March 2004 doc IEEE 802 11 040412 r

March 2004 doc. : IEEE 802. 11 -04/0412 r 0 Thinking About the Site Report Bernard Aboba Microsoft bernarda@microsoft. com Dan Harkins Trapeze Networks Areg Alimian Communication Machinery Corporation aalimian@cmc. com Marty Lefkowitz OTCS Consulting Submission 1 Bernard Aboba Microsoft

March 2004 doc. : IEEE 802. 11 -04/0412 r 0 Outline • • • What is a site report? Query and response semantics Why the site report matters to handoff Issues with the site report Summary Submission 2 Bernard Aboba Microsoft

March 2004 doc. : IEEE 802. 11 -04/0412 r 0 What Is A Site Report? • A report on relating to WLAN-enabled stations within a site • Possible questions – What stations have transmitted in the past – and on what channels – What stations are transmitting now – and on what channels – Characteristics of the stations • Location and transmit power • Capabilities • Authenticated vs. rogues • Connectivity – to what prefixes do they offer access? • Why is this important? – To regain control over radio spectrum usage. – To inventory WLAN capable devices. – To provide information to stations wishing to better utilize the network. – Information != control; the site report creates no obligation to act. Submission 3 Bernard Aboba Microsoft

March 2004 doc. : IEEE 802. 11 -04/0412 r 0 Query and Response Semantics • Query and response semantics are very important – Querying station may have differing objectives and goals • Diagnostics: May wish to gather data on problems it is experiencing • Optimization: May wish to optimize its own performance • Inventory: May wish to inventory and map the network – In dense deployments, the entire site report may be quite long – Querying station may only need a subset of the entire report • May only care about stations “on this floor” in a given direction • May only care about stations “authenticated by the responder” • May only care about stations matching a set of capabilities Submission 4 Bernard Aboba Microsoft

March 2004 doc. : IEEE 802. 11 -04/0412 r 0 Handoff Scenario Channel 11 Channel 6 c v D AP B STA AP A Latency Contributors 802. 11 scan 802. 1 X authentication 4 -way handshake Movement detection Address assignment Duplicate detection IKE renegotiation MIP signalling TCP adjustment period c ~ 10 -20 ft D ~ 100 -300 ft Submission 5 Bernard Aboba Microsoft

March 2004 doc. : IEEE 802. 11 -04/0412 r 0 Why the Site Report Matters to Handoff • Site Report enables stations to optimize scan behavior – No need to scan on channels/technologies with no potential APs – No need for admin to configure stations for optimal scan behavior – Saves power, reduces handoff time, decreases radio spectrum pollution • Site Report enables stations to identity a potential candidate list prior to entering the coverage overlap area – Relevant dimension changed from “c” to “D” – Coverage overlap can be decreased, reducing interference issues • Site report increases maximum potential station velocity – Consequence of changing length metric from “c” to “D” • Site Report enables stations to decrease total handoff time Submission 6 Bernard Aboba Microsoft

March 2004 doc. : IEEE 802. 11 -04/0412 r 0 Rate 802. 11 Handoff Problem Space B DT Scan + Pre-auth via Old AP Scan + Radio tuning Pre-Auth + Site Report D DTPA c DTPA Stationary Submission 4 -way hand. , no 802. 1 X Pedestrian Vehicular Station Velocity 7 3 -way hand. , no 802. 1 X D DTFH Association not possible D DTReassoc High Speed Bernard Aboba Microsoft

March 2004 doc. : IEEE 802. 11 -04/0412 r 0 Issues with the “Site Report” • “Site report” may or may not be useful in formulating a “candidate list” – Depends on the query semantics – A list of all APs, or APs meeting criteria to be valid roaming candidates? • Site Report Response uses mgmt action frames which are not secured in the current specification. • Even if the STA has the BSSID of the AP to preauthenticate to, it needs to be within the AP’s coverage area to reassociate. • Without targeted queries, site report may not narrow the roaming candidates – “Site Report” may contain unsuitable roaming candidates – SNR is necessary to choose between roaming candidates – Using a “site report” as a “candidate list report” may cause the station to preauthenticate to more APs, increasing load. Submission 8 Bernard Aboba Microsoft

March 2004 doc. : IEEE 802. 11 -04/0412 r 0 Issues (cont’d) • Duplication of the “site report” in other protocols – Tempting to duplicate the functionality in other protocols, if support is not sufficiently comprehensive – Better to have one way to satisfy all “site report” needs, rather than multiple standard ways • Vendor extensions – OK to “add value” but… – Basic elements of the response need to be interoperable – Semantics of the response cannot be vendor-specific, only data Submission 9 Bernard Aboba Microsoft

March 2004 doc. : IEEE 802. 11 -04/0412 r 0 Summary • The site report matters. – In Diagnostics. – In Inventory. – In performance optimization. • Defining the semantics of queries and responses is important. • Getting a single facility rather than multiple ones should be a goal. – Removing critical functionality does not decrease workload or speed up completion, if you have to implement something multiple times. Submission 10 Bernard Aboba Microsoft

March 2004 doc. : IEEE 802. 11 -04/0412 r 0 Feedback? Submission 11 Bernard Aboba Microsoft