Network Selection Issues Pasi Eronen

Network Selection -- Goals Assist AAA routing in global roaming, when full routing information not available or ambiguous Allow the user to select which broker to use, in case there are price or other differences Allow the intended service providers to be a part of the transaction business-wise

Network Selection -- Some Solutions AAA layer: some mechanism to provide a better AAA routing / roaming table Link layer: advertise an SSID for the broker/intermediate network, then use that in AAA routing, using virtual AAA clients and proxies EAP layer: provide some hints in EAP identity request, select a NAI based on those hints A regular NAI A NAI with the broker’s name added jarkko%piuha.net@ipass.com Another alternative decoration: ipass/jarkko@piuha.net

Issues with NAI Prefix / EAP Solution All proxies have to know about this Diameter routing and Diameter-RADIUS problems Does not work this way according to the current RFCs APs have to be modified to get the initial ID request from the proxy, or identity re-queries are needed, lengthening the network attachment time Does not help in selecting the AP Need to scan of all APs and running EAP before deciding which AP to choose EAP Identity Req/Resp contents are not secured

The SSID Solution No AAA protocol implications No EAP or NAI interoperability issues Does require APs to support multiple SSIDs If the number of advertised networks is large, can consume a lot of beacon bandwidth At 1 mbps, all bandwidth used for 100 network advertisements! A similar issue with the EAP/scan solution, but not dependent on number of networks -- instead, the number of logins per second x number of APs However, in the EAP/scan solution a higher speed can be chosen for the unicast communications For instance, 10 logins per second with 10 APs and 100 networks, with 10 mbps unicast speed would result in 10 * 10 * 10000 = 1 mbps or 10% of the bandwidth used

Feedback on Network Selection If an EAP-layer based solution is used, EAP identity request hints are probably OK Prefix-based NAI decoration is problematic AAA routing instructions from RFCs are violated All proxies have to recognize the decoration Suffix-based NAI decoration would be better Neither the hints or the decorations are authenticated Applies to SSIDs in part too, at least for dishonest AP case Scanning APs and trying EAP is problematic Particularly hard if there are multiple APs and fast roaming And particularly if identity re-query is used Consider combining AP selection and network selection? Beacon-based approach is limited to ~dozen brokers Particularly if lowest beaconing speed is small