1. Virtual Private Network (VPN)
SCSC 455

2. VPN
A virtual private network that is established over, in general, the Internet
It is virtual because it exists as a virtual entity within a public network
It is private because it is confined to a set of private users

3. Private Networks vs. Virtual Private Networks
Employees can access the network (Intranet) from remote locations.
Secured networks.
The Internet is used as the backbone for VPNs
Saves cost tremendously from reduction of equipment and maintenance costs.
Scalability

4. Why is it a Virtual Private Network?
From the user’s perspective, it appears as a network consisting of dedicated network links
These links appear as if they are reserved for the VPN client
Because of encryption, the network appears to be private

5. Typical VPN Connection

6. Tunnel and Connections
The portion of the network where the data is encapsulated
Connection
The portion of the network where the data is encrypted

7. Application Areas
In general, provide users with connection to the corporate network regardless of their location
The alternative of using truly dedicated lines for a private network are expensive propositions

8. Some Common Uses of VPN
Provide users with secured remote access over the Internet to corporate resources
Connect two computer networks securely over the Internet
Example: Connect a branch office network to the network in the head office
Secure part of a corporate network for security and confidentiality purpose

9. Remote Access Over the Internet

10. Connecting Two Computer Networks Securely

11. Basic VPN Requirements
User Authentication
VPN must be able to verify user authentication and allow only authorized users to access the network
Address Management
Assign addresses to clients and ensure that private addresses are kept private on the VPN
Data Encryption
Encrypt and decrypt the data to ensure that others on the not have access to the data
Key Management
Keys must be generated and refreshed for encryption at the server and the client
Multi-protocol Support
The VPN technology must support commons protocols on the Internet such as IP, IPX etc.

12. VPN Implementation Protocols
Point-to-Point Tunneling Protocol (PPTP) of Layer 2 Tunneling Protocol (L2TP)
IPSec

13. More on Tunneling
Tunneling involves the encapsulation, transmission and decapsulation of data packets
The data is encapsulated with additional headers
The additional headers provide routing information for encapsulated data to be routed between the end points of a tunnel

14. Tunneling

15. Point-to-Point Tunneling Protocol (PPTP)
Encapsulate and encrypt the data to be sent over a corporate or public IP network

16. Level 2 Tunneling Protocol
Encrypted and encapsulated to be sent over a communication links that support user datagram mode of transmission
Examples of links include X.25, Frame Relay and ATM

17. IPSec Tunnel Mode
Encapsulate and encrypt in an IP header for transmission over an IP network

18. Layer 2 Tunneling Protocols
PPTP
L2TP
Both encapsulate the payload in a PPP frame

19. Layer 3 Tunneling Protocol
IPSec Tunneling Mode
Encapsulates the payload in an additional IP header

20. Other Important Protocols in VPN
Microsoft Point-to-Point Encryption (MPPE)
Extensible Authentication Protocol (EAP)
Remote Authentication Dial-in User Service (RADIUS)

21. Some Example Scenarios
VPN remote access for employees.
On-demand branch office access.
Persistent branch office access.
Extranet for business partners.
Dial-up and VPNs with RADIUS authentication

22. Router-to-Router Branch Office Connection

23. VPN Based Extranet

24. Dial-up and VPNS with RADIUS Authentication