draft-ietf-tsvwg-udp-options-05.txt   draft-ietf-tsvwg-udp-options-06.txt 
TSVWG J. Touch TSVWG J. Touch
Internet Draft Internet Draft Independent consultant
Intended status: Standards Track July 19, 2018 Intended status: Standards Track March 5, 2019
Intended updates: 768 Intended updates: 768
Expires: January 2019 Expires: September 2019
Transport Options for UDP Transport Options for UDP
draft-ietf-tsvwg-udp-options-05.txt draft-ietf-tsvwg-udp-options-06.txt
Status of this Memo Status of this Memo
This Internet-Draft is submitted in full conformance with the This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79. This document may not be modified, provisions of BCP 78 and BCP 79. This document may not be modified,
and derivative works of it may not be created, except to format it and derivative works of it may not be created, except to format it
for publication as an RFC or to translate it into languages other for publication as an RFC or to translate it into languages other
than English. than English.
Internet-Drafts are working documents of the Internet Engineering Internet-Drafts are working documents of the Internet Engineering
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This Internet-Draft will expire on January 19, 2019. This Internet-Draft will expire on September 5, 2019.
Copyright Notice Copyright Notice
Copyright (c) 2018 IETF Trust and the persons identified as the Copyright (c) 2019 IETF Trust and the persons identified as the
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3. Background.....................................................3 3. Background.....................................................3
4. The UDP Option Area............................................4 4. The UDP Option Area............................................4
5. UDP Options....................................................7 5. UDP Options....................................................7
5.1. End of Options List (EOL).................................8 5.1. End of Options List (EOL).................................8
5.2. No Operation (NOP)........................................9 5.2. No Operation (NOP)........................................9
5.3. Option Checksum (OCS).....................................9 5.3. Option Checksum (OCS).....................................9
5.4. Alternate Checksum (ACS).................................10 5.4. Alternate Checksum (ACS).................................10
5.5. Lite (LITE)..............................................11 5.5. Lite (LITE)..............................................11
5.6. Maximum Segment Size (MSS)...............................13 5.6. Maximum Segment Size (MSS)...............................13
5.7. Fragmentation (FRAG).....................................14 5.7. Fragmentation (FRAG).....................................14
5.7.1. Coupling FRAG with LITE.............................16 5.8. Coupling FRAG with LITE..................................16
5.8. Timestamps (TIME)........................................17 5.9. Timestamps (TIME)........................................17
5.9. Authentication and Encryption (AE).......................17 5.10. Authentication and Encryption (AE)......................18
5.10. Experimental (EXP)......................................18 6. Echo request (REQ) and echo response (RES)....................19
6. UDP API Extensions............................................19 6.1. Experimental (EXP).......................................19
7. Whose options are these?......................................20 7. Rules for designing new options...............................19
8. UDP options LITE option vs. UDP-Lite..........................20 8. Option inclusion and processing...............................20
9. Interactions with Legacy Devices..............................21 9. UDP API Extensions............................................22
10. Options in a Stateless, Unreliable Transport Protocol........22 10. Whose options are these?.....................................22
11. UDP Option State Caching.....................................22 11. UDP options LITE option vs. UDP-Lite.........................23
12. Updates to RFC 768...........................................22 12. Interactions with Legacy Devices.............................24
13. Multicast Considerations.....................................23 13. Options in a Stateless, Unreliable Transport Protocol........24
14. Security Considerations......................................23 14. UDP Option State Caching.....................................25
15. IANA Considerations..........................................23 15. Updates to RFC 768...........................................25
16. References...................................................24 16. Multicast Considerations.....................................25
16.1. Normative References....................................24 17. Security Considerations......................................26
16.2. Informative References..................................24 18. IANA Considerations..........................................26
17. Acknowledgments..............................................26 19. References...................................................27
Appendix A. Implementation Information...........................28 19.1. Normative References....................................27
19.2. Informative References..................................27
20. Acknowledgments..............................................29
Appendix A. Implementation Information...........................30
1. Introduction 1. Introduction
Transport protocols use options as a way to extend their Transport protocols use options as a way to extend their
capabilities. TCP [RFC793], SCTP [RFC4960], and DCCP [RFC4340] capabilities. TCP [RFC793], SCTP [RFC4960], and DCCP [RFC4340]
include space for these options but UDP [RFC768] currently does not. include space for these options but UDP [RFC768] currently does not.
This document defines an experimental extension to UDP that provides This document defines an experimental extension to UDP that provides
space for transport options including their generic syntax and space for transport options including their generic syntax and
semantics for their use in UDP's stateless, unreliable message semantics for their use in UDP's stateless, unreliable message
protocol. protocol.
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Many protocols include a default header and an area for header Many protocols include a default header and an area for header
options. These options enable the protocol to be extended for use in options. These options enable the protocol to be extended for use in
particular environments or in ways unforeseen by the original particular environments or in ways unforeseen by the original
designers. Examples include TCP's Maximum Segment Size, Window designers. Examples include TCP's Maximum Segment Size, Window
Scale, Timestamp, and Authentication Options Scale, Timestamp, and Authentication Options
[RFC793][RFC5925][RFC7323]. [RFC793][RFC5925][RFC7323].
These options are used both in stateful (connection-oriented, e.g., These options are used both in stateful (connection-oriented, e.g.,
TCP [RFC793], SCTP [RFC4960], DCCP [RFC4340]) and stateless TCP [RFC793], SCTP [RFC4960], DCCP [RFC4340]) and stateless
(connectionless, e.g., IPv4 [RFC791], IPv6 [RFC8200] protocols. In (connectionless, e.g., IPv4 [RFC791], IPv6 [RFC8200]) protocols. In
stateful protocols they can help extend the way in which state is stateful protocols they can help extend the way in which state is
managed. In stateless protocols their effect is often limited to managed. In stateless protocols their effect is often limited to
individual packets, but they can have an aggregate effect on a individual packets, but they can have an aggregate effect on a
sequence as well. One example of such uses is Substrate Protocol for sequence as well. One example of such uses is Substrate Protocol for
User Datagrams (SPUD) [Tr16], and this document is intended to User Datagrams (SPUD) [Tr16], and this document is intended to
provide an out-of-band option area as an alternative to the in-band provide an out-of-band option area as an alternative to the in-band
mechanism currently proposed [Hi15]. mechanism currently proposed [Hi15].
UDP is one of the most popular protocols that lacks space for UDP is one of the most popular protocols that lacks space for
options [RFC768]. The UDP header was intended to be a minimal options [RFC768]. The UDP header was intended to be a minimal
addition to IP, providing only ports and a data checksum for addition to IP, providing only ports and a data checksum for
protection. This document experimentally extends UDP to provide a protection. This document experimentally extends UDP to provide a
trailer area for options located after the UDP data payload. trailer area for options located after the UDP data payload.
