Virtual Private NetworksVirtual Private Networks

Alberto Pace

IT/IS Technical Meeting – January 2002

What is a VPN ?What is a VPN ?

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

IT/IS Technical Meeting – January 2002

What is a VPN ?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

IT/IS Technical Meeting – January 2002

Point-to-Point Tunneling ProtocolPoint-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)

IT/IS Technical Meeting – January 2002

Layer Two Tunneling ProtocolLayer 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

IT/IS Technical Meeting – January 2002

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

IT/IS Technical Meeting – January 2002

Authentication MethodsAuthentication Methods

Challenge Handshake Authentication Protocol (CHAP) Uses Message Digest 5 (MD5) / challenge-response

MS-CHAP 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

IT/IS Technical Meeting – January 2002

Types of VPNsTypes of VPNs

Router-to-Router

IT/IS Technical Meeting – January 2002

Types of VPNsTypes of VPNs

Remote Access VPNs

IT/IS Technical Meeting – January 2002

Tests at CERNTests at CERN

PCAP7 (computer in my office)

IT/IS Technical Meeting – January 2002

From the clientFrom the client

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

The page http://cern.ch/Win/Temp/vpn.asp considers intranet the address 137.138.32.xxx

IT/IS Technical Meeting – January 2002

Connect to the VPNConnect to the VPN

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

IT/IS Technical Meeting – January 2002

Try to connectTry to connect

IT/IS Technical Meeting – January 2002

Conclusions so farConclusions so far

If we open the pptp port on address 137.138.33.62, 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)

IT/IS Technical Meeting – January 2002

More conclusion so farMore 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.