Inserting, Processing And Deleting IPv6 Extension Headers
draft-bonica-6man-ext-hdr-update-02
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| Document | Type | Active Internet-Draft (individual) | |
|---|---|---|---|
| Author | Ron Bonica | ||
| Last updated | 2020-03-09 (Latest revision 2020-03-06) | ||
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draft-bonica-6man-ext-hdr-update-02
6man R. Bonica
Internet-Draft Juniper Networks
Updates: RFC 8200 (if approved) March 9, 2020
Intended status: Standards Track
Expires: September 10, 2020
Inserting, Processing And Deleting IPv6 Extension Headers
draft-bonica-6man-ext-hdr-update-02
Abstract
This document provides guidance regarding the processing, insertion
and deletion of IPv6 extension headers. It updates RFC 8200.
Status of This Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering
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material or to cite them other than as "work in progress."
This Internet-Draft will expire on September 10, 2020.
Copyright Notice
Copyright (c) 2020 IETF Trust and the persons identified as the
document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 2
3. Updates To RFC 8200 . . . . . . . . . . . . . . . . . . . . . 3
3.1. Original Text . . . . . . . . . . . . . . . . . . . . . . 3
3.2. Updated Text . . . . . . . . . . . . . . . . . . . . . . 3
4. Motivation . . . . . . . . . . . . . . . . . . . . . . . . . 4
5. Security Considerations . . . . . . . . . . . . . . . . . . . 5
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 5
7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 5
8. Normative References . . . . . . . . . . . . . . . . . . . . 5
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 6
1. Introduction
In IPv6 [RFC8200] optional internet-layer information is encoded in
extension headers. As specified by [RFC8200], "extension headers
(except for the Hop-by-Hop Options header) are not processed,
inserted, or deleted by any node along a packet's delivery path,
until the packet reaches the node (or each of the set of nodes, in
the case of multicast) identified in the Destination Address field of
the IPv6 header".
The statement quoted above identifies nodes upon which extension
headers are not processed, inserted or deleted. It does not imply
that extension headers can be processed, inserted or deleted on any
other node along a packet's delivery path.
This document provides guidance regarding the processing, insertion
and deletion of IPv6 extension headers. It clarifies the statement
quoted above and updates [RFC8200].
2. Terminology
The following terms are used in this document:
o Source node - An IPv6 source node accepts data from an upper-layer
protocol, prepends an IPv6 header, and sends the resulting IPv6
packet to a destination node.
o Destination node - An IPv6 destination node receives an IPv6
packet and delivers its payload to an upper-layer protocol. If a
packet contains a Routing header, its destination address may
represent an interface that belongs to a node other than the
destination node.
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o Delivery path - A packet's delivery path is a series of nodes that
a packet traverses on route to its destination. The delivery path
includes the destination node.
o Segment - A segment is a series of links and nodes in a packet's
delivery path. An IPv6 Routing header steers packets from segment
to segment along the delivery path. If a packet contains a
Routing header, its delivery path can contain multiple segments.
If a packet does not contain a Routing header, its delivery path
contains only one segment.
o Segment egress node - A segment egress node terminates a segment.
When a packet arrives at a segment egress node, its IPv6
Destination Address identifies an interface that belongs to the
node. All destination nodes are also segment egress nodes.
3. Updates To RFC 8200
The terms defined in Section 2 of this document should be added to
Section 2 of [RFC8200].
Section 3.1 of this document quotes text from [RFC8200]. That text
should be replaced with the text contained by Section 3.2 of this
document.
3.1. Original Text
"Extension headers (except for the Hop-by-Hop Options header) are not
processed, inserted, or deleted by any node along a packet's delivery
path, until the packet reaches the node (or each of the set of nodes,
in the case of multicast) identified in the Destination Address field
of the IPv6 header.
The Hop-by-Hop Options header is not inserted or deleted, but may be
examined or processed by any node along a packet's delivery path,
until the packet reaches the node (or each of the set of nodes, in
the case of multicast) identified in the Destination Address field of
the IPv6 header. The Hop-by-Hop Options header, when present, must
immediately follow the IPv6 header. Its presence is indicated by the
value zero in the Next Header field of the IPv6 header."
3.2. Updated Text
Source nodes can send packets that include extension headers.
Extension headers are not inserted by subsequent nodes along a
packet's delivery path.
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The Hop-by-Hop Options header, when present, must immediately follow
the IPv6 header. Its presence is indicated by the value zero in the
Next Header field of the IPv6 header.
The Hop-by-Hop Options header can be processed by any node in a
packet's delivery path. The following headers can be processed by
any segment egress node, including the destination node:
o Destination Options header.
o Routing header.
The following headers can be processed by the destination node only:
o The Fragment header.
o The Authentication header.
o The Encapsulating Security Payload header.
Except for the following fields, extension headers are not modified
by nodes along a packet's delivery path:
o The Segments Left field in the Routing header.
o Type-specific data in the Routing header, as allowed by the
relevant Routing type specification.
o Option Data in the Destination Options header.
Extension headers are not deleted by any node along a packet's
delivery path, until the packet reaches the destination node (or each
of the set of destination nodes, in the case of multicast).
Extension headers can be inspected for various purposes (e.g.,
firewall filtering) by any node along a packet's delivery path.
4. Motivation
The following are reasons why extension headers are not inserted by
nodes along a packet's delivery path:
o MTU black holing - Many IPv6 nodes dynamically discover Path MTU
(PMTU) [RFC8201]. Having discovered the PMTU, they send packets
whose size approaches, but does not exceed the PMTU. Adding an
extension header to such a packet can cause MTU black holing.
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o Incompatibility with the IPv6 Authentication Header [RFC4302] -
IPv6 Authentication header processing relies on the immutability
of the Payload Length field in the IPv6 header. When a node along
a packet's delivery path inserts an extension header, it updates
the Payload Length field in the IPv6 header. This causes
Authentication header processing to fail.
o Semantic corruption - Insertion of an extension header can change
the meaning of a packet.
The following are reasons why extension headers are not deleted by
any node along a packet's delivery path, until the packet reaches the
destination node:
o Incompatibility with the IPv6 Authentication Header - IPv6
Authentication header processing relies on the immutability of the
Payload Length field in the IPv6 header. When a node along a
packet's delivery path deletes an extension header, it updates the
Payload Length field in the IPv6 header. This causes
Authentication header processing to fail.
o Semantic corruption - Deletion of an extension header can change
the meaning of a packet.
5. Security Considerations
This document does not introduce any new security considerations.
6. IANA Considerations
This document does not request any IANA actions.
7. Acknowledgements
Thanks to Bob Hinden, Brian Carpenter, Tom Herbert, Fernando Gont and
Jinmei Tatuya for their comments and review.
8. Normative References
[RFC4302] Kent, S., "IP Authentication Header", RFC 4302,
DOI 10.17487/RFC4302, December 2005,
<https://www.rfc-editor.org/info/rfc4302>.
[RFC8200] Deering, S. and R. Hinden, "Internet Protocol, Version 6
(IPv6) Specification", STD 86, RFC 8200,
DOI 10.17487/RFC8200, July 2017,
<https://www.rfc-editor.org/info/rfc8200>.
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[RFC8201] McCann, J., Deering, S., Mogul, J., and R. Hinden, Ed.,
"Path MTU Discovery for IP version 6", STD 87, RFC 8201,
DOI 10.17487/RFC8201, July 2017,
<https://www.rfc-editor.org/info/rfc8201>.
Author's Address
Ron Bonica
Juniper Networks
2251 Corporate Park Drive
Herndon, Virginia 20171
USA
Email: rbonica@juniper.net
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