MPLS) Conformance and Performance Testing Whitepaper

Enabling a Converged World™

Multi-Protocol Label Switching (MPLS) Conformance and Performance Testing whitepaper

Multi-Protocol Label Switching (MPLS) Conformance and Performance Testing

example test plans included Contents

Abstract ...... 3 Introduction ...... 3 What is MPLS? ...... 4 Historical perspective ...... 4 MPLS and IP ...... 4 Advantages of MPLS ...... 4 How Does MPLS Work? ...... 5 MPLS routing ...... 5 Signaling and label distribution ...... 6 Data flow in an MPLS network ...... 7 How Is MPLS Used? ...... 8 Virtual Private Networks ...... 8 QoS/CoS ...... 11 Traffic engineering ...... 11 MPLS Challenges ...... 12 Why Test for MPLS Conformance? ...... 13 Why Test for MPLS Scalability and Performance? ...... 14 Scalability ...... 14 Performance ...... 14 Test Solution Requirements ...... 15 Optimized hardware platform ...... 15 Routing protocol emulation ...... 15 Signaling protocol emulation ...... 15 Traffic generation ...... 15 Automation ...... 15 Ixia’s Approach to MPLS Testing ...... 16 MPLS conformance testing...... 16 MPLS scalability and performance testing ...... 16 Conclusion ...... 18 Appendix: MPLS Testing Examples ...... 19 1. IxANVL LDP Conformance Test ...... 19 2. IxScriptMate L2 VPN Partial Mesh Performance Test ...... 21 3. IxScriptMate L3 VPN RSVP-TE Egress Performance ...... 22 4. IxExplorer LDP Extended Martini Session Scalability Test ...... 23 5. IxScriptMate VPLS MAC Address Cache Capacity Test ...... 25 6. IxExplorer RSVP-TE Fast Reroute Test ...... 27 Glossary ...... 28 Acknowledgements ...... 31

Copyright © 1998-2004 Ixia. All rights reserved. The information in this document is furnished for Ixia informational use only, is subject to change 26601 W. Agoura Road without notice, and should not be construed as a commitment by Ixia. Ixia assumes no Calabasas, CA 91302 responsibility or liability for any errors or Phone: (818) 871-1800 inaccuracies that may appear in this document. Ixia and the Ixia logo are trademarks of Ixia. All Fax: (818) 871-1805 other companies, product names, and logos are Email: [email protected] trademarks or registered trademarks of their respective holders. Internet: www.ixiacom.com

Abstract Today’s communication networks and networks. The rollout of MPLS brings the services are migrating to a converged challenges associated with any new paradigm centered on IP (Internet networking technology — validating proper Protocol). MPLS (Multi-Protocol Label conformance with industry standards prior Switching) has emerged as a key enabling to production deployment and verifying technology for this migration. MPLS acceptable performance. This white paper technology has proven its value for provides an overview of MPLS, and Ixia’s delivering new services while at the same approach to testing and validating that time allowing migration from old to new technology.

Introduction Several forces shape the current handle a variety of services, both legacy worldwide communications landscape. and new, over a single network. It enables One is the general economic slowdown higher-value applications and services to since early 2000, in particular, the pop of be delivered from the service provider’s the telecommunications industry bubble. network, thereby reducing requirements Another is the much-ballyhooed on customer-premises equipment. convergence of digital communications Integration and consolidation speak loudly networks (voice, video, data) and the in today’s business environment. emergence of IP as the protocol of choice. It’s clear that the migration to MPLS is well Finally, globalization and deregulation under way. Every major carrier in the US, have combined to level the playing field and many internationally, have deployed or and increase competitive pressures. announced plans for MPLS backbones. A The economic slowdown of recent years 2003 study by Infonetics Research shows and resulting over-capacity in core 62 percent of service providers are now networks has forced service providers and engaged in some form of data network carriers to look seriously at their return on convergence over IP or IP/MPLS, with 86 investment from network assets. With pure percent doing so in 2004. Since legacy bandwidth becoming, in essence, a services, such as Frame Relay and ATM, commodity, industry focus has shifted to can be carried over the MPLS network, this supplying the value-add services network convergence is often transparent customers need. As new technologies are to the end user enterprise. Moving forward, adopted, the provider’s ability to newer low cost services such as Ethernet consolidate disparate existing networks is will drive further adoption. a key to deploying all services, old and Beyond large carrier networks, MPLS is new, profitably. The enterprise market has also finding its way into the larger shown a similar response to the slowdown enterprise networks of organizations such — increasing efficiencies by pragmatically as retailers, investment companies, applying the new technologies that make government agencies and the military, such improvements possible. health care organizations, and technology Consequently, MPLS has great appeal for enterprises. telecommunications providers. It can

MPLS: Conformance and Performance Testing Copyright © 2004, Ixia 3 What is MPLS? Historical perspective consider other factors, such as latency or traffic congestion. MPLS is based on the concept of label switching: an independent and unique MPLS creates a connection-based model “label” is added to each data packet and overlaid onto the traditionally this label is used to switch and route the connectionless framework of IP routed packet through the network. The label is networks. This connection-oriented simple — essentially a short hand version architecture opens the door to a wealth of of the packet’s header information — so new possibilities for managing traffic on an network equipment can be optimized IP network. MPLS builds on IP, combining around processing the label and the intelligence of routing, which is forwarding traffic. This concept has been fundamental to the operation of the around the data communications industry Internet and today’s IP networks, with the for years. X.25, Frame Relay, and ATM are high performance of switching. Beyond its examples of label switching technologies. applicability to IP networking, MPLS is being expanded for more general Several label switching initiatives emerged applications in the form of Generalized in the mid-1990’s to improve the MPLS (GMPLS), with applications in optical performance of software-based IP routers and Time-Division Multiplexing (TDM) and provide Quality of Service (QoS). networks. Among these were IP Switching (Ipsilon/ Nokia), Tag Switching (Cisco), and ARIS Advantages of MPLS (IBM). In early 1997, an Internet • MPLS enables a single converged Engineering Task Force (IETF) Working network to support both new and Group was chartered to standardize a label legacy services, creating an efficient switching technology. MPLS emerged from migration path to an IP-based this effort as another labeling scheme, but infrastructure. MPLS operates over one with this distinct advantage: it uses both legacy (DS3, SONET) and new the same routing and host addressing infrastructure (10/100/1000/10G schemes as IP — the protocol of choice in Ethernet) and networks (IP, ATM, today’s networks. Today MPLS is defined Frame Relay, Ethernet, and TDM). by a set of IETF Request for Comments • MPLS enables traffic engineering. (RFCs) and draft specifications (under Explicit traffic routing and engineering development). help squeeze more data into available MPLS and IP bandwidth. It is important to understand the • MPLS supports the delivery of services differences in the way MPLS and IP routing with Quality of Service (QoS) forward data across a network. Traditional guarantees. Packets can be marked IP packet forwarding uses the IP for high quality, enabling providers to destination address in the packet’s header maintain a specified low end-to-end to make an independent forwarding latency for voice and video. decision at each router in the network. • MPLS reduces router processing These hop-by-hop decisions are based on requirements, since routers simply network layer routing protocols, such as forward packets based on fixed labels. Open Shortest Path First (OPSF) or Border • MPLS provides the appropriate level of Gateway Protocol (BGP). These routing security to make IP as secure as protocols are designed to find the shortest Frame Relay in the WAN, while path through the network, and do not reducing the need for encryption on public IP networks.

