Internet Area WG J. Touch
Internet Draft USC/ISI
Updates: 791,1122,2003 September 16, 2011
Intended status: Proposed Standard
Expires: March 2012
Updated Specification of the IPv4 ID Field
draft-ietf-intarea-ipv4-id-update-04.txt
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Abstract
The IPv4 Identification (ID) field enables fragmentation and
reassembly, and as currently specified is required to be unique
within the maximum lifetime for all datagrams with a given
source/destination/protocol tuple. If enforced, this uniqueness
requirement would limit all connections to 6.4 Mbps. Because
individual connections commonly exceed this speed, it is clear that
existing systems violate the current specification. This document
updates the specification of the IPv4 ID field in RFC791, RFC1122,
and RFC2003 to more closely reflect current practice and to more
closely match IPv6 so that the field's value is defined only when a
datagram is actually fragmented. It also discusses the impact of
these changes on how datagrams are used.
Table of Contents
1. Introduction...................................................3
2. Conventions used in this document..............................3
3. The IPv4 ID Field..............................................3
4. Uses of the IPv4 ID Field......................................4
5. Background on IPv4 ID Reassembly Issues........................5
6. Updates to the IPv4 ID Specification...........................6
6.1. IPv4 ID Used Only for Fragmentation.......................7
6.2. Encourage Safe IPv4 ID Use................................8
6.3. IPv4 ID Requirements That Persist.........................8
7. Impact on Datagram Use.........................................9
8. Updates to Existing Standards..................................9
8.1. Updates to RFC 791.......................................10
8.2. Updates to RFC 1122......................................10
8.3. Updates to RFC 2003......................................11
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9. Impact on NATs/ASMs, Rewriting Devices, and Tunnel Ingresses..11
10. Impact on Header Compression.................................12
11. Security Considerations......................................13
12. IANA Considerations..........................................13
13. References...................................................13
13.1. Normative References....................................13
13.2. Informative References..................................14
14. Acknowledgments..............................................15
1. Introduction
In IPv4, the Identification (ID) field is a 16-bit value that is
unique for every datagram for a given source address, destination
address, and protocol, such that it does not repeat within the
Maximum Segment Lifetime (MSL) [RFC791][RFC1122]. As currently
specified, all datagrams between a source and destination of a given
protocol must have unique IPv4 ID values over a period of this MSL,
which is typically interpreted as two minutes (120 seconds). This
uniqueness is currently specified as for all datagrams, regardless of
fragmentation settings.
Uniqueness of the IPv4 ID is commonly violated by high speed devices;
if strictly enforced, it would limit the speed of a single protocol
between two IP endpoints to 6.4 Mbps for typical MTUs of 1500 bytes
[RFC4963]. It is common for a single connection to operate far in
excess of these rates, which strongly indicates that the uniqueness
of the IPv4 ID as specified is already moot.
This document updates the specification of the IPv4 ID field to more
closely reflect current practice, and to include considerations taken
into account during the specification of the similar field in IPv6.
2. Conventions used in this document
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in RFC-2119 [RFC2119].
In this document, the characters ">>" proceeding an indented line(s)
indicates a requirement using the key words listed above. This
convention aids reviewers in quickly identifying or finding this
document's explicit requirements.
3. The IPv4 ID Field
IP supports datagram fragmentation, where large datagrams are split
into smaller components to traverse links with limited maximum
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transmission units (MTUs). Fragments are indicated in different ways
in IPv4 and IPv6:
o In IPv4, fragments are indicated using four fields of the basic
header: Identification (ID), Fragment Offset, a "Don't Fragment"
flag (DF), and a "More Fragments" flag (MF) [RFC791]
o In IPv6, fragments are indicated in an extension header that
includes an ID, Fragment Offset, and M (more fragments) flag
similar to their counterparts in IPv4 [RFC2460]
IPv4 and IPv6 fragmentation differs in a few important ways. IPv6
fragmentation occurs only at the source, so a DF bit is not needed to
prevent downstream devices from initiating fragmentation (i.e., IPv6
always acts as if DF=1). The IPv6 fragment header is present only
when a datagram has been fragmented, so the ID field is not present
for non-fragmented datagrams, and thus is meaningful only for
fragments. Finally, the IPv6 ID field is 32 bits, and required unique
per source/destination address pair for IPv6, whereas for IPv4 it is
only 16 bits and required unique per source/destination/protocol
triple.
