Internet DRAFT - draft-ihlar-masque-datagram-numbers
draft-ihlar-masque-datagram-numbers
Masque Working Group M. Ihlar
Internet-Draft Ericsson AB
Intended status: Standards Track M. Westerlund
Expires: 11 January 2024 Ericsson
10 July 2023
A Sequence Number Extension for HTTP Datagrams
draft-ihlar-masque-datagram-numbers-02
Abstract
This document defines a sequence number extension to HTTP datagrams
used to carry proxied UDP payload or IP datagrams. This extension is
useful when HTTP datagrams are transported on top of a multipath
protocol that does not ensure in-order delivery as it allows for
example a masque endpoint to implement reordering logic specific to
its needs.
About This Document
This note is to be removed before publishing as an RFC.
Status information for this document may be found at
https://datatracker.ietf.org/doc/draft-ihlar-masque-datagram-
numbers/.
Discussion of this document takes place on the WG Working Group
mailing list (mailto:masque@ietf.org), which is archived at
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https://www.ietf.org/mailman/listinfo/masque/.
Source for this draft and an issue tracker can be found at
https://github.com/ihlar/draft-ihlar-masque-datagram-numbers.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
1.1. ATSSS . . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Conventions and Definitions . . . . . . . . . . . . . . . . . 4
3. Sequence Number Datagram Extension . . . . . . . . . . . . . 4
3.1. Registration . . . . . . . . . . . . . . . . . . . . . . 4
3.2. Datagram Format . . . . . . . . . . . . . . . . . . . . . 5
4. Security Considerations . . . . . . . . . . . . . . . . . . . 6
5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 6
5.1. Capsule types . . . . . . . . . . . . . . . . . . . . . . 6
5.2. HTTP headers . . . . . . . . . . . . . . . . . . . . . . 7
6. References . . . . . . . . . . . . . . . . . . . . . . . . . 7
6.1. Normative References . . . . . . . . . . . . . . . . . . 7
6.2. Informative References . . . . . . . . . . . . . . . . . 8
Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . . 8
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 8
1. Introduction
This document defines a sequence number extension to HTTP datagrams
[RFC9297]. Sequence numbers at the HTTP datagram layer allows a
receiving endpoint to implement arbitrary reordering logic, which can
be useful when proxied datagrams are sent over multiple paths
simultaneously, such as when using the multipath QUIC extension
[MPQUIC]. The extension applies to HTTP datagrams and specifices its
use with the extended CONNECT method, and the protocols connect-ip
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[CONNECT-IP] and connect-udp [RFC9298].
1.1. ATSSS
This extension is motivated by the Access Traffic Steering,
Switching, and Splitting (ATSSS) feature outlined for the 5G System
by 3GPP in section 5.32 of [_3GPPTS23.501].
ATSSS, an optional feature of the 5G system, permits the concurrent
usage of 3GPP and non-3GPP accesses within a single PDU session.
This is managed by a number of steering functionalities and modes,
determining the types of supported concurrent path usage. As of
Release 18 of the 5G System Architecture specification, three
steering functionalities have been defined for ATSSS: ATSSS-LL,
MPTCP, and Multipath QUIC.
ATSSS-LL, a "Lower Layer Functionality," operates beneath the IP
layer. It's capable of steering to one path, switching from one path
to another, and splitting all traffic types, encompassing both IP and
Ethernet PDU sessions. However, it doesn't support splitting a
single traffic flow among multiple paths. In contrast, MPTCP and
Multipath QUIC, termed as "Higher Layer Functionalities," operate
above the IP layer, steering, switching, and splitting TCP and UDP
traffic respectively.
The Multipath QUIC steering functionality uses multipath capable
HTTP3 proxies supporting the extended CONNECT method with the
connect-udp protocol. It establishes two datagram modes for UDP
payload encapsulation. The default mode sends HTTP datagrams
unreliably over QUIC datagrams, while the optional mode encapsulates
UDP payload in HTTP datagrams augmented with sequence numbers.
