Skip to main content

Signaling Use Cases for Traffic Differentiation

Document Type Active Internet-Draft (individual)
Authors Sridharan Rajagopalan , Dan Wing , Mohamed Boucadair , Tirumaleswar Reddy.K
Last updated 2024-03-04
RFC stream (None)
Intended RFC status (None)
Stream Stream state (No stream defined)
Consensus boilerplate Unknown
RFC Editor Note (None)
IESG IESG state I-D Exists
Telechat date (None)
Responsible AD (None)
Send notices to (None)
Transport and Services Working Group                      S. Rajagopalan
Internet-Draft                                                   D. Wing
Intended status: Informational                      Cloud Software Group
Expires: 5 September 2024                                   M. Boucadair
                                                                T. Reddy
                                                            4 March 2024

            Signaling Use Cases for Traffic Differentiation


   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

   This note is to be removed before publishing as an RFC.

   The latest revision of this draft can be found at
   signaling-use-cases.html.  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

Status of This Memo

   This Internet-Draft is submitted in full conformance with the
   provisions of BCP 78 and BCP 79.

Rajagopalan, et al.     Expires 5 September 2024                [Page 1]
Internet-Draft             Signaling Use Cases                March 2024

   Internet-Drafts are working documents of the Internet Engineering
   Task Force (IETF).  Note that other groups may also distribute
   working documents as Internet-Drafts.  The list of current Internet-
   Drafts is at

   Internet-Drafts are draft documents valid for a maximum of six months
   and may be updated, replaced, or obsoleted by other documents at any
   time.  It is inappropriate to use Internet-Drafts as reference
   material or to cite them other than as "work in progress."

   This Internet-Draft will expire on 5 September 2024.

Copyright Notice

   Copyright (c) 2024 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

   This document is subject to BCP 78 and the IETF Trust's Legal
   Provisions Relating to IETF Documents (
   license-info) in effect on the date of publication of this document.
   Please review these documents carefully, as they describe your rights
   and restrictions with respect to this document.  Code Components
   extracted from this document must include Revised BSD License text as
   described in Section 4.e of the Trust Legal Provisions and are
   provided without warranty as described in the Revised BSD License.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   3
   2.  Conventions and Definitions . . . . . . . . . . . . . . . . .   4
   3.  Use Cases . . . . . . . . . . . . . . . . . . . . . . . . . .   4
     3.1.  Priority Between Flows (Inter-Flow) . . . . . . . . . . .   4
       3.1.1.  Abuse and Constraints . . . . . . . . . . . . . . . .   4
     3.2.  Priority Within a Flow (Intra-Flow) . . . . . . . . . . .   5
     3.3.  Key Establishment . . . . . . . . . . . . . . . . . . . .   6
     3.4.  Metadata Version/Capability Exchange  . . . . . . . . . .   6
   4.  Requirements Summary  . . . . . . . . . . . . . . . . . . . .   6
   5.  Security Considerations . . . . . . . . . . . . . . . . . . .   6
   6.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   6
   7.  Informative References  . . . . . . . . . . . . . . . . . . .   6
   Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . .   8
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .   8

Rajagopalan, et al.     Expires 5 September 2024                [Page 2]
Internet-Draft             Signaling Use Cases                March 2024

1.  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".

              +------+  |                     |          |
   +----+     |Wi-Fi |  |  +------+  +------+ | +------+ | +----+
   +----+     |point |  |  +------+  +------+ | +------+ | +----+
              +------+  |                     |          |
                        |                     | Transit  |  Content
      User Network      |    ISP Network      | Network  |  Network

   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".

Rajagopalan, et al.     Expires 5 September 2024                [Page 3]
Internet-Draft             Signaling Use Cases                March 2024

   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 ([I-D.draft-trammell-plus-spec]), UDP
   options ([I-D.draft-kaippallimalil-tsvwg-media-hdr-wireless]),
   overloading the IPv6 Flow Label
   ([I-D.draft-cc-v6ops-wlcg-flow-label-marking], 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 Section 3.3.

