IPInfusion Inc. IPv6 fragmentation allows fragments to be sent only by the source of a packet. The Fragment header is used by an IPv6 source to send a packet larger than would fit in the path MTU to its destination. Firewalls generally use 5-tuples to filter out packets. However there are cases where fragmentation can be used to disguise TCP packets from IP filters used in routers and hosts. This document specifies where tiny fragments can be issues.