Boosting Internet Access Resilience, ISP Multihoming Explained



Internet access for organizations today is no longer about connectivity for email and web browsing. A stable Internet connection is a vital component in the chain of IT systems required to conduct business. Typically, in the past, the focus around Internet connectivity has been on cost, with vendors providing solutions allowing organizations to spread their traffic across consumer and enterprise products.

This approach is all good and can provide significant cost savings, mainly when employee traffic is directed over low-cost consumer products such as ADSL; however, resilience in conducting B2B business through front-end servers hosted in your DMZ becomes a significant concern.

In this scenario, a dead Internet link can mean loss of revenue and even, potentially more severe, brand damage. In this paper, we discuss several methods that can improve the resilience of an Internet link. While this sounds like it should be a simple case of connecting to multiple Internet Service Providers, the devil, as they say, is in the detail.

Boosting Internet Access Resilience, ISP Multihoming Explained 1

Mission-critical Internet

Business networks have been mission-critical for some time now, and the focus on resilience and business continuity has always been top of any CIO’s mind. However, this focus’s general areas of interest were restricted to internal networks and systems. With more and more business being conducted directly via the web or B2B over Internet links to systems hosted in DMZs, it is no longer permissible for an Internet link to be down. Loss of access to the Internet can directly impact revenue generation, especially today, as the business operating models begin shifting towards off-site cloud computing and software as a service.

A solution to the problem

Multihoming is a method whereby a company can connect to multiple ISPs simultaneously. The concept was born from the need to protect Internet access in either an ISP link failure or an ISP internal failure. In the earlier days of Internet access, most traffic was outbound, except for email. An Internet link failure left internal users with no browsing capability and email backing up on inbound ISP mail gateways. Once the link was restored, so was browsing and email delivery. The direct impact on the business was relatively small and mainly not revenue effective. Early solutions to this problem were to connect multiple links to the same ISP, but while this offered some level of link resilience, it could provide no safeguards against an internal ISP failure.