Hi,

I have reviewed this document as an ops reviewer. This is a well written document.

Some editorial nits:
1. Section 1.3 s/obs-folds/obs-fold
2. Section 2: s/Signture/Signature
3. Remove redundant "the":
  Section 2.1.3  If the value of the the HTTP field in question 
  Section 4.1.  The member's key is the label that uniquely identifies the message signature within the the HTTP message
4. 7.4.2  s/cacheing/caching

Thanks,
Bo Wu