Abstract
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Today抯 communication networks and services are migrating to a converged paradigm centered on IP (Internet Protocol). MPLS (Multi-Protocol Label Switching) has emerged as a key enabling technology for this migration. MPLS technology has proven its value for delivering new services while at the same time allowing migration from old to new networks. The rollout of MPLS brings the challenges associated with any new networking technology ?validating proper conformance with industry standards prior to production deployment and verifying acceptable performance. This white paper provides an overview of MPLS, and Ixia抯 approach to testing and validating that technology.
Introduction
Several forces shape the current worldwide communications landscape. One is the general economic slowdown since early 2000, in particular, the pop of the telecommunications industry bubble. Another is the much-ballyhooed convergence of digital communications networks (voice, video, data) and the emergence of IP as the protocol of choice. Finally, globalization and deregulation have combined to level the playing field and increase competitive pressures.
The economic slowdown of recent years and resulting over-capacity in core networks has forced service providers and carriers to look seriously at their return on investment from network assets. With pure bandwidth becoming, in essence, a commodity, industry focus has shifted to supplying the value-add services customers need. As new technologies are adopted, the provider抯 ability to consolidate disparate existing networks is a key to deploying all services, old and new, profitably. The enterprise market has shown a similar response to the slowdown ?increasing efficiencies by pragmatically applying the new technologies that make such improvements possible.
Consequently, MPLS has great appeal for telecommunications providers. It can handle a variety of services, both legacy and new, over a single network. It enables higher-value applications and services to be delivered from the service provider抯 network, thereby reducing requirements on customer-premises equipment. Integration and consolidation speak loudly in today抯 business environment.
It抯 clear that the migration to MPLS is well under way. Every major carrier in the US, and many internationally, have deployed or announced plans for MPLS backbones. A 2003 study by Infonetics Research shows 62 percent of service providers are now engaged in some form of data network convergence over IP or IP/MPLS, with 86 percent doing so in 2004. Since legacy services, such as Frame Relay and ATM, can be carried over the MPLS network, this network convergence is often transparent to the end user enterprise. Moving forward, newer low cost services such as Ethernet will drive further adoption.
Beyond large carrier networks, MPLS is also finding its way into the larger enterprise networks of organizations such as retailers, investment companies, government agencies and the military, health care organizations, and technology enterprises.
What is MPLS?
Historical perspective
MPLS is based on the concept of label switching: an independent and unique 搇abel?is added to each data packet and this label is used to switch and route the packet through the network. The label is simple ?essentially a short hand version of the packet抯 header information ?so network equipment can be optimized around processing the label and forwarding traffic. This concept has been around the data communications industry for years. X.25, Frame Relay, and ATM are examples of label switching technologies.
Several label switching initiatives emerged in the mid-1990抯 to improve the performance of software-based IP routers and provide Quality of Service (QoS). Among these were IP Switching (Ipsilon/ Nokia), Tag Switching (Cisco), and ARIS (IBM). In early 1997, an Internet Engineering Task Force (IETF) Working Group was chartered to standardize a label switching technology. MPLS emerged from this effort as another labeling scheme, but one with this distinct advantage: it uses the same routing and host addressing schemes as IP ?the protocol of choice in today抯 networks. Today MPLS is defined by a set of IETF Request for Comments (RFCs) and draft specifications (under development).
MPLS and IP
It is important to understand the differences in the way MPLS and IP routing forward data across a network. Traditional IP packet forwarding uses the IP destination address in the packet抯 header to make an independent forwarding decision at each router in the network. These hop-by-hop decisions are based on network layer routing protocols, such as Open Shortest Path First (OPSF) or Border Gateway Protocol (BGP). These routing protocols are designed to find the shortest path through the network, and do not consider other factors, such as latency or traffic congestion.
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