]> Cloud Software Group, Inc.

United States of America danwing@gmail.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 Conveying metadata about network conditions and metadata about individual packets can improve the user experience especially on wireless networks which suffer bandwidth and delay variability. This document describes how clients and servers can cooperate with network elements so their QUIC and DTLS streams can be augmented with information about network conditions and packet importance. 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 ART 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). Due to network constraints a network element will need to drop or even prioritize a packet ahead of other packets. The decision of which packet to drop or prioritize is improved if the network element knows the importance of the packet. Metadata carried in each packet can influence that decision to improve the user experience. This document defines CIDFI (pronounced "sid fye") which is a system of several protocols that allow communicating about a connection or a DTLS connection from the network to the server and the server to the network. The information exchanged allows the server to know about network conditions and allows the server to signal packet importance. provides a sample network diagram of a CIDFI system showing two bandwidth-constrained networks (or links) depicted by "B" and CIDFI-aware devices immediately upstream of those links, and another bandwidth-constrained link between a smartphone handset and its Radio Access Network (RAN). This diagram shows the same protocol and same mechanism can operate with or without 5G, and can operate with different administrative domains such as Wi-Fi, an ISP edge router, and a 5G RAN.

Network Diagram

The CIDFI-aware client establishes a TLS connection with the CIDFI-aware network elements (Wi-Fi access point, edge router, and RAN router in the above diagram). Over this connection it receives network performance information and it sends mapping of (QUIC or DTLS) Destination CIDs to packet importance. The design creates new state in the CIDFI-aware network elements for mapping from the QUIC Destination CID or DTLS Destination CID to the packet importance, bandwidth information for that connection towards the client, and for the TLS-encrypted communication with the client. describes network-to-server signaling similar to the use case described in , with metadata relaying through the client. describes server-to-network metadata signaling similar to the use cases described in . The server-to-network metadata signaling can also benefit and . A discussion of extending CIDFI to other protocols is provided in .

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.

CID:

Connection Identifier used by or by .

CNE:

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

Notations For discussion purposes, JSON is used in the examples to give a flavor of the data that the client retrieves from a CNE. The authors anticipate using a more efficient encoding such as .

Design Goals This section highlights the design goals of this specification.

Client Authorization:

The client authorizes each CIDFI-aware network element (CNE) to participate in CIDFI for each QUIC or DTLS flow.

Same Server:

Communication about the network metadata arrives over the primary QUIC or DTLS connection which ensures it arrives at the same server instance even through local network translators (NAT) or server-side load balancers.

Privacy:

The packet importance is only known by CIDFI-aware network elements (CNE). The network performance data is protected by TLS.

Integrity:

The packet importance is mapped to Destination CIDs which are integrity protected by QUIC (or DTLS) itself and cannot be modified by on-path network elements. The communication between client, server, and network element is protected by TLS.

Internet Survival:

The QUIC (or DTLS) communications between the client and server are not changed so CIDFI is expected to work wherever QUIC (or DTLS) works. The elements involved are only the QUIC (or DTLS) client and server and with the participating CIDFI network elements.

Network Preparation 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 below.

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

DNS SVCB Records This document defines a new DNS Service Binding "cidfi-aware" in and a new Special-Use Domain Name "cifi.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), 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 this when there are two CIDFI-aware network elements, service-cidfi and wi-fi, 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 Operation on Network Attach or Topology Change On initial network attach topology change (see ), the client learns if the network supports CIDFI () and authorizes those network elements ().

Client Learns Local Network Supports CIDFI For this step, four mechanisms are identified: DNS SVCB records, IPv6 Provisioning Domains (PvD), DHCP, or 3GPP PCO. These are described below.

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

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 Network Elements The response from the previous step in will contain one or more CNEs. 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. After authorizing that subset of CNEs, the client makes a new HTTPS connection to each of those CNEs and performs PKIX validation of their certificates. The client MAY have to authenticate itself to the CIDFI network element. The client then obtains the CIDFI nonce and CIDFI HMAC secret from each network element used later in to prove the client owns its UDP 4-tuple.

