Why Test for MPLS Conformance?
MPLS standards and implementations are dynamic. At the time of this writing, there were over 100 IETF drafts associated with MPLS, and over 20 RFCs. In such a dynamic environment, standards compliance and the corresponding expectation of equipment interoperability present significant challenges.
Equipment vendors find themselves at the leading edge of these challenges as they continually update their feature sets to the latest standards and options, while at the same time improving performance and scalability. They must do this, both to remain competitive in their market and to meet the demands of their customers. Development test and quality assurance groups therefore need an efficient way to verify the correctness of their implementations. Formalized conformance testing against standards supplies this confidence. Beyond ensuring product interoperability and quality, conformance testing can also accelerate product development by detecting bugs or correcting design issues early in the development cycle, thereby reducing the product抯 time to market and hence increasing profitability.
For both service providers and enterprise organizations, multi-vendor environments are the reality today. Such a reality is untenable without equipment interoperability driven by standards-based implementations. Networks are also dynamic, so when it comes time to upgrade, conformance and regression testing are crucial to ensure that new software releases do not break existing services.
To achieve adequate test coverage for compliance with a standard, hundreds of conformance test cases are typically necessary to cover a given protocol, and these tests must be appropriately updated as necessary. Since test cycles are often very frequent (daily in some cases), these tests must be automated as well. To address these challenges, most vendors and service providers rely on conformance testing products that are maintained and supported by a dedicated third-party.
Why Test for MPLS Scalability and Performance?
After verifying the standards compliance and interoperability of an MPLS system, the next challenge is to determine the ability of an implementation to perform in a real network. Given the complexity of the protocols involved and the multi-layered nature of MPLS, scalability and performance are often genuine concerns. Equipment vendors typically test and publish the scalability and performance capabilities of their products. End users will often validate the numbers while additionally testing specific network scenarios unique to their deployment.
Scalability
Scalability is typically viewed as the biggest challenge in service providers?MPLS networks today. They must understand the dynamics of growth in their networks as new customers are added, as well as the ultimate limits of their networks. Several metrics are key in determining scalability:
- Router capacity: The capacity of the MPLS routers to handle large numbers of LSPs, VPN instances (VRFs or VCs), and routes is important to determine when sizing the overall network.
- LSP setup rate: The rate at which LSPs can be set up is an important factor in overall network responsiveness.
- Signaling protocol scalability: The?limits of an MPLS router running?signaling protocols such as LDP or RSVP-TE must be verified to determine the number of protocol sessions that can be sustained.
Together, these numbers will determine the quantity of routers that must be deployed for a given number of customers.
Performance
One of the original proposed benefits of MPLS was the performance boost associated with switching on a label as opposed to routing on an IP address. While this is of less concern today, the forwarding performance of PE routers at the edge of the MPLS network still involves IP (or other) lookups and assignments. Vendors and service providers alike must test and characterize MPLS devices across multiple interface types (Ethernet, POS, ATM) for traditional data plane performance metrics:
- Data throughput
- Packet loss
- Latency
- Jitter
Given the advances in hardware-based routing in recent years, the expectations for device performance have grown so that line rate traffic support is typically a given. But the MPLS routers of today are being asked to perform many functions, with operational requirements at the data (traffic), control (routing), security, and management planes. With requirements for MPLS routers to run multiple protocols simultaneously, to interoperate among multiple technologies, and to apply QoS and other policies to traffic, the reality is that full performance is not a given. Performance must be viewed in different usage scenarios, depending on how the network is designed and being operated.
Together, scalability and performance metrics can be competitive differentiators for equipment vendors. For service providers and network managers, they are a key selection criteria between vendors. Characterizing these elements is critical, since they directly impact the service quality that can be delivered to the end customer.
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