TABLE OF CONTENTS Communications devices can differ significantly in their form factors for example, a cell phone is several times smaller than the telecommunications switch through which its calls may be switched. The following is a partial list of the popular forms for communications devices, along with some examples:
Host-based adapter a PCI Ethernet add-on card
A handheld device a cell phone or pager
A pizza box design a single processor or multi-processor switch or router
A chassis-based design a CompactPCI-based voice or data switch
Of these, the pizza box and the chassis designs are the most popular for communications devices in a network. The pizza box design is typically a single-board architecture with one or more processors. The chassis-based design has multiple boards plugged into a backplane which provides the communication among the boards.
A single-board/single-processor architecture is the simplest design. Here, both the control and data planes run on the only processor or CPU. In several cases, data plane acceleration could be provided by a hardware device, like a switching chipset (an ASIC). In these cases, hardware acceleration devices do not run software they are only configured by the software running on the central processor. An exception is the network processor, which typically runs microcode downloaded from the central processor.
The second type of architecture is the single-board/multi-processor architecture. The simplest example is the two-processor architecture, in which the control and management code run on Processor 1, and the data plane and services run on Processor...