Client Operation on Each Connection to a QUIC Server When a QUIC client (or {DTLS-CID}) client connects to a QUIC (or {DTLS-CID}) server, the client:

1. learns the server supports CIDFI and obtains its mapping of transmitted destinations CID to metadata.
2. proves ownership of its UDP 4-tuple to the on-path network elements.
3. performs initial metadata exchange with the CIDFI network element and server, and server and network element.
4. continually updates the server and the CIDFI network element whenever new information is received from the other party.

These steps are described in more detail below.

• Note: the client is also a sender, and can also perform all these functions in its direction. This functionality will be expanded in later versions of this document. For example, a mobile device connected to Wi-Fi with 5G backhaul might be running an interactive audio/video application and want to indicate to its internal Wi-Fi driver and to the 5G modem its mapping from its transmitted QUIC Destination CID to per-packet metadata and the application can benefit from receiving network performance metrics.

Client Learns Server Supports CIDFI On initial connection to a QUIC server, the client includes a new QUIC transport parameter CIDFI () which is remembered for 0-RTT. If the server does not indicate CIDFI support, CIDFI processing stops. If the server indicates CIDFI support, then the server creates a new Server-Initiated, Bidirectional QUIC stream which is dedicated to CIDFI communication. This stream number is communicated in the CIDFI transport response during the QUIC handshake. TODO: specify how CIDFI stream number is communicated to client. The QUIC client and QUIC server exchange CIDFI information over this CIDFI-dedicated stream as described in .

Client Proves Ownership of its UDP 4-Tuple To ensure that the client messages to the CNE pertain only to the client's own UDP 4-tuple, the client sends the CIDFI nonce protected by the HMAC secret it obtained from over the QUIC UDP 4-tuple it is using with the QUIC server. The ability to transmit that packet on the same UDP 4-tuple as the QUIC connection indicates ownership of that IP address and UDP port. The nonce and HMAC are sent in a indication (STUN class of 0b01) containing one or more CIDFI-NONCE attributes (). If there are multiple CNE the single STUN indication contains a CIDFI-NONCE attribute from each of them. This message is discarded by the QUIC server. The figure below shows a summarized message flow obtaining the nonce and HMAC secret from the CNE then later sending the nonce and HMAC in the same UDP 4-tuple towards the QUIC server: | | | HTTPS: Ok. nonce=12345 | | |<-----------------------------------+ | | | | : : : | | | | QUIC Initial, transport parameter=CIDFI | +------------------------------------------------------>| | STUN Indication, nonce=12345, hmac=e8FEc | +------------------------------------------------------>| | | discarded | | | | "I saw my nonce, HMAC is valid" | | | | | HTTPS: "Map DCID=xyz as high importance" | +----------------------------------->| | | QUIC Initial, transport parameter=CIDFI | |<------------------------------------------------------+ | HTTPS: Ok | | |<-----------------------------------+ | ]]> Because multiple QUIC clients will use the same incoming Destination CID on their own UDP 4-tuple, the STUN Indication message also allows the CIDFI network element to distinguish which UDP 4-tuple belongs to each CIDFI client. To reduce CIDFI setup time the client STUN Indication MAY be sent at the same time as the QUIC Initial packet, which is encouraged if the client remembers the server supports CIDFI (0-RTT). To prevent replay attacks, the Nonce is usable only for authenticating one UDP 4-tuple. When the connection is migrated () the CIDFI network element won't apply any CIDFI behavior to that newly-migrated connection. The client will have to restart CIDFI procedures at the beginning ().

STUN CIDFI-NONCE Attribute The format of the STUN CIDFI-NONCE attribute is:

Format of CIDFI-NONCE Attribute

The nonce is 128 bits obtained from the CIDFI network element. The HMAC-output field is computed per using the CIDFI network element-provided HMAC secret, and the CIDFI network element-provided Nonce concatenated with the fixed string "cidfi" (without quotes), shown below with "|" denoting concatenation.