4 Copyright © 2004, Ixia MPLS: Conformance and Performance Testing • MPLS VPNs scale better than configuration and management customer-based VPNs since they are requirements for the customer. provider-network-based, reducing the

How Does MPLS MPLS is a technology used for optimizing establish the network topology. MPLS is Work? traffic forwarding through a network. then overlaid on top of this topology. MPLS Though MPLS can be applied in many predetermines the path data takes across different network environments, this a network and encodes that information discussion will focus primarily on MPLS in into a label that the network’s routers IP packet networks — by far the most understand. This is the connection- common application of MPLS today. oriented approach previously discussed. Since route planning occurs ahead of time MPLS assigns labels to packets for and at the edge of the network (where the transport across a network. The labels are customer and service provider network contained in an MPLS header inserted into meet), MPLS-labeled data requires less the data packet (Figure 1). router horsepower to traverse the core of These short, fixed-length labels carry the the service provider's network. information that tells each switching node MPLS routing (router) how to process and forward the packets, from source to destination. They MPLS networks establish Label-Switched have significance only on a local node-to- Paths (LSPs) for data crossing the network. node connection. As each node forwards An LSP is defined by a sequence of labels the packet, it swaps the current label for assigned to nodes on the packet’s path the appropriate label to route the packet to from source to destination. LSPs direct the next node. This mechanism enables packets in one of two ways: hop-by-hop very-high-speed switching of the packets routing or explicit routing. through the core MPLS network. Hop-by-hop routing. In hop-by-hop routing, MPLS combines the best of both Layer 3 IP each MPLS router independently selects routing and Layer 2 switching. In fact, it is the next hop for a given Forwarding sometimes called a “Layer 2½” protocol. Equivalency Class (FEC). A FEC describes a While routers require network-level group of packets of the same type; all intelligence to determine where to send packets assigned to a FEC receive the traffic, switches only send data to the next same routing treatment. FECs can be hop, and so are inherently simpler, faster, based on an IP address route or the and less costly. MPLS relies on traditional service requirements for a packet, such as IP routing protocols to advertise and low latency.

Figure 1. MPLS header format on an MPLS packet.

MPLS: Conformance and Performance Testing Copyright © 2004, Ixia 5 In the case of hop-by-hop routing, MPLS The most commonly used MPLS signaling uses the network topology information protocol is LDP. LDP defines a set of distributed by traditional Interior Gateway procedures used by MPLS routers to Protocols (IGPs) — routing protocols such exchange label and stream mapping as OSPF or IS-IS. This process is similar to information. It is used to establish LSPs, traditional routing in IP networks, and the mapping routing information directly to LSPs follow the routes the IGPs dictate. Layer 2 switched paths. It is also commonly used to signal at the edge of the Explicit routing. In explicit routing, the entire MPLS network — the critical point where list of nodes traversed by the LSP is non-MPLS traffic enters. Such signaling is specified in advance. The path specified required when establishing MPLS VPNs, could be optimal or not, but is based on for example. the overall view of the network topology and, potentially, on additional constraints. RSVP-TE is also used for label distribution, This is called Constraint-Based Routing. most commonly in the core of networks Along the path, resources may be reserved that require traffic engineering and QoS. A to ensure QoS. This permits traffic set of extensions to the original RSVP engineering to be deployed in the network protocol, RSVP-TE provides additional to optimize use of bandwidth. functionality beyond label distribution, such as explicit LSP routing, dynamic Label Information Base. As the network is rerouting around network failures, established and signaled, each MPLS preemption of LSPs, and loop detection. router builds a Label Information Base RSVP-TE can distribute traffic engineering (LIB)—a table that specifies how to forward parameters such as bandwidth a packet. This table associates each label reservations and QoS requirements. with its corresponding FEC and the outbound port to forward the packet to. Multi-protocol extensions have been This LIB is typically established in addition defined for BGP, enabling the protocol to to the routing table and Forwarding also be used to distribute MPLS labels. Information Base (FIB) that traditional MPLS labels are piggybacked onto the routers maintain. same BGP messages used to distribute the associated routes. Signaling and label distribution MPLS allows multiple labels (called a label Connections are signaled and labels are stack) to be carried on a packet. Label distributed among nodes in an MPLS stacking enables MPLS nodes to network using one of several signaling differentiate between types of data flows, protocols, including Label Distribution and to set up and distribute LSPs Protocol (LDP) and Resource reSerVation accordingly. A common use of label Protocol with Tunneling Extensions (RSVP- stacking is for establishing tunnels through TE). Alternatively, label assignment can be MPLS networks for VPN applications. piggybacked onto existing IP routing protocols such as BGP.

