V-216715

Discussion

Different applications have unique requirements and toleration levels for delay, jitter, bandwidth, packet loss, and availability. To manage the multitude of applications and services, a network requires a QoS framework to differentiate traffic and provide a method to manage network congestion. The Differentiated Services Model (DiffServ) is based on per-hop behavior by categorizing traffic into different classes and enabling each node to enforce a forwarding treatment to each packet as dictated by a policy. Packet markings such as IP Precedence and its successor, Differentiated Services Code Points (DSCP), were defined along with specific per-hop behaviors for key traffic types to enable a scalable QoS solution. DiffServ QoS categorizes network traffic, prioritizes it according to its relative importance, and provides priority treatment based on the classification. It is imperative that end-to-end QoS is implemented within the IP core network to provide preferred treatment for mission-critical applications.

Check Content

Review the router configuration and verify that a QoS policy has been configured to provide preferred treatment for mission-critical applications.

Step 1: Verify that the class-maps are configured to match on DSCP values as shown in the configuration example below:

class-map match-all PREFERRED_DATA
 match ip dscp af33
class-map match-all CONTROL_PLANE
 match ip dscp cs6
class-map match-all VIDEO
 match ip dscp af41
class-map match-all VOICE
 match ip dscp ef
class-map match-all C2_VOICE
 match ip dscp 47

Step 2: Verify that the policy map reserves the bandwidth for each traffic type as shown in the following example:

policy-map QOS_POLICY
 class CONTROL_PLANE
    priority percent 10
 class C2_VOICE
    priority percent 10
 class VOICE
    priority percent 15
 class VIDEO
    bandwidth percent 25
 class PREFERRED_DATA
    bandwidth percent 25
 class class-default
    bandwidth percent 15

Step 3: Verify that an output service policy is bound to all interfaces as shown in the configuration example below:

interface GigabitEthernet1/1
 ip address 10.1.15.5 255.255.255.252
 service-policy output QOS_POLICY
!
interface GigabitEthernet1/2
 ip address 10.1.15.8 255.255.255.252
 service-policy output QOS_POLICY

If the router is not configured to implement a QoS policy in accordance with the QoS DODIN Technical Profile, this is a finding.