Achieving High Quality Voiceover-IP Across WANs With Talari Networks APN Technology A Talari Networks Application Note 2012 Talari Networks / www.talari.com
Enterprise-class Voice-over-IP Challenges In recent years, enterprise Voice-over-IP (VoIP) has become a mainstream business service offering a flexible, rich, and cost-effective means of communication. In a report published by Technavio in June 26 th 2012, the Global VoIP Services market in the Telecommunication industry is forecast to grow at a CAGR of 7.1 percent over the period of 2011-2015, with low cost of communication service being one of the key contributing factors of this growth. But poor voice quality and frequent dropped calls can quickly undermine the added value that VoIP can provide an enterprise, leading to poor user acceptance and high complaint volumes. Call quality on VoIP is particularly sensitive to underlying network QOS and will degrade drastically in the presence of packet loss, high jitter and high latency. According to a new report by the business consulting firm Frost and Sullivan, the market for SIP and VoIP trunking services amounts to roughly $2 billion annually. The study suggests that more than 7 million companies are using the voice service. Packet loss results in a choppy or broken voice, dramatically degrading user experience. Even though most CODECs apply a Packet Loss Concealment (PLC) algorithm to regenerate lost packets, the reconstructed packet is only the best guess and the listener will still experience a broken or synthetic voice. A high packet loss rate severely impacts users experience and the impact is even higher when a compressed CODEC is used. Another impairment to take into account is packet latency. With a one-way latency greater than 150 ms or 300 ms round-trip, talkers will interrupt each other and experience talk-over effects. It is therefore crucial to remain within the acceptable latency budget during the whole call. Packet jitter needs to be considered as well. High packet jitter increases distortion. To reduce jitter, packets are usually buffered in the network devices. However, this further increases packet latency in the VoIP call. Avoiding congestion is another challenge to enterprises, as they must provide sufficient bandwidth to support the appropriate number of concurrent VoIP calls alongside other business applications on the network. With each call taking up 24 to 80Kbps of bandwidth, depending on the used CODEC, it is easy to eat up a significant fraction of an expensive T1 MPLS circuit just with voice. And it goes without saying that a failed link cannot carry a voice call. Traditionally an individual call is assigned to a single network link and when that link fails, the call drops. While some underlying networks and VoIP systems will automatically reconnect the call on an alternate link, usually a significant and noticeable gap in the call occurs and often the call must be manually reestablished. These quality challenges, which are frequently linked to the use of public communication services, have forced enterprises to purchase high-cost private wide area network (WAN) links such as MPLS. Page 2 of 7
This is because public network services lack guaranteed end-to-end Quality of Service (QoS), a major requirement for a successful VoIP call. However, enterprise-class VoIP even over a leased line WAN can still be a challenge. To run effectively on a WAN, end-to-end QoS must be provided to ensure the quality considerations listed above are within tolerable ranges. And regardless of the guarantees in the service provider s QoS SLA, after the fact restitution does nothing to retroactively correct poor call quality. Plus, high-quality private WAN/MPLS can be expensive, so satisfying the high bandwidth requirement for VoIP is a constant challenge for IT organizations. Talari s Appliances Ensure Reliable and High-Quality VoIP Using patented Adaptive Private Network (APN) technology, Talari's Mercury appliances address the challenging requirements of running VoIP over a WAN. Talari combines traditional WAN and IP bandwidth sources to provide reliable, resilient and high-quality connectivity between sites. Their appliances are deployed in the main office and branches/remote offices and provide a meshed network of "Conduits" between sites. Each conduit is made of one or more WAN links and the Talari appliance controls and optimizes the use of network resources available within those Conduits to ensure high quality VoIP calls. Resilient Multipath Connectivity: Resilient Multipath Connectivity is a Talari technology within APN that uniquely delivers ultra-reliable, costeffective support for VoIP. It routinely monitors QoS across all available Talari s APN Technology addresses the key factors that affect VoIP call quality: Packet Loss Latency Jitter Congestion Link Failure network paths and chooses network paths with the least packet loss, jitter, and one-way latency for such high-priority real-time traffic. At the start of a call, APN will automatically pick the path with the best characteristics for a voice call (low loss, jitter, and one-way latency.) It continually monitors these characteristics on each path, and will quickly reroute VoIP packets within a fraction of a second to a new path with minimal disruption in call quality. APN adapts to loss, latency, and jitter network events within ~250 milliseconds for domestic connections or ~500-600 milliseconds even for longerdistance international connections. This sub-second response window ensures that VoIP calls will not be dropped during a fail-over. Classes of Service: An APN conduit between two sites can have up to 16 classes of service allowing VoIP packets to be assigned to the appropriate priority relative to other applications such as email or file transfers. This feature guarantees that VoIP packets are not delayed in getting onto the WAN. To determine which traffic is VoIP and deserves real-time priority, Talari s Mercury APN appliances can be configured to honor IP DSCP markings and also can be configured to make this classification decision based on flow characteristics such as port number and/or source or destination IP address. Page 3 of 7