Initial Metadata Exchange Using its HTTPS channel with each of the CIDFI network elements it previously authorized for CIDFI participation, the client signals the mapping of the server's transmitted short Destination Connection ID and its length to the CNE. As server support of the QUIC CIDFI transport parameter is remembered for 0-RTT, the client can immediately send the nonce. The primary purpose of a second Connection ID is connection migration (). With CIDFI, additional Connection IDs are necessary to: * maintain CIDFI operation when topology remains the same. * use Destination Connection ID to indicate packet importance To maintain CIDFI operation when topology remains the same, the CIDFI client signals the CNEs of that 'next' Destination CID. When QUIC detects a topology change, however, that Destination CID MUST NOT be used by the peer, otherwise it links the communication on the old topology to the new topology (). Thus, an additional Connection ID is purposefully not communicated from the CIDFI client to its CNEs, so that Connection ID can be immediately used by the peer during connection migration when the topology changes. Note the source IP address and source UDP port number are not signaled by design. This is because NATs (, ), multiple NATs on the path, IPv6/IPv4 translation, similar technologies, and QUIC connection migration all complicate accurate signaling of the source IP address and source UDP port number. If the CNE receives the HTTPS map request but has not yet seen the STUN nonce message it rejects the mapping request with a 403 and provides a new nonce. The new nonce avoids the problem of an attacker seeing the previous nonce and using that nonce on its own UDP 4-tuple. The client then sends a new STUN message with that new nonce value and send a new HTTPS mapping request(s). This interaction is highlighted in the simplified message flow, below.

Client re-transmitting lost nonce | | | HTTPS: Ok. nonce=12345 | | |<-----------------------------------+ | | | | : : : | | | | QUIC Initial, transport parameter=CIDFI | +------------------------------------------------------>| | STUN Indication, nonce=12345, HMAC=8f93e | +--------------------> X (lost) | | | | | | HTTPS: "Map DCID=xyz as high importance" | +----------------------------------->| | | HTTPS: 403, new Nonce=5678 | | |<-----------------------------------| | | STUN Indicate, nonce=5678, HMAC=aaf3c | +------------------------------------------------------>| | | discarded | | | | "I saw my nonce, HMAC is valid" | | | | | HTTPS: "Map DCID=xyz as high importance" | +----------------------------------->| | | Ok | | |<-----------------------------------+ | ]]>

There are two types of metadata exchanged, described in the following sub-sections.

Server to Network Elements The server communicates to network elements via the client which then communicates with the network element(s). While this adds communication delay, it allows the user at the client to authorize the metadata communication about its own incoming (and outgoing) traffic. The communication from the client to the server are using a CIDFI-dedicated QUIC stream over the same QUIC connection as their primary communication. | | | | "Map DCID=xyz as high importance" | | +----------------------------------->| | | Ok | | | |<-----------------+ | | | Ok | | | |<-----------------------------------+ | | QUIC CIDFI stream: Ok | | +------------------------------------------------------>| ]]> To each of the network elements authorized by the client, the client sends the mappings of the server's transmitted Destination CIDs to packet metadata (see {#packet-metadata}).

Network Element to Server The network element sends network performance information to the server which is intended to influence the sender's traffic rate (such as improving or reducing fidelity of the audio or video). In the figure below the CNE informs the client of reduced bandwidth and the client informs the server using CIDFI. | | QUIC CIDFI stream: Ok | | |<------------------------------------------------+ | Ok | | | +----------------------------------->| | ]]> The communication from the client to the server is using a CIDFI-dedicated QUIC stream over the same QUIC connection as their primary communication. The CNE can update the client with whenever the metadata about the connection changes significantly, but MUST NOT update more frequently than once every second. The metadata exchanged over this channel is described in .

Ongoing Metadata Exchange For the duration of the primary QUIC connection between the client and server, the client relays network element metadata changes to the server, and server's transmitted QUIC Destination CID to the network elements.

Interaction with Load Balancers HTTPS servers, including QUIC servers, are frequently behind load balancers. With CIDFI, all the communications to the load-balanced QUIC server are over the same UDP 4-tuple as the primary QUIC connection but in a different QUIC stream. This means no changes are required to ECMP load balancers or to CID-aware load balancers when using a CIDFI-aware back-end QUIC server. Load balancers providing QUIC-to-TCP interworking is incompatible with CIDFI because TCP lacks QUIC's stream identification.

