07-19-2015 08:03 AM - edited 03-05-2019 01:54 AM
Hello,
I would appreciate a "second opinion" whether the WAN ingress Parent Policy below will drop packets regardless if they are High Priority pkts (eg/ EF, AF41) or if they are best effort (DSCP 0) packets.
I have included a 'show policy-map interface' output which shows the Parent Policy dropping packets
I have attached the Child policy as well but my query is mainly focussed on the Parent Policy. The ios is version 15.1(4)M3 and the router is a 2911.
The background is that we having Video packet loss which is affecting the picture quality.
---
policy-map 20Mb_WAN_Parent_In
class class-default
police cir 20480000 bc 3840000 be 7680000
conform-action transmit
exceed-action drop
service-policy 20Mb_WAN_Child_In
show policy-map interface
GigabitEthernet0/0.1897
Service-policy input: 20Mb_WAN_Parent_In
Class-map: class-default (match-any)
177963787 packets, 104965314158 bytes
30 second offered rate 965000 bps, drop rate 0 bps
Match: any
police:
cir 20480000 bps, bc 3840000 bytes, be 7680000 bytes
conformed 177961960 packets, 104963180269 bytes; actions:
transmit
exceeded 1828 packets, 2133953 bytes; actions:
drop
violated 0 packets, 0 bytes; actions:
drop
conformed 965000 bps, exceed 0 bps, violate 0 bps
-------
Thanks in advance
S
Solved! Go to Solution.
07-21-2015 06:14 PM
Hello,
Yes, as I understand the Parent policer can drop any tipe of traffic (regardless of it's DSCP value). In this link (http://www.cisco.com/c/en/us/td/docs/routers/10000/10008/configuration/guides/qos/qoscf/10qhier.html#wp1041745) this behaviour is explained:
•Packet classification for the bottom-level child policy map occurs before the top-level policer acts on the traffic classes.
•Traffic policing at the top-level parent does not guarantee fairness in sharing bandwidth among the child classes. If packets from two different traffic classes arrive at the same rate and then go through a traffic policer, the output rates of the two classes might be different because the hierarchical input policer acts as an aggregate policer. The parent policer might drop packets in one class in favor of the other class. This situation can happen when the top-level policer has enough tokens when the packets for one class arrive, but does not have enough tokens left for the other class. Based on the arrival pattern of the packets, this pattern could continue indefinitely.
Basically, the Parent Policer acts on the aggregate traffic it receives from the child class, without any regards to the DSCP value.
You can see some information about this for your IOS Version in the following link (it referes to three-level hierarchy, but the same should apply to a two-level hierarchy): http://www.cisco.com/c/en/us/td/docs/ios-xml/ios/qos_plcshp/configuration/15-mt/qos-plcshp-15-mt-book/qos-plcshp-mod-cli-tlhp.html
Regards,
Luis
07-21-2015 06:14 PM
Hello,
Yes, as I understand the Parent policer can drop any tipe of traffic (regardless of it's DSCP value). In this link (http://www.cisco.com/c/en/us/td/docs/routers/10000/10008/configuration/guides/qos/qoscf/10qhier.html#wp1041745) this behaviour is explained:
•Packet classification for the bottom-level child policy map occurs before the top-level policer acts on the traffic classes.
•Traffic policing at the top-level parent does not guarantee fairness in sharing bandwidth among the child classes. If packets from two different traffic classes arrive at the same rate and then go through a traffic policer, the output rates of the two classes might be different because the hierarchical input policer acts as an aggregate policer. The parent policer might drop packets in one class in favor of the other class. This situation can happen when the top-level policer has enough tokens when the packets for one class arrive, but does not have enough tokens left for the other class. Based on the arrival pattern of the packets, this pattern could continue indefinitely.
Basically, the Parent Policer acts on the aggregate traffic it receives from the child class, without any regards to the DSCP value.
You can see some information about this for your IOS Version in the following link (it referes to three-level hierarchy, but the same should apply to a two-level hierarchy): http://www.cisco.com/c/en/us/td/docs/ios-xml/ios/qos_plcshp/configuration/15-mt/qos-plcshp-15-mt-book/qos-plcshp-mod-cli-tlhp.html
Regards,
Luis
07-22-2015 04:28 AM
Hi Luis,
Thank you very much for answering my question. That's very helpful and I can use it to report back to my managers.
regards
Suresh
07-22-2015 08:26 AM
Hello Suresh,
I'm glad I could help.
Regards,
Luis
Discover and save your favorite ideas. Come back to expert answers, step-by-step guides, recent topics, and more.
New here? Get started with these tips. How to use Community New member guide