Standard Communication with Network Elements (SCONE) Protocol

3.1. Independent of Congestion Signals

Throughput advice signals are not a substitute for congestion feedback or congestion control. Congestion signals, such as acknowledgments or ECN markings [ECN][WHY-ECN], provide information on loss and delay that indicate the real-time condition of a network path. Congestion signals might indicate a throughput limit that is different from the signaled throughput advice.¶

Endpoints cannot assume that the rate indicated in throughput advice is achievable if congestion signals indicate otherwise. Congestion could be experienced at a different point on the network path than the network element that signals throughput advice. Therefore, endpoints need to respect the send rate constraints that are set by a congestion controller.¶

Networks can use SCONE to communicate throughput advice for reasons other than rate limiting policies. For example, a network element in an access network could provide throughput advice to guide application use of network capacity, in any way that is separate from any signals that are intended to influence congestion response.¶

In addition to rate limiting policies, throughput advice can indicate temporary increases in available capacity or temporarily reduced capacity. This includes persistent overuse, equipment faults, or other transient issues. Providing advice is applicable if increases or reductions are expected to last for more than one monitoring period; see Section 5.2.¶

3.2. Unspecified Scope

Modifying a packet does not prove that the throughput that is indicated would be achievable. A signal that is sent for a specific flow is likely enforced at a different scope. The extent of that scope is not carried in the signal.¶

For instance, policy limits might apply at a network subscription level, such that multiple flows receive the same signal, but usage all contributes to a shared policy limit.¶

Endpoints can therefore be more confident in the throughput signal as an indication of the maximum achievable throughput than as any indication of expected throughput. In addition to endpoints respecting congestion signals (see Section 3.1), networks might need to monitor and enforce policies, even where applications attempt to follow advice (see Section 7.3).¶

The advised throughput will likely only be achievable when the application is the only user of throughput within the scope that the advice applies to. In the presence of other flows, congestion limits are likely to determine actual throughput.¶

This implies that signals can most usefully be applied to a downlink flow in access networks, close to an endpoint. In that case, capacity is less likely to be split between multiple active flows.¶

3.3. Per-Flow Signal

The same UDP address tuple might be used for multiple QUIC connections. A single signal might be lost or only reach a single application endpoint. Network elements can apply SCONE advice to all QUIC connections that include SCONE packets to ensure that advice is received by all application endpoints.¶

The signaled advice applies to the flow of packets on the same UDP address tuple for the duration of the current monitoring period, unless it is updated earlier or the flow ends; see Section 5.2 for details on the monitoring period.¶

Rate limiting policies often apply on the level of a device or subscription, but endpoints cannot assume that this is the case. A separate signal can be sent for each flow.¶

3.4. Undirectional Signal

Throughput advice is signaled with SCONE packets that are transmitted as part of the flow that the advice applies to. Carrying signals in the affected flow, in the same way that ECN signals are conveyed, ensures that there is no ambiguity about what flow is affected. However, this means that the endpoint that receives throughput advice is not the endpoint that might need to adapt its sending behavior.¶

A receiving endpoint might need to communicate the value it receives to the sending peer in order to ensure that the limit is respected. This document does not define how that signaling occurs as this is specific to the application in use.¶

3.5. Advisory Signal

Throughput advice indicates what one part of the network expects to be achievable for flows that transit that portion of the network. It is possible that very different throughput is achievable -- either higher or lower than the advice -- as determined by congestion control. Endpoints that receive this signal therefore need to treat the information as advisory.¶

The fact that an endpoint requests throughput advice does not necessarily mean that it will adhere to them; in some cases, the endpoint cannot. For example, a flow may initially be used to serve video chunks, with the client selecting appropriate chunks based on received advice, but later switch to a bulk download for which bitrate adaptation that cannot be similarly controlled. Composite flows from multiple applications, such as tunneled flows, might only have a subset of the involved applications that are capable of handling SCONE signals. Therefore, when a network element detects that throughput exceeds the advertised throughput advice, it might switch to applying its policies for non-SCONE flows, using congestion control signals.¶