   There is consensus that applications can benefit by signaling the
   network ([IAB], [ATIS]).  This document provides use-cases to further
   detail the need of such signaling.

2.  Conventions and Definitions

   Intentional Management:  network policy such as (monthly) bandwidth
      quota or bandwidth limit, or quality (delay and/or jitter))

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

3.  Use Cases

3.1.  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.

3.1.1.  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

Rajagopalan, et al.     Expires 5 September 2024                [Page 4]
Internet-Draft             Signaling Use Cases                March 2024

   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.

3.2.  Priority Within a Flow (Intra-Flow)

   Interactive Audio/Video has long been using [RTP] which runs over
   UDP.  As described in Section of [RFC7478], 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 ([RFC9221],
   [I-D.draft-kpugin-rush]).  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.

Rajagopalan, et al.     Expires 5 September 2024                [Page 5]
Internet-Draft             Signaling Use Cases                March 2024

3.3.  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.

3.4.  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.

4.  Requirements Summary

   TODO summary.

5.  Security Considerations

   TODO Security

6.  IANA Considerations

   This document has no IANA actions.

7.  Informative References

   [ATIS]     "Content Classification for Traffic Optimization", 2023,

              Carder, D. W., Chown, T., McKee, S., and M. Babik, "Use of
              the IPv6 Flow Label for WLCG Packet Marking", Work in

Rajagopalan, et al.     Expires 5 September 2024                [Page 6]
Internet-Draft             Signaling Use Cases                March 2024

              Progress, Internet-Draft, draft-cc-v6ops-wlcg-flow-label-
              marking-02, 10 July 2023,

              Kaippallimalil, J., Gundavelli, S., and S. Dawkins, "Media
              Handling Considerations for Wireless Networks", Work in
              Progress, Internet-Draft, draft-kaippallimalil-tsvwg-
              media-hdr-wireless-04, 14 February 2024,

              Pugin, K., Frindell, A., Ferret, J. C., and J. Weissman,
              "RUSH - Reliable (unreliable) streaming protocol", Work in
              Progress, Internet-Draft, draft-kpugin-rush-02, 10 May
              2023, <

              Trammell, B. and M. K├╝hlewind, "Path Layer UDP Substrate
              Specification", Work in Progress, Internet-Draft, draft-
              trammell-plus-spec-01, 13 March 2017,

   [IAB]      Arkko, J., Hardie, T., Pauly, T., and M. K├╝hlewind,
              "Considerations on Application - Network Collaboration
              Using Path Signals", RFC 9419, DOI 10.17487/RFC9419, July
              2023, <>.

   [RFC7478]  Holmberg, C., Hakansson, S., and G. Eriksson, "Web Real-
              Time Communication Use Cases and Requirements", RFC 7478,
              DOI 10.17487/RFC7478, March 2015,

   [RFC9221]  Pauly, T., Kinnear, E., and D. Schinazi, "An Unreliable
              Datagram Extension to QUIC", RFC 9221,
              DOI 10.17487/RFC9221, March 2022,

   [RTP]      Schulzrinne, H., Casner, S., Frederick, R., and V.
              Jacobson, "RTP: A Transport Protocol for Real-Time
              Applications", STD 64, RFC 3550, DOI 10.17487/RFC3550,
              July 2003, <>.

Rajagopalan, et al.     Expires 5 September 2024                [Page 7]
Internet-Draft             Signaling Use Cases                March 2024


   TODO acknowledge.

Authors' Addresses

   Sridharan Rajagopalan
   Cloud Software Group Holdings, Inc.
   United States of America

   Dan Wing
   Cloud Software Group Holdings, Inc.
   United States of America

   Mohamed Boucadair

   Tirumaleswar Reddy

Rajagopalan, et al.     Expires 5 September 2024                [Page 8]