title: Why Beacon needed when there is probe response
body: <p>I was trying to understand the use of beacon and probe response in 802.11 network. If advertising the existence of a AP is only the goal, then why beacon frame needed? Passive scanning may be important while the station is in roaming but is it the only usage of beacon frames? Please clarify what other purposes does this frame serve in a typical 802.11 network.</p>