Network conditions and rate-limit policies can change in ways that make previously signaled advice obsolete. For example, routing changes can cause a flow to move to a different network path. There are no guarantees that updated advice will be sent at such events.¶

3.6. Following Advice

The SCONE throughput advice is advisory (see Section 3.5). Applications that chose to follow it will do so in the way that best suits their needs.¶

The most obvious way to keep within the limits set by throughput advice is to inform the sending peer of the limit so that the peer can do whatever rate limiting is necessary. Alternatively, a receiver can control the release of flow control credit (see Section 4 of [QUIC]) to indirectly limit the sending rate of a peer.¶

Some applications offer options for rate control that can offer superior outcomes. Most video applications, especially real-time and streaming video applications, can adapt their use of network bandwidth. For instance, typical HTTP Live Streaming [HLS] or DASH [DASH] clients are provided with manifests that allow them to adjust the bitrate and quality of media segments based on available network capacity.¶

5.1. Rate Signals

A Rate Signal is a 7-bit unsigned integer (0-127). The high six bits are the Rate Signal High Bits, and the least significant bit is the most significant bit of the Version field.¶

When sent by a QUIC endpoint, the Rate Signal is set to 127. Receiving a value of 127 indicates that throughput advice is unknown, either because network elements on the path are not providing advice or they do not support SCONE. All other values (0 through 126) represent the ceiling of rates advised by the network element(s) on the path.¶

Throughput advice follows a logarithmic scale defined as:¶

• Base rate (b_min) = 100 Kbps¶

• Bitrate at value n = b_min * 10^(n/20)¶

where n is an integer between 0 and 126 represented by the Rate Signal.¶

Table 1 lists some of the potential values for signals and the corresponding bitrate for each.¶

5.2. Monitoring Period

The time over which throughput advice applies is defined to be a period of 67 seconds.¶

Protocol participants can use a different period, depending on their role. Senders can limit their send rate over any time period up to 67 seconds. Network elements can monitor and apply limits to send rates using time period of at least 67 seconds.¶

The choice of 67 seconds is a compromise between competing interests. Longer periods allow applications more flexibility in terms of how to allocate bandwidth over time. Shorter periods allow networks to administer policies more tightly. Also, when circumstances change, applications are better able recover without exceeding limits for a significant time if they have exceeded limits.¶

The choice of 67 seconds, as a prime number, also helps avoid synchronization with other periodic effects that are commonly measured in whole seconds. This includes segment length or key frame intervals in video applications, but also includes timers for middleboxes; see Section 4.3 of [RFC4787]. Any repeating phenomenon at a 67 second interval is therefore unlikely to be due to other periodic effects.¶

5.3. Endpoint Processing of SCONE Packets

Processing a SCONE packet involves reading the value from the Rate Signal field. However, this value MUST NOT be used unless another packet from the same datagram is successfully processed. Therefore, a SCONE packet always needs to be coalesced with other QUIC packets.¶

A SCONE packet is defined by the use of the long header bit (0x80 in the first byte) and the SCONE protocol version (0x6f7dc0fd or 0xef7dc0fd in the next four bytes). The 7-bit Rate Signal can be extracted by combining the low 6 bits of the first byte with the most significant bit of the version field. A SCONE packet MAY be discarded, along with any packets that come after it in the same datagram, if the Source Connection ID is not consistent with those coalesced packets, as specified in Section 5.¶

A SCONE packet is discarded if the rate signal is unknown (127).¶

A SCONE packet MUST be discarded if the Destination Connection ID does not match one recognized by the receiving endpoint.¶

If a connection uses multiple DSCP markings [RFC2474], the throughput advice that is received on datagrams with one marking might not apply to datagrams that have different markings.¶