Topology Change When the topology changes the client will transmit from a new IP address -- such as switching to a backup WAN connection, or such as switching from Wi-Fi to 5G. If using QUIC, QUIC server will consider this a connection migration and will issue a PATH_CHALLENGE. If the client is aware of the topology change (such as attaching to a different network), the client would also change its QUIC Destination CID (). If the QUIC CIDFI-aware client is otherwise unaware of a topology change and receives a QUIC PATH_CHALLENGE then the CIDFI-aware client SHOULD re-discover its CIDFI network elements . If that set of network elements differs from the previous set, the client SHOULD continue with normal CIDFI processing.

• todo: include discussion of client and discussion of its ICE interaction, if any?

Details of Metadata Exchanged This section describes the metadata that can be exchanged from a CNE to a server (generally network performance information) and from the server to the CNE.

Server to CIDFI-aware Network Element Because there is no direct communication from the server to the network element the communication is relayed through the client. The communications from servers to network elements do not occur directly, but rather through the client. Two types of mapping metadata are described below: metadata parameters and DSCP values.

Mapping Metadata Parameters to DCIDs Several of metadata parameters can be mapped to Destination CIDs:

Importance:

Low/Medium/High importance, relative to other CIDs within this same UDP 4-tuple.

Delay budget:

Time in milliseconds until this packet is worthless to the receiver. This is counted from when the packet arrives at the CNE to when it is transmitted; other delays may occur before or after that event occurs. The receiver knows its own jitter (playout) buffer length and the client and server can calculate the one-way delay using timestamps. With that information, the client can adjust the server's signaled delay budget with the client's own knowledge. TODO: provide enough details to create interoperable implementations.

Over the CIDFI-dedicated QUIC stream, the server sends mapping information to the client when then propagates that information to each of the CNEs.

Mapping DiffServ Code Point (DSCP) to DCIDs A mapping from Destination CID to DiffServ code point leverages existing DiffServ handling that may already exist in the CIDFI network element. If there are downstream network elements configured with the same DSCP the CIDFI network element could mark the packet with that code point as well. Signaling the DSCP values for different QUIC Destination CIDs increases the edge network's confidence that the sender's DiffServ intent is preserved into the edge network, even if the DSCP bits were modified en route to the edge network (e.g., ). Over the CIDFI-dedicated QUIC stream, the server sends the mapping information to the client when then propagates that information to each of the CNEs.

Example JSON for DSCP Mapping

CIDFI-aware Network Element to Server The CIDFI-aware client informs the network element of the client's received Destination CIDs. As bandwidth availability to that client changes, the CNE updates the client with new metadata. The client then sends that information to the server in the CIDFI-dedicated QUIC stream associated with that same Connection ID.

Discussion Points This section discusses known issues that would benefit from wider discussion.

Client versus Server Signaling CID-to-importance Mapping Need to evaluate number of round trips (and other overhead) of client signaling CID-to-importance mapping or server signaling CID-to-importance mapping.

Overhead of QUIC DCID Packet Examination If CID-to-importance metadata was signaled by the server as described in , the CNE have to examine the UDP payload of each packet for a matching Destination CID for the lifetime of the connection. This is somewhat assuaged by the STUN nonce transmitted which may well be an easier signal to identify.

Interaction with Wi-Fi Packet Aggregation Per-packet metadata influences transmission of that packet but may well conflict with some Wi-Fi optimizations (e.g., ) and similar 5G optimizations. This impact needs further study.

Overhead of Mapping CIDs to Packet Metadata Network Elements have to maintain a mapping between each UDP 4-tuple and QUIC CID and its DSCP code point. This also needs updating whenever sender changes its CID. This is awkward. An alternative is a fixed mapping of QUIC CIDs to their meanings, as proposed in . However, this will ossify the meaning of those QUIC CIDs. It also requires all networks to agree on the meaning of those QUIC CIDs.