This document focuses on the IPv4 ID field issues, because in IPv6
the field is larger and present only in fragments.
4. Uses of the IPv4 ID Field
The IPv4 ID field was originally intended for fragmentation and
reassembly [RFC791]. Within a given source address, destination
address, and protocol, fragments of an original datagram are matched
based on their IPv4 ID. This requires that IDs are unique within the
address/protocol triple when fragmentation is possible (e.g., DF=0)
or when it has already occurred (e.g., frag_offset>0 or MF=1).
The IPv4 ID field can be useful for other purposes. The field has
been proposed as a way to detect and remove duplicate datagrams,
e.g., at congested routers (noted in Sec. 3.2.1.5 of [RFC1122],
proposed experimentally in Simplified Multicast Forwarding [Ma11]).
It can similarly be used at end hosts to reduce the impact of
duplication on higher-layer protocols (e.g., additional processing in
TCP, or the need for application-layer duplicate suppression in UDP).
The IPv4 ID field is also used in some debugging tools to correlate
datagrams measured at various locations along a network path. This is
already insufficient in IPv6 because unfragmented datagrams lack an
ID, so these tools are already being updated to avoid such reliance
on the ID field.
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The ID clearly needs to be unique (within MSL, within the
src/dst/protocol tuple) to support fragmentation and reassembly, but
not all packets are fragmented or allow fragmentation. This document
deprecates non-fragementation uses, allowing the ID to be repeated
(within MSL, within the src/dst/protocol tuple) in those cases.
5. Background on IPv4 ID Reassembly Issues
The following is a summary of issues with IPv4 fragment reassembly in
high speed environments raised previously [RFC4963]. Readers are
encouraged to consult RFC 4963 for a more detailed discussion of
these issues.
With the maximum IPv4 datagram size of 64KB, a 16-bit ID field that
does not repeat within 120 seconds means that the aggregate of all
TCP connections of a given protocol between two IP endpoints is
limited to roughly 286 Mbps; at a more typical MTU of 1500 bytes,
this speed drops to 6.4 Mbps [RFC4963]. This limit currently applies
for all IPv4 datagrams within a single protocol (i.e., the IPv4
protocol field) between two IP addresses, regardless of whether
fragmentation is enabled or inhibited, and whether a datagram is
fragmented or not.
IPv6, even at typical MTUs, is capable of 18.7 Tbps with
fragmentation between two IP endpoints as an aggregate across all
protocols, due to the larger 32-bit ID field (and the fact that the
IPv6 next-header field, the equivalent of the IPv4 protocol field, is
not considered in differentiating fragments). When fragmentation is
not used the field is absent, and in that case IPv6 speeds are not
limited by the ID field uniqueness.
Note also that 120 seconds is only an estimate on the maximum
datagram lifetime. It is loosely based on half maximum value of the
IP TTL field (255), measured in seconds, because the TTL is
decremented not only for each hop, but also for each second a
datagram is held at a router (as implied in [RFC791]). Network delays
are incurred in other ways, e.g., satellite links, which can add
seconds of delay even though the TTL is often not decremented by a
corresponding amount. There is thus no enforcement mechanism to
ensure that datagrams older than 120 seconds are discarded.
Wireless Internet devices are frequently connected at speeds over 54
Mbps, and wired links of 1 Gbps have been the default for several
years. Although many end-to-end transport paths are congestion
limited, these devices easily achieve 100+ Mbps application-layer
throughput over LANs (e.g., disk-to-disk file transfer rates), and
numerous throughput demonstrations have been performed with COTS
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systems over wide-area paths at these speeds for over a decade. This
strongly suggests that IPv4 ID uniqueness has been moot for a long
time.
6. Updates to the IPv4 ID Specification
This document updates the specification of the IPv4 ID field in three
distinct ways, as discussed in subsequent subsections:
o Use the IPv4 ID field only for fragmentation
o Avoiding a performance impact when the IPv4 ID field is used
o Encourage safe operation when the IPv4 ID field is used
There are two kinds of datagrams used in the following discussion,
named as follows:
o Atomic datagrams: datagrams not yet fragmented (MF=0 and fragment
offset=0) and for which further fragmentation has been inhibited
(DF=1), i.e., as a mathematical expression (equals is ==, logical
'and' is &&, logical 'or' is ||, greater than is >, logical 'not'
is ~, and parenthesis function typically):
(DF==1)&&(MF==0)&&(frag_offset==0)
o Non-atomic datagrams: datagrams which have either already been
fragmented, i.e.:
(MF=1)||(frag_offset>0)
or for which fragmentation remains possible:
(DF==0)
I.e., non-atomic datagrams can be expressed in two equivalent
tests:
(DF==0)||(MF==1)||(frag_offset>0)
which can also be expressed as follows, using DeMorgan's Law and
other identities:
~((DF==1)&&(MF==0)&&(frag_offset==0))
Note that this final expression is the same as "not(atomic)".