5.4. Following Throughput Advice

Endpoints that receive throughput advice can advise their peer of the limit so that the peer might limit the amount of data it sends over any monitoring period (Section 5.2). Alternatively, the endpoint might change its own behavior to effect a similar outcome indirectly, which might use flow control or changes to request patterns.¶

An endpoint that receives throughput advice might receive multiple different values. If advice is applied by applications, applications MUST apply the lowest throughput advice received during any monitoring period; see Section 5.2.¶

After a monitoring period (Section 5.2) without receiving throughput advice, any previous advice expires. Endpoints can remove any constraints placed on throughput based on receiving throughput advice. This does not mean that there are no limits, either in policy or due to network conditions, only that these limits are now unknown. Other constraints on usage will still apply, which necessarily includes congestion control and might include other, application-specific constraints.¶

The relatively long duration of the monitoring period means that this is preferable to disabling sending completely. The cost is that loss of information about recent send rate might result in temporarily exceeding the rates indicated by throughput advice. In comparison, applications retain throughput usage state when throughput advice increases.¶

This approach ensures that network elements are able to reduce the frequency with which they send updated signals to as low as once per monitoring period. However, applying signals at a low frequency risks throughput advice being reset if no SCONE packet is available for applying signals (Section 7.1), or the rewritten packets are lost. Sending the signal multiple times increases the likelihood that the signal is received.¶

6.1. Indicating Support on New Flows

All new flows that are initiated by a client that supports SCONE MUST include bytes with values 0xc8 and 0x13 as the last two bytes of datagrams that commence a new flow if the protocol permits it. This indication MUST be sent in every datagram until the client receives any datagram from the server, at which point the client can be confident that the indication was received.¶

A client that uses a QUIC version that includes length-delimited packets, which includes QUIC versions 1 [QUIC] and 2 [QUICv2], can include an indicator of SCONE support at the end of datagrams that start a flow. The handshakes of these protocols ensures that the indication can be included in every datagram the client sends until it receives a response -- of any kind -- from the server.¶

6.2. Limitations of Indication

This indication does not mean that SCONE signals will be respected, only that the client is able to negotiate SCONE. A server might not support SCONE and either endpoint might choose not to send SCONE packets. Finally, applications might be unable to apply throughput advice or choose to ignore it.¶

This indication being just two bytes means that there is a non-negligible risk of collision with other protocols or even QUIC usage without SCONE indications. This means that the indication alone is not sufficient to indicate that a flow is QUIC with the potential for SCONE support.¶

Despite these limitations, having an indication might allow network elements to change their starting posture with respect to their enforcement of their rate limit policies.¶

6.3. Indications for Migrated Flows

Applications MAY decide to indicate support for SCONE on new flows, including when migrating to a new path (see Section 9 of [QUIC]). In QUIC version 1 and 2, the two byte indicator cannot be used.¶

Sending a SCONE packet for the first few packets on a new path gives network elements on that path the ability to recognize the flow as being able to receive throughput advice and also gives the network element an opportunity to provide that throughput advice.¶

To enable this indication, even if an endpoint would not otherwise send SCONE packets, endpoints can send a SCONE packet any time they send a QUIC PATH_CHALLENGE or PATH_RESPONSE frame. This applies to both client and server endpoints, but only if the peer has sent the transport parameter; see Section 6.¶

7.1. Applying Throughput Advice Signals

A network element detects a SCONE packet by observing that a packet has a QUIC long header and one of the SCONE protocol versions (0x6f7dc0fd or 0xef7dc0fd).¶

A network element then conditionally replaces the most significant bit of the Version field and the Rate Signal High Bits field with values of its choosing.¶

A network element might receive a packet that already includes a rate signal. The network element replaces the rate signal if it wishes to signal a lower value for throughput advice; otherwise, the original values are retained, preserving the signal from the network element with the lower policy.¶

