Network Working Group D. Wing Internet-Draft Cloud Software Group Intended status: Standards Track T. Reddy Expires: 18 February 2024 Nokia M. Boucadair Orange 17 August 2023 CID Flow Indicator (CIDFI) draft-wing-cidfi-00 Abstract 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 This note is to be removed before publishing as an RFC. The latest revision of this draft can be found at https://danwing.github.io/cidfi/draft-wing-cidfi.html. Status information for this document may be found at https://datatracker.ietf.org/doc/draft-wing-cidfi/. Discussion of this document takes place on the ART Area Working Group Working Group mailing list (mailto:art@ietf.org), which is archived at https://mailarchive.ietf.org/arch/browse/art/. Subscribe at https://www.ietf.org/mailman/listinfo/art/. Source for this draft and an issue tracker can be found at https://github.com/danwing/cidfi. Status of This Memo This Internet-Draft is submitted in full conformance with the provisions of BCP 78 and BCP 79. 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 https://datatracker.ietf.org/drafts/current/. Wing, et al. Expires 18 February 2024 [Page 1] Internet-Draft CIDFI August 2023 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 18 February 2024. Copyright Notice Copyright (c) 2023 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 (https://trustee.ietf.org/ 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 . . . . . . . . . . . . . . . . . 5 3. Design Goals . . . . . . . . . . . . . . . . . . . . . . . . 5 4. Network Preparation: DNS SVCB Records . . . . . . . . . . . . 6 5. Client Operation on Network Attach or Topology Change . . . . 6 5.1. Client Learns Local Network Supports CIDFI . . . . . . . 6 5.2. Client Authorizes CIDFI Network Elements . . . . . . . . 7 6. Client Operation on Each Connection to a QUIC Server . . . . 7 6.1. Client Learns Server Supports CIDFI . . . . . . . . . . . 8 6.2. Client Proves Ownership of its UDP 4-Tuple . . . . . . . 8 6.2.1. STUN CIDFI-NONCE Attribute . . . . . . . . . . . . . 9 6.3. Initial Metadata Exchange . . . . . . . . . . . . . . . . 10 6.3.1. Server to Network Elements . . . . . . . . . . . . . 12 6.3.2. Network Element to Server . . . . . . . . . . . . . . 12 6.4. Ongoing Metadata Exchange . . . . . . . . . . . . . . . . 13 7. Interaction with Load Balancers . . . . . . . . . . . . . . . 13 8. Topology Change . . . . . . . . . . . . . . . . . . . . . . . 14 9. Details of Metadata Exchanged . . . . . . . . . . . . . . . . 14 9.1. Server to CIDFI-aware Network Element . . . . . . . . . . 14 9.1.1. Mapping Metadata Parameters to DCIDs . . . . . . . . 14 9.1.2. Mapping DiffServ Code Point (DSCP) to DCIDs . . . . . 15 9.2. CIDFI-aware Network Element to Server . . . . . . . . . . 16 10. Discussion Points . . . . . . . . . . . . . . . . . . . . . . 16 10.1. Client versus Server Signaling CID-to-importance Mapping . . . . . . . . . . . . . . . . . . . . . . . . 16 Wing, et al. Expires 18 February 2024 [Page 2] Internet-Draft CIDFI August 2023 10.2. Overhead of QUIC DCID Packet Examination . . . . . . . . 16 10.3. Interaction with Wi-Fi Packet Aggregation . . . . . . . 16 10.4. Overhead of Mapping CID to packet metadata . . . . . . . 16 10.5. Improve CIDFI Initialization time . . . . . . . . . . . 17 10.6. Primary QUIC Channel CID Change {#primary-cid-change}: . . . . . . . . . . . . . . . . . 17 11. Security Considerations . . . . . . . . . . . . . . . . . . . 17 12. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 18 12.1. New QUIC Transport Parameter . . . . . . . . . . . . . . 18 12.2. New Well-known URI "cidfi-aware" . . . . . . . . . . . . 18 12.3. New Special-use Domain Name . . . . . . . . . . . . . . 18 12.4. New DNS Service Binding (SVCB) . . . . . . . . . . . . . 18 12.5. New STUN Attribute . . . . . . . . . . . . . . . . . . . 18 13. References . . . . . . . . . . . . . . . . . . . . . . . . . 19 13.1. Normative References . . . . . . . . . . . . . . . . . . 19 13.2. Informative References . . . . . . . . . . . . . . . . . 20 Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . . 