Network Working Group F. L. Templin, Ed.
Internet-Draft Boeing Research & Technology
Intended status: Standards Track 30 July 2023
Expires: 31 January 2024
Identification Extension Options for the Internet Protocol
draft-templin-intarea-ipid-ext-01
Abstract
The Internet Protocol, version 4 (IPv4) header includes a 16 bit
Identification field in all packets, but this length is too small to
ensure reassembly integrity even at moderate data rates in modern
networks. Even for Internet Protocol, version 6 (IPv6), the 32 bit
Identification field may be smaller than desired for some intended
uses. This document addresses these limitations by defining both an
Identification Extension option for IPv4 and a corresponding
Destination Option for IPv6.
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
Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet-
Drafts is at https://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress."
This Internet-Draft will expire on 31 January 2024.
Copyright Notice
Copyright (c) 2023 IETF Trust and the persons identified as the
document authors. All rights reserved.
Templin Expires 31 January 2024 [Page 1]
Internet-Draft IP Identification Extension July 2023
This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents (https://trustee.ietf.org/
license-info) in effect on the date of publication of this document.
Please review these documents carefully, as they describe your rights
and restrictions with respect to this document. Code Components
extracted from this document must include Revised BSD License text as
described in Section 4.e of the Trust Legal Provisions and are
provided without warranty as described in the Revised BSD License.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3
3. Motivation . . . . . . . . . . . . . . . . . . . . . . . . . 3
4. IP ID Extension . . . . . . . . . . . . . . . . . . . . . . . 4
5. IP ID Hyper-Extension . . . . . . . . . . . . . . . . . . . . 5
6. IP ID Ultra-Extension . . . . . . . . . . . . . . . . . . . . 6
7. Requirements . . . . . . . . . . . . . . . . . . . . . . . . 7
8. Implementation Status . . . . . . . . . . . . . . . . . . . . 8
9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 8
10. Security Considerations . . . . . . . . . . . . . . . . . . . 9
11. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 9
12. References . . . . . . . . . . . . . . . . . . . . . . . . . 9
12.1. Normative References . . . . . . . . . . . . . . . . . . 9
12.2. Informative References . . . . . . . . . . . . . . . . . 9
Appendix A. Change Log . . . . . . . . . . . . . . . . . . . . . 10
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 10
1. Introduction
The Internet Protocol, version 4 (IPv4) header includes a 16 bit
Identification in all packets [RFC0791], but this length is too small
to ensure reassembly integrity even at moderate data rates in modern
networks [RFC4963] [RFC6864]. This document defines a new option for
IPv4 that extends the Identification field to 32 bits (i.e., the same
as the length specified for Internet Protocol, version 6 (IPv6)
[RFC8200]) to support reassembly integrity at high data rates.
When an IPv4 packet includes this "Identification Extension" option,
the value encoded in the IPv4 header Identification field represents
the 2 least-significant octets while the option encodes the 2 most-
significant octets of an extended 4-octet IP ID. Hosts and routers
that recognize the option employ it for packet identification
purposes in general and to fortify the IPv4 reassembly procedure in
particular.
Templin Expires 31 January 2024 [Page 2]
Internet-Draft IP Identification Extension July 2023
This specification also supports a "hyper-extended" mode that extends
the Identification field to 64 bits for both IPv4 and IPv6. This
format may be useful for future networks that operate at still higher
data rates, or for source nodes that frequently reset the starting
Identification sequence numbers of flows. Finally, for truly extreme
environments, an optional "ultra-extended" mode that extends the
Identification field to 128 bits is also supported.
2. Terminology
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
"OPTIONAL" in this document are to be interpreted as described in BCP
14 [RFC2119][RFC8174] when, and only when, they appear in all
capitals, as shown here.
This document uses the term "IP" to refer generically to either
protocol version (i.e., IPv4 or IPv6), and uses the term "IP ID" to
refer generically to the IP Identification field whether in simple or
extended form.
3. Motivation
Studies over many decades have shown that transport layer protocols
often achieve greater performance by setting segment sizes that
exceed the path Maximum Transmission Unit (MTU). When the segment
size exceeds the path MTU, IP fragmentation at some layer is a
natural consequence.
A recent study [I-D.templin-dtn-ltpfrag] proved that setting segment
sizes that cause IPv4 packets to exceed the path MTU (thereby
invoking IPv4 fragmentation and reassembly) provides a multiplicative
performance increase at high data rates in comparison with using
smaller segment sizes as long as fragment loss is negligible.
