Vpn tunneling protocols
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VPN TUNNELING PROTOCOLS. PPTP, L2TP, L2TP/IPsec. Ashkan Yousefpour Amirkabir University of Technology. Today’s Overview . Why using VPNs?. fast , secure and reliable connection between separated networks full access on resources from everywhere -> building a virtual local connection

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Vpn tunneling protocols




Amirkabir University of Technology

Today s overview

Today’s Overview

Why using vpns

Why using VPNs?

fast, secure and reliable connection betweenseparated networks

full access on resources from everywhere ->building a virtual local connection

reasonable access: building connection onlyto local ISP

Vpn tunneling protocols

PPTP - enables secure data transfers between a remote client and an enterprise server by creating a VPN across an IP-based internetwork

Point to point tunneling protocol pptp rfc 2637

Point-to-Point Tunneling Protocol (PPTP) [RFC 2637]

  • Standard method for transporting multiprotocol datagrams over point-to-point links

  • Mainly implemented and used by Microsoft

  • Extension of PPP

  • Allows tunneling of PPP datagrams over IP networks

  • Easy to use and to implement

  • Use of 2 connections

    • Control connection

    • Tunnel connection

  • Operates at layer 2 of OSI

  • Uses TCP Port 1723

Point to point tunneling protocol pptp rfc 2637 continued

Point-to-Point Tunneling Protocol (PPTP) [RFC 2637] - continued

  • PPTP is a tunneling protocol provided by Microsoft, which provides remote users, encrypted, multi protocol access to a corporate network over the Internet.

  • It encapsulates PPP frames in IP data grams

  • Microsoft’s implementation of PPTP has been found to have several problems that make it vulnerable to attacks, and it also lakes the scalability in that it only supports 255 concurrent connections per server.

  • Require an IP Network between PPTP Client and PPTP Server ( either LAN or dial- up)

  • PPTP can support only one tunnel at a time for each user.

Vpn tunneling protocols


  • Uses Generic Routing Encapsulation (GRE) to carry PPP packets

  • PPP payload can be encrypted and/or compressed

  • GRE header contains information about tunnel protocol and encryption algorithm

  • Structure of PPTP packet:

Layer 2 tunneling protocol l2tp rfc 2661

Layer 2 Tunneling Protocol (L2TP) [RFC 2661]

  • Uses UDP

  • Can be transported over IP, Frame Relay, ATM, X.25, ...

  • Allows multiple tunnels with multiple sessions inside every tunnel

  • UDP Port 1701

  • Commonly used with IPsec -> L2TP/IPsec

Layer 2 tunneling protocol l2tp rfc 2661 continued

Layer 2 Tunneling Protocol (L2TP) [RFC 2661]Continued

  • Structure of L2TP packet:

Layer 2 tunneling protocol l2tp rfc 2661 continued1

Layer 2 Tunneling Protocol (L2TP) [RFC 2661]Continued

  • A hybrid of Microsoft’s PPTP and Cisco Systems’ Layer 2 Forwarding - L2F protocol

  • can support multiple, simultaneous tunnels for each user.

  • It Uses UDP and supports any routed protocol, including IP, IPX and AppleTalk, including frame relay, ATM, X. 25

  • Because of L2TP’s use of PPTP, it is included as part of the remote access features of most Windows Products

  • It does not provide cryptographically key security features

Layer 2 tunneling protocol l2tp rfc 2661 continued2

Layer 2 Tunneling Protocol (L2TP) [RFC 2661]Continued

  • L2TP allows multiprotocol traffic to be encrypted and then sent over any medium that supports point-to-point datagram delivery, such as IP or asynchronous transfer mode (ATM).

  • L2TP is a combination of PPTP and Layer 2 Forwarding (L2F), a technology developed by Cisco Systems, Inc.

  • It can support IPsec for data encryption and integrity

L2tp ipsec


  • Uses IPsec Encapsulating Security Payload (ESP)

  • an IPsec Authentication trailer provides message integrity and authentication

  • Structure of encrypted packet:

L2tp ipsec vs pptp

L2TP/IPsec vs. PPTP

Thank you

Thank You!

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