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10
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7
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Highlighted
Beginner

QoS related issues

Hello everyone!
Due to an emergency demand, I took over the position of a CCNP professional who dealt with direct questions from the Service Provider, and I need help with questions related to QoS.

 

Could you help me with that?

 

I have the following requirements requested by the client:

 

The circuit must follow the following QoS premise:
Queue 1 - 20% - Real Time
Queue 2 - 30% - Critical apps
Queue 3 - 40% - Non-critical apps
Queue 4 - 10% - Best Effort

 

1 - Queues 2, 3 and 4 can use resources from other queues (including queue 1), if they are without traffic. However, queue 1 cannot use resources from other queues.

2 - The available network must make the necessary appointments to adapt the network's QoS policies in both directions.

3 - The bandwidth reserved for each queue should flexibly meet the following criteria:

 

Queue 1 - EF; AF1
Queue 2 - AF21; AF22; AF23; AF31; FA32; FA33
Queue 3 - DSCP 00; (all remaining markings)
Queue 4 - AF11


Below is what was understood by me in relation to what was requested by the client:

 

class-map match-any Real_Time
description Data for Voice and Video Conference
match ip dscp ef
match ip dscp af41

 

class-map match-any Critical_Apps
description Critical Applications
match ip dscp af21
match ip dscp af22
match ip dscp af23
match ip dscp af31
match ip dscp af32
match ip dscp af33

 

class-map match-any Non_Critical_Apps
description Non-critical applications and standard DSCP
match ip dscp default
match ip dscp af12
match ip dscp af13
match ip dscp af42
match ip dscp af43

 

class-map match-any Best_Effort
description Best Effort
match ip dscp 11

 

policy-map QoS_Structure
class Real_Time
priority percent 20

 

class Critical_Apps
bandwidth percent 30
random-detect dscp-based

 

class Non_Critical_Apps
bandwidth percent 40
random-detect dscp-based
fair-queue

 

class Best_Effort
bandwidth percent 9
random-detect dscp-based
fair-queue


I would like to know if this configuration meets the client's requirements or if I am just mistaking it all.

Any help is always welcome!

 

Thank you!

1 ACCEPTED SOLUTION

Accepted Solutions
Highlighted

Again, for your Real_Time LLQ, the way LLQ normally works, if there's no actual queuing in that class, the class can use more than the specified bandwidth, up to the full link's worth. (The implicit policer only usually engages when traffic is queued in this class.) Basically, it will only, in such cases, use otherwise unused bandwidth. So, again, if you truly want to limit it to some amount of bandwidth, all the time, you need to police it.

E.g.
class Real_Time
priority percent 20
police average # !later IOS versions might also support a percentage allocation

The "class-default" doesn't get its own class-map because it's always there in the policy-map, whether explicitly defined or not. This built-in class is basically a none-of-the-above class. I.e. anything not matched in other classes goes through this class. As the sequence of class definitions in a policy-map can be important, as they are processed top to bottom (like an ACL), the class-default will always appear last. (Likewise, LLQ classes appear before other classes, but since you can define more than one of these, although there is only one physical LLQ [excluding later IOSs that support two - which you may want to consider for prioritization of VoIP over Video], the sequence of defining them is maintained, as configured, relative to each other.)

So:

class-map match-any Class_Default
description Non-critical Applications
match ip dscp default af12 af13
match ip dscp af42 af43


IPPrec is the earlier RFC for use of first 3 ToS byte bits. DSCP supercedes IPPrec but is somewhat backward compatible with IPPrec. For example, BE overlaps IPPrec zero, and IPPrec 6 and 7 are "left alone" by DSCP (so they can be treated as they were - for network management purposes). Traffic allocated to AF classes and EF, is generally done such that "more important" traffic aligns with, more-or-less, IPPrec 1..5. Knowing this, if you want to match, for example, CS# and the AF#x markings, IPPrec # will match them all. (IPPrec will also match the other "private" ToS values immediately one above the corresponding CS# and AF#x marking. E.g. IPPrec 1 matches DSCP values CS1, AF11, AF12, AF13 and 9, 11, 13, 15).

View solution in original post

7 REPLIES 7
Highlighted

Configuration looks good. Do you have any lab devices to work on this with a traffic generator.

Please do not hesitate to click the STAR button if you are satisfied with my answer.
Highlighted
VIP Expert

"However, queue 1 cannot use resources from other queues."

For that, you'll also need to add an explicit police statement to your Real_Time class.

Suggest for:

class-map match-any Non_Critical_Apps
description Non-critical applications and standard DSCP
match ip dscp default
match ip dscp af12
match ip dscp af13
match ip dscp af42
match ip dscp af43

class Non_Critical_Apps
bandwidth percent 40
random-detect dscp-based
fair-queue

Use, instead:

class class-default
bandwidth percent 40
fair-queue

Also (strongly) suggest, as seen in above class, not to use random-detect dscp-based (especially with FQ) in any class.

Also suggest possibly using FQ in Critical_Apps class.

BTW, generally DSCP BE (zero) is best effort class, not AF11.

Also BTW, your Best_Effort class only has 9% allocated. This, I believe, because implicit class-default requires at least 1%. If you do as suggested, above, you should be able to allocate the requested 10%.

Further, also BTW, believe you can match up to 4 DSCP markings per match statement. So, if you want to "condense" your configuration, you might write a class-map like:

class-map match-any Critical_Apps
description Critical Applications
match ip dscp af21 af22 af23
match ip dscp af31 af32 af33

Lastly, what about IPPrec 6 and 7, 5 (excluding EF), CS1..4, AF12 and AF13, AF42 and AF43; client wants all these treated BE?
Highlighted

Hi Joseph!

