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MPLS VPN Services: A Better Frame Relay
14 June 2001 Neil Rickard MPLS VPNs are a new technique for creating enterprise WANs, which will eventually replace frame relay as the dominant enterprise WAN technology. However, in the short term, enterprises must take care if they are to benefit.
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# MPLS VPN Services: A Better Frame Relay

MPLS VPNs are a new technique for creating enterprise WANs, which will eventually replace frame relay as the dominant enterprise WAN technology. However, in the short term, enterprises must take care if they are to benefit.

Bottom Line

Key Issue How will broadband networking (e.g., frame relay, ATM) evolve?

Strategic Planning Assumption By 2003, MPLS VPNs will have completely replaced frame relay for new WAN opportunities (0.7 probability).

MPLS Overview: Multiprotocol label switching (MPLS) is a generic networking technique that combines many of the desirable features of technologies such as asynchronous transfer mode (ATM) and frame relay with the features of IP. Standard routing schemes (e.g., BGP-4 and OSPF) are used to determine the topology of the network. This information is used to create tables of "labels" that identify destinations (ingress or egress ports) on the MPLS network. These labels can be simple additions to IP headers or can be other headers, such as ATM cell headers. At the ingress of an MPLS network, packets are inspected, their destination determined and the corresponding label attached. The packets are then switched through the network to the egress point, without further packet inspection, by a simple label-swapping scheme. This creates an end-to-end connection path similar to an ATM or frame relay virtual circuit. Its simplicity allows increased performance from the backbone provider routers (P router). Since 1999, MPLS has been used as a traffic management tool to allow Internet service providers (ISPs) to control the flows of traffic across their backbones more easily. During 2000, we saw the introduction of a new application for MPLS, the creation of virtual private networks (VPNs). In this application, a customer access router (which will often be operator-provided and managed) routes packets in the normal way, to a provider edge (PE) router. This device runs a routing table for each VPN customer connecting to that node. The table maps the enterprise's IP addressing into a unique set of labels for that enterprise, corresponding to the other virtual routers with which the enterprise needs to communicate. Thus, each enterprise's traffic is contained in its own set of label-switched paths, assuring privacy and allowing each enterprise to retain its own IP addressing scheme. The Internet Engineering Task Force (IETF) is the main standards body for MPLS and many of the basics are standardized. However, as is typical in the early phases of a technology, there are a wide variety of prestandard implementations or areas that are not yet fully standardized. For most enterprises that will be using managed MPLS services, there is little profit in wading through a multitude of MPLS options. Instead, enterprises should focus on the resulting functionality. For example, if an operator has implemented an initial MPLS network based on routers from one vendor, how will that affect its plans to upgrade its frame relay switches — bought from a different vendor — to MPLS? MPLS vs. Frame Relay and ATM Unlike frame relay, which must be partnered with ATM to obtain higher speeds, MPLS can be delivered over any speed of connection — from 64 kilobits per second and below, to gigabit Ethernet and above. Since the MPLS network is IP-aware, any-to-any connectivity is inherent and there is no need for the enterprise to deploy concentration routers to aggregate traffic from branch sites, as is often the case with large frame relay or ATM networks. Although MPLS quality of service is still being defined, most operators have implemented vendor-specific schemes, which give multiple service classes. The characteristics of these schemes are much better defined than frame relay's committed information rate and can deliver equivalent functionality to ATM service classes. MPLS vs. Encrypting/Tunneling VPNs The differences between MPLS and encrypting or tunneling-based VPNs, such as IP Security (IPsec), depends largely on the differences between the underlying networks. Most IPsec-based VPNs use the public Internet, or one operator's portion of it; most MPLS networks use a dedicated network, where the underlying addressing is not accessible from the Internet or by other enterprises sharing the network. In these circumstances, MPLS can provide security comparable to that achieved using frame relay, without needing encryption. This simplifies the equipment and the management burden. In a dedicated MPLS network, service levels can be higher, multiple service classes can be delivered and denial of service attacks should not be an issue. Internet backbones, even when managed by one operator, are vulnerable to traffic and routing disruption as well as hacking and denial of service attacks. MPLS Availability — Equipment In nearly