Improve CIDFI Initialization Time Find approaches to further reduce network communications to start CIDFI.

Primary QUIC Channel CID Change {#primary-cid-change}: Because the CIDFI network element, QUIC server, and QUIC client all cooperate to share the primary QUIC connection's Destination CID, when a new CIDFI network element is involved (e.g., due to client attaching to a different network), a new Destination CID SHOULD be used for the reasons discussed in }. We need clear way to signal which DCIDs can be used for 'this' network attach and which DCIDs are for a migrated connection. Probably belongs in the QUIC transport parameter signaling?

Security Considerations Because the sender's QUIC Destination Connection ID is mapped to packet importance, and the DCID remains the same for many packets, an attacker could determine which DCIDs are important by causing interference on the bandwidth-constrained link (by creating other legitimate traffic or creating radio interference) and observing which DCIDs are transmitted versus which DCIDs are dropped. This is a side- effect of using fixed identifier (DCIDs) rather than encrypting the packet importance. This was a design trade-off to reduce the CPU effort on the CNEs. A mitigation is using several DCIDs for every packet importance. Communications are relayed through the client because only the client and server knows the identity of the server and can validate its certificate. The protocol in this specification does not disclose the server's identity to the CIDFI network element. For an attacker to succeed with the nonce challenge against a victim's UDP 4-tuple the attacker has to send a STUN CIDFI-NONCE packet using the victim's source IP address and a valid HMAC. A valid HMAC can only be obtained by the attacker making its own connection to the CIDFI server and spoofing the source IP address and UDP port of the victim. Such spoofing of a victim's IP address is prevented by the network using network ingress filtering (, , , and/or ). In the event network ingress filtering is not configured or configured improperly, the CIDFI network element can detect an attack if the client implements CIDFI. The CIDFI network element receive two HTTPS connections describing the same DCID (one connection from the attacker, another from the victim). The CIDFI network element will issue unique Nonces and HMACs to both the attacker and victim, and the attacker and victim will both send the STUN indication on that same UDP 4-tuple. This should never normally occur and should generate an alarm on the CIDFI network element. In this situation, it is recommended both attack and victim be denied CIDFI access.

IANA Considerations

New QUIC Transport Parameter This document requests IANA to register the following new permanent QUIC transport parameter in the "QUIC Transport Parameters" registry under the "QUIC" registry group available at : New QUIC Transport Parameter

Value	Parameter Name	Reference
TBD1	CIDFI	This-Document

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 Register new 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 .

New STUN Attribute This document requests IANA to register the new STUN attribute "CIDFI-NONCE" in the "STUN Attributes" registry available at .

New Provisioning Domain Additional Information Key This document requests IANA to register two new JSON keys in the Provisioning Domains Additional Information registry at : Additionally, in the following cidfi keys are to be registered:

