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TCP and UDP over IPv6 Jumbograms (RFC2147) Disclosure Number: IPCOM000002703D
Original Publication Date: 1997-May-01
Included in the Prior Art Database: 2000-Sep-13
Document File: 3 page(s) / 6K

Publishing Venue

Internet Society Requests For Comment (RFCs)

Related People

D. Borman: AUTHOR


Status of this Memo

This text was extracted from a ASCII document.
This is the abbreviated version, containing approximately 45% of the total text.

Network Working Group D. Borman

Request for Comments: 2147 Berkeley Software Design, Inc.

Updates: 1883 May 1997

Category: Standards Track

TCP and UDP over IPv6 Jumbograms

Status of this Memo

This document specifies an Internet standards track protocol for the

Internet community, and requests discussion and suggestions for

improvements. Please refer to the current edition of the "Internet

Official Protocol Standards" (STD 1) for the standardization state

and status of this protocol. Distribution of this memo is unlimited.

1. Overview

IPv6 supports datagrams larger than 65535 bytes long, often referred

to as jumbograms, through use of the Jumbo Payload hop-by-hop option

[Deering95]. The UDP protocol has a 16-bit length field that keeps

it from being able to make use of jumbograms, and though TCP does not

have a length field, both the MSS option and the Urgent field are

constrained by 16-bits. This document describes some simple changes

that can be made to allow TCP and UDP to make use of IPv6 jumbograms.

2. UDP Jumbograms

To allow UDP to make use of jumbograms, either the UDP length field

needs to be extended, or it needs to be ignored. Since the size of

the field can't be changed, a length of zero is used to indicate that

it is to be ignored, and the length in the "pseudo-header" is to be

used to determine the true length of the UDP header plus data. This

works because UDP length field includes the UDP header, so the

minimum valid value for this field is 8.

When sending a UDP packet, if and only if the length of the UDP

header plus data is greater than 65,535, set the length field in the

UDP header to zero.

Note 1: The length used in the "pseudo-header" for computing the

UDP checksum is always the true length of the UDP header plus

data, NOT zero [RFC-1883, Section 8.1].

Note 2: An IPv6 packet that carries a UDP packet of length

greater than 65,535 will necessarily carry a Jumbo Payload option

in a Hop-by-Hop Options header [RFC1883, Section 4.3]). The

length field in the Jumbo Payload option contains the length of

the IP packet excluding the IPv6 header, that is, it contains the

length of all extension headers present plus the UDP header plus

the UDP data. The length field in the IPv6 header contains zero

to indicate the presence of the Jumbo Payload option.

If a UDP packet is received with a length field of zero, the length

of the UDP packet is computed from the length field in the Jumbo...