With its unique features of comprehensive and delta sitemaps that provide long-term bandwidth-saving and freshness benefits at little to no operational overhead, the Bing XML Sitemap plugin is a great addition to any webmaster’s tool belt. Available as binaries for IIS and Apache, the plugin is a great solution for your Sitemap needs across platforms. What’s more, the source code released under the Apache 2.0 open source license and you can therefore roll your own binaries or – if so inclined – see line by line how the Bing XML Sitemap plugin does its “Sitemap magic” under the hood.Understanding Bing XML Sitemap Plugin For Webmasters [bing.com]

In addition to collecting your site’s URLs to build a comprehensive Sitemap (or to be exact: a Sitemap Index and one or more XML Sitemaps), the Bing XML Sitemap Plugin generates Sitemaps that contain only those URLs that have changed from the last time they were visited. It is especially this “delta” information that provides additional, long-term benefits to web publishers and their performance in the Bing index (and as a result in Yahoo!, Facebook web search, Windows Smart Search, Siri on iOS7, and all the other cool places powered by Bing!).

Using the built-in signature computation, we are easily able to establish whether or not a page has changed significantly. By publishing that change information into the delta Sitemap we then are able to tell our Bingbot crawlers whether or not a page requires a re-crawl to pick up the changes in our index. This helps reduce bandwidth on both your server as well as on the Bing side, since Bingbot no longer needs to fetch a URL only to discover it hasn’t changed. In fact, in some cases the impact of the Bing XML Sitemap delta technology is so significant that we see up to a 75% reduction in the need to crawl pages of a site.