References Normative References This document defines the core of the QUIC transport protocol. QUIC provides applications with flow-controlled streams for structured communication, low-latency connection establishment, and network path migration. QUIC includes security measures that ensure confidentiality, integrity, and availability in a range of deployment circumstances. Accompanying documents describe the integration of TLS for key negotiation, loss detection, and an exemplary congestion control algorithm. This document specifies the Connection ID (CID) construct for the Datagram Transport Layer Security (DTLS) protocol version 1.2. A CID is an identifier carried in the record layer header that gives the recipient additional information for selecting the appropriate security association. In "classical" DTLS, selecting a security association of an incoming DTLS record is accomplished with the help of the 5-tuple. If the source IP address and/or source port changes during the lifetime of an ongoing DTLS session, then the receiver will be unable to locate the correct security context. The new ciphertext record format with the CID also provides content type encryption and record layer padding. This document updates RFC 6347. 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. The Concise Binary Object Representation (CBOR) is a data format whose design goals include the possibility of extremely small code size, fairly small message size, and extensibility without the need for version negotiation. These design goals make it different from earlier binary serializations such as ASN.1 and MessagePack. This document obsoletes RFC 7049, providing editorial improvements, new details, and errata fixes while keeping full compatibility with the interchange format of RFC 7049. It does not create a new version of the format. Google Akamai Technologies Akamai Technologies This document specifies the "SVCB" 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 [HTTP]. By providing more information to the client before it attempts to establish a connection, these records offer potential benefits to both performance and privacy. TO BE REMOVED: This document is being collaborated on in Github at: https://github.com/MikeBishop/dns-alt-svc (https://github.com/MikeBishop/dns-alt-svc). The most recent working version of the document, open issues, etc. should all be available there. The authors (gratefully) accept pull requests. 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. Session Traversal Utilities for NAT (STUN) is a protocol that serves as a tool for other protocols in dealing with NAT traversal. It can be used by an endpoint to determine the IP address and port allocated to it by a NAT. It can also be used to check connectivity between two endpoints and as a keep-alive protocol to maintain NAT bindings. STUN works with many existing NATs and does not require any special behavior from them. STUN is not a NAT traversal solution by itself. Rather, it is a tool to be used in the context of a NAT traversal solution. This document obsoletes RFC 5389. This document defines the IP header field, called the DS (for differentiated services) field. [STANDARDS-TRACK] 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] Meta Platforms, Inc. There is increasing need for application endpoints to exchange rich information with devices in the network and secure that information from on-path observers. This document presents some current problems and the broad strokes of potential solutions. Discussion Venues This note is to be removed before publishing as an RFC. Source for this draft and an issue tracker can be found at https://github.com/mjoras/sadcdn. Technical University Munich Technical University Munich Tencent America LLC This document specifies a minimal mapping for encapsulating Real-time Transport Protocol (RTP) and RTP Control Protocol (RTCP) packets within the QUIC protocol. This mapping is called RTP over QUIC (RoQ). It also discusses how to leverage state from the QUIC implementation in the endpoints, in order to reduce the need to exchange RTCP packets and how to implement congestion control and rate adaptation without relying on RTCP feedback. 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. This document specifies a simple Hashed Message Authentication Code (HMAC)-based key derivation function (HKDF), which can be used as a building block in various protocols and applications. The key derivation function (KDF) is intended to support a wide range of applications and requirements, and is conservative in its use of cryptographic hash functions. This document is not an Internet Standards Track specification; it is published for informational purposes. The NAT operation described in this document extends address translation introduced in RFC 1631 and includes a new type of network address and TCP/UDP port translation. In addition, this document corrects the Checksum adjustment algorithm published in RFC 1631 and attempts to discuss NAT operation and limitations in detail. This memo provides information for the Internet community. This document attempts to describe the operation of NAT devices and the associated considerations in general, and to define the terminology used to identify various flavors of NAT. This memo provides information for the Internet community. Alibaba Inc. Alibaba Inc. Alibaba Inc. Ericsson This document defines a method for supporting QUIC-enabled service differentiation for traffic engineering through multipath and QUIC connection identifier (CID) encoding. This approach enables end-host networking stacks and applications to select packet routing paths in a wide area network (WAN), potentially improving the end-to-end performance, cost, and reliability. The proposed method can be used in conjunction with segment routing traffic engineering technologies, such as SRv6 TE. This paper discusses a simple, effective, and straightforward method for using ingress traffic filtering to prohibit DoS (Denial of Service) attacks which use forged IP addresses to be propagated from 'behind' an Internet Service Provider's (ISP) aggregation point. This document specifies an Internet Best Current Practices for the Internet Community, and requests discussion and suggestions for improvements. This document specifies the procedure for creating a binding between a DHCPv4/DHCPv6-assigned IP address and a binding anchor on a Source Address Validation Improvement (SAVI) device. The bindings set up by this procedure are used to filter packets with forged source IP addresses. This mechanism complements BCP 38 (RFC 2827) ingress filtering, providing finer-grained source IP address validation. Routed protocols are often susceptible to spoof attacks. The canonical solution for IPv6 is Secure Neighbor Discovery (SEND), a solution that is non-trivial to deploy. This document proposes a light-weight alternative and complement to SEND based on filtering in the layer-2 network fabric, using a variety of filtering criteria, including, for example, SEND status. This document is not an Internet Standards Track specification; it is published for informational purposes. This memo describes First-Come, First-Served Source Address Validation Improvement (FCFS SAVI), a mechanism that provides source address validation for IPv6 networks using the FCFS principle. The proposed mechanism is intended to complement ingress filtering techniques to help detect and prevent source address spoofing. [STANDARDS-TRACK] 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 the Secure Real-time Transport Protocol (SRTP), a profile of the Real-time Transport Protocol (RTP), which can provide confidentiality, message authentication, and replay protection to the RTP traffic and to the control traffic for RTP, the Real-time Transport Control Protocol (RTCP). [STANDARDS-TRACK] While the Secure Real-time Transport Protocol (SRTP) provides confidentiality for the contents of a media packet, a significant amount of metadata is left unprotected, including RTP header extensions and contributing sources (CSRCs). However, this data can be moderately sensitive in many applications. While there have been previous attempts to protect this data, they have had limited deployment, due to complexity as well as technical limitations. This document updates RFC 3711, the SRTP specification, and defines Cryptex as a new mechanism that completely encrypts header extensions and CSRCs and uses simpler Session Description Protocol (SDP) signaling with the goal of facilitating deployment. Nederlandse Publieke Omroep Tencent America LLC This document describes use cases and requirements that guide the specification of a simple, low-latency media delivery solution for ingest and distribution, using either the QUIC protocol or WebTransport as transport protocols.