6 Copyright © 2004, Ixia MPLS: Conformance and Performance Testing Figure 2. MPLS network. Data flow in an MPLS network establish LSPs through the MPLS network to remote PE routers. Figure 2 shows a typical MPLS network and its associated elements. The central 2. Non-MPLS traffic (Frame Relay, ATM, cloud represents the MPLS network itself. Ethernet, etc.) is sent from a All data traffic within this cloud is MPLS- customer network, through its CE labeled. All traffic between the cloud and router, to the ingress PE router the customer networks is not MPLS- operating at the edge of the labeled (IP for example). The customer- provider’s MPLS network. owned Customer Edge (CE) routers 3. The PE router performs a lookup on interface with the Provider Edge (PE) information in the packet to routers (also called Label Edge Routers, or associate it with a FEC, then adds LERs) owned by the service provider. At the the appropriate MPLS label(s) to the ingress (incoming) side of the MPLS packet. network, PE routers add MPLS labels to 4. The packet proceeds along its LSP, packets. At the egress (outgoing) side of with each intermediary P router the MPLS network, the PE routers remove swapping labels as specified by the the labels. Within the MPLS cloud, P information in its LIB to direct the (Provider) routers (also called Label packet to the next hop. Switching Routers, or LSRs), switch traffic 5. At the egress PE, the last MPLS label hop-by-hop based on the MPLS labels. is removed and the packet is To demonstrate an MPLS network in forwarded by traditional routing operation, we will follow the flow of data mechanisms. through the network in Figure 2: 6. The packet proceeds to the 1. Before traffic is forwarded on the destination CE and into the MPLS network, the PE routers first customer’s network.

MPLS: Conformance and Performance Testing Copyright © 2004, Ixia 7 How Is MPLS Used? One of the primary original goals of MPLS, scalability compared with other VPN boosting the performance of software- technologies. MPLS VPNs keep different based IP routers, has been superseded as customers’ traffic separated by uniquely advances in silicon technology have identifying each VPN flow and setting up enabled line-rate routing performance circuit-like connections. This mechanism implemented in router hardware. In the provides traffic separation and is meantime, additional benefits of MPLS transparent to end users within the VPN have been realized, notably VPN services group. MPLS VPNs provide security and traffic engineering. inherently, essentially making IP as secure as Frame Relay or ATM, and reducing the Virtual Private Networks need for encryption. Miercom, an A Virtual Private Network (VPN) is a private independent network consultancy and network service delivered over a public testing laboratory, tested MPLS VPN (shared) network. VPNs benefit end security on a network of various routers, customers by allowing remote locations to and concluded (2001): “Our test results be securely connected over a public have demonstrated that MPLS-based VPN network, without the expense of buying or networks offer the same level of security leasing dedicated network lines. MPLS as Frame Relay or ATM.” enables VPNs by providing a circuit-like, L3 VPNs. MPLS VPNs fall into two broad connection-oriented framework, allowing classes — those that operate at Layer 3 carriers to deploy VPNs over the and those that operate at Layer 2. Layer 3 traditionally connectionless IP network VPNs were first to be investigated and infrastructure. standardized in RFCs. Layer 3 VPNs based MPLS VPNs vs. IPSec VPNs. The term VPN can on RFC 2547bis have seen the most be confusing, as it is used to describe a widespread deployment to date. number of technologies. VPNs can be RFC 2547bis-based Layer 3 VPNs use organized into two broad categories: extensions to BGP, specifically Multi- • Customer-based: the VPN is Protocol internal BGP (MP-iBGP), to configured exclusively on customer- distribute VPN routing information across located equipment and uses tunneling the provider backbone. Standard MPLS protocols across the public network, mechanisms (as previously discussed) are most commonly IPSec. used to forward the VPN traffic across the • Network-based: the VPN is configured backbone. In an L3 VPN, the CE and PE on service provider equipment and routers are IP routing peers. The CE router managed by the provider. MPLS VPNs provides the PE router with the routing are an example of network-based VPNs. information for the customer’s private IPSec adds secure encryption capabilities network behind it. The PE router stores this to IP. It is typically managed by the end private routing information in a Virtual customer, outside of a service provider’s Routing and Forwarding (VRF) table; each network, where there is a higher degree of VRF is essentially a private IP network. The exposure to breaches of data privacy. PE router maintains a separate VRF table IPSec is especially useful for securing for each VPN, thereby providing remote location VPN connections back to appropriate isolation and security. VPN the corporate network. users have access only to sites or hosts within the same VPN. In addition to the MPLS VPNs are maintained on the service VRF tables, the PE router also stores the provider’s equipment, which can provide normal routing information it needs to significant cost savings and increased send traffic over the public Internet.

8 Copyright © 2004, Ixia MPLS: Conformance and Performance Testing Figure 3. Layer 3 VPN MPLS network. L3 VPNs use a two-level MPLS label stack tables that are larger than normal with the (see Figure 3). The inner label carries VPN- addition of the VPN routes. specific information from PE to PE. The L2 VPNs. Layer 2 MPLS VPNs have recently outer label carries the hop-by-hop MPLS generated much interest from carriers and forwarding information. The P routers in vendors and are beginning to be deployed the MPLS network only read and swap the (2003). Layer 2 MPLS VPN standards are outer label as the packet passes through still in the development phase, but the the network. They do not read or act upon industry has centralized on the IETF the inner VPN label — that information is Martini drafts, named after primary author tunneled across the network. Luca Martini. These drafts define a The L3 VPN approach has several method for setting up L2 VPN tunnels advantages. The customer IP address across an MPLS network that can handle space is managed by the carrier, all types of Layer 2 traffic, including significantly simplifying the customer IT Ethernet, Frame Relay, ATM, TDM, and role — as new customer VPN sites are PPP/HDLC. easily connected and managed by the There are two kinds of Layer 2 VPNs that provider. L3 VPNs also have the advantage use the Martini methodology: of supporting auto-discovery by leveraging the dynamic routing capabilities of BGP to • Point-to-point: similar to ATM and distribute VPN routes. Frame Relay using fixed, point-to-point connections (LSPs) across the The Layer 3 approach has disadvantages network. as well. Layer 3 VPNs support only IP or • Multi-point: supporting meshed and “IP-encapsulated” customer traffic. Scaling hierarchical topologies. also can be a significant issue with PE routers required to support BGP routing

