what does 1P2Q1T, 1P6Q2T means in QOS?

[gavin han]

what does 1P2Q1T, 1P6Q2T means  in QOS?

[Mark Malone]

its how the interfaces queues traffic, different mods would have different abilities , show interfaces x/x capabilities should show it from memory ,   1 priority 6 standard queues 2 threshold queues for drops

[gavin han]

Thank you.

how does 1P6Q2T relates to number of classes in MQC? can I have any number of classes in MQC and put "priority bandwidth x%" for dscp ef so voice packets goes to the priority queue?

[Mark Malone]

the queueing 1P6Q2T  would be based on the hardware of what the module can do , its separate to the MQC which would be software side  and applied manually to the interface , the 1P6Q2T thats what its is how the actual interface logically sperates teh packets into queues your harwdrae queues should match though at some extent to your MQC in terms of how traffic is marked but there 2 very different parts of qos in how they work hardware and software

[gavin han]

Thanks Mark. what does "2T" stand for and what's its function? "1P" means 1 priority queue and "6Q" means 6 queues (including 1 priority queue), correct?

[Mark Malone]

Hi

See this link it will explain it further in detail but its the threshold or drop queues, WRED drop or Tail drop , it goes through the other queues too in the link

http://www.cisco.com/c/en/us/td/docs/switches/lan/catalyst6500/ios/15-1SY/config_guide/sup2T/15_1_sy_swcg_2T/qos_policy_based_queueing.html#pgfId-1005923

Tail-drop thresholds—On ports with tail-drop thresholds, frames with a given QoS label are admitted to the queue until the drop threshold associated with that QoS label is exceeded; subsequent frames of that QoS label are discarded until the threshold is no longer exceeded. For example, if CoS 1 is assigned to queue 1, threshold 2, and the threshold 2 watermark is 60 percent, then frames with CoS 1 will not be dropped until queue 1 is 60 percent full. All subsequent CoS 1 frames will be dropped until the queue is less than 60 percent full. With some port types, you can configure the nonpriority receive queue to use both a tail-drop and a WRED-drop threshold by mapping a CoS value to the queue or to the queue and a threshold. The switch uses the tail-drop threshold for traffic carrying CoS values mapped only to the queue. The switch uses WRED-drop thresholds for traffic carrying CoS values mapped to the queue and a threshold. All LAN ports of the same type use the same drop-threshold configuration.

[gavin han]

Thanks Mark. On one of our switch (output shown below). I don't see "qos" (i.e. 1P4Q2T etc) for "sh int Gi1/1 capabilities" but I am able to enter "auto qos voip trust" command. does it mean this switch supports software qos but not hardware qos? will voice traffic have issues (in case of cpu over utilization) if this switch only supports software qos? switch also supports class-map, policy-map, service-policy commands.

sw-c4507R-EE#sh int Gi1/1 capabilities
GigabitEthernet1/1
Model: WS-X4640-CSFP-E-Gbic
Type: No Gbic
Speed: 100,1000
Duplex: full
Auto-MDIX: no
EEE: no
Trunk encap. type: 802.1Q
Trunk mode: on,off,desirable,nonegotiate
Channel: yes
Broadcast suppression: percentage(0-100), hw
Multicast suppression: percentage(0-100), hw
Flowcontrol: rx-(off,on,desired),tx-(off,on,desired)
VLAN Membership: static, dynamic
Fast Start: yes
CoS rewrite: yes
ToS rewrite: yes
Inline power: no
SPAN: source/destination
UDLD: yes
Link Debounce: no
Link Debounce Time: no
Port Security: yes
Dot1x: yes
Maximum MTU: 9198 bytes (Jumbo Frames)
Multiple Media Types: no
Diagnostic Monitoring: N/A
sw-c4507R-EE#sh int Gi1/1 capabilities | i qos
sw-c4507R-EE#conf t
Enter configuration commands, one per line. End with CNTL/Z.
sw-c4507R-E(config)#int Gi1/1
sw-c4507R-E(config-if)#au
sw-c4507R-E(config-if)#auto qo
sw-c4507R-E(config-if)#auto qos vo
sw-c4507R-E(config-if)#auto qos voip tr
sw-c4507R-E(config-if)#auto qos voip trust ?
<cr>