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6.1. IPv4 ID Used Only for Fragmentation
Although RFC1122 suggests the IPv4 ID field has other uses, and it is
currently being considered for the experimental Simplfied Mulitcast
Forwarding (SMF) protocol [Ma11], this document asserts that this
field's value is defined only for fragmentation and reassembly:
o >> IPv4 ID field MUST NOT be used for purposes other than
fragmentation and reassembly.
SMF includes non-ID hash-based duplicate packet detection for cases
where the ID field is absent (IPv6), and already defines these for
IPv4, where it should be preferred to ID-based duplicate detection.
In atomic datagrams, the IPv4 ID field has no meaning, and thus can
be set to an arbitrary value, i.e., the requirement for non-repeating
IDs within the address/protocol triple is no longer required for
atomic datagrams:
o >> Originating sources MAY set the IPv4 ID field of atomic
datagrams to any value.
Second, all network nodes, whether at intermediate routers,
destination hosts, or other devices (e.g., NATs and other address
sharing mechanisms, firewalls, tunnel egresses), cannot rely on the
field:
o >> All devices that examine IPv4 headers MUST ignore the IPv4 ID
field of atomic datagrams.
The IPv4 ID field is thus meaningful only for non-atomic datagrams -
datagrams that have either already been fragmented, or those for
which fragmentation remains permitted. Atomic datagrams are detected
by their DF, MF, and fragmentation offset fields as explained in
Section 6, because such a test is completely backward compatible;
this document thus does not reserve any IPv4 ID values, including 0,
as distinguished.
Deprecating the use of the IPv4 ID field for non-reassembly uses
should have little - if any - impact. IPv4 IDs are already frequently
repeated, e.g., over even moderately fast connections. Duplicate
suppression was only suggested [RFC1122], and no impacts of IPv4 ID
reuse have been noted. Routers are not required to issue ICMPs on any
particular timescale, and so IPv4 ID repetition should not have been
used for validation, and again repetition occurs and probably could
have been noticed [RFC1812]. ICMP relaying at tunnel ingresses is
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specified to use soft state rather than a datagram cache, and should
have been noted if the latter for similar reasons [RFC2003].
6.2. Encourage Safe IPv4 ID Use
This document makes further changes to the specification of the IPv4
ID field and its use to encourage its safe use as corollary
requirements changes as follows.
RFC 1122 discusses that TCP retransmits a segment it may be possible
to reuse the IPv4 ID (see Section 8.2). This can make it difficult
for a source to avoid IPv4 ID repetition for received fragments. RFC
1122 concludes that this behavior "is not useful"; this document
formalizes that conclusion as follows:
o >> The IPv4 ID of non-atomic datagrams MUST NOT be reused when
sending a copy of an earlier non-atomic datagram.
RFC 1122 also suggests that fragments can overlap [RFC1122]. Such
overlap can occur if successive retransmissions are fragmented in
different ways but the same reassembly IPv4 ID. This overlap is noted
as the result of reusing IPv4 IDs when retransmitting datagrams,
which this document deprecates. However, it is also the result of in-
network packet duplication, which can still occur. As a result this
document does not change the need to support overlapping fragments.
6.3. IPv4 ID Requirements That Persist
This document does not relax the IPv4 ID field uniqueness
requirements of [RFC791] for non-atomic datagrams, i.e.:
o >> Sources emitting non-atomic datagrams MUST NOT repeat IPv4 ID
values within one MSL for a given source address/destination
address/protocol triple.
Such sources include originating hosts, tunnel ingresses, and NATs
(including other address sharing mechanisms) (see Section 9).
This document does not relax the requirement that all network devices
honor the DF bit, i.e.:
o >> IPv4 datagrams whose DF=1 MUST NOT be fragmented.
o >> IPv4 datagram transit devices MUST NOT clear the DF bit.
In specific, DF=1 prevents fragmenting atomic datagrams. DF=1 also
prevents further fragmenting received fragments. In-network
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fragmentation is permitted only when DF=0; this document does not
change that requirement.
