TECHNOLOGY TODAY

When a client device tries to join a new network for the very first time, it must have a valid IP address to communicate. It first transmits a DHCPDISCOVER message on its local subnet. Because the client has no way of knowing the subnet to which it belongs, the DHCPDISCOVER is an all-subnets broadcast (destination IP address of 255.255.255.255, a layer 3 broadcast address) and a destination MAC address of FF-FF-FF-FF-FF-FF (a layer 2 broadcast address). The client does not have a configured IP address, so the source IP address of 0.0.0.0 is used. The purpose of  DHCPDISCOVER message is to try to find out a DHCP Server. After receiving the discover message, the DHCP Server dynamically picks up an unassigned IP address from its IP pool and broadcasts a DHCPOFFER message to the client device. DHCPOFFER message could contain other information such as subnet mask, default gateway, IP address lease time, and domain name server (DNS). In fact, the DHCPOFFER is...

Over the past two decades, the demand for wireless service has grown at an extraordinary pace. The industry has grown from pagers, and  cellular phones  to Personal Communication Systems (PCS) and wireless local area networks (WLANs), providing services that deliver voice, data, and video in real time.  For some time, wireless communications have been evolving from voice and low data rate services towards high bit rate services like video-telephony and multimedia). In addition, wireless-in-house communications with a high degree of mobility are also emerging rapidly. Wi-Fi Access Points are being installed in almost every conceivable location from public areas such as airports, coffee bars to private homes and even on the masts of boats. The performance of wireless communication systems depends on the radio wave transmission path between the transmitter and the receiver. Unlike their wired counterparts whose distance limitations and data rates are fully understood due ...