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Why MPLS makes sense

Initially designed to bring the speed of Layer 2 switching to Layer 3 routers, it can also save an organization capital and improve overall network performance.


July 1, 2006  


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In today’s business environment, the network has become a critical tool to gain competitive advantages. With this in mind, we must always be diligent in finding ways to enhance and improve the enterprise network.

Although generally perceived as complex, Multiprotocol Label Switching (MPLS) actually serves to simplify the network, reduce costs and enable network convergence with greater control and resiliency for the enterprise.

Admittedly, it is not for every enterprise, but when implemented correctly it is a very powerful tool to support business demands within the network.

MPLS is a set of networking technologies and protocols used to enhance IP network efficiency and quality. It brings to packet-based IP networks the deterministic characteristics of circuit switching. It enables consolidation of disparate networks, delivers control through traffic segregation, and provides resiliency through fast re-route and traffic engineering.

Although initially designed to simply bring the speed of Layer 2 switching to Layer 3 routers, the pure speed benefit is no longer viewed as the main benefit of MPLS.

Traffic engineering

Instead, new benefits are seen like traffic engineering, with the ability to create virtual private networks (VPN) without the need for encryption or end-user devices, the ability to carry traditional Layer 2 traffic (such as Ethernet, Frame Relay or ATM) over IP and the ability to simplify the Wide Area Network (WAN).

MPLS is generally appropriate as a WAN and core networking technology. In a converged core or converged WAN, MPLS can provide virtualized networks to segment traffic based upon applications and user groups, provide differentiated and guaranteed qualities of service and provide security through virtual network separation.

In addition, through MPLS traffic engineering, MPLS can intelligently route around congestion in the core or WAN — a potential network bottleneck — and can be employed to reduce core and WAN bandwidth requirements and associated cost.

With traditional IP routing, some WAN links may be congested while others are under-utilized. MPLS allows the network administrator to map traffic across what would otherwise be under-utilized links and avoid the potential costly bandwidth upgrade requirements on shortest paths.

This mapping of traffic across selected paths can either be performed manually, or automated and performed dynamically with MPLS-based auto-bandwidth sensing capabilities.

Also, while many services being converged in the core may require real-time application performance, MPLS can meet these requirements with capabilities such as MPLS Fast Re-Route (FRR) and fast link and node error detection with Bidirectional Forwarding Detection (BFD).

Migrating the core or WAN to MPLS allows the enterprise to preserve the investments made at the edge of the MPLS network, while lowering cost and improving performance of a converged WAN or core network.

Given the ability of MPLS to support both Layer 2 and Layer 3 VPNs, networks and services such as ATM, Frame Relay and Voice can be folded into and converged with IP.

Their unique qualities of service and security requirements are supported within the core and WAN. Voice and video networks, as well as the LAN and data centre, do not have to change or upgrade to support the migration of MPLS — thus preserving the technology investment while providing the cost savings of a converged network that can support varied application performance and security requirements of the enterprise.

Considering the scale, cost and performance requirements of the large enterprise core and WAN, this portion of the network requires significant equipment and operational cost.

As a result, it is this very portion of the network that has the most to gain from the benefits of MPLS. It offers the large enterprise a significant return on investment in most applications based upon scale, performance requirements and the cost savings enabled by convergence, while enabling network performance to meet the requirements of the most demanding applications.

The benefits of MPLS for the WAN closely mirror the needs that today’s rapidly evolving business scene force on the corporate WAN. Business leaders need converged networks with advanced capabilities.

These include deterministic traffic for improved performance; configurable quality of service (QoS) on a granular application basis; low latency, jitter and packet loss to improve the performance of sensitive traffic; end-to-end transport resiliency; and manageability with scale.

As with any investment with the scale and overall impact of an MPLS there are some important considerations. First, will it be a private MPLS deployment or a public one?

Owning and managing a private WAN involves a great deal of management and required capital equipment, as well as additional operational cost to maintain the network. However, for some large enterprises it is justified based on the business model and cost structure of the organization.

If your organization has an outsourced public WAN and Internet access provided by one or more service providers, it can still reap the rewards of migrating to an MPLS-based WAN and continue to be served by its outsourced WAN.

Additionally, an enterprise can benefit from a hybrid of public and private MPLS networks if they have a mix of owned and managed campus networks and a public-outsourced WAN.

Perhaps the easiest way to migrate to MPLS is to take the following phased step approach. Most enterprises find the following six steps result in a smooth, optimal migration to MPLS.

1. Upgrade the IP network to MPLS, but continue to run it as an IP network. This step verifies network stability.

2. Build the MPLS network parallel to the IP network and expand the MPLS network to necessary locations where Frame Relay, ATM, or other networks exist today.

3. Configure the MPLS VPNs needed to migrate your network or networks to MPLS.

4. One-by-one, starting with the IP network, fold the existing networks into their respective MPLS VPNs.

5. If planning to traffic engineer portions of the network and configure MPLS-based features, such as Fast Re-Route (FRR), you should do this as the service(s) requiring traffic engineering and FRR are folded into the MPLS network.

6. Monitor and manage traffic loads based on applications, users and time of day requirements, and modify traffic engineering as appropriate to improve efficiencies of the network.

MPLS VPNs can segregate traffic based on departments, groups or users as well as by applications or any combination of user groups and applications.

Since each network being converged onto the newly built MPLS network has its own set of QoS, security and policy requirements, you will want to define MPLS-based VPNs that map to the legacy networks already built. Beyond that there are a few additional possible VPNs to consider.

Further consideration must be given to the applications running on the MPLS network. MPLS enables you to design and deploy your network with the support requirements of applications in mind. Specifically, multiple MPLS VPNs can be established over common service providers. Each MPLS-based VPN can be configured with the correct policy, security and network-based performance in mind to support a specific dedicated application or specific user community. Still further considerations are required for the migration from traditional routing protocols to those that work well with MPLS (such as EIRGP) compliance requirements and mapping of IP QoS from the LAN to MPLS QoS in order to ensure that “real-time” applications maintain the appropriate levels of priority. When considered for the planning purposes of an enterprise MPLS implementation, these considerations can ensure application-based performance over a converged network.

Deployment decisions

It should be clear how your MPLS deployment can better enable the
business, enhance operations within the organization to improve application performance while heightening security, and lowering operational cost of supporting the networking needs of the organization.

By conducting the business needs assessment from a department or user group perspective as well as by applications, geography, security, compliance and other relevant business factors, these business requirements can be instrumental in dictating the necessary deployment decisions for your MPLS network.

MPLS can be used to secure areas of the network and to consolidate policy with MPLS-based VPNs. In addition, it can be configured to support end-to-end QoS, Fast Re-Route and traffic engineering for application performance and optimal use of costly network links.

It’s the business drivers that will determine the choice of configurations and protocol implementations on the MPLS network to best meet the needs of an organization.

Where different groups provide management of applications, departments or geographies, the network can be virtualized to accommodate the organization’s network management structure on a cost effective converged network.

The many benefits of MPLS directly parallel the many considerations that must be made to accommodate the specific business needs of your organization.

Troy Herrera is the Segment Marketing Manager with Juniper Networks Inc.