7. Impact on Datagram Use
The following is a summary of the recommendations that are the result
of the previous changes to the IPv4 ID field specification.
Because atomic datagrams can use arbitrary IPv4 ID values, the ID
field no longer imposes a performance impact in those cases. However,
the performance impact remains for non-atomic datagrams. As a result:
o >> Sources of non-atomic IPv4 datagrams MUST rate-limit their
output to comply with the ID uniqueness requirements.
Such sources include, in particular, DNS over UDP [RFC2671].
Because there is no strict definition of the MSL, reassembly hazards
exist regardless of the IPv4 ID reuse interval or the reassembly
timeout. As a result:
o >> Higher layer protocols SHOULD verify the integrity of IPv4
datagrams, e.g., using a checksum or hash that can detect
reassembly errors (the UDP checksum is weak in this regard, but
better than nothing), as in SEAL [RFC5320].
Additional integrity checks can be employed using tunnels, as in
SEAL, IPsec, or SCTP [RFC4301][RFC4960][RFC5320]. Such checks can
avoid the reassembly hazards that can occur when using UDP and TCP
checksums [RFC4963], or when using partial checksums as in UDP-Lite
[RFC3828]. Because such integrity checks can avoid the impact of
reassembly errors:
o >> Sources of non-atomic IPv4 datagrams using strong integrity
checks MAY reuse the ID within MSL values smaller than is typical.
Note, however, that such more frequent reuse can still result in
corrupted reassembly and poor throughput, although it would not
propagate reassembly errors to higher layer protocols.
8. Updates to Existing Standards
The following sections address the specific changes to existing
protocols indicated by this document.
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8.1. Updates to RFC 791
RFC 791 states that:
The originating protocol module of an internet datagram sets the
identification field to a value that must be unique for that
source-destination pair and protocol for the time the datagram
will be active in the internet system.
And later that:
Thus, the sender must choose the Identifier to be unique for this
source, destination pair and protocol for the time the datagram
(or any fragment of it) could be alive in the internet.
It seems then that a sending protocol module needs to keep a table
of Identifiers, one entry for each destination it has communicated
with in the last maximum datagram lifetime for the internet.
However, since the Identifier field allows 65,536 different
values, some host may be able to simply use unique identifiers
independent of destination.
It is appropriate for some higher level protocols to choose the
identifier. For example, TCP protocol modules may retransmit an
identical TCP segment, and the probability for correct reception
would be enhanced if the retransmission carried the same
identifier as the original transmission since fragments of either
datagram could be used to construct a correct TCP segment.
This document changes RFC 791 as follows:
o IPv4 ID uniqueness applies to only non-atomic datagrams.
o Retransmitted non-atomic IPv4 datagrams are no longer permitted to
reuse the ID value.
8.2. Updates to RFC 1122
RFC 1122 states that:
3.2.1.5 Identification: RFC-791 Section 3.2
When sending an identical copy of an earlier datagram, a
host MAY optionally retain the same Identification field in
the copy.
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DISCUSSION:
Some Internet protocol experts have maintained that when a
host sends an identical copy of an earlier datagram, the new
copy should contain the same Identification value as the
original. There are two suggested advantages: (1) if the
datagrams are fragmented and some of the fragments are lost,
the receiver may be able to reconstruct a complete datagram
from fragments of the original and the copies; (2) a
congested gateway might use the IP Identification field (and
Fragment Offset) to discard duplicate datagrams from the
queue.
This document changes RFC 1122 as follows:
o The IPv4 ID field is no longer permitted to be used for duplicate
detection. This applies both atomic and non-atomic datagrams.
o Retransmitted non-atomic IPv4 datagrams are no longer permitted to
reuse the ID value.
8.3. Updates to RFC 2003
This document updates how IPv4-in-IPv4 tunnels create IPv4 ID values
for the IPv4 outer header [RFC2003], but only in the same way as for
any other IPv4 datagram source.
9. Impact on NATs/ASMs, Rewriting Devices, and Tunnel Ingresses
Network address translators (NATs) and address/port translators
(NAPTs) rewrite IP fields, and tunnel ingresses (using IPv4
encapsulation) copy and modify some IPv4 fields, so all are
considered sources, as do any devices that rewrite any portion of the
source address, destination address, protocol, and ID tuple for any
datagrams [RFC3022]. This is also true for other address sharing
mechanisms (ASMs), including to include 4rd, IVI, and others in the
"A+P" (address plus port) family [Bo11] [De11] [RFC6219]. It is
equally true for any other packet rewriting mechanism. As a result,
they are subject to all the requirements of any source, as has been
noted.
