When it comes time to buy Internet services, network executives are inundated with measurements that service providers use to show the size and performance of their IP networks.Number of points of presence; number of countries supported; amount of packets carried; number of domains connected. Service providers quote these and other measures to show that they have the largest or most expansive or most interconnected IP backbones.But do any of these numbers really matter to corporate customers? Yes and no, industry analysts say. Buyers should consider the metrics that ISPs use to track their IP networks, but they should keep their own needs in mind when choosing a service provider, experts say.Brownlee Thomas, a principal analyst with Forrester Research, recommends that buyers look beyond bandwidth and traffic measurements to find out how service providers design and configure their networks."I don't care that you have the most POPs. I care that your POPs are where I need them. I don't care that you have the fattest pipes. I care if you have the fattest pipes where I need them. There's a difference between having the biggest network and having the best network to meet my needs," Thomas says.Corporate buyers also must keep in mind that no standard methodology exists for measuring IP networks. No government agency or industry group publishes statistics about IP network size or performance. Instead, each ISP measures and publishes its own performance against its preferred metrics. So buyers have to be careful not to compare apples and oranges."There is no forum in which all the ISPs participate in which we share all of our data using a consistent methodology," says Fred Briggs, president of operations and technology at MCI.Most service providers focus on two types of metrics: those that measure the size of their IP networks and those that measure network performance. In the first story of this two-part series, we'll look at the measurements that ISPs use to determine IP backbone size. Next week, we'll look at how ISPs measure network performance.Most top-tier ISPs have similar-sized network backbones - OC-192 pipes running at 10G bit\/sec are the norm - and they deploy top-of-the-line routers from vendors such as Cisco and Juniper. So bandwidth or router size is not likely a differentiator.Where buyers can find differentiation is in the geographic reach of various IP networks.One key measure is the number of countries where an ISP owns or controls network footprint. The ISP that usually wins this contest is\u00a0Equant, which boasts IP services in 145 countries.Equant earlier this month won a major contract extension from satellite phone service provider Globalstar because of the global reach of Equant's private IP network. Globalstar uses Equant's IP VPN services in 15 countries across North America, Latin America, Europe, Asia Pacific and the Middle East."The strength that Equant brought to the table is its worldwide reach. And the price was right," says Mac Jeffery, senior director for marketing communications at Globalstar, which counts U.S. military operations in Afghanistan and Iraq among its customers. "Our biggest business is going to be in those odd-ball locations way out on the edge of the world."Jeffery says Globalstar plans to add IP VPN locations in Puerto Rico, Alaska and India over the next year. "We're confident that when it comes time to broaden our network, Equant will be there," he says.Another measure that ISPs boast about is the number of IP POPs on their networks.\u00a0MCI\u00a0touts that its global IP network features 4,500 company-owned POPs on six continents - all but Antarctica. This is the figure that MCI uses to say it runs the largest IP backbone in the world."What becomes relevant from a customer standpoint is how many POPs you have in the world," Briggs says. "This metric shows how many places I can get on your network and you can provide me with capability."The reach of an ISP's network - whether measured by POPs or number of cities supported - matters because most service-level agreements (SLA) apply once the customer is on the carrier's own network rather than a local access network."Once they get on our network, then the SLAs we offer become relevant," Briggs says. "Companies that have manufacturing or customer service operations around the world can get a consistent quality of service."For corporate buyers, being able to get Internet access from a particular country isn't as important as what other IP services are available there. Currently, top-tier ISPs are competing to see who can offer Multi-protocol Label Switching (MPLS) service in the most countries."It's not just the raw POP counts that matter," says Christine Sorenson, a technology consultant with\u00a0AT&T. "What matters is where you can get the service you need. You need to ask how many of the POPs can be used with an MPLS VPN."Another measurement that ISPs use to describe the size of IP networks is the amount of packet traffic carried.AT&T, for example, asserts that its North American IP backbone carries the most traffic on a monthly basis. Last year, AT&T surpassed MCI to take the top spot in a ranking of Internet traffic compiled by telecommunications research firm RHK."The reason we pride ourselves on the amount of traffic we carry is that it is an indicator of the economies of scale we bring to the market," says Craig Uthe, IP network product management director for AT&T. "About 1.3 petabytes of data per day goes through our network."AT&T says traffic measurements are important because they show how widely AT&T's IP network is used."It gets back to Metcalfe's Law, which states that the value of a network increases with the number of nodes," Sorenson says. "If there's more traffic on a network, more people who are trying to reach each other are on that network, and the traffic gets there faster."Meanwhile, MCI touts a different metric - the number of autonomous system network connections it has - to show the value of its IP backbone network. MCI was ranked first in this metric by TeleGeography Research, which says this statistic shows the connectedness of an IP network to the rest of the Internet."We have historically connected to the most number of domains," Briggs says, adding that this measure is important because it shows that MCI interconnects with the most ISPs around the world.How interconnected an IP backbone network is matters because it affects how quickly communications can get from one ISP to another, says Bryan Van Dussen, director of telecommunications strategy at The Yankee Group."If I were a corporate buyer, I'd ask ISPs how many routes they were broadcasting and to show me their autonomous system numbers. Then I'd run some ping tests to see how many hops it takes for my communications to get around the Internet," Van Dussen says.Although the top-tier ISPs spend a significant amount of time and energy arguing that their networks are the largest according to particular metrics, corporate buyers usually care more about network performance than network size."Latency, availability and packet loss: That's what the customer sees and can measure and impacts their services," Briggs says.Next week: A closer look at these three key metrics for IP network performance, and a few new metrics that are useful when buying emerging services such as VoIP.