Windows 2012 QoS

Quality of Service QoS:

QoS is one of the Advance Network feature in Windows Server 2012;what we are getting with QoS?

Bits per Second–Based or Weight-Based you will choose between implementing QoS by using bps-based or weight-based rules.

The bps-based rules can be quite specific, guaranteeing a very certain amount of bandwidth, which can be useful for some applications.

bps rules can be considered inflexible, especially if workloads are mobile between hosts.

Weight-based rules are extremely flexible and are usually going to be the correct choice; a weight-based rule is based on a share of bandwidth, with no consideration of the actual speed

Minimum Bandwidth: can guarantee a minimum share of the host’s bandwidth to a virtual NIC or a protocol.

Maximum Bandwidth: can limit the bandwidth consumption of a virtual NIC or protocol with this type of rule.

 These are the three approaches to applying QoS:

1) Hyper-V Virtual Switch If the traffic in question is passing through a virtual switch, you can create QoS rules that are based on virtual NICs rather than on protocols. With this type of rule, you are creating minimum or maximum rules for connections.

2) Server Networking This category includes any networking that does not include a virtual NIC and a Hyper-V virtual switch, such as a physical NIC that is used by the management OS, or the NICs used by a file server. The rules are based on protocols rather than on virtual NICs, which can give you great granularity of control. There are two ways to apply QoS when you have physical networking.

If you have NICs and switches that support Data Center Bridging (DCB), you can create rules for protocols or IP ports that will be applied by the hardware.

1. If you have NICs and switches that support Data Center Bridging (DCB), you can create rules for protocols or IP ports that will be applied by the hardware.

2. If you do not have end-to-end DCB-capable networking, you can create rules for protocols or IP ports that will be applied by the OS packet scheduler.


Data Center Bridging (DCB) is an extension to Ethernet that allows the classification and prioritization of traffic for lossless transmission. DCB allows you to classify protocols and prioritize them. The QoS rules are applied at the hardware level, therefore not increasing the load on the OS packet scheduler.

You must have end-to-end support, including NICs and networking appliances, to use DCB.

3) Networking That Bypasses the Operating System: Remote Direct Memory Access (RDMA).

RDMA enables Server Message Block (SMB) Multichannel (NIC support RSS) to use 100 percent of bandwidth in very high bandwidth networks without fully utilizing the processor of the server.

This feature, called SMB Direct, does this by offloading the SMB transfer so that it effectively becomes invisible to the operating system.


Summarize the three QoS approaches

Applying QoS to Virtual NICs

When traffic is passing through a virtual switch, and therefore from a virtual NIC, we create QoS rules that are based on virtual NICs.

This is the simplest of the three ways to configure QoS: you have a virtual NIC, and you give it a share of bandwidth.

Applying QoS to Protocols with the OS Packet Scheduler

Classify protocols and use the OS packet scheduler to apply QoS rules for traffic that does not go through a virtual switch in the operating system.

Applied scenarios:

1- We want to apply QoS to traffic for physical NICs in which we do not have end-to-end support for DCB.

2-We want to apply QoS inside the guest operating system of a virtual machine, assuming that it is running Windows Server 2012.

Applying QoS to Protocols Using DCB

It is the preferred option if you have DCB-capable NICs and network appliances; this option is to let the hardware do the work.

DCB uses priorities to apply QoS policies.

You will use the following process to classify protocols and create traffic classes that prioritize the traffic:

  1. Install the DCB feature on the server by using Server Manager.
  2. Create the required QoS policies by classifying protocols.
  3. Create a traffic class that matches each created QoS policy.
  4. You should enable PFC if you are using RoCE networking and the NIC(s) support PFC.
  5. Enable DCB settings to be applied to the NICs.
  6. Specify the NICs that will use DCB.

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