[Mark Malone]

not all platforms have it , it depends on the supervisor running and the line cards , nearly all 6500s I seen or Nexus switches would have it example below from sup720-3B , platforms and how they work qos vary from one to another depending on architecture , MLS is now gone from newer switches and its all auto qos nearly basically doing the same thing its still qos and still uses the TIS and DSCP values for marking  , but you will also see on newer ios-xe software there trusting DSCP markings by default now as well so in some cases theres not even a requirement to mark or trust at edge ports anymore unless trying to do something that wouldn't be standard  but some do anyway

so your switch does support qos just not mls but does support auto qos , once it does one or the other your fine , you will also see it has software qos that can be built manually through class-maps and policys , some auto qos platforms when enabled will build automatic mapping maps in the global config , you may see that when you enable auto qos

GigabitEthernet2/5
  Model:                 WS-X6548-GE-TX
  Type:                  10/100/1000BaseT
  Speed:                 10,100,1000,auto
  Duplex:                half,full
  Trunk encap. type:     802.1Q
  Trunk mode:            on,off,desirable,nonegotiate
  Channel:               yes
  Broadcast suppression: none
  Flowcontrol:           rx-(off,on,desired),tx-(off,on,desired)
  Membership:            static
  Fast Start:            yes
  QOS scheduling:        rx-(1q2t), tx-(1p2q2t)
  QOS queueing mode:     rx-(cos), tx-(cos)
  CoS rewrite:           yes
  ToS rewrite:           yes
  Inline power:          no
  Inline power policing: no
  SPAN:                  source/destination
  UDLD                   yes
  Link Debounce:         yes
  Link Debounce Time:    no
  Ports on ASIC:         1-24
  Remote switch uplink:  no
  Dot1x:                 yes
  Port-Security:         yes
xir-b100sds01#

[gavin han]

Thanks Very much Mark!

[Mark Malone]

If you don't mind Gavin if that's answered everything will you mark it as answered when other users search answered questions come up in search and theres a few useful links in that post from Joseph and myself it will save us having to repeat it all again for someone who has the same query which happens quite often

[gavin han]

sure Mark, I will do that. one more question, what's queue-set 1 and queue-set 2? what's difference between them and their importance?

swc3560#sh mls qos queue-set 1
Queueset: 1
Queue : 1 2 3 4
----------------------------------------------
buffers : 25 25 25 25
threshold1: 100 200 100 100
threshold2: 100 200 100 100
reserved : 50 50 50 50
maximum : 400 400 400 400
swc3560#sh mls qos queue-set 2
Queueset: 2
Queue : 1 2 3 4
----------------------------------------------
buffers : 25 25 25 25
threshold1: 100 200 100 100
threshold2: 100 200 100 100
reserved : 50 50 50 50
maximum : 400 400 400 400

[gavin han]

and which queue voice traffic use?

[Mark Malone]

Hi Gavin

you have 2 queue sets as you seen on platforms that run mls , the default queue-set can be 1 or 2 which will be applied to all interfaces and can be tweaked changing sizes depending on the platform , but you may want to have another ports not using same size queues so you have the option of setting queue set 2 to an interface and moving it off the default queue set , each queue gives you different sets of buffers , queue-set 1 is default on 2960s and queue-set 2 on 3560s when I look at mine , you can check using

sh mls qos interface queueing

GigabitEthernet1/0/30
Egress Priority Queue : enabled
Shaped queue weights (absolute) :  25 0 0 0
Shared queue weights  :  10 10 60 20
The port bandwidth limit : 100  (Operational Bandwidth:100.0)
The port is mapped to qset : 2

Queueset: 1
Queue     :       1       2       3       4
----------------------------------------------
buffers   :      10      10      26      54
threshold1:     138     138      36      20
threshold2:     138     138      77      50
reserved  :      92      92     100      67
maximum   :     138     400     318     400
Queueset: 2
Queue     :       1       2       3       4
----------------------------------------------
buffers   :      16       6      17      61
threshold1:     149     118      41      42
threshold2:     149     118      68      72
reserved  :     100     100     100     100
maximum   :     149     235     272     242

