QoS | Tail-drops Packet

In my post before you can found 'tail-drops', in here I will share about it.

This is we (I & You *reader) talk about tail-drops packet in network as specially in interface network (Cisco). Do you ever hear tail-drops, let read about that

- tail-drops occur when the output queue is full, these are common drops, which happen when a link is congested
.input queue drop: main cpu is congested & cannot process packets (input queue is full)
.ignore: router ran out of buffer space
.overrun: cpu is congested & cannot assign a free buffer to the new packet
.frame errors: hardware-detected error in a frame-cyclic redundancy check (CRC), runt, giant

- tail drop limitations (tail drop avoided because it contains significant flaws:)
.tcp synchronization
.tcp starvation
.no differentiated drop

- tcp synchronization: tail drops cause many packets of many sessions to be dropped at same time, tcp session restart at same time (synchronized)
- tcp delay, jitter & starvation

- characteristic of tail-drops
.tail drop does not look at IP precedence
.constant high buffer usage (long queue) causes delay
.more aggresive flows can cause other flows to starve
.no differentiated dropping occurs