MPLS: Conformance and Performance Testing Copyright © 2004, Ixia 9 Figure 4. Layer 2 VPN MPLS network. VPLS (Virtual Private LAN Services) is a The inner Virtual Circuit (VC) label multi-point L2 VPN model that has identifies the VLAN, VPN, or connection at generated significant interest of late. VPLS the end point. In addition, there is an uses Ethernet as the access technology optional Control Word following the VC between the customer and the provider label that carries information about the network and enables a private corporate enclosed Layer 2 packet. Ethernet network to be extended over a Layer 2 MPLS VPNs have the distinct provider-managed MPLS infrastructure. advantage of being able to transport any Multiple corporate customer sites can be enterprise protocol — whatever is being connected together with all locations carried is transparent to the MPLS appearing to be on the same Layer 3 network. They can also run over nearly any network, all without the complexity of transport medium, including ATM, Frame configuring Layer 3 routers. Relay, Packet over SONET, and Ethernet, In Layer 2 VPNs, the PE and CE routers enabling the integration of connectionless need not be routing peers as required in IP networks with connection-oriented Layer 3 VPNs. Instead, only a Layer 2 networks. End customer expertise is connection needs to exist between PE and minimal since no routing configuration is CE, with the PE routers simply switching required. incoming traffic into tunnels configured to On the downside, L2 VPNs may not scale one or more other PE routers. A Layer 2 as well as L3 VPNs. A full mesh of LSPs MPLS VPN determines reachability through must be set up between all L2 VPN sites, a the data plane by using address learning, requirement that does not scale well with in contrast with Layer 3 VPNs, which large numbers of sites. In addition, they determine reachability through the control cannot take advantage of automatic route plane by exchanging BGP routes. discovery available with L3 VPNs, and so L2 VPNs use label stacking similar to Layer are better suited to situations with a 3 VPNs. The outer tunnel label determines smaller number of VPN sites and static the hop-by-hop path through the network. routes.

10 Copyright © 2004, Ixia MPLS: Conformance and Performance Testing QoS/CoS While IntServ offers traffic bandwidth guarantees, it has proved to be not very One of the key shortcomings of IP-based scalable or practical to operate across networks, compared with Frame Relay and large networks. The DiffServ architecture, ATM networks, has been their inability to on the other hand, is a scalable provide service guarantees for traffic. For alternative, but does not provide example, real-time traffic such as voice or guarantees. Recent work in the IETF has video needs high quality service (low focused on combining DiffServ and MPLS latency, low jitter, etc.) to successfully traffic engineering elements to provide traverse a network. Similarly, mission- QoS guarantees in MPLS packet networks. critical data, such as e-commerce The DiffServ information in IP packet transactions, must have priority over headers is mapped into the label normal web browser traffic. information of the MPLS packets. MPLS MPLS’s connection-oriented nature routers act upon the prioritization provides the framework necessary to give information in the packets to forward the quality guarantees to IP traffic. While QoS data appropriately. Some of the and Class of Service (CoS) are not mechanisms used include traffic shaping, fundamental features of MPLS, they can queuing, and packet classification. be applied in MPLS networks where traffic QoS is typically implemented at the edge of engineering is used. This enables the MPLS cloud, where non-labeled traffic providers to establish Service Level from the customer network enters the Agreements (SLAs) with customers to carrier network. At this entry point for guarantee service aspects such as example, delay-sensitive real-time traffic, network bandwidth, delay, and jitter. Value- such as IP voice or video conferencing added services can be delivered in traffic, can be prioritized for delivery over addition to basic data transport, increasing bulk data transmissions. revenue propositions and ultimately enabling the move to converged networks. Traffic engineering IntServ and DiffServ. Several mechanisms Another key shortcoming of IP, especially in have developed over time to establish public networks, is its inability to optimize QoS/CoS within a network. In the IntServ network resource utilization. Using (Integrated Services) model, RSVP was standard IP routing, all traffic between two developed to signal QoS requirements points is sent over the shortest path even across a network, allowing devices to though multiple paths may exist. During negotiate and establish guaranteed traffic periods of high traffic volume, this can parameters such as bandwidth and result in traffic congestion on certain latency end-to-end. It uses hard allocation routes while alternative routes are of resources, guaranteeing services down underused. This is known as the hyper- to a per-flow basis. The DiffServ aggregation problem (Figure 5). (Differentiated Services) model is less Rather than adding bandwidth to handle stringent, providing for CoS delivery by traffic volume increases, MPLS traffic classifying traffic into relative priority levels engineering uses existing bandwidth more for aggregate treatment, but without efficiently by allowing packets to be routed signaling or end-to-end guarantees of along explicit routes and with specific service. DiffServ redefines the Type of bandwidth guarantees. Service (TOS) field in the IP packet header to provide this classification.

MPLS: Conformance and Performance Testing Copyright © 2004, Ixia 11 Figure 5. Hyper-aggregation in conventional IP networks. This is known as Constraint-Based Routing such as link bandwidth, link utilization, and is the key to MPLS traffic engineering. delay, priority, preemption, etc. — to allow Constraint-Based Routing manages traffic the network to utilize paths that meet paths within an MPLS network, allowing service requirements, resource availability, traffic to be steered to desired paths. load balancing, and failure recovery objectives. RSVP-TE is widely used for MPLS traffic engineering also enables MPLS signaling in networks that require resiliency and reliability to be built into traffic engineering. carrier networks, increasing the availability and value of the network to their MPLS traffic engineering is typically customers. Using MPLS traffic deployed in the core of the MPLS network, engineering, LSP connections can be while QoS is used at the edge. QoS at the optimized and preempted. When outages edge ensures that high priority packets get occur, traffic can be actively rerouted preferential treatment, while traffic around failed links. An example of this is engineering avoids network congestion RSVP-TE Fast Reroute, which provides for and appropriately utilizes available sub-50ms switchovers between primary bandwidth resources. Together, QoS and and back up LSPs or LSP bundles. traffic engineering enable organizations to move away from multiple, specialized Traffic engineering is deployed in MPLS networks for voice, video, and data to a networks via traffic engineering extensions single converged IP/MPLS network, to IGPs, such as OSPF and IS-IS. OSPF-TE dramatically reducing overhead and cost. and IS-IS-TE carry additional information —

MPLS Challenges MPLS has made significant progress over continually evolving state and its impact on the last few years and is well into network performance and scalability. mainstream deployment in networks MPLS is not a standalone technology — it is around the world. But key challenges to overlaid on Layer 2 technologies such as attaining more widespread acceptance Ethernet or ATM, and must operate in remain. MPLS encompasses a wide range conjunction with other control plane of functionality and applications, therefore protocols, such as IP routing. The its implementation has an associated high complexity of MPLS deployments is level of complexity. Vendors who develop increased because of this interaction. In MPLS technology, as well as organizations some cases, four or more protocols may be looking at deploying MPLS in a network involved in a given network scenario, today, must also factor in MPLS’s necessitating careful coordination and

