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Site-to-Site DMVPN Per-Tunnel QoS Monitoring with Flow

Organizations often lack visibility to WAN application traffic. Even if there is an SLA and class of service in place, WAN carriers do not provide good statistics about their services. Effective monitoring priorities should include: up/down monitoring, time-stamped centralized logging, capacity-planning statistics, and application performance metrics.

This data can be collected with NetFlow/IPFIX/sFlow or SNMP. An SD-WAN system can provide detailed application statistics and show the results of their synthetic test traffic measurements. Some SD-WAN systems even possess application performance management (APM) functionality.

Who are the players?

Traditional routers are special-purpose computers with very specialized CPUs and operating systems. SD-WAN devices do not necessarily have to be specialized devices. They could be simple x86 servers with compute resources for applying policy and just a few 1GE NICs. However, x86 hardware and standard operating systems may not be capable of connecting TDM-based synchronous interfaces that require a real-time OS. For example, CloudGenix’s SD-WAN devices only support Ethernet interfaces, because Ethernet has become the dominant WAN interface type.

Traditional router-based solutions have evolved and gained more features. Most notably, Cisco’s Intelligent WAN (IWAN) has all the essential SD-WAN features within their routers. However, IWAN requires faster routers like the ISR G2 2900/3900, ISR 4000, or ASR1000 routers to perform some of the more CPU-intensive functions.

Some SD-WAN solutions use commodity servers to either replace existing routers or can be used in conjunction with current gear. Companies like Pluribus Networks and Talari use Super Micro’s x86 hardware. Companies like Viptela, CloudGenix, and Sonus Networks use their own custom hardware.

Vendors like VeloCloud have features that direct cloud traffic to specific cloud service providers, thus improving end-user experience for public cloud applications. Some SD-WAN system vendors, like FatPipe, have been developed from companies that have traditionally offered WAN bonding and WAN link aggregation solutions.

Several of the traditional WAN optimization vendors are labeling what they have traditionally offered as SD-WAN products. Some of the WAN optimization companies that now have features include Riverbed, Citrix CloudBridge, and SilverPeak.

SD-WAN vendors also vary based on their licensing models. Cisco offers Cisco SD-WAN licensing options for IWAN routers. Other SD-WAN vendors may be licensed yearly, based on number of sites, amount of interface bandwidth, or even operate like an equipment lease.

There are also several SD-WAN management systems that act as the centralized controller and policy store and perform many of the features of a traditional NMS. Cisco IWAN solutions can use the Cisco Prime Infrastructure (CPI) version 3.0 system or use the Application Policy Infrastructure Controller (APIC) Enterprise Module (APIC-EM). Other popular SD-WAN management platforms include LiveAction and Glue Networks.

Migration to an SD-WAN can range between gradual and consistent to quick and aggressive. It is highly unlikely that even the most cash-flush enterprises could afford to immediately replace all their WAN hardware. It is more likely that upgrades would occur a few sites at a time as old hardware ages out. Some of these solutions can co-exist with the current routers. Some SD-WAN vendors treat the current IP network as an underlay and could operate in a hybrid deployment. Some SD-WAN solutions can be deployed in a monitor-only mode (like an IDS), then later be put into an active mode (like an IPS) after the organization is comfortable with the solution.


As enterprises continue to do more with less and eke out IT efficiencies, they will be taking a hard look at their WAN costs and link utilization statistics. The SD-WAN market is crowded and vendors are aggressive with pricing and developing new features to remain competitive.

2016 will be the year that most enterprises look to take a step toward SDN with their WANs. Enterprises can benefit financially and operationally from transport independence and intelligent path control, security, auto-provisioning, and increased traffic visibility. End-users will appreciate the improved application performance, intelligent QoS, and traffic optimization. The next step is to determine which SD-WAN product is right for your organization and proceed with deployment.