Introduction to MPLS and its routing style

Anton P. | August 5, 2021

MPLS refers to a more efficient way of delivering packets to their rightful destination. Generally speaking, all data received or sent travels in the form of packets. Like letters, these packets have a destination listed in them. However, there are no instructions on how the packets should reach their final stop. Now, imagine that your taxi driver steers in circles, picking a route that significantly prolongs your journey. In some cases, data packets take inconvenient paths before arriving at their target. MPLS is a brilliant technique for sending data packets along the shortest and systemic routes.

What is MPLS?

MPLS (Multi-protocol Label Switching) is a data forwarding technology using a unique method for delivering packets. Instead of IP addresses and Layer 3 information, it relies on something called a label.

The label makes all the forwarding decisions in the MPLS universe, such as the route packets need to take. Thus, each packet receives its corresponding label, typically based on its content and format.

Achieving similar results in conventional routing can be laborious. MPLS allows networks to control traffic efficiently, and boost performance, too.

Thus, each packet travels along a predetermined path, and routers no longer need to check their routing tables. Instead of this, the MPLS label serves as instructions on how networks deal with different packets.

The traditional routing explained

Conventional routing leaves a lot of work for the routers. For instance, each router receiving a packet must individually inspect its destination before forwarding.

Furthermore, packets traverse through several layers, including your computer (Layer One) and networks (LAN or WAN, Layer Two). Then, data might still bounce off of a few more layers until it reaches its final stop.

Each router receiving a packet will have to look through its network-layer header and refer to its routing table. Only then can it individually transfer data to the necessary point.

Making routers go through this repetitive process is a time-consuming undertaking. Therefore, conventional routing is not precisely ideal for performance-sensitive activities like video or voice services. For instance, you could experience performance issues during Zoom calls.

How does multi-protocol switching work?

MPLS expedites the routing process and minimizes the tasks routers need to perform for sending packets their merry way. Here is the rundown of how MPLS directs the packet through networks, step by step:

  • The first time a packet lands on a network, the router does all the work necessary. It inspects the type of data a packet contains and its intended destination.
  • After the primary inspection, the router assigns a Forwarding Equivalence Class (FEC). According to it, the packet will receive the MPLS label. The router will then encapsulate it inside a Label-Switched Path (LSP).
  • The main advantage of MPLS is that the packets’ headers will require inspection only once. The subsequent routers will follow the instructions added by the first router in line. Thus, the in-between routers won’t have to waste time on concluding their header analysis.
  • The last router will remove the MPLS label from the packet before forwarding it to the intended destination.

Is MPLS useful today?

Although MPLS brought significant improvements, it is not necessarily ground-breaking at the moment. The rise of cloud computing and SD-WAN have pushed MPLS to the side.

For one, implementing MPLS can be more expensive than choosing the flexible and affordable SD-WAN. However, MPLS supporters and loyal users emphasize that this technique will continue to be relevant. In some instances, it will assist SD-WAN. At the very least, it will continue serving specific business needs, like connecting point-to-point locations.

MPLS and VPN

MPLS VPN refers to a series of techniques for using MPLS to build Virtual Private Networks. It is one of the available use cases of MPLS. For instance, companies could build specific MPLS VPNs to route voice, video, and AMI traffic between substations and data center locations.

MPLS VPN will create a separate private routing table for each customer, known as VRF (Virtual Routing and Forwarding). The downside is that the setup can be rather expensive and difficult to achieve. When users opt for a VPN to circumvent internet restrictions, MPLS will prove rather insufficient unless configured to the highest degree.

However, standard MPLS systems are not substitutes for a VPN. Since fewer routers get to analyze headers, it might be more secure. Nonetheless, MPLS does not apply encryption, meaning that eavesdroppers could view the exchanged data.

So, while they both modify how data travels online, their purpose is applicable in specific scenarios. In some of them, businesses can choose to use both a VPN and MPLS to boost the performance and security of their operations.

Anton P.

Anton P.

Former chef and the head of Atlas VPN blog team. He's an experienced cybersecurity expert with a background of technical content writing.

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