4. The UDP Option Area 4. The UDP Option Area
The UDP transport header includes demultiplexing and service The UDP transport header includes demultiplexing and service
identification (port numbers), a checksum, and a field that identification (port numbers), a checksum, and a field that
indicates the UDP datagram length (including UDP header). The UDP indicates the UDP datagram length (including UDP header). The UDP
Length length field is typically redundant with the size of the Length field is typically redundant with the size of the maximum
maximum space available as a transport protocol payload (see also space available as a transport protocol payload (see also discussion
discussion in Section 9). in Section 12).
For IPv4, IP Total Length field indicates the total IP datagram For IPv4, IP Total Length field indicates the total IP datagram
length (including IP header), and the size of the IP options is length (including IP header), and the size of the IP options is
indicated in the IP header (in 4-byte words) as the "Internet Header indicated in the IP header (in 4-byte words) as the "Internet Header
Length" (IHL), as shown in Figure 1 [RFC791]. As a result, the Length" (IHL), as shown in Figure 1 [RFC791]. As a result, the
typical (and largest valid) value for UDP Length is: typical (and largest valid) value for UDP Length is:
UDP_Length = IPv4_Total_Length - IPv4_IHL * 4 UDP_Length = IPv4_Total_Length - IPv4_IHL * 4
For IPv6, the IP Payload Length field indicates the datagram after For IPv6, the IP Payload Length field indicates the datagram after
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| IP Hdr | UDP Hdr | UDP user data | surplus area | | IP Hdr | UDP Hdr | UDP user data | surplus area |
+--------+---------+----------------------+------------------+ +--------+---------+----------------------+------------------+
<------------------------------> <------------------------------>
UDP Length UDP Length
Figure 3 IP transport payload vs. UDP Length Figure 3 IP transport payload vs. UDP Length
In most cases, the IP transport payload and UDP Length point to the In most cases, the IP transport payload and UDP Length point to the
same location, indicating that there is no surplus area. It is same location, indicating that there is no surplus area. It is
important to note that this is not a requirement of UDP [RFC768] important to note that this is not a requirement of UDP [RFC768]
(discussed further in Section 9). UDP-Lite used the difference in (discussed further in Section 12). UDP-Lite used the difference in
these pointers to indicate the partial coverage of the UDP Checksum, these pointers to indicate the partial coverage of the UDP Checksum,
such that the UDP user data, UDP header, and UDP pseudoheader (a such that the UDP user data, UDP header, and UDP pseudoheader (a
subset of the IP header) are covered by the UDP checksum but subset of the IP header) are covered by the UDP checksum but
additional user data in the surplus area is not covered [RFC3828]. additional user data in the surplus area is not covered [RFC3828].
This document uses the surplus area for UDP transport options. This document uses the surplus area for UDP transport options.
The UDP option area is thus defined as the location between the end The UDP option area is thus defined as the location between the end
of the UDP payload and the end of the IP datagram as a trailing of the UDP payload and the end of the IP datagram as a trailing
options area. This area can occur at any valid byte offset, i.e., it options area. This area can occur at any valid byte offset, i.e., it
need not be 16-bit or 32-bit aligned. In effect, this document need not be 16-bit or 32-bit aligned. In effect, this document
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---------------------------------------------- ----------------------------------------------
0* - End of Options List (EOL) 0* - End of Options List (EOL)
1* - No operation (NOP) 1* - No operation (NOP)
2* 2 Option checksum (OCS) 2* 2 Option checksum (OCS)
3* 4 Alternate checksum (ACS) 3* 4 Alternate checksum (ACS)
4* 4 Lite (LITE) 4* 4 Lite (LITE)
5* 4 Maximum segment size (MSS) 5* 4 Maximum segment size (MSS)
6* 8/10 Fragmentation (FRAG) 6* 8/10 Fragmentation (FRAG)
7 10 Timestamps (TIME) 7 10 Timestamps (TIME)
8 (varies) Authentication and Encryption (AE) 8 (varies) Authentication and Encryption (AE)
9-126 (varies) UNASSIGNED (assignable by IANA) 9 6 Request (REQ)
10 6 Response (RES)
11-126 (varies) UNASSIGNED (assignable by IANA)
127-253 RESERVED 127-253 RESERVED
254 N(>=4) RFC 3692-style experiments (EXP) 254 N(>=4) RFC 3692-style experiments (EXP)
255 RESERVED 255 RESERVED
These options are defined in the following subsections. These options are defined in the following subsections. Options 0
and 1 use the same values as for TCP.
>> An endpoint supporting UDP options MUST support those marked with >> An endpoint supporting UDP options MUST support those marked with
a "*" above: EOL, NOP, OCS, ACS, LITE, FRAG, and MSS. This includes a "*" above: EOL, NOP, OCS, ACS, LITE, FRAG, and MSS. This includes
both recognizing and being able to generate these options if both recognizing and being able to generate these options if
configured to do so. configured to do so.
>> All other options (without a "*") MAY be implemented, and their >> All other options (without a "*") MAY be implemented, and their
use SHOULD be determined either out-of-band or negotiated. use SHOULD be determined either out-of-band or negotiated.
>> Receivers MUST silently ignore unknown options. That includes >> Receivers MUST silently ignore unknown options. That includes
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this occurs, the packet MUST be treated as malformed and dropped, this occurs, the packet MUST be treated as malformed and dropped,
and the event MAY be logged for diagnostics (logging SHOULD be rate and the event MAY be logged for diagnostics (logging SHOULD be rate
limited). limited).
>> Required options MUST come before other options. Each required >> Required options MUST come before other options. Each required
option MUST NOT occur more than once (if they are repeated in a option MUST NOT occur more than once (if they are repeated in a
received segment, all except the first MUST be silently ignored). received segment, all except the first MUST be silently ignored).
The requirement that required options come before others is intended The requirement that required options come before others is intended
to allow for endpoints to implement DOS protection, as discussed to allow for endpoints to implement DOS protection, as discussed
further in Section 14. further in Section 17.
5.1. End of Options List (EOL) 5.1. End of Options List (EOL)
The End of Options List (EOL) option indicates that there are no The End of Options List (EOL) option indicates that there are no
more options. It is used to indicate the end of the list of options more options. It is used to indicate the end of the list of options
without needing to pad the options to fill all available option without needing to pad the options to fill all available option
space. space.
+--------+ +--------+
| Kind=0 | | Kind=0 |
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are intended to assist with alignment, not other padding or fill. are intended to assist with alignment, not other padding or fill.
[NOTE: Tom Herbert suggested we declare "more than 3 consecutive [NOTE: Tom Herbert suggested we declare "more than 3 consecutive
NOPs" a fatal error to reduce the potential of using NOPs as a DOS NOPs" a fatal error to reduce the potential of using NOPs as a DOS
attack, but IMO there are other equivalent ways (e.g., using attack, but IMO there are other equivalent ways (e.g., using
RESERVED or other UNASSIGNED values) and the "no more than 3" RESERVED or other UNASSIGNED values) and the "no more than 3"
creates its own DOS vulnerability) creates its own DOS vulnerability)
5.3. Option Checksum (OCS) 5.3. Option Checksum (OCS)
The Option Checksum (OCS) is an 8-bit ones-complement sum (Ones8) The Option Checksum (OCS) is conventional Internet checksum that
that covers all of the UDP options. OCS is 8-bits to allow the covers all of the UDP options. The primary purpose of OCS is to
entire option to occupy a total of 16 bits. The primary purpose of detect non-standard (i.e., non-option) uses of the options area.
