System Examples

Question 1

What is a WISP in an WIFI hotspot?

Answer 1

A captive portal (may include auth server).

It is used before the routing to authenticate clients

Question 2

Why do we need authentication for WiFi hotstop and how can we realize it?

Answer 2

We need auth for privacy protection, billing purposes and legal reasons

We can use L2 (WPA), L3 (IPsec, PPTP) or L4 (captive portals)

Question 3

How can a client be redirected to a captive portal?

Answer 3

• ICMP redirect
• DNS spoofing
• Terminating TCP connections
• HTTP redirect

Question 4

How does eduroam handle authentication?

Answer 4

Via 802.1X and country-level RADIUS servers using user certificates and end-to-end tunneling

Question 5

Name some characteristics for train wifi networks

Answer 5

• Mulitple cellular interfaces
• Wifi for access in train stations
• Mobility is predefined by the train trcks
• 2-tier network access: mobile operator for WAN, backend service provider for train