In this article, we learn about Multiprotocol Label Switching, How MPLS Works, Components of MPLS, Multiprotocol Label Switching Advantages and Disadvantages.
Multiprotocol Label Switching
Wide Area Networks (WANs) are the main application for Multiprotocol Label Switching (MPLS), a sophisticated packet-forwarding and networking technology that effectively routes and transports data over intricate networks.
MPLS use short, fixed-length labels to identify the path packets take, as opposed to conventional Internet Protocol (IP) routing, where routers utilize lengthy network addresses to make intricate forwarding decisions for each packet.
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How MPLS Works
Label-Based Forwarding
Sending packets down predefined network pathways known as Label-Switched pathways (LSPs) is the primary feature of MPLS.
Ingress Stage (Label Assignment/Push): The ingress router, also known as a Label Edge Router or LER, assigns a Forwarding Equivalence Class (FEC) to incoming data packets, including IP packets, as they enter the MPLS network. Then, depending on factors like destination, service type, or Quality of Service (QoS), the LER appends an MPLS header with one or more labels (a label stack).
Core Stage (Label Switching/Swap): Only the topmost label on the packet is examined by intermediate routers, sometimes referred to as Label Switch Routers (LSRs) or transit routers, inside the MPLS core. They conduct a swap operation, changing the incoming label with a new outgoing label, then advance the packet down the LSP using this label as an index to rapidly identify the next hop. Data transmission is accelerated by doing away with the requirement for resource-intensive IP routing table lookups at each hop.
Egress Stage (Label Removal/Pop): Using standard Layer 3 IP routing rules, the packet is routed to its destination after the MPLS header is removed (popped) when it reaches the last MPLS router (Egress LSR or LER). Penultimate hop popping (PHP) is the term for this removal that frequently takes place at the penultimate hop, which is the hop that comes before the egress router.
Multiprotocol and Layer Location
Multiprotocol: The phrase “Multiprotocol” refers to MPLS’s independence from protocols. IP packets (IPv4 and IPv6), Ethernet, Asynchronous Transfer Mode (ATM), Frame Relay, and Digital Subscriber Line (DSL) are just a few of the various forms of traffic (payloads) that it may transport. As long as the router can read the MPLS labels, the underlying network protocol has no bearing on the forwarding choice.
Layer 2.5: Because its header is placed in between the Data Link Layer (Layer 2) and Network Layer (Layer 3) headers in the OSI seven-layer structure, MPLS is sometimes referred to as a Layer 2.5 protocol.
Components of MPLS
MPLS requires specialized roles for network devices:
| Component | Role |
|---|---|
| Label Edge Router (LER) / Provider Edge (PE) Router | Operates at the edge of the MPLS network, adding labels (push) to incoming packets and removing labels (pop) from outgoing packets. |
| Label Switch Router (LSR) / P Router | Core routers inside the MPLS network that process and swap labels. |
| Customer Edge (CE) Router | The router at the customer’s network edge that connects to the PE router. |
| Label Switched Path (LSP) | The pre-established, unidirectional path that labeled packets follow through the network. |
| Forwarding Equivalence Class (FEC) | A group of data packets that are treated the same way and assigned the same label for forwarding along a specific LSP. |
The 32-bit MPLS header also contains fields for Traffic Class (TC) (3 bits, used for QoS prioritization) and Time to Live (TTL) (8 bits, used for loop prevention).
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Multiprotocol Label Switching Advantages
MPLS is mostly utilized nowadays for its sophisticated traffic management and service capabilities, despite the fact that it was first created to speed up routing a aim that is now less important due to contemporary hardware acceleration:
Quality of Service (QoS): Using the Traffic Class field, MPLS allows network managers to priorities time-sensitive traffic, such as VoIP and video, so that these applications receive enough bandwidth and experience less jitter and delay.
Traffic Engineering (TE): By enabling packets to be guided via particular, optimized pathways (LSPs) that may not be the quickest route, MPLS offers control over network traffic flow, avoiding congestion and making effective use of network resources.
Virtual Private Networks (VPNs): Service providers frequently utilize MPLS to build scalable Layer 2 and Layer 3 VPNs (L2VPNs and L3VPNs), which logically and securely divide client traffic across a common infrastructure.
Reliability: With recovery periods similar to SONET rings (less than 50 ms), MPLS offers a strong architecture for quick recovery and rerouting in the case of network outages.
Scalability and Performance: MPLS offers continuously excellent performance and is built to handle increases in network needs.
Disadvantages of MPLS
Despite its advantages, MPLS has a number of disadvantages, particularly when considering contemporary cloud computing:
Cost: Because MPLS guarantees high capacity and performance standards, it is typically more expensive than traditional broadband internet services.
Complexity and Setup: Management and implementation are intricate processes. LSPs frequently need human configuration, which hinders rapid network scaling.
Security Limitations: MPLS does not automatically offer encryption, although it does offer traffic separation. To secure sensitive data, additional security measures (such as firewalls, VPNs, or encryption) must be put in place independently.
Cloud Inefficiency: When it comes to accessing cloud applications, the conventional MPLS hub-and-spoke approach is inefficient since it frequently necessitates backhauling traffic through the company’s headquarters, which has a substantial negative influence on performance.
Many organizations have migrated to or enhanced MPLS with more recent technologies, such as Software-Defined Wide Area Networking (SD-WAN), as a result of MPLS’s difficulties. Through the use of several forms of connection, including reasonably priced broadband internet, SD-WAN provides centralized control, flexibility, and cost savings. By combining MPLS with SD-WAN, a hybrid solution may be produced, keeping MPLS’s dependability for important traffic while using SD-WAN for other types of traffic.
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