An alternative to fortifying the IPv4 ID was also considered and
examined in which IPv4 packets were first encapsulated in IPv6
headers then subjected to IPv6 fragmentation where a 32 bit
Identification field already exists. While this IPv4-in-IPv6
encapsulation followed by IPv6 fragmentation also showed a
performance increase for larger segment sizes in comparison with
using MTU-sized or smaller segments, the magnitude of increase was
significantly less than for invoking IP fragmentation directly
without first applying encapsulation.
An observation offered without supporting evidence is that common
implementations base both IPv4 and IPv6 fragmentation and reassembly
off a common code base since their algorithms are so similar. It
Templin Expires 31 January 2024 [Page 3]
Internet-Draft IP Identification Extension July 2023
therefore seems reasonable to conclude that IPv4 fragmentation and
reassembly can support higher data rates than IPv6 when full
(uncompressed) headers are used.
For these reasons, it is clear that a robust IP fragmentation and
reassembly service can provide a useful tool for performance
maximization in the Internet. This document therefore presents a
means to fortify the IP ID to support such a service.
4. IP ID Extension
IP ID extension for IPv4 is achieved by introducing a new IPv4
option. This new IPv4 ID Extension (IDEXT) Option begins with an
option-type octet with "copied flag" set to '1', "option class" set
to '00' and "option number" set to TBD. The option-type octet is
followed immediately by an option-length octet set to the constant
value "4".
The option-type is then followed by a 2-octet "ID Extension" field
that (when combined with the 2 least-significant octets found in the
IPv4 packet header Identification field) includes the 2 most-
significant octets of an extended 4-octet IP ID for the packet. The
option format is shown in Figure 1:
+--------+--------+--------+--------+
|100[TBD]|00000100| ID Extension |
+--------+--------+--------+--------+
Type=TBD Length=4
Figure 1: IPv4 ID Extension (IDEXT) Option
When an IPv4 source node (i.e., an original source or an IPv4
encapsulation ingress) wishes to supply a 4-octet extended IP ID for
the packet, it includes an IDEXT option in the IPv4 packet header
options area, i.e., while following the same rules as for including
any IPv4 option. The source next writes the 2 least-significant
octets in the IPv4 header Identification field and writes the 2 most-
significant octets in the "ID Extension" field.
The source then applies source fragmentation if necessary while
including the extended IP ID value. The source copies the ID
Extension option to each resulting fragment and sets or clears the
"Don't Fragment (DF)" flag as desired. (In the limiting case, the
source can set DF to disable network fragmentation and replicate the
conditions experienced for IPv6.)
Templin Expires 31 January 2024 [Page 4]
Internet-Draft IP Identification Extension July 2023
The source then forwards each packet/fragment to the next hop, where
IPv4 forwarding will direct them toward the final destination. If an
IPv4 router on the path needs to apply network fragmentation, it
copies the IDEXT option into each resulting fragment to provide the
final destination with the correct reassembly context.
5. IP ID Hyper-Extension
When an IPv4 source produces a sustained burst of IPv4 packets that
use the same source address, destination address and protocol at
extreme data rates (e.g., in excess of 1Tbps), or when the source
plans to reset the IP ID starting sequence frequently or even pseudo-
randomly, it can optionally "hyper-extend" the IP ID by supplying an
8-octet value instead of a 2/4-octet value.
To apply hyper-extension, the source includes an IDEXT option with
option-type set to TBD the same as above, but with option-length set
to 8 instead of 4 as shown in Figure 2:
+--------+--------+--------+--------+
|100[TBD]|00001000| ID Extension |
+--------+--------+--------+--------+
| ID Hyper-Extension |
+--------+--------+--------+--------+
Figure 2: IDEXT Option with Hyper-Extension
The option-data will then include the 2-octet ID Extension to be
applied to the IPv4 Identification field as above, plus a 4-octet ID
Hyper-Extension that includes the 4 most significant octets of the
hyper-extended ID. The combined 8-octet IP ID can then fit properly
within the longest word length for modern 64-bit architectures.