Steering modes influence how traffic flows utilize concurrent paths.
Load Balancing traffic steering and Redundant traffic steering are
two modes where sequence numbers prove beneficial.
The Load Balancing steering mode involves parallel transmission over
the 3GPP and non-3GPP accesses, a process often referred to as
bandwidth aggregation. Distributing data transmission over multiple
paths, while increasing available bandwidth, can result in out-of-
order packet delivery. The impact of packet disorder is largely
dependent on the properties of the protocols and applications
conveyed over the proxied payload. Negative effects of large degrees
of packet reordering may include increased frequency of packet
acknowledgements, inaccurate loss detection and spurious
retransmissions. By buffering out-of-order data, an ATSSS endpoint
can reconcile path latency differences and reduce the volume of data
delivered out-of-order to the final endpoints. Furthermore, an ATSSS
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endpoint can set an upper bound on the time packets are delayed in
its reorder buffer, thus incurring less packet delay variation in the
face of loss than if the proxied payload is encoded over reliable
streams. Which datagram mode is used for load balancing traffic
steering depends on application requirements expressed as ATSSS
rules.
With the Redundant steering mode proxied payload is duplicated over
the 3GPP and non-3GPP accesses. Despite the added cost, this
steering mode is useful for applications and users with stringent
availability requirements. Data duplication at one end necessitates
de-duplication at the other. This can be efficiently accomplished
through sequence numbering, which provides a straightforward method
for de-duplication.
2. Conventions and Definitions
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 notational conventions described in Section 1.3 of
[RFC9000].
3. Sequence Number Datagram Extension
The Sequence Number datagram extension prepends sequence numbers to
HTTP datagrams. Datagram sequence numbers are unsigned integers
initiated to 0 and are incremented by 1 for every transmitted HTTP
datagram, except for when the integer overflows and is reset to 0.
The extension can be used with the HTTP CONNECT method when the
:protocol pseudo header is equal to "connect-udp" or "connect-ip".
Use of the sequence number extension is determined per request, and
the scope of a datagram sequence is limited to a single request
stream. Datagrams with different quarter stream IDs have distinct
sequence number spaces.
3.1. Registration
Endpoints indicate support for Sequence Number Datagram type by
including the boolean-valued Item Structured Field "DG-Sequence: ?1"
in the HTTP Request and Response headers (See Section 3.3.6 of
[RFC8941] for information about the boolean format.).
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A datagram sequence is registered by sending a
REGISTER_SEQUENCE_CONTEXT capsule. An endpoint MAY send multiple
REGISTER_SEQUENCE_CONTEXT capsules in order to support multiple
payload formats.
REGISTER_SEQUENCE_CONTEXT Capsule {
Type (i) = REGISTER_SEQUENCE_CONTEXT,
Length (i),
Context ID (i),
Payload Context ID (i),
[Representation (8)]
}
The capsule has the following fields:
Context ID: Identifies a sequence number context. The value MUST be
unique within the scope of a request stream.
Payload Context ID: Identifies the type of payload that follows a
sequence number. The value MUST be equal to a previously registered
Context ID.
Representation: The size in bits of the unsigned interger used to
encode the sequence number, the value MUST be one of the following:
8, 16, 32 or 64. This field MUST be present in the first
REGISTER_SEQUENCE_CONTEXT capsule sent on a request stream and it MAY
be omitted in subsequent capsules.
3.2. Datagram Format
A Sequence Number Datagram has the following format:
Sequence Number Datagram {
Context ID (i),
Sequence Number (8..64),
Payload (..)
}
Context ID: This value indicates that the datagram contains a
sequence number and the format of the data that follows the sequence
number.
Sequence Number: Unsigned integer of size specified in registration,
indicates the transmission order of the datagagram.
Payload: Datagram payload.
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4. Security Considerations
Although the usage of the sequence number is not defined by this
specification, there is an underlying assumption that the sequence
numbers are assigned in transmission order of HTTP datagram sent in
the context of this HTTP request. Any attacker that can break that
assumption will thus impact any node that uses the sequence number.
