The different QoS capabilities of the VMware vSwitch’s

In a recent discussion (podcast with Scott Lowe) we discussed that ability of the network to effectively apply QoS to server frames when all the servers are located in a single VLAN is limited. This led me to consider the different types of QoS that can be managed in the VMware vSwitch.

Three types

There are three types of software switch in the VMware platform – vSwitch, vDS and Nexus 1000. Both the vDS and Nexus 1000 are licensed upgrades to the base system meaning that they cost more but hopefully there are features that justify the extra cost.

  • vSwitch – The standard software connectivity in vSphere. More like a fancy network adapter than an effective network element
  • vDS – The virtual distributed switch (vDS is the TLA) has more functions that just enhanced QoS
  • Nexus 1000 – a Cisco software enhancement that attaches to the VMware kernel to provide a number of the enhanced functions, and centralised configuration that uses the IOS CLI and will be familiar to Cisco skilled people everywhere.

The QoS

There are three key elements of the QoS strategy

  • classification
  • marking
  • policing and shaping
QOS functions of VMware networking software
QoS capability vSwitch vDS Nexus 1000
Classification No No Yes
Marking No No Yes
Policing Yes (Outbound only) Yes (Outbound and Inbound, simple PQ mode) Yes
Shaping No No Yes

It should be noted that the Nexus 1000 vSwitch software also provides Netflow, SPAN/ERSPAN and CDP for better operation and troubleshooting.

The EtherealMind View

The current QoS functions of VMware aren’t great compared to the existing solutions in Ethernet switches. However, the DCB networking standards will supply a lot more functionality to allow per flow QoS signalling and control and have more granular policies in the near future.

Additionally, there are more standards in development such 802.1Qbg and 802.1Qbh that offers much improved functionality for a wide range of networking features between the network and VMware that will most likely make software networking either significantly different or even obsolete. Therefore, I currently take the view that future product developments will improve VMware networking and customers should limit the use of vDS and Nexus for QoS unless absolutely necessary, as these functions will eventually become a standard feature of the Ethernet Network Edge.

Comments are welcome. Happy to discuss if I’ve misinterpreted information anywhere!

About Greg Ferro

Greg Ferro is a Network Engineer/Architect, mostly focussed on Data Centre, Security Infrastructure, and recently Virtualization. He has over 20 years in IT, in wide range of employers working as a freelance consultant including Finance, Service Providers and Online Companies. He is CCIE#6920 and has a few ideas about the world, but not enough to really count.

He is a host on the Packet Pushers Podcast, blogger at and on Twitter @etherealmind and Google Plus

You can contact Greg via the site contact page.

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