[Yum] dag repo problems

[Peter Flynn]

For many months now any attempt to run yum -y update gets me the error 
message

> Cannot open/read repomd.xml file for repository: dag
> failure: repodata/repomd.xml from dag: [Errno 256] No more mirrors to try.
> Error: failure: repodata/repomd.xml from dag: [Errno 256] No more mirrors to try

This happens regardless of the connection I am on (I'm using a laptop)
and while it's easy to work around with --disablerepo I'm just curious
to know when the dag repo will become available again.

 From time to time other repos give similar messages -- for example right
now (10.30pm Eastern) I'm getting

> Cannot find a valid baseurl for repo: updates-released
> Error: Cannot find a valid baseurl for repo: updates-released

but these tend to clear up in a few days. I have seen from various
similar posts that this is always blamed on the user's DNS service,
but as the dag problem happens no matter whose I use, the problem
presumably lies deeper.

Does anyone know the truth?

///Peter