Why DC-DC WAN optimization matters

Roy Illsley/Ovum
OvumWAN optimization is not a single technology or market. Ovum classifies it as three different technologies or markets: data center to branch, asymmetric, and data center to data center.
 
It is in the latter market, where high-speed multi-gigabit links between data centers (DCs) effectively form a high-speed WAN, that Ovum sees problems with application performance. These specialist WAN environments are under increased pressure to deliver critical business applications to strict service level agreements (SLAs), while also maximizing the utilization of resources.
 
However, current approaches and technologies are delivering sub-optimal performance in the WAN. The DC-DC WAN link is therefore becoming a potential bottleneck for application performance and the answer is not more bandwidth, but a fresh approach to traffic flow management. Infineta has just released FlowTune, its solution for situations such as this. Ovum believes that the techniques used by FlowTune address the specific problems of application performance over multi-gigabit links.
 
Congestion prevention is better than cure
 
In most inter-DC scenarios the application performance is affected by one main offender: packet loss. The cause of this packet loss can be attributed to three main factors: WAN congestion, WAN bit errors, congestion on the LAN/WAN edge.
 
The typical approach to remedy WAN congestion is to use aggressive retransmission of the packets, while with WAN bit errors the common solution is to use forward error correction, and the traditional approach to remedy congestion on the LAN/WAN edge is Layer-2 quality of service (QoS). However, this final remedy is generating the sub-optimal performance on inter-DC WANs.
 
The typical approach is to limit the use of available bandwidth to say 70% and use flow-prioritization as a method of ensuring QoS at Layer-2. However, this approach fails because of contention between aggressive flows, which in turn affects flows throughput and leads to an impact on business logic and under-utilization of the WAN.
 
Infineta’s FlowTune technology addresses the underlying cause of the problem (congestion at the LAN/WAN edge) and applies QoS at Layer-4, resulting in a network free of packet loss as a result of queue overruns. By adjusting the speed of the traffic depending on the circumstances, FlowTune uses the same approach as that used on many busy roads, but takes the analogy further by adding a second dimension, and prioritizing the traffic according to business importance.
 

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