PMTUD

This document specifies how a UDP Options sender implements Datagram Packetization Layer Path MTU Discovery (DPLPMTUD) as a robust method for Path MTU Discovery (PMTUD). This method uses the UDP Options packetization layer. It allows an application to discover the largest size of datagram that can be sent across a network path. It also provides a way to allow the application to periodically verify the current Maximum Packet Size (MPS) supported by a path and to update this when required.

This document specifies a new IPv6 Hop-by-Hop Option that is used to record the Minimum Path MTU (PMTU) along the forward path between a source host to a destination host. The recorded value can then be communicated back to the source using the return Path MTU field in the Option.

This document specifies Datagram Packetization Layer Path MTU Discovery (DPLPMTUD). This is a robust method for Path MTU Discovery (PMTUD) for datagram Packetization Layers (PLs). It allows a PL, or a datagram application that uses a PL, to discover whether a network path can support the current size of datagram. This can be used to detect and reduce the message size when a sender encounters a packet black hole. It can also probe a network path to discover whether the maximum packet size can be increased. This provides functionality for datagram transports that is equivalent to the PLPMTUD specification for TCP, specified in RFC 4821, which it updates. It also updates the UDP Usage Guidelines to refer to this method for use with UDP datagrams and updates SCTP.

The document provides implementation notes for incorporating Datagram PMTUD into IETF datagram transports or applications that use datagram transports.

This specification updates RFC 4960, RFC 4821, RFC 6951, RFC 8085, and RFC 8261.

This document describes Path MTU Discovery (PMTUD) for IP version 6. It is largely derived from RFC 1191, which describes Path MTU Discovery for IP version 4. It obsoletes RFC 1981.

This document describes a robust method for Path MTU Discovery (PMTUD) that relies on TCP or some other Packetization Layer to probe an Internet path with progressively larger packets. This method is described as an extension to RFC 1191 and RFC 1981, which specify ICMP-based Path MTU Discovery for IP versions 4 and 6, respectively. [STANDARDS-TRACK]

This memo catalogs several known Transmission Control Protocol (TCP) implementation problems dealing with Path Maximum Transmission Unit Discovery (PMTUD), including the long-standing black hole problem, stretch acknowlegements (ACKs) due to confusion between Maximum Segment Size (MSS) and segment size, and MSS advertisement based on PMTU. This memo provides information for the Internet community.

TCP/IPX allows TCP/IP applications to run over IPX networks by letting TCP and UDP run over IPX. And this memo specifies the packet format and operational procedures for running TCP and UDP over IPX. This document defines an Experimental Protocol for the Internet community. This does not specify an Internet standard of any kind.

In the course of reviewing the MTU Discovery protocol for possible elevation to Draft Standard, a specific operational problem was uncovered. The problem results from the optional suppression of ICMP messages implemented in some routers. This memo outlines a modification to this practice to allow the correct functioning of MTU Discovery. This memo provides information for the Internet community. It does not specify an Internet standard.

This memo describes a technique for dynamically discovering the maximum transmission unit (MTU) of an arbitrary internet path. It specifies a small change to the way routers generate one type of ICMP message. For a path that passes through a router that has not been so changed, this technique might not discover the correct Path MTU, but it will always choose a Path MTU as accurate as, and in many cases more accurate than, the Path MTU that would be chosen by current practice. [STANDARDS-TRACK]