Microsoft announced that Xbox Live will be down for maintenance on June 16. Microsoft is turning off the switch starting at 12:01 am/pst of June 16 and is expected to be offline up to 24 hours.
Try not to get too upset with Microsoft, as they are undertaking this maintenance to get ready for a number of new features, these include Facebook, last.fm and Twitter to the paid service.
Anyway, if you want to know how to change the default Maximum Transmission Unit MTU setting?