What is the use cases of Using H-QOS over QOS

[Ibrahim Jamil]

Hello Guys What is the use cases of Using H-QOS over QOS Thanks

[Giuseppe Larosa]

Hello Ibrahim,

HQoS provides multiple levels of application and so it allows for more granular control

Example 1:

a CPE with a sub rate (not wire speed) parent shaper policy that invokes a child policy that implements a CBWFQ or LLQ scheduler for user defined class maps and for class class-default.

This is a typical use case of HQoS with two levels.

Example 2:

in a router acting as broadband access server or BNG you can define multiple levels of QoS that can apply to a range of outer Vlans (identifying a customer in a wholesale scenario) then matching on inner vlan values up to having a subscriber specific QoS policy.

The HQF Hierarchical QoS Framework has been introduced by Cisco with IOS release 12.4(20)T but it should apply to IOS XE and other network operating systems.

See the following slide from an event in forums

https://community.cisco.com/t5/networking-documents/hierarchical-queueing-framework-overview-and-changes-on-quality/ta-p/3123529?dtid=osscdc000283

Hope to help

Giuseppe

[Joseph W. Doherty]

The most common usage for H-QoS is, as already noted by Giuseppe, is a policy that contains shaping for some group which you want to define how that group's shaped traffic is to be QoS managed.

For example, if you have a "WAN" Ethernet connection (10 Mbps) but your provider is providing a 5 Mbps CIR, if you apply QoS at the physical interface it won't "trigger" until the interface actually congests, so you might have a "parent" policy to shape at 5 Mbps, and a "child" policy to determine what happens when there's congestion at 5 Mbps.

policy-map ParentSample
class class-default
shape average 5000000
service-policy ChildSample

policy-map ChildSample
class LLQ
priority percent 33
class class-default
fair-queue

The above is about the most common example of using H-QoS, but a parent policy could have multiple classes matching different groups of traffic all with the same shape value and using the same child policy or each with a different shape value and different child policy or some combination of the prior.

Some devices, I recall, support up to a 3 level H-QoS policy, but many (at least they used too) only support a 2 level H-QoS policy,