A CRITICAL REVIEW OF IEEE 802.3

A critical review of IEEE 802.3



A critical review of IEEE 802.3

Introduction

Today's Devices Under Test (DUT) represent complex, multi-protocol network elements with an emphasis on Quality of Service (QoS) and Quality of Experience (QoE) that scale to terabits of bandwidth across the switch fabric. The Spirent Catalogue of Test Methodologies represents an element of the Spirent test ecosystem that helps answer the most critical Performance, Availability, Security and Scale Tests (PASS) test cases. The Spirent Test ecosystem and Spirent Catalogue of Test Methodologies are intended to help development engineers and product verification engineers to rapidly develop and test complex test scenarios.

Core networking applications have demonstrated the need for bandwidth beyond existing capabilities and beyond the projected bandwidth requirements for computing applications. Switching, routing, and aggregation in data centers, in terabit exchanges and service provider peering points, and high bandwidth applications such as video on demand and high performance computing, need a 40/100 Gigabit Ethernet interface. The need for 40/100 GB Ethernet at the core of the network initially, extending to the edge eventually, is driven by many factors, including elimination of aggregation protocols, bandwidth growth at the edge of the network, and the rise of for-pay services like HD IPTV, VoIP, cloud computing, and cloud storage (IEEE computer society 2003, p.12-18) .

The 100 GB delivery test requirements are different than previous 1 GB and 10 GB because of the strong emphasis placed on QoS/CoS, realism, stacked protocols, and multiplay services over 100 GB. Imprecise clocking between systems at 40/100 GB can increase latency and packet loss. Testing with backwards compatible system is critical. Latency issue is an important issue. At 10 GB, especially at high densities, the specification allows for a little variance for clocks. As you aggregate traffic into 10 GB ports, small differences between clocks can cause high latency and packet loss. At 40 GB, the tolerances are even smaller. This is a critical requirement in data centers today. The innovations in data-center networking and Ethernet address lower latencies and enhanced queuing and buffering. Key test metrics for IEEE 802.3ba 100 GB Ethernet are:

Layer 1 skew performance: Lane skew was a contributor in older Ethernet roll out issues, being able to add skew and to measure effects are a critical part of the physical layer setup. Layer 1 lane swapping. Measuring the ability of the DUT to manage the virtual to physical translation is critical because lane swapping errors can lead to interface link-down problems that are difficult to debug in deployed systems. Layer 1 per-lane unique bert (PRBS). The ability to test the physical pathways using unique PRBS BERT patterns reveal physical lane stability and crosstalk issues (Gilb 2004, p.20-28).

Latency and jitter. Testing 100 GB to 100 GB, 100 GB to 40 GB, and 100 GB to multiple 10 GB ports is a critical test of backwards compatibility. The ability to measure jitter to 2.5 ns in the core is essential. RFC2544 100 GB ...