Lync 2013 Bringing a Few Load Balancing Benefits

The load balancing requirements for Lync 2013 will be quite similar to those of Microsoft's previous-generation server for unified communications.

At least that's the viewpoint of an expert with Kemp Technologies. The company is one of about 12 partners that offer qualified load balancer products for Microsoft Lync. Load balancers, which are also called "application delivery controllers," are used with Lync to distribute traffic among servers with the idea of ensuring scalability and redundancy across the service.

For Lync 2010, Microsoft suggests using three possible load balancer configurations, supporting various server roles. A load balancer can be used to support multiple front-end servers in "Enterprise pools." It can be used to connect to an array of "Director pools." Lastly, a load balancer can connect to internal and external network interface cards (NICs) to support an array of "Edge server pools," according to Microsoft's description. Other server roles supported by Lync include "Standard," "Back end," "Audio/video (A/V) conferencing," "Mediation," "Monitoring" and "Archiving."

That's the Lync 2010 architectural scenario, and it's basically the same with Lync 2013. The one exception has to do with Microsoft's addition of the Office Web App Server, which is used right now with Lync 2013 to stream PowerPoint presentations, according to Bhargav Shukla, director of product research and innovation at Kemp Technologies.

"With Lync 2013, most of the workloads have not changed," Shukla said in a phone interview this week. "What did change, though, is the introduction of Office Web App Server. For example, if you are sharing PowerPoint using your Lync client and you are in a meeting and your attendees are going to look at the PowerPoint. With the Office Web App Server, now, they will be able to pull the PowerPoint. They will be able to use the slides regardless of at which point in the presentation you were as the presenter. They will be able to see the slides out of order if they need to refer to something before or after. If they joined late and want to see what they missed, they can skip back, without affecting the ongoing presentation. However, because Office Web App server is a requirement now, you have to consider the requirement of being load balanced."

It's theoretically possible to put all of the server roles on a single server and support 80,000 users with Lync. Shukla has seen a variety of approaches in the field.

"Most of the deployments that we see, you definitely have Edge [server role] on a separate machine -- that is a requirement, so there's no question there," he said. "[With] group chat, we have some people deploy [it] on dedicated servers. We do see the front-end deployments in the Enterprise [server role], which basically requires the back end to be separated and on SQL Server so it would be on its own server. [For] the other roles, we have seen a good mix of separated vs. dedicated. Either they are collocated with the front end or they are separated out if their environment requires it."  

As for how many servers would be needed to support 80,000 Lync users, Shukla is leaving that matter to the Lync experts designing the network. However, there's a strict four-server guidance. One server can have 10,000 users, and you can have up to ten servers in a pool, so that approximates about 80,000 users in a pool, he explained. The number of load balancers required for such a deployment depends on the type of load balancer selected.

With a DNS server, you don't have to send Session Initiation Protocol (SIP) traffic to the load balancer, but a load balancer is still required for the Web traffic (HTTP). And that's for internal network traffic. For outside traffic on the Edge pool, there's a requirement for a load balancer, and there about three architectural options there, Shukla explained. Kemp sells various load balancer products for the purpose.

"We have on the physical front Kemp 2200, 2600, 3600 and 5300: four physical-box models," Shukla said. "You also have an option to get a virtual model which runs on Hyper-V or VMware or one of the virtual platforms. VLM 1000 is the product of choice for those who opt for the VLM in their virtual networks, and those work well on the smaller deployments."

Shukla recommended using the Kemp LoadMaster 5300 to support 80,000 users if consolidating the internal apps and internal clients. Kemp's Exchange calculator can indicate which Loadmaster is the right choice, he added. The main reason to use the Virtual LoadMaster product is convenience and flexibility in deployment, according to Shukla, because the functionality is "pretty much the same" as the hardware product. The one exception is SSL offload, which isn't supported in the virtual version.

In addition to selling standalone products, Kemp distributes its LoadMaster in partnership with original equipment manufacturers of servers. For instance, the company recently announced a product designed for Cisco UCS B-Series blades, as well as one for the Dell R320 server platform.

In terms of resiliency, Lync 2013 offers some additional flexibility.

"Usually, if you think about that two-site deployment for site resiliency in Lync 2010 terms, you used to have two datacenters and two load balancers and you had one pool for each side," Shukla explained. "With Lync 2013, you have the option to expand your pool to the different sites. You can have a single pool stretched over two sites."

As for what's to come at Microsoft's Lync Conference in San Diego on February 19, Shukla said that he expects there will be more deep-dive information presented. At the Microsoft Exchange Conference in September, there was just a little presented about Lync, he said.

Kemp is also taking up some of the slack following Microsoft's decision in September to wind down its Forefront Threat Management Gateway product. Shukla suggested that those reverse-proxy functions can be handled through Kemp LoadMaster.

About the Author

Kurt Mackie is senior news producer for 1105 Media's Converge360 group.


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