what is class-default,service-policy queuing?

[getaway51]

Anyone knows how to explain this?Anyone can understand this settings in the ISP router? 

policy-map queuing
class audio
priority 3072
class video
bandwidth 3072
class biz-app
bandwidth 8192
class class-default
bandwidth 6144
policy-map b3
class class-default
shape average 20480000
service-policy queuing
policy-map lan
class audio
set ip precedence 5
class video34
set ip precedence 2
class biz-app
set ip precedence 0
class class-default
set ip precedence 1
policy-map wan
class audio
set ip dscp ef
class video
set ip dscp af41
class biz-app
set ip dscp default
class class-default
set ip dscp af21

[Kevin Groves]

The meaning behind "class class-default" and "policy-map queuing" is that: "class class-default" specifies whose bandwidth is to be configured or modified AND "policy-map queuing" is used to assign policy maps to interfaces.
This is all about QoS and because certain Cisco models and software do not automatically attach the class class map to a policy map, you can manually add the it to a policy map. On all other Cisco equipment, this class is, by default, included in a policy map.
What are you trying to accomplish and what Cisco model(s) and IOS version(s) are you using?

[getaway51]

Router is running 15.3

Basically i just wanted to knw why "ip precedence" and "dscp".

perhaps it is related to Cisco ip phone settings in the lan.   

[Kevin Groves]

I believe your answer should be in the following links. Read both of them, don't skim, and let me know!

• https://networklessons.com/quality-of-service/ip-precedence-dscp-values/
• https://en.wikipedia.org/wiki/Differentiated_services

[getaway51]

Hi, I understand IP Precedence and DSCP but not sure why they were set in such a way in router config.

Appreciate if you can explain how it works!

Below are the full config of class-map & policy map as well as QOS config.

1)Are the voice & video traffic coming from LAN tagged with dscp?

2)What traffic fall under "class class-default"? 

class class-default
shape average 2048000
service-policy queuing

3)What is the objective for config above particularly "service-policy queuing" & "class class-default" 

I only know it shape traffic to 2048000

4)Why need to set "service-policy output" & "service-policy input" for both LAN & WAN interface? I thought just match traffic from LAN which is "service-policy input qos-in" and set traffic out from WAN which is "service-policy output setbw" are sufficient? Is there any reason/objective to this standardization? I found it hard to understand. Any simple diagram/explanation?

interface GigabitEthernet0/1
description to LAN
service-policy input qos-in
service-policy output qos-out
!
interface Serial0/3
description to WAN 
bandwidth 2048
service-policy input in-qos
service-policy output setbw

----------------------------------------------------------

class-map match-all biz-app
match access-group name biz-qos
class-map match-all voice
match access-group name dscp-ef-voice
match packet length max 100
class-map match-all p-video
match ip precedence 2
class-map match-all p-voice
match ip precedence 5
class-map match-all p-biz
match ip precedence 0
class-map match-all dscp-34-video
match access-group name dscp-34-video
!
policy-map queuing
class p-voice
priority 256
class p-video
bandwidth 256
class p-biz
bandwidth 768
class class-default
bandwidth 768
policy-map setbw
class class-default
shape average 2048000
service-policy queuing
policy-map qos-in
class voice
set ip precedence 5
class dscp-34-video
set ip precedence 2
class biz-app
set ip precedence 0
class class-default
set ip precedence 1
policy-map qos-out
class p-voice
set ip dscp ef
class p-video
set ip dscp af41
class biz-app-IPPREC
set ip dscp default
class class-default
set ip dscp af21
policy-map in-qos
class p-voice
class p-video
class p-biz

interface GigabitEthernet0/1
description to LAN
service-policy input qos-in
service-policy output qos-out
!
interface Serial0/3
description to WAN
bandwidth 2048
service-policy input in-qos
service-policy output setbw

[paul driver]

Hello

---

@getaway51 wrote:

Hi, I understand IP Precedence and DSCP but not sure why they were set in such a way in router config.

Appreciate if you can explain how it works!

Below are the full config of class-map & policy map as well as QOS config.

1)Are the voice & video traffic coming from LAN tagged with dscp? -

No its being classified/marked with Ip precedence which isnt as granular to configure as dscp but it still has a relating dscp/AF value

example:
ip prec 0 = dcsp 0
ip prec 2 = dscp 16 = AF21-23 (dscp 18,20,22)
ip prec 5 = dscp 40  = EF (dscp 46)

2)What traffic fall under "class class-default"? 

class class-default
shape average 2048000
service-policy queuing

You are applying a shape Bw value to all of you egress wan traffic, and to do that you need to apply that to the class class-default within the parent policy

3)What is the objective for config above particularly "service-policy queuing" & "class class-default" 

I only know it shape traffic to 2048000

Hqos is being implemented here so you are nesting your child policy-map queuing  into a parent policy-map setbw and shaping your egress WAN traffic to 2mB

4)Why need to set "service-policy output" & "service-policy input" for both LAN & WAN interface? I thought just match traffic from LAN which is "service-policy input qos-in" and set traffic out from WAN which is "service-policy output setbw" are sufficient? Is there any reason/objective to this standardization? I found it hard to understand. Any simple diagram/explanation?

