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Understanding MPLS Networks – Unraveling the Inner Workings

MPLS is sometimes called a Layer 2.5 protocol since it runs at an OSI model layer typically positioned between conventional Layer 2 and Layer 3 specifications.

Take, for example, an enterprise that wants to bridge sites together over long distances. It would take a lot of rules to write in the hardware forwarding tables for Ethernet, ATM, Frame Relay, and Synchronous Optical Networking (SONET). MPLS provides an alternative.

mpls networks


How does MPLS works? A data packet utilizes intricate routing tables to determine how to reach its destination when traveling across the internet. Every router the packet passes through necessitates a forwarding choice, which affects how healthy end users and apps work.

MPLS eliminates this by attaching a label to each packet that tells routers exactly where to send it. It reduces the number of IP lookups that must be performed, enabling fast packet transfers.

Each packet is assigned a label when it enters the network from an outside provider and continues to travel to multiple Label Switch Routers (LSRs). Routers read the packet label and follow instructions as the packet travels through these in-between stops. Labels can be stacked on top of one another, and when a packet reaches an egress LSR, it “pops” the label to reveal the destination IP address.

In addition to accelerating the delivery of business services such as VoIP and videoconferencing, MPLS improves bandwidth utilization, scalability, and security. Additionally, it assists businesses in cutting expenses by lessening the demand for pricey hardware, including switches and routers, in outlying areas.

Label Switching

With label switching, packets are augmented with labels that identify the location of the destination. Each device in the network reads these labels to determine what action to take with each packet. For example, a router may swap a packet’s top label with another one and send it down a specific path associated with that label. This process reduces router functionality to switch functions, dramatically speeding up data transfer by eliminating the need for complex routing tables.

The labels inserted or stripped are based on the Quality of Service (QoS) requirements established by the carrier. These QoS parameters are incorporated into the MPLS header and applied to each packet by the first router that handles it. It ensures that every packet receives the bandwidth, low latency, and minimal jitter required for a high-quality connection.

As an alternative to MPLS, enterprises can use SD-WAN to deliver the same underlying connectivity and performance at a much lower cost and with greater flexibility. However, it’s important to remember that SD-WAN does not replace MPLS as it relies on the telecom provider to manage your network infrastructure and provide robust network reporting capabilities. In addition, it still requires backhauling your traffic through your carrier’s network to the cloud or your on-premise or colocation data center.

Path Selection

When a packet is sent over the internet, each router that handles it must decide how to send it to its destination. It can take a long time since each decision requires complex routing tables. It can affect the quality of service for voice-based applications and other mission-critical data transmissions.

With MPLS, routers can have prebuilt lookup tables that tell them how to forward the packet based on its label. It eliminates the need for complex IP lookups and can speed up data transfer.

Each router examines its label stack to decide how to forward the packet. The topmost label tells the router which path to follow. The router then performs a swap, push[c], or pop[d] operation on the packet’s label stack, allowing it to send the packet along that path.

The router then checks the coverage of these paths and selects one that covers the most links. The process takes a lot of time because the number of visible links can grow exponentially in an extensive network. Fortunately, this computation can be sped up by using graph decomposition techniques. The process also scales well with the number of monitored paths. A 40-monitor network can handle up to 20 million routes. In comparison, a 60-monitor network could have up to 80 million routes.

Virtual Private Networks (VPNs)

A VPN encrypts data sent over an Internet connection, making it difficult for anyone to see what you’re searching for or browsing. It’s used by organizations to secure their employees’ connections when working remotely. Still, personal users are becoming increasingly interested in VPN technology after security scandals and net neutrality controversies hit the news.

A provider-provisioned VPN uses preconfigured tunneling protocols on the service providers’ routers, allowing them to offer virtual vast area network (WAN) services to multiple customers on a single infrastructure. Often, these VPNs are called Layer 3 VPNs. In addition to encrypting data, MPLS-based L3VPNs can prioritize specific types of traffic over others to ensure that voice and video are always delivered with the highest possible quality of service.

Dedicated VPNs, deployed on-premises in the enterprise, use the same encryption standards as IPSec but are typically paired with a more vital, more reliable security protocol such as SSL or TLS. The most popular dedicated VPN protocols are SSTP and OpenVPN. PPTP, once a standard option for free VPNs, is no longer considered a safe choice because of its many known security flaws.

VPNs can also provide better security by requiring user authentication through a password or a physical security key plugged into the device. It can be done through a built-in operating system feature or third-party software.


About Erik

Erik is the owner and main editor of techmanik.com. He has been working in computers and information technology for more than 20 years. He’s a business analyst, developer and avid traveler.

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