22 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 22 1. Introduction Senders rely on ramping up their transmission rate until they encounter packet loss or see [ECN] 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 [QUIC] connection or a DTLS connection [DTLS-CID] 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. Wing, et al. Expires 18 February 2024 [Page 3] Internet-Draft CIDFI August 2023 Figure 1 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 Newwork (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. | | | +------+ +------+ | +------+ | | |CIDFI-| |CIDFI-| | |CIDFI-| | | |aware | |aware | | |aware | +------+ | | |client|-+-B-+Wi-Fi +-B-+edge +--+router+------+ | +------+ |access| | |router| +------+ | | | +--------+ |point | | +------+ | | | | CIDFI- | +------+ | | +-+----+ | | aware | | | |router+---+ QUIC or| +---------+ | +------+ | +-+----+ | | DTLS | | CIDFI- | | |CIDFI-| | | | | server | | aware | | |aware | +------+ | | | +--------+ | client +-----B-----+RAN +--+router+------+ | |(handset)| | |router| +------+ | | +---------+ | +------+ | | | | | | | transit | server user network | ISP network | network | network Figure 1: 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. In Section 6.3.2 this document describes network-to-server signaling similar to the use-case described in Section 2 of [I-D.joras-sadcdn], with metadata relaying through the client. Wing, et al. Expires 18 February 2024 [Page 4] Internet-Draft CIDFI August 2023 In Section 6.3.1 this document describes server-to-network metadata signaling similar to the use-cases described in Section 3 of [I-D.joras-sadcdn]. The server-to-network metadata signaling can also benefit [I-D.ietf-avtcore-rtp-over-quic] and [DTLS-CID]. 2. 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 [RFC2119] [RFC8174] when, and only when, they appear in all capitals, as shown here. CID: Connection Identifier used by [QUIC] or by [DTLS-CID]. CNE: CIDFI-aware Network Element, a network element that supports this CIDFI specification. This is usually a router. 3. 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 flow or each 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 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 are protected by TLS. Internet Survival: The QUIC communications and DTLS communications between the client and server are not changed so CIDFI is expected to work wherever QUIC (or DTLS) work. The elements involved are only the QUIC (or DTLS) client and server and with the participating CIDFI network elements. Wing, et al. Expires 18 February 2024 [Page 5] Internet-Draft CIDFI August 2023 4. Network Preparation: DNS SVCB Records This document defines a new DNS Service Binding "cidfi-aware" in Section 12.4 and a new Special-Use Domain Name "cifi.arpa" in Section 12.3. The local network is configured to respond to DNS SVCB [I-D.ietf-dnsop-svcb-https] queries with ServiceMode (Section 2.4.3 of [I-D.ietf-dnsop-svcb-https]) 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 CNE on the local network, one belonging to the local ISP (exmaple.net) and the other belonging to the local Wi-Fi network (example.com), _cidfi-aware.cidfi.arpa. 7200 IN SVCB 0 service-cidfi.example.net. ( alpn=h3 cidfipathauth=/path-auth-query {?cidfi} cidfimetadata=/cidfi-metadata ) _cidfi-aware.cidfi.arpa. 7200 IN SVCB 0 wifi.example.com. ( alpn=h3 cidfipathauth=/path-auth-query {?cidfi} cidfimetadata=/cidfi-metadata ) When multihoming, the multihome-capable CPE aggregates all upstream networks' _cidfi-aware.cidfi.arpa responses into the response sent to its locally-connected clients. 5. Client Operation on Network Attach or Topology Change On initial network attach topology change (see Section 8), the client learns if the network supports CIDFI (Section 5.1) and authorizes those network elements (Section 5.2). 5.1. Client Learns Local Network Supports CIDFI 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) [I-D.ietf-dnsop-svcb-https]. If this succeeds, processing skips to Section 5.2. If discovery failed it indicates the local network does not support CIDFI and processing stops. Wing, et al. Expires 18 February 2024 [Page 6] Internet-Draft CIDFI August 2023 5.2. Client Authorizes CIDFI Network Elements The SVCB response from the previous step in Section 5.1 will contain one or more CNE. The client authorizes each of the CNE using its local policy. This policy is implementation specific. An example implementation might have the user authorize their ISP's CIDFI server (e.g., allow cidfi.example.net if the user's ISP is configured as example.net). Similarly, if none of the CNE are recognized the client might silently avoid using CIDFI on that network. After authorizing that subset of CNE, the client makes a new HTTPS connection to each of those CNE 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 Section 6.2 to prove the client owns its UDP 4-tuple. For discussion purposes, JSON is shown below to give a flavor of the data the client retrieves from the CIDFI network element. The authors anticipate using a more efficient encoding such as [CBOR]. {"cidfi-path-authentication":[ {"nonce":"ddqwohxGZysgy0BySNh7sNHV5IH9RbE7rqXmg9wb9Npo", "hmac-secret":"jLNsCvuU59mt3F4/ePD9jbZ932TfsLSOP2Nx3XnUqc8v"}]} 6. 