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MPLS Tunnels

Multiprotocol Label Switching (MPLS) is an ISP-provided networking service that uses labels to switch traffic between sites faster than traditional IP routing. It supports flexible site connectivity, quality of service prioritization, and full-mesh topology without additional physical links.

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About this video

Multiprotocol Label Switching (MPLS) is a provider-managed networking service that businesses subscribe to in order to connect multiple sites across a shared infrastructure they do not directly control. Unlike traditional IP routing, which requires each router along a path to examine the destination IP address, decrement the time-to-live field, and recalculate packet checksums at every hop, MPLS assigns a label to each packet as it enters the network. Subsequent routers forward traffic based solely on that label, bypassing the overhead of full Layer 3 processing and delivering significantly faster switching performance. Because it operates between the traditional Layer 2 and Layer 3 boundaries, MPLS is not constrained to a single link type and can function across diverse underlying technologies, including DSL and other variable-speed connections. This flexibility means that even sites with limited or slower access options can maintain full connectivity to the broader MPLS network without disrupting overall performance. Beyond raw speed, MPLS provides meaningful operational advantages for enterprise environments. Quality of service is a core capability — traffic such as voice can be tagged with a specific label on ingress and prioritized throughout its path to the destination, ensuring time-sensitive applications perform reliably. MPLS also enables full-mesh connectivity across all connected sites without requiring dedicated point-to-point circuits between each location, simplifying network design while reducing infrastructure costs. Together, these characteristics make MPLS a widely adopted choice for organizations that need reliable, high-performance, multi-site connectivity through a managed service provider.

What you'll learn

What's covered

MPLS (Multi-Protocol Label Switching)

Aligned to

Cisco CCNA
3.2 Determine how a router makes a forwarding decision by default
4.7 Explain the forwarding per-hop behavior (PHB) for QoS
1.2 Describe characteristics of network topology architectures

Key terms

Multiprotocol Label Switching
MPLS
A high-performance packet-forwarding technique that directs traffic using short fixed-length labels rather than network addresses, enabling fast switching independent of upper-layer protocols. MPLS is widely deployed by service providers to build scalable VPNs, traffic-engineered WAN paths, and quality-of-service-enabled networks.
Layer 3
The Network layer of the OSI model, responsible for logical addressing and routing packets between networks.
Packet
A unit of data formatted for transmission over a network, containing a header, payload, and sometimes a trailer.
Time to Live
TTL
A value in a packet that limits its lifespan on a network, preventing it from circulating indefinitely.
Quality of Service
QoS
A set of techniques used to manage network traffic by classifying, marking, and prioritizing certain data types to ensure consistent performance for latency-sensitive applications such as voice and video. QoS mechanisms include traffic shaping, queuing, and policing applied at each network device.
Label Switching
A forwarding mechanism that routes traffic based on short fixed-length labels rather than performing a full Layer 3 routing table lookup at each hop.

Transcript

What MPLS Is

Another common protocol out there is MPLS, or multi-protocol labeled switching. It's a service that internet service providers provide for their customers, so it's something that a business would subscribe to.

Routing Across a Provider Network

Let's take a look at a scenario here. Let's say this is a network provider's network, and this is a network we don't really have control over - we're actually subscribed to a service, and we're subscribed to the service through a company that has multiple sites, so we are connected into this network at multiple locations.

When a packet gets routed - let's say we want a packet that's getting routed from the headquarters office to maybe some sort of satellite campus down here - what's going to happen is that packet's going to come into the router, and then it's going to get forwarded on to the next hop, and then to the next hop, and then to the next hop, and then to its final destination.

All along the way here these are layer 2 networks, so that layer one and layer two gets pulled away and a new layer one and two gets formed for every single connection along here. Also it has to take a look at that layer three and pull out the destination IP address, look it up in the routing table, it needs to decrement the time to live, it needs to recalculate that checksum that's in there for accuracy. So it's got a lot that it needs to do for these packets.

How MPLS Differs

Multi-protocol label switching is a type of switching, so it operates quite a bit differently. One thing to note about this is it's not really layer two, because it can go across a lot of different types of links here, but it's also not layer three, in that it's not doing routing - it's doing switching here.

So what does that look like? What happens is that when the information comes into the router, it gets tagged with a label, hence the label part of this. Then all these routers here along the way will actually forward that traffic based off of this label. It's actually much faster to do it this way, rather than digging into the layer three and doing the decrementing the time to live and all of that stuff. It's just using these labels to switch at a much faster pace to get to its location.

Advantages

There are several advantages to MPLS. Number one: let's say over here our headquarters office, maybe we have a connection here, and maybe over here at this satellite campus we don't have access, so maybe we have to use DSL or some sort of slower connection here. Well, MPLS allows us to really deal with whatever is available to us, whatever resources, so it still allows us to have any kind of site connectivity to this network.

It also has this switching involved with it, and since it's switching we have a quality of service. So we can tag the traffic as it comes into it with a label that's specifically for voice, and it gets prioritized to the end route, and it can be much faster because of that. So we've got quality of service that we have there.

Another thing too is we can create a full mesh without any extra lines here. So we can create connectivity from all of these different sites really easily, and we can have that full mesh.

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