Mechanisms for discovering path maximum transmission unit

A computer program product comprising a non-transitory computer readable storage medium having a computer readable program stored therein, wherein the computer readable program, when executed on an intermediate node of at least one intermediate node along a path from a source node to a destination node, causes the intermediate node to:

• receive an echo request packet from the source node;
• determine whether a size of the echo request packet is greater than a maximum transmission unit (MTU) of a next link of the path from the intermediate node to a next node along the path;
• record the MTU of the next link in the echo request packet in response to the determination that the size of the echo request packet is greater than the MTU of the next link;
• and
• reduce a size of the echo request packet in response to a determination that the size of the echo request packet is greater than the MTU of the next link, wherein:
• a data portion of the echo request packet is filled with one of zero values or a don't care value, and wherein reducing the size of the echo request packet comprises reducing a size of the data portion of the echo request packet,
• the path MTU field of the echo request packet stores a smallest MTU value of all of the links along the path from the source node to the destination node that the echo request packet has so far traversed as a path MTU value which is updated dynamically as the echo request packet is transmitted along the path,
• the intermediate node does not return a packet too big message back to the source node in response to the size of the echo request packet being greater than the MTU of the next link of the path from the intermediate node to a next node along the path, and
• the source node is informed of a difference in a path MTU (PMTU) for the path from the source node to the destination node only by an echo reply packet returned by the destination packet in response to receiving the echo request packet from the source node.

An apparatus, comprising:

• a processor;
• and
• a memory coupled to the processor, wherein the memory comprises instructions which, when executed by the processor, cause the processor to:
• receive an echo request packet from a source node in a data transmission path from the source node to a destination node, the path comprising one or more intermediate nodes, and wherein the apparatus is one of the one or more intermediate nodes;
• determine whether a size of the echo request packet is greater than a maximum transmission unit (MTU) of a next link of the path from the apparatus to a next node along the path;
• record the MTU of the next link in the echo request packet in response to the determination that the size of the echo request packet is greater than the MTU of the next link;
• and
• reduce a size of the echo request packet in response to a determination that the size of the echo request packet is greater than the MTU of the next link, wherein:
• a data portion of the echo request packet is filled with one of zero values or a don't care value, and wherein reducing the size of the echo request packet comprises reducing a size of the data portion of the echo request packet,
• the path MTU field of the echo request packet stores a smallest MTU value of all of the links along the path from the source node to the destination node that the echo request packet has so far traversed as a path MTU value which is updated dynamically as the echo request packet is transmitted along the path,
• the intermediate node does not return a packet too big message back to the source node in response to the size of the echo request packet being greater than the MTU of the next link of the path from the intermediate node to a next node along the path, and
• the source node is informed of a difference in a path MTU (PMTU) for the path from the source node to the destination node only by an echo reply packet returned by the destination packet in response to receiving the echo request packet from the source node.