FIFO Queueing - first in first out, no change in packet order. Just like a line at the bank
There is a single queue per interface.
There is no change in response to traffic.
It is the default queueing on non serial interfaces that are as fast as a T1 or above.
Its not recommended for X.25, SDLC, or compressed ppp.
It's the fastest queueing method utilising the least router resources.
No Starvation
All traffic could fail if network is saturated
Weighted Fair Queueing -Cisco algorythim that chooses packet priority. Just like triage in an emergence room more immeadiate traffic moves to the front of the line
WFQ adapts to changes in traffic
There is a single queue per interface with Cisco automagically choosing packet order.
Default queueing method for everything else (ie. serial and below T1)
Slower than FIFO
Small packets and low volume traffic go to the head of the queue.
Uses stateful inspection and conversations to classify traffic
Bandwidth is shared for remaining traffic
Starvation improbable, Failures improbable
Priority Queueing -Administrative control
:
4 queues: High, Medium, Normal, Low
No change in response to traffic
Slower than Weighted fair.
Must be programmed
High queue is emptied before any other queues are considered
Starvation is possible and likely if you have a lot or bursty high priority traffic
Custom Queueing -Administrative control
16 queues (10 in IOS 11.1 or earlier
No change in response to traffic
Just a guess that it's the slowest method
May have from 1 to 16 queues
Must be programmed
Doesn't empty queue before servicing other queues
Services queue in chunks (byte count) in order so every queue gets visited
Default byte count is 1500 ( same as Ethernet MTU )
Starvation is not possible but all traffic can become lagged in a saturated network.
*FIFO
(config-if)#FIFO
*weighted fair
(config-if)#fair-queue{congestive-discard-threshold}
*Priority
(config-if)#priority-group group_number(1-16)
(config)#priority-list list-number protocol protocol-name {high | medium | normal | low} queue-keyword
keyword-value
list-number interface interface-type interface-number {high | medium | normal | low}
(config)#priority-list list-number default {high | medium | normal | low}
*optional commands
!command to change the max number of packets in each queue.
(config)#priority-list list-number queue-limit high-limit medium-limit normal-limit low-limit
!default 20 40 60 80
!queue-keyword values
fragmens--number of fragments
gt--port num
lt--port num
list---access list
tcp--port num
udp--port num
*Custom
(config-if)#custom-queue-list list_number(1-16)
(config)#queue-list list-number protocol protocol-name {high | medium | normal | low} queue-keyword keyword-value
(config)#queue-list list-number interface interface-type interface-number queue-number
(config)#queue-list list-number default queue-number
-optional commands
!specify the max number of packets for a particular queue (limit-number 0 - 32,767)
(config)#queue-list list-number queue queue-number limit limit-number
!if max number of packets are set too low you will drop the excess traffic!!!!
!default limit-number is 20
(config)#queue-list list-number queue queue-number byte-count byte-count-number
!default byte count is 1500