]> Cloud Software Group Holdings, Inc.

United States of America danwing@gmail.com https://www.cloud.com

Nokia

Bangalore Karnataka India kondtir@gmail.com

Orange

Rennes 35000 France mohamed.boucadair@orange.com

Network Network Working Group user experience bandwidth priority enriched feedback media streaming realtime media QoS 5G Wi-Fi WiFi DTLS Connection Identifier DTLS-SRTP QUIC Connection Identifier QUIC Host-to-network signaling and network-to-host signaling can improve the user experience to adapt to network's constraints and share expected application needs, and thus to provide differentiated service to a flow and to packets within a flow. The differentiated service may be provided at the network (e.g., packet prioritization), the server (e.g., adaptive transmission), or both. Such an approach is called CIDFI, for Collaborative and Interoperable Dissemination of Flow Indicators. A key component in a CIDFI system is to discover whether a network is CIDFI-capable, and if so discover a set of CIDFI-aware Network Elements (CNEs) that will be involved in the Host-to-network signaling and network-to-host signaling. This document discusses a set of discovery methods. 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 TSV Area Working Group mailing list (), which is archived at . Subscribe at . Source for this draft and an issue tracker can be found at .

Introduction Senders rely on ramping up their transmission rate until they encounter packet loss or see indicating they should level off or slow down their transmission rate. This feedback takes time and contributes to poor user experience when the sender over- or under-shoots the actual available bandwidth, especially if the sender changes fidelity of the content (e.g., improves video quality which consumes more bandwidth which then gets dropped by the network). This is also called an 'intentional management policy'. Due to network constraints a network element will need to drop or even prioritize a packet ahead of other packets within the same UDP 4-tuple. The decision of which packet to drop or prioritize is improved if the network element knows the importance of the packet. By mapping packet metadata to a network-visible field in each packet, the network element is better informed and better able to improve the user experience. There are also exceptional cases (crisis) where "normal" network resources cannot be used at maximum and, thus, a network would seek to reduce or offload some of the traffic during these events -- often called 'reactive traffic policy'. Network-to-host signals are useful to put in place adequate traffic distribution policies (e.g., prefer the use of alternate paths or offload a network). defines a generic framework, called CIDFI (pronounced "sid fye"), which is a system of several protocols that allows communicating about a connection from the network to a host and the host to the network. For example, this mechanism can be used by a host to signal packet importance to a network element. Overall, the following main steps are involved in CIDFI; some of them are optional:

• CIDFI-awareness discovery between a host and a network.
• Establishment of a secure association with all or a subset of CIDFI-aware networks.
• Negotiation of CIDFI support with remote servers.
• CIDFI-aware networks sharing of changes of network conditions.
• CIDFI-aware clients sharing of metadata with CIDFI-aware networks as hints to help processing flows.
• CIDFI-aware clients sharing of metadata with CIDFI-aware server to adapt to local network conditions.

This document focuses on the discovery step. On initial network attach topology change, the client learns if the network supports CIDFI () and authorizes discovered network elements () as a function of a local policy.

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. The document makes use of the following terms:

CNE:

CIDFI-aware Network Element, a network element that supports this CIDFI specification. This is typically a router.

Differentiated service:

Refers to a differentiated processing that can be provided to a flow (or specific packets within a flow) by a network, client, or server.

Examples of differentiated service are: prioritization, adaptive transmission, or traffic steering.

Network Configuration to Support CIDFI The network is configured to advertise its support for CIDFI. For this step, four mechanisms are described in this document: DNS SVCB records , IPv6 Provisioning Domains (PvD) , DHCP , and 3GPP PCO. These are described in the following sub-sections.

• Standardizing all or some of these mechanisms is for further discussion.

DNS SVCB Records This document defines a new DNS Service Binding parameter "cidfi-aware" in and a new Special-Use Domain Name "cidfi.arpa" in . The local network is configured to respond to DNS SVCB queries with ServiceMode () for "_cidfi-aware.cidfi.arpa" with the DNS names of that network's and upstream network's CIDFI-aware network elements (CNEs). If upstream networks also support CIDFI (e.g., the ISP network) those SVCB records are aggregated into the local DNS server's response by the local network's recursive DNS resolvers. For example, a query for "_cidfi-aware.cidfi.arpa" might return two answers for the two CNEs on the local network, one belonging to the local ISP (example.net) and the other belonging to the local Wi-Fi network (example.com).

