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Pretty Good Handoffs

Pretty Good Handoffs. Dan Harkins Trapeze Networks. Pretty Good Handoffs. This group has not defined the word “fast” How do we know whether a proposal is actually a solution to the problem then? But the ITU has: it’s 50ms The number was not PDOOMA’d

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Pretty Good Handoffs

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  1. Pretty Good Handoffs Dan Harkins Trapeze Networks Dan Harkins, Trapeze Networks

  2. Pretty Good Handoffs • This group has not defined the word “fast” • How do we know whether a proposal is actually a solution to the problem then? • But the ITU has: it’s 50ms • The number was not PDOOMA’d • Is a 50ms handoff “fast” for us? Is it possible to even do? Dan Harkins, Trapeze Networks

  3. Pretty BAD Handoffs • Current handoffs are S-L-O-W • Charles Wright showed (in 0989) handoffs from 2-8 seconds even without security! • Reasons • Active scanning is chewing up a significant portion of the handoff latency budget (shown by Areg Alimian and Bernard Aboba showed in 0377), especially bad for a/b/g devices • Doing an full 802.1X reauthentication is expensive • 802.1X implementations and OSs are not optimized to do an efficient 4way handshake Dan Harkins, Trapeze Networks

  4. Pretty Good Handoffs • What can be done to fix the problem with handoff latencies • Optimize the scanning function! Not in our charter, but is in TGk’s. And TGk is already addressing this problem. • Don’t do a full 802.1X reauthentication when handing off! Cache PMKs and just do a 4 way handshake. • Fix our 802.1X implementations to “fast switch” packets for the 4way handshake through our kernels. Dan Harkins, Trapeze Networks

  5. Pretty Good Handoffs • Independentanalysis (Bill Arbaugh from Univ of Maryland) shows it is feasible to do a 4 way handshake in under 25ms. • “neighbor list” from TGkcan give a STA a list of valid APs to which a handoff should be made. This can drastically reduce scan times. • Possible to fit an optimized scan and 4way handshake in a 50ms budget without any protocol changes (and with room to spare)! • That’s a “Pretty Good” handoff Dan Harkins, Trapeze Networks

  6. Pretty Good Handoffs • What about QoS? (note to presenter: wave hands here) • Need some way to set up service (TSPECS) prior to handoff • TGk should help with identification of valid APs prior to handoff • This is something TGr should solve • What other kinds of state needs to be transferred, how long does it take to set-up and how critical is it? • Not sure at this point but security state is NOT one Dan Harkins, Trapeze Networks

  7. Pretty Good Handoffs • Benefits of PGH • No new key hierarchies • No new or overloaded management frames • No change to ASs necessary • Does not break, change, or modify the way existing protocols work • Cuts down on code bloat • 100% KISS-compliant! • It satisfies this TG’s definition of “fast” • No new protocol necessary • Drawback of PGH • No new protocol necessary Dan Harkins, Trapeze Networks

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