Techniques that improve IPv4 often also apply in a corresponding
fashion for IPv6 (and vice-versa). This document therefore defines a
new IPv6 ID Extension Destination Option for IPv6 that extends the
base Identification value found in the IPv6 Fragment Header. The
source inserts the Destination Option immediately before the Fragment
Header (or Routing Header, if present)) and the destination processes
the option only if the Fragment Header is also present. The IPv6 ID
Extension Option format is shown in Figure 3:
Templin Expires 31 January 2024 [Page 5]
Internet-Draft IP Identification Extension July 2023
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Option Type | Opt Data Len |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| IPv6 ID Hyper-Extension |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Option Type 8-bit value TBD2.
Opt Data Len 8-bit value 4.
IPv6 ID Extension 32-bit unsigned integer. The option data
includes a 4-octet extension to the (4-octet)
IPv6 Fragment Header Identification field.
Figure 3: IPv6 ID Extension Option
All aspects of applying and processing the IPv6 ID Extension option
follow exactly the same as for IPv4, with the exception that only
source fragmentation is permitted since network fragmentation is
deprecated in IPv6.
6. IP ID Ultra-Extension
To support truly extreme environments (e.g., where IP ID duplication
in ultra-high speed networks carries severe consequences and/or where
sophisticated adversaries actively try to guess IP ID values), an
optional "ultra-extension" mode is also supported that extends the IP
ID to 16 octets.
Nodes invoke ultra-extension mode by replacing the "Hyper-Extension"
fields in Figure 2 and Figure 3 with an "Ultra-Extension" field
containing the most significant 12 octets of a 16-octet ultra-
extended IP ID. For IPv4, the option sets option-length to 16 and,
for IPv6, the option sets Opt Data Len to 12.
Nodes process the IP ID ultra-extension format the same as for the
other extension forms, except that the option contains 12 octets in
network byte order that form the most significant octets of a 16
octet IP ID. The combined 16-octet IP ID can then fit properly
within two words under the longest word length for modern 64-bit
architectures.
Templin Expires 31 January 2024 [Page 6]
Internet-Draft IP Identification Extension July 2023
Since processing two long words instead of a single word may require
extra machine instructions even in modern architectures, and since
transporting longer ultra-extended IP IDs consumes additional network
bandwidth, ultra-extended mode performance may be less than for
extended/hyper-extended modes under modern day architectures.
However, these issues may be overcome by future architectures that
support 128-bit instruction sets natively over ultra-high speed
networks.
Due to the added complexity and overhead, nodes are not required to
support ultra-extended mode natively. Destination nodes that
implement the extended/hyper-extended modes but do not support ultra-
extended mode unconditionally drop packets that include an ultra-
extended IP ID. After first testing for basic IP ID extension
support (see: Section 7) source nodes can therefore test for ultra-
extension support by sending a 'ping' packet that includes an ultra-
extended option. If the source receives a ping response, it can
begin sending packets with ultra-extended IP IDs.
7. Requirements
IPv4 routers MUST forward without dropping any packets with IPv4
option-type TBD while copying the option during (router)
fragmentation, and IPv6 routers MUST forward without dropping any
packets with IPv6 Option Type TBD2.
Destinations that recognize IPv4 option-type TBD and/or IPv6 Option
Type TBD2 MUST accommodate packets that include all simple, extended
and hyper-extended IP ID formats based on any 2-, 4- or 8-octet value
included by the source. Destinations that implement the OPTIONAL
ultra-extended IP ID format MUST accommodate packets with ultra-
extended 16-octet IP IDs, while destinations that implement only the
required extended IP ID formats MUST drop packets that include an
ultra-extended IP ID.
Sources MUST transmit and destinations MUST process the octets of the
extended IP ID in network byte order with the base IP header
Identification field containing the least significant octets, the ID
Extension field (when present) containing the next most significant
octets and the ID Hyper/Ultra-Extension field (when present)
containing the most significant octets. When either or both
extension fields are absent, implementations consider their values to
be "0".
Since the option is included only by the source and reassembly is
performed only by the destination, the source can test whether the
path and/or destination are compliant by sending a fragmented 'ping'
packet with the same IP Identification in all fragments but with two
Templin Expires 31 January 2024 [Page 7]
Internet-Draft IP Identification Extension July 2023
or more fragments containing different pseudo-random values in the
combined extension/hyper-extension fields of an ID extension option
(the source can first send an ordinary 'ping' to test reachability).
If the destination responds to a fragmented ping sent with mismatched
hyper-extended IP IDs (proving that reassembly was performed without
honoring the option) the source can infer that the destination and/or
some router on the path does not recognize the option.
