Configuring Jumbo Frames with PowerShell in Windows Server 2012

Posted on June 11, 2012 by workinghardinit

During lab and test time with Windows Server 2012 Hyper-V some experimenting with PowerShell is needed to try and automate actions and settings. One of the thing we have been playing around with was how to enable and configure jumbo frames.

Many advanced features like Large Send Offload have commandlets of their own (Enable-NetAdapterLso etc.), but not all them and jumbo frames is one of the latter. For those advanced features you can use the NetAdapterAdvancedProperty commandlets (Network Adapter Cmdlets in Windows PowerShell). You can than set/enable those features via the registry keywords & values. Let’s say we want to enable jumbo frames on a virtual adapter named “ISCSI” in a VM.

To know what values to use you can run:

Get-NetAdapterAdvancedProperty -Name ISCSI

As you can see Jumbo Packet has a RegistryValue of 1514 and a DisplayValue of “Disabled”. You can also see that the RegistryKeyword to use to enable and configure jumbo frames is “*JumboPacket”. So to enable jumbo frames you run the following command:

Set-NetAdapterAdvancedProperty -Name “ISCSI” -RegistryKeyword “*JumboPacket” -Registryvalue 9014

The RegistryValue is set to 9014 and the DisplayValue is set to “9014 Bytes”, i.e. it’s enabled.

If you type in an disallowed value it will list the accepted values. Please note also that these can differ from NIC to NIC depending on what is supported. Some will only show 1514, 4088, some will show 1514, 4088, 9014.

Now to disable jumbo frames you just need to reset the RegistryValue back to 1514

Set-NetAdapterAdvancedProperty -Name “ISCSI” -RegistryKeyword “*JumboPacket” -Registryvalue 1514

The result of this command can be seen in the picture below. DisplayName Jumbo Packet has a DisplayValue of “Disabled” again.

Let’s say you want to enable jumbo frames on all network adapters in a host you can run this:

Get-NetAdapterAdvancedProperty -DisplayName “Jumbo Packet” | Set-NetAdapterAdvancedProperty –RegistryValue “9014”

Or run

Set-NetAdapterAdvancedProperty -Name * -RegistryKeyword “*JumboPacket” -Registryvalue 9014

I didn’t notice much difference in speed testing this with measure-command.

If you mess things up to much and you want to return all DisplayName settings to a well known status, i.e. the defaults you can run:

Reset-NetAdapterAdvancedProperty –Name SCSCI –DisplayName *

If you’ve just messed around with the jumbo frame settings run

Reset-NetAdapterAdvancedProperty -Name ISCSI –DisplayName “Jumbo Packet”

Or you can do the same for all network adapters:

Reset-NetAdapterAdvancedProperty –Name * –DisplayName “Jumbo Packet”

There you go, you’re well on your way doing the more advanced configurations of your network setup. Enjoy!

Windows Server 2012 Supports Data Center Bridging (DCB)

Posted on June 4, 2012 by workinghardinit

Data Center Bridging (DCB) is a collection of standards-based end-to-end networking technologies that allow Ethernet to act as the unified fabric for multiple types of traffic in the data center. You cannot put a bunch of traffic types / protocols on the same physical pipes if you have no way of guaranteeing that they will each get what they need when they need it based on priority and impact. Even with ludicrous over provisioning you could still run into issues and even if that’s not the case that’s a very expensive option. When you think about iSCSI, Remote Direct Memory Access (RDMA) and Fibre Channel over Ethernet (FCoE) you can see where the benefits are to be found. We just can keep adding network after network infrastructure for all these applications on a large scale.

Integrates with the standard Ethernet networks
Prevents congestion in NIC & network by reserving bandwidth for particular traffic types giving better performance for all
Windows 2012 provides support & control for DCB and allows to tags packets by traffic type
Provides lossless transport for mission critical workloads

You can see why this can be handy in a virtualized world evolving in to * cloud infrastructure. By enabling multiple traffic types to use an Ethernet fabric you can simplify & reduce the network infrastructure (hardware & cabling). In some environments this is a big deal. Imagine that a cloud provider does storage traffic over Ethernet on the same hardware infrastructure as the rest of the Ethernet traffic. You can get rid of the isolated storage-specific switches and HBAs reducing complexity, and operational costs. Potentially even equipment costs, I say potentially because I’ve seen the cost of some unified fabric switches and think your mileage may vary depending on the scale and nature of your operations.

