The 802.11 MAC is implemented by a
combination of hardware and software.
4 Opportunities for Distinction
There are several attributes about an RI that o?®er opportunities for distinction.
Below, we discuss how the architectural design, the implementation of
the 802.11 standard, and the setting of configurable parameters contribute to
the identification of a wireless system.
4.1 Software/Hardware Split
For the RI, an important performance factor is the amount of time it takes the
interface to process a packet in its send queue and start the physical transmission
over the airwaves, called the packet servicing time. Deciding how
to split the implementation of the RI between hardware and software is at
the discretion of the manufacturer and greatly impacts this parameter. Driver
software makes it cheaper and easier to upgrade the functionality of the NIC,
but it requires the resources of the host because it is embedded in the kernel
space of the operating system (OS). An RI with dedicated hardware seeks
to minimize intervention and utilization of the host which reduces the packet
servicing time. In contrast, an architecture that relies on the resources of the
host introduces additional latencies associated with the host, such as the overhead
caused by interrupt handling and OS transitions to honor the requests
of the RI. Consider the case where an RI uses a dedicated hardware engine to
perform packet encryption instead of implementing it in software.
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