When going through the process of choosing your next MPLS provider, carefully evaluate your true needs and what type of features you require for a productive, cost-effective network. We've written a number of articles on selecting an MPLS provider over the years and, while this article may not provide any new ground breaking advice, we hope the content serves as a good refresher in 2019.
What kind of network design do you need?
MPLS is capable of supporting different kinds of network topologies to give you the exact kind of connectivity you require. The two primary types of MPLS service include Layer 3 VPN and Layer 2 VPN. MPLS, whether of the L3VPN or L2VPN variety, creates an isolated network for your traffic within one or more service provider backbone networks.
L3VPN is what most people think of when the term “MPLS” is used without further qualification. With MPLS L3VPN, your business routers peer with the MPLS provider routers. This means the MPLS provider participates in making routing decisions for your network traffic. The default setup for an MPLS L3VPN is “any to any” connectivity, where any customer router can reach any other customer router within the VPN, and frequently the VPN is designed so that the providers core network is hidden so each router appears to be only a single hop away from any other router in the network.
L2VPN, by contrast, does not require participation in routing with the service provider. With L3VPN, your routers usually appear to be one hop away (with the carrier’s router being the “hop”), but with L2VPN your routers appear to be directly connected to each other. L2VPN is a good choice if you want to maintain complete control over the routing between your locations across the WAN.
Different network design topologies are available for both L3VPN and L2VPN. While “any to any” connectivity is the most common for both, point to multipoint (also known as hub and spoke) and direct point to point connections are also possible. In the case of L3VPN, multiple customer VPNs can also be connected together in specific ways. This is sometimes known as an extranet. When selecting your next MPLS provider, be sure to understand what kind of network design you need and if they offer solutions to match it. The provider should be able to help you understand if you’re not sure.
What features do you need?
One of the reasons businesses are keeping their MPLS connections even as they move to SD WAN is due to some of the features and guarantees available with a private MPLS link. The most common (and potentially most important) feature is Quality of Service (QoS). While SD WAN technologies can emulate some of the features of QoS, such as packet prioritisation, once traffic leaves your SD WAN edge device and is sent over the Internet, there is no QoS and therefore no guarantees about how your network traffic will be handled.
If you have applications that are sensitive to latency and jitter, a private MPLS link with QoS enabled makes a big difference in the quality of experience for your users, particularly if large geographic distances are involved. MPLS links are capable of true QoS features that are unavailable when using the Internet. Many SD WAN edge appliances, such as those offered by Cisco Meraki and Cisco Viptela, are capable of utilising the QoS features offered by an MPLS link.
Similarly, MPLS links are capable of supporting true multicast, unlike when traffic is sent over the Internet. Some SD WAN edge devices can simulate multicast, but this works by sending multiple copies of the multicast traffic which increases bandwidth utilisation, unlike true multicast where only a single copy of the traffic is sent.
Multicast and QoS are considered value-add services and usually incur an extra cost with MPLS connections. Likewise, different service level agreements (SLAs) can usually be purchased from your MPLS provider. When selecting an MPLS provider, be sure they offer the features you may need along with appropriate guarantees on service performance and availability.
What kinds of additional services are available?
When evaluating a new MPLS vendor, many offer other services to increase the value of the private connection and offload some functions for you as the consumer. One of the most common is offering Internet access either through the VPN itself (such as the MPLS vendor providing a default route to the Internet), or with a separate logical connection through the MPLS link (such as a separate VLAN).
Somewhat related, MPLS vendors can also offer security services in the form of a centralised firewall. With the proper network design in place, having the MPLS vendor provide security services can save you money on the upfront costs of purchasing firewalls. In particular, larger more-capable firewalls are very expensive and also require knowledgeable staff to operate them.
Similarly, many MPLS providers also offer voice services, whether completely hosted by the service provider, or simply offering SIP trunking services to your own internal Unified Communications systems. Just like with a centralised firewall design, having the MPLS provider host your communications services saves you on both upfront costs of hardware as well as staffing to design, operate and maintain the service.
The other additional service that continues to increase in popularity is direct interconnections to public cloud providers through the private MPLS service. As more businesses expand their private data centre workloads into public cloud offerings, having private high-performance connections into the public cloud provider can be advantageous compared to connecting over the public Internet. When selecting a new MPLS provider, inquire about any agreements they may have with different cloud services providers to see if private connections are available.
What are the risks and pitfalls of MPLS?
MPLS is a mature technology that has developed across more than two decades. During this time, new service offerings have become available, such as centralised voice and security. While the risks associated with using MPLS are minimal, the most common pitfall is the cost associated with the premium services offered. SD WAN over the Internet is usually less expensive than MPLS, but you have no control over your traffic. When selecting a new MPLS provider, determine what your requirements are and whether the provider will work with you to keep your costs in check for the additional services they are able to offer.