Requirements for Data Center Bridging

DCB is based on 4 specifications by the DCB Task Group

Enhanced Transmission Selection (IEEE 802.1Qaz)
Priority Flow Control (IEEE 802.1Qbb)
Datacenter Bridging Exchange protocol
Congestion Notification (IEEE 802.1Qau)

3. & 4. are not strictly required but optional (and beneficial) if I understand things correctly. If you want to dive a little deeper have a look here at the DCB Capability Exchange Protocol Specification and have a chat with your network people on what you want to achieve.

You also need support for DCB in the switches and in the network adaptors.

Finally don’t forget to run Windows Server 2012 as the operating systems Winking smile . You can find some more information on TechNet Data Center Bridging (DCB) Overview but it is incomplete. More information is coming!

Understanding what it is and does

So, in the same metaphor of a traffic situation like we used with Data Center TCP we can illustrate the situation & solution with traffic lanes for emergency services and the like. Instead of having your mission critical traffic stuck in grid lock like the fire department trucks below

You could assign an reserved lane, QOS, guaranteed minimal bandwidth, for that mission critical service. Whilst you at it you might do the same for some less critical services that none the less provide a big benefit to the entire situation as well.

Windows Server 2012 Supports Data Center TCP (DCTCP)

Posted on May 26, 2012 by workinghardinit

In the grand effort to make Windows Server 2012 scale above and beyond the call of duty Microsoft has been addressing (potential) bottle necks all over the stack. CPU, NUMA, Memory, storage and networking.

Data Center TCP (DCTCP) is one of the many improvements by which Microsoft aims to deliver a lot better network throughput with affordable switches. Switches that can mange large amounts of network traffic tend to have large buffers and those push up the prices a lot. The idea here is that a large buffer creates the ability to deal with burst and prevents congestions. Call it over provisioning if you want. While this helps it is far from ideal. Let’s say it a blunt instrument.

To mitigate this issue Windows Server 2012 is now capable dealing with network congestion in a more intelligent way. It does so by reacting to the degree & not merely the presence of congestion using DCTCP. The goals are:

Achieve low latency, high burst tolerance, and high throughput, with small buffer switches (read cheaper).
Requires Explicit Congestion Notification (ECN, RFC 3168) capable switches. This should be no showstopper you’d think as it’s probably pretty common on most data center / rack switches but that doesn’t seem to be the case for the real cheap ones where this would shine …
Algorithm enables when it makes sense to do so (low round trip times, i.e. it will be used inside the data center where it makes sense, not over a world wide WAN or internet).

To see if it is applied run Get-NetTcpConnection:

As you can see this is applied here on a DELL PC8024F switch for the CSV and LM networks. The internet connected NIC (connection of the RDP session) shows:

Yup, it’s East-West traffic only, not North-South where it makes no sense.

When I was prepping a slide deck for a presentation on what this is, does and means I compared it to the green wave traffic light control. The space between consecutive traffic lights is the buffer and the red light are stops the traffic has to deal with due congestion. This leaves room for a lot of improvement and the way to achieve this is traffic control that intelligently manages the incoming flow so that at every hop there is a green light and the buffer isn’t saturated.

Windows Server 2012 in combination with Explicit Congestion Notification (ECN) provides the intelligent traffic control to realize the green wave.

The result is very smooth low latency traffic with high burst tolerance and high throughput with cheaper small buffer switches. To see the difference look at the picture below (from Microsoft BUILD)of what this achieves. Pretty impressive. Here’s a paper by Microsoft Research on the subject

NIC Teaming in Windows 8 & Hyper-V

Posted on April 10, 2012 by workinghardinit

One of the many new features in Windows 8 is native NIC Teaming or Load Balancing and Fail Over (LBFO). This is, amongst many others, a most welcome and long awaited improvement. Now that Microsoft has published a great whitepaper (see the link at the end) on this it’s time to publish this post that has been simmering in my drafts for too long. Most of us dealing with NIC teaming in Windows have a lot of stories to tell about incompatible modes depending on the type of teaming, vendors and what other advanced networking features you use. Combined with the fact that this is a moving target due to a constant trickle of driver & firmware updates to rid of us bugs or add support for features. This means that what works and what doesn’t changes over time. So you have to keep an eye on this. And then we haven’t even mentioned whether it is supported or not and the hassle & risk involved with updating a driver Smile

When it works it rocks and provides great benefits (if not it would have been dead). But it has not always been a very nice story. Not for Microsoft, not for the NIC vendors and not for us IT Pros. Everyone wants things to be better and finally it has happened!

Windows 8 NIC Teaming

Windows 8 brings in box NIC Teaming, also know as Load Balancing and Fail Over (LBFO), with full Microsoft support. This makes me happy as a user. It makes the NIC vendors happy to get out of needing to supply & support LBOF. And it makes Microsoft happy because it was a long missing feature in Windows that made things more complex and error prone than they needed to be.

So what do we get form Windows NIC Teaming

It works both in the parent & in the guest. This comes in handy, read on!

No need for anything else but NICs and Windows 8, that’s it. No 3rd party drivers software needed.
A nice and simple GUI to configure & mange it.
Full PowerShell support for the above as well so you can automate it for rapid & consistent deployment.
Different NIC vendors are supported in the same team. You can create teams with different NIC vendors in the same host. You can also use different NIC across hosts. This is important for Hyper-V clustering & you don’t want to be forced to use the same NICs everywhere. On top of that you can live migrate transparently between servers that have different NIC vendor setups. The fact that Windows 8 abstracts this all for you is just great and give us a lot more options & flexibility.
Depending on the switches you have it supports a number of teaming modes:
- Switch Independent: This uses algorithms that do not require the switch to participate in the teaming. This means the switch doesn’t care about what NICs are involved in the teaming and that those teamed NICS can be connected to different switches. The benefit of this is that you can use multiple switches for fault tolerance without any special requirements like stacking.
- Switch Dependent: Here the switch is involved in the teaming. As a result this requires all the NICs in the team to be connected to the same switch unless you have stackable switches. In this mode network traffic travels at the combined bandwidth of the team members which acts as a as a single pipeline.There are two variations supported.
  1. Static (IEEE 802.3ad) or Generic: The configuration on the switch and on the server identify which links make up the team. This is a static configuration with no extra intelligence in the form of protocols assisting in the detection of problems (port down, bad cable or misconfigurations).
  2. LACP (IEEE 802.1ax, also known as dynamic teaming). This leverages the Link Aggregation Control Protocol on the switch to dynamically identify links between the computer and a specific switch. This can be useful to automatically reconfigure a team when issues arise with a port, cable or a team member.
There are 2 load balancing options:
1. Hyper-V Port: Virtual machines have independent MAC addresses which can be used to load balance traffic. The switch sees a specific source MAC addresses connected to only one connected network adapter, so it can and will balance the egress traffic (from the switch) to the computer over multiple links, based on the destination MAC address for the virtual machine. This is very useful when using Dynamic Virtual Machine Queues. However, this mode might not be specific enough to get a well-balanced distribution if you don’t have many virtual machines. It also limits a single virtual machine to the bandwidth that is available on a single network adapter. Windows Server 8 Beta uses the Hyper-V switch port as the identifier rather than the source MAC address. This is because a virtual machine might be using more than one MAC address on a switch port.
2. Address Hash: A hash (there a different types, see the white paper mention at the end for details on this) is created based on components of the packet. All packets with that hash value are assigned to one of the available network adapters. The result is that all traffic from the same TCP stream stays on the same network adapter. Another stream will go to another NIC team member, and so on. So this is how you get load balancing. As of yet there is no smart or adaptive load balancing available that make sure the load balancing is optimized by monitoring distribution of traffic and reassigning streams when beneficial.

