well, for me I just tell the truth. so ya, depends on how you handle it, as I believe if I bring it up to him at a very young age. He will get use to it as he grows up.
2nd choice, break it to your child when you think he or she is old enough but not during teenage life or what known as rebellious age.
mean while just let her know her father is far away?
Anyway, feel free to msn with me too : email@example.com