Patent attributes
An improved traceroute mechanism for use in a label-switched path (LSP) is provided by (a) receiving, by a device in the LSP, an echo request message, wherein the echo request includes a label stack having a least one label, and wherein each of the at least one label has an associated time-to-live (TTL) value; (b) responsive to receiving the echo request, determining by the device, whether or not the device is a penultimate hop popping (PHP) device for the outermost label of the label stack; and (c) responsive to determining that the device is the PHP device for the outermost label of the label stack, (1) generating an echo reply message corresponding to the echo request message, wherein the echo reply message is encoded to indicate that the device is the PHP device for the outermost label of the label stack, and (2) sending the echo reply message back towards a source of the echo request message. Responsive to receiving the echo reply message by the ingress of the LSP defined by the outermost label of the label stack, the ingress may (a) determine whether or not the received echo reply message was sourced from the PHP of the LSP defined by the outermost label of the label stack, and (b) responsive to a determination that the received echo reply message was sourced from the PHP of the LSP defined by the outermost label of the label stack, (1) generate a next echo request in which the TTL value associated with the outermost label in the label stack is increased and in which the TTL value associated with a next to outermost label, if any, in the label stack is incremented, and (2) send the next echo request message on the LSP defined by the outermost label of the label stack.
