Wrap cinnamon and allspice in cheesecloth, tying into bag with string. Combine cider and cinnamon packet in large saucepan. Bring to simmering over medium-high heat. Reduce heat to medium-low; cook at bare simmer for 10 minutes.
Add cranberry juice. Bring to simmering. Remove cheesecloth bag and discard. Remove pan from heat. Let stand about 10 minutes before serving. Garnish with the orange slices, if desired. Makes 12 servings.