Here a nice overview table from the whitepaper:

Microsoft stated that this covers the most requested types of NIC teaming but that vendors are still capable & allowed to offer their own versions, like they have offered for many years, when they find that might have added value.

Side Note

I wonder how all this is relates/works with to Windows NLB, not just on a host but also in a virtual machine in combination with windows NIC teaming in the host (let alone the guest). I already noticed that Windows NLB doesn’t seem to work if you use Network Virtualization in Windows 8. That combined with the fact there is not much news on any improvements in WNLB (it sure could use some extra features and service monitoring intelligence) I can’t really advise customers to use it any more if they want to future proof their solutions. The Exchange team already went that path 2 years ago. Luckily there are some very affordable & quality solution out there. Kemp Technologies come to mind.

Scalability.You can have up to 32 NIC in a single team. Yes those monster setups do exist and it provides for a nice margin to deal with future needs
There is no THEORETICAL limit on how many virtual interfaces you can create on a team. This sounds reasonable as otherwise having an 8 or 16 member NIC team makes no sense. But let’s keep it real, there are other limits across the stack in Windows, but you should be able to get up to at least 64 interfaces generally. Use your common sense. If you couldn’t put 100 virtual machines in your environment on just two 1Gbps NICs due to bandwidth concerns & performance reasons you also shouldn’t do that on two teamed 1Gbps NICs either.
You can mix NIC of different speeds in the same team. Mind you, this is not necessarily a good idea. The best option is to use NICs of the same speed. Due to failover and load balancing needs and the fact you’d like some predictability in a production environment. In the lab this can be handy when you need to test things out or when you’d rather have this than no redundancy.

Things to keep in mind

SR-IOV & NIC teaming

Once you team NICs they do not expose SR-IOV on top of that. Meaning that if you want to use SR-IOV and need resilience for your network you’ll need to do the teaming in the guest. See the drawing higher up. This is fully supported and works fine. It’s not the easiest option to manage as it’s on a per guest basis instead of just on the host but the tip here is using the NIC Teaming UI on a host to manage the VM teams at the same time. Just add the virtual machines to the list of managed servers.

Do note that teams created in a virtual machine can only run in Switch Independent configuration, Address Hash distribution mode. Only teams where each of the team members is connected to a different Hyper-V switch are supported. Which is very logical, as the picture below demonstrates, because you won’t have a redundant solution.

Security Features & Policies Break SR-IOV

Also note that any advanced feature like security policies on the (virtual) switch will disable SR-IOV, it has to or SR-IOV could be used as an effective security bypass mechanism. So beware of this when you notice that SR-IOV doesn’t seem to be working.

RDMA & NIC Teaming Do Not Mix

Now you need also to be aware of the fact that RDMA requires that each NIC has a unique IP addresses. This excludes NIC teaming being used with RDMA. So in order to get more bandwidth than one RDMA NIC can provide you’ll need to rely on Multichannel. But that’s not bad news.

TCP Chimney

TCP Chimney is not supported with network adapter teaming in Windows Server “8” Beta. This might change but I don’t know of any plans.

Don’t Go Overboard

Note that you can’t team teamed NIC whether it is in the host or parent or in virtual machines itself. There is also no support for using Windows NIC teaming to team two teams created with 3rd party (Intel or Broadcom) solutions. So don’t stack teams on top of each

Overview of Supported / Not Supported Features With Windows NIC Teaming

Conclusion

There is a lot more to talk about and a lot more to be tested and learned. I hope to get some more labs going and run some tests to see how things all fit together. The aim of my tests is to be ready for prime time when Windows 8 goes RTM. But buyer beware, this is still “just” Beta material.

For more information please download the excellent whitepaper NIC Teaming (LBFO) in Windows Server "8" Beta

Working Hard In IT

My view on IT from the trenches

Category Archives: Networking