US 7,542,471 B2 · Method of determining path maximum transmission unit

Abstract

Network endpoints using TCP/IP operate to determine the maximum transmission unit (MTU) of the path between them. This determination is done so as to avoid the expensive IP fragmentation that will occur when transitioning links with a smaller MTU size. The standard method of determining the path MTU (PMTU) has several known deficiencies, including: inefficient use of bandwidth as proper operation will likely result in the loss of one or more packets and difficulty of implementation as the reverse channel communication mechanism, reception of ICMP messages indicating the discarding of unfragmentable packets, is frequently blocked by firewalls and other security apparatus. A method of determining the PMTU between intermediate proxies is disclosed that does not require reception of ICMP messages or the inefficient use of bandwidth due to the presumed dropping of packets with valid data.

Claims25

Dependent claims

A method for performing by proxies discovery of a maximum transmission unit of a path between a client and a sewer in a more efficient manner, the method comprising the steps of:

(a) determining, by a first proxy, a size for a path maximum transmission unit (PMTU) for transmitting network packets between a client and a server by increasing a value of the PMTU by a predetermined percentage for each round-trip-time that elapses without receipt of an indication that fragmentation has occurred;
(b) repacketizing, by the first proxy, packets received from the client for transmission to the sewer into packet sizes in accordance with the size of the PMTU;
(c) transmitting, by the first proxy, the repacketized packets to the server;
(d) detecting, by a second proxy, a packet received from transmission of repacketized packets from the first proxy is fragmented;
and
(e) transmitting, by the second proxy to the first proxy in response to the detection, an acknowledgement packet marked with an indicator that fragmentation has occurred.

3 more elements

Dependencies are inferred from the claim text.

Method of determining path maximum transmission unit

Life of this patent

Method of determining path maximum transmission unit

Life of this patent

Abstract

Claims25