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. Wing, et al. Expires 18 February 2024 [Page 7] Internet-Draft CIDFI August 2023 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. 6.1. Client Learns Server Supports CIDFI On initial connection to a QUIC server, the client includes a new QUIC transport parameter CIDFI (Section 12.1) 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 Section 6.3. 6.2. Client Proves Ownership of its UDP 4-Tuple To ensure 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 Section 5.2 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 [STUN] indication (STUN class of 0b01) containing one or more CIDFI- NONCE attributes (Section 12.5). 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: Wing, et al. Expires 18 February 2024 [Page 8] Internet-Draft CIDFI August 2023 QUIC CIDFI-aware QUIC client edge router server | | | | HTTPS: Enroll CIDFI router to partipate | +----------------------------------->| | | 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 set-up 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 (Section 9 of [QUIC]) 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 (Section 5). 6.2.1. STUN CIDFI-NONCE Attribute The format of the STUN CIDFI-NONCE attribute is: Wing, et al. Expires 18 February 2024 [Page 9] Internet-Draft CIDFI August 2023 0 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | | | Nonce (128 bits) | | | | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | | | | | | | HMAC-output (256 bits) | | | | | | | | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Figure 2: Format of CIDFI-NONCE Attribute The nonce is 128 bits obtained from the CIDFI network element. The HMAC-output field is computed per [RFC5869] 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. HMAC-output = HMAC-SHA256( hmac-secret, nonce | "cidfi" ) 6.3. 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 (Section 9 of [QUIC]). 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 (Section 9.5 of [QUIC]). Thus, an additional Connection ID is purposefully not communicated from the Wing, et al. Expires 18 February 2024 [Page 10] Internet-Draft CIDFI August 2023 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 ([NAPT], [NAT]), 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. CIDFI-aware QUIC client edge router server | | | | HTTPS: Enroll CIDFI router to partipate | +----------------------------------->| | | 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 | | |<-----------------------------------+ | Wing, et al. Expires 18 February 2024 [Page 11] Internet-Draft CIDFI August 2023 Figure 3: Client re-transmtting lost nonce There are two types of metadata exchanged, described in the following sub-sections. 6.3.1. 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. CIDFI-aware CIDFI-aware client Wi-Fi Access Point edge router server | | | | | QUIC CIDFI stream: "Map DCID=xyz as high importance" | |<------------------------------------------------------+ | "Map DCID=xyz as | | | high importance"| | | +----------------->| | | | "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}). 6.3.2. Network Element to Server The network element send network performance information to the server which is intended to influence the sender'ss 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. Wing, et al. Expires 18 February 2024 [Page 12] Internet-Draft CIDFI August 2023 CIDFI-aware CIDFI-aware client Wi-Fi Access Point edge router server | | | | | "bandwidth now 1Mbps" | | |<-----------------------------------+ | | QUIC CIDFI stream: "bandwidth now 1Mbps" | +------------------------------------------------>| | QUIC CIDFI stream: Ok | | |<------------------------------------------------+ | Ok | | | +----------------------------------->| | The communication from the client to the server are 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 Section 9. 6.4. Ongoing Metadata Exchange For the duration of the primary QUIC connection between the QUIC client and QUIC server, the client relays network element metadata changes to the server, and server's transmitted QUIC Destination CID to the network elements. 7. Interaction with Load Balancers HTTPS servers, including QUIC servers, are frequently behind load balancers. With CIDFI, all the communication to the load-balanaced 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. Wing, et al. Expires 18 February 2024 [Page 13] Internet-Draft CIDFI August 2023 8. Topology Change When 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 (Section 9 of [QUIC]). 