]> Okayama University

masa.koz@kozuka.jp

Transport QUIC QUIC failover multipath The proposed path failover mechanism provides a seamless way to recover from path failures in Multipath QUIC. It allows the protocol to take advantage of multiple paths while maintaining reliability and security. The implementation and deployment of this mechanism should be done with careful consideration of security and performance. 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 QUIC Working Group mailing list (), which is archived at . Subscribe at . Source for this draft and an issue tracker can be found at .

Introduction Multipath QUIC provides improved network performance and reliability by using multiple network paths concurrently. However, if one of the paths fails, it can cause a disruption in the communication. This document proposes a path failover mechanism for Multipath QUIC, which allows it to recover from path failures seamlessly.

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.

Path Failover Mechanism Multipath QUIC uses multiple paths to transfer data concurrently. Each path has its own metrics, such as RTT, available bandwidth, and congestion level. These metrics are monitored by the sender using the Path Quality Estimation (PQE) framework. When a path failure is detected, the sender chooses a new path to transfer data. The sender detects a path failure when the path metrics show a significant degradation. This can be caused by a network outage or congestion. If the path metrics remain degraded for a certain duration, the sender assumes the path has failed and triggers the failover mechanism. When the failover mechanism is triggered, the sender selects a new path to transfer data from a list of available paths. The selection criteria can be based on various factors, such as available bandwidth, RTT, and congestion level. The sender also considers the path diversity to choose a path that is different from the failed path. After selecting a new path, the sender checks whether it is valid by sending a connectivity check packet. If the path is valid, it starts sending data on the new path. If the new path also fails, the sender repeats the failover mechanism with a different path.

Security Considerations The failover mechanism should not compromise the security of the communication. The selection of a new path should not leak information about the failed path or the communication itself. Therefore, the selection criteria should not depend on any information that can be obtained by an eavesdropper. The connectivity check packet should be authenticated to prevent spoofing attacks. The sender should verify the authenticity of the packet before deciding to use the new path. The sender should also limit the number of failover attempts to prevent denial-of-service attacks. The failover mechanism should not introduce any new vulnerabilities to the Multipath QUIC protocol. Therefore, it should be thoroughly tested and reviewed before being deployed.

IANA Considerations This document has no IANA actions.

Normative References In many standards track documents several words are used to signify the requirements in the specification. These words are often capitalized. This document defines these words as they should be interpreted in IETF documents. This document specifies an Internet Best Current Practices for the Internet Community, and requests discussion and suggestions for improvements. RFC 2119 specifies common key words that may be used in protocol specifications. This document aims to reduce the ambiguity by clarifying that only UPPERCASE usage of the key words have the defined special meanings.

Acknowledgments TODO acknowledge.