Multiprotocol Label Switching (MPLS) is a method developed in the 1990s to enhance the speed of network connections. While the public Internet forwards packets from one router to the next until they reach their destination, MPLS directs packets along predetermined network paths. The objective is to minimize the time routers spend deciding where to forward each packet, ensuring that packets consistently follow the same route.
To illustrate, envision planning a long drive. Instead of specifying all the towns and cities on the route to the destination, it is more efficient to identify the roads heading in the right direction. Similarly, MPLS focuses on identifying paths or network “roads” rather than a sequence of intermediary destinations.
MPLS is positioned at OSI layer “2.5,” situated below the network layer (layer 3) and above the data link layer (layer 2).
How does routing normally work?
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When transmitting data from one computer to another through the Internet, the information is fragmented into smaller units known as packets, rather than being sent as a whole. For example, think about this webpage—it reached your computer or device in a series of packets that were reassembled before being displayed. Each packet contains a header with information about its source, destination, and the corresponding destination IP address, much like an address on a piece of mail.
For a packet to reach its designated endpoint, routers play a crucial role in forwarding it from one network to the next until it reaches the network housing its destination IP address. Subsequently, that network forwards the packet to the specified address and the corresponding device.
Before routers can direct a packet to its final IP address, they must determine its intended route. Routers achieve this by referencing and maintaining a routing table, offering instructions on how to forward each packet. Each router examines the packet’s headers, consults its internal routing table, and transmits the packet to the next network. The subsequent router in that network repeats the process, and this sequence continues until the packet reaches its destination.
While this routing approach is effective for most purposes and forms the backbone of Internet operations using IP addresses and routing tables, certain users or organizations prefer their data to travel more rapidly over paths under their direct control.
How does routing work in MPLS?
In conventional Internet routing, each router autonomously makes decisions based on its internal routing table. Even if two packets originate from the same source and are destined for the same endpoint, they might traverse different network paths if a router updates its routing table following the passage of the first packet. However, MPLS ensures that packets consistently follow the same route.
Within a network utilizing MPLS, every packet is categorized into a class known as a forwarding equivalence class (FEC). The possible network paths for packets are referred to as label-switched paths (LSP). The assignment of a packet to a particular path (LSP) is determined by its class (FEC). Packets sharing the same FEC follow identical LSPs.
Each packet is affixed with one or more labels, and these labels are encapsulated in an MPLS header, which is added atop all other headers attached to the packet. The labels associated with FECs are enumerated within the packet’s labels. Routers disregard the packet’s other headers and focus on the label, directing the packet to the appropriate LSP.
Due to MPLS-supporting routers only requiring visibility of the MPLS labels on a given packet, MPLS can function with nearly any protocol, hence the term “multiprotocol.” The format of the rest of the packet is inconsequential, as long as the router can interpret the MPLS labels at the packet’s forefront.
Is an MPLS network a ‘private’ network?
While MPLS can be termed “private” when specific paths are exclusively utilized by a single organization, it’s essential to note that MPLS itself doesn’t encrypt the transmitted data. In the event of intercepted packets along these paths, the information can be accessed. Conversely, a virtual private network (VPN) provides encryption, offering a means to genuinely secure network connections.
What Is MPLS Used For
Organizations frequently adopt this technology when managing multiple remote branch offices across the country or globally that require access to a data center or applications located at the organization’s headquarters or another branch. MPLS offers scalability, improved performance, and bandwidth, enhancing the user experience compared to traditional IP routing. However, it comes with a considerable cost, global delivery challenges, and a lack of carrier independence flexibility.
As organizations migrate their applications to the cloud, the traditional MPLS hub-and-spoke model becomes inefficient and expensive for the following reasons:
- It mandates routing traffic through the organization’s headquarters before reaching the cloud, rather than establishing a direct connection, significantly impacting performance.
- With the continual addition of applications, services, and mobile devices to networks, there is a growing demand for bandwidth and cloud expertise, resulting in escalated costs and increased operational complexity.
What are the drawbacks of MPLS?
- Cost: MPLS service is more expensive compared to regular Internet service.
- Extended setup time: The process of establishing intricate dedicated paths across one or more extensive networks is time-consuming. LSPs need manual configuration either by the MPLS vendor or the organization utilizing MPLS. This hinders organizations from rapidly expanding their networks.
- Absence of encryption: MPLS lacks inherent encryption; any unauthorized entity intercepting packets on MPLS paths can easily read them in plaintext. Encryption must be established as a separate measure.
- Cloud-related challenges: Organizations dependent on cloud services may face difficulties in establishing direct network connections to their cloud servers. This is because they lack access to the specific servers housing their data and applications.
How MPLS Networks Work for Cloud Adoption
MPLS networks were originally designed as an overlay strategy to simplify and enhance performance. However, effectively routing cloud traffic proves challenging with MPLS. To improve the efficiency of cloud traffic, many organizations are exploring ways to complement MPLS with other types of connections, such as:
- MPLS offloading: Through a direct-to-internet connection, an organization can redirect traffic initially destined for the web. This ensures that the MPLS circuit only carries traffic intended for headquarters. The challenge lies in addressing security for branch internet connections. An organization may need to add a full stack of security products at the branch, introducing complexity. Alternatively, it might route internet traffic through a proxy, which doesn’t offer the same level of security or inspect non-web traffic.
- MPLS replacement with direct-to-internet: Some organizations choose to completely replace an MPLS circuit with an internet connection at a branch office. While a direct connection improves efficiency for cloud access, it introduces challenges in setting up networking with the same connectivity and reliability as the MPLS environment and raises questions about how to implement security.
- Internet-augmented MPLS with SD-WAN: Using a software-defined wide area network (SD-WAN) allows organizations to enhance flexibility by supplementing MPLS with affordable broadband internet links or replacing it with the internet. This optimization assists in making branch networking decisions based on application, networking, and bandwidth requirements.
FAQ’s
How does MPLS differ from traditional Internet routing?
MPLS directs packets along predetermined paths, ensuring consistent routing, while traditional Internet routing relies on independent decisions made by each router based on its internal routing table.
What is the position of MPLS in the OSI layer?
MPLS is situated at OSI layer “2.5,” positioned below the network layer (layer 3) and above the data link layer (layer 2).
How does routing function in MPLS networks?
In MPLS networks, packets are assigned to forwarding equivalence classes (FECs), determining their label-switched paths (LSPs). Packets with the same FEC follow identical LSPs, as determined by their class. Routers focus on MPLS labels, providing flexibility with various protocols.
Is an MPLS network considered “private”?
While MPLS paths can be exclusive to an organization, it’s crucial to note that MPLS itself does not encrypt data. For enhanced security, a virtual private network (VPN) with encryption is recommended.
What are the drawbacks of MPLS networks?
Key drawbacks include the higher cost compared to regular Internet service, extended setup time due to manual configuration, lack of inherent encryption, and challenges in establishing direct network connections to cloud servers.
How does MPLS work for cloud adoption?
Organizations enhance cloud traffic efficiency by complementing MPLS with strategies such as MPLS offloading (direct-to-internet redirection), MPLS replacement with direct-to-internet, or Internet-augmented MPLS with SD-WAN for increased flexibility.
Conclusion
MPLS has significantly improved network performance and routing efficiency since its inception. Positioned at OSI layer “2.5,” it streamlines packet transmission along predetermined paths. Despite its benefits, MPLS comes with drawbacks, including cost and the absence of encryption. As organizations shift to the cloud, challenges arise, leading to the exploration of alternative strategies. Understanding MPLS nuances is essential for informed decisions in addressing evolving network needs.
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