Earth Agencies...specifically US and Offworld ones:
FBI - The Federal Bureau of Investigation. They are responsible for law enforcement at the Federal level.
CIA - Central Intelligence Agency. They are responsible for gathering intelligence using covert means.
NSA - National Security Agency. They are codemakers and codebreakers for the US Gov.
CCIS - Colonial Criminal Investigatory Service. They investigate crimes committed off planet. Their headquarters is on the moon and they have liasons from Earth agencies and other US ones. (Based on NCIS and never conceived of by the EFC Creators or Tribune.)
All Agents working for these Agencies and others not mentioned report to the US 'IntelCzar' Sr. Dir. John Spencer, who reports to U.S. President Hubble Urich, leader of the ANA.
As far as the Earth Agencies go, they are pretty much the same in this show as they are in real life and in the shows they have been used in except for the fact that the Taelons and Atavus were big factors in what changes they Did make.
As for the DCI: The Agents in this Agency do not know this but Hubble also has a secret purpose...track future alien species and by using various means, ascertain their true purpose by hacking in to the files belonging to said hypothetical ship...this is where Sandoval's old Mothership codes come into play...if found to be a theat, even a heavilly Veiled one then they will be turned away. If the new hypothetical species turns threatening immediately then they will be Nuked...hopefully they won't be able to communicate with their world before they are destroyed and it Won't start a war. The agents will find the truth out in time though.