This section shows examples of how you can use access lists to configure quality of service (QoS), classifying data packets and prioritizing the transmission properties for different classes. Note that QoS is synonymous with class of service (CoS).
Forwarding and QoS Example
This example shows how to configure class of service (CoS) to classify data packets and control how traffic flows out of and in to the interfaces on a vEdge router and on the interface queues. To configure a QoS policy:
- Map each forwarding class to an output queue.
- Configure the QoS scheduler for each forwarding class.
- Group the QoS schedulers into a QoS map.
- Define an access list to specify match conditions for packet transmission.
- Apply the access list to a specific interface.
- Apply the queue map and the rewrite rule to the egress interface.
The sections below show examples of each of these steps.
Map Forwarding Class to Output Queue
This example shows a data policy that classifies incoming traffic by mapping each forwarding class to an output queue. Here, traffic classified as "be" (Best Effort) is mapped to queue 2, traffic classified as "af1" (Assured Forwarding) is mapped to queue 3, and so on.
policy class-map class be queue 2 class af1 queue 3 class af2 queue 4 class af3 queue 5 ! !
Configure QoS Scheduler for Each Forwarding Class
This example illustrates how to configure the QoS scheduler for each queue to define the importance of data packets. Depending on the priority of the traffic, you assign the bandwidth, buffer level, and random early detection (RED) drop profile associated with the queue. Here, "af3" traffic has higher priority over other traffic classes and so is configured to have 40% bandwidth and 40% buffer. Traffic in class "af2" has 30% bandwidth and 30% buffer; traffic in class "af1" class has 20% bandwidth and 20% buffer and traffic in class "be" has 10% bandwidth and 10% buffer size reflecting the respective priority of the traffic on the network. All traffic classes are configured with a drop profile of RED, meaning that instead of waiting for the queue to be full, packets are dropped randomly based on the thresholds defined.
qos-scheduler af1 class af1 bandwidth-percent 20 buffer-percent 20 drops red-drop ! qos-scheduler af2 class af2 bandwidth-percent 30 buffer-percent 30 drops red-drop ! qos-scheduler af3 class af3 bandwidth-percent 40 buffer-percent 40 drops red-drop ! qos-scheduler be class be bandwidth-percent 10 buffer-percent 10 drops red-drop !
Group QoS Schedulers into a QoS Map
This example illustrates the grouping of "qos scheduler af1," "qos scheduler af2," and "qos scheduler be" into a single QoS map called "test."
qos-map test qos-scheduler af1 qos-scheduler af2 qos-scheduler be ! !
Classify Data Packets into Appropriate Class
This example shows how to classify data packets into appropriate forwarding classes based on match conditions. Here "access-list acl1" classifies data packets originating from the host at source address 10.10.10.1 and going to the destination host at 126.96.36.199 into the "be" class. Data packets with a DSCP value of 10 in the IP header field are classified in the "af1" class, TCP packets are classified in the "af3" class, and packets going to destination port 23, which carries Telnet mail traffic, are classified in the "af2" class. All other traffic is dropped.
policy access-list acl1 sequence 1 match source-ip 10.10.10.1/32 destination-ip 188.8.131.52/32 ! action accept class be ! ! sequence 2 match dscp 10 ! action accept class af1 ! ! sequence 3 match protocol 6 ! action accept class af3 ! ! sequence 4 match destination-port 23 ! action accept class af2 ! ! default-action drop ! !
Apply Access List to Specific Interface
This example illustrates how to apply the access list defined above on the input of a service interface. Here "access-list acl1" is applied on the input of interface ge0/4 in VPN 1.
vpn 1 interface ge0/4 ip address 10.20.24.15/24 no shutdown access-list acl1 in ! !
Configure Rewrite Rule
This example shows how to configure the rewrite rule to overwrite the DSCP field of the outer IP header. Here the rewrite rule "transport" overwrites the DSCP value for forwarding classes based on the drop profile. Since all classes are configured with RED drop, they can have one of two profiles: high drop or low drop. The rewrite rule is applied only on the egress interface, so on the way out, packets classified as "af1" and a Packet Loss Priority (PLP) level of low are marked with a DSCP value of 3 in the IP header field, while "af1" packets with a PLP level of high are marked with 4. Similarly, "af2" packets with a PLP level of low are marked with a DSCP value of 5, while "af2" packets with a PLP level of high are marked with 6, and so on.
policy rewrite-rule transport class af1 low dscp 3 class af1 high dscp 4 class af2 low dscp 5 class af2 high dscp 6 class af3 low dscp 7 class af3 high dscp 8 class be low dscp 1 class be high dscp 2 ! !
Apply the Queue Map and Rewrite Rule on an Interface
This example applies the queue map "test" and the rewrite rule "transport" to the egress interface ge0/0 in VPN 0. Queue maps and rewrite rules are applied only on outgoing traffic.
vpn 0 interface ge0/0 ip address 10.1.15.15/24 tunnel-interface preference 10 weight 10 color lte allow-service dhcp allow-service dns allow-service icmp no allow-service sshd no allow-service ntp no allow-service stun ! no shutdown qos-map test rewrite-rule transport ! !
Police Data Packets
This example illustrates how to configure a policer to rate limit traffic received on an interface. After you configure the policer, include it in an access list. Here "policer-p1" is configured to have a maximum traffic rate of 1,000,000 bits per second and a maximum burst-size limit of 15000 bytes. Traffic exceeding these rate limits is dropped. The policer is then included in the access list "acl1," which is configured to accept all TCP or UDP traffic originating from the host at source 184.108.40.206 and going to the destination host at 10.1.1.0 on port 20 or 220.127.116.11 on port 30. You can use "access-list acl1" on the input or output of the interface to do flow-based policing.
policy policer p1 rate 1000000 burst 15000 exceed drop ! access-list acl1 sequence 1 match source-ip 18.104.22.168/16 destination-ip 10.1.1.0/24 22.214.171.124/24 destination-port 20 30 protocol 6 17 23 ! action accept policer p1 ! ! default-action drop ! ! vpn 1 interface ge0/4 ip address 10.20.24.15/24 no shutdown access-list acl1 in ! !
A policer can also be directly applied on an inbound or an outbound interface. You can do so if you want to police all traffic ingressing or egressing this interface.
policy policer p1 rate 1000000 burst 15000 exceed drop ! ! vpn 1 interface ge0/4 ip address 10.20.24.15/24 no shutdown policer p1 in ! ! vpn 2 interface ge0/0 ip address 10.1.15.15/24 no shutdown policer p1 out ! !