12 Copyright © 2004, Ixia MPLS: Conformance and Performance Testing validation of the end-to-end system. have vastly improved the raw performance Integration of legacy services and of today’s routers, the complexity of MPLS deployment of new services, such as VPNs, in real network applications presents requires tunneling, which in turn increases performance and scalability issues. The the setup requirements for a given circuit. challenge is typically not in the MPLS core network, where data is simply being label- Though under development for a number switched, but at the network edge where of years, MPLS continues to evolve rapidly. MPLS must integrate with non-MPLS The primary goals of the technology have networks, and where services are initiated. shifted over time as technology has As networks converge, traffic loads progressed. Today, a number of extensions increase and networks must be able to to the MPLS protocols, as well as new deal with the overhead of handling real- functionality, are under development. New time and prioritized traffic. The meshed developments often obsolete older ones. connections required for VPN deployments This dynamic nature presents a moving can quickly challenge equipment target to those developing and deploying scalability limitations, as well as MPLS. Vendors must decide whether to provisioning and management implement a new feature with an eye on requirements. Large service provider the industry’s current direction. Service networks have the ultimate scalability providers gauge the viability of new challenge and must consider the developments by asking whether they limitations of their equipment as they look solve a given problem better. On certain to maximize return on investment. issues, the industry has split into multiple camps, further complicating the situation The challenges presented by MPLS as organizations trade off the long term ultimately necessitate thorough testing risk of obsolescence with the shorter term and validation of MPLS systems during benefits of implementing a certain development and prior to deployment. technology. Interoperability of MPLS MPLS is by no means a plug-and-play equipment in heterogeneous networks proposition. Performing appropriate due remains an issue and will continue to be diligence is the only way to ensure success so for several years to come. when dealing with a broad-scope and rapidly evolving technology such as MPLS. Though advances in silicon technology

Why Test for MPLS MPLS standards and implementations are remain competitive in their market and to Conformance? dynamic. At the time of this writing, there meet the demands of their customers. were over 100 IETF drafts associated with Development test and quality assurance MPLS, and over 20 RFCs. In such a groups therefore need an efficient way to dynamic environment, standards verify the correctness of their compliance and the corresponding implementations. Formalized conformance expectation of equipment interoperability testing against standards supplies this present significant challenges. confidence. Beyond ensuring product interoperability and quality, conformance Equipment vendors find themselves at the testing can also accelerate product leading edge of these challenges as they development by detecting bugs or continually update their feature sets to the correcting design issues early in the latest standards and options, while at the development cycle, thereby reducing the same time improving performance and product’s time to market and hence scalability. They must do this, both to increasing profitability.

MPLS: Conformance and Performance Testing Copyright © 2004, Ixia 13 For both service providers and enterprise To achieve adequate test coverage for organizations, multi-vendor environments compliance with a standard, hundreds of are the reality today. Such a reality is conformance test cases are typically untenable without equipment necessary to cover a given protocol, and interoperability driven by standards-based these tests must be appropriately updated implementations. Networks are also as necessary. Since test cycles are often dynamic, so when it comes time to very frequent (daily in some cases), these upgrade, conformance and regression tests must be automated as well. To testing are crucial to ensure that new address these challenges, most vendors software releases do not break existing and service providers rely on conformance services. testing products that are maintained and supported by a dedicated third-party.

Why Test for MPLS After verifying the standards compliance RSVP-TE must be verified to determine Scalability and and interoperability of an MPLS system, the number of protocol sessions that Performance? the next challenge is to determine the can be sustained. ability of an implementation to perform in Together, these numbers will determine a real network. Given the complexity of the the quantity of routers that must be protocols involved and the multi-layered deployed for a given number of customers. nature of MPLS, scalability and performance are often genuine concerns. Performance Equipment vendors typically test and One of the original proposed benefits of publish the scalability and performance MPLS was the performance boost capabilities of their products. End users associated with switching on a label as will often validate the numbers while opposed to routing on an IP address. While additionally testing specific network this is of less concern today, the forwarding scenarios unique to their deployment. performance of PE routers at the edge of Scalability the MPLS network still involves IP (or other) lookups and assignments. Vendors Scalability is typically viewed as the biggest and service providers alike must test and challenge in service providers’ MPLS characterize MPLS devices across multiple networks today. They must understand the interface types (Ethernet, POS, ATM) for dynamics of growth in their networks as traditional data plane performance new customers are added, as well as the metrics: ultimate limits of their networks. Several metrics are key in determining scalability: •Data throughput • Router capacity: The capacity of the •Packet loss MPLS routers to handle large numbers •Latency of LSPs, VPN instances (VRFs or VCs), •Jitter and routes is important to determine Given the advances in hardware-based when sizing the overall network. routing in recent years, the expectations • LSP setup rate: The rate at which LSPs for device performance have grown so that can be set up is an important factor in line rate traffic support is typically a given. overall network responsiveness. But the MPLS routers of today are being • Signaling protocol scalability: The asked to perform many functions, with limits of an MPLS router running operational requirements at the data signaling protocols such as LDP or (traffic), control (routing), security, and

14 Copyright © 2004, Ixia MPLS: Conformance and Performance Testing management planes. With requirements Together, scalability and performance for MPLS routers to run multiple protocols metrics can be competitive differentiators simultaneously, to interoperate among for equipment vendors. For service multiple technologies, and to apply QoS providers and network managers, they are and other policies to traffic, the reality is a key selection criteria between vendors. that full performance is not a given. Characterizing these elements is critical, Performance must be viewed in different since they directly impact the service usage scenarios, depending on how the quality that can be delivered to the end network is designed and being operated. customer.

Test Solution MPLS test tools must be able to perform a extensions to these protocols, for example Requirements wide variety of functions to test and OSPF-TE and IS-IS-TE, must be supported validate MPLS devices and systems to allow this aspect of MPLS to be tested. adequately. For conformance testing, the Signaling protocol emulation test solution must be able to fully exercise the control plane of the device or system MPLS signaling protocols must be under test. For performance and scalability supported to establish MPLS tunnels and testing, the test solution must be able to signal L2 and L3 VPNs. Examples of these emulate MPLS routers at the control plane protocols include LDP, RSVP-TE, and MP- level and scale up for large capacity BGP. The test tool must be able to run testing. And it must be able to drive traffic these protocols simultaneously with the through the system at the data plane level routing protocols on the same network to fully stress the device being tested. interface. Optimized hardware platform Traffic generation While simple router emulations can be run Once the MPLS network has been on PCs or workstations, an optimized test established and all connections signaled, system must be employed to provide the test tool must be able to inject data complete testing capabilities and high traffic into the network topology, at speeds levels of scalability. For example, to up to line rate, and it must be able to emulate a large network, a network receive traffic as well. This means sending interface on a test tool must support traffic over all of the LSPs configured on hundreds or even thousands of IP the test interfaces. On the receiving side, interfaces and MAC addresses— the test tool must be able to gather requirements that standard off-the-shelf statistics and capture the traffic for hardware cannot support. Purpose-built analysis. An increasingly common test hardware is required to provide the requirement for test tools is to emulate flexibility and scalability needed to real enterprise applications over the adequately test MPLS equipment. network. This allows for the characterization of the network in terms Routing protocol emulation the end user really cares about, namely, The test solution must be able to emulate how their applications will perform. the full range of routing protocols used in Automation today’s networks, including OSPF, IS-IS, RIP, and BGP. These routing protocols are Since MPLS testing involves complex setup used to advertise the underlying network and analysis requirements, tests must be topologies over which the MPLS network is repeatable, which makes automation very established. In addition, traffic engineering important. Scripting languages are

