International Business Machines Corporation

Larry Steven Wise

Lance Warren Russell

David Richard Marquardt

Satyanarayana B Rao

Daniel Edward Badt

Saurabh Desai

Jessie Ann Haug

Gregory Scott Joyce

A local system issues an ICMP echo request packet with a size based on an initial PMTU value corresponding to that of the local system's interface MTU. When an ICMP needfrag error packet is received by the local system, this signifies that the initial PMTU value was too large for packets of corresponding size to be transmitted through the Internet without fragmentation. The value is accordingly decreased by the local system and a next ICMP echo request packet transmitted through the Internet. The process iterates until an ICMP echo request packet is successfully transmitted through the Internet to a target system. In response thereto, the target system transmits an ICMP echo response packet back through the Internet to the local system, thereby indicating that the last-sent ICMP echo request packet from the local system had the correct PMTU value which is thereafter assumed to be the correct PMTU.

System and method for discovering path MTU of internet paths

A local system issues an ICMP echo request packet with a size based on an initial PMTU value corresponding to that of the local system's interface MTU. When an ICMP needfrag error packet is received by the local system, this signifies that the initial PMTU value was too large for packets of corresponding size to be transmitted through the Internet without fragmentation. The value is accordingly decreased by the local system and a next ICMP echo request packet transmitted through the Internet. The process iterates until an ICMP echo request packet is successfully transmitted through the Internet to a target system. In response thereto, the target system transmits an ICMP echo response packet back through the Internet to the local system, thereby indicating that the last-sent ICMP echo request packet from the local system had the correct PMTU value which is thereafter assumed to be the correct PMTU. An MTU application, MTU table, and corresponding application program interfaces and controls are provided in the system for dynamically maintaining PMTU value estimates and for providing next estimates of PMTU. These next estimates are accessed from the table in next ICMP echo request packet transmissions when an ICMP needfrag error packet does not contain an MTU value returned from a router in the Internet.

System and method for dynamically refining PMTU estimates in a

An information handling system includes a number of stations connected in a network configuration, each station including a processor, a storage and an I/O controller, where the processor operates under control of an operating system control program which is divided into a user (application) space and a kernel (system) space, the kernel may include a protocol layer interfacing the user application to a DLPI in the kernel, a DLPI which interfaces between the protocol module and a device driver interface, a device driver and a hardware device for connecting the station to the network. When data is to be received by a station from the network, the following steps are performed in the DLPI: recognize the network interface type (FDDI, Ethernet, Token Ring, etc.); recognize the protocol being used; format data according to the protocol; transmit to a Data Link Services user if address resolution is not required; if address resolution is required, test to determine if the protocol address resolution routine is registered; if registered, transmit data to the Data Link Services user; if not registered, call the default address resolution routine to resolve address and then transmit data to protocol module. When data is to be transmitted from a station to the network, the following steps are performed in the DLPI: recognize the network interface type (FDDI, Ethernet, Token Ring, etc.); recognize the protocol being used; test for registered address resolution routine; if not registered, call the default address resolution routine; if registered, call the registered address resolution routine; and call the device driver to, output the data to be transmitted to the network.

System for user registering an address resolution routine to provide

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Austin, TX, United States of America

Larry Steven Wise