GET /common/global.html HTTP/1.1
User-Agent: Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US; rv:18.104.22.168) Gecko/2009060215 Firefox/3.0.11 (.NET CLR 3.5.30729)
Pragma: akamai-x-cache-on, akamai-x-cache-remote-on, akamai-x-check-cacheable, akamai-x-get-cache-key, akamai-x-get-extracted-values, akamai-x-get-nonces, akamai-x-get-ssl-client-session-id, akamai-x-get-true-cache-key, akamai-x-serial-no
HTTP/1.x 200 OK
Date: Tue, 14 Jul 2009 18:01:27 GMT
X-Cache: TCP_MEM_HIT from a69-174-50-208 (AkamaiGHost/5.7.2-5726413) (-)
The X-Cache headers are related to akamai and here are the different headers you might get to see and their respective meanings,
X-Cache HTTP Response Header
Returned from request using "Pragma: akamai-x-cache-on":
TCP_HIT: The object was fresh in cache and object from disk cache.
TCP_MISS: The object was not in cache, server fetched object from origin.
TCP_REFRESH_HIT: The object was stale in cache and we successfully refreshed with the origin on an If-Modified-Since request.
TCP_REFRESH_MISS: Object was stale in cache and refresh obtained a new object from origin in response to our IF-Modified-Since request.
TCP_REFRESH_FAIL_HIT: Object was stale in cache and we failed on refresh (couldn't reach origin) so we served the stale object.
TCP_IMS_HIT: IF-Modified-Since request from client and object was fresh in cache and served.
TCP_NEGATIVE_HIT: Object previously returned a "not found" (or any other negatively cacheable response) and that cached response was a hit for this new request.
TCP_MEM_HIT: Object was on disk and in the memory cache. Server served it without hitting the disk.
TCP_DENIED: Denied access to the client for whatever reason
TCP_COOKIE_DENY: Denied access on cookie authentication (if centralized or decentralized authorization feature is being used in configuration)
X-Cache-Key HTTP Response Header
Returned from request using "Pragma: akamai-x-get-cache-key"; the value is the internal cache key for the page or object on the Akamai server.