MPLS: Conformance and Performance Testing Copyright © 2004, Ixia 15 normally used to provide automation in environments to perform repeatable MPLS router testing. These tools enable regression tests necessary to ensure quality assurance and manufacturing product functionality and quality.

Ixia’s Approach to MPLS conformance testing IxANVL can run on standalone workstations or on Ixia test hardware. Its MPLS Testing Ixia has addressed the challenges of operation can be completely automated protocol conformance testing by using a scripting interface. IxANVL source developing IxANVL (Ixia Automated code is also available to users for Network Validation Library), the industry customization, allowing a great degree of standard conformance test suite. While testing flexibility. supporting over 30 protocols overall, IxANVL contains over 800 test cases to MPLS scalability and performance testing validate routers for MPLS label The general methodology employed by Ixia encapsulation, and LDP and RSVP-TE for testing the scalability and performance protocol conformance. IxANVL provides of MPLS routers involves first surrounding positive as well as negative test cases the device or system under test (DUT/SUT) against the RFCs that specify these with Ixia hardware test interfaces. The Ixia standards. Negative tests help validate system then emulates everything else device response to “killer packets.” needed to test the device, including other IxANVL performs its tests as a dialog: it MPLS routers, IP route injection, LSP sends packets to the router being tested, signaling, and traffic transmission. In this receives the packets sent in response, and way, large and complex topologies can be then analyzes the response to determine simulated to test the DUT/SUT in realistic the next action to take. This allows IxANVL system environments, with a minimum of to test complicated situations or reactions hardware requirements. As an example, in in a much more intelligent and flexible way Figure 6, four Ixia test interfaces are than can be done by simple packet connected to the DUT with numerous generation and capture devices. routers being emulated per interface.

Ixia port Ixia port

IXIA IXIA IXIA IXIA

IXIA IXIA IXIA IXIA IXIA

IXIA IXIA IXIA IXIA

DUT

IXIA

IXIA IXIA IXIA

Ixia port Ixia port = emulated router IXIA IXIA

Figure 6. Ixia router simulation.

16 Copyright © 2004, Ixia MPLS: Conformance and Performance Testing Ixia has developed two primary generated over the established applications for MPLS performance connections. Alternatively, Ixia’s IxChariot testing, IxExplorer and IxScriptMate, each product can be used to transmit emulated with a distinct testing focus. enterprise application traffic over the MPLS device or network being tested to IxExplorer. IxExplorer provides a high level measure end-to-end application response of flexibility and functionality in protocol times. emulation, traffic generation, and analysis. IxExplorer is the primary controlling IxScriptMate. IxScriptMate provides a application for Ixia’s purpose-built framework for running automated test hardware test platform, allowing detailed scenarios. Numerous test suites have configuration of protocols and analysis of been developed within the IxScriptMate test results. environment for testing the session and circuit scalability, traffic throughput Within IxExplorer, a comprehensive set of performance, latency, and failover recovery IP routing and MPLS signaling protocols is capabilities of MPLS routers. IxScriptMate supported, including OSPF, IS-IS, RIP, BGP, simplifies the configuration process by LDP, and RSVP-TE, as well as multicast defining a configuration for the test and protocols. IxExplorer controls the protocol’s displaying the relevant parameters for user operation on Ixia’s test hardware input. Tests then run automatically, and architecture, which supports a CPU the results are presented to the user. This running Linux on each test port. This is especially useful for L2 and L3 VPNs, dedicated emulation environment allows where the test configuration can involve hundreds of MPLS routers to be emulated multiple protocols and complex traffic on each network interface. Up to hundreds generation requirements. of thousands of LSPs can be signaled from each interface. Line rate traffic can be

MPLS: Conformance and Performance Testing Copyright © 2004, Ixia 17 Conclusion In the post-bubble economy, the most and its impact on network performance important objectives for service providers and scalability. and carriers are to: To manage the complexity of MPLS, a wide • reduce operating costs range of protocols, services, applications, • preserve existing services and hardware must be tested and • introduce new services efficiently validated. For network managers and vendors of MPLS-related products and MPLS technology has proven its value for services, a comprehensive and well delivering new services while at the same designed conformance and performance time allowing migration from old to new testing solution is crucial to the success of networks. By converging new and legacy MPLS technology. network services over an MPLS network, providers and carriers can introduce Ixia provides that solution with efficiencies that promise great savings in • IxANVL, the industry standard operating costs. As a result, MPLS is well conformance test suite into mainstream deployment in networks • IxExplorer and IxChariot, providing around the world as a standard backbone flexibility and functionality in protocol technology for converged networks. emulation, traffic generation, and However, MPLS has proven to be an analysis extremely complex technology, • IxScriptMate, providing the efficiency encompassing a wide range of of automated testing functionality and applications. Vendors Together, these tools enable the providers who develop MPLS technology, as well as of next-generation MPLS products and organizations looking to deploy MPLS, services to ensure the reliability, must consider the complexity of the performance, scalability, and profitability technology, its continually evolving state, of their offerings.

18 Copyright © 2004, Ixia MPLS: Conformance and Performance Testing Appendix: MPLS This appendix contains several examples 1. Configure each IxANVL network Testing Examples of brief MPLS test plans, with specific interface with the appropriate examples showing how Ixia’s solutions network parameters, including those address the challenges of MPLS testing. of the DUT such as IP address, MAC address, gateway, etc. 1. IxANVL LDP Conformance Test 2. Specify configuration of the DUT, Objective: To characterize the MPLS typically via command scripts such router’s compliance with LDP RFC as Expect scripts. standards. 3. Select the set of IxANVL LDP test Test setup: IxANVL Linux workstation cases to run during the test session connected directly, or via Ixia test (see Figure 7). hardware, to DUT with two network 4. Run IxANVL in batch mode with the connections — one for request packets and command scripts, reconfiguring the one for response packets. DUT as required between test cases Methodology: IxANVL runs a number of test to match the IxANVL test setup. cases against the DUT based on direct Results: Number of tests passed/failed, interpretation of the LDP RFCs 3036 and including reasons for failed cases (see 3215. Figure 8).

