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Web and Internet Transport Transport and Services Working Group user experience bandwidth priority enriched feedback media streaming realtime media QoS 5G Wi-Fi WiFi diffserv Host-to-network signaling can improve the user experience by informing the network which flows are more important and which packets within a flow are more important. The differentiated service may be provided at the network (e.g., packet prioritization), the sender (e.g., adaptive transmission), or through cooperation of both the sender and the network. This document outlines use-cases that highlight the need for a new signaling protocol from the receiver to its network elements which enables different traffic treatment. 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 Transport and Services Working Group Working Group mailing list (), which is archived at . Subscribe at . Source for this draft and an issue tracker can be found at .

Introduction Bandwidth constraints exist most predominently at the access network. Users of those networks run various hosts which run various applications, each having different needs for the best user experience. These requirements are not fixed but change over time depending on the application and even depending on how the application is used. The simple network diagram below shows where such bandwidth and performance constraints usually exist with a "B". For traffic sent in either direction, the network network element(s) immediately prior to the bandwidth constraining link can be augmented with flow metadata. Such augmentation allows those network elements to make autonomous decisions to prioritize, delay, or drop packets especially to when performing Reactive Management. A difficulty with this metadata augmentation is deciding which metadata to trust. Traffic arriving from a content provider cannot be differentiated from traffic arriving from other hosts on the Internet. The metadata signals from the content provider are more likely to be authentic but the metadata signals from other hosts may be wrong, undesired by the local host, or maliciously contain improper metadata. Attempts to automate identification of content providers have included HTTP "Host" header inspection and TLS SNI inspection which are expected to fail as encrypted SNI and privacy-enhancin MASQUE proxies become more prevalant. A remaining mechanism to authorize metadata signals from the content provider is to configure the ISP equipment with the content network's source IP addresses and provide only that traffic with differentiated service. However, such an arrangement benefits large players (large ISPs and large content network) and disadvantages small players (and new players). A more egalitarian approach would provide the same benefit to all parties -- large and small -- and also provide richer signaling to further improve user experience and metadata interoperability. This would allow all parties to become part of the "Internet fast lane". The authorization problem exists with technologies as relatively simple as DiffServ and the problem persists with many other recently discussed metadata signaling mechanisms including embedding information in the UDP payload (), UDP options (), overloading the IPv6 Flow Label (, and Hop-by-Hop Options. One mechanism suggested occasionally is to encrypt or integrity protect the metadata with a key; such a key could be established with a signaling protocol, see . There is consensus that applications can benefit by signaling the network (, ). This document provides use-cases to further detail the need of such signaling.

Conventions and Definitions

Intentional Management:

network policy such as (monthly) bandwidth quota or bandwidth limit, or quality (delay and/or jitter)) assurances.

Reactive Management:

network reactions to congestion events, with very short to very long durations (e.g., varying wireless and mobile air interface conditions).

Use Cases

Priority Between Flows (Inter-Flow) Certain flows being received by an host or by an application are less or more important than other flows. For example, a host downloading a software update is generally considered less important than another host doing interactive audio/video or gaming. By signaling the relative importance of flows to a network element (e.g., router, MASQUE proxy), the network element can (de-)prioritize those flows to best accomodate the needs of the various applications (on a single host) and between hosts on a network.

Abuse and Constraints It is important that not every flow be prioritized; otherwise, the network devolves into the best-effort network that existed prior to metadata signaling. It is a requirement that mechanisms exist to prevent this occurrence. The mechanism might be simple, for example a cellular network might allow one flow from a subscriber to declare itself as important; other flows with that subscriber are denied attempts to prioritize themselves. The mechanism might be more complex where authentication and authorization is performed by an enterprise network which, itself, decides which flows are important based on its policy and only the enterprise network communicates flow priorities to the ISP network. The enterprise might prioritize certain users (e.g., IT staff, CEO), certain equipment (audio/video equipment in a conference room), or whatever its policies it might want.

Interactive Media Examples: VoIP, gaming, virtual desktop. Requirement: Signal the flow needs low jitter and low delay. However, the network can only provide a limited amount of low jitter/low delay to each host, maybe as few as one. This requires signaling feedback indicating that low jitter and low delay flows are already subscribed to other hosts. In response, the user and the application will likely continue, occasionally re-attempting to get the desired quality of service from the network. Todo: this section on cooperation needs editing.

Bulk Data Transfer Examples: backup/restore, software update, RSS feed update, email Requirement: Signal the flow as below best-effort.

Priority Within a Flow (Intra-Flow) Interactive Audio/Video has long been using which runs over UDP. As described in , there is value in differentiating between voice, video and data. Today's video streaming is exclusively over TCP but will migrate to QUIC and eventually is likely to support unreliable transport (, ). With unreliable transport of video in RTP or QUIC, it is beneficial to differentiate the important video keyframes from other video frames. Other applications such as gaming and remote desktop also benefit from differentiating their packets to the network. Many of these flows do not originate from a content provider's network. Thus, the flows originate from an IP address that is not known before connection establishment, so there needs to be a way for the client to authorize the network elements to honor the metadata of those packets.

