Media Delivery Index (MDI) is emerging as the metric of choice for IPTV testing, though not all the big test firms are backing it

June 16, 2006

3 Min Read
IPTV Testing Goes Standard

If you hadn't heard of MDI (Media Delivery Index) a month ago, there's a good chance you'll know about it now, especially if you went to this month's Globalcomm show in Chicago.

That's because it was the tag du jour of some of the major test and measurement firms that were touting their IPTV capabilities on the show floor. (See Agilent Tests IPTV and Ixia Unveils IPTV Tester.)

MDI is a measure of video quality, in the same way that MOS (mean opinion score) is used as a measure of voice quality. It provides an "at-a-glance" indicator of IP jitter and packet loss using data gathered by network probes, and is expressed as a "delay factor" and "media loss rate."

But it's nothing new: Specialist IPTV test firms like Bridge Technologies Co AS and IneoQuest Technologies Inc. have been singing from the MDI hymn sheet for months, and in IneoQuest's case, years. (See IneoQuest Spews Video Test News.)

That's because IneoQuest, along with Cisco Systems Inc. (Nasdaq: CSCO), authored the measurement and submitted it to the Internet Engineering Task Force (IETF) , where it is currently in RFC (request for comment) stage (RFC 4445, to be exact).

IneoQuest CEO Marc Todd says that process has been crucial in making MDI an accepted method of monitoring video traffic quality, though with more than 200 customers, including equipment vendors and service providers, already using IneoQuest's equipment, MDI has become a de facto industry standard.

And there are plenty more opportunities, reckons Todd. "Every telco on the planet has something in the hopper" in terms of an IPTV strategy, says the CEO.

That's why, just prior to the Globalcomm event, the company unveiled its latest MDI-based product suite, which service providers can use to test the video throughput capabilities of network elements. (See IneoQuest Stresses Video Switches.)

And during Globalcomm, Agilent Technologies Inc. (NYSE: A) specified it had built MDI capabilities into its N2X multiservices test product that can be used for pre-deployment IPTV service testing.

Ixia (Nasdaq: XXIA), meanwhile, said it supports a number of IPTV metrics, including MDI, in its Aptixia IxLoad 3.10 platform that simulates various network elements and subscriber behavior. Ixia's system is being used by BCE Inc. (Bell Canada) (NYSE/Toronto: BCE) as it prepares to launch IPTV services and has even had its system endorsed by Alcatel (NYSE: ALA; Paris: CGEP:PA), which is involved in many of the world's IPTV rollouts.

But not everyone's jumped on board the MDI bandwagon. The most notable exception is Spirent Communications plc , which has gone as far as to describe MDI as an "older, primitive" approach that is already obsolete.

That's because it's pushing an alternative called V-Factor, developed by QoSmetrics Inc. Spirent has integrated V-Factor into its IPTV Quality of Experience (QoE) Test System, and says it is superior to MDI because it takes more factors into account and provides a metric that correlates more closely with the viewing experience of IPTV subscribers. (See Spirent Adds V-Factor and QoSmetrics Offers Video Test Tools.)

MDI is "unsuitable for video quality assessment," according to Spirent VP Bahaa Moukadam, because it "only looks at two network parameters and is blind to video stream content," whereas his company's system looks at network impairments and video stream content, he is quoted as saying in a prepared statement.

QoSmetrics has found some carrier support for its approach in Taiwan, where national carrier Chunghwa Telecom Co. Ltd. (NYSE: CHT), which has already launched its IPTV services, is a customer.

— Ray Le Maistre, International News Editor, Light Reading

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