Yes this is a bit confusing, but I would have expected just to see a ingress service policy being to your lan interface and a egress service policy being to your WAN interface , However saying that I don't think that qos-out on your lan interface and in-qos on you wan interface are doing anything

[Kevin Groves]

This topic is very exciting and I appreciate your enthusiasm on QoS. Unfortunately there isn't any really good single documentation to understand the high-level nature of this. I will describe and answer this difficult topic to the best of my abilities below:

1.) Are the voice & video traffic coming from LAN tagged with dscp?
*************
**ANSWER: No, it just gets a dscp value number from Packet Classification which categorizes a packet within a specific class and assigns it a traffic descriptor to make it accessible for QoS network handling. This helps with congestion management/avoidance on the data path. So its tied to traffic policies that are created/applied to class(es) and not vlans. NOTE: Preference is given to higher dscp numbers over lower dscp numbers (example: Voice=46 is higher, then broadcast video followed by video conferencing, telepresence, multimedia streaming, and lastly call signaling is lower at 24.

2.) What traffic fall under "class class-default"?
class class-default
shape average 2048000
service-policy queuing
*************
**ANSWER: This is where all the traffic doesn't fall into the category will be the the default class. This is manually scripted by the network engineer with varying traffic descriptors as per network/company requirements.

3.) What is the objective for config above particularly "service-policy queuing" & "class class-default"?
*************
**ANSWER: I believe I answered your "Class class-default" in question two. For "shape average #######" is important so that an average can be manually defined if the network traffic needs are requiring strict adherence. If traffic strictness is not applicable to your network and you have additional bandwidth and can tolerate the occasional packet loss burst ability can be appended, however; this isn't in your config so I won't digress. For "service-policy queuing" is to attach a policy map to an input or output interface or virtual circuit allowing for weighted fair queueing.

4.) Why need to set "service-policy output" & "service-policy input" for both LAN & WAN interface? I thought just match traffic from LAN which is "service-policy input qos-in" and set traffic out from WAN which is "service-policy output setbw" are sufficient? Is there any reason/objective to this standardization? I found it hard to understand. Any simple diagram/explanation?
*************
**ANSWER: It is because voice traffic QoS works in both directions (talking and listening). Input and output must be defined here to have enough reserved bandwidth.

[paul driver]

Hello

---

@Kevin Groves wrote:

This topic is very exciting and I appreciate your enthusiasm on QoS. Unfortunately there isn't any really good single documentation to understand the high-level nature of this. I will describe and answer this difficult topic to the best of my abilities below:

1.) Are the voice & video traffic coming from LAN tagged with dscp?
*************
**ANSWER: No, it just gets a dscp value number from Packet Classification which categorizes a packet within a specific class and assigns it a traffic descriptor to make it accessible for QoS network handling. This helps with congestion management/avoidance on the data path. So its tied to traffic policies that are created/applied to class(es) and not vlans. NOTE: Preference is given to higher dscp numbers over lower dscp numbers (example: Voice=46 is higher, then broadcast video followed by video conferencing, telepresence, multimedia streaming, and lastly call signaling is lower at 24.

---

What are you basing you NO answer on?
The policy map applied ingress on the lan interface shows it being classified and marked with ip precedence

policy-map qos-in
class voice
set ip precedence 5
class dscp-34-video
set ip precedence 2
class biz-app
set ip precedence 0
class class-default
set ip precedence 1

---

2.) What traffic fall under "class class-default"?
class class-default
shape average 2048000
service-policy queuing
*************
**ANSWER: This is where all the traffic doesn't fall into the category will be the the default class. This is manually scripted by the network engineer with varying traffic descriptors as per network/company requirements.

---

They can be true however as the OP is using Hqos and they are shaping a CIR rate for all traffic to 2mb its the child policy within that will police the certain classes to there appropriate Bw allocation

---

3.) What is the objective for config above particularly "service-policy queuing" & "class class-default"?
*************
**ANSWER: I believe I answered your "Class class-default" in question two. For "shape average #######" is important so that an average can be manually defined if the network traffic needs are requiring strict adherence. If traffic strictness is not applicable to your network and you have additional bandwidth and can tolerate the occasional packet loss burst ability can be appended, however; this isn't in your config so I won't digress. For "service-policy queuing" is to attach a policy map to an input or output interface or virtual circuit allowing for weighted fair queueing.

---

Can you elaborate on this Kevin I am not sure i understand what you are saying here?

The service policy queuing is a child policy of the parent set-bw policy, as such the parent policy is shaping all egress traffic to 2mb and the child policy is allocating parts of this BW to the various defined class within it

---

4.) Why need to set "service-policy output" & "service-policy input" for both LAN & WAN interface? I thought just match traffic from LAN which is "service-policy input qos-in" and set traffic out from WAN which is "service-policy output setbw" are sufficient? Is there any reason/objective to this standardization? I found it hard to understand. Any simple diagram/explanation?
*************
**ANSWER: It is because voice traffic QoS works in both directions (talking and listening). Input and output must be defined here to have enough reserved bandwidth.

---

Regarding applying QOS for ingress traffic on the wan interface personally I think wouldn't be much of help as this has already cross the wire and taken up the BW .

In any case in this setup as I have stated before it looks like that qos-out on the lan interface and in-qos on the wan interface are not doing anything anyway