Key Establishment Various proposals have suggested establishing a key to validate per-packet metadata or to decrypt per-packet metadata. However, most proposals have not specified how this key would be established. A signaling protocol from the receiving host to its ISP could establish such a key. The host can then convey the key to the sending host to use to integrity protect or encrypt the per-packet metadata.

• Note: The CPU overhead of validating or decrypting such per-packet metadata needs to be carefully considered by the signaling protocol proposing such keying.

Metadata Version/Capability Exchange The sender has to convey metadata in a way that is understood by the various network elements on the path -- each of which might be operated by different entities and have different capabilities. For example, the Wi-Fi access point might be operated by an enterprise network, hotel, or home user, whereas the ISP's router is operated by the ISP. Each of those might support different versions of the same metadata, or might need the metadata expressed in different ways. The signaling protocol would provide a way to learn the needs of those networks, and provide metadata signaling satisfying most or all of their needs.

Requirements Summary TODO summary.

Security Considerations TODO Security

IANA Considerations This document has no IANA actions.

Informative References ETH Zurich ETH Zurich This document specifies a common Path Layer UDP Substrate (PLUS) wire image for encrypted transport protocols carried over UDP. The base PLUS header carries information for driving a minimal state machine at middleboxes described in [I-D.trammell-plus-statefulness], and provides optional exposure of additional information to devices along the path using the mechanism described in [I-D.trammell-plus-abstract-mech]. Futurewei Cisco Tencent America LLC Wireless networks like 5G cellular or Wi-Fi experience significant variations in link capacity over short intervals due to wireless channel conditions, interference, or the end-user's movement. These variations in capacity take place in the order of hundreds of milliseconds and is much too fast for end-to-end congestion signaling by itself to convey the changes for an application to adapt. Media applications on the other hand demand both high throughput and low latency, and may adjust the size and quality of a stream to network bandwidth available or dynamic change in content coded. However, catering to such media flows over a radio link with rapid changes in capacity requires the buffers and congestion to be managed carefully. Wireless networks need additional information to manage radio resources optimally to maximize network utilization and application performance. This draft provides requirements on metadata about the media transported, its scalability, privacy, and other related considerations. Energy Sciences Network Jisc University of Michigan CERN This document describes an experimentally deployed approach currently used within the Worldwide Large Hadron Collider Computing Grid (WLCG) to mark packets with their project (experiment) and application. The marking uses the 20-bit IPv6 Flow Label in each packet, with 15 bits used for semantics (community and activity) and 5 bits for entropy. Alternatives, in particular use of IPv6 Extension Headers (EH), were considered but found to not be practical. The WLCG is one of the largest worldwide research communities and has adopted IPv6 heavily for movement of many hundreds of PB of data annually, with the ultimate goal of running IPv6 only. This document discusses principles for designing mechanisms that use or provide path signals and calls for standards action in specific valuable cases. RFC 8558 describes path signals as messages to or from on-path elements and points out that visible information will be used whether or not it is intended as a signal. The principles in this document are intended as guidance for the design of explicit path signals, which are encouraged to be authenticated and include a minimal set of parties to minimize information sharing. These principles can be achieved through mechanisms like encryption of information and establishing trust relationships between entities on a path. This memorandum describes RTP, the real-time transport protocol. RTP provides end-to-end network transport functions suitable for applications transmitting real-time data, such as audio, video or simulation data, over multicast or unicast network services. RTP does not address resource reservation and does not guarantee quality-of- service for real-time services. The data transport is augmented by a control protocol (RTCP) to allow monitoring of the data delivery in a manner scalable to large multicast networks, and to provide minimal control and identification functionality. RTP and RTCP are designed to be independent of the underlying transport and network layers. The protocol supports the use of RTP-level translators and mixers. Most of the text in this memorandum is identical to RFC 1889 which it obsoletes. There are no changes in the packet formats on the wire, only changes to the rules and algorithms governing how the protocol is used. The biggest change is an enhancement to the scalable timer algorithm for calculating when to send RTCP packets in order to minimize transmission in excess of the intended rate when many participants join a session simultaneously. [STANDARDS-TRACK] This document describes web-based real-time communication use cases. Requirements on the browser functionality are derived from the use cases. This document was developed in an initial phase of the work with rather minor updates at later stages. It has not really served as a tool in deciding features or scope for the WG's efforts so far. It is being published to record the early conclusions of the WG. It will not be used as a set of rigid guidelines that specifications and implementations will be held to in the future. This document defines an extension to the QUIC transport protocol to add support for sending and receiving unreliable datagrams over a QUIC connection. Facebook Facebook Facebook Facebook RUSH is an application-level protocol for ingesting live video. This document describes the protocol and how it maps onto QUIC. Discussion Venues This note is to be removed before publishing as an RFC. Discussion of this document takes place on the mailing list (), which is archived at . Source for this draft and an issue tracker can be found at https://github.com/afrind/draft-rush.

Acknowledgments TODO acknowledge.