QoS 3850 PQ Level 1 reserved bandwidth by default

[Vsevolod Ruchin]

Hello everybody, 

I need to check that we have right configuration of QoS for Voice. 

We have configured Priority Queue Level 1 for EF traffic. 

Unfortunately I can't find anywhere how much bandwidth reserved for Level 1 by default. 

Here is the part of config for Cisco 3850 IOS XE 3.7:

policy-map QOS_EGRESS

 class VOICE

  priority level 1

Here is description of priority command from command reference:

Kb/s	(Optional) Guaranteed allowed bandwidth, in kilobits per second (kbps), for the priority traffic. The amount of guaranteed bandwidth varies according to the interface and platform in use. Beyond the guaranteed bandwidth, the priority traffic will be dropped in the event of congestion to ensure that the nonpriority traffic is not starved. The value must be between 1 and 2,000,000 kbps.
level level-value	(Optional) Assigns priority level. Available values for level-value are 1 and 2. Level 1 is a higher priority than Level 2. Level 1 reserves bandwidth and goes first, so latency is very low. Reserve the bandwidth even if you do not use it. Both levels 1 and 2 can reserve bandwidth.

Anyway Priority command reserves some amount of bandwidth by default. 

For 3850 there is no information in output of show commands to determine how much is reserved for interface by default. 

#sh policy-map interface g1/0/3
GigabitEthernet1/0/3

Service-policy output: QOS_EGRESS

queue stats for all priority classes:
Queueing
priority level 1

(total drops) 0
(bytes output) 2098464

Class-map: VOICE (match-any)
0 packets
Match: dscp ef (46)
0 packets, 0 bytes
5 minute rate 0 bps
Match: ip dscp ef (46)
0 packets, 0 bytes
5 minute rate 0 bps
Priority: Strict,

Priority Level: 1

Does anybody know the answer?

Regards, 

Vsevolod

[Georg Pauwen]

Hello,

priority level 1 goes into queue 0. What is the output of:

show platform qos queue config g1/0/3
show platform qos queue stats g1/0/3

[Vsevolod Ruchin]

Hi Georg, 

thank you for your reply. 

show platform qos queue config gigabitEthernet 1/0/3
DATA Port:11 GPN:881 AFD:Disabled QoSMap:1 HW Queues: 88 - 95
DrainFast:Disabled PortSoftStart:2 - 450
----------------------------------------------------------
DTS Hardmax Softmax PortSMin GlblSMin PortStEnd
--- -------- -------- -------- --------- ---------
0 1 6 75 8 300 7 200 0 0 4 600
1 1 4 0 8 300 7 200 3 75 4 600
2 1 4 0 8 300 7 200 3 75 4 600
3 1 4 0 8 300 7 200 3 75 4 600
4 1 4 0 5 0 5 0 0 0 4 600
5 1 4 0 5 0 5 0 0 0 4 600
6 1 4 0 5 0 5 0 0 0 4 600
7 1 4 0 5 0 5 0 0 0 4 600
Priority Shaped/shared weight shaping_step max_neg_res_idx
-------- ------------ ------ ------------ --------------
0 1 Shared 50 0 0
1 7 Shared 140 0 3
2 7 Shared 50 0 0
3 7 Shared 700 0 4
4 0 Shared 10000 0 2
5 0 Shared 10000 0 2
6 0 Shared 10000 0 2
7 0 Shared 10000 0 2

Weight0 Max_Th0 Min_Th0 Weigth1 Max_Th1 Min_Th1 Weight2 Max_Th2 Min_Th2
------- ------- ------ ------ ------ ------ ------ ------ ------
0 0 298 0 0 333 0 0 375 0
1 0 239 0 0 267 0 0 300 0
2 0 239 0 0 267 0 0 300 0
3 0 239 0 0 267 0 0 300 0
4 0 0 0 0 0 0 0 0 0
5 0 0 0 0 0 0 0 0 0
6 0 0 0 0 0 0 0 0 0
7 0 0 0 0 0 0 0 0 0

Max neg resource utilization
Index Weight Ref count max neg val
----- ------ --------- ----------
0 50 30 ffff614f
1 75 2 ffff11f7
2 10000 68 ff8405b8
3 140 14 fffe43aa
4 700 14 fff75252
5 0 0 0
6 0 0 0
7 0 0 0
8 0 0 0
9 0 0 0
10 0 0 0
11 0 0 0
12 0 0 0
13 0 0 0
14 0 0 0
15 0 0 ffffc000

show platform qos queue stats gigabitEthernet 1/0/3
DATA Port:11 Enqueue Counters
-------------------------------
Queue Buffers Enqueue-TH0 Enqueue-TH1 Enqueue-TH2
----- ------- ----------- ----------- -----------
0 0 0 0 2160967
1 0 0 0 0
2 0 0 0 0
3 0 0 0 0
4 0 0 0 0
5 0 0 0 0
6 0 0 0 0
7 0 0 0 0
DATA Port:11 Drop Counters
-------------------------------
Queue Drop-TH0 Drop-TH1 Drop-TH2 SBufDrop QebDrop
----- ----------- ----------- ----------- ----------- -----------
0 0 0 0 0 0
1 0 0 0 0 0
2 0 0 0 0 0
3 0 0 0 0 0
4 0 0 0 0 0
5 0 0 0 0 0
6 0 0 0 0 0
7 0 0 0 0 0
AQM Broadcast Early WTD COUNTERS(In terms of Bytes)
--------------------------------------------------
PORT TYPE ENQUEUE DROP
--------------------------------------------------
UPLINK PORT-0 N/A 0
UPLINK PORT-1 N/A 0
UPLINK PORT-2 N/A 0
UPLINK PORT-3 N/A 0
NETWORK PORTS 0 0
RCP PORTS 0 0
CPU PORT 0 0
Note: Queuing stats are in bytes

[Georg Pauwen]

Hello,

you need to compare the hardmax/softmax and assigned weight values with and without the service policy applied.

I don't want to be cheap, but the document below explains the queue buffer structure of the 3850, and what happens when you apply priority levels...

https://www.cisco.com/c/en/us/support/docs/switches/catalyst-3850-series-switches/200594-Catalyst-3850-Troubleshooting-Output-dr.html

[brselzer]

Hello,

You can manually configure the bandwidth if you are not sure:

3850(config-pmap-c)#priority level 1 ?
<8-100000000> Kilo Bits per second
percent % of total bandwidth
<cr> <cr>

Hope that helps!