10 Reasons your WAN is Broken

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2 Lack of Visibility Most WAN performance problems are driven by underperforming connections or applications. It isn t uncommon to be paying for a 20 Mbps WAN link that performs at 10 Mbps. The root cause is often a handful of specific issues, such as excessive link latency, overly chatty applications, or legacy protocols. The solution may be straightforward, but discovering what problem to solve is the true challenge. You may have traffic coming from a wide variety of sources. The first step to improving network performance and throughput is to dissect those traffic sources, and to understand what they are doing. 2

3 Traffic Shaping and Quality of Service Quality of service policies ensure that the most important needs get priority by assigning applications to classes of service (3-6 levels typically) with traffic policies for each. For example, the top class might be guaranteed 50 percent of the bandwidth. Traffic shaping delays or drops packets from some flows and prioritizes preferred streams. Problems occur with traffic shaping for two main reason. First, an application may need a higher priority level or the traffic class may need more bandwidth. Second, when multiple carriers are involved, it can be difficult to coordinate consistent classes of service. Most importantly, real-time traffic must be kept in the top class all the way through the WAN. 3

4 Not Keeping up with Change A network may once have been perfectly designed and implemented, but not updated for new requirements. Applications are added, traffic patterns change, staff are moved between locations, new offices are built, etc. Organizations deploying an application may not understand the effect it will have on the network, and those responsible for the network may not understand the effect changes will have on applications. Here s a small sample of the things that can cause a network design to be outdated: new data centers, new branches, new applications, changing priorities, enterprise applications, cloud migration, and user growth at peak times. 4

5 Leased Lines or Insufficient Bandwidth Many WANs were built with leased lines including T1, MPLS, and frame relay, but there are better links. Advisors typically recommend looking carefully at your WAN before adding bandwidth. In other words, don t just throw money at the problem. While this is good advice, sometimes you just need more bandwidth. When links really are too slow, adding bandwidth improves throughput. For several reasons, however, performance improvement is seldom linear. One common reason is that applications and protocols aren t designed to take advantage of the extra bandwidth. For example, TCP interacts poorly with long, fat networks, and often does not use all the available throughput. 5

6 Legacy Applications Many businesses cling to outdated applications and platforms from necessity. This leaves IT stuck with the high-cost task of forcing old platforms onto new infrastructure. Old applications can be dependent on old hardware and on old network implementations. An indicator of the prevalence of these legacy applications is the usage of old operating systems. As of early 2018, Windows XP was still running on nearly 7% of machines 16 years after it was released! This indicates a high usage of legacy applications. 6

7 Duplication Duplicate data leads to excessive I/O, network traffic, and storage. Disaster recovery (DR) backups require that large files be transmitted between data centers that are physically far apart. Unless highly optimized file transfer technologies are used, DR applications don t utilize the full WAN bandwidth yet they still cause congestion. As a result, DR backups take excessive (perhaps prohibitive) time and decrease the performance of other applications. 7

8 Paths Routing traffic over unplanned paths can lead to bottlenecks. Some things to consider: do large sources of traffic need more bandwidth than some paths can supply? Is traffic divided between the Internet and MPLS, and is there a planned difference? Should traffic be directed to particular paths for performance purposes? Is there a connection between path selection and service classes? For example, two sites are connected by MPLS and a higher bandwidth Internet VPN link. The network might route traffic from an application like ERP via MPLS, while routing across the Internet VPN as long as the latency isn t excessive. 8

9 Wi-Fi Network performance is most impacted by packet loss and throughput limitations, but increasingly wireless problems are entering the mix. BYOD policies and a general increase in connected devices have made the Wi-Fi environment a pain point. Slow wireless access has many potential causes. These include interference from competing channels or non devices, and overuse. Bit errors are much more likely on wireless links. This results in packet loss, which causes retransmission. Because IP networks operate on the end-to-end principle, a loss on Wi-Fi causes data to be retransmitted across the entire network, not just the wireless portion. This means a user on a poor Wi-Fi connection can generate a disproportionate amount of network traffic, driving congestion. 9

10 Overflowing queues WAN latency has fixed and variable components. The fixed component relates to the route miles a packet travels plus a small fixed time for each router the packet must pass through. A typical WAN link crossing the continental U.S. takes 40 ms or 80 ms for the round trip (RTT). The variable component, known as jitter, is due to queuing congestion at the routers. It occurs when more data enters a router than can exit given the bandwidth available on that link. This can add ms of latency for each occurrence. If the delays are longer, then packets will be dropped rather than be delayed. Overflowing queues are the primary reason for packet loss. 10

11 Congestion Demand for network traffic increases over time. When network traffic exceeds capacity, routers drop packets and this causes data loss. Enterprise data is growing rapidly, new applications are adopted, and growing organizations naturally increase the number of users. As the number of applications grows, the likelihood that one will misbehave or interact poorly with another application increases. According to Cisco, annual IP traffic will reach 3.3 Zettabytes (ZB) by 2021 from 1.2 ZB in While this is global traffic, not your organization, the expectation is for data volume to almost triple over the course of 5 years. The drivers of this traffic increase will affect all organizations. Network congestion is growing and hardware investment is unlikely to keep up. 11

12 By many accounts, there are only three problems with networks: latency, throughput, and packet loss. While these problems are responsible for most of the impacts, they do not suggest the root causes. Why is there packet loss, low throughput, or latency? This ebook highlights some common underlying issues leading to WAN performance problems. Identification of problems is a good starting place to look for improvement. The natural question is now what? In the next piece, What is Network Acceleration, available at we will examine the range of solutions that are commonly used to address these problems.