In this poem tennyson refers to both ulysses and achilles what is this technique called in literature
a. alliteration
b. allusion
c. assonance
d. personification

In the poem, Tennyson refers to both Ulysses and Achilles. This technique is called B. allusion in literature.
When you use allusion, you are referring to people or places outside of the novel or essay, or whatever it is you are writing. And since Ulysses and Achilles are not Tennyson's characters, he is alluding to them when he mentions them in his poem.