QoS Cisco IOS

Here is a script to optimise one end of an IAX over SDSL link.
It is designed to achieve two goals:
1. prevent the SDSL link to my company from getting saturated
2. keep 96kbps of traffic available at all times to VOIP traffic.

Notes:

Access List 105 matches any udp/4569 (IAX2) traffic
Access List 2128 matches any traffic for my company
You can only shape TCP traffic, since it will back off if packets are dropped.
You cannot shape UDP traffic, but you can rate-limit the router’s OUTPUT of any kind of traffic. This is why it is best to try and have control over BOTH ENDS of your link.

class-map voice
match access-group 105

policy-map policy1
class voice
priority 96
class class-default
fair-queue

interface e0/0
rate-limit input access-group 105 128000 65536 65536 conform-action
set-prec-transmit 5 exceed-action set-prec-continue 0
rate-limit output access-group 105 128000 8000 8000 conform-action
set-prec-transmit 5 exceed-action continue
rate-limit output access-group 2128 640000 1500 2000 conform-action
set-prec-transmit 1 exceed-action continue
rate-limit output access-group 2128 64000 1500 2000 conform-action
set-prec-transmit 1 exceed-action drop
full-duplex
service-policy output policy1

interface s0/0
rate-limit input access-group 105 128000 65536 65536 conform-action
set-prec-transmit 5 exceed-action set-prec-continue 0
rate-limit input 1408000 8000 8000 conform-action transmit exceed-action drop
service-policy output policy1

access-list 105 remark VOIP (IAX2) traffic gets top priority (5)
access-list 105 permit udp any any eq 4569

NB The other end of this link is controlled by Linux – see QoS Linux

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