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Forcing Fragmentation to Network MTU

Document Type Expired Internet-Draft (ipngwg WG)
Expired & archived
Author Mark P. Andrews
Last updated 1998-01-27
RFC stream Internet Engineering Task Force (IETF)
Intended RFC status (None)
Additional resources Mailing list discussion
Stream WG state WG Document
Document shepherd (None)
IESG IESG state Expired
Consensus boilerplate Unknown
Telechat date (None)
Responsible AD (None)
Send notices to (None)

This Internet-Draft is no longer active. A copy of the expired Internet-Draft is available in these formats:


There exists a class of applications which cannot accept Path MTU discovery [RFC-1981]. This is recommended to be turned on by default for IPv6 [IPV6-SPEC-V2, 4.5, 5]. This document describes an extension to the BSD API [RFC-2133] to inform the kernel when it should be fragmenting at the network MTU rather than trying to discover the path MTU. Path MTU discovery works well when there is a stream of data. However for distributed servers sending small answers larger than the network MTU to many clients the lack of fragmentation in intermediate nodes is anathema. RFC-1981 Section 5.6 recommends that a system utility be provided to: - Specify that Path MTU Discovery not be done on a given path. - Change the PMTU value associated with a given path. This documents specifies how to do the same at the application level to a individual socket.


Mark P. Andrews

(Note: The e-mail addresses provided for the authors of this Internet-Draft may no longer be valid.)