NBAR
NBAR stands for Network Based Application Recognition and can look beyond L3 and L4 information , all the way up to L7 .
Don’t forget also that NBAR relies on CEF enabled.
MQC supported markings
Here are also all supported markings after you have classified your traffic :
- IP Precendence (set ip precedence <<value>>)
- DSCP (set ip dscp <<value>>)
- QoS group (set ip precedence <<value>>)
- MPLS experimental bits (set mpls experimental <<value>>)
- Frame Relay DE bit (set fr-de)
- ATM CLP bit (set atm-clp)
Tools to classify traffic under a class-map
Here are all tools that we can use to classify the traffic under a class-map:
- ACL
- Existing markings ( CoS,IP Precedence,DSCP)
- QoS group
- Protocol (using NBAR)
- Traffic matching another class-map
- Mac-address (source or destination)
- Range of UDP ports
CoS Layer 2 >< ToS Layer 3
Just as a reminder , CoS marking (Layer 2) doesn’t “survive” to Layer 3 as the route processor will remark it.
It is why the most of the time a Cos to DSCP rewriting policy must be applied on the input direction of the interface.
AutoQoS Activation
Before enabling AutoQoS , take in mind the following pre-requisites :
- CEF must be enabled as AutoQoS relies on NBAR which is dependant of CEF.
- No Policy QoS can be attached to the interface
- The correct bandwidth statement must be set up on the interface
- An IP address must be configured on an interface if its speed is less than 768 Kbps
- The interface can’t be in a shutdown mode
You can the ask why IP Address is an mandatory element ?
It is simply because if your speed links is less than 768 Kbps , then AutoQoS will enable Multilink PPP (MLP)
Class-map
By default , a class-map will use the match-all criteria so it will tell that you must match all your conditions in your class-map before to classify the traffic .
If you want classify directly when at least one condition is met then use the criteria match-any.
Unclassified traffic will go in the default class.