Bundling Internet Connections to Incrementally Increase Bandwidth Capacity

2009-10-20 by

The diversity of today’s workforce and the increase in the number of remote branch offices, road warriors and telecommuters is a direct result of the benefits of the Internet. The ubiquitous nature of the Web has made it possible to have access to business applications, anywhere, any time. However, the successful delivery of applications over the Internet depends upon the flexibility of the WAN infrastructure.

Until recently, WAN solutions such as bandwidth aggregation were too expensive for small and medium-sized enterprises (SMEs). The use of advanced WAN optimization products also known as WAN link controllers for intelligent and automated link load balancing and failover capabilities are not only affordable, the integration of WAN link load balancing and failover provides SMEs with very cost-effective solutions for assuring network uptime and application availability even when connectivity to an Internet service provider fails.

Get the most out of your Internet connectivity

Bandwidth aggregation combines two or more WAN connections from a single ISP, or different ISPs, and provides Web-based applications the combined total available bandwidth of the multiple links. Advanced bandwidth aggregation techniques support link load balancing to route Internet sessions from congested links to links with more available bandwidth. They also provide automatic failover of Internet sessions from failed links to functionin- links to ensure reliable connectivity.



This diagram shows a WAN link controller conducting load balancing and failover for two Internet links.

Increasing bandwidth once required upgrading to more expensive single-line access technology. An example of upgrading line capacity would be to replace a 1.5 Mbps T1 line with a 45 Mbps T3 line. Few businesses, especially small-to-medium size enterprises, need an increase of this magnitude in one step. However, many do need the ability to add incremental bandwidth capacity over time as business needs expand. Another disadvantage to simply upgrading a single line's throughput is that it still leaves businesses vulnerable to the WAN as a point of failure.

WAN Link Controllers Bring Control to the WAN

WAN link controllers provide the ability to direct Internet traffic to the best performing, most accessible WAN and/or ISP links. Should one of the links become inaccessible due to traffic congestion or failure, the WAN link controller will take that link out of service, and automatically re-direct traffic to other functioning links.

WAN application delivery has emerged as one of the most important technologies in solving the problem of performance and accessibility for applications delivered over the Internet. In addition, by using various link load balancing algorithms, a WAN link controller can distribute users to links that offer the best performance, and links that are the most cost-effective to use.

By aggregating multiple, diverse Internet links from one or more ISPs, WAN link controllers reduce the need to purchase multiple and expensive high-speed links such as T-1s. This enables organizations to increase bandwidth by using cost-effective links without compromising up-time. In addition to managing scalability and redundancy, WAN link controllers utilize all available WAN bandwidth through intelligent link load balancing, with features such as quality-of-service routing and traffic shaping. WAN link controllers provide controls for how bandwidth is used to support applications going over the Internet. This allows the SME to take advantage of the most cost-effective links, while ensuring appropriate levels of bandwidth are available for specific applications.

Bandwidth aggregation of multiple links can be used to increase bandwidth in a more gradual and cost-effective manner. There are three basic types of bandwidth aggregation. The multi-homing approach used by many large enterprises requires the cooperation of multiple telcos and carriers and special routers that use the Border Gateway Protocol (BGP). The cost, complexity and difficulty in securing service provider cooperation for this approach (many ISPs will not support BGP for end users) eliminates BGP as an option for most SMEs. In addition, BGP introduces latency and performance issues that can affect the seamless, uninterrupted delivery of Internet traffic. Furthermore, many ISPs that do support BGP usually do so only for high-cost, high-capacity WAN links.

Another type of bandwidth aggregation approach that is more suited for small-to-medium size enterprises maintains individual IP sessions on multiple links, rather than using BGP to manage the links. This method allows organizations to effectively utilize the total combined bandwidth of up to 15 different ISPs (depending on the product). This is achieved through a combination of intelligent link load balancing, Quality of Service (QoS) rules which determine bandwidth minimums and maximums for specific applications, and other features. No special arrangements need to be made with any ISP, and any kind of WAN link such as DSL, cable, wireless, T1/E1, satellite, frame relay, etc. can be used in any combination. This approach allows organizations to aggregate multiple types of ISP links, avoid exposure to a single point of failure and add additional low-cost links to increase bandwidth as the need arises.

A third approach is site-to-site channel bonding, where WAN link controllers bond multiple Internet links into a single high-bandwidth channel for uninterrupted availability for applications that require connectivity between sites. If one Internet link goes down or degrades in performance, traffic is automatically directed to the best working links without interruption. Channel bonding is a form of packet-based link load balancing which allows for stateful failover of traffic to the best performing links to ensure critical applications avoid problems that occur when they are stopped on one link and restarted over another link. Site-to-site channel bonding ensures that critical applications avoid Internet failures, and are not adversely affected, even after brief disruptions.

Site-to-site channel bonding supports applications that are bandwidth-intensive such as large files. These files may be sent over an open connection, or transferred through a VPN connection to remote locations. Transfer time can be dramatically reduced by combining multiple Internet links, while preventing the need to re-transmit files due to an Internet link interruption which may drop the VPN connection. By adding additional bandwidth connections at a remote location, and incorporating a WAN link controller at each site, the bandwidth of multiple links can be bonded to increase the aggregate throughput – dramatically lowering transfer times. With multiple Internet paths, file transmissions continue even if one of the links fails. See diagram below.

Bandwidth aggregation delivers the following business benefits:

•  Ensures each user has the best network experience possible over the WAN
•  Guarantees traffic will be directed to only “available” WAN links and sites
•  Enables administrators to optimize WAN traffic according to line pricing models and throughput capacity; and
•  Provides QoS and traffic shaping to ensure critical applications get the bandwidth required for smooth performance

Optimizing multi-homed links

Organizations that need true high-availability for application delivery over the WAN will find that aggregating bandwidth by multi-homing ISP links alone will not be sufficient. They will still have to deal with link performance issues because adding additional bandwidth will not adequately solve the problem. Rather, it creates an endless cycle of buying additional bandwidth, while receiving diminishing benefits. Adding to the problem, are new IP services being deployed without having any method to affordably and effectively manage the bandwidth these services consume. It is important to find a balance, without having to make a trade off between critical application deployment, and buying enough bandwidth.

The challenge comes in being able to easily and cost-effectively manage multiple and diverse WAN links based on bandwidth capacity and application usage, and to incrementally add bandwidth in an affordable manner as needed.


Organizations continue to struggle with problems related to delivering high-performing, continuous uptime and high-availability for VoIP, webmail, web portals, and other critical applications. These applications are putting increased stress upon ISP links. An affordable approach to address these issues is the use of bandwidth aggregate, the bundling of multiple ISP links into a single larger virtual connection.

Today’s distributed workforce includes employees located at headquarters, remote branch offices, road-warriors and telecommuters. The Internet is being used to correspond and conduct business with customers and partners, as the ubiquitous nature of the web has made it possible to access to business applications, anywhere, any time. The successful delivery of these applications over the Internet depends upon the flexibility of the WAN infrastructure.

Until recently, WAN solutions such as bandwidth aggregation were too expensive for Small and medium-sized enterprises (SMEs). Today, advanced WAN link controllers are not only affordable, the integration of WAN and ISP link load balancing and failover provides organizations with very cost-effective solutions.




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