By altering the sequence number in HTTP datagrams, an attacker can
impact how much data a receiver is buffering for the following
purposes:
* Resource exhaustion attack by maximizing the amount of data
buffered in each HTTP request context
* Introducing reordering, jitter and additional delay in the path
properties for these datagram
* Cause the sequence number using node to drop some HTTP Datagrams
by causing them to be so far reordered that some policy in the
receiving node drops the datagram.
A malicious endpoint is more likely to mount a resource exhaustion
attack, while HTTP intermediares could be used by an third party
attacker to impact the HTTP datagram flow between a source and a
destination.
A user that buffers datagrams based on sequence numbers should ensure
that they have protection against resource exhaustion attacks by
limiting the size of their buffers.
5. IANA Considerations
5.1. Capsule types
This document adds following entries to the "HTTP Capsule Types"
registry:
+===========================+=======+=================+
| Capsule Type | Value | Specification |
+===========================+=======+=================+
| REGISTER_SEQUENCE_CONTEXT | TBD | (This document) |
+---------------------------+-------+-----------------+
Table 1: New Capsule Type to register
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5.2. HTTP headers
This document adds following entry to the "Hypertext Transfer
Protocol (HTTP) Field Name Registry":
+=============+==========+===========+=================+==========+
| Field Name | Template | Status | Reference | Comments |
+=============+==========+===========+=================+==========+
| DG-Sequence | | permanent | (This document) | |
+-------------+----------+-----------+-----------------+----------+
Table 2: HTTP Field Name to register
6. References
6.1. Normative References
[CONNECT-IP]
Pauly, T., Schinazi, D., Chernyakhovsky, A., Kühlewind,
M., and M. Westerlund, "Proxying IP in HTTP", Work in
Progress, Internet-Draft, draft-ietf-masque-connect-ip-13,
28 April 2023, <https://datatracker.ietf.org/doc/html/
draft-ietf-masque-connect-ip-13>.
[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/rfc/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/rfc/rfc8174>.
[RFC8941] Nottingham, M. and P. Kamp, "Structured Field Values for
HTTP", RFC 8941, DOI 10.17487/RFC8941, February 2021,
<https://www.rfc-editor.org/rfc/rfc8941>.
[RFC9000] Iyengar, J., Ed. and M. Thomson, Ed., "QUIC: A UDP-Based
Multiplexed and Secure Transport", RFC 9000,
DOI 10.17487/RFC9000, May 2021,
<https://www.rfc-editor.org/rfc/rfc9000>.
[RFC9297] Schinazi, D. and L. Pardue, "HTTP Datagrams and the
Capsule Protocol", RFC 9297, DOI 10.17487/RFC9297, August
2022, <https://www.rfc-editor.org/rfc/rfc9297>.
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[RFC9298] Schinazi, D., "Proxying UDP in HTTP", RFC 9298,
DOI 10.17487/RFC9298, August 2022,
<https://www.rfc-editor.org/rfc/rfc9298>.
6.2. Informative References
[MPQUIC] Liu, Y., Ma, Y., De Coninck, Q., Bonaventure, O., Huitema,
C., and M. Kühlewind, "Multipath Extension for QUIC", Work
in Progress, Internet-Draft, draft-ietf-quic-multipath-04,
13 March 2023, <https://datatracker.ietf.org/doc/html/
draft-ietf-quic-multipath-04>.
[_3GPPTS23.501]
3rd Generation Partnership Project, "System architecture
for the 5G System (5GS) - Release 18", July 2023,
<https://www.3gpp.org/ftp/Specs/
archive/23_series/23.501/23501-i22.zip>.
Acknowledgments
TODO acknowledge.
Authors' Addresses
Marcus Ihlar
Ericsson AB
Email: marcus.ihlar@ericsson.com
Magnus Westerlund
Ericsson
Email: magnus.westerlund@ericsson.com
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