Keeping Packets In-order
If two packets destined for the same output arrive back-to-back at one line card, they will be spread to two different buffers, which could have two different occupancies, and so the packets could be reordered by the time they are delivered to the output. Although reordering is legal, it is typically undesirable because TCP does not perform well with reordered packets.
By adding yet more latency and buffering, the load-balanced switch can maintain packet order within flows using only local information. One such algorithm is FOFF (Fully Ordered Frames First). FOFF has the additional benefits of removing any vulnerability to pathological traffic patterns, and providing a mechanism for implementing priorities.
Read more about this topic: Load-balanced Switch
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