Vietnamese Steak Sandwich

Name: Vietnamese Steak Sandwich
Ingredients: 3 tablespoons fish sauce, (see Note); 3 tablespoons lime juice; 4 teaspoons brown sugar; ½ teaspoon freshly ground pepper; 1 pound flank steak, thinly sliced against the grain; 1 teaspoon canola oil; 6 tablespoons reduced-fat mayonnaise; 3 12-inch baguettes, cut in half and split horizontally; 2 small carrots, shredded or cut into matchsticks; ½ small cucumber, cut into thin spears; ½ cup shredded peeled daikon radish; 3 scallions, trimmed and thinly sliced; ⅓ cup coarsely chopped fresh cilantro