1. IPSec VPN Chapter 13 of Malik

2. http://sce.uhcl.edu/yang/teaching/.../VPN.ppt 2 Outline Types of IPsec VPNs IKE (or Internet Key Exchange) protocol

3. http://sce.uhcl.edu/yang/teaching/.../VPN.ppt 3 Types of IPsec VPNs Site-to-site (aka LAN-to-LAN) IPsec VPN Figure 13-1 Question: no concentrator? Remote-access client IPsec VPN Figure 13-2 Unique challenges: (see p.317) 1.IPsec clients use unknown-to-gateway IP addresses to connect to the gateway 2.Client’s IP address assigned by the ISP is not compatible with the private network’s addressing. 3.The clients must use the DNS server, DHCP server, and other such servers on the private network. 4.PAT can no longer function as normal (because ESP encrypts all the port info in the TCP or UDP header).

4. http://sce.uhcl.edu/yang/teaching/.../VPN.ppt 4 Phases of IPsec 1.Connection initiated 2.IKE main mode or aggressive mode Results: a.creation of an IKE Security Association (SA) between the two IPsec peers b.A set of 3 session keys are established –Quick mode Results: a.creation of two IPsec SAs between the two peers (incoming SA and outgoing SA) b.Generate a pair of IPsec keys (one for each of the SAs) 3.Data communication (using ESP or AH)

5. http://sce.uhcl.edu/yang/teaching/.../VPN.ppt 5 IPsec Negotiation using IKE P.279: Authentication methods vs modes Preshared key Digital signature Encrypted nonces Main modepp. 280- 298 pp.298-302 Aggressive mode pp.302- 306

6. http://sce.uhcl.edu/yang/teaching/.../VPN.ppt 6 IPsec Negotiation using IKE Example 1: Main mode using preshared key authentication followed by Quick mode negotiation pp.280-298 Example 2: Main mode using DS authentication followed by Quick mode negotiation pp.298-302 Example 3: Aggressive mode using Preshared key authentication (followed by Quick mode negotiation) pp. 302-306