The following pseudocode indicates how a network element might detect a SCONE packet and replace the existing rate signal (packet_signal) with a new rate signal (target_signal) that encodes the throughput advice of this network element.¶

is_long = packet[0] & 0x80 == 0x80
packet_version = ntohl(packet[1..5])
if is_long and (packet_version & 0x7fffffff) == SCONE_VERSION_BITS:
  packet_signal = ((packet[0] & 0x3f) << 1) | (packet_version >> 31)
  if target_signal < packet_signal:
    packet[0] = (packet[0] & 0xc0) | (target_signal >> 1)
    packet[1] = (packet[1] & 0x7f) | (target_signal << 7)

Once the throughput advice signal is updated, the network element updates the UDP checksum for the datagram.¶

To avoid throughput advice expiring, a network element needs to ensure that it sends updated rate signals with no more than a monitoring period (Section 5.2) between each update. Because this depends on the availability of SCONE packets and packet loss can cause signals to be missed, network elements might need to update more often. Ideally, network elements update advice in SCONE packets at least twice per monitoring period, to match endpoint behavior (see Section 8.1).¶

At the start of a flow, network elements are encouraged to update the rate signal of the first few SCONE packets it observes so that endpoints can obtain throughput advice early.¶

Senders that send a SCONE packet or network elements that update SCONE packets every 20–30 seconds is likely sufficient to ensure that throughput advice is not lost. To reduce the risk of synchronization across multiple senders, which may cause network elements to miss updates, senders can include a small random delay.¶

A network element MUST NOT alter datagrams to add SCONE packets or synthesize datagrams that contain SCONE packets. The latter will not be accepted and the former, even if they do not exceed the path MTU as a result, can be detected by applications and could be ignored. This document does not define a mechanism to support detection, but one might be added in future.¶

7.2. Monitoring Flows

Sending throughput advice is optional for any network. A network that sends throughput advice might, also optionally, choose to monitor flows to determine whether applications are following advice.¶

This section outlines a method that a network element could use to determine whether advice is being followed. Network deployments that choose to monitor are free to follow any monitoring regime that suits their needs.¶

This monitoring algorithm is guidance only. However, monitoring any more strictly than the following could mean that an application might be incorrectly classified as not following advice. A looser monitoring approach, such as monitoring over a longer time window than the monitoring period (67s) or using a higher rate than is signaled, has no risk of incorrect classification.¶

When a network changes the value it intends to signal, applications need time to adjust their sending behavior. As a result, any monitoring needs to allow time for SCONE packets to be updated, for those packets to be received by endpoints, and for applications to adapt.¶

A network element can then monitor affected flows to determine whether the throughput advice it provided was followed.¶

A network element SHOULD base its monitoring on the maximum value that was configured to apply during the preceding two monitoring periods. If the network element cannot update the throughput advice in every SCONE packet (or can do so only infrequently), a longer period might be used to account for the possibility that the updated SCONE packets are lost. This allows applications time to receive advice and adapt their sending rate.¶

Any monitoring and policy enforcement could be implemented in different network elements than the ones that signal throughput advice. However, network elements MUST NOT enforce throughput based on throughput advice found in SCONE packets received from other entities, because unlike endpoints, network elements do not have the capability to validate other QUIC packets contained in the same datagram; see Section 9.1.¶

7.3. Flows That Exceed Throughput Advice

A network could deploy policy enforcement that drops or delays packets to ensure that applications do not exceed throughput limits set in policy.¶

SCONE allows networks to provide advice to applications, so that stricter limits, which can be inefficient and lead to worse application performance, are not necessary in all cases.¶

Some applications will not support SCONE. Other applications either will not or cannot follow throughput advice.¶

Networks can monitor flows to determine if applications follow advice; see Section 7.2. A network could choose to either disable or loosen policy enforcement for flows where SCONE is active, but re-enable or tighten enforcement if monitoring indicates that throughput advice is not being respected.¶

8.1. Providing Opportunities to Apply Throughput Advice Signals

Endpoints that wish to offer network elements the option to add throughput advice signals can send SCONE packets at any time. This is a decision that a sender makes when constructing datagrams.¶

