IPsec

IP Security

• Layer 3 and 4 protocol
• Standards-based
  • Widely supported
• Framework
• Provides confidentiality & integrity
  • Once you authenticate everything is gonna be encrypted
  • What gives you integrity?
    • Hashing or Digest
• Tunneling like GRE
• IP only
  • Unlike GRE which supports everything
• Commonly used in Virtual Private Networks

Types of VPN

• We do not know where our users are going to connect from
• An alternative to IPsec is called TLS/SSL which uses port TCP 443 sharing port with HTTPS.
  • It is easier to use TLS/SSL
• Site-to-site uses IPsec always.

How two routers build a VPN session?

• From Tampa to Orlando
• From side A to side B
• A sends traffic into its router
  • Hey router if you see an envelope source from here to that other IP
  • How do you encrypt it? maybe you use: AES or SHA256.
• Router A is going to call router B using port UDP 500
  • This is called a management session and establishes encryption between the two routers
• In phase 2 this is where we set up our communications with IPsec data essays.
  • If one of the other sides is misconfigure, if they both do not have a matching the tunnel is not formed, they have to exactly math specifications.