NATs/ASMs/rewriters present a particularly challenging situation for
fragmentation. Because they overwrite portions of the reassembly
tuple in both directions, they can destroy tuple uniqueness and
result in a reassembly hazard. Whenever IPv4 source address,
destination address, or protocol fields are modified, a
NAT/ASM/rewriter needs to ensure that the ID field is generated
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appropriately, rather than simply copied from the incoming datagram.
In specific:
o >> Address sharing or rewriting devices MUST ensure that the IPv4
ID field of datagrams whose address or protocol are translated
comply with requirements as if the datagram were sourced by that
device.
This compliance means that the IPv4 ID field of non-atomic datagrams
translated at a NAT/ASM/rewriter needs to obey the uniqueness
requirements of any IPv4 datagram source. Unfortunately, fragments
already violate that requirement, as they repeat an IPv4 ID within
the MSL for a given source address, destination address, and protocol
triple.
Such problems with transmitting fragments through NATs/ASMs/rewriters
are already known; translation is based on the transport port number,
which is present in only the first fragment anyway [RFC3022]. This
document underscores the point that not only is reassembly (and
possibly subsequent fragmentation) required for translation, it can
be used to avoid issues with IPv4 ID uniqueness.
Note that NATs/ASMs already need to exercise special care when
emitting datagrams on their public side, because merging datagrams
from many sources onto a single outgoing source address can result in
IPv4 ID collisions. This situation precedes this document, and is not
affected by it. It is exacerbated in large-scale, so-called "carrier
grade" NATs [Pe11].
Tunnel ingresses act as sources for the outermost header, but tunnels
act as routers for the inner headers (i.e., the datagram as arriving
at the tunnel ingress). Ingresses can always fragment as originating
sources of the outer header, because they control the uniqueness of
that IPv4 ID field and the value of DF on the outer header
independent of those values on the inner (arriving datagram) header.
10. Impact on Header Compression
Header compression algorithms already accommodate various ways in
which the IPv4 ID changes between sequential datagrams [RFC1144]
[RFC2508] [RFC3545] [RFC5225]. Such algorithms currently assume that
the IPv4 ID is preserved end-to-end. Some algorithms already allow
assuming the ID does not change (e.g., ROHC [RFC5225]), where others
include nonchanging IDs via zero deltas (e.g., ECRTP [RFC3545]).
When compression assumes a changing ID as a default, having a non-
changing ID can make compression less efficient (see footnote 21 of
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[RFC1144] or cRTP [RFC2508]). When compression can assume a
nonchanging IPv4 ID - as with ROHC and ECRTP - efficiency can be
increased.
11. Security Considerations
When the IPv4 ID is ignored on receipt (e.g., for atomic datagrams),
its value becomes unconstrained; that field then can more easily be
used as a covert channel. For some atomic datagrams - notably those
not protected by IPsec Authentication Header (AH) [RFC4302] - it is
now possible, and may be desirable, to rewrite the IPv4 ID field to
avoid its use as such a channel.
The IPv4 ID also now adds much less entropy of the header of a
datagram. The IPv4 ID had previously been unique (for a given
source/address pair, and protocol field) within one MSL, although
this requirement was not enforced and clearly is typically ignored.
The IPv4 ID of atomic datagrams is not required unique, and so
contributes no entropy to the header.
The deprecation of the IPv4 ID field's uniqueness for atomic
datagrams can defeat the ability to count devices behind a
NAT/ASM/rewriter [Be02]. This is not intended as a security feature,
however.
12. IANA Considerations
There are no IANA considerations in this document.
The RFC Editor should remove this section prior to publication
13. References
13.1. Normative References
[RFC791] Postel, J., "Internet Protocol", RFC 791 / STD 5, September
1981.
[RFC1122] Braden, R., Ed., "Requirements for Internet Hosts -
Communication Layers", RFC 1122 / STD 3, October 1989.
[RFC1812] Baker, F. (Ed.), "Requirements for IP Version 4 Routers",
RFC 1812 / STD 4, Jun. 1995.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", RFC 2119 / BCP 14, March 1997.
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[RFC2003] Perkins, C., "IP Encapsulation within IP", RFC 2003,
October 1996.
