Shepherd writeup

Technical Summary

This simple document defines a new request header field for HTTP:
CDN-Loop. CDN-Loop addresses an operational need that occurs when an
HTTP request is intentionally forwarded between CDNs but then is
accidentally re-routed back into the original CDN causing a non
terminating loop. The new header field is used to identify the error
and terminate the loop.

The document was co-authored by employees of three different large CDNs.

Working Group Summary

The group was largely in agreement that this was a sensible solution
and consensus was quickly reached. About 35 emails were exchanged on
the document. A majority of the comments dealt with the relationship
between CDN-Loop and the existing Via header field. Consensus was
reached that Via was essentially 'burned' at this point and not
operationally suitable for that purpose.

Document Quality

Participation in the document's review and development was sufficient
given the tight scope of the document. In addition to the 3
primary authors, 9 other individuals weighed in with comments and
reviews. This represented contributors from both clients, servers, and

The Working Group Last Call requested information on any plans to
implement. In addition to the author's CDNs one other CDN stepped
forward at that time with interest. There has been at least one
pre-release deployment already.


Tommy Pauly is the document shepherd; Alexey Melnikov is the
responsible Area Director.