Bringing Multipath capabilities in QUIC

During the last years, the use cases for Multipath TCP have continued to grow. Multipath TCP is used on all iPhones to provide seamless handovers and improve performance for Siri, Apple Music and other applications. This successful deployment has encouraged 3GPP to adopt it for the ATSSS service that will future 5G smartphones to seamlessly use Wi-Fi and cellular networks. Multipath TCP is also used by network operators to deploy hybrid access networks that combine cellular and xDSL networks.

In parallel with this deployment, the IETF has finalised the specification of the QUIC protocol. In a nutshell, QUIC combines the functions that are typically found in the transport and TLS layer in a single protocol that runs above UDP so that it can be implemented as a userspace library. When the QUIC working group was chartered, we argued for the inclusion of multipath capabilities in this new protocol. This item was added to the charter and we proposed a first design for Multipath QUIC.

The QUIC working group spent more time than expected on designing the protocol and we adapted the design of Multipath QUIC to the different changes to the protocol. The latest version of Multipath QUIC is cleaner and better adapted to QUIC. The multipath requirements remain and QUIC version only provides a poor man’s solution with its connection migration capabilities that have not yