When I recently rewrote our company's WAN service description, I had to keep in mind that IT management often believes MPLS and virtual private LAN services to be two distinct and separate products. They are, however, very much based on the same technology.
Here's what you need to know. Multiprotocol Label Switching (MPLS) is the protocol that underlies both Layer 3 (typically referred to as MPLS) and Layer 2 services, such as virtual private LAN service (VPLS) and virtual leased line (VLL), which encompass pseudowire point-to-point and multipoint circuits. In the early life of MPLS, the intent was to increase routing performance, which was suffering delays due to a combination of low CPU power versus ever-growing routing tables. As time went on, MPLS evolved to offer traffic engineering (allowing providers to make the best use of resources) and product capabilities such as Layer 2 services.
If we consider (at a high level) why your organization would benefit from MPLS versus VPLS, here are some main drivers:
- Layer 2 VPLS offers an end-to-and capability but allows organizations to self -manage their routing. This may be important if you are trying to use a protocol that is not supported within products offered by traditional Layer 3 service providers.
- Layer 2 services offer a seamless LAN extension. In other words, two offices in different locations appear as if they are located on the same LAN. A good use of this would be cloud-based computing. If one of your hosting facilities reaches capacity, you can tap into a different facility.
- Layer 3 MPLS, also known as a virtual private routed network, or VPRN, provides almost a prepackaged capability. Service providers support this standard service over a national or global network.
If your network requires Layer 3 routing, MPLS ideally provides an opportunity to outsource your routing requirements to the service provider, allowing your IT team to focus on other key areas within the business. In reality, today's networks demand a variety of capabilities, including Layer 3 and Layer 2 services such as VPLS, and VLL or true fiber services. Consider metro area networks where offices are generally located within relatively short distances from each other. These offices would be well-served using dedicated short-haul fiber or VLL services over slightly longer distances. The WAN, by contrast, is best served by the global or national capability of service providers using their full VPLS or MPLS product capability.
Overall, the conversation about MPLS versus VPLS is becoming less prevalent since the objective is to align your business specifics with the products and services that best meet your business requirements. Service providers now offer such a broad range of capabilities that there often isn't a single solution to meet your business needs. The majority of businesses we work with are now deploying hybrid networks that include Layer 2 and Layer 3 capabilities.
MPLS and VPLS both support quality of service, or QoS, for applications. Therefore, the performance across both capabilities is not a concern for today's mission-critical and delay-sensitive applications. We should also not forget a further option when we discuss MPLS versus VPLS. Organizations are also using IPSec-based VPNs to further complement the overall capability of MPLS networks.
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