OCS is to detect non-standard (i.e., non-option) uses of the surplus
area.
OCS can be calculated by computing the 16-bit ones-complement sum OCS is calculated by computing the ones-complement of the 8-bit
and "folding over" the result (using carry wraparound). Note that ones-complement checksum (i.e., Internet checksum) sum of the
OCS is direct, i.e., it is not negated or adjusted if zero (unlike options area. OCS protects the option area from errors in a similar
the Internet checksum as used in IPv4, TCP, and UDP headers). OCS way that the UDP checksum protects the UDP user data (when not
protects the option area from errors in a similar way that the UDP zero).
checksum protects the UDP user data.
+--------+--------+ +--------+--------+
| Kind=2 | Ones8 | | Kind=2 |checksum|
+--------+--------+ +--------+--------+
Figure 7 UDP OCS option format Figure 7 UDP OCS option format
>> When present, the option checksum SHOULD occur as early as >> When present, the option checksum SHOULD occur as early as
possible, preferably preceded by only NOP options for alignment and possible, preferably preceded by only NOP options for alignment and
the LITE option if present. the LITE option if present.
OCS covers the entire UDP option area, including the Lite option as >> OCS SHOULD be half-word aligned to the start of the UDP packet.
This is to help ensure that the option, together with the other
options, result in an overall zero ones-complement sum, which may
help the UDP options traverse devices that incorrectly attempt to
checksum the surplus area (as originally proposed as the Checksum
Compensation Option [Fa18]).
OCS covers the UDP option area, including the Lite option as
formatted before swapping (or relocation) for transmission (or, formatted before swapping (or relocation) for transmission (or,
equivalently, after the swap/relocation after reception). equivalently, after the swap/relocation after reception).
>> If the option checksum fails, all options MUST be ignored and any >> If the option checksum fails, all options MUST be ignored and any
trailing surplus data (and Lite data, if used) silently discarded. trailing surplus data (and Lite data, if used) silently discarded.
>> UDP data that is validated by a correct UDP checksum MUST be >> UDP data that is validated by a correct UDP checksum MUST be
delivered to the application layer, even if the UDP option checksum delivered to the application layer, even if the UDP option checksum
fails, unless the endpoints have negotiated otherwise for this fails, unless the endpoints have negotiated otherwise for this
segment's socket pair. segment's socket pair.
Note that use of the UDP checksum is optional. When not used, the
field is zero, where it is also assumed to be "correct" for these
purposes.
Note also that OCS is intended to check for accidental errors, not
for attacks.
5.4. Alternate Checksum (ACS) 5.4. Alternate Checksum (ACS)
The Alternate Checksum (ACS) provides a stronger alternative to the The Alternate Checksum (ACS) provides a stronger alternative to the
checksum in the UDP header, using a 16-bit CRC of the conventional checksum in the UDP header, using a 16-bit CRC of the conventional
UDP payload only (excluding the IP pseudoheader, UDP header, and UDP UDP payload only (excluding the IP pseudoheader, UDP header, and UDP
options, and not include the LITE area). Because it does not include options, and not include the LITE area). Because it does not include
the IP pseudoheader or UDP header, it need not be updated by NATs the IP pseudoheader or UDP header, it need not be updated by NATs
when IP addresses or UDP ports are rewritten. Its purpose is to when IP addresses or UDP ports are rewritten. Its purpose is to
detect errors that the UDP checksum might not detect. detect errors that the UDP checksum, when used, might not detect.
CRC-CCITT (polynomial x^16 + x^12 + x^5 + 1) has been chosen because CRC-CCITT (polynomial x^16 + x^12 + x^5 + 1) has been chosen because
of its ubiquity and use in other packet protocols, such as X.25, of its ubiquity and use in other packet protocols, such as X.25,
HDLC, and Bluetooth. The option contains FCS-16 as defined in HDLC, and Bluetooth. The option contains FCS-16 as defined in
Appendix C of [RFC1662], except that it is not inverted in the final Appendix C of [RFC1662], except that it is not inverted in the final
step and that it is stored in the ACS option in network byte order. step and that it is stored in the ACS option in network byte order.
+--------+--------+--------+--------+ +--------+--------+--------+--------+
| Kind=3 | Len=4 | CRC16sum | | Kind=3 | Len=4 | CRC16sum |
+--------+--------+--------+--------+ +--------+--------+--------+--------+
Figure 8 UDP ACS option format Figure 8 UDP ACS option format
When present, the ACS always contains a valid CRC checksum. There When present, the ACS always contains a valid CRC checksum. There
are no reserved values, including the value of zero. If the CRC is are no reserved values, including the value of zero. If the CRC is
zero, this must indicate a valid checksum (i.e., it does not zero, this must indicate a valid checksum (i.e., it does not
indicate that the ACS is not used; instead, the option would simply indicate that the ACS is not used; instead, the option would simply
not be included if that were the desired effect). not be included if that were the desired effect).
ACS does not protect the UDP pseudoheader; only the current UDP ACS does not protect the UDP pseudoheader; only the current UDP
checksum provides that protection. ACS cannot provide that checksum provides that protection (when used). ACS cannot provide
protection because it would need to be updated whenever the UDP that protection because it would need to be updated whenever the UDP
pseudoheader changed, e.g., during NAT address and port translation; pseudoheader changed, e.g., during NAT address and port translation;
because this is not the case, ACS does not cover the pseudoheader. because this is not the case, ACS does not cover the pseudoheader.
5.5. Lite (LITE) 5.5. Lite (LITE)
The Lite option (LITE) is intended to provide equivalent capability The Lite option (LITE) is intended to provide equivalent capability
to the UDP Lite transport protocol [RFC3828]. UDP Lite allows the to the UDP Lite transport protocol [RFC3828]. UDP Lite allows the
UDP checksum to cover only a prefix of the UDP data payload, to UDP checksum to cover only a prefix of the UDP data payload, to
protect critical information (e.g., application headers) but allow protect critical information (e.g., application headers) but allow
potentially erroneous data to be passed to the user. This feature potentially erroneous data to be passed to the user. This feature
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>> The Identification field is a 32-bit value that MUST be unique >> The Identification field is a 32-bit value that MUST be unique
over the expected fragment reassembly timeout. over the expected fragment reassembly timeout.
>> The Identification field SHOULD be generated in a manner similar >> The Identification field SHOULD be generated in a manner similar
to that of the IPv6 Fragment ID [RFC8200]. to that of the IPv6 Fragment ID [RFC8200].
>> UDP fragments MUST NOT overlap. >> UDP fragments MUST NOT overlap.
FRAG needs to be used with extreme care because it will present FRAG needs to be used with extreme care because it will present
incorrect datagram boundaries to a legacy receiver, unless encoded incorrect datagram boundaries to a legacy receiver, unless encoded
as LITE data (see Section 5.7.1). as LITE data (see Section 5.8).
