A Good Reason to Increase The Amount of Voice Traffic Across Your WAN

Does this story sound familiar?  You are on a conference call with a team from around the world and all of a sudden, in mid-sentence, one of the speakers “drops off” the call.  Or better yet, the voice quality starts to deteriorate with echo and the notorious “tinny” voice creeping into the conversation. The odds are that you have experienced this many times if you leverage a VoIP or an IP-based teleconferencing service. Most of the time people attribute the problem to a poor call system or conferencing provider. In reality, issues in the wide area network could be the culprit. What in the WAN can impact voice traffic? Regardless of WAN link type, e.g. MPLS, Broadband, LTE, Satellite, multiple factors, such as poor underlying infrastructure, heavy usage, long distances, and interference, can impact the quality and availability of a WAN link. How do these factors manifest themselves from a network perspective? As packet loss, delay, and jitter.

Before we get to the details of potential ways to address these challenges, let’s review some of the characteristics of voice traffic including the network requirements to deliver good voice service. VoIP and teleconferencing tools are real-time services. They require constant, reliable delivery of packets with a small variance between the arrival of each packet. Basically, voice applications are very sensitive to packet loss, delay and jitter. Traditional techniques to address these issues, such as re-transmission of a lost packet, are not applicable with real-time applications since they will usually introduce a delay which will violate a basic real-time application requirement.

How can you mitigate the impact that the WAN has on your voice and other real-time applications? The first step is to increase the number of links that you have come into each of your WAN sites. Typically, a Hybrid WAN is deployed where Internet WAN links are introduced alongside an existing MPLS environment. By having multiple WAN links, your WAN nodes, such as a Talari Appliance, can choose the best path for application traffic and adjust path decisions based upon the current state of the WAN. For more information regarding this capability, see the first blog post in this series, Maximize Application Performance and Uptime with a Talari SD-WAN, that discusses intelligent load balancing and fast failover. Both of these capabilities help ensure application SLAs over the WAN.

Beyond Intelligent load balancing we have another tool that can help deliver a quality user experience for real-time applications; packet duplication. Packet duplication in this context refers to having a WAN node send traffic over all WAN links at the same time. When the packets arrive at the remote node, the receiving device will take the first packet, regardless of which link the packet traversed, and forward it to the destination client. As the remaining duplicate packets arrive, they are discarded. With this approach, the packets are in a race across all the WAN links with the “winner” being forwarded and the losers being discarded; guaranteeing that the best path will support the transmission of a packet. If a packet is lost on one path, the expectation is that one of the packets traversing the other paths will arrive i.e. we always expect one packet to cross the finish line. Since all of the packets are sent at the same time, we do not introduce an incremental delay that traditional packet re-transmission delivers.

So what is the downside of packet duplication? Increased WAN bandwidth consumption. Because of this, we recommend that you selectively leverage this capability and enable it for select mission critical applications and utilize traditional intelligent load balancing to support bulk applications such as file downloads and Internet browsing.

Visit our just published Broadband Report that delivers quantified details on how packet duplication and other capabilities of a Talari Thinking SD-WAN can help your voice, interactive and bulk traffic meet your application SLA over a Hybrid-based SD-WAN.

For the next blog in this series, I will discuss how Talari delivers rapid and easy deployment, monitoring, and reporting of an SD-WAN infrastructure.

Categories: Application Performance/Application Quality, Hybrid WAN, Software Defined WAN (SD-WAN)


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