The message is finally getting out to small-to-medium sized enterprises (SME): when a wide area network (WAN) link that connects your organization to customers, partners and remote employees fails, no one except your network administrator will know because you deployed a WAN link controller.

Affordable WAN link controllers that are purpose-built for SME’s are able to keep organizations well connected to e-mail, VoIP, ERP, CRM, VPN and other critical applications that rely on the Internet for connectivity. WAN link controllers provide high reliability and much more. They can increase network performance by aggregating two or more WAN lines, such as cable, DSL, wireless, satellite, T1, DS3 and other network links. They can also load balance and provide failover for both incoming and outgoing connections. For example, with inbound connections, when users connect to a site, and one of the service provider network links used by the site has an outage, the WAN link controller acting as the DNS authority removes the address of the downed link so that users will be sent to only the working links. For outbound connections, WAN link controllers can intelligently manage the network by conducting health checks on each WAN link to determine network availability and performance, and load balance each session across the links to deliver the optimal user experience. If a network connection goes down, WAN link controllers can also automatically transfer traffic to the other working links.

This diagram shows how WAN link controllers manager traffic among multiple WAN links, automatically directing traffic to the working WAN link.

Additionally, WAN link controllers can intelligently manage bandwidth by bonding together multiple WAN links. For example, network administrators can combine the bandwidth of a DSL and a cable link to provide greater bandwidth for applications such as digital images, MRIs and X-ray images for healthcare providers. This technique supports many other applications such as voice over Internet Protocol (VoIP), email, video and other applications and media types. Quality of service (QoS) rules can also be set to bandwidth minimums and maximums for specific applications.

This diagram shows haw WAN link controllers combine multiple WAN links to create a bonded channel that can utilize the total throughput of the combined links.

WAN link controllers aren’t entirely new. Large enterprises and Internet service providers have relied on WAN link controllers for many years. So, what has changed? Vendors focused on the small-to-medium size enterprises (SME) have recognized that, just like larger enterprises, SMEs compete in today’s business environment by leveraging the Internet. The Internet plays a vital role in virtually all organizations. Consequently, several vendors have developed WAN link controllers that are affordable to SMEs and have the functionality and performance needed to ensure business activities that rely on the Internet are dependable, fast and have the security they need.

Most small and medium-size businesses not only want to stay connected to their customers, they also need to ensure that their remote employees (telecommuting, or working at branch offices) can stay connected to their corporate headquarters. Losing email connectivity is no longer acceptable. In addition to the phone, email has become the primary means of communication between employees, customers and partners.

Many organizations use WAN link controllers to load balance and provide failover between, for example, their DSL connection and T1 line. In addition to the bandwidth management noted above, small and medium-size businesses also need to consider the following features and functions:

• Failover and Failback: The WAN link controller should provide redundant connectivity to the Internet using two or more separate ISPs or WAN links. If one ISP goes down, the WAN link controller automatically directs traffic (failover) to the other ISP or WAN connection. The WAN link controller should also return traffic to the first ISP when the connection is restored.
• Virtual Private Network (VPN) Support: Just a few years ago, many WAN link controllers could accommodate only one VPN at a time; not of much use to the SME with greater than one remote worker. Now, many WAN link controllers support multiple VPN tunnels. In addition to providing VPN failover and redundancy, some vendors have built-in firewall and VPN gateways for greater security. This integration also enables SMEs to have greater functionality and device consolidation and lower equipment, management and maintenance costs.
• WAN Link Failover: While there are different ways to direct Internet traffic, organizations that rely on the Internet need more than the ability to manage inbound traffic among multiple sites. They also need intelligent outbound load balancing and failover.
• Security: Increasingly, firewall and VPN gateway security is being combined in a single device. Most WAN link controllers support Internet Protocol Security (IPsec). IPsec support is important for deploying a VPN when there are several nodes to support because security can be handled without requiring changes to individual computers, which can be time-consuming. Moreover, some secure sites fail to work if a user’s IP address switches in the middle of a session, as can happen with dual WAN routers.
• Dynamic Host Configuration Protocol Support: DHCP is a communication protocol that enables network administrators to centrally manage and automate the assignment of Internet Protocol (IP) addresses within an organization’s network. Without DHCP, IP addresses must be entered manually at each computer within an organization, and a new IP address must be entered each time a computer moves to a new location on the network. Not all WAN link controllers support DHCP.
• Bandwidth Aggregation: In addition to boosting data throughput, bandwidth aggregation has another benefit for some users, namely, revenue generation. For example, business offices, apartments and condominiums are now offering WAN connectivity to occupants and tenants who need bandwidth aggregation and inbound/outbound failover, but cannot afford it. They may have large companies as tenants that typically have their own IT infrastructure. Smaller tenants, such as SMEs, also like the idea of having these services available to them, especially when they host their own email and have experienced ISP outages.
• Quality of Service (QoS): QoS is the ability to prioritize network traffic to ensure that adequate bandwidth is always available to specific bandwidth-intensive applications, especially during periods of congestion. QoS rules determine bandwidth minimums and maximums for specific types of traffic and use load balancing and automatic failover to direct this traffic to links with sufficient bandwidth. Based on user-defined QoS policies, WAN link controllers can control the link bandwidth allocations to support applications that are prioritized, and over which ISP links they are being transported. IT staff can set up QoS rules to determine bandwidth limits for specific applications based on protocol type, source port, destination port, and source IP -- or any combination of these.

Summary
What type of WAN link controller is right for your network? There are many different types from which to choose. Some are referred to as dual WAN routers that are typically limited to two links, provide limited outbound management and offer no inbound management. Vendors that are in the “value” part of the market offer WAN link controllers that can provide greater functionality at an affordable price. While other vendors focused on meeting the needs of large enterprise customers offer high-end products that may be “over-kill” in terms of cost and features for an SME. It is important to find the product with the best price/performance value for your business.

About the author: Marc Goodman is the director of marketing at Ecessa, a manufacturer of advanced WAN Optimization products that provide WAN and ISP link aggregation, intelligent load balancing, failover, QoS and VPN load balancing and failover within a single device.