The Multiprotocol Label Switching (MPLS) protocol has been the predominant means by which service providers and enterprises built wide area networks (WANs) over the past decade. The protocol sits between layers 2 and layers 3 and was designed to support multiple types of transports.
As with IP routing, the MPLS device at the edge of a network receives incoming packets and does a route lookup. But while IP routing works hop-by-hop with the route lookup determining the next router, MPLS determines complete path to the destination. The edge device appends this path to the packet so subsequent devices can forward packets without additional routing lookups.
MPLS is one type of data service that can be used by software-defined wide area networks (SD-WANs). Other types of data services that might be part of an SD-WAN include Internet access delivered across xDSL, cable or 4G. The SD-WAN is a mesh of encrypted tunnels across these underlying services, applying application routing and optimized path selection technologies to direct packets into the right tunnel. Once in that tunnel the underlying data services, such as MPLS, decides determines the path to the destination. (Visit this page for more information about SD-WAN operation.)
Initially, the primary benefit of MPLS came about because routing lookups was difficult to implement efficiently in software. By minimizing them, MPLS offered a significant reduction in latency. Improvements in silicon have largely eliminated lookup problem, but MPLS still brings three major benefits:
MPLS services reflect these benefits. Generally, MPLS services are highly available (99.99% is typical for a service level agreement (SLA) and actual network availability will often be higher) and engineered to deliver low packet loss (.1% is typical of SLAs). As such, MPLS is particularly well suited for carrying real-time applications, such a voice, and thin clients that require a highly responsive network.
The several limitations when comparing MPLS services against Internet services:
These limitations have given rise to SD-WANs. Visit this page to better understand how SD-WANs address the limitations of MPLS services.
MPLS provides business with a number of concrete benefits when compared with other private data services, such as leased lines. These include:
In addition to the above mentioned items, the following is a list of key technical features provided by any MPLS service:
The flexibility of MPLS has led to the development of four different types of services that may be provided by MPLS providers.
Pseudowire is an industry term for transport of any packet over an MPLS network. With a pseudowire, the packet are encapsulated in MPLS and the Label Distribution Protocol (LDP) is used as a signaling mechanism. Cisco calls this Any Transport over MPLS (AToM) and this is the building block of Layer 2 VPNs over MPLS.
Probably the most well know MPLS service, L3VPN is an IP based VPN. Virtual routing domains (VRFs) are built on CE-router. The VRFs contain customers route information and exchange routes with PE-router, usually using a protocol like BGP.
With VPWS, the MPLS provider delivers the virtual equivalent of a leased line, leaving the customer responsible for managing the IP routing. If there are disparate transport types, internetworking must be done at the provider edge (PE), translating between data transport types.
With VPLS, the provider delivers the equivalent of a LAN to the customer. VPLS is a layer-2 offering, using MAC addresses and layer-2 switching. Customer’s sites effectively are in one large Ethernet broadcast domain with any-any-connectivity. This provides a number of benefits:
The main advantage of VPLS is customer controls its own IP routing, letting the IT department be much more agile in responding to customer demands. VPLS networks allow you to rapidly reconfigure the network without having to contact and wait for your MPLS provider to act upon the request. Even if you do require a service provider change, the typical time to make network changes to Layer 2 VPLS networks is a fraction of layer-3 MPLS because network planning is much simpler, which could be crucial for some businesses.
Another feature which aids agility is the ease of adding new sites. With a VPLS-enabled network, a new site can be added by simply changing the network router that connects the site to the VPLS network. With layer-3 MPLS solutions, adding new sites is a much more complex process as all of the service provider’s routers need to be changed.
Companies with a VPLS-enabled wide area networks will be more smooth-running and thus should be able to provide a better level of service to their customers. This is down to the fact that with VPLS the company has access to its own network information so faults in a VPLS network can be isolated much faster and the IT department can troubleshoot to fix an urgent crisis rather than having to go through a number of support engineers to get the information required from a carrier. Less network down-time means higher corporate efficiency and productivity.
Another aspect of VPLS solutions is that they offer five levels of Quality of Service (QoS) and allow you to define your own priority levels either through labeling your traffic or using the service aware QoS feature on the core network. This is how VPLS maximizes efficient network usage according to your business needs, so you can rest assured that mission-critical data such as CRM, ERP and SCM are allocated enough bandwidth, alongside key services such as video conferencing and telephony, even during peak usage and without costly over provisioning of network capacity.
Companies that use VPLS solutions will find they have lower costs for a number of reasons. Firstly, VPLS enables convergence of services such as VoIP, video etc. so that all traffic can be delivered over a single Ethernet interface, eliminating multiple leased lines and resulting in economies of scale. Secondly, working with VPLS uses the same skills sets that LAN specialists have, so you would not need to provide additional training on WAN skills or hire WAN specialists. In addition, VPLS requires a lower cost CPE as it requires smaller and fewer routers than MPLS solutions.
As a switched, Layer 2 solution VPLS is zero-hop in the core of the network, so extremely low round-trip latencies and jitter can be achieved. For example sub 1 millisecond within a metropolitan area and 67 milliseconds round-trip from London to New York. This improves the productivity of the workforce as information is available faster. It also saves retail customers using Point-of-Sale systems time dialling up to make credit/debit card payments, improving their customers’ sales experience.
The point at which an interconnection between two different MPLS networks is made is referred to as an MPLS Exchange Point (MEP). A straightforward MEP would be at the customer premises.
Interconnecting MPLS networks requires subject matter expertise. Network professionals must understand MPLS internals, vendor-specific switch/router implementations and carrier-specific COS markings. Additionally, the enterprise must be willing to build MEPs at points where carrier MPLS networks come together—typically carrier-neutral collocation facilities, or pay for local loops to the enterprise facility. Unless you have the expertise in-house, it makes sense to outsource this configuration and management.
When you ask for an MPLS price quotation, you should understand that there are a wide variety of pricing models used by the different carriers. This makes it a bit more complicated to compare the carrier offerings, since with some pricing models, seemingly minor changes to your network, will change your monthly cost.
The different pricing models are as follows:
Understand that international MPLS prices may include a line item for “International Bandwidth” which reserves your contracted amount of bandwidth “across the pond” so to speak. By the same token, other carriers will bundle this charge amongst the other charges in their quotation.
As you can see, it takes some thought to analyze your MPLS price quotations.
For additional information about MPLS, check out the following: