites. In both these browser. In contrast to the traditional Internet Protocol cases, the secure connection across the internetwork Security (IPsec) VPN, an SSL VPN does not require the appears to the user as a private network communication— installation of specialized client software on the end user's despite the fact that this communication occurs over a public computer. It's used to give remote users with access to Web internetwork. Hence, the name - virtual private network. applications, client/server applications and internal network connections. 1.1 Protocols used in VPN: [D].OpenVPN [A]. Point to Point Tunnel Protocol (PPTP) VPN Unlimited currently supports only OpenVPN via the UDP port. It is a simple OSI transport layer protocol for Point to Point Tunneling Protocol is an OSI layer two network applications based on internet Protocol (IP). UDP is protocol built on top of the Point to Point Protocol (PPP). the main alternative to TCP and one of the oldest network PPTP connects to the target network by creating a virtual protocols, introduced in 1980. UDP is an ideal protocol for network for each remote client. The PPTP control connection network applications in which perceived latency is critical carries the PPTP call control and management message that such as gaming, voice and video communications. The © 2017, IRJET | Impact Factor value: 6.171 | ISO 9001:2008 Certified Journal | Page 1598 International Research Journal of Engineering and Technology (IRJET) e-ISSN: 2395-0056 Volume: 04 Issue: 11 | Nov -2017 www.irjet.net p-ISSN: 2395-0072 protocol permits individual packets to be dropped and UDP The payload is first encapsulated in a GRE packet, which packets to be received in a different order than that in which possibly includes the route. The resulting GRE packet can they were sent, allowing for better performance. then be encapsulated in some other protocol and then forwarded. The outer protocol is the delivery protocol. 2. PPTP 3. Tunneling in PPTP A consortium, consisting of Ascend Communications, 3Com, ECI Telematics, U.S. Robotics, and Microsoft, developed the A tunnel is defined by PNS (PPTP network server) - PAC PPTP specification for the tunneling of data across the (PPTP access concentrator) pair. The tunnel protocol is Internet.The PPTP protocol [4] is built on the well- defined by a modified version of GRE .The tunnel carries PPP established Internet Communications Protocol PPP (point- datagrams between the PAC and the PNS. A control to-point protocol), and TCP/IP (Transmission Control connection operating over TCP controls the establishment, Protocol/Internet Protocol).Multiprotocol PPP offers release and maintenance of sessions and of the tunnel itself. authentication as well as methods of privacy and compression of data. IP is routable, and has an Internet Comparison of VPN Protocols: IPSec, PPTP, and L2TP infrastructure. PPTP allows a PPP session to be tunneled through an existing IP connection, no matter how it was set Before PPP tunneling can occur between a PAC and PNS, a up. An existing connection can be treated as if it were a control connection must be established between them. The telephone line, so a private network can run over a public control connection is a standard TCP session over which one. Tunneling is achieved because PPTP provides PPTP call control and management information is passed. ncapsulation by wrapping packets of information (IP, IPX, or This tunnel is used to carry all user session PPP packets for NetBEUI) within IP packets for transmission through the sessions involving a given PNS-PAC pair. Internet. Upon receipt, the external IP packets are stripped away, exposing the original packets for delivery. 3.1 Types of Tunneling: Encapsulation allows the transport of packets that will not otherwise conform to Internet addressing standards. PPTP Tunnels can be created in various ways: encapsulates Point-To-Point Protocol (PPP) frames into IP data grams for transmission over an IP-based Internet work, 3.1.1 Compulsory Tunneling: such as Internet. To encapsulate PPP frames as tunneled data, PPTP uses a TCP connection known as PPTP control Compulsory tunneling (also referred to as NAS- connection to create, maintain and terminate the tunnel & a initiated tunneling) enables users to dial to NAS(Network modified version of Generic Routing Encapsulation (GRE). Access Servers), which then establishes tunnel to the server. PPTP inherits encryption or compression or both, of PPP The connection between the client of the user and the NAS is payloads from PPP. Authentication that occurs during the not encrypted. creation of PPTP-based VPN connection uses the same authentication mechanisms as PPP connections, such as: 3.1.2 Voluntary Tunneling · Extensible Authentication Protocol (EAP). Voluntary tunneling (also referred to as client-initiated · Challenge Handshake Protocol (CHAP). tunneling) enables clients to configure and establish · Shiva Password Authentication Protocol (SPAP) and encrypted tunnels to tunnel servers without an intermediate · Password Authentication Protocol (PAP). NAS participating in the tunnel negotiation and the establishment. For PPTP, only voluntary tunneling is 2.1 PAP supported. PPTP works by encapsulating the virtual private network packets inside of PPP packets which are in turn encapsulated in Generic Routing Encapsulation (GRE), Password Authentication Protocol (PAP) provides a method packets sent over IP from the client to the gateway PPTP for the peer to establish its identity using a 2-way server and back again. In conjunction with this encapsulated handshake. This is one of the ways of user authentication. A data channel, there is a TCP-based control session. The stronger authentication such, as CHAP must negotiate prior control session packets are used to query status and convey to PAP. signaling information between client and the server. The control channel is initiated by the client to the server on TCP GRE port. In most cases this is a bi-directional communication channel where the client can send requests to the server and The Protocol GRE (Generic Routing Encapsulation)