>> A host SHOULD indicate FRAG support by transmitting an >> A host SHOULD indicate FRAG support by transmitting an
unfragmented datagram using the Fragmentation option (e.g., with unfragmented datagram using the Fragmentation option (e.g., with
Offset zero and length 12, i.e., including the checksum area), Offset zero and length 12, i.e., including the checksum area),
except when encoded as LITE. except when encoded as LITE.
>> A host MUST NOT transmit a UDP fragment before receiving recent >> A host MUST NOT transmit a UDP fragment before receiving recent
confirmation from the remote host, except when FRAG is encoded as confirmation from the remote host, except when FRAG is encoded as
LITE. LITE.
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Any additional UDP options would follow the FRAG option in the final Any additional UDP options would follow the FRAG option in the final
fragment, and would be included in the reassembled packet. fragment, and would be included in the reassembled packet.
Processing of those options would commence after reassembly. Processing of those options would commence after reassembly.
>> UDP options MUST NOT follow the FRAG header in non-terminal >> UDP options MUST NOT follow the FRAG header in non-terminal
fragments. Any data following the FRAG header in non-terminal fragments. Any data following the FRAG header in non-terminal
fragments MUST be silently dropped. All other options that apply to fragments MUST be silently dropped. All other options that apply to
a reassembled packet MUST follow the FRAG header in the terminal a reassembled packet MUST follow the FRAG header in the terminal
fragment. fragment.
5.7.1. Coupling FRAG with LITE 5.8. Coupling FRAG with LITE
FRAG can be coupled with LITE to avoid impacting legacy receivers. FRAG can be coupled with LITE to avoid impacting legacy receivers.
Each fragment is sent as LITE un-checksummed data, where each UDP Each fragment is sent as LITE un-checksummed data, where each UDP
packet contains no legacy-compatible data. Legacy receivers packet contains no legacy-compatible data. Legacy receivers
interpret these as zero-payload packets, which would not affect the interpret these as zero-length payload packets (i.e., UDP Length
receiver unless the presence of the packet itself were a signal. The field is 8, the length of just the UDP header), which would not
header of such a packet would appear as shown in Figure 16 and affect the receiver unless the presence of the packet itself were a
Figure 17. signal. The header of such a packet would appear as shown in Figure
16 and Figure 17.
+---------+--------------+---------+ +---------+--------------+---------+
| UDP Hdr | LiteFrag |LITE|FRAG| | UDP Hdr | LiteFrag |LITE|FRAG|
+---------+--------------+----+----+ +---------+--------------+----+----+
<-------> ^^^^ ^^^^ <-------> ^^^^ ^^^^
Zero UDP Length | | UDP Length=8 | |
+--------------+ +--------------+
Figure 16 Preparing FRAG as Lite data Figure 16 Preparing FRAG as Lite data
+---------+--------------+----+ +---------+--------------+----+
| UDP Hdr |LITE|LiteFrag |FRAG| | UDP Hdr |LITE|LiteFrag |FRAG|
+---------+--------------+----+ +---------+--------------+----+
<-------> | ^ <-------> | ^
Zero UDP Length | | UDP Length=8 | |
+-------------+ +-------------+
Figure 17 Lite option before transmission Figure 17 Lite option before transmission
When a packet is reassembled, it appears as a complete LITE data When a packet is reassembled, it appears as a complete LITE data
region. The UDP header of the reassembled packet is adjusted region. The UDP header of the reassembled packet is adjusted
accordingly, so that the reassembled region now appears as accordingly, so that the reassembled region now appears as
conventional UDP user data, and processing of the UDP options conventional UDP user data, and processing of the UDP options
continues, as with the non-LITE FRAG variant. continues, as with the non-LITE FRAG variant.
5.8. Timestamps (TIME) 5.9. Timestamps (TIME)
The UDP Timestamp option (TIME) exchanges two four-byte timestamp The UDP Timestamp option (TIME) exchanges two four-byte timestamp
fields. It serves a similar purpose to TCP's TS option [RFC7323], fields. It serves a similar purpose to TCP's TS option [RFC7323],
enabling UDP to estimate the round trip time (RTT) between hosts. enabling UDP to estimate the round trip time (RTT) between hosts.
For UDP, this RTT can be useful for establishing UDP fragment For UDP, this RTT can be useful for establishing UDP fragment
reassembly timeouts or transport-layer rate-limiting [RFC8085]. reassembly timeouts or transport-layer rate-limiting [RFC8085].
+--------+--------+------------------+------------------+ +--------+--------+------------------+------------------+
| Kind=7 | Len=10 | TSval | TSecr | | Kind=7 | Len=10 | TSval | TSecr |
+--------+--------+------------------+------------------+ +--------+--------+------------------+------------------+
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TSecr of zero indicates that the TSval was not echoed by the TSecr of zero indicates that the TSval was not echoed by the
transmitter, i.e., from a previously received UDP packet. transmitter, i.e., from a previously received UDP packet.
>> UDP MAY use an RTT estimate based on nonzero Timestamp values as >> UDP MAY use an RTT estimate based on nonzero Timestamp values as
a hint for fragmentation reassembly, rate limiting, or other a hint for fragmentation reassembly, rate limiting, or other
mechanisms that benefit from such an estimate. mechanisms that benefit from such an estimate.
>> UDP SHOULD make this RTT estimate available to the user >> UDP SHOULD make this RTT estimate available to the user
application. application.
5.9. Authentication and Encryption (AE) These UDP timestamps are modeled after TCP timestamps and have
similar expectations. In particular, they are expected to be:
o Values are monotonic and non-decreasing
o Values should increase according to a typical 'tick' time
o A request is defined as "reply=0" and a reply is defined as both
fields being non-zero.
o A receiver should always respond to a request with the highest
TSval received, which is not necessarily the most recently
received.
5.10. Authentication and Encryption (AE)
The Authentication and Encryption option (AE) is intended to allow The Authentication and Encryption option (AE) is intended to allow
UDP to provide a similar type of authentication as the TCP UDP to provide a similar type of authentication as the TCP
Authentication Option (TCP-AO) [RFC5925]. It uses the same format as Authentication Option (TCP-AO) [RFC5925]. It uses the same format as
specified for TCP-AO, except that it uses a Kind of 8. UDP-AO specified for TCP-AO, except that it uses a Kind of 8. UDP-AO
supports NAT traversal in a similar manner as TCP-AO [RFC6978]. UDP- supports NAT traversal in a similar manner as TCP-AO [RFC6978]. UDP-
AO can also be extended to provide a similar encryption capability AO can also be extended to provide a similar encryption capability
as TCP-AO-ENC, in a similar manner [To18ao]. For these reasons, the as TCP-AO-ENC, in a similar manner [To18ao]. For these reasons, the
option is known as UDP-AE. option is known as UDP-AE.
skipping to change at page 18, line 36 skipping to change at page 19, line 5
option area checksum and UDP-AE hash areas are zeroed before option area checksum and UDP-AE hash areas are zeroed before
computing the UDP-AE hash. It is important to consider that options computing the UDP-AE hash. It is important to consider that options
not yet defined might yield unpredictable results if not confirmed not yet defined might yield unpredictable results if not confirmed
as supported, e.g., if they were to contain other hashes or as supported, e.g., if they were to contain other hashes or
checksums that depend on the option area contents. This is why such checksums that depend on the option area contents. This is why such
dependencies are not permitted except as defined for OCS and UDP-AE. dependencies are not permitted except as defined for OCS and UDP-AE.