When sending SCONE packets, endpoints MUST include the SCONE packet as the first packet in a datagram, coalesced with additional packets.¶

Upon confirmation that the peer is willing to receive SCONE packets, an endpoint SHOULD include SCONE packets in the first few UDP datagrams that it sends. Doing so increases the likelihood of eliciting early throughput advice from network elements, allowing applications to apply that advice from the early stages of the data transfer.¶

After that, endpoints that seek to receive throughput advice on a flow MUST send a SCONE packet at least twice each monitoring period; see Section 5.2.¶

Sending SCONE packets more often might be necessary to:¶

Avoid missing advice:

If SCONE packets are not sent, updated, and received for an entire monitoring period, an application might incorrectly assume that no advice is being provided.¶

Reduce latency:

The time between SCONE packets determines the maximum delay between changes in throughput advice and when that advice can be received and acted upon.¶

A sender can track the receipt of the coalesced QUIC packet and send another SCONE packet when loss is detected. However, it is likely simpler to send SCONE packets more often.¶

Sending a SCONE packet every 20–30 seconds is likely sufficient to ensure that throughput advice is not lost, though endpoints might send a packet every few seconds to improve responsiveness. This period could be determined by how quickly an application is able to respond to a change in throughput advice.¶

For example, a streaming application that fetches video segments that are 5 seconds in length might send SCONE packets on a similar cadence. A real-time conferencing application might send more often. In either case, the length of the monitoring period (Section 5.2) limits how fast any application can react.¶

Though sending SCONE packets more than once each round trip time might help reduce exposure to packet loss, it is better to spread updates over time rather than to send multiple SCONE packets in less frequent bursts.¶

The main cost associated with sending SCONE packets is the reduction in available space in datagrams for application data.¶

A network element that wishes to signal updated throughput advice waits for the next SCONE packet in the desired direction; see Section 7.1.¶

8.2. Feedback To Sender About Signals

Information about throughout advice is intended for the sending application. Any signal from network elements can be propagated to the receiving application using an implementation-defined mechanism.¶

This document does not define a means for indicating what was received. That is, the expectation is that any signal is propagated to the application for handling, not handled automatically by the transport layer. How a receiving application communicates the throughput advice signal to a sending application will depend on the application in use.¶

Different applications can choose different approaches. For example, in an application where a receiver drives rate adaptation, it might not be necessary to define additional signaling.¶

A sender can use any acknowledgment mechanism provided by the QUIC version in use to learn whether datagrams containing SCONE packets were likely received. This might help inform whether to send additional SCONE packets in the event that a datagram is lost. However, rather than relying on transport signals, an application might be better able to indicate what has been received and processed.¶

SCONE packets could be stripped from datagrams in the network, which cannot be reliably detected. This could result in a sender falsely believing that no network element applied a throughput advice signal. Senders will therefore proceed as though there was no advice.¶

8.3. Interactions with Congestion Control

SCONE and congestion control both provide the application with estimates of a path capacity. They are complementary. Congestion control algorithms are typically designed to quickly detect and react to congestion, i.e., to the "minimum" capacity of a path. SCONE informs the endpoint of the maximum capacity of a path based on network rate limit policy, network conditions, or a combination of the two.¶

Consider for example a path in which the bottleneck router implements some form of Early Congestion Notification [ECN]. If the path capacity diminishes, queues will build up and the router will immediately start increasing the rate at which packets are marked as "Congestion Experienced". The receiving endpoint will notice these marks, and inform its peer. The incoming congestion will be detected in 1 round trip time (RTT). This scenario will play out whatever the reason for the change in capacity, whether due to increased competition between multiple applications or, for example, to a change in capacity of a wireless channel.¶

