Category Archives: Load Balancing

Options For A Highly Available Load Balanced RD Gateway Server Farm on Hyper-V

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When you need to make the RD Gateway service highly available you have some options. On the RD Gateway side you have capability of configuring a farm with multiple RD Gateway servers.image

When in comes to the actual load balancing of the connections there are some changes in respect load balancing from Windows Server 2008 R2 that you need to de aware of! With Windows 2008 R2 you could do:

  1. Load balancing appliances (KEMP Loadmaster for example, F5, A10, …) or Application Delivery Controllers, which can be hardware, OEM servers, virtual and even cloud based (see Load Balancing In An Ever More Demanding Virtualized & Cloudy World). KEMP has Hyper-V appliances, many others don’t. These support layer 4, layer 7, geo load balancing etc. Each has it’s use cases with benefits and drawback but you have many options for the many situations you might encounter.
  2. Software load balancing. With this they mean Windows NLB. It works but it’s rather limited in regards to intelligence for failure detection & failover. It’s in no way an “Application Delivery Controller” as load balancer are positioned nowadays.
  3. DNS Round Robin load balancing. That sort of works but has the usual drawbacks for problem detection and failover.  Don’t get me wrong for some use cases it’s fine, but for many it isn’t.

I prefer the first but all 3 will do the basic job of load balancing the end-user connections based on the traffic. I have done 2 when it was good enough or the only option but I have never liked 3, bar where it’s all what’s needed, because it just doesn’t fit many of the uses cases I dealt with. It’s just too limited for many apps.

In regards to RD Gateway in Windows Server 2012 (R2), you can no longer use  DNS Round Robin for load balancing with the new HTTP transport. The reason is that it uses two HTTP channels (one for input and one for output) and DNS round robin cannot guarantee that both these connections will be routed trough the same RD Gateways server which is a requirement for it to work. Basically RRDNS will only work for legacy RPC-HTTP. RPC could reroute a channel to make sure all flows over the same node at the cost of performance & scalability. But that won’t work with HTTP which provides scalability & performance. Another thing to note is that while you can work without UDP you don’t want to. The UDP protocol is used  to deliver graphics with a better user experience  over even low quality networks for graphics or high and experiences with RemoteFX. TCP (HTTP) is can be used without it (at the cost of a lesser experience) and is also used to maintain the sessions and actions. Do note that you CANNOT use UDP alone as these connections are established only after the main HTTP connection exists between the remote desktop client and the remote desktop server. See Don’t Forget To Leverage The Benefits of RD Gateway On Hyper-V & RDP 8/8.1 for more information

So you will need a least Windows Network Load Balancing (WNLB) because that supports IP affinity to make sure all channels stick to the same node. UDP & HTTP can be on different nodes by the way. Also please not that when using network virtualization WNLB isn’t a good choice. It’s time to move on.

So the (or at least my) preferred method is via a real “hardware” load balancer.  These support a bunch of persistence options like IP affinity, cookie-based affinity, … just look at the screenshot below (KEMP Loadmaster)

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But they also support layer 7 functionality for better health checking and failover.  So what’s not to like?

So we need to:

  1. Build a RD Gateway Farm with at least two servers
  2. Load balance HTTP/HTTPS for the RD Gateway farm
  3. Load balance UDP for the RD Gateway farm.

We’ll do this 100% virtualized on Hyper-V and we’ll also make make the load balancer it self highly available. Remember, removing single points of failure are like bottle necks. The moment you take one away you just hit the next one Smile.

Kemp has a great deployment guide for RDS on how to do this but I should ass that you could leverage SUB Virtual Services (SUBVS) to deal with the other workloads such as RD Web Access if they’re on the same server. They don’t mention this in the white paper but it’s an option when using HTTP/HTTPS as service type for both configurations. #1 & #2 are the SUB Virtual Services where I used this in a lab.

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But for RD Gateway you can also leverage the Remote Terminal Service type and in this case you won’t leverage SUBVS as the service type is different between RD Gateway (Remote Terminal) and RD Web Access (HTTP/HTTPS). This is actually used by their RDS template you can download form their support site.

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Hope this helps some of you out there!

Don’t Forget To Leverage The Benefits of RD Gateway On Hyper-V & RDP 8/8.1

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So you upgraded your TS Gateway virtual machine on W2K8(R2) to RDS Gateway on W2K12(R2) too make sure you get the latest and the greatest functionality and cut off any signs of technology debt way in advance. Perhaps you were inspired by my blog series on how to do this, and maybe you jumped through the x86 to x64 bit hoop whilst at it. Well done.

