This page contains information regarding Star Trek: Discovery, and thus may contain spoilers.
Federation Headquarters fleet
When the USS Discovery first arrived at Federation Headquarters in 3189, the protective distortion field was being sustained by the collective energy of a fleet of ships, including one Angelou-class, three Saturn-classes, the USS Reliant-M, the USS Armstrong, three Eisenberg-classes (including the USS Nog), two Courage-classes (including the USS Song), a four-nacelled ship, a two long-nacelled ship, three NCC-325019-types (including the NCC-325019), a Mars-class, and the USS Voyager-J. (DIS: "Die Trying")
Several starships sustained the protective field while Discovery was undergoing a refit, and Fleet Admiral Charles Vance held an assignment briefing for twelve starship captains. These ships included the USS Le Guin and the NCC-325072. (DIS: "Scavengers")
A number of starships later sustained the protective field when Discovery jumped to Kwejian, including at least one Saturn-class, two Eisenberg-classes, a Courage-class, a four-nacelled ship, and a NCC-325019-type ship. (DIS: "The Sanctuary")
When the Viridian and the Discovery (under Osyraa's control) first approached Federation Headquarters and during her negotiations, the fleet of about fifteen ships included at least three Saturn-classes, two Armstrong-types (including the USS Nobel), an Eisenberg-class, two Courage-classes (including the USS Song), two four-nacelled ship, and a NCC-325019-types. (DIS: "There Is A Tide...") By the time the negotiations had failed, the fleet also included an Angelou-class, a two long-nacelled ship, a Mars-class, and the Voyager-J. Several of these ships pursued the Viridian and Discovery along with a fleet of Ni'Var razors, up to the point the Viridian was destroyed. (DIS: "That Hope Is You, Part 2")