How is SUP different from existing ping services?
Traditional ping services require feed publishers to ping one or more centralized ping services every time one of their feeds is updated. This is inappropriate for large services that may have thousands or millions of feeds, and is rarely utilized for anything other than blogs. Furthermore, there is no way to know which, if any, ping services are updated by any given feed (it is not discoverable). Also, since ping services are based on feed urls, they can not be used for services, such as Google Reader, which do not wish to publicly expose all of their feed urls. SUP solves these problems by providing an open, discoverable, and standardized way for feed providers to share pings. Since it’s based on opaque tokens known as “SUP-IDs”, publishers do not have to reveal any additional information, and updates can be extremely compact (about 21 bytes each, or 8 bytes with gzip encoding). There is no central ping server, so SUP is practical for both large and small publishers, and everyone has