all circumstances, the access router on the enterprise site is unaware it is connecting to an MPLS network. Thus, almost any IP access device can be deployed. Going forward, an MPLS user network interface should allow more-intelligent exchange of registration and quality of service information between the customer router and the MPLS PE node. MPLS traffic engineering (for P routers) is supported by many vendors; however, MPLS VPN (PE router) functionality is comparatively rare, with only a couple of router platforms supporting this functionality by 2Q01. During the second half of 2001, we expect that the majority of vendors of equipment for service providers will introduce MPLS VPN capabilities. Not only will routing products be upgraded to support MPLS VPNs, but upgrades will also be made available for many ATM and frame relay platforms. MPLS Availability — Services Most of the major international network operators servicing the enterprise market have either started delivering MPLS VPN services (e.g., Global One and Equant) or plan to do so during 2001. A growing number of national operators (e.g., France Telecom in France, British Telecommunications in the United Kingdom and AT&T and WorldCom in the United States) have also announced services. However, most of the networks currently in service are based on relatively small numbers of MPLS nodes. In some cases, traffic is even being carried across frame relay to and from the MPLS nodes, increasing the likelihood of high latency and congestion. Most operators plan significant expansion of their MPLS networks over the coming months and years; however, it will take at least two years for most of them to approach the size of their existing frame relay networks and the very process of expansion and upgrade increases the probability of service disruption. As with frame relay networks, competing MPLS VPN network operators will not directly interconnect their networks, at least through 2005 (0.7 probability). Gartner forecasts that MPLS pricing will be similar in structure to frame relay — based on port speed and connections charged by their bandwidth and quality of service. Although early MPLS pricing has varied widely, many operators are pricing MPLS around 10 percent to 15 percent less than frame relay as they try to attract customers to this new service. Enterprises with large networks can make further savings as MPLS VPNs will not need the "concentration" routers found in frame relay solutions. Finally, some operators are already using their MPLS networks as the basis for value-added IP services, such as managed Internet access, with firewalls, public voice over IP access, and IP centrex. We expect MPLS networks to be the dominant platform for such services. What Should Enterprises Do Now? Enterprises that are already locked into long-term frame relay and ATM contracts should be prepared to continue to extend their networks through 2005. If an enterprise's frame contracts come up for renewal or it is bidding for a new network through year-end 2001 and during 2002, it should consider both frame relay/ATM and MPLS offers, based on price and service levels. By 2003, MPLS VPNs will have completely replaced frame relay for new WAN opportunities (0.7 probability). Gartner continues to recommend the shortest duration of a contract an enterprise can tolerate for this type of network (typically two or three years). Frame relay proposals should have clauses to allow enterprises to migrate to MPLS during the contract, or to get MPLS pricing levels. Router prioritization features can be combined with frame relay to deliver comparable functionality to MPLS with multiple service classes. Enterprises should ask potential MPLS suppliers a number of critical questions (see Note 1). Because of the higher risk associated with a new technology, they should ensure they have a backup solution, independent of the MPLS network (such as ISDN dial around), for their critical applications.

Note 1 Questions to Ask MPLS VPN Service Providers 1. Is your network in service for production traffic? If so, do you have reference customers? 2. What is your current and planned network topology? Where are the nodes and links? 3. How is my traffic carried to and from the MPLS nodes? Does it pass over the frame relay network? 4. Is the MPLS backbone a dedicated network or part of a public network? If it is a public network, how is my traffic protected from disruption? 5. What access speeds and reliability options, such as ISDN backup, are available? 6. What service classes are offered and what are the service-level agreements and reports that go with them? 7. What value-added services are offered and planned? 8. What technology-migration options will be available? How can frame relay users migrate to MPLS?

Bottom Line MPLS VPNs will bring enterprises reduced WAN costs with additional functionality. However, through year-end 2001 and during 2002, enterprises should be cautious in their deployments, while the services mature. Equally, during this period, enterprises should avoid making long-term commitments to the services MPLS VPNs will replace, principally frame relay, but also ATM.

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