From time to time, someone will tell me that they are experiencing trouble using Netflix because of buffering but that HBOMax streams fine, and that both use the same internet connection in the same house. Other times I have been told that Netflix streams very well, but that Amazon does not. While it is difficult to know with certainty exactly what might be the cause of this, it is possible the answer is “anycast.”

Anycast is a network addressing and routing methodology in which a single destination address has multiple routing paths to two or more endpoint destinations. Routers will select the desired path on the basis of number of hops, distance, lowest cost, latency measurements, or the least congested route. Anycast networks are widely used for content delivery network (CDN) products to bring their content closer to the end user. English translation: When you connect to a website such as The New York Times, you might logically think you are connecting to a server on the east coast of the U.S., but it is actually possible the web page you see is being provided by a server physically located in Mexico City.

Anycast technology allows content providers to improve their ability to serve customers by locating copies of their servers closer to their customers. Normally an IP address on the internet refers to only one server in one location. Anycast allows the content provider, for example, The New York Times, to have one server on the east coast, another on the west coast and a third in Europe. When you use your web browser to visit www.nytimes.com, you could be connecting to any of those servers, exactly which one depends on its proximity, which is the least busy, and, theoretically, the one that will give you the best connection.

I have used the nytimes.com website as an example here seeking one that many readers will immediately envisage as being in the iconic Times Tower or Times Annex in Manhattan. My intended point is that on the internet some sites are not constrained by geography, and so, assuming that atencionsanmiguel.org is actually located in San Miguel de Allende is not a certainty. Perhaps a better example of anycast would be Google, but that company has never really been associated with any particular locale in the public’s mind. It has a worldwide network of email servers in more than 50 countries to serve its Gmail users. For security reasons, Google does not disclose the number of servers it uses or their locations. Just be assured that anycast allows you to go to gmail.com from anywhere you are and connect via the closest available server. We end users have no way to control this, and most of the time, we never know this is happening.

So, if Netflix is streaming along at full speed while HBOMax is interrupted by buffering, it is possible that Netflix has located a server closer than HBO has.

Charles Miller is a freelance computer consultant, a frequent visitor to San Miguel since 1981, and now practically a full-time resident. He may be contacted at 415 101 8528 or email FAQ8@SMAguru.com.