In a sachet of cheesecloth or, as I prefer, a tea strainer, combine the allspice berries, cloves, black peppercorns and juniper berries.
Meanwhile, if you are planning to can your cranberries, prepare 6 half-pint jars and lids. Wash all the jars and lids thoroughly with soap and water, and rinse well. Fill your canner with enough water to cover the jars by at least 1 inch and bring to a simmer. Using a pair of canning tongs, lower the jars in gently, tilting them to fill with the hot water. In a small saucepan, keep some water warm but not boiling; place the lids in the water. Have an additional kettle of water on to boil.
Wash the cranberries and pick through them for any stems or damaged berries. Combine the vinegar and sugar in a large, nonreactive saucepan, like stainless steel or enamel. Do not use aluminum or copper. Add the cinnamon sticks and sachet or tea strainer full of spices, and bring the brine to a boil. Add the cranberries and cook until the berries pop and the brine returns to a full rolling boil, about another 5 minutes. Remove from heat, and remove the strainer of spices.
If you are not canning the cranberries, simply ladle them, along with the brine, into clean containers, allow to cool, cover and refrigerate for at least 3 days before eating. Use within 3 months.
If you are canning, fill and close the jars. Using canning tongs, remove the jars from the canner, carefully pouring the water back into the canner. Set next to the cranberries in the saucepan. Turn the heat under the canner to high. Use a slotted spoon to transfer the cranberries into the sterilized jars through a canning funnel, leaving 1/2 inch of headspace at the top.
Then, use a ladle to pour the brine into the jars over the cranberries, again leaving 1/2 inch of headspace. If desired, add one of the cinnamon stick chunks to the jar. Run a clean chopstick around the inside of the jar to dislodge any trapped air. Wipe the rims of the jars with a damp paper towel. Place the lids on, and screw on the rings until just finger-tight.
Using canning tongs, gently transfer the jars to the canner, taking care to keep them vertical. When all the jars are in the canner, there should be at least 1 inch of water covering them; if you need more, add water from the kettle until the jars are sufficiently covered. Bring the water to a full rolling boil; process for 10 minutes.
Using canning tongs, gently remove the jars from the canner and transfer them to a kitchen towel or cooling rack, again keeping them vertical. Do not set hot jars directly onto cool counter surfaces. Leave to cool, undisturbed, for at least 12 hours. If any of the jars do not seal when cool, reprocess using the method above, or refrigerate and use immediately.