Systems and methods for path maximum transmission unit discovery
An information handling system is provided. The information handling system includes a plurality of network devices. One of the plurality of network devices is a source device and another of the plurality of network devices is a destination device. If path maximum transmission unit (PMTU) information for a path between the source device and the destination device is not known, the source device sends a PMTU send packet to the destination device, and the destination device sends a PMTU receive packet with a received PMTU value to the source device. Other associated systems and methods for PMTU discovery are also provided.
1. A first network device in an information handling system, the first network device comprising:
a plurality of ports for sending and receiving packets, at least one of the ports having an associated maximum transmission unit equal to a first value;
one or more processors in communication with the plurality of ports; and
a memory in communication with the one or more processors, the memory including a path maximum transmission unit (PMTU) table that associates each of a plurality of destination addresses with a maximum transmission unit (MTU) value in an MTU field; and
wherein the first network device is configured to:
send a PMTU send packet comprising a first MTU value based on a MTU size for a first immediate hop of a transmission path and a data packet to the destination address when the destination address for the data packet does not have an associated MTU value in an associated MTU field of the PMTU table; and
resend the data packet when a PMTU response is received comprising a second MTU value smaller than the first MTU value.
2. The first network device of claim 1 , wherein the PMTU send packet is sent using Internet Protocol version 6 (IPv6) and includes the first value in a PMTU header of the PMTU send packet.
3. The first network device of claim 1 , wherein the PMTU send packet is decreased in size by at least one intermediate network device before reaching the destination address.
4. The first network device of claim 1 , wherein the first network device is configured to update the associated MTU field upon receipt of a PMTU receive packet from a second network device, the second network device having the destination address.
5. The first network device of claim 1 , wherein the PMTU send packet includes authentication data.
6. The first network device of claim 1 , wherein the destination address is a multicast address associated with a plurality of destination network devices, each of the plurality of destination network devices generating a PMTU receive packet in response to the PMTU send packet, each PMTU receive packet including a third MTU value, the first network device being configured to update the PMTU table to include a lowest MTU value of the third MTU values in the associated MTU field.
7. An information handling system comprising:
a first network device, the first network device being a source device;
a second network device, the second network device being a destination device; and
at least one intermediate network device, the source device, the destination device, and the at least one intermediate network device being part of a plurality of network devices, wherein:
if path maximum transmission unit (PMTU) information for a path between the source device and the destination device is not known, the source device sends a PMTU send packet with a first MTU value, the first MTU value based on a first immediate hop of the path, with a data packet to the destination device, the destination device sends a PMTU receive packet with a received PMTU value to the source device and the source device resends the data packet when the received PMTU value is below the first MTU value.
8. The information handling system of claim 7 , wherein the source device updates a table of PMTU information with the received PMTU value.
9. The information handling system of claim 8 , wherein the PMTU send packet includes an initial PMTU value that is larger than the received PMTU value.
10. The information handling system of claim 7 , wherein the PMTU send packet includes sent authentication data.
11. The information handling system of claim 10 , wherein the PMTU receive packet includes received authentication data and the source device updates a table of PMTU information with the received PMTU value if the received authentication data corresponds to the sent authentication data.
12. The information handling system of claim 7 , wherein the source device periodically sends a PMTU confirmation packet to the destination device, the destination device responding with a corresponding PMTU receive packet.
13. The information handling system of claim 7 , further comprising a multicast address that is an address for a plurality of destination network devices, the plurality of destination network devices including the destination device; and wherein:
the source device is configured to send a respective PMTU send packet to each of the plurality of destination network devices, each destination network device of the plurality responding by sending a respective PMTU receive packet that includes a second MTU value, and to select a lowest MTU value of the second MTU values.
14. A method for determining a maximum transmission unit (MTU) of a path between a source network device and a destination network device, the method comprising:
transmitting a data packet with a path maximum transmission unit (PMTU) send packet with an initial PMTU value, the initial PMTU value based on a first immediate hop of a transmission path, from the source network device to the destination network device;
transmitting a PMTU receive packet from the destination network device to the source network device, the PMTU receive packet including a received PMTU value;
updating a PMTU table on the source network device with the received PMTU value included in the PMTU receive packet; and
resending the data packet when the received PMTU value is below the initial PMTU value.
15. The method of claim 14 , further comprising:
receiving the PMTU send packet at an intermediate network device;
resizing the PMTU send packet so that the PMTU send packet is as small or smaller than an MTU of a next link to create a resized PMTU send packet; and
transmitting the resized PMTU send packet to the destination network device as the PMTU send packet.
16. The method of claim 14 , further comprising:
adding a PMTU header to the PMTU send packet, the PMTU header including the initial PMTU value; and
adding authentication data to the PMTU send packet.
17. The method of claim 14 , further comprising:
including authentication data in the PMTU receive packet before transmitting the PMTU receive packet from the destination network device to the source network device, the authentication data included in the PMTU receive packet corresponding to authentication data included in the PMTU send packet; and
checking the authentication data included in the PMTU receive packet with the authentication data included in the PMTU send packet.
18. The method of claim 14 , further comprising:
decreasing a size of the PMTU send packet at least once before the PMTU send packet is received at the destination network device.
19. The method of claim 14 , further comprising:
forming a PMTU confirmation packet by adding a PMTU header to a data packet;
transmitting the PMTU confirmation packet from the source network device to the destination network device periodically;
transmitting a corresponding PMTU receive packet from the destination network device to the source network device in response to the PMTU confirmation packet.
20. The method of claim 14 , further comprising selecting a lowest MTU value from a plurality of received PMTU values received from a plurality of destination network devices associated with a multicast address.