11th September 2017

Objective 2.2 – Configure Network I/O control (NIOC)

OK new week and a new set of revision posts.

Here is the rest of Objective 2, Objective 2.2 – Configure Network I/O control (NIOC).

As with the other posts I’ll continue linking these back to the VCP6.5 Certification Blueprint.

Happy revision




Objective 2.2 – Configure Network I/O control (NIOC)

Explain NIOC capabilities

About vSphere Network I/O Control Version 3

vSphere Network I/O Control version 3 introduces a mechanism to reserve bandwidth for system traffic based on the capacity of the physical adapters on a host. It enables fineȬgrained resource control at the VM network adapter level similar to the model that you use for allocating CPU and memory resources.

Version 3 of the Network I/O Control feature offers improved network resource reservation and allocation across the entire switch.

Models for Bandwidth Resource Reservation

Network I/O Control version 3 supports separate models for resource management of system traffic related to infrastructure services, such as vSphere Fault Tolerance, and of virtual machines.

The two traffic categories have different nature. System traffic is strictly associated with an ESXi host. The network traffic routes change when you migrate a virtual machine across the environment. To provide network resources to a virtual machine regardless of its host, in Network I/O Control you can configure resource allocation for virtual machines that is valid in the scope of the entire distributed switch.

Bandwidth Guarantee to Virtual Machines

Network I/O Control version 3 provisions bandwidth to the network adapters of virtual machines by using constructs of shares, reservation and limit. Based on these constructs, to receive sufficient bandwidth, virtualized workloads can rely on admission control in vSphere Distributed Switch, vSphere DRS and vSphere HA.

Configure NIOC shares/limits based on VM requirements

A network resource pool provides a reservation quota to virtual machines. The quota represents a portion of the bandwidth that is reserved for virtual machine system traffic on the physical adapters connected to the distributed switch. You can set aside bandwidth from the quota for the virtual machines that are associated with the pool. The reservation from the network adapters of powered on VMs that are associated with the pool must not exceed the quota of the pool.


  • Verify that vSphere Distributed Switch is version 6.0.0 and later.
  • Verify that Network I/O Control on the switch is version 3.
  • Verify that Network I/O Control is enabled.
  • Verify that the virtual machine system traffic has a configured bandwidth reservation.
  • In the vSphere Web Client, navigate to the distributed switch.
  • On the configure tab, expand Resource Allocation.
  • Click Network resource pools.
  • Click the Add icon.
  • Type a name and a description for the network resource pool.
  • Enter a value for Reservation quota, in Mbps, from the free bandwidth that is reserved for the virtual machine system traffic
    • The maximum quota that you can assign to the pool is determined according to the following formula:
    • max reservation quota = aggregated reservation for vm system traffic – quotas of the other resource pools
  • where:
    • aggregated reservation for vm system traffic = configured bandwidth reservation for the virtual machine system traffic on each pNIC * number of pNICs connected to the distributed switch quotas of the other pools = the sum of the reservation quotas of the other network resource pools
  • Click OK.

Explain the behaviour of a given NIOC setting

By using several configuration parameters Network I/O Control allocates bandwidth to traffic from basic vSphere system features.


Shares, from 1 to 100, reflect the relative priority of a system traffic type against the other system traffic types that are active on the same physical adapter. The amount of bandwidth available to a system traffic type is determined by its relative shares and by the amount of data that the other system features are transmitting. For example, you assign 100 shares to vSphere FT traffic and iSCSI traffic while each of the other network resource pools has 50 shares. A physical adapter is configured to send traffic for vSphere Fault Tolerance, iSCSI and management. At a certain moment, vSphere Fault Tolerance and iSCSI are the active traffic types on the physical adapter and they use up its capacity. Each traffic receives 50% of the available bandwidth. At another moment, all three traffic types saturate the adapter. In this case, vSphere FT traffic and iSCSI traffic obtain 40% of the adapter capacity, and vMotion 20%.


The minimum bandwidth, in Mbps, that must be guaranteed on a single physical adapter. The total

bandwidth reserved among all system traffic types cannot exceed 75 percent of the bandwidth that the physical network adapter with the lowest capacity can provide. Reserved bandwidth that is unused becomes available to other types of system traffic. However, Network I/O Control does not redistribute the capacity that system traffic does not use to virtual machine placement. For example, you configure a reservation of 2 Gbps for iSCSI. It is possible that the distributed switch never imposes this reservation on a physical adapter because iSCSI uses a single path. The unused bandwidth is not allocated to virtual machine system traffic so that Network I/O Control can safely meet a potential need for bandwidth for system traffic for example, in the case of a new iSCSI path where you must provide bandwidth to a new VMkernel adapter


The maximum bandwidth, in Mbps or Gbps, that a system traffic type can consume on a single physical adapter.

Determine Network I/O Control requirements

Example Bandwidth Reservation for System Traffic

The capacity of the physical adapters determines the bandwidth that you guarantee. According to this capacity, you can guarantee minimum bandwidth to a system feature for its optimal operation. For example, on a distributed switch that is connected to ESXi hosts with 10 GbE network adapters, you might configure reservation to guarantee 1 Gbps for management through vCenter Server, 1 Gbps for iSCSI storage, 1 Gbps for vSphere Fault Tolerance, 1 Gbps for vSphere vMotion trafficǰ and 0.5 Gbps for virtual machine trafficǯ Network I/O Control allocates the requested bandwidth on each physical network adapter. You can reserve no more than 75 percent of the bandwidth of a physical network adapter, that is, no more than 7.5 Gbps.

You might leave more capacity unreserved to let the host allocate bandwidth dynamically according to shares, limits, and use, and to reserve only bandwidth that is enough for the operation of a system feature.

NIOC Example

Differentiate Network I/O Control capabilities

See sections above.

Enable/Disable Network I/O Control

Enable network resource management on a vSphere Distributed Switch to guarantee minimum bandwidth to system traffic for vSphere features and to virtual machine traffic.

  • Prerequisites
  • Verify that the vSphere Distributed Switch version is 5.1.0 and later.
  • In the vSphere Web Client, navigate to the distributed switch.
  • From the Actions menu, select Edit Settings.
  • From the Network I/O Control drop-down menu, select Enable.
  • Click OK.

When enabled, the model that Network I/O Control uses to handle bandwidth allocation for system traffic and virtual machine traffic is based on the Network I/O Control version that is active on the distributed switch

 Monitor Network I/O Control

To monitor the NIOC setting, manage resource allocation under system traffic