The mirror is not a cache of the identified resource, it is creating a resource with its own identity. Therefore, it could have an independent freshness lifetime.
If you remove the bhttp envelope as #25 suggests, then you will totally lose information about freshness of the original. However, I believe that a mirror only exists to validate the bytes: a client should have a copy of the resource direct from the authoritative source that contains authoritative information about freshness lifetimes. (Because mirrors cannot be used to establish the authenticity of content, only its consistency.)
The mirror could use (or is it abuse?) targeted cache control fields for the purpose of providing information about what the mirror received from the authoritative source, but I'm struggling to come up with a really good reason to pass that information along.
The mirror is not a cache of the identified resource, it is creating a resource with its own identity. Therefore, it could have an independent freshness lifetime.
If you remove the bhttp envelope as #25 suggests, then you will totally lose information about freshness of the original. However, I believe that a mirror only exists to validate the bytes: a client should have a copy of the resource direct from the authoritative source that contains authoritative information about freshness lifetimes. (Because mirrors cannot be used to establish the authenticity of content, only its consistency.)
The mirror could use (or is it abuse?) targeted cache control fields for the purpose of providing information about what the mirror received from the authoritative source, but I'm struggling to come up with a really good reason to pass that information along.