Why is Lync The Killer SDN Application?

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The key to showing the promise of SDN is to find a real-world application to showcase capabilities.  I recently wrote about using SDN to slice education networks.  But this is just one idea.  When it comes to real promise, you have to shelve the approach and trot out a name.  People have to know that SDN will help them fix something on their network or optimize an troublesome program.  And it appears that application is Microsoft Lync.

MIssing Lync

Microsoft Lync (neè Microsoft Office Communicator) is a software application designed to facilitate communications.  It includes voice calling capability, instant messaging, and collaboration tools.  The voice part is particularly appealing to small businesses.  With a Microsoft Office 365 for Business subscription, you gain access to Lync.  That means introducing a voice soft client to your users.  And if it’s available, people are going to use it.

As a former voice engineer, I can tell you that soft clients are a bit of a pain to configure.  They have their own way of doing things.  Especially when Quality of Service (QoS) is involved.  In the past, tagging soft client voice packets with Cisco Jabber required setting cluster-wide parameters for all clients.  It was all-or-nothing.  There were also plans to use things like Cisco MediaNet to tag Jabber packets, but this appears to be an old method.  It was much easier to use physical phones and set their QoS value and leave the soft phones relegated to curiosities.

Lync doesn’t use a physical phone.  It’s all software based.  And as usage has grown, the need to categorize all that traffic for optimal network transmission has become important.  But configuring QoS for Lync is problematic at best.  Microsoft guidelines say to configure the Lync servers with QoS policies.  Some enterprising users have found ways to configure clients with Group Policy settings based on port numbers.  But it’s all still messy.

A Lync To The Future

That’s where SDN comes into play.  Dynamic QoS policies can be pushed into switches on the fly to recognize Lync traffic coming from hosts and adjust the network to suit high traffic volumes.  Video calls can be separated from audio calls and given different handling based on a variety of dynamically detected settings.  We can even guarantee end-to-end QoS and see that guarantee through the visibility that protocols like OpenFlow enable in a software defined network.

SDN QoS is very critical to the performance of soft clients.  Separating the user traffic from the critical communication traffic requires higher-order thinking and not group policy hacking.  Ensuring delivery end-to-end is only possible with SDN because of overall visibility.  Cisco has tried that with MediaNet and Cisco Prime, but it’s totally opt-in.  If there’s a device that Prime doesn’t know about inline, it will be a black hole.  SDN gives visibility into the entire network.

The Weakest Lync

That’s not to say that Lync doesn’t have it’s issues.  Cisco Jabber was an application built by a company with a strong networking background.  It reports information to the underlying infrastructure that allows QoS policies to work correctly.  The QoS marking method isn’t perfect, but at least it’s available.

Lync packets don’t respect the network.  Lync always assumes there will be adequate bandwidth.  Why else would it not allow for QoS tagging?  It’s also apparent when you realize that some vendors are marking packets with non-standard CoS/DSCP markings.  Lync will happily take override priority on the network.  Why doesn’t Lync listen to the traffic conditions around it?  Why does it exist in a vacuum?

Lync is an application written by application people.  It’s agnostic of networks.  It doesn’t know if it’s running on a high-speed LAN or across a slow WAN connection.  It can be ignorant of the network because that part just gets figured out.  It’s a classic example of a top-down program.  That’s why SDN holds such promise for Lync.  Because the app itself is unaware of the networks, SDN allows it to keep chugging along in bliss while the controllers and forwarding tables do all the heavy lifting.  And that’s why the tie between Lync and SDN is so strong.  Because SDN makes Lync work better without the need to actually do anything about Lync, or your server infrastructure in general.


Tom’s Take

Lync is the poster child for bad applications that can be fixed with SDN.  And when I say poster child, I mean it.  Extreme Networks, Aruba Networks, and Meru are all talking about using SDN in concert with Lync.  Some are using OpenFlow, others are using proprietary methods.  The end result is making a smarter network to handle an application living in a silo.  Cisco Jabber is easy to program for QoS because it was made by networking folks.  Lync is a pain because it lives in the same world as Office and SQL Server.  It’s only when networks become contentious that we have to find novel ways of solving problems.  Lync is the use case for SDN for small and medium enterprises focused primarily on wireless connectivity.  Because making Lync behave in that environment is indistinguishable from magic, at least without SDN.


If you want to see some interesting conversations about Lync and SDN, especially with OpenFlow, tune into SDN Connect Live on September 18th.  Meru Networks and Tech Field Day will have a roundtable discussion about Lync, featuring Lync experts and SDN practitioners.

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