(config-if)#int g2/0/51
(config-if)#queue-set ?
  <1-2>  the qset to which this port is mapped

(config-if)#queue-set

queue 1 is the priority queue by default from what I remember but can be changed in global ---mls qos srr-queue input priority-queue ?

for voice you can also set the command priority-queue out under the interface , this will make sure priority queue voice is serviced first before others queues in srr

good doc explains it bit further

.........................................................

http://www.cisco.com/c/en/us/td/docs/switches/lan/catalyst2960/software/release/12-2_55_se/configuration/guide/scg_2960/swqos.html#pgfId-1157930

You can configure one ingress queue as the priority queue by using the mls qos srr-queue input priority-queue queue-id bandwidth weight global configuration command. The priority queue should be used for traffic (such as voice) that requires guaranteed delivery because this queue is guaranteed part of the bandwidth regardless of the load on the stack or internal ring.

SRR services the priority queue for its configured weight as specified by the bandwidth keyword in the mls qos srr-queue input priority-queue queue-id bandwidth weight global configuration command. Then, SRR shares the remaining bandwidth with both ingress queues and services them as specified by the weights configured with the mls qos srr-queue input bandwidth weight1 weight2 global configuration command.

You can combine the commands described in this section to prioritize traffic by placing packets with particular DSCPs or CoSs into certain queues, by allocating a large queue size or by servicing the queue more frequently, and by adjusting queue thresholds so that packets with lower priorities are dropped. For configuration information, see the “Configuring Ingress Queue Characteristics” section.

[gavin han]

Thanks Mark. what's difference between queue-set 1 and queue-set 2? do they refer to same hardware queue or different hardware queue? if default queue-set is 1 then is there a benefit to hardcode some ports for queue-set 2? how to check which queue is used for priority queue?

below command gives me option to configure only queue 1 or queue 2 as priority queue? does it mean queue 3 & 4 can't be configured as priority queue? 

sw-c3560(config)#mls qos srr-queue input priority-queue ?
<1-2> enter priority queue number [1-2]

I don't see option to define which queue to use for priority for egress. so we can't define egress priority queue?

sw-c3560(config)#mls qos srr-queue output ?
cos-map Configure cos-map for a queue id
dscp-map Configure dscp-map for a queue id

[Mark Malone · Accepted solution]

Thanks Mark. what's difference between queue-set 1 and queue-set 2? do they refer to same hardware queue or different hardware queue? if default queue-set is 1 then is there a benefit to hardcode some ports for queue-set 2? how to check which queue is used for priority queue?

Its just giving you a choice of 2 different ready made queue-sets, you see in my last post there different threshold and buffer values , depending on your setup queue 1 or 2 maybe your choice , most usually stick with the default and just tweak it if required , there may be an instance though where you need a totally different setup for some ports and that's where been able to deploy a second queue set would be beneficial to you , you may have some irregular device that doesn't fit the standard qos of all other ports so using default wont help , I have never had to use it always stuck with just default

below command gives me option to configure only queue 1 or queue 2 as priority queue? does it mean queue 3 & 4 can't be configured as priority queue? 

Yes from what I have read and understood only queue 1 or 2 can be priority queue and that's only on distribution switches like 3000 series , your layer 2 switches pure access like 2960s you probably cant change it , I cant change mine anyway all default queue 1 for priority, out of the box it will be queue 1 for priority unless you change it , you can check with extended ping as well ping and set the TOS decimal value to 184 which maps to DSCP 46 , if you ping constantly using that value it will think its voice traffic and you will see your priority queue fill up , that way and using wireshark are 2 good ways of confirming your packets are being marked right and put in right queue

#ping
Protocol [ip]:
Target IP address: 1.1.1.1
Repeat count [5]:
Datagram size [100]:
Timeout in seconds [2]:
Extended commands [n]: y
Source address or interface: vlan 1
Type of service [0]: 184
Set DF bit in IP header? [no]:
Validate reply data? [no]:
Data pattern [0xABCD]:
Loose, Strict, Record, Timestamp, Verbose[none]:

I don't see option to define which queue to use for priority for egress. so we can't define egress priority queue?

Yes that's all I have ever seen as well only by input