PLZ HELP!

I know the device is satire but how:

Read the following Shakespearean sonnet.

My mistress' eyes are nothing like the sun;
Coral is far more red than her lips' red;
If snow be white, why then her breasts are dun;
If hairs be wires, black wires grow on her head.;
I have seen roses damasked, red and white,
But no such roses see I in her cheeks;
And in some perfumes is there more delight
Than in the breath that from my mistress reeks.

I love to hear her speak, yet well I know

That music hath a far more pleasing sound;

I grant I never saw a goddess go;
My mistress when she walks treads on the ground.
And yet, by heaven, I think my love as rare
As any she belied with false compare.

The lines "My mistress' eyes are nothing like the sun; / Coral is far more red than her lips' red; / If snow be white, why then her breasts are dun; / If hairs be wires, black wires grow on her head" employ a humor device.

Identify the device used and discuss its effect on the meaning and tone of the poem.