Now when upgrading or migrating from W2K8(R2) a lot of people forget about some of the enhancements in W2K12(R2). This is especially true of you don’t notice much by doing so. That’s why I see people forget about UDP. Why? Well things will keep working as they did before Windows Server 2012 RDS Gateway over HTTP or over RPC-HTTP (legacy clients). I have seen deployments where both the Windows and the perimeter firewall rules to allow UDP over 3391 were missing. Let alone that UDP Transport over port 3391 was enabled in the transport settings.  But then you miss out on the benefits it offers (an improved user experience over less than great network connections and with graphics) as well on those of that ever more capable thingy called RemoteFX, if you use that.

For you that don’t know yet:  HTTP and UDP protocols are both used preferably by RD Gateway and are more efficient than RPC over HTTP which is better for scaling and experience under low bandwidth and bad connectivity conditions. When HTTP transport channels are up (in & outgoing traffic), two UDP side channels are set up that can be used to provide both reliable (RDP-UDP-R) and best-effort (RDP-UDP-L) delivery of data. UDP also leveraged SSL via the RD gateway because is uses Datagram Transport Layer Security (DTLS). For more info RD Gateway Capacity Planning in Windows Server 2012. Further more it proves you have no reason not to virtualize this workload and I concur!

So why not set it up!?  So check you firewall rules on the RD Gateway Server and set the rules accordingly. Do the same for your perimeter firewalls or any other in between your users and your RD Gateway.

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Under properties of your RS Gateway server you need to make sure UDP is enabled and listening on the needed IP address(es)

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A client who connects over your RDS Gateway server, Windows Server 2012(R2) that is, and checks the network connection properties (click the “wireless NIC” like icon in the connection bar) sees the following: UDP is enabled. imageIf they don’t see UDP as enabled and they aren’t running Windows 8 or 8.1 (or W2K12R2) they can upgrade to RDP 8.1 on windows 7 or Windows Server 2008 R2! When they connect to a Windows 7 SP1 or Windows 2008R2  machine make sure you read this blog post Get the best RDP 8.0 experience when connecting to Windows 7: What you need to know as it contains some great information on what you need to do to enable RDP 8/8.1 when connecting to Windows 7 SP1 or Windows 2008 R2:

  1. “Computer ConfigurationAdministrative TemplatesWindows ComponentsRemote Desktop ServicesRemote Desktop Session HostRemote Session EnvironmentEnable Remote Desktop Protocol 8.0” should be set to “Enabled”
  2. “Computer ConfigurationAdministrative TemplatesWindows ComponentsRemote Desktop ServicesRemote Desktop Session HostConnectionsSelect RDP Transport Protocols” should be set to “Use both UDP and TCP” => Important: After the above 2 policy settings have been configured, restart your computer.
  3. Allow port traffic: If you’re connecting directly to the Windows 7 system, make sure that traffic is allowed on TCP and UDP for port 3389. If you’re connecting via Remote Desktop Gateway, make sure you use RD Gateway in Windows Server 2012 and allow TCP port 443 and UDP port 3391 traffic to the gateway

Cool you’ve done it and you verify it works. Under monitoring in the RD Gateway Manager you can see 3 connections per session: one is HTTP and the two others are UDP.

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Life is good. But if you want to see the difference really well demonstrated try to connect to Windows 7 SP1 computer with RDP8 & TCP/UDP disabled and play a YouTube video, then to the same with RDP8 & TCP/UDP enabled, the difference is rather impressive. Likewise if you leverage RemoteFX in VM. The difference is very clear in experience, just try it! While you’re doing this look a the UDP “Kilobytes Sent” stats (refresh the monitoring tab, you’ll see UDP being put to work when playing a video on in your RDP session.

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Load balancing Hyper-V Workloads With High To Continuous Availability With a KEMP Loadmaster

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I’m working on some labs and projects with KEMP Loadmaster load balancing appliances (LM 2400, LM-R320) That will lead to some blog post on  load balancing several workloads, which are all on Windows Server 2012 R2  Hyper-V or integrate in to Azure. The load balancers used in the labs are the virtual appliances, depending on the needs and environment these are a very good, cost effective option for production as well and depending on the version you get they scale very well. Hence their use in cloud environments, they will not hold you back at all!

To stimulate your interest in load balancing and high availability I’ve put up a video on load balancing RD Gateway services. Consider it a teaser or introduction to more about the subject.

Why use an appliance (hardware/virtual)? Well let’s look at the 2 alternatives:

  • Round robin DNS, which is also sometimes used is just to low tech for most real life scenarios and sometimes can’t be used or is less efficient which impacts scalability and performance. On top of that it doesn’t provide health checking for failover purposes.
  • I’ve also said  before that while Windows NLB  provides layer 4 load balancing out of the box it’s pretty basic. It also often causes a lot of network grief and the implementation can be tedious. This has not improved in an ever more virtualized & cloud based world. On top of that, when network virtualization comes into play you might paint yourself into a corner as those two don’t mix. But if that’s not a concern and you’re on a budget, I’ve used it with success in the past as well.