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We will put together a new page outlining more of the concrete considerations around migrating away from that approach, mostly for use by federations needing help crafting advice for their members. In a nutshell, you need to know what profiles your IdP supports, which ones are in use, and what services relying on that port might support or not support in terms of SAML metadata to allow a smooth migration away from it. In the meantime, the SecurityAndNetworking topic contains good information about why the additional port is largely a historical footnote at this point.