Methods and apparatus for enabling a provider to perform a tracing
procedure to determine the existence forwarding problems within its
network are disclosed. According to one aspect of the present invention,
a method for detecting a forwarding problem within an autonomous system
includes initiating a message from a source node. The message is sent to
a message destination that is an external address relative to the
autonomous system. The method also includes forwarding the message from
the source node along a path to the external address which includes an
intermediate node and a destination node. The message is received on the
destination node through a first path segment of the path. Finally, the
message is removed from the path at the destination node, and a response
that indicates that the intermediate node does not have a forwarding
problem is sent along the first path segment to the source node.