Similar to TCP-AO-NAT, UDP-AE can be configured to support NAT Similar to TCP-AO-NAT, UDP-AE can be configured to support NAT
traversal, excluding one or both of the UDP ports [RFC6978]. traversal, excluding one or both of the UDP ports [RFC6978].
5.10. Experimental (EXP) 6. Echo request (REQ) and echo response (RES)
The echo request (REQ, kind=9) and echo response (RES, kind=10)
options provide a means for UDP options to be used to provide
packet-level acknowledgements. Their use is described as part of the
UDP variant of packetization layer path MTU discovery (PLPMTUD)
[Fa19]. The options both have the format indicated in Figure 20.
+--------+--------+------------------+
| Kind | Len=6 | nonce |
+--------+--------+------------------+
1 byte 1 byte 4 bytes
Figure 20 Echo option format
6.1. Experimental (EXP)
The Experimental option (EXP) is reserved for experiments [RFC3692]. The Experimental option (EXP) is reserved for experiments [RFC3692].
It uses a Kind value of 254. Only one such value is reserved because It uses a Kind value of 254. Only one such value is reserved because
experiments are expected to use an Experimental ID (ExIDs) to experiments are expected to use an Experimental ID (ExIDs) to
differentiate concurrent use for different purposes, using UDP ExIDs differentiate concurrent use for different purposes, using UDP ExIDs
registered with IANA according to the approach developed for TCP registered with IANA according to the approach developed for TCP
experimental options [RFC6994]. experimental options [RFC6994].
+----------+----------+----------+----------+ +----------+----------+----------+----------+
| Kind=254 | Len | UDP ExID | | Kind=254 | Len | UDP ExID |
+----------+----------+----------+----------+ +----------+----------+----------+----------+
| (option contents, as defined)... | | (option contents, as defined)... |
+----------+----------+----------+----------+ +----------+----------+----------+----------+
Figure 20 UDP EXP option format Figure 21 UDP EXP option format
>> The length of the experimental option MUST be at least 4 to >> The length of the experimental option MUST be at least 4 to
account for the Kind, Length, and the minimum 16-bit UDP ExID account for the Kind, Length, and the minimum 16-bit UDP ExID
identifier (similar to TCP ExIDs [RFC6994]). identifier (similar to TCP ExIDs [RFC6994]).
6. UDP API Extensions 7. Rules for designing new options
The UDP option Kind space allows for the definition of new options,
however the currently defined options do not allow for arbitrary new
options. For example, LITE needs to come first if present; new
options cannot declare that they need to precede it. The following
is a summary of rules for new options and their rationales:
>> New options MUST NOT depend on option space content. Only OCS,
ACS, and AE depend on the content of the options themselves, and
their order is fixed (on transmission, AE is computed first using a
zero-checksum OCS or ACS if present, and OCS or ACS is computed
second over the entire option area, including AE).
>> New options MUST NOT declare their order relative to other
options, whether new or old.
>> New options MUST NOT modify content anywhere except within their
option field; areas that need to remain unmodified include the IP
header, IP options, the UDP body, the UDP option area (i.e., other
options), and the post-option area.
Note that only certain of the initially defined options violate
these rules:
o >> LITE MUST be first, if present, and MUST be processed when
encountered (e.g., even before security options).
o >> LITE is the only option that modifies the UDP body or option
areas.
o >> OCS or ACS MUST be the first option, except in the presence of
LITE, in which case they MUST be the first option after LITE.
o >> OCS and ACS MUST be processed by receivers when encountered in
the options list.
o >> AE MUST be processed by receivers when encountered in the
options list.
8. Option inclusion and processing
The following rules apply to option inclusion by senders and
processing by receivers.
>> Senders MAY add any option, as configured by the API.
>> All mandatory options MUST be processed by receivers, if present
(presuming UDP options are supported at that receiver).
>> Non-mandatory options MAY be ignored by receivers, if present,
based on API settings.
The basic premise is that the sender decides what options to add and
the receiver decides what options to handle. Simply adding an option
does not force work upon a receiver, with the exception of the
mandatory options.
Upon receipt, the receiver checks various properties of the UDP
packet and its options to decide whether to accept or drop the
packet and whether to accept or ignore some its options as follows
(in order):
if the UDP checksum fails then
silently drop (per RFC1122)
if the UDP checksum passes then
if OCS is present and fails then
deliver the UDP payload but ignore all options
(this is required to emulate legacy behavior)
if OCS is present and passes then
deliver the UDP payload after parsing
and processing the rest of the options
if both sender and receiver choose to use ACS then
if ACS passes then
deliver the UDP payload after parsing
and processing the rest of the options
if ACS fails then
silently drop the packet
if ACS is not present when received then
silently drop the packet
if the sender includes ACS
and the receiver does not indicate ACS is required then
the receiver accepts all UDP payloads that pass
the UDP checksum and indicate for each packet
whether ACS succeeded, but never drop when ACS fails
I.e., ACS should be treated like any other option, in that the
transmitter can add it as desired and the receiver has the option to
require it or not. Only if it is required (by API configuration)
should the receiver require it being present and correct.
I.e., for all options other than OCS:
o if the option is not required by the receiver, then packets
missing the option are accepted.
o if the option is required and missing or incorrectly formed,
silently drop the packet.
o if the packet is accepted (either because the option is not
required or because it was required and correct), then pass the
option with the packet via the API.
Any options whose length exceeds that of the UDP packet (i.e.,
intending to use data that would have been beyond the surplus area)
should be silently ignored (again to model legacy behavior).
9. UDP API Extensions
UDP currently specifies an application programmer interface (API), UDP currently specifies an application programmer interface (API),
summarized as follows (with Unix-style command as an example) summarized as follows (with Unix-style command as an example)
[RFC768]: [RFC768]:
o Method to create new receive ports o Method to create new receive ports
o E.g., bind(handle, recvaddr(optional), recvport) o E.g., bind(handle, recvaddr(optional), recvport)
o Receive, which returns data octets, source port, and source o Receive, which returns data octets, source port, and source
skipping to change at page 20, line 5 skipping to change at page 22, line 48
o Extend the receive function to indicate the options and their o Extend the receive function to indicate the options and their
parameters as received with the corresponding received datagram. parameters as received with the corresponding received datagram.
o Extend the send function to indicate the options to be added to o Extend the send function to indicate the options to be added to
the corresponding sent datagram. the corresponding sent datagram.
