Virtual private networks
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Virtual Private Networks. Alberto Pace. What is a VPN ?. A technology that allows to send confidential data securely over the internet. What is a VPN ?. The remote computer can connect to the internet using an arbitrary Internet Service Provider (ISP) and have an IP Address in the intranet.

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Virtual Private Networks

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Virtual private networks

Virtual Private Networks

Alberto Pace

What is a vpn

What is a VPN ?

  • A technology that allows to send confidential data securely over the internet

What is a vpn1

What is a VPN ?

  • The remote computer can connect to the internet using an arbitrary Internet Service Provider (ISP) and have an IP Address in the intranet.

  • The computer can act as if it was on the intranet

Point to point tunneling protocol

Point-to-Point Tunneling Protocol

  • You can access a private network through the Internet or other public network by using a virtual private network (VPN) connection with the Point-to-Point Tunneling Protocol (PPTP).

  • Developed as an extension of the Point-to-Point Protocol (PPP),

  • PPTP tunnels or encapsulates, IP, IPX, or NetBEUI protocols inside of PPP datagrams

  • PPTP does not require a dial-up connection. It does, however, require IP connectivity between your computer and the server

  • My understanding is that it uses Microsoft Point-to-Point Encryption (MPPE)

Layer two tunneling protocol

Layer Two Tunneling Protocol

  • L2TP is an industry-standard Internet tunneling protocol with roughly the same functionality as the Point-to-Point Tunneling Protocol (PPTP).

  • Like PPTP, L2TP encapsulates Point-to-Point Protocol (PPP) frames, which in turn encapsulate IP, IPX, or NetBEUI protocols

  • With L2TP, the computer performs all security checks and validations, and enables data encryption, which makes it much safer to send information over nonsecure networks by using the new Internet Protocol security (IPSec)

  • In this case data transfer through a L2TP-enabled VPN is as secure as within a single LAN at a corporate site

Internet protocol security ipsec

Internet Protocol security (IPSec)

  • IPSec provides machine-level authentication, as well as data encryption.

  • IPSec negotiates between your computer and its remote tunnel server before an L2TP connection is established, which secures both passwords and data

Authentication methods

Authentication Methods

  • Challenge Handshake Authentication Protocol (CHAP)

    • Uses Message Digest 5 (MD5) / challenge-response


    • Same as Chap + functionality to which LAN-based users are accustomed

    • MS-CHAP is consistent with standard CHAP (superset of functionalities)

    • You must at least use MS-CHAP to use MPPE (encryption)

  • MS-CHAP v2

    • both the client and the server prove their identities. Not only the client. V2 ensures that you can configure a your connection can be configured to connect to the expected server

  • Extensible Authentication Protocol (EAP)

    • Allows to use other security devices. EAP provides a standard mechanism for support of additional authentication methods within PPP including token cards, one-time passwords, public key authentication using smart cards, certificates, and others

Types of vpns

Types of VPNs

  • Router-to-Router

Types of vpns1

Types of VPNs

  • Remote Access VPNs

Tests at cern

Tests at CERN

  • PCAP7 (computer in my office)

From the client

From the client

  • The machine we have in on the intranet only. We have to simulate internet/intranet.

  • The page considers intranet the address

Connect to the vpn

Connect to the VPN

  • From “My Network Places” – Right-Click – “Properties” – “Create New Connection”

Try to connect

Try to connect

Conclusions so far

Conclusions so far

  • If we open the pptp port on address, we have today a working solution with the following limitations

    • Uses PPTP and Microsoft Point-to-Point Encryption

      • Windows computer have all necessary software natively

    • Windows Machines can be identified (as member of the domain or an ad-hoc domain)

    • Security is strengthened by domain logon that can be tightened to anything you want

  • This is the current “industry standard”

    • Used world-wide, secure and proven technology

    • Evolution towards L2TP and IPSec coming, but slowly (requires heavy infrastructure)

More conclusion so far

More conclusion so far

  • Using this technology, we could open rapidly a VPN service for WINDOWS users

    • Time to install and configure the VPN server ~ 8 hours

    • Time to install a windows client that has already TCP/IP connectivity ~ 1 minute

  • Support for Linux users could come for the “community”

    • May be very expensive to formally support Linux clients

    • Not a standard technology – to my knowledge, no companies have “roaming linux users” on the internet to the same extent that we have

  • Deploying the IPsec infrastructure to support L2TP will require an administrative office to distribute, revoke and maintain computer certificates and user certificates.

    • May not be possible within the current resources / May require several years

    • Yet another computer Registration ? Yet another user Registration ?

      • Should try to have LANDB and CCDB moving in this direction. Only if this happens the investment can be justified.

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