Tannen uses the framing, or envelope, technique - opening and closing an essay with the same reference, quotation, or anecdote. what effect does this have

Using this technique brings the essay or any piece of writing full circle. This is especially important when you wan to stress a specific thing. Also this kind of framing technique is used to generate a stronger impact as the the opening quotation or an anecdote by the end will have a different meaning or would have a stronger impact because its idea has been debated during the essay.