help on dsl connection

hHi im using a dsl account, i have a question regarding its connection, you see it has leased obtain (date and time), leased expires (date and time also), just want to ask why is it it is limited only for 2 hours. i.e.
leased obtain 10/14/08 11:00:00 am
leased expires 10/14/08 1:00:00 pm

thats the example, is it on my lan card, on my dsl or what… hope you can help me with this one…
thanks