Latency versus Packet Buffering for Ethernet
As developers integrate the Media Access Controllers (MAC) into their Ethernet design, they must make a choice as to how they want to buffer the data stream. The two most popular options are the use of latency buffers or the use of packet buffers. Each type of buffering scheme includes advantages and disadvantages that must be weighed in order to select the most efficient use of system resources. This paper examines how each choice affects the bandwidth requirements needed to handle the data flow, what the restrictions are that the choice places on the system CPU, and how to determine the amount of memory needed to implement the preferred scheme.
This paper focuses on the advantages of using a packet based buffer over a latency buffer because of the lower requirements placed on the system CPU in terms of bus allocation and the transfer of unnecessary data. While a latency buffer provides lower gate counts due to smaller memory sizes, it requires more software intervention and system resources to accomplish the same goals provided by a packet based buffer.
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