Figure 7. IxANVL LDP test cases

missing label mapping message

Figure 8. IxANVL LDP test results.

20 Copyright © 2004, Ixia MPLS: Conformance and Performance Testing 2. IxScriptMate L2 VPN Partial Mesh Methodology: Performance Test 1. Each Ixia port simulating a PE router Objective: To determine the maximum rate establishes an OSPF session, LDP an LSR configured as an L2 VPN PE router session, and Extended LDP (Martini) can “push” MPLS labels onto incoming session with the DUT. Layer 2 packets and forward the resulting 2. If more than one Ixia port is being MPLS traffic, or “pop” labels from used to simulate PE routers, the VC incoming MPLS packets and forward the IDs can be distributed among them resulting Layer 2 traffic with no loss. in either round robin or consecutive fashion. Test setup: Minimum of two Ixia ports connected to the DUT — one to simulate a 3. The CE and/or PE ports transmit PE router and another to simulate a CE traffic at the specified rate. If frame router. Additional ports can be configured loss occurs, the transmission rate is to emulate multiple PEs/CEs (see Figure alternately reduced/increased using 9). The IxScriptMate application, running a binary search algorithm to on a workstation, controls the test running determine the maximum rate at on Ixia hardware. which the DUT can forward traffic without loss. Parameters: Number of PEs/CEs, number of VCs per PE, VC distribution style Results: Frame loss, latency, data errors, (consecutive or round robin), frame size sequence errors. distribution, traffic transmission rate.

Martini CE encapsulated PE IXIA L2 traffic traffic IXIA

i PF in S ic rt O as a B M P d D e L nd te Ex P D PE L OSPF LDP Basic CE PE IXIA LDP Extended Martini IXIA DUT

O L S D LD P P P F E B xt a e si nd c ed M ar ti ni CE PE IXIA IXIA

Figure 9. Test setup

MPLS: Conformance and Performance Testing Copyright © 2004, Ixia 21 3. IxScriptMate L3 VPN RSVP-TE Egress address of the simulated PE router. Performance Traffic engineering parameters are advertised using OSPF-TE. Objective: To determine the maximum rate an LER configured as an L3 VPN PE router 2. Bidirectional LSPs are established can “pop” MPLS labels from incoming using RSVP-TE. packets and forward the resulting IP traffic 3. A Multi-Protocol internal BGP (MP- with no loss. iBGP) session is established with the DUT. Test setup: Two Ixia ports connected to the DUT — one to simulate a PE and P router 4. The port simulating the PE router and another to simulate a CE router (see transmits MPLS traffic at the Figure 10). specified rate. If frame loss occurs, the transmission rate is alternately Parameters: OSPF parameters, BGP reduced/increased using a binary parameters, number of routes per CE, frame search algorithm to determine the size distribution, traffic transmission rate. maximum rate at which the DUT can Methodology: forward traffic without loss. 1. The port simulating the PE/P router Results: Transmit rate, latency, data errors, establishes an OSPF session with the sequence errors. DUT and advertises the loopback

MPLS traffic

CE IP traffic PE P PE

OSPF OSPF IXIA IXIA IXIA RSVP-TE DUT MP-iBGP session over provider backbone

Figure 10. IxScriptMate L3 VPN RSVP-TE egress performance.

22 Copyright © 2004, Ixia MPLS: Conformance and Performance Testing 4. IxExplorer LDP Extended Martini Session the DUT with one or more Layer 2 VC Scalability Test FECs advertised per session. Objective: To determine the maximum 4. Status on the port is monitored to number of LDP Extended Martini sessions determine if all configured sessions the DUT can sustain at one time. are successfully established. Figure 14 shows the MPLS Martini labels Test setup: One Ixia port connected to the learned by IxExplorer from the DUT — DUT (see Figure 11). one for each session. Methodology: 5. If all sessions are successfully 1. An OSPF session is established with established, the number of extended the DUT. sessions configured is increased and 2. An LDP basic session is established the test rerun. If not all are with the DUT, advertising the Ixia port established, the number of sessions loopback address as a FEC. is lowered and the test repeated. 3. A number of LDP Extended Martini Results: LDP Extended Martini session sessions (based on test capacity. expectations) are established with

IXIA

emulated PEs IXIA DUT P router

IXIA physical connections emulated connections IXIA OSPF sessions LDP sessions LDP Extended Martini sessions

Figure 11. IxExplorer LDP Extended Martini session scalability test setup

label information

Figure 12. Test results (learned labels)

24 Copyright © 2004, Ixia MPLS: Conformance and Performance Testing 5. IxScriptMate VPLS MAC Address Cache the specified DUT MAC address table Capacity Test size, are sent to the Learning port. These frames contain varying source Objective: To determine the maximum MAC addresses and a fixed capacity of a router’s Layer 2 MAC address destination MAC address cache. corresponding to the address Test setup: A minimum of three Ixia test connected to the Test port. ports connected to the DUT — a Test port, a 3. Validation frames are sent to the Test Monitoring port, and a Learning port. port back to the addresses learned Parameters: Number of PEs per port, on the Learning port. number of VPLS instances per CE, number 4. The Monitoring port listens for of hosts per VLAN, DUT MAC address table flooded or mis-forwarded frames size, DUT MAC address aging time. (See from the DUT. Figure 13.) 5. A binary search algorithm is used to Methodology: determine the maximum number of 1. OSPF and LDP are run based on addresses that can be learned user-configured parameters to set up without flooding or dropping frames. the network topology and signal the Results: Maximum MAC address capacity VPLS instances. total and per VPLS instance. (See Figure 2. Learning frames, equal in number to 14.)

