V-216621

Discussion

DoS is a condition when a resource is not available for legitimate users. Packet flooding distributed denial-of-service (DDoS) attacks are referred to as volumetric attacks and have the objective of overloading a network or circuit to deny or seriously degrade performance, which denies access to the services that normally traverse the network or circuit. Volumetric attacks have become relatively easy to launch using readily available tools such as Low Orbit Ion Cannon or botnets. Measures to mitigate the effects of a successful volumetric attack must be taken to ensure that sufficient capacity is available for mission-critical traffic. Managing capacity may include, for example, establishing selected network usage priorities or quotas and enforcing them using rate limiting, Quality of Service (QoS), or other resource reservation control methods. These measures may also mitigate the effects of sudden decreases in network capacity that are the result of accidental or intentional physical damage to telecommunications facilities (such as cable cuts or weather-related outages).

Check Content

Review the router configuration to determine if it is configured to enforce a QoS policy to limit the effects of packet flooding DoS attacks.

Step 1: Verify that a class map has been configured for the Scavenger class as shown in the example below.

class-map match-all SCAVENGER
 match ip dscp cs1

Step 2: Verify that the policy map includes the SCAVENGER class with low priority as shown in the following example below. 

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 SCAVENGER
    bandwidth percent 5
 class class-default
    bandwidth percent 10

Note: Traffic out of profile must be marked at the customer access layer or CE egress edge.

If the router is not configured to enforce a QoS policy to limit the effects of packet flooding DoS attacks, this is a finding.