Examples of API instances for Linux and FreeBSD are provided in Examples of API instances for Linux and FreeBSD are provided in
Appendix A, to encourage uniform cross-platform implementations. Appendix A, to encourage uniform cross-platform implementations.
7. Whose options are these? 10. Whose options are these?
UDP options are indicated in an area of the IP payload that is not UDP options are indicated in an area of the IP payload that is not
used by UDP. That area is really part of the IP payload, not the UDP used by UDP. That area is really part of the IP payload, not the UDP
payload, and as such, it might be tempting to consider whether this payload, and as such, it might be tempting to consider whether this
is a generally useful approach to extending IP. is a generally useful approach to extending IP.
Unfortunately, the surplus area exists only for transports that Unfortunately, the surplus area exists only for transports that
include their own transport layer payload length indicator. TCP and include their own transport layer payload length indicator. TCP and
SCTP include header length fields that already provide space for SCTP include header length fields that already provide space for
transport options by indicating the total length of the header area, transport options by indicating the total length of the header area,
skipping to change at page 20, line 33 skipping to change at page 23, line 28
UDP options are intended for use only by the transport endpoints. UDP options are intended for use only by the transport endpoints.
They are no more (or less) appropriate to be modified in-transit They are no more (or less) appropriate to be modified in-transit
than any other portion of the transport datagram. than any other portion of the transport datagram.
UDP options are transport options. Generally, transport datagrams UDP options are transport options. Generally, transport datagrams
are not intended to be modified in-transit. However, the UDP option are not intended to be modified in-transit. However, the UDP option
mechanism provides no specific protection against in-transit mechanism provides no specific protection against in-transit
modification of the UDP header, UDP payload, or UDP option area, modification of the UDP header, UDP payload, or UDP option area,
except as provided by the options selected (e.g., OCS, ACS, or AE). except as provided by the options selected (e.g., OCS, ACS, or AE).
8. UDP options LITE option vs. UDP-Lite 11. UDP options LITE option vs. UDP-Lite
UDP-Lite provides partial checksum coverage, so that packets with UDP-Lite provides partial checksum coverage, so that packets with
errors in some locations can be delivered to the user [RFC3828]. It errors in some locations can be delivered to the user [RFC3828]. It
uses a different transport protocol number (136) than UDP (17) to uses a different transport protocol number (136) than UDP (17) to
interpret the UDP Length field as the prefix covered by the UDP interpret the UDP Length field as the prefix covered by the UDP
checksum. checksum.
UDP (protocol 17) already defines the UDP Length field as the limit UDP (protocol 17) already defines the UDP Length field as the limit
of the UDP checksum, but by default also limits the data provided to of the UDP checksum, but by default also limits the data provided to
the application as that which precedes the UDP Length. A goal of the application as that which precedes the UDP Length. A goal of
skipping to change at page 21, line 20 skipping to change at page 24, line 15
implement UDP options would silently discard this non-checksummed implement UDP options would silently discard this non-checksummed
user data, along with the UDP options as well. user data, along with the UDP options as well.
UDP-Lite cannot support UDP options, either as proposed here or in UDP-Lite cannot support UDP options, either as proposed here or in
any other form, because the entire payload of the UDP packet is any other form, because the entire payload of the UDP packet is
already defined as user data and there is no additional field in already defined as user data and there is no additional field in
which to indicate a separate area for options. The UDP Length field which to indicate a separate area for options. The UDP Length field
in UDP-Lite is already used to indicate the boundary between user in UDP-Lite is already used to indicate the boundary between user
data covered by the checksum and user data not covered. data covered by the checksum and user data not covered.
9. Interactions with Legacy Devices 12. Interactions with Legacy Devices
It has always been permissible for the UDP Length to be inconsistent It has always been permissible for the UDP Length to be inconsistent
with the IP transport payload length [RFC768]. Such inconsistency with the IP transport payload length [RFC768]. Such inconsistency
has been utilized in UDP-Lite using a different transport number. has been utilized in UDP-Lite using a different transport number.
There are no known systems that use this inconsistency for UDP There are no known systems that use this inconsistency for UDP
[RFC3828]. It is possible that such use might interact with UDP [RFC3828]. It is possible that such use might interact with UDP
options, i.e., where legacy systems might generate UDP datagrams options, i.e., where legacy systems might generate UDP datagrams
that appear to have UDP options. The UDP OCS provides protection that appear to have UDP options. The UDP OCS provides protection
against such events and is stronger than a static "magic number". against such events and is stronger than a static "magic number".
skipping to change at page 22, line 5 skipping to change at page 24, line 47
It has been reported that Alcatel-Lucent's "Brick" Intrusion It has been reported that Alcatel-Lucent's "Brick" Intrusion
Detection System has a default configuration that interprets Detection System has a default configuration that interprets
inconsistencies between UDP Length and IP Length as an attack to be inconsistencies between UDP Length and IP Length as an attack to be
reported. Note that other firewall systems, e.g., CheckPoint, use a reported. Note that other firewall systems, e.g., CheckPoint, use a
default "relaxed UDP length verification" to avoid falsely default "relaxed UDP length verification" to avoid falsely
interpreting this inconsistency as an attack. interpreting this inconsistency as an attack.
(TBD: test with UDP checksum offload and UDP fragmentation offload) (TBD: test with UDP checksum offload and UDP fragmentation offload)
10. Options in a Stateless, Unreliable Transport Protocol 13. Options in a Stateless, Unreliable Transport Protocol
There are two ways to interpret options for a stateless, unreliable There are two ways to interpret options for a stateless, unreliable
protocol -- an option is either local to the message or intended to protocol -- an option is either local to the message or intended to
affect a stream of messages in a soft-state manner. Either affect a stream of messages in a soft-state manner. Either
interpretation is valid for defined UDP options. interpretation is valid for defined UDP options.
It is impossible to know in advance whether an endpoint supports a It is impossible to know in advance whether an endpoint supports a
UDP option. UDP option.
>> UDP options MUST allow for silent failure on first receipt. >> UDP options MUST allow for silent failure on first receipt.
skipping to change at page 22, line 29 skipping to change at page 25, line 24
>> A UDP option MUST be silently optional until confirmed by >> A UDP option MUST be silently optional until confirmed by
exchange with an endpoint. exchange with an endpoint.
The above requirements prevent using any option that cannot be The above requirements prevent using any option that cannot be
safely ignored unless that capability has been negotiated with an safely ignored unless that capability has been negotiated with an
endpoint in advance for a socket pair. Legacy systems would need to endpoint in advance for a socket pair. Legacy systems would need to
be able to interpret the transport payload fragments as individual be able to interpret the transport payload fragments as individual
transport datagrams. transport datagrams.
11. UDP Option State Caching 14. UDP Option State Caching
Some TCP connection parameters, stored in the TCP Control Block, can Some TCP connection parameters, stored in the TCP Control Block, can
be usefully shared either among concurrent connections or between be usefully shared either among concurrent connections or between
connections in sequence, known as TCP Sharing [RFC2140][To18cb]. connections in sequence, known as TCP Sharing [RFC2140][To19cb].
