WAN Optimization: Strategies & Techniques

Quick Definition: WAN optimization is a set of techniques used to increase the efficiency of WAN connections.

Wide-area networks (or WANs) are the highways that keep the internet moving, connecting our homes and businesses to data centers, cloud providers, and, most importantly, to each other. They enable these connections at high speeds, low latencies, and across vast distances. Without these techniques, WANs can't carry the punch that our constantly connected lives and work culture require.

Optimizing WAN performance is an important topic to keep our connections working as efficiently as possible. Let's explore WAN optimization to see how it can improve our connections, what solutions are available, and what advantages and disadvantages to consider. 

What is WAN Optimization?

The primary objective of WAN optimization is to enhance data transfer by reducing latency and optimizing the usage of already available bandwidth. It does not involve changes to the WAN infrastructure, such as buying faster connections or running more fiber. Instead, it's about making intelligent decisions in how data is processed and transmitted across the WAN.

WAN optimization uses various techniques to address the challenges of transmitting data across long distances. TCP optimization, data deduplication and compression, caching, and forward error correction are all ways of improving network traffic transmission. Using some or all of these techniques together can streamline data flow. In the next section, we'll explore each of these techniques.

WAN Optimization Techniques

Now that you understand what WAN optimization is, let's take a deeper look at the strategies used to improve performance and how they work. 

TCP Optimization

TCP (Transmission Control Protocol) is a common protocol for transmitting data across networks. One of its defining features is a system of back-and-forth communications to confirm that sent data was received intact on the other end (or ACK in TCP lingo). This confirms the reliability of sent data, but it adds overhead and slows down the transmission process.

TCP optimization comes to the rescue by fine-tuning TCP transmissions to reduce the overhead they create. TCP window scaling increases the size of the transmission window, sending more data before awaiting an ACK and reducing the total number of ACKs. Selective acknowledgment (SACK) reduces the number of packets that are retransmitted if one is lost. 

Data Deduplication and Compression

Data deduplication eliminates redundant data. You might be familiar with this technique from data backups; when performing a server backup, identical copies of a file are only backed up once to save time and storage space. For WAN optimization, a common use case is branch offices. Appliances on each end of the WAN connection cache data and inspect requests. When identical data is requested, a local copy is provided, eliminating the need to retransmit.

Compression works like you would expect. Data is reencoded to reduce file size on the fly before being sent out the WAN and then decompressed when it is received. Data deduplication and compression both reduce the amount of data sent over your WAN connections, accelerating transfer rates.

Caching

Caching involves storing a copy of frequently accessed data, usually closer to the end user, to reduce transfer times and relieve some network load on the original data storage location. A popular use of caching is with CDNs, or Content Delivery Networks. 

AWS runs a CDN service called CloudFront. When you enable it on another service like Amazon S3, CloudFront will cache the files in your S3 bucket at AWS edge data centers all over the world. When a user requests a file from your bucket, AWS automatically routes that request to the edge location nearest to the user. The user gets their file faster, and there's less load on the main AWS data centers.

Forward Error Correction

Forward Error Correction (FEC) is a mechanism on some routers. An extra, redundant packet is sent along with other intended packets. If one packet is lost, the receiving router can rebuild the lost packet using the extra data. Think of it like RAID 5, where the data is written redundantly across the disks. Without requiring lost packets to be retransmitted, data transfers can be more efficient, but at the expense of constantly adding redundant packets.

Choosing a WAN Optimization Solution

With so many different techniques at play in WAN Optimization, choosing a solution is anything but a one-size-fits-all situation. There are lots of variables at play:

• Network topology: Is your network built around an HQ data center and multiple branch offices? Data deduplication would be valuable as many users are probably opening the same files in each branch. Is everything in the cloud with worldwide users? Caching with a service like CloudFront will speed up file transfers for all.

• Compatibility: Some WAN optimization techniques are based on features of switches or routers. Do yours support the features you need? Error correction, for example, must be supported and enabled on the routers between two offices to work.

• Cost: Cost is always a huge factor in any project, and you must ask if the outcome justifies the cost. TCP optimization might be as simple as checking a box on the equipment you already have in production. But if it involves ripping out and replacing hardware, you must be sure that the improvements are worth it. 

WAN Optimization Solutions

As data continues to grow, doing more with the bandwidth that we have will be a never-ending problem. Many vendors, though, are providing comprehensive solutions, combining the techniques we've discussed into holistic product WAN optimization suites.

• Riverbed SteelHead: Claiming to be "The #1 WAN optimization solution worldwide," SteelHead combines data deduplication, compression, and application acceleration to maximize network performance.

• Cisco WAAS (Wide Area Application Services): Networking juggernaut Cisco provides this solution, which combines high-end routers and virtualization appliances working together to reduce bandwidth for all manner of business apps.

• HPE Aruba (formerly Silver Peak Unity): The Aruba platform is a cloud-based SD-WAN solution that minimizes latency and improves bandwidth with one-click deployment. 

Advantages and Disadvantages of WAN Optimization

Faster WANs have obvious benefits: quicker data transfers, greater efficiency, and happier users. There can also be cost savings by reducing the need to spend more for greater bandwidth. Some solutions, like caching, also offer bonus benefits of reliability; if the main site is down, then cached content points act as backups.

There are disadvantages to consider, however. The cost to implement some of these solutions can be high, requiring major hardware purchases. Of course, with greater functionality comes the need for IT staff to run it; you will need either experienced new hires or pay for training to get current staff up to speed. Finally, greater complexity means more can go wrong. Troubleshooting can become costly and time-consuming.

Conclusion

WAN optimization can be a powerful tool in any network admin's toolbelt for increasing WAN performance, reducing latency, and providing a better user experience. By employing any or all of these techniques, you can see significant improvements in the efficiency of your WAN connections. Though there are complexities, challenges, and costs involved, it's worth analyzing if the benefits are worthwhile for your organization.

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