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 Section 5.1. If that set of network elements differs from the previous set, the client SHOULD continue with normal CIDFI processing. todo: include discussion of [DTLS-CID] client and discussion of its ICE interaction, if any? 9. Details of Metadata Exchanged This section describes the metadata that can be exchanged from the CNE to the server (generally network performance information) and from the server to the CNE. 9.1. Server to CIDFI-aware Network Element Because there is no direct communications from the server to the network element the communications are relayed through the client. The communication from server to network element do not occur directly, but rather through the client. Two types of mapping metadata are described below: metadata parameters and DSCP code points. 9.1.1. Mapping Metadata Parameters to DCIDs Several of metadata parameters can be mapped to Destination CID: 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 Wing, et al. Expires 18 February 2024 [Page 14] Internet-Draft CIDFI August 2023 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. For discussion purposes, JSON is shown below to give a flavor of the data exchanged. The authors anticipate a more efficient encoding such as [CBOR]. {"metadata-parameters":[{"quicversion":1, "dcidlength":3, "map":[ {"import":17,"burst":83,"delaybudget":71,"dcids":[551,381]}, {"import":3,"burst":888,"delaybudget":180,"dcids":[89,983]}, {"import":7,"burst":37,"delaybudget":55,"dcids":[33]}]}]} 9.1.2. Mapping DiffServ Code Point (DSCP) to DCIDs A mapping from Destination CID to DiffServ code point [RFC2474] leverages existing DiffServ handling that may already exist in the CIDFI network element. If there are downstream network elements configured with the same DiffServ code point the CIDFI network element could mark the packet with that code point as well. Signaling the DiffServ values for different QUIC Destination CID increases the edge network's confidence 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., [pathologies]). Over the CIDFI-dedicated QUIC stream, the server sends mapping information to the client when then propagates that information to each of the CNEs. For discussion purposes, JSON is shown below to give a flavor of the data exchanged. The authors anticipate using a more efficient encoding such as [CBOR]. {"dscp":[{"quicversion":1, "dcidlength":3, "map":[ {"dscp":10,"dcids":[123,456]}, {"dscp":46,"dcids":[998,183]}]}]} Figure 4: Example JSON for DSCP Mapping Wing, et al. Expires 18 February 2024 [Page 15] Internet-Draft CIDFI August 2023 9.2. 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. For discussion purposes, JSON is shown below to give a flavor of the data sent from the CNE to the client. The authors anticipate using a more efficient encoding such as [CBOR]. {"dcid":123, "bandwidth":"1Mbps"} The client then sends that information to the server in the CIDFI- dedicated QUIC stream associated with that same Connection ID. 10. Discussion Points This section discusses known issues that would benefit from wider discussion. 10.1. 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. 10.2. Overhead of QUIC DCID Packet Examination If CID-to-importance metadata was signaled by the server as described in Section 6.3.1, 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. 10.3. 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., [wifi-aggregation]) and similar 5G optimizations. This impact needs further study. 10.4. Overhead of Mapping CID 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. Wing, et al. Expires 18 February 2024 [Page 16] Internet-Draft CIDFI August 2023 An alternative is a fixed mapping of QUIC CIDs to their meanings, as proposed in [I-D.zmlk-quic-te]. However, this will ossify the meaning of those QUIC CIDs. It also requires all networks to agree on the meaning of those QUIC CIDs. 10.5. Improve CIDFI Initialization time Find approaches to further reduce network communications to start CIDFI. 10.6. 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 Section 9.5 of [QUIC]}. 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? 11. 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 ([RFC2827], [RFC7513], [RFC6105], and/or [RFC6620]). In the event network Wing, et al. Expires 18 February 2024 [Page 17] Internet-Draft CIDFI August 2023 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. 12. IANA Considerations 12.1. 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 [IANA-QUIC]: +=======+================+===============+ | Value | Parameter Name | Reference | +=======+================+===============+ | TBD1 | CIDFI | This-Document | +-------+----------------+---------------+ Table 1: New QUIC Transport Parameter 12.2. 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 [IANA-WKU]. 