Option formats supported by this specification include only the
mandatory-to-implement extended/hyper-extended formats and optional
ultra-extended format. The formats are differentiated by the option-
length value for IPv4 or the Option Length value for IPv6. Future
documents may specify additional formats that use different option
length values.
Note: IP fragmentation can only be applied for packet lengths up to a
maximum of 65535 octets. IP parcels and advanced jumbos provide a
means for efficiently packaging and shipping multiple large segments
or truly large singleton segments in IP packets that may exceed this
size [I-D.templin-intarea-parcels].
8. Implementation Status
In progress.
9. IANA Considerations
IANA is requested to assign a new IPv4 Option named "IDEXT" in the
'ip-parameters' registry (registration procedures not defined). The
option sets "Copy" to '1', "Class" to '00' and "Number" to TBD.
IANA is further requested to assign a new IPv6 Destination Option
with description "IPv6 ID Extension" in the 'ipv6-parameters'
registry (registration procedures IESG Approval, IETF Review or
Standards Action). The option sets "act" to '00', "chg" to '0' and
"rest" to TBD2.
Note: IANA could alternatively re-assign a deprecated IPv4 option
instead of allocating a new option; for example, the "Extended
Internet Protocol (EIP)" option which still appears as option
"Number" 17 with "Value" 145. Earlier works formalized deprecation
of the EIP option [RFC6814], while [RFC7126] took the further step of
advising routers to drop packets that include the option.
Templin Expires 31 January 2024 [Page 8]
Internet-Draft IP Identification Extension July 2023
10. Security Considerations
All aspects of IP security apply equally to this document, which does
not introduce any new vulnerabilities. Moreover, when employed
correctly the mechanisms in this document robustly address a known
IPv4 reassembly integrity concern [RFC4963] and also provide an
advanced degree of packet uniqueness assurance.
11. Acknowledgements
This work was inspired by continued DTN performance studies.
12. References
12.1. Normative References
[RFC0791] Postel, J., "Internet Protocol", STD 5, RFC 791,
DOI 10.17487/RFC0791, September 1981,
<https://www.rfc-editor.org/info/rfc791>.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997,
<https://www.rfc-editor.org/info/rfc2119>.
[RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
May 2017, <https://www.rfc-editor.org/info/rfc8174>.
[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>.
12.2. Informative References
[I-D.templin-dtn-ltpfrag]
Templin, F., "LTP Fragmentation", Work in Progress,
Internet-Draft, draft-templin-dtn-ltpfrag-10, 5 May 2023,
<https://datatracker.ietf.org/doc/html/draft-templin-dtn-
ltpfrag-10>.
[I-D.templin-intarea-parcels]
Templin, F., "IP Parcels and Advanced Jumbos", Work in
Progress, Internet-Draft, draft-templin-intarea-parcels-
66, 26 July 2023, <https://datatracker.ietf.org/doc/html/
draft-templin-intarea-parcels-66>.
Templin Expires 31 January 2024 [Page 9]
Internet-Draft IP Identification Extension July 2023
[RFC4963] Heffner, J., Mathis, M., and B. Chandler, "IPv4 Reassembly
Errors at High Data Rates", RFC 4963,
DOI 10.17487/RFC4963, July 2007,
<https://www.rfc-editor.org/info/rfc4963>.
[RFC6814] Pignataro, C. and F. Gont, "Formally Deprecating Some IPv4
Options", RFC 6814, DOI 10.17487/RFC6814, November 2012,
<https://www.rfc-editor.org/info/rfc6814>.
[RFC6864] Touch, J., "Updated Specification of the IPv4 ID Field",
RFC 6864, DOI 10.17487/RFC6864, February 2013,
<https://www.rfc-editor.org/info/rfc6864>.
[RFC7126] Gont, F., Atkinson, R., and C. Pignataro, "Recommendations
on Filtering of IPv4 Packets Containing IPv4 Options",
BCP 186, RFC 7126, DOI 10.17487/RFC7126, February 2014,
<https://www.rfc-editor.org/info/rfc7126>.
Appendix A. Change Log
<< RFC Editor - remove prior to publication >>
Differences from earlier versions:
* First draft publication.
Author's Address
Fred L. Templin (editor)
Boeing Research & Technology
P.O. Box 3707
Seattle, WA 98124
United States of America
Email: fltemplin@acm.org
Templin Expires 31 January 2024 [Page 10]