Networking: MPLS or the Internet? Not an All or Nothing Deal

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Networking: MPLS or the Internet? Not an All or Nothing Deal
By Jim Metzler

July 1, 2008 —

Having spent previous columns discussing MPLS (Multi-Protocol Label Switching) technology, I now want to introduce to the discussion a different approach to wide area networking—an approach based on leveraging the Internet. This is not an all-or-nothing proposition. I do not see the question facing IT organizations as being, “Do you use MPLS or do you use the Internet?” Rather, I see the question as being, “When and where do you use MPLS and when and where do you use the Internet?”

Some reasons why MPLS has been so successful in the marketplace are that it provides predictable latency and packet loss characteristics along with quality-of-service functionality that allows for the convergence of voice, video and data traffic within a single service offering. However, one of the disadvantages of MPLS is that, in most instances, it is relatively expensive and there tends to be a long lead time associated with deploying new MPLS services.

MPLS also tends to be complex, precluding virtually all IT organizations from deploying private MPLS networks. Instead, when an IT organization acquires MPLS services from a carrier, (e.g., AT&T) they usually acquire a managed service.

As is the case with most services provided by a carrier, MPLS services typically come with a service level agreement (SLA) that describes the key characteristics of the service. This can include time to install a new service along with metrics for the promised availability, delay and loss. If the carrier does not live up to the SLA, there are penalties.

The problem is that the SLAs associated with MPLS services tend to be weak. For example, the SLAs are primarily reactive in focus; e.g., the computation of an outage begins only when the customer opens a trouble ticket. Not only is the computation of the SLA metrics done in a way that is unfavorable to the customer, the level of compensation for violation of SLAs remains quite modest.

Further weakening the value of these SLAs is the fact that the SLA metrics are primarily calculated as network-wide averages rather than for a specific customer’s traffic or for a particular site. As a result, it would be possible for a company’s data center to receive notably poor service in spite of the fact that the network-wide SLA metrics remain within agreed bounds. In addition, many of the carriers have some unique quirks in their SLAs. For example, one carrier excludes from their availability target any network outage of less than a minute in duration.

The bottom line is that MPLS is a fine service for providing connectivity between an organization’s mid-sized and large offices. Given its price and complexity, MPLS may not be appropriate to provide connectivity to smaller offices.

There is, however, a large and growing requirement for WAN connectivity that has nothing to do with the traditional task of providing connectivity between and among an organization’s offices. This requirement for WAN connectivity is driven by many factors, including home workers for whom MPLS is almost certain to be too expensive and too complex.

It is also driven by the movement to software as a service, the burgeoning deployment of wireless devices such as PDAs and the continually increasing movement to deploy browser-based applications. All of these trends mean that users are increasingly accessing applications over the Internet.

Because the reasons for utilizing the Internet are so compelling, service providers such as Akamai have begun to offer an Internet overlay service. In its simplest terms, these services involve adding a wide range of functionality on top of the Internet. This functionality is intended to improve the performance of the Internet.

One of the most important pieces of functionality of an effective Internet overlay service is route optimization. The goal of route optimization is to improve the performance of IP networks. A route optimization solution measures the performance of multiple paths through the network and chooses the optimal path from origin to destination. Route optimization reduces the end-to-end delay and loss that are associated with the Internet.

There are, of course, many other techniques, such as compression, that can also be part of an Internet overlay services. I will look at these techniques in detail in a future column when I discuss WAN optimization solutions in general. In the meantime, for more information on WAN optimization, see the free report, “The 2008 Application Delivery Handbook.”

Jim Metzler has more than 30 years of professional experience in the networking industry. Reach him at jim@ashtonmetzler.com.

Related Search Term(s): Networking, Akamai

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