Although UDP is stateless, some of the options proposed herein may Although UDP is stateless, some of the options proposed herein may
have similar benefit in being shared or cached. We call this UCB have similar benefit in being shared or cached. We call this UCB
Sharing, or UDP Control Block Sharing, by analogy. Sharing, or UDP Control Block Sharing, by analogy.
[TBD: extend this section to indicate which options MAY vs. MUST NOT [TBD: extend this section to indicate which options MAY vs. MUST NOT
be shared and how, e.g., along the lines of To18cb] be shared and how, e.g., along the lines of To19cb]
12. Updates to RFC 768 15. Updates to RFC 768
This document updates RFC 768 as follows: This document updates RFC 768 as follows:
o This document defines the meaning of the IP payload area beyond o This document defines the meaning of the IP payload area beyond
the UDP length but within the IP length. the UDP length but within the IP length.
o This document extends the UDP API to support the use of options. o This document extends the UDP API to support the use of options.
13. Multicast Considerations 16. Multicast Considerations
UDP options are primarily intended for unicast use. Using these UDP options are primarily intended for unicast use. Using these
options over multicast IP requires careful consideration, e.g., to options over multicast IP requires careful consideration, e.g., to
ensure that the options used are safe for different endpoints to ensure that the options used are safe for different endpoints to
interpret differently (e.g., either to support or silently ignore) interpret differently (e.g., either to support or silently ignore)
or to ensure that all receivers of a multicast group confirm support or to ensure that all receivers of a multicast group confirm support
for the options in use. for the options in use.
14. Security Considerations 17. Security Considerations
The use of UDP packets with inconsistent IP and UDP Length fields The use of UDP packets with inconsistent IP and UDP Length fields
has the potential to trigger a buffer overflow error if not properly has the potential to trigger a buffer overflow error if not properly
handled, e.g., if space is allocated based on the smaller field and handled, e.g., if space is allocated based on the smaller field and
copying is based on the larger. However, there have been no reports copying is based on the larger. However, there have been no reports
of such vulnerability and it would rely on inconsistent use of the of such vulnerability and it would rely on inconsistent use of the
two fields for memory allocation and copying. two fields for memory allocation and copying.
UDP options are not covered by DTLS (datagram transport-layer UDP options are not covered by DTLS (datagram transport-layer
security). Despite the name, neither TLS [RFC5246] (transport layer security). Despite the name, neither TLS [RFC8446] (transport layer
security, for TCP) nor DTLS [RFC6347] (TLS for UDP) protect the security, for TCP) nor DTLS [RFC6347] (TLS for UDP) protect the
transport layer. Both operate as a shim layer solely on the payload transport layer. Both operate as a shim layer solely on the payload
of transport packets, protecting only their contents. Just as TLS of transport packets, protecting only their contents. Just as TLS
does not protect the TCP header or its options, DTLS does not does not protect the TCP header or its options, DTLS does not
protect the UDP header or the new options introduced by this protect the UDP header or the new options introduced by this
document. Transport security is provided in TCP by the TCP document. Transport security is provided in TCP by the TCP
Authentication Option (TCP-AO [RFC5925]) or in UDP by the Authentication Option (TCP-AO [RFC5925]) or in UDP by the
Authentication Extension option (Section 5.9). Transport headers are Authentication Extension option (Section 5.10). Transport headers
also protected as payload when using IP security (IPsec) [RFC4301]. are also protected as payload when using IP security (IPsec)
[RFC4301].
UDP options use the TLV syntax similar to that of TCP. This syntax UDP options use the TLV syntax similar to that of TCP. This syntax
is known to require serial processing and may pose a DOS risk, e.g., is known to require serial processing and may pose a DOS risk, e.g.,
if an attacker adds large numbers of unknown options that must be if an attacker adds large numbers of unknown options that must be
parsed in their entirety. Implementations concerned with the parsed in their entirety. Implementations concerned with the
potential for this vulnerability MAY implement only the required potential for this vulnerability MAY implement only the required
options and MAY also limit processing of TLVs. Because required options and MAY also limit processing of TLVs. Because required
options come first and at most once each (with the exception of options come first and at most once each (with the exception of
NOPs, which should never need to come in sequences of more than NOPs, which should never need to come in sequences of more than
three in a row), this limits their DOS impact. Note that when a three in a row), this limits their DOS impact. Note that when a
packet's options cannot be processed, it MUST be discarded; the packet's options cannot be processed, it MUST be discarded; the
packet and its options should always share the same fate. packet and its options should always share the same fate.
15. IANA Considerations 18. IANA Considerations
Upon publication, IANA is hereby requested to create a new registry Upon publication, IANA is hereby requested to create a new registry
for UDP Option Kind numbers, similar to that for TCP Option Kinds. for UDP Option Kind numbers, similar to that for TCP Option Kinds.
Initial values of this registry are as listed in Section 5. Initial values of this registry are as listed in Section 5.
Additional values in this registry are to be assigned by IESG Additional values in this registry are to be assigned by IESG
Approval or Standards Action [RFC8126]. Approval or Standards Action [RFC8126].
Upon publication, IANA is hereby requested to create a new registry Upon publication, IANA is hereby requested to create a new registry
for UDP Experimental Option Experiment Identifiers (UDP ExIDs) for for UDP Experimental Option Experiment Identifiers (UDP ExIDs) for
use in a similar manner as TCP ExIDs [RFC6994]. This registry is use in a similar manner as TCP ExIDs [RFC6994]. This registry is
initially empty. Values in this registry are to be assigned by IANA initially empty. Values in this registry are to be assigned by IANA
using first-come, first-served (FCFS) rules [RFC8126]. using first-come, first-served (FCFS) rules [RFC8126].
16. References 19. References
16.1. Normative References 19.1. Normative References
[Fa19] Fairhurst, G., T. Jones, M. Tuexen, I. Ruengeler, T.
Voelker, "Packetization Layer Path MTU Discovery for
Datagram Transports," draft-ietf-tsvwg-datagram-plpmtud,
Feb. 2019.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997. Requirement Levels," BCP 14, RFC 2119, March 1997.
[RFC768] Postel, J., "User Datagram Protocol", RFC 768, August [RFC768] Postel, J., "User Datagram Protocol," RFC 768, August
1980. 1980.
[RFC791] Postel, J., "Internet Protocol," RFC 791, Sept. 1981. [RFC791] Postel, J., "Internet Protocol," RFC 791, Sept. 1981.
[RFC1122] Braden, R., Ed., "Requirements for Internet Hosts -- [RFC1122] Braden, R., Ed., "Requirements for Internet Hosts --
Communication Layers," RFC 1122, Oct. 1989. Communication Layers," RFC 1122, Oct. 1989.
[RFC1662] Simpson, W. Ed., "PPP in HDLC-like Framing," RFC 1662, [RFC1662] Simpson, W. Ed., "PPP in HDLC-like Framing," RFC 1662,
Oct. 1994. Oct. 1994.