Example of SVCB Records

When multihoming, the multihome-capable CPE aggregates all upstream networks' "_cidfi-aware.cidfi.arpa" responses into the response sent to its locally-connected clients.

Provisioning Domains The CIDFI networks are configured to set the H-flag so clients can request PvD Additional Information (). The "application/pvd+json" returned looks like what is depicted in when there are two CIDFI-aware network elements, service-cidfi and wi-fi.

Example of PvD Information

Multiple CIDFI-aware network elements on a network path will require propagating the Provisioning Domain Additional Information. For example, a CIDFI-aware Wi-Fi access point connected to a CIDFI-aware 5G network will require the information for both CIDFI networks be available to the client, in a single Provisioning Domain Additional Information request. This means the Wi-Fi access point has to obtain that information so the Wi-Fi access point can provide both the 5G network's information and the Wi-Fi access point's information.

DHCP or 3GPP PCO The network is configured to respond to DHCPv6, DHCPv4 sub-option, or 3GPP PCO (Protocol Configuration Option) Information Element.

Client Learns Local Network Supports CIDFI For this step, four mechanisms are identified: DNS SVCB records, IPv6 PvD, DHCP, or 3GPP PCO. These are described in the following sub-sections. In all cases below,

• if the discovery succeeds (i.e., the client concludes that the local and/or ISP network support CIDFI) client processing proceeds to .
• if the discovery failed (i.e., the client concludes that the local network and ISP do not support CIDFI) client processing stops.

Client Learns Using DNS SVCB The client determines if the local network provides CIDFI service by issuing a query to the local DNS server for "_cidfi-aware.cidfi.arpa." with the SVCB resource record type (64) .

Client Learns Using Provisioning Domain The client determines if the local network supports CIDFI by querying https://<PvD-ID>/.well-known/pvd as described in .

Client Learns Using DHCP or 3GPP PCO The client determines that a local network is CIDFI-capable if the client receives an explicit signal from the network, e.g., via a dedicated DHCP option or a 3GPP PCO (Protocol Configuration Option) Information Element. An example of explicit signal would be a DHCPv6 option or DHCPv4 sub-option that that is returned as part of .

Client Authorizes CIDFI-aware Network Elements The client authorizes each of the CNEs using a local policy. This policy is implementation-specific. An implementation example might have the users authorize their ISP's CIDFI server (e.g., allow "cidfi.example.net" if a user's ISP is configured with "example.net"). Similarly, if none of the CNEs are recognized by the client, the client might silently avoid using CIDFI on that network.

Security Considerations TBC.

IANA Considerations

New Well-known URI "cidfi-aware" This document requests IANA to register the new well-known URI "cidfi" in the "Well-Known URIs" registry available at .

New Special-use Domain Name This document requests IANA to register new a special-use domain name cidfi.arpa for DNS SVCB discovery.

New DNS Service Binding (SVCB) This document requests IANA to register the new DNS SVCB "_cidfi-aware" in the "DNS Service Bindings (SVCB)" registry available at . The document also requests IANA to register the following service parameter in the "Service Parameter Keys (SvcParamKeys)" registry :

Number:

TBD

Name:

min-ttl

Meaning: :The minimum IPv4 TTL or IPv6 Hop Limit to use for a connection.

Reference:

This-Document

New Provisioning Domain Additional Information Key This document requests IANA to register a new JSON key in the Provisioning Domains Additional Information registry at : Additionally, this document requests creating a new registry, entitled "CIDFI JSON Keys" under the Provisioning Domains Additional Information registry group . The policy for assigning new entries in this registry is Expert Review . The structure of this registry is identical to the Provisioning Domains Additional Information registry group. The initial content of this registry is provided below:

