]> Ericsson AB

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TSV Masque Working Group masque datagram multipath 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 a masque endpoint to implement reordering logic specific to its needs. About This Document The latest revision of this draft can be found at . Status information for this document may be found at . Discussion of this document takes place on the WG Working Group mailing list (), which is archived at . Source for this draft and an issue tracker can be found at .

Introduction This document defines a sequence number extension to HTTP datagrams . 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, e.g. using the multipath QUIC extension . The extension applies to HTTP datagrams when they are used with the extended CONNECT method and the protocols are either connect-ip or connect-udp .

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 when, and only when, they appear in all capitals, as shown here.

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 can not share a common sequence number space.

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 for information about the boolean format.). A new datagram sequence is registered by sending a REGISTER_SEQUENCE_CONTEXT capsule. The capsule has the following fields: Context ID: Identifies a sequence number context. 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. It is possible to use multiple contexts for a single sequence, this is needed if multiple datagram payload formats are used in parallel. To add a context to an existing sequence an endpoint sends an ADD_SEQUENCE_CONTEXT Capsule. The capsule has the following fields: Sequence Context: Identifies the original sequence number context. Context ID: A new context identifier that refers to the same sequence identified by the Sequence Context ID. Payload Context ID: Identifies the type of payload that follows a sequence number. The value MUST be equal to a previously registered Context ID.

Datagram Format A Sequence Number Datagrams has the following format: 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.

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.

IANA Considerations

Capsule types This document adds following entries to the "HTTP Capsule Types" registry:

Capsule Type	Value	Specification
REGISTER_SEQUENCE_CONTEXT	TBD	(This document)
ADD_SEQUENCE_CONTEXT	TBD	(This document)

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)

References Normative References This document describes HTTP Datagrams, a convention for conveying multiplexed, potentially unreliable datagrams inside an HTTP connection. In HTTP/3, HTTP Datagrams can be sent unreliably using the QUIC DATAGRAM extension. When the QUIC DATAGRAM frame is unavailable or undesirable, HTTP Datagrams can be sent using the Capsule Protocol, which is a more general convention for conveying data in HTTP connections. HTTP Datagrams and the Capsule Protocol are intended for use by HTTP extensions, not applications. Apple Inc. Google LLC Google LLC Ericsson Ericsson This document describes a method of proxying IP packets over HTTP. This protocol is similar to CONNECT-UDP, but allows transmitting arbitrary IP packets, without being limited to just TCP like CONNECT or UDP like CONNECT-UDP. This document describes how to proxy UDP in HTTP, similar to how the HTTP CONNECT method allows proxying TCP in HTTP. More specifically, this document defines a protocol that allows an HTTP client to create a tunnel for UDP communications through an HTTP server that acts as a proxy. In many standards track documents several words are used to signify the requirements in the specification. These words are often capitalized. This document defines these words as they should be interpreted in IETF documents. This document specifies an Internet Best Current Practices for the Internet Community, and requests discussion and suggestions for improvements. RFC 2119 specifies common key words that may be used in protocol specifications. This document aims to reduce the ambiguity by clarifying that only UPPERCASE usage of the key words have the defined special meanings. This document describes a set of data types and associated algorithms that are intended to make it easier and safer to define and handle HTTP header and trailer fields, known as "Structured Fields", "Structured Headers", or "Structured Trailers". It is intended for use by specifications of new HTTP fields that wish to use a common syntax that is more restrictive than traditional HTTP field values. Informative References Alibaba Inc. Alibaba Inc. UCLouvain UCLouvain and Tessares Private Octopus Inc. Ericsson This document specifies a multipath extension for the QUIC protocol to enable the simultaneous usage of multiple paths for a single connection. Discussion Venues This note is to be removed before publishing as an RFC. Discussion of this document takes place on the QUIC Working Group mailing list (quic@ietf.org), which is archived at https://mailarchive.ietf.org/arch/browse/quic/. Source for this draft and an issue tracker can be found at https://github.com/mirjak/draft-lmbdhk-quic-multipath.

Acknowledgments TODO acknowledge.