 

Thank you for your help, and for sharing your knowledge with me!

I modified the structure of the settings according to its orientation, from what I could understand, I think it should be as below, right?

 

class-map match-any Real_Time
description Voice and Video Conference
match ip dscp af41 ef

 

class-map match-any Critical_Apps
description Critical Applications
match ip dscp af21 af22 af23
match ip dscp af31 af32 af33

class-map match-any Class_Default
description Non-critical Applications
match ip dscp default af12 af13
match ip dscp af42 af43

class-map match-any Bulk_Data
description Background Noninteractive Traffic Flows
match ip dscp af11

policy-map QoS_Structure

class Real_Time
priority percent 20

 

class Critical_Apps
bandwidth percent 30
fair-queue

 

class Class_Default
bandwidth percent 40
fair-queue

 

class Bulk_Data
bandwidth percent 10
fair-queue


Lastly, what about IPPrec 6 and 7, 5 (excluding EF), CS1..4, AF12 and AF13, AF42 and AF43; client wants all these treated BE?
Everyone's tags (0)

 

 

I am still studying IP Precedence and I confess that I still don't have enough knowledge to apply it correctly in these configurations.

 

For the information provided by the customer, it is necessary that Queue 2 (Critical_Apps), Queue 3 (Class_Default), and Queue 4 (Bulk_Data) can use resources from other queues, including Queue 1 (Real_Time), if these queues are without traffic . However, Queue 1 (Real_Time) will not be able to use the resources belonging to the other queues, even if they are without traffic.

 

 

 

 

Again, thank you for all your help!

Highlighted

Again, for your Real_Time LLQ, the way LLQ normally works, if there's no actual queuing in that class, the class can use more than the specified bandwidth, up to the full link's worth. (The implicit policer only usually engages when traffic is queued in this class.) Basically, it will only, in such cases, use otherwise unused bandwidth. So, again, if you truly want to limit it to some amount of bandwidth, all the time, you need to police it.

E.g.
class Real_Time
priority percent 20
police average # !later IOS versions might also support a percentage allocation

The "class-default" doesn't get its own class-map because it's always there in the policy-map, whether explicitly defined or not. This built-in class is basically a none-of-the-above class. I.e. anything not matched in other classes goes through this class. As the sequence of class definitions in a policy-map can be important, as they are processed top to bottom (like an ACL), the class-default will always appear last. (Likewise, LLQ classes appear before other classes, but since you can define more than one of these, although there is only one physical LLQ [excluding later IOSs that support two - which you may want to consider for prioritization of VoIP over Video], the sequence of defining them is maintained, as configured, relative to each other.)

So:

class-map match-any Class_Default
description Non-critical Applications
match ip dscp default af12 af13
match ip dscp af42 af43


IPPrec is the earlier RFC for use of first 3 ToS byte bits. DSCP supercedes IPPrec but is somewhat backward compatible with IPPrec. For example, BE overlaps IPPrec zero, and IPPrec 6 and 7 are "left alone" by DSCP (so they can be treated as they were - for network management purposes). Traffic allocated to AF classes and EF, is generally done such that "more important" traffic aligns with, more-or-less, IPPrec 1..5. Knowing this, if you want to match, for example, CS# and the AF#x markings, IPPrec # will match them all. (IPPrec will also match the other "private" ToS values immediately one above the corresponding CS# and AF#x marking. E.g. IPPrec 1 matches DSCP values CS1, AF11, AF12, AF13 and 9, 11, 13, 15).

View solution in original post

Highlighted

I am having trouble understanding you accurately, I believe it is due to my level of English.

Sorry about that.

Latest changes:

class-map match-any Real_Time
description Voice and Video Conference
match ip dscp af41 ef

class-map match-any Critical_Apps
description Critical Applications
match ip dscp af21 af22 af23
match ip dscp af31 af32 af33

class-map match-any Class_Default
description Non-critical Applications
match ip dscp default

class-map match-any Bulk_Data
description Background Noninteractive Traffic Flows
match ip dscp af11



policy-map QoS_Structure

class Real_Time
priority percent 20
police rate percent 20

class Critical_Apps
bandwidth percent 30
fair-queue

class Class_Default
bandwidth percent 40
fair-queue

class Bulk_Data
bandwidth percent 10  (I still can't reach 10% of the band, something must still be wrong)
fair-queue
Test.JPG


About the class below:
Class_Default
description Non-critical Applications
match ip dscp default
Can I leave it this way, or do I need to remove it?


I am taking a lot of your time, if it is no longer feasible for you to answer I will understand perfectly.

Thanks!

Highlighted

"I am having trouble understanding you accurately, I believe it is due to my level of English.

Sorry about that."

No need to apologize. I'm sure your understanding of English is better than mine of your native language. ;)

Okay, one issue, you've defined a class-map and policy-map class for "Class_Default". Don't define that class-map and replace its policy-map class with one defined "class-default". The latter is a built-in class. It's always present, although it won't appear in the config unless you define it. If you define it explicitly, you can define parameters for it. (I believe this "built-in" class is what's using the missing 1%.)
Highlighted
Beginner

Hello Vishnu Vardhan

 

Yes, I have EVE-NG and PNETlab simulators. I have been following these traffic with Sniffer and checking the matches directly in the Appliances.

 

Thank you for your help!

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