References Normative References 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 specifies the "SVCB" ("Service Binding") and "HTTPS" DNS resource record (RR) types to facilitate the lookup of information needed to make connections to network services, such as for HTTP origins. SVCB records allow a service to be provided from multiple alternative endpoints, each with associated parameters (such as transport protocol configuration), and are extensible to support future uses (such as keys for encrypting the TLS ClientHello). They also enable aliasing of apex domains, which is not possible with CNAME. The HTTPS RR is a variation of SVCB for use with HTTP (see RFC 9110, "HTTP Semantics"). By providing more information to the client before it attempts to establish a connection, these records offer potential benefits to both performance and privacy. Provisioning Domains (PvDs) are defined as consistent sets of network configuration information. PvDs allows hosts to manage connections to multiple networks and interfaces simultaneously, such as when a home router provides connectivity through both a broadband and cellular network provider. This document defines a mechanism for explicitly identifying PvDs through a Router Advertisement (RA) option. This RA option announces a PvD identifier, which hosts can compare to differentiate between PvDs. The option can directly carry some information about a PvD and can optionally point to PvD Additional Information that can be retrieved using HTTP over TLS. The Dynamic Host Configuration Protocol (DHCP) provides a framework for passing configuration information to hosts on a TCPIP network. DHCP is based on the Bootstrap Protocol (BOOTP), adding the capability of automatic allocation of reusable network addresses and additional configuration options. [STANDARDS-TRACK] This document describes the Dynamic Host Configuration Protocol for IPv6 (DHCPv6): an extensible mechanism for configuring nodes with network configuration parameters, IP addresses, and prefixes. Parameters can be provided statelessly, or in combination with stateful assignment of one or more IPv6 addresses and/or IPv6 prefixes. DHCPv6 can operate either in place of or in addition to stateless address autoconfiguration (SLAAC). This document updates the text from RFC 3315 (the original DHCPv6 specification) and incorporates prefix delegation (RFC 3633), stateless DHCPv6 (RFC 3736), an option to specify an upper bound for how long a client should wait before refreshing information (RFC 4242), a mechanism for throttling DHCPv6 clients when DHCPv6 service is not available (RFC 7083), and relay agent handling of unknown messages (RFC 7283). In addition, this document clarifies the interactions between models of operation (RFC 7550). As such, this document obsoletes RFC 3315, RFC 3633, RFC 3736, RFC 4242, RFC 7083, RFC 7283, and RFC 7550. Many protocols make use of points of extensibility that use constants to identify various protocol parameters. To ensure that the values in these fields do not have conflicting uses and to promote interoperability, their allocations are often coordinated by a central record keeper. For IETF protocols, that role is filled by the Internet Assigned Numbers Authority (IANA). To make assignments in a given registry prudently, guidance describing the conditions under which new values should be assigned, as well as when and how modifications to existing values can be made, is needed. This document defines a framework for the documentation of these guidelines by specification authors, in order to assure that the provided guidance for the IANA Considerations is clear and addresses the various issues that are likely in the operation of a registry. This is the third edition of this document; it obsoletes RFC 5226. Informative References This memo specifies the incorporation of ECN (Explicit Congestion Notification) to TCP and IP, including ECN's use of two bits in the IP header. [STANDARDS-TRACK] Cloud Software Group Holdings, Inc. Nokia Orange Host-to-network signaling and network-to-host signaling can improve the user experience to adapt to network's constraints and share expected application needs, and thus to provide differentiated service to a flow and to packets within a flow. The differentiated service may be provided at the network (e.g., packet prioritization), the server (e.g., adaptive transmission), or both. This document describes how clients can communicate with their nearby network elements so they can learn network constraints. Optionally, with QUIC server support their incoming QUIC packets can be mapped to metadata about their contents so packet importance can influence both intentional and reactive management policies. The framework handles both directions of a flow. This document specifies the format and mechanism that is to be used for encoding Access-Network Identifiers in DHCPv4 and DHCPv6 messages by defining new Access-Network-Identifier options and sub-options.

Acknowledgments Thanks to Dave Täht, Magnus Westerlund, Christian Huitema, Gorry Fairhurst, and Tom Herbert for hallway discussions and feedback at TSVWG that encouraged the authors to consider the approach described in this document. Thanks to Ben Schwartz for suggesting PvD as an alternative discovery mechanism.