Agilent Measurement Journal - Issue 4 - 2008 - (Page 33)

For TCP trafﬁc, raw packet rates are an inconclusive metric. It’s far more useful to make throughput measurements that account for the retransmission characteristics of TCP, again at the huge scale of real networks. As an example, a forwarding device may be capable of passing IP packets with a low rate of loss. However, if the lost packets happen to be spread out, then the number of TCP retransmissions can be large and therefore cause much slower overall throughput of application trafﬁc. With numerous network-user results accumulated, the test instrument must store, sort and present them in a way that makes it easy to spot problems and verify performance. With typical scale numbers of hundreds of thousands of users, the ability to extract useful insights depends on the ﬁltering and grouping of results according to trafﬁc characteristics and result values. Finding signiﬁcant results would otherwise be akin to looking for a needle in a haystack (Figure 4). Conclusion The tantalizing possibility of converged voice, data and video is at last within our grasp. Such convergence is hugely attractive to service providers, but users will embrace an offered service only if it performs at least as well as existing mechanisms for phone and TV. To achieve convergence, the IP networks of today must evolve more in the next few years than telecom has in all the 150 years of its existence. This will be made possible by rigorous testing that accurately simulates real trafﬁc types at real-world scale in the design, development and networktrial phases. 10010010001110101110100100011010111010110011100010101001110101011010100101101001110100101101101001 10100100100011101011101001000110101110101100111000101010011101010110101001011010011101001011011010 Figure 4. Tools for results analysis must scale up to match the vast quantities of collected test data. Agilent Measurement Journal 33

Table of Contents Feed for the Digital Edition of Agilent Measurement Journal - Issue 4 - 2008

Agilent Measurement Journal - Issue 4 - 2008 Delivering Confidence through Compliance with Standards Contents Emerging Innovations Trying Early Device Implementations at the IEEE 1588 PlugFest Achieving Greater Confidence in Measurement Accuracy through Consistency in Calibration Services Overcoming the Challenges of RFID Component Testing 3GPP LTE: Introducing Single- Carrier FDMA Ensuring Reliable Operation and Performance in Converged IP Networks Testing Storage Area Networks and Devices at 8.5-Gb/s Fibre Channel Rates Choosing an Appropriate Calibration Method for Vector Network Analysis Making Traceable EVM Measurements with Digital Oscilloscopes Exploring Terahertz Measurement, Imaging and Spectroscopy: The Electromagnetic Spectrum’s Final Frontier Interpreting Quoted Specifications when Selecting Digitizers

Agilent Measurement Journal - Issue 4 - 2008

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