On Monday, November 12, 2012 11:15:56 AM Johannes Berg wrote: > Ok, can you elaborate on the differences between PCP and AP, and their > clients? I haven't had time to dig through the draft again What comes to my mind: PBSS is new type of BSS introduced by 60g spec. Partially, it sorts out mess associated with IBSS; partially it helps to address 60g specifics. PBSS is such a hybrid between ESS (infrastructure BSS) and IBSS. PBSS can be established only with DMG (60G) stations. PBSS features: ===Similar to IBSS=== - PBSS is ad-hoc network. Data frames use FromDS/ToDS combination 0/0 - stations communicate directly with each other. - security: every STA implement both authenticator and supplicant roles - STA use GAS to gather info about other STA's in the same PBSS ===Similar to ESS (infrastructure BSS)=== - there is dedicated coordination point, named PCP. - PCP manages joining to the PBSS (association flow) - only PCP transmits beacons. (in IBSS - every one) - up to 254 STA may be associated with PCP (in IBSS - unlimited) - PCP enforce uniform security policy (in IBSS each STA can enforce its own) ===Other=== - BSS type defined in beacon/probe resp etc. - there is a protocol, called "PCP negotiation" that allows 2 STA to decide who will accept role of PCP, based on specific scan procedure. They compare "PCP factors" - something similar to P2P intents, but composed of various capability bits. Most importand bit is "AC powered" - if 1 STA is AC powered while 2-nd is battery powered, AC powered will be elected as PCP. And so on - idea is to elect more capable STA as PCP. - there is no multicast in DMG network, since all data transmissions are directed. Due to this, if STA need to send mcast/bcast frame, it duplicates it for every STA within PBSS. - there is protocol for PCP hand-off - in 60g, P2P_GO is PCP by definition To summarize client's POV: - you know whether it is AP or PCP from scan results - you associate with AP and PCP in the same way - you set FromDS/ToDS bits differently for PCP and AP - for PCP, you yse GAS to discover other STA's (query PCP) - for PCP, you transmit to every STA in your PBSS directly - for PCP, you duplicate Tx multicast frame for each STA. -- To unsubscribe from this list: send the line "unsubscribe linux-wireless" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