12.3. New Special-use Domain Name Register new special-use domain name cidfi.arpa for DNS SVCB discovery. 12.4. 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 [IANA-SVCB]. 12.5. New STUN Attribute This document requests IANA to register the new STUN attribute "CIDFI-NONCE" in the "STUN Attributes" registry available at [IANA-STUN]. Wing, et al. Expires 18 February 2024 [Page 18] Internet-Draft CIDFI August 2023 13. References 13.1. Normative References [CBOR] Bormann, C. and P. Hoffman, "Concise Binary Object Representation (CBOR)", STD 94, RFC 8949, DOI 10.17487/RFC8949, December 2020, . [DTLS-CID] Rescorla, E., Ed., Tschofenig, H., Ed., Fossati, T., and A. Kraus, "Connection Identifier for DTLS 1.2", RFC 9146, DOI 10.17487/RFC9146, March 2022, . [I-D.ietf-dnsop-svcb-https] Schwartz, B. M., Bishop, M., and E. Nygren, "Service binding and parameter specification via the DNS (DNS SVCB and HTTPS RRs)", Work in Progress, Internet-Draft, draft- ietf-dnsop-svcb-https-12, 11 March 2023, . [QUIC] Iyengar, J., Ed. and M. Thomson, Ed., "QUIC: A UDP-Based Multiplexed and Secure Transport", RFC 9000, DOI 10.17487/RFC9000, May 2021, . [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/RFC2119, March 1997, . [RFC2474] Nichols, K., Blake, S., Baker, F., and D. Black, "Definition of the Differentiated Services Field (DS Field) in the IPv4 and IPv6 Headers", RFC 2474, DOI 10.17487/RFC2474, December 1998, . [RFC5869] Krawczyk, H. and P. Eronen, "HMAC-based Extract-and-Expand Key Derivation Function (HKDF)", RFC 5869, DOI 10.17487/RFC5869, May 2010, . [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, May 2017, . Wing, et al. Expires 18 February 2024 [Page 19] Internet-Draft CIDFI August 2023 [STUN] Rosenberg, J., Mahy, R., Matthews, P., and D. Wing, "Session Traversal Utilities for NAT (STUN)", RFC 5389, DOI 10.17487/RFC5389, October 2008, . 13.2. Informative References [ECN] Ramakrishnan, K., Floyd, S., and D. Black, "The Addition of Explicit Congestion Notification (ECN) to IP", RFC 3168, DOI 10.17487/RFC3168, September 2001, . [I-D.ietf-avtcore-rtp-over-quic] Ott, J., Engelbart, M., and S. Dawkins, "RTP over QUIC (RoQ)", Work in Progress, Internet-Draft, draft-ietf- avtcore-rtp-over-quic-05, 26 July 2023, . [I-D.joras-sadcdn] Joras, M., "Securing Ancillary Data for Communicating with Devices in the Network", Work in Progress, Internet-Draft, draft-joras-sadcdn-01, 10 July 2023, . [I-D.zmlk-quic-te] Zheng, Z., Ma, Y., Liu, Y., and M. Kühlewind, "QUIC- enabled Service Differentiation for Traffic Engineering", Work in Progress, Internet-Draft, draft-zmlk-quic-te-00, 5 May 2023, . [IANA-QUIC] "QUIC", 26 July 2023, . [IANA-STUN] "STUN Attributes", 20 March 2023, . [IANA-SVCB] "DNS Service Bindings (SVCB)", 13 June 2023, . Wing, et al. Expires 18 February 2024 [Page 20] Internet-Draft CIDFI August 2023 [IANA-WKU] "Well-known URIs", 20 June 2023, . [NAPT] Srisuresh, P. and K. Egevang, "Traditional IP Network Address Translator (Traditional NAT)", RFC 3022, DOI 10.17487/RFC3022, January 2001, . [NAT] Srisuresh, P. and M. Holdrege, "IP Network Address Translator (NAT) Terminology and Considerations", RFC 2663, DOI 10.17487/RFC2663, August 1999, . [pathologies] Custura, A., Secchi, R., and G. Fairhurst, "Exploring DSCP modification pathologies in the Internet", May 2018, . [RFC2827] Ferguson, P. and D. Senie, "Network Ingress Filtering: Defeating Denial of Service Attacks which employ IP Source Address Spoofing", BCP 38, RFC 2827, DOI 10.17487/RFC2827, May 2000, . [RFC6105] Levy-Abegnoli, E., Van de Velde, G., Popoviciu, C., and J. Mohacsi, "IPv6 Router Advertisement Guard", RFC 6105, DOI 10.17487/RFC6105, February 2011, . [RFC6620] Nordmark, E., Bagnulo, M., and E. Levy-Abegnoli, "FCFS SAVI: First-Come, First-Served Source Address Validation Improvement for Locally Assigned IPv6 Addresses", RFC 6620, DOI 10.17487/RFC6620, May 2012, . [RFC7513] Bi, J., Wu, J., Yao, G., and F. Baker, "Source Address Validation Improvement (SAVI) Solution for DHCP", RFC 7513, DOI 10.17487/RFC7513, May 2015, . [wifi-aggregation] Høiland-Jørgensen, T., Kazior, M., Täht, D., Hurtig, P., and A. Brunstrom, "Ending the Anomaly: Achieving Low Latency and Airtime Fairness in WiFi", 22 May 2017, . Wing, et al. Expires 18 February 2024 [Page 21] Internet-Draft CIDFI August 2023 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. Authors' Addresses Dan Wing Cloud Software Group, Inc. United States of America Email: danwing@gmail.com Tirumaleswar Reddy Nokia Bangalore Karnataka India Email: kondtir@gmail.com Mohamed Boucadair Orange Rennes 35000 France Email: mohamed.boucadair@orange.com Wing, et al. Expires 18 February 2024 [Page 22]