9.1. Fake SCONE Packets

Attackers that can inject packets could compose arbitrary "SCONE-like" packets by selecting a pair of IP addresses and ports, an arbitrary rate signal, a valid SCONE version number, an arbitrary "destination connection ID", and an arbitrary "source connection ID". A coalesced "1RTT" packet will start with a plausible first octet, and continue with the selected destination connection ID followed by a sufficiently long series of random bytes, mimicking the content of an encrypted packet.¶

Endpoints will reject such packets because they do not contain valid QUIC packets, but network elements cannot detect this. All the network elements between the injection point and the destination will have to process these packets.¶

Attackers could send a high volume of these "fake" SCONE packets in a denial of service (DOS) attempt against network elements. The attack will force the intermediaries to process the fake packets. If network elements are keeping state for ongoing SCONE flows, this might exhaust memory resources. The mitigation is the same as for other distributed DOS attacks: limit the rate of SCONE packets that a network element is willing to process; possibly, implement logic to distinguish valid SCONE packets from fake packets; or, use generic protection against Distributed DOS attacks.¶

Attackers could also try to craft the fake SCONE packets in ways that trigger a processing error at network elements. For example, they might pick connection identifiers of arbitrary length. Network elements can mitigate these attacks with implementations that fully conforms to the specification of Section 5.¶

9.2. Damage to Other Protocols

Network elements that update SCONE packet fields might do that for datagrams exchanged in other protocols. This could result in damage to those protocols.¶

The most serious damage occurs when every datagram is modified, because that could mean that the protocol is effectively unable to operate end-to-end.¶

To that end, network elements MUST only update the content of datagrams on a given address tuple a few times each monitoring period. Network elements MAY update more often immediately after a change in their throughput advice, to reduce the reaction time from senders.¶

In addition, some heuristics might be used to detect SCONE-compatible QUIC flows. This includes identification of a QUIC handshake on the flow, the presence of indications (Section 6.1), or other heuristics. If these heuristics indicate a non-QUIC flow, the safest option is for network elements to disable updating of datagrams.¶

10.1. Passive Attacks

If only few clients and server pairs negotiate the usage of SCONE, the occasional observation of SCONE packets will "stick out". That observation, could be combined with observation of timing and volume of traffic to help identify the endpoint or categorize the application that they are using.¶

A variation of this issue occurs if SCONE is widely implemented, but only used in some specific circumstances. In that case, observation of SCONE packets reveals information about the state of the endpoint.¶

If multiple servers are accessed through the same front facing server, Encrypted Client Hello (ECH) may be used to prevent outside parties to identify which specific server a client is using. However, if only a few of these servers use SCONE, any SCONE packets will help identify which specific server a client is using.¶

This issue will be mitigated if SCONE becomes widely implemented, and if the usage of SCONE is not limited to the type of applications that make active use of the signal.¶

QUIC implementations are therefore encouraged to make the feature available unconditionally. Endpoints might send SCONE packets whenever a peer can accept them.¶

10.2. Active Attacks

Suppose a configuration in which multiple clients use a VPN or proxy service to access the same server. The attacker sees the IP addresses in the packets behind VPN and proxy and also between the users and the VPN, but it does not know which VPN address corresponds to what user address.¶

Suppose now that the attacker selects a flow on the link between the VPN/proxy and server. The attacker applies throughput advice signals to SCONE packets in that flow. The attacker chooses a bandwidth that is lower than the "natural" bandwidth of the connection. A reduction in the rate of flows between client and VPN/proxy might allow the attacker to link the altered flow to the client.¶

An attacker that can manipulate SCONE headers can also simulate congestion signals by dropping packets or by setting the ECN CE bit. That will also likely result in changes in the congestion response by the affected client.¶

A VPN or proxy could defend against this style of attack by removing SCONE (and ECN) signals. There are few reasons to provide per-flow throughput advice signals in that situation. Endpoints might also either disable this feature or ignore any signals when they are aware of the use of a VPN or proxy.¶

11.1. SCONE Versions

This document registers the following entries to the "QUIC Versions" registry maintained at https://www.iana.org/assignments/quic, following the guidance from Section 22.2 of [QUIC].¶

