'The Internet is down.' What does that really mean?

A multiplicity of factors can interrupt service, from temporary annoyances to long-term problems

Type a URL into your browser, or click on a link. Then you wait for an instant or two, while your page loads. But sometimes you keep waiting. Or you get Error 404: Page Not Found. Possibly, your browser times out while waiting for the server to respond. We tend to summarize all these events with a simple phrase, like "The Internet is down."

In almost all cases, that worldwide interconnection of networks that gives us the World Wide Web, e-mail and countless other online services is still operating. The Internet is still there; we just can't get to it.

But why? The root cause might be almost anywhere. The culprit could be something inside your computer, attached peripheral equipment, a service interruption from your own network or ISP. It could be a regional or wider-scale outage caused by faulty equipment, weather problems, accidental or malicious damage to cables, disruptions caused by malicious software such as viruses and Trojan horses. Or it could be something as simple as the need for routine maintenance.

Possible points of failure

Inside your local system and close by: A hardware component or connection failure is a real possibility. If the hardware is OK, how about software? Windows is notorious for slowing down over time. How long has it been since Windows was installed or since its registry was checked for inconsistencies and cleaned out? Have you installed the latest service packs and patches to your operating system and browser? Is your antivirus, antispyware and firewall software up to date and working properly?

Regional upsets: Maybe the problem lies with your office network or ISP. A quick phone call to the help desk, the network administrator or your ISP will let you know. Their problems could involve hardware or software. Service might be down because of severe weather such as a hurricane, an electrical power outage, or physical damage to a data center or its building caused by anything from an accident to an earthquake to an act of terrorism. It's all unlikely -- and all possible. In July 2007, a major electrical outage in San Francisco took down for several hours a data center hosting a number of popular sites, including Craigslist, TypePad, Technorati and Second Life.

Major service provider outages: Simple things can have unexpected consequences, especially for major service providers. In February 2009, millions of Google users lost access for more than two hours as a result of unplanned downtime caused by testing new software during regular data center maintenance.

Similarly, in February 2008, a two-hour global Hotmail outage occurred, which also affected MSN Messenger and other Microsoft Live services. In July 2001, MSN Messenger was down for up to a week for some users after a disk controller in a database server failed.

Amazon's cloud computing Simple Storage Service, which provides on-demand storage, suffered an outage in February 2008 when a data center's authentication service was overloaded. Similar outages the following June led to speculation that the site was the target of a denial-of-service attack.

A software failure took down parts of eBay intermittently for almost a day in 1998. The online auction site reportedly lost more than $3 million in revenue because of customer refunds and waived fees. After similar problems in 1999, 2002 and 2003, eBay created an outage policy for customers and reassured investors it had resolved reliability issues.

International connections: Despite the wide use of satellites and wireless communications, global communications still depend heavily on fiber-optic cables that cover the planet and connect continents. In December 2008, millions of Web users in the Middle East were put out of communication by damage to a string of underwater cables in the Mediterranean Sea between Italy and Egypt. As much as 70% of all Internet traffic and telephone communications between Europe and Africa was affected, and Internet traffic had to be rerouted through Asia and the U.S. Similar cable damage had occurred less than a year before when ships' anchors had torn through a different section of those same cables.

What to do?

When you lose Internet service, try these few steps before you call for help. First, wait a few minutes; many Internet outages resolve themselves in short order. If you get a timeout message, try again right away. Check all I/O cables, including those attached to your PC, router, network, and cable or DSL modem. If you're on a wireless connection, try plugging in with a cable.

Next, unless there's good reason you cannot or should not do so, try restarting your computer and, if applicable, your router and/or modem. Restart, not reset: just unplug them, wait 30 seconds, then plug them back in again and let them reboot. Nine times out of 10 this will fix the problem. If not, call for help.

Kay is a Computerworld contributing writer in Worcester, Mass. You can contact him at russkay@charter.net.

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