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Multiprotocol Label Switching (MPLS) – Definition, Features, Differences, Pros, and Cons

Multiprotocol Label Switching (MPLS) – Definition, Features, Differences, Pros, and Cons

Multiprotocol Label Switching (MPLS)

Multiprotocol Label Switching (MPLS) is a technique, not a service so that it can offer anything from IP VPN to metropolitan Ethernet. It is expensive, so with the advent of SD-WAN, companies are trying to find ways to optimize their use against less expensive connections such as the Internet.

Did you ever purchased something online and then tracked the package? And he noticed that he makes strange and illogical stops throughout the country.

It is similar to how IP routing works on the Internet. When an Internet router obtains an IP packet, that packet does not contain information beyond a destination IP address. There are no instructions on how that package should arrive at its destination or how it should be treated along the way.

Each router must make an independent forwarding decision for each packet based solely on the network layer header of the packet. Therefore, each time a packet arrives at a router, the router must “think” where to send the packet next. The router does this when referring to complex routing tables.

The process is repeated in each jump along the route until the package finally reaches its destination. All those hops and all those individual routing decisions result in poor performance for time-sensitive applications such as video conferencing or VOIP

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What is Multiprotocol Label Switching (MPLS)?

Multiple Protocol Label Switching (MPLS), that old WAN workhorse launched at the turn of the century, addresses this problem by establishing predetermined and highly capable routes.

Using MPLS, the first time a packet enters the network, it is assigned to a specific forwarding equivalency class (FEC), which is indicated by adding a short bit sequence (the tag) in the packet.

An individual router in the network has a table that indicates how to handle the packets of a specific FEC type, as the packet has entered the network, the routers do not need to perform a header analysis. In contrast, subsequent routers use the tag as an index in a table that offers them with a new FEC for that packet.

Due to the same MPLS, network skills to handle packets with particular characteristics (such as coming from specific ports or transporting traffic from specific application types) in a consistent manner. Packages that transport traffic in real time, such as voice or video, can be easily assigned to low latency routes throughout the network, something that is difficult with conventional conventional routing

The critical point of the architecture with all this is that the tags deliver a mode to attach additional info to each packet, information that goes beyond what the routers had previously.

How does Multiprotocol Label Switching work?

The beauty of MPLS is that it is not tied to any underlying technology. It was designed in the days of ATM and frame relay as an overlay technique designed to simplify and improve performance: that’s the “multiple protocol” portion.

ATM and frame relay are reserved memories, but MPLS is still alive in the backbone networks of operators and enterprise networks. The most common use cases are branches, campus networks, metropolitan Ethernet services and companies that need quality of service (QoS) for real-time applications.

MPLS Layer 2 or Layer 3?

A big question arises whether MPLS is a Layer 2 or Layer 3 service. But MPLS does not fit perfectly into the OSI seven layer hierarchy. Whereas, one of the key benefits of MPLS is that it separates the forwarding links of the underlying data link service. Additionally, MPLS can be used to create forwarding tables for any underlying protocol.

Specifically, MPLS routers establish a tag-switching route (LSP), a predetermined route to route traffic in an MPLS network, according to the criteria of the FEC. Only after an LSP has been established can MPLS forwarding occur. LSPs are multi-directional, which means that the return traffic is sent through a different LSP.

When an end user sends traffic to the MPLS network, an MPLS tag is added through an MPLS entry router at the edge of the network. The MPLS label consists of four subparts:

The tag contains all the information of the MPLS routers to control where the packet must be advanced.

Experimental: New bits are used for Quality of Service (QoS) to form the priority that the labeled packet must have.

Bottom of the stack: the bottom of the pile tells the MPLS router if it is the last leg of the trip and there are no more labels to worry about.

Time-To-Live identifies how many jumps the packet can make before discarding it.

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MPLS Pros and cons

The pros of MPLS are scalability, performance, better bandwidth utilization, reduced network congestion and a better experience for the end user.

Multiprotocol Label Switching itself does not provide encryption, but it is a virtual private network and, as such, is partitioned off the public Internet. Therefore, MPLS is considered a safe mode of transport. And it is not weak to a denial of service attacks, which could affect networks based on pure IP.

On the downside, MPLS is a service that must be purchased from an operator and is much more expensive than sending traffic over the public Internet.

As companies expand to new markets, they may find it difficult to find an MPLS service provider that can offer global coverage. Typically, service providers combine universal coverage through partnerships with other service providers, which can be costly.

And MPLS was designed at a time when branches sent traffic back to a headquarters or data center, not to today’s world, where branch workers want direct access to the cloud.

Is Multiprotocol Label Switching dead?

Gartner raised that provocative question in 2013 and responded by guessing that MPLS would continue to be an vital part of the WAN landscape, but that most companies would move slowly into a hybrid environment that would consist of both MPLS and public Internet networks.

MPLS will continue to have a role that connects specific point-to-point locations, such as large regional offices, commercial facilities with point-of-sale systems, local manufacturing facilities and multiple data centers. And it is required for applications in real time.

But enterprise WAN architectsWAN architects must make a risk/reward calculation between the superior but expensive performance of MPLS versus the cheaper but less reliable Internet performance, which brings us to a new and exciting technology called SD-WAN.


Each technology has there own specialization in modern WANS. SD-WAN is the application of network concepts defined by software (SDN) to the WAN. It means the implementation of edge SD-WAN devices that apply rules and policies to send traffic along the best route.

SD-WAN is a transport-independent overlay that can route any traffic, including MPLS. The advantage of SD-WAN is that a corporate WAN traffic architect can be located at a central point and easily apply policies on all WAN devices.

On the contrary, with MPLS, the predetermined routes must be carefully provisioned and once the fixed circuits are working, make changes.

After MPLS network deployment, it offers specific performance for real-time traffic. Software Defined WAN can route traffic along the most efficient route, but once those IP packets arrive on the open Internet, there are no performance assurances.

The most sensible strategy in the future will be to download all possible MPLS traffic to the public Internet but continue using MPLS for urgent applications that require guaranteed delivery. Nobody wants to get caught in the spotlight when the monthly videoconference of the CEO with the employees of the branch falls in the middle of the sentence.

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