Priming QUIC with Peer Hints for Atypical Networks, such as Delay-Tolerant Networks(DTN)

Abstract

Abstract¶

1. Introduction

Long delay networks such as in space communications may possibly use the IP protocol as IP as no notion of delivery time. However, it requires that the transport and application layers work properly in the context of long delays. In space radio communications, it is typical to have delays in order of multiple minutes and maybe hours. This document describes a configuration profile for QUIC and HTTP3 implementations to properly work in these scenarios. It can also be used for any use case where some initial QUIC parameters should be changed from the defaults.¶

2. Peer Hints

A QUIC stack is primed with a config that defines various parameters for a destination, so that the QUIC stack converges faster. For example, when a network is known to be "far", with a large and known in advance latency, such as in space, the QUIC stack is primed with an initial RTT of that destination, for example 20 minutes, so that the QUIC RTT calculation is converging much faster and does not generate a lot of useless retransmits and does not timeout. It should be noted that these priming values are just hints and the QUIC stack may decide to not honor them, or to use more prudent values. For example, if the value is very large, the QUIC stack may decide to start with half of the proposed value.¶

The properties and their values are as follows. All values must follow the maximums specified in their corresponding definitions in QUIC RFCs.¶

• destination: an IPv4 prefix in CIDR format [RFC4632] or an IPv6 prefix [RFC4291]. A single host may be expressed without the /length suffix.¶
• initial_rtt: unsigned integer. in ms. see [RFC9002] section 6.2.2¶
• max_idle_timeout: unsigned integer. in ms. see [RFC9000] section 18.2¶
• active_connection_id_limit: unsigned integer. see [RFC9000] section 18.2¶
• TBD: others?¶

3. File Format

The values are expressed in a JSON object, typically stored as a file.¶

The top-level properties are as follows:¶

• type: mandatory. always set to "quicPeerHints". This enables identification of that file outside of the expected context.¶
• version: mandatory. this document set to 1. New specifications may define new versions.¶
• lastUpdated: mandatory. the last time this file was updated in [RFC3339] format¶
• quicHints: mandatory. a non-empty array of hints¶

The following is an example:¶

<CODE BEGINS>

{
  "type": "quicPeerHints",
  "version": 1,
  "lastUpdated": "2025-01-17T23:20:50Z",
  "quicHints": [
    {
      "destination": "2001:db8:1234::/48",
      "initial_rtt": 600000,
      "max_idle_timeout": 1500000,
      "active_connection_id_limit": 100000
    },
    {
      "destination": "192.0.2.0/24",
      "initial_rtt": 30000,
      "max_idle_timeout": 100000,
      "active_connection_id_limit": 10000
    }
  ]
}


<CODE ENDS>

4. Considerations

The mechanism to distribute such configuration to the QUIC stack is undefined in this document. For the use case that triggered this work, space networking, it is expected that these configuration will be fairly static, loaded in advance and very seldomly need to be updated. However, other use cases may require updates more often and therefore may need a protocol to distribute such configuration. A possible candidate protocol to update this configuration is [RFC8175] but that would apply to networks reachable via a single link where all the characteristics are inherited from that link.¶

Similarly to typical forwarding and routing algorithms, if a destination address matches multiple address prefixes, the most specific prefix will be used as a match. In case multiple prefixes have the same length, the last one encountered while parsing the file is the one used as a match¶

Some configuration values are defined in this document. However, it is possible that other parameters might need to be added in the future. Therefore, an IANA registry of values is defined to support future definition of parameters. The actual possible values or range of values for a specific parameter is not shown in the IANA registry. Discussion on the semantics of the parameter, its possible values, etc... must be in the referenced document. The IANA registry only contains the JSON syntax useful for a JSON parser.¶

7. TODO and Comments (section to be deleted when ready for publication)

a list of TODOs and comments not yet resolved in this version¶

• MT: remove active_connection_id_limit as not needed since negotiated and not need to be primed¶
• MT: consider initial congestion window. CH: Not tying the CWIN: very good. Starting with extra large CWIN can be very risky.¶
• CH: The idle timeout tends to be application specific. LP: h3-nginx config parameter in quiche¶
• CH: DOS attacks with spoofed packets. A single spoofed with address in the selected range will tie connection resource for a long time.¶
• MT: consider domain names. MB: I disagree because side effects of TTL=0, split views, ...¶

8. References