13.2. Informative References
[Be02] Bellovin, S., "A Technique for Counting NATted Hosts",
Internet Measurement Conference, Proceedings of the 2nd ACM
SIGCOMM Workshop on Internet Measurement, November 2002.
[Bo11] Boucadair, M., J. Touch, P. Levis, R. Penno, "Analysis of
Solution Candidates to Reveal a Host Identifier in Shared
Address Deployments", (work in progress), draft-boucadair-
intarea-nat-reveal-analysis, Sept. 2011.
[De11] Despres, R. (Ed.), S. Matsushima, T. Murakami, O. Troan,
"IPv4 Residual Deployment across IPv6-Service networks
(4rd)", (work in progress), draft-despres-intarea-4rd,
March 2011.
[Ma11] Macker, J. (Ed.), "Simplified Multicast Forwarding," (work
in progress), draft-ietf-manet-smf-12, Jul. 2011.
[Pe11] Perreault, S., (Ed.), I. Yamagata, S. Miyakawa, A.
Nakagawa, H. Ashida, "Common requirements of IP address
sharing schemes", (work in progress), draft-ietf-behave-
lsn-requirements, March 2011.
[RFC1144] Jacobson, V., "Compressing TCP/IP Headers", RFC 1144, Feb.
1990.
[RFC2460] Deering, S., R. Hinden, "Internet Protocol, Version 6
(IPv6) Specification", RFC 2460, December 1998.
[RFC2508] Casner, S., V. Jacobson. "Compressing IP/UDP/RTP Headers
for Low-Speed Serial Links", RFC 2508, Feb. 1999.
[RFC2671] Vixie,P., "Extension Mechanisms for DNS (EDNS0)", RFC 2671,
August 1999.
[RFC3022] Srisuresh, P. and K. Egevang, "Traditional IP Network
Address Translator (Traditional NAT)", RFC 3022, January
2001.
[RFC3545] Koren, T., S. Casner, J. Geevarghese, B. Thompson, P.
Ruddy, "Enhanced Compressed RTP (CRTP) for Links with High
Delay, Packet Loss and Reordering", RFC 3545, July 2003.
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[RFC3828] Larzon, L-A., M. Degermark, S. Pink, L-E. Jonsson, Ed., G.
Fairhurst, Ed., "The Lightweight User Datagram Protocol
(UDP-Lite)", RFC 3828, July 2004.
[RFC4301] Kent, S., K. Seo, "Security Architecture for the Internet
Protocol", RFC 4301, Dec. 2005.
[RFC4302] Kent, S., "IP Authentication Header", RFC 4302, Dec. 2005.
[RFC4960] Stewart, R. (Ed.), "Stream Control Transmission Protocol",
RFC 4960, Sep. 2007.
[RFC4963] Heffner, J., M. Mathis, B. Chandler, "IPv4 Reassembly
Errors at High Data Rates," RFC 4963, July 2007.
[RFC5225] Pelletier, G., K. Sandlund, "RObust Header Compression
Version 2 (ROHCv2): Profiles for RTP, UDP, IP, ESP and UDP-
Lite", RFC 5225, Apr. 2008.
[RFC5320] Templin, F., Ed., "The Subnetwork Encapsulation and
Adaptation Layer (SEAL)", RFC 5320, Feb. 2010.
[RFC6219] Li, X., C. Bao, M. Chen, H. Zhang, J. Wu, "The China
Education and Research Network (CERNET) IVI Translation
Design and Deployment for the IPv4/IPv6 Coexistence and
Transition", RFC 6219, May 2011.
14. Acknowledgments
This document was inspired by of numerous discussions among the
authors, Jari Arkko, Lars Eggert, Dino Farinacci, and Fred Templin,
as well as members participating in the Internet Area Working Group.
Detailed feedback was provided by Gorry Fairhurst, Mike Heard, Erik
Nordmark, Carlos Pignataro, and Dan Wing. This document originated as
an Independent Stream draft co-authored by Matt Mathis, PSC, and his
contributions are greatly appreciated.
This document was prepared using 2-Word-v2.0.template.dot.
Touch Expires March 16, 2012 [Page 15]
Internet-Draft Updated Spec. of the IPv4 ID Field September 2011
Author's Address
Joe Touch
USC/ISI
4676 Admiralty Way
Marina del Rey, CA 90292-6695
U.S.A.
Phone: +1 (310) 448-9151
Email: touch@isi.edu
Touch Expires March 16, 2012 [Page 16]