Value:

0x6f7dc0fd¶

Status:

permanent¶

Specification:

This document¶

Change Controller:

IETF (iesg@ietf.org)¶

Contact:

QUIC Working Group (quic@ietf.org)¶

Notes:

SCONE Protocol - Low Range¶

Value:

0xef7dc0fd¶

Status:

permanent¶

Specification:

This document¶

Change Controller:

IETF (iesg@ietf.org)¶

Contact:

QUIC Working Group (quic@ietf.org)¶

Notes:

SCONE Protocol - High Range¶

11.2. scone_supported Transport Parameter

This document registers the scone_supported transport parameter in the "QUIC Transport Parameters" registry maintained at https://www.iana.org/assignments/quic, following the guidance from Section 22.3 of [QUIC].¶

Value:

0x219e¶

Parameter Name:

scone_supported¶

Status:

Permanent¶

Specification:

This document¶

Date:

This date¶

Change Controller:

IETF (iesg@ietf.org)¶

Contact:

QUIC Working Group (quic@ietf.org)¶

Notes:

(none)¶

12.1. Normative References

[BCP14]

Best Current Practice 14, <https://www.rfc-editor.org/info/bcp14>.
At the time of writing, this BCP comprises the following:

Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/RFC2119, March 1997, <https://www.rfc-editor.org/info/rfc2119>.

Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, May 2017, <https://www.rfc-editor.org/info/rfc8174>.

[INVARIANTS]

Thomson, M., "Version-Independent Properties of QUIC", RFC 8999, DOI 10.17487/RFC8999, May 2021, <https://www.rfc-editor.org/rfc/rfc8999>.

[QUIC]

Iyengar, J., Ed. and M. Thomson, Ed., "QUIC: A UDP-Based Multiplexed and Secure Transport", RFC 9000, DOI 10.17487/RFC9000, May 2021, <https://www.rfc-editor.org/rfc/rfc9000>.

[QUIC-BIT]

Thomson, M., "Greasing the QUIC Bit", RFC 9287, DOI 10.17487/RFC9287, August 2022, <https://www.rfc-editor.org/rfc/rfc9287>.

[QUICv2]

Duke, M., "QUIC Version 2", RFC 9369, DOI 10.17487/RFC9369, May 2023, <https://www.rfc-editor.org/rfc/rfc9369>.

[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, <https://www.rfc-editor.org/rfc/rfc2474>.

12.2. Informative References

[DASH]

"Information technology — Dynamic adaptive streaming over HTTP (DASH) — Part 1: Media presentation description and segment formats", ISO/IEC 23009-1:2022, August 2022, <https://www.iso.org/standard/83314.html>.

[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, <https://www.rfc-editor.org/rfc/rfc3168>.

[HLS]

Pantos, R., Ed. and W. May, "HTTP Live Streaming", RFC 8216, DOI 10.17487/RFC8216, August 2017, <https://www.rfc-editor.org/rfc/rfc8216>.

[QUIC-MP]

Liu, Y., Ma, Y., De Coninck, Q., Bonaventure, O., Huitema, C., and M. Kühlewind, "Managing multiple paths for a QUIC connection", Work in Progress, Internet-Draft, draft-ietf-quic-multipath-18, 8 December 2025, <https://datatracker.ietf.org/doc/html/draft-ietf-quic-multipath-18>.

[RFC4787]

Audet, F., Ed. and C. Jennings, "Network Address Translation (NAT) Behavioral Requirements for Unicast UDP", BCP 127, RFC 4787, DOI 10.17487/RFC4787, January 2007, <https://www.rfc-editor.org/rfc/rfc4787>.

[WHY-ECN]

Fairhurst, G. and M. Welzl, "The Benefits of Using Explicit Congestion Notification (ECN)", RFC 8087, DOI 10.17487/RFC8087, March 2017, <https://www.rfc-editor.org/rfc/rfc8087>.