Tail drop – Allied Telesis AlliedWare Plus Operating System Version 5.4.4C (x310-26FT,x310-26FP,x310-50FT,x310-50FP) User Manual

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Quality of Service (QoS) Introduction

Software Reference for x310 Series Switches

C613-50046-01 REV A

AlliedWare Plus

Operating System - Version 5.4.4C

38.25

Tail Drop

In this drop mode each egress queue is configured with a maximum threshold value. This
value represents the point where the egress buffer queues are full and the egress port
must start dropping data. The port does this by dropping data packets destined for the
full queue on a “last in first dropped” basis. This enables the port to clear its data already
queued for egress.

If a reliable transport protocol, such as TCP is used, this data should be retransmitted, but
at a slower rate due to lack of returning “acknowledgments”.