TEST AND MEASUREMENT


Four decades of Ethernet evolution – and counting… Testing the Ethernet waters by Xing Ye, UniPRO Product Manager with IDEAL Networks


Slowly and quietly Ethernet over the last four decades, Ethernet has taken over the world - the world of networking that is. In its Carrier Ethernet and Metro


Ethernet forms, it is far more complex than the simple LAN variants most of us work with. So how do these more complex forms of Ethernet differ? And what difference does it mean for the testing process? Ethernet started its life back in 1973-4


Xing Ye reveals how Ethernet has quietly taken our world by storm...


with Robert Metcalfe at Xerox Parc. By 1976 the system was realised as hardware and deployed across Xerox Parc. Metcalfe and colleague David Boggs then published a seminal paper that announced Ethernet to the world. It’s worth noting that, before


Ethernet, each manufacturer had its own proprietary networking system. The vendor lock-in was total. So great were the benefits to


customers of this new inter-networking capability that Ethernet soon quashed most other networking technologies in the Enterprise LAN. A major driver for this domination was its capability to work over simple, cheap twisted pair cable. Over the last 40 years, Ethernet


has shown itself highly adaptable; first in the enterprise LAN and then more recently the data centre LAN. Its speed capability has gone from the initial 4Mb/s to 10, then 100, 1000 and 10,000 Mbit/s(10Gb/s). On short-range copper, we are now up to 40Gb/s. The more ubiquitous Ethernet has


become, so the component costs have fallen on the familiar cost/volume curve - and all making it even more attractive. And it’s because of its cost and


ubiquity that the previously very separate world of carriers became involved in Ethernet. Carriers came from a world of


circuits. Originally individual private circuits consisting of one or two dedicated twisted pairs from A to B. As time went on, they provided dedicated ‘virtual circuits’ using mostly synchronous network protocols like SDH and SONET. But providing SDH or SONET


- and other protocols such as frame- relay and X25 - to enterprise users was


28 NETCOMMS europe Volume IV Issue 1 2013 Ethernet powering the past - and the future www.netcommseurope.com


quite expensive and since most of their customers now wanted to connect to an Ethernet LAN, expensive protocol converters were also needed. Furthermore Ethernet allowed


‘circuits to be shared’ greatly reducing their cost of provision. The writing was on the wall- carriers needed to embrace Ethernet. But here’s where Ethernet once


again needed to adapt and evolve - the world of carrier networks is much more complex than that of the enterprise or data centre LAN. Whilst it is true that both need to be


able to segregate data traffic into quality- of-service (QoS) streams so that video and voice are given priority, the reality is that general data can suffer small delays with little or no degradation to user service.


A major factor for carriers, however,


was the need to be able to provide each customer with specific guaranteed bandwidths across their networks - whilst ensuring that the ‘bursty’ nature of the Ethernet traffic didn’t overload or disrupt the guaranteed performance for other customers. To develop the capability for carrier


networks to use simple, cheap Ethernet - but to add-in the extras they needed - the Metro Ethernet Forum was created. Before long Carrier/Metro Ethernet appeared complete with quite a lot of extra complexity. It is this extra complexity, which means that testing carrier-grade Ethernet is very different to testing its much simpler LAN variants.


RFC2544 For many years, and for the want of any better test standard, Carrier- grade Ethernet has been testing to the RFC2544 standard, which covers issues such as throughput (bit/s); latency; frame loss; back-to-back (burstability) and system recovery. There are many testers available


to do this including our own models. However, RFC2544 testing has three major drawbacks. Firstly, the standard it was never


designed for live field testing but rather for testing individual pieces of equipment on the lab bench to its limits. Secondly, RFC2544 only tests a single


Not just carriers Interestingly, because of its extra capabilities, Carrier Grade Ethernet is now used by many other sectors. You’ll find it used on trains and metros – where critical brakes and safety systems share the same Ethernet network as public address, electronic signage and IPCCTV - as well as for track-side signalling.


Also in mobile wireless networks for


cell site backhaul and public WiFi, in petrochemical plants, by public utilities to control their national distribution networks and in many Industrial Ethernet applications. And in all of these applications,


engineers need to be able to fully test the more complex Carrier-grade Ethernet both for service turn-up (commissioning) and for fault finding.


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