ESP

Estimated Street Price (ESP) is meant developer’s or manufacturer’s estimated price for a particular product for specific area or segment of the market.

Estimate Street Price (ESP) and actual end user’s price are not same always. 

ESP is also used as abbreviation of “Short for Encapsulating Security Payload. Thus the ESP header was developed in order to provide the blend of services pertaining to security issues in Ipv4 as well as in Ipv6.  ESP can also be applied independently as well as along with the IP AH (Authentication Header). The ESP header is put after the IP header and prior to the upper layer protocol header or can also be inserted before the encapsulated IP header. Actually ESP is very useful to enhance secrecy, connectionless integrity, origin authentication etc. etc.