What is MPLS? Multiprotocol label switching explained

What is MPLS?

The multiprotocol label switching (MPLS) protocol directs network traffic along predefined network paths (also known as label-switched paths or LSPs). By adding an MPLS label to an IP (Internet Protocol) packet, you instruct the router that receives the packet to send it along a specific, predetermined route.

At first glance, you might assume that MPLS labels serve the same function as IP addresses, but that is not the case. An IP address determines what network and network user is to receive a data packet, but MPLS dictates the path through the network that the packet should take.

How does multiprotocol label switching work?

MPLS works by adding numerical labels to data packets, and then using those labels to determine the packet’s path. When you visit a website on your browser, your web requests are divided into packets, each carrying information about its destination and where it’s coming from.

Since the packets are labeled during their transition from layer 2 (layer 2 protocols are responsible for transferring data between nodes) to layer 3 (protocols in layer 3, like the IPsec protocol, cover packet forwarding and routing), MPLS is often called a “layer 2.5 protocol.” Of course, there is no such thing as layer 2.5 — this term is just used to describe the fact that MPLS operates between the two layers.

Let’s break down the steps that a data packet goes through when using MPLS.

1. Label assignment: A data packet enters the MPLS network via the ingress router (also referred to as the label edge router). The ingress router assigns an MPLS label to the packet. This label specifies the route the packet should now take through the network.
2. Label distribution: The ingress router communicates with other routers in the network and shares information about assigned labels and corresponding routes. This process is known as label distribution and often relies on the Label Distribution Protocol (LDP) or the Resource Reservation Protocol (RSVP).
3. Label switching: The labeled packet is moved through the MPLS network. Each network switch, or router, that it passes through uses the packet’s MPLS label to decide where it should go next. Transitions from one switch to the next are called hops, while the overall transfer process is referred to as label switching.
4. Label popping: At each hop in the network, a router can carry out a process known as label popping. Popping means replacing the original MPLS label with a new one. This step occurs when unexpected networking issues arise, meaning that the original route cannot be adhered to.
5. Label removal: The data packet arrives at the last router on its journey, known as the egress router. The egress router removes the packet’s MPLS label and forwards it based on its IP address. At this point, the packet leaves the MPLS network and completes its journey.

What is multiprotocol label switching used for?

MPLS is used to streamline the packet-forwarding process within a network. MPLS allows routers to save time deciphering the destination IP addresses, telling routers exactly where the packet is meant to go as soon as it reaches them. The result is improved speed and efficiency, lower latency, and less risk of network congestion.

Using MPLs also lets administrators create pre-planned paths through their networks, strategically managing the flow of traffic. Without MPLS, an IP packet may take an unnecessarily long and inefficient route to its final destination. Once again, implementing MPLS leads to better overall performance on a network.

Another common use for MPLS is to create private networks. Organizations use MPLS to establish private communication channels between specific nodes on a shared network. In a corporate wide-area network, for example, with employees spread across multiple locations and LANs, you could use MPLS to link dispersed team members together within a single private network.

What is an MPLS network?

The term MPLS network refers to a network of preset MPLS pathways, or LSPs — a network within a network. MPLS networks are created to link a limited group of nodes within a larger network.

You might have 50 users on a wide- or local-area network, and of that 50, 10 are routing traffic to each other using MPLS labeling. The network between those 10 users and their machines is the MPLS network.

While an MPLS network does technically count as a virtual private network, it is important to note that when most people discuss VPNs, they mean commercial client/server VPNs, like NordVPN. Premium VPNs offer encryption, IP address protection, and much more, while an MPLS network does not.

That’s not to say MPLS networks aren’t useful, but it’s important to understand both their benefits and their limitations.

Pros and cons of MPLS

Before deciding whether to use MPLS, consider the following benefits and disadvantages.

Pros

MPLS offers some clear benefits, as listed below.

• Speed. Since packets in MPLS networks travel in predetermined ways, routers don’t need to perform an IP lookup in every step. This means the whole routing process consumes fewer computing resources compared with “normal” routing, and so MPLS connections are faster than normal IP traffic. MPLS can be beneficial when speed is an important factor, especially when running real-time applications.
• Quality. MPLS has QoS (quality of service) options that help packets achieve better performance and efficiency when they travel across the network.
• Remote connection. Since MPLS can be cloud-hosted, you can add new remote connections without having to invest in additional hardware.
• Reduced network congestion. MPLS divides web requests between different routes, thus avoiding network congestion.
• Improved uptime. If a downtime occurs, MPLS can switch traffic to an alternative route if it’s available.
• MLPS for SaaS support. MPLS networks excel in supporting Software as a Service (SaaS) applications.

Cons

Of course, MPLS also brings with it a few downsides.

• User experience. MPLS requires extensive configuration on your router. Setting up the MPLS network yourself is only advisable if you know what you’re doing. Otherwise, leave this task to an IT administrator.
• Cost. MPLS solutions can be costly because you’ll have to pay for your data every month. Internet service providers can set up the whole MPLS infrastructure and maintain it for you, but this will obviously increase the price. You’ll also need specialized routers, known as label switch routers, to read the MPLS labels.
• Less control. Since your ISP configures your network for you, you don’t have full control over it.
• Accessibility. MPLS is not suited for SaaS or cloud applications but for point-to-point connectivity.
• Deployment. It takes several months to deploy MPLS if your company’s offices are located in different countries or even continents.

What’s the difference between SD-WAN and MPLS?

Software-defined wide-area networking (SD-WAN) is a software-based approach to managing a WAN. However, it’s more advanced than MPLS. SD-WAN is more secure, less expensive, and offers better performance.

Both MPLS and SD-WAN are used for network connectivity: connecting users working from home with headquarters or remote branch offices.

Some IT specialists claim that in the future, MPLS will be pushed out by SD-WAN, but both systems have their use cases, and DS-WAN is unlikely to completely replace MPLS in all use-cases.

MPLS vs. a VPN

MPLS and a VPN (virtual private network) are both networking technologies used to improve the performance and security of data transmission over networks, but they’re not exactly the same. While an MPLS network could be described as a VPN, it doesn’t provide all the main benefits people associate with VPN technology.

MPLS optimizes network traffic and routes data packets quickly between the label edge router to the destination, while a VPN creates a secure and private connection between your device and the VPN over the internet.

When it comes to VPN vs. MPLS comparisons, it’s best to see them as two separate tools that can work together, rather than limiting yourself to one or the other. You can use MPLS to connect different branches of your company and a VPN to protect your employees online. Since MPLS doesn’t encrypt your traffic, it’s worth considering VPN solutions to ensure that your online traffic is protected in transit.