Convoy duty or escort duty, and/or a convoy mission or an escort mission, were a type of duty mission designated for escort vessels to protect convoys, especially during times of war.
During the escort mission, Martok commented that the only thing about convoy duty he hated was the waiting. (DS9: "Sons and Daughters")
Following the First Battle of Chin'toka, the Defiant, under the command of Lieutenant Commander Worf, was assigned to protect more convoys, some containing self-sealing stem bolts. In regards to their mission, Bashir felt that "there should be a law against convoy duty lasting more than ten days." Nog, however, enjoyed guarding convoys, as "it [was] usually much safer than being on the front lines." (DS9: "Image in the Sand")
Worf became more and more discontent with convoy duty, following the death of his wife, Jadzia, and yearned for some combat duty to ensure her a place in Sto-vo-kor. He was later offered a position as first officer under General Martok on a dangerous mission, this after inquiring if Worf liked convoy duty, stating, "I was afraid you might be getting soft." (DS9: "Image in the Sand")