Figure 13. IxScriptMate run setup

Figure 14. IxScriptMate test results

26 Copyright © 2004, Ixia MPLS: Conformance and Performance Testing 6. IxExplorer RSVP-TE Fast Reroute Test detour. Objective: To measure the LSP switchover 3. Unicast traffic is sent from the time of a router running RSVP-TE Fast ingress port over the primary LSP. Reroute between a primary LSP and a 4. A switchover to the detour LSP is detour LSP upon link failure. initiated by bringing down the link to the DUT on the primary LSP. Test setup: Three Ixia test ports connected to the DUT — one acting as the ingress and 5. Traffic is captured on both the egress two as egress (primary and detour). See ports. The switchover time is Figure 15. calculated by comparing the timestamp of the last packet Methodology: received on the primary port with the 1. Two bidirectional LSPs are signaled timestamp of the first packet using RSVP-TE through the DUT from received on the detour port. the Ixia ingress and egress ports. Results: Fast Reroute switchover time of 2. RSVP-TE Fast Reroute objects are the DUT. signaled to establish one LSP as a primary and the second LSP as a

IXIA

primary LSP egress LER 1

IXIA DUT detour LSP ingress LER

IXIA egress LER 2

Figure 15. IxScriptMate run setup

Border Gateway Protocol (BGP) An exterior gateway protocol defined in RFC 1267 and RFC 1268. BGP is the principal protocol used along the Internet backbone and within larger organizations.

Constraint-Based Routing Routing that uses intelligent path computation and explicit route specification to determine routes. This differs from typical non- Constraint-Based Routing, in which routes are calculated based only on shortest path. Constraint-Based Routing enables traffic engineering in MPLS networks.

Class of Service (CoS) Class of Service (CoS) is a method for managing network traffic by grouping similar types of traffic (for example, e-mail, streaming video, voice, large document file transfer) together and treating each type as a class with its own level of service priority.

Customer Edge Router (CE) A router at the edge of a customer network, the CE interfaces to a corresponding Provider Edge (PE) router at the edge of the service provider’s network.

Diffserv An architecture for providing different types or (Differentiated Services) levels of service for network traffic.

Exterior Gateway Protocol (EGP) A protocol that distributes routing information to the routers that connect networks.

Fast Reroute A mechanism used in MPLS networks to provide redundant data paths for recovery from node or link failures. The RSVP-TE protocol is used to signal Fast Reroute configuration.

Forward Equivalency Class (FEC) A classification of a group of packets — all packets assigned to a FEC receive the same routing treatment. FECs can be based on IP address prefixes or service requirements for a type of packet (QoS, VPN, Traffic Engineering, etc.).

Forwarding Information Base (FIB) A table containing the information necessary to forward IP data in a router. At a minimum, the FIB contains the outbound interface identifier and next hop information for each reachable IP destination network.

28 Copyright © 2004, Ixia MPLS: Conformance and Performance Testing Internet Gateway Protocol (IGP) Protocol that distributes routing information to the routers within a network. The term “gateway” is historical; “router” is currently the preferred term. Example IGPs are OSPF, IS-IS and RIP.

IS-IS An OSI/IP routing protocol, IS-IS stands for Intermediate System to Intermediate System (i.e., router to router). MPLS traffic engineering parameters can be distributed with IS-IS using extensions to the protocol (IS-IS-TE).

L2 VPN An emulation of a Layer 2 switching environment, supplied by a service provider for its customers, via a core network. In MPLS networks, L2 VPNs use LDP to signal connections for transporting Layer 2 frames over MPLS.

L3 VPN An emulation of Layer 3 services/distribution of routes, supplied by a service provider for its customers, via a core network. L3 VPNs use BGP extensions to signal provider-provisioned VPNs per IETF Draft RFC 2547bis.

Label Distribution Protocol (LDP) A protocol, defined in RFC 3036, used to distribute MPLS label and stream mapping information.

Label Edge Router (LER) A router at the edge of an MPLS network. At the ingress side, an LER maps IP packets to LSPs, adds the appropriate MPLS header, and forwards the packet to the next hop. At the egress side, an LER strips the MPLS label(s) and forwards the packet using traditional routing mechanisms.

Label Information Base (LIB) A table that specifies how to forward a packet in an MPLS router. This table associates each label with its corresponding FEC.

Label Switched Path (LSP) In MPLS, a path through a network from an ingress to an egress router that has been established through the distribution of labels that define hop-by-hop forwarding treatment.

Label Switching Router (LSR) A router, operating in the core of an MPLS network, that switches traffic based on labels.

MPLS: Conformance and Performance Testing Copyright © 2004, Ixia 29 Martini Drafts A set of IETF draft specifications (named for primary author Luca Martini) that define the mechanisms for creating Layer 2 MPLS VPNs. Such VPNs support Layer 2 traffic such as Frame Relay, ATM, and Ethernet tunnels over an MPLS network.

Open Shortest Path First (OSPF) A link-state routing protocol used by IP routers located within a single Autonomous System (AS) to determine routing paths. MPLS traffic engineering parameters can be distributed with OSPF using extensions to the protocol (OSPF-TE).

P Router (Provider Router) A router that operates in the core of an service provider network.

Provider Edge Router (PE) A router that operates at the edge of a service provider’s network, interfacing with the corresponding Customer Edge (CE) router(s) at the edge of one or more customer networks.

Quality of Service (QoS) A measure of performance for a transmission system that reflects its transmission quality and service availability. QoS mechanisms provide the ability to manage network traffic’s bandwidth, delay, and congestion.

Resource Reservation Protocol — Extensions to the RSVP protocol related to Tunneling Extensions (RSVP-TE) traffic engineering. RSVP-TE implements an assignment of labels from ingress to egress routers, with consideration for bandwidth and other QoS requirements.

Routing Information Protocol (RIP) An Internet routing protocol that uses hop count as a routing metric. RIP is the most common IGP used in the Internet.

Traffic Engineering Techniques and processes that optimize the routing of network traffic. Traffic engineering mechanisms enable network administrators to manage network traffic’s bandwidth, delay, and congestion.

Virtual Circuit (VC) A circuit or path between points in a network that appears to be a discrete, physical path but is actually part of a managed pool of resources from which specific circuits are allocated as needed to meet traffic requirements.

30 Copyright © 2004, Ixia MPLS: Conformance and Performance Testing Virtual Private LAN Service (VPLS) A class of VPN that supports the connection of multiple sites in a single bridged domain over a managed IP/MPLS network. The goal of VPLS is to provide a protocol-transparent, any- to-any, full-mesh service across a WAN.

Virtual Routing and Forwarding (VRF) A VPN routing/forwarding instance. A VRF Table includes the routing information that defines a customer VPN site that is attached to a PE router.

Acknowledgements Authors: Bruce Miller, Elliott Stewart