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How to Optimize a Wide Area Network (WAN)

Improving your WAN through link aggregation, optimization, and virtualization ensures high network availability and increased quality of experience (QoE).


A WAN is a telecommunications network that connects different computer networks, typically local area networks (LANs), and spans a large geographical area. They can be private networks that connect different locations of a business or they can be public. The internet is the most famous public WAN.

Typically, TCP/IP is the protocol used in modern WANs, and LANs usually connect to the WAN via a physical or virtual router.


WAN Link Aggregation

WAN link aggregation is also referred to as multilink aggregation, and sometimes as link-load balancing. WAN aggregation can be deployed as a single- or dual-ended solution. As a single-ended solution, it usually focuses on the internet-facing connections of a business. In this case, sessions are always mapped to a given link at session initiation and the link-load balancing capabilities support more bandwidth and provide higher application availability in case one or more of the links being aggregated fails (although active sessions tied to the failed link usually are lost).

As a dual-ended capability, for example, as part of software-defined WAN (SD-WAN) offerings, WAN link aggregation improves throughput between locations. Most session-steering SD-WAN offerings limit individual application sessions to a single link, although when a link dies usually the sessions failover to another link in the bundle and are not broken. Advanced SD-WAN offerings can use all the bandwidth across multiple WAN links even for a single large TCP session, and even when the bandwidth, latency, and loss characteristics of the WAN connections are very different.


WAN Optimization

WAN optimization is a dual-ended offering that uses a collection of techniques for reducing bandwidth consumption and improving application performance across WANs. WAN optimization as a solution and a market segment was very popular in the 2006-–2016 timeframe as enterprise WAN administrators sought to deal with the limited bandwidth available on frame relay and MPLS WANs in the face of server consolidation at a handful of data centers and/or headquarters. WAN optimization’s application-specific proxy technology for Microsoft’s CIFS file transfer protocol was useful for improving file transfer performance of older versions of Microsoft’s protocol during server consolidation.

While there remains a place for WAN optimization technology in a world of high-bandwidth internet links and ever-greater focus on SaaS and cloud access, SD-WANs are generally a better way to solve the problems associated with improving enterprise WANs.

WAN Optimization

WAN Optimization Technologies

WAN optimization uses a combination of data transfer-reduction technologies, application-specific proxies, and lower-level TCP protocol optimization technologies to help mitigate the effects of low bandwidth and high latency on application performance.

  • Data compression– Reduces the payload size of network packets to lower bandwidth consumption.
  • Data deduplication– Drastically reduces the bandwidth consumed for redundant data over the WAN when the same data is accessed at a remote location multiple times.
  • TCP protocol optimization– Multiple techniques, including but not limited to connection pooling, WAN buffering, and TCP termination, minimize and mitigate the effects of packet loss on high latency WANs, significantly improving application performance in some cases.
  • Application protocol optimization– Spoofs and manages chatty application protocols locally, by proxy, to minimize the effects of latency and packet loss on high-latency WANs.
  • The Microsoft CIFS application proxy made a huge impact and can sometimes offer significant help. In a multilink SD-WAN world, with the appropriate protocol technology, and given the reality of more applications moving to the cloud, most application proxies offer minimal benefits, if any.
  • Moving from WAN optimization technology to SD-WAN– WAN optimization technologies are efficient at removing unnecessary traffic over the WAN. SD-WANs offer many more benefits: the ability to lower costs and enable greater network agility with diverse high bandwidth, low-cost internet connections. SD-WANs also help simplify, control, and automate WAN deployment and ongoing management. Many SD-WAN solutions also include WAN optimization as an option.
WAN Optimization Technologies

SD-WAN Architecture

The best way to improve your WAN today is with SD-WAN technology. SD-WANs offer significant agility, flexibility, and cost advantages over traditional MPLS-only WANs. An SD-WAN provides:

  • A secure, flexible, virtual WAN overlay fabric supporting multiple WAN links, including lower-cost internet links
  • A controller architecture with centralized management, reporting, and policy control
  • Branch office simplification abilities, including zero-touch provisioning (ZTP)
  • Superior access to cloud and SaaS
  • Choice of physical or virtual appliances

In addition to the above, a failsafe SD-WAN—such as offered by Oracle Communications—tames the chaos of the shared public internet and delivers reliability, high availability, and predictable application QoE not offered by competing SD-WAN solutions.

SD-WAN Architecture

WAN Virtualization

WAN virtualization combines two or more network connections of any type to create a single, virtual pipe between locations. This enables cost-efficient, high-availability, and high-bandwidth capacity. All aggregated links are active, and the full amount of bandwidth is always available. It can augment or replace expensive private MPLS circuits with low-cost broadband internet links and achieve excellent application performance and reliability, even with congestion events.

A well-designed WAN virtualization solution will perform dynamic, real-time traffic engineering. It will react subsecond, not only to link failures, but also to congestion-related network problems. WAN virtualization supports both session-based steering and per-packet traffic engineering. The advantage of per-packet traffic engineering is real-time reliability and predictability for all applications. WAN virtualization is more comprehensive than WAN link aggregation. It can easily handle connections with significant differences in bandwidth, latency, jitter, and packet loss. It will also determine where to steer traffic based on current, real-time conditions for each network connection.

WAN virtualization is a term that pre-dates SD-WAN, and has largely been replaced by that term, even though only a small number of today’s SD-WAN offerings deliver true WAN virtualization.

WAN Virtualization

SD-WAN Security

When researching an SD-WAN solution, there are several key security considerations. A secure SD-WAN offering must as a baseline be able to encrypt all traffic using 128- or 256-bit AES encryption and have secure, dynamically changing encryption keys. Better still, it should support cipher block chaining, per-protocol sequence numbers and per-session symmetric encryption. It needs to be able to support all three of the fundamental network security architectures that enterprises employ: fully distributed, centralized at private data centers or colocation facilities, or integrated with cloud-based network security. Plus, it should support integrated network security as well as the ability to overlay with an enterprise’s existing network security architecture. SD-WAN also needs to support not only basic stateful application firewall services, but features such as zone-based security, policy-based filtering for granular levels, and layers of security aligned on a per-application or traffic-type basis, traffic isolation and traffic segmentation by user or VRF. Service chaining should be supported, and SD-WANs should integrate with cloud-based security solutions.

SD-WAN Security