05-28-2008 09:29 AM - edited 03-15-2019 10:56 AM
All,
Can someone put this into plain english for me?
mls qos map policed-dscp 0 24 to 8
mls qos map cos-dscp 0 8 16 26 32 46 48 56
Thanks
Solved! Go to Solution.
05-28-2008 10:03 AM
This is the untrusted scavanger model as discussed in the QoS SRND. Basically it allows only 128 kbps for voice traffic (RTP) per switchport, which is perfect unless you are using Barge feature, as G711 codec will never use this much badnwidth anyway, so the idea here is to protect the network from possible worms, etc simulating voice traffic. Anything above 128 K will be dropped, similarly with the signaling traffic, IPCC desktop, etc where exceeding traffic will be re-marked to the DSCP 8 value. Then on your WAN interfaces you probably have a policy that (LLQ) that matches traffic with dscp of 8 and gives it very small bucket, so that it does not starve out other traffic crossing the link.
HTH, please rate all useful posts!
Chris
05-28-2008 09:43 AM
This is just a part of full QoS configuration.
The first line re-marks all packets with DSCP value of 0 or 24 to 8, you still need to apply a policer to a port in order for this to take affect, so if based on your policy a packet needs to be remarked it will be remarked from 0 or 24 to 8, this is to create a scavanger class for further limiting.
The second line maps L2 COS markings to L3 DSCP vlaues, this will map the following:
COS DSCP
0 --> 0
1 --> 8
2 --> 16
3 --> 26
4 --> 32
5 --> 46
6 --> 48
7 --> 56
Check out QoS SRND at www.cisco.com/go/srnd for more details
HTH,
Chris
05-28-2008 09:58 AM
Ok,
Here is our policy/class:
service-policy input IPPHONE+PC-BASIC
srr-queue bandwidth share 1 25 70 5
srr-queue bandwidth shape 3 0 0 0
priority-queue out
policy-map IPPHONE+PC-BASIC
class VVLAN-VOICE
set dscp ef
police 128000 8000 exceed-action drop
class VVLAN-CALL-SIGNALING
set dscp cs3
police 32000 8000 exceed-action policed-dscp-transmit
class VVLAN-ANY
set dscp default
police 32000 8000 exceed-action policed-dscp-transmit
class AGENT-DESKTOP-TRAFFIC
set dscp cs3
police 256000 8000 exceed-action policed-dscp-transmit
class class-default
set dscp default
police 5000000 8000 exceed-action policed-dscp-transmit
I'm not sure how the qos map works with the policy?
Thanks again.
05-28-2008 10:03 AM
This is the untrusted scavanger model as discussed in the QoS SRND. Basically it allows only 128 kbps for voice traffic (RTP) per switchport, which is perfect unless you are using Barge feature, as G711 codec will never use this much badnwidth anyway, so the idea here is to protect the network from possible worms, etc simulating voice traffic. Anything above 128 K will be dropped, similarly with the signaling traffic, IPCC desktop, etc where exceeding traffic will be re-marked to the DSCP 8 value. Then on your WAN interfaces you probably have a policy that (LLQ) that matches traffic with dscp of 8 and gives it very small bucket, so that it does not starve out other traffic crossing the link.
HTH, please rate all useful posts!
Chris
05-28-2008 10:07 AM
One last question: what happens to a PC/server that is plugged into the switch port with that policy? Does it drop packets over 128k, or since that traffic is on a different vlan, it is safe?
Thanks
05-28-2008 10:17 AM
It will drop the traffic if it arrives marked with DSCP 46 (ef), for regular non marked data traffic it will obey the defaul map, which mean that everything over 5 Mb gets remarked down to scavanger, so if you are transmitting a lot of files on a PC this may cause a bottleneck.
Chris
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