Packet Duplication: To offer the highest possible call quality, it is possible to trade additional inexpensive bandwidth for platinum quality voice. By replicating voice packets over two disparate paths across the network, suppressing duplicates at the receiving appliance, the destination APN appliance will use the most timely of two VoIP packets and be able to hide packet loss or excessive delay on either of the paths. This results in the absolute lowest latency path for each packet and the virtual elimination of dropped packets. Packet Loss Mitigation: Talari Mercury Appliances can be configured to re-transmit lost VoIP packets, a feature not available in UDP. Additionally, since the wait time before requesting the retransmit for an incoming packet is user-configurable, this feature can be used without exceeding the maximum tolerable packet latency for the VoIP call. Bandwidth Augmentation: Talari Networks makes it easy to increase bandwidth, a key factor in ensuring high quality VoIP calls. Using Talari s APN technology, existing broadband or WAN links can be easily augmented with additional links, immediately increasing usable and reliable bandwidth for remote sites. Often this is achieved by leveraging Internet links that are currently used as VPN backup connections or redundant WAN links. APN performs bandwidth optimization and bandwidth management using multiple connections as a single pipe, creating a virtual, software-define WAN from multiple physical links. Dynamic Bandwidth Management: Talari's patented APN technology recognizes and adapts subsecond to the bandwidth usage changes and congestion at both ends of a path. Talari's solution allows the near-end to dynamically manage the bandwidth, not only based on local congestion measurement or static setup, but also on the remote-end s instantaneous use of bandwidth. This feature allows a site with a peak number of VoIP calls to use more bandwidth if other sites are having lower than expected number of calls. Page 4 of 7
1 At the start of a call, APN will automatically pick the path with the best characteristics for a voice call (low loss, jitter, and one- way latency.) 2 APN continually monitors the QoS of each direction on each path, and will quickly reroute VoIP packets within a fraction of a second to a new path with minimal disruption in call quality. 3 If a link fails, APN quickly detects the failure and moves the call packets to a link that is still available, without disrupting or dropping the call. Page 5 of 7
Talari Networks Differences There are many software and hardware solutions that purport to increase the quality of VoIP. But only Talari s patented technology constantly measures the factors that impact VoIP quality and adapts the behavior of network traffic in response to these changing factors. Assess Network Health for VoIP - Talari Networks uniquely continuously monitors each path to collect end-to-end metrics on one-way latency, jitter, packet loss and bandwidth. The health of each path for VoIP calls is monitored end-to-end and decisions are based on the quality of the path, not just if the path is up or down. Optimize Use of Network Resources - Talari s dynamic bandwidth reservation is based on congestion prediction and constantly adapting to instantaneous available bandwidth. Talari also performs traffic shaping to remove burstiness with prioritization based on application class (e.g. realtime VoIP) defined by configuration policies. Eliminate Dropped Calls - Talari Networks performs sub-second path change if any issue such as low performance or link failure is detected. Adding Talari to a network will ensure VoIP calls work without interruption even in the case of link failure or network impairments such as high jitter, latency, or packet loss. Only Talari makes path decisions on a per-packet basis not application flow to deliver the highest possible quality and reliability, insuring no call is dropped during a path change. Calls experience reliable QoS even over best effort networks. Conclusion APN uniquely delivers ultra-reliable and cost-effective support for real-time applications such as VoIP that run across an enterprise WAN. It routinely chooses network paths with the least latency, packet loss, and jitter for high-priority real-time traffic and switches with sub-second response to a better path in the face of high loss or jitter. This ensures "platinum quality" connectivity for VoIP, even when the underlying network is composed of network links with no guaranteed QoS. Page 6 of 7
About Talari Networks Talari Networks is redefining WAN reliability and performance quality. By aggregating multiple broadband links and continuously adapting to the quality of the network, Talari enables true enterprise-class quality and reliability at consumer prices. Talari s patented technology delivers 30-100 times gain in bandwidth per dollar, 40-90 percent on-going WAN cost reductions and greater visibility and reliability than MPLS or any other private network. In 2011, Talari was named a Gartner Cool Vendor and its Mercury T750 won Best of Interop Performance Optimization. For more information, visit www.talari.com. Talari Networks, Inc. 550 S.Winchester Blvd., Suite 500 San Jose, CA 95128 USA +1 408 689 0400 +1 408 864 2124 fax info@talari.com www.talari.com Page 7 of 7