Today's word in the Networking ABC's is the letter X.  There really aren't that many words that start with X so my choices for today was limited.  But, luckily for you all, there is one word that stands out as a necessity for application servers hosted behind HTTP proxies.  The "X-Forwarded-For" HTTP header is used to allow a proxy server to inject the true originating IP address of a client connection into the HTTP request allowing the application server to know the callers true identity.

"X" is for X-Forwarded-For