Extending CIDFI to Other Protocols CIDFI can be extended to other protocols including TCP, SCTP, RTP and SRTP, and bespoke UDP protocols. An extension to each protocol is described below which retains the ability of the client to prove its ownership of the 5-tuple to a CNE.

TCP To prove ownership of the TCP 4-tuple, TCP can utilize a new TCP option to carry the CNE's nonce and HMAC-output. This TCP option can be carried in both the TCP SYN and in some subsequent packets to avoid consuming the entire TCP option space (40 bytes). Sub-options can be defined to carry pieces of the Nonce and HMAC output, with the first piece of the Nonce in the TCP SYN so the CIDFI network element can be triggered to begin looking for the subsequent TCP frames containing the rest of the CIDFI nonce and CIDFI HMAC-output. For example,

1. send TCP SYN + CIDFI option (including Nonce bits 0-63)
2. if received TCP SYNACK does not indicate CIDFI support, stop sending CIDFI option
3. send next TCP packet + CIDFI option (including Nonce bytes 64-128)
4. send next TCP packet + CIDFI option (including HMAC-output bits 0-127)
5. send next TCP packet + CIDFI option (including HMAC-output bytes 128-256)

To shorten this further we might truncate the HMAC output and/or truncate the Nonce after security evaluation.

SCTP If SCTP is sent directly over IP, proof of ownership of the SCTP 4-tuple can be achieved using an extension to its INIT packets, similar to what is described above for TCP SYN. If SCTP is run over UDP, the same proof of ownership of the UDP 4-tuple as described in can be performed.

RTP and SRTP The RTP Synchronization Source (SSRC) is in the clear for , , and . If the SSRC is signaled similarly to CID, RTP could also benefit from CIDFI. CIDFI network elements could be told the mapping of SSRC values to importance and schedule those SSRCs accordingly. However, SSRC is used in playout (jitter) buffers and a new SSRC seen by a receiver will cause confusion. Thus, overloading SSRC to mean both 'packet importance' for CIDFI and 'synchronization source' will require engineering work on the RTP receiver to treat all the signaled SSRCs as one source for purposes of its playout buffer. RTP over QUIC is another approach which exposes QUIC headers to the network (which have CIDs) and does not overload the RTP SSRC. The Media over QUIC (MOQ) working group includes RTP over QUIC as one of its use cases .

Bespoke UDP Application Protocols To work with CIDFI, other UDP application protocols would have to prove ownership of their UDP 4-tuple () and extend their protocol to include a connection identifier in the first several bits of each of their UDP packets. Alternatively, rather than modifying the application protocol it could be run over or .

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.