Wireless Hacks

BSS Versus IBSS

BSS/Master/AP/Infrastructure/IBSS/Ad-Hoc/Peer-to-Peer: these all refer to 802.11b operating modes, but what does it all mean?

802.11b (see [Hack #3] ) defines two possible (and mutually exclusive) radio modes that stations can use to intercommunicate. Those modes are BSS and IBSS.

BSS stands for Basic Service Set. In this operating mode, one station (the BSS master , usually a piece of hardware called an access point ) acts as a gateway between the wireless and a wired (likely Ethernet) backbone. Before gaining access to the wired network, wireless clients (also called BSS clients) must first establish communications with an access point within range. Once the AP has authenticated the wireless client, it allows packets to flow between the client and the attached wired network, either routing traffic at Layer 3, or acting as a true Layer 2 bridge. A related term, Extended Service Set (ESS), refers to a physical subnet that contains more than one access point (AP). In this sort of arrangement, the APs can communicate with each other to allow authenticated clients to “roam” between them, handing off IP information as the clients move about. Note that (as of this writing) there are no APs that allow roaming across networks separated by a router.

IBSS (Independent Basic Service Set) is frequently referred to as Ad-Hoc or Peer-to-Peer mode. In this mode, no hardware AP is required. Any network node that is within range of any other can communicate if both nodes ...