16.2. Informative References 19.2. Informative References
[Fa18] Fairhurst, G., T. Jones, R. Zullo, "Checksum Compensation
Options for UDP Options", draft-fairhurst-udp-options-cco,
Oct. 2018.
[Hi15] Hildebrand, J., B. Trammel, "Substrate Protocol for User [Hi15] Hildebrand, J., B. Trammel, "Substrate Protocol for User
Datagrams (SPUD) Prototype," draft-hildebrand-spud- Datagrams (SPUD) Prototype," draft-hildebrand-spud-
prototype-03, Mar. 2015. prototype-03, Mar. 2015.
[RFC793] Postel, J., "Transmission Control Protocol" RFC 793, [RFC793] Postel, J., "Transmission Control Protocol" RFC 793,
September 1981. September 1981.
[RFC1191] Mogul, J., S. Deering, "Path MTU discovery," RFC 1191, [RFC1191] Mogul, J., S. Deering, "Path MTU discovery," RFC 1191,
November 1990. November 1990.
skipping to change at page 25, line 18 skipping to change at page 28, line 24
[RFC4960] Stewart, R. (Ed.), "Stream Control Transmission Protocol", [RFC4960] Stewart, R. (Ed.), "Stream Control Transmission Protocol",
RFC 4960, September 2007. RFC 4960, September 2007.
[RFC3692] Narten, T., "Assigning Experimental and Testing Numbers [RFC3692] Narten, T., "Assigning Experimental and Testing Numbers
Considered Useful," RFC 3692, Jan. 2004. Considered Useful," RFC 3692, Jan. 2004.
[RFC3828] Larzon, L-A., M. Degermark, S. Pink, L-E. Jonsson (Ed.), [RFC3828] Larzon, L-A., M. Degermark, S. Pink, L-E. Jonsson (Ed.),
G. Fairhurst (Ed.), "The Lightweight User Datagram G. Fairhurst (Ed.), "The Lightweight User Datagram
Protocol (UDP-Lite)," RFC 3828, July 2004. Protocol (UDP-Lite)," RFC 3828, July 2004.
[RFC5246] Dierks, T., E. Rescorla, "The Transport Layer Security
(TLS) Protocol Version 1.2," RFC 5246, Aug. 2008.
[RFC5925] Touch, J., A. Mankin, R. Bonica, "The TCP Authentication [RFC5925] Touch, J., A. Mankin, R. Bonica, "The TCP Authentication
Option," RFC 5925, June 2010. Option," RFC 5925, June 2010.
[RFC6347] Rescorla, E., N. Modadugu, "Datagram Transport Layer [RFC6347] Rescorla, E., N. Modadugu, "Datagram Transport Layer
Security Version 1.2," RFC 6347, Jan. 2012. Security Version 1.2," RFC 6347, Jan. 2012.
[RFC6691] Borman, D., "TCP Options and Maximum Segment Size (MSS)," [RFC6691] Borman, D., "TCP Options and Maximum Segment Size (MSS),"
RFC 6691, July 2012. RFC 6691, July 2012.
[RFC6978] Touch, J., "A TCP Authentication Option Extension for NAT [RFC6978] Touch, J., "A TCP Authentication Option Extension for NAT
skipping to change at page 26, line 5 skipping to change at page 29, line 8
[RFC8126] Cotton, M., B. Leiba, T. Narten, "Guidelines for Writing [RFC8126] Cotton, M., B. Leiba, T. Narten, "Guidelines for Writing
an IANA Considerations Section in RFCs," RFC 8126, June an IANA Considerations Section in RFCs," RFC 8126, June
2017. 2017.
[RFC8200] Deering, S., R. Hinden, "Internet Protocol Version 6 [RFC8200] Deering, S., R. Hinden, "Internet Protocol Version 6
(IPv6) Specification," RFC 8200, Jul. 2017. (IPv6) Specification," RFC 8200, Jul. 2017.
[RFC8201] McCann, J., S. Deering, J. Mogul, R. Hinden (Ed.), "Path [RFC8201] McCann, J., S. Deering, J. Mogul, R. Hinden (Ed.), "Path
MTU Discovery for IP version 6," RFC 8201, Jul. 2017. MTU Discovery for IP version 6," RFC 8201, Jul. 2017.
[RFC8446] Rescorla, E., "The Transport Layer Security (TLS) Protocol
Version 1.3," RFC 8446, Aug. 2018.
[To18ao] Touch, J., "A TCP Authentication Option Extension for [To18ao] Touch, J., "A TCP Authentication Option Extension for
Payload Encryption", draft-touch-tcp-ao-encrypt, Jan. Payload Encryption," draft-touch-tcp-ao-encrypt, Jul.
2018. 2018.
[To18cb] Touch, J., M. Welzl, S. Islam, J. You, "TCP Control Block [To19cb] Touch, J., M. Welzl, S. Islam, J. You, "TCP Control Block
Interdependence," draft-touch-tcpm-2140bis, Jan. 2018. Interdependence," draft-touch-tcpm-2140bis, Jan. 2019.
[Tr16] Trammel, B. (Ed.), M. Kuelewind (Ed.), "Requirements for [Tr16] Trammel, B. (Ed.), M. Kuelewind (Ed.), "Requirements for
the design of a Substrate Protocol for User Datagrams the design of a Substrate Protocol for User Datagrams
(SPUD)," draft-trammell-spud-req-04, May 2016. (SPUD)," draft-trammell-spud-req-04, May 2016.
17. Acknowledgments 20. Acknowledgments
This work benefitted from feedback from Bob Briscoe, Ken Calvert, This work benefitted from feedback from Bob Briscoe, Ken Calvert,
Ted Faber, Gorry Fairhurst, C. M. Heard (including the FRAG/LITE Ted Faber, Gorry Fairhurst, C. M. Heard (including the FRAG/LITE
combination), Tom Herbert, and Mark Smith, as well as discussions on combination), Tom Herbert, and Mark Smith, as well as discussions on
the IETF TSVWG and SPUD email lists. the IETF TSVWG and SPUD email lists.
This work is partly supported by USC/ISI's Postel Center. This work was partly supported by USC/ISI's Postel Center.
This document was prepared using 2-Word-v2.0.template.dot. This document was prepared using 2-Word-v2.0.template.dot.
Authors' Addresses Authors' Addresses
Joe Touch Joe Touch
Manhattan Beach, CA 90266 USA Manhattan Beach, CA 90266 USA
Phone: +1 (310) 560-0334 Phone: +1 (310) 560-0334
Email: touch@strayalpha.com Email: touch@strayalpha.com
Appendix A. Implementation Information Appendix A. Implementation Information
The following information is provided to encourage interoperable API The following information is provided to encourage interoperable API
implementations. implementations.
System-level variables (sysctl): System-level variables (sysctl):
Name default meaning Name default meaning
---------------------------------------------------- ----------------------------------------------------
net.ipv4.udp_opt 0 UDP options available net.ipv4.udp_opt 0 UDP options available
net.ipv4.udp_opt_ocs 1 Default include OCS net.ipv4.udp_opt_ocs 1 Default include OCS
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