Quality of service (QoS) has been a hot technology since its inception. QoS combines multiple technologies that help in building good traffic patterns on a computer network. To deploy a simple QoS policy that prioritizes business-critical applications on your network , follow these three steps:
- Classify network traffic
- Shape or police bandwidth
- Apply the QoS policy to a WAN interface
The example below explains QoS deployment on a network to support VoIP, which is now being commonly used on most networks. These VoIP packets should have proper treatment on the network or else users will experience bad call quality across network.
Classifying network traffic
Classification identifies the type of traffic that you want to prioritize on the network and then marks that traffic as a priority. Now, when the marked traffic travels through networking devices, those devices recognize the prioritized traffic and provide proper treatment.
To classify VoIP traffic on the network, you can use the example configuration mentioned below.
Let’s say all the VoIP traffic is coming from a particular subnet (192.168.1.0/24). This traffic passes through your network’s Cisco edge router, which connects the other sites. Now, we need to classify this VoIP traffic on the Cisco router. Below is a sample configuration that has to be done on the router.
Create the object group for VoIP network:
object-group network VoIP
192.168.1.0 255.255.255.0
Create the access list to match this VoIP traffic access group:
access-list 101 permit udp any Object-group VoIP
Create a class map to match the created access list:
Class-map match-all Traffic
Match any
Class-map match-all VoIP
Match access-group 101
Class-map match-all Video
Match ip dscp AF41
Shaping or policing bandwidth
Policing and shaping actually limit the bandwidth for a defined traffic type. If an interface is configured to police traffic for a given application type, then traffic will be remarked or dropped when that type of application tries to use more bandwidth than its specified limit.
Shaping also sets limits on bandwidth for classified data. If the bandwidth requirement is higher than the given limit, the router buffers the traffic and uses a queuing mechanism to prioritize the subsequent transmission of the buffered traffic.
Below are examples of traffic shaping:
policy-map class VoIP
bandwidth remaining percent 40
class Video
bandwidth remaining percent 50
class class-default
bandwidth remaining percent 10
!
!
policy-map Mission-Critical
class Traffic
shaping average 20000000
service-policy VoIP-Video
Applying the QoS policy to a WAN interface
Create a policy to attach to an interface that handles VoIP, so that when VoIP traffic exits the network, it is prioritized based on the policy on the router.
Interface GigabitEthernet0/0
Ip address X.X.X.X
Service-policy Mission-Critical
Traditional methods of analyzing QoS policy performance
The traditional methods of analyzing the performance of an applied QoS policy include polling the router through SNMP using third-party software and getting data from the QoS policy index MIB, class MIB, and others. Users can also log in to the router directly and execute the “show” command to analyze the policy details.
The methods above only give stats specific to policy and classes such as pre-policy, post-policy, drop, and queue metrics. However, those methods don’t say whether the intended traffic is really getting classified under the QoS policy. To confirm that traffic is being classified according to the policy, ManageEngine NetFlow Analyzer generates reports on CBQoS policies through SNMP. Click hereto learn more about this feature.
Advanced QoS hierarchy and drop monitoring using Cisco AVC
ManageEngine NetFlow Analyzer is capable of monitoring QoS Hierarchy and drop. The QoS policy and class details are actually exported in the NetFlow packets from routers, and you can see each flow policy and the class categorization details in NetFlow Analyzer reports. To configure the Cisco device for QoS Hierarchy and drop export, refer to this document.
Using NetFlow Analyzer with SNMP-based CBQoS reporting and Cisco AVC QoS reports, administrators can run their networks with zero delay and no downtime.
References
http://www.cisco.com/c/en/us/td/docs/ios/solutions_docs/avc/ios_xe3_9/avc_soln_guide_iosxe3_9/avc_config.html#wp1054638
http://www.cisco.com/en/US/prod/collateral/routers/ps9343/qa_c67-695977.html
http://www.cisco.com/en/US/prod/routers/avc_control.html#~overview
http://www.cisco.com/en/US/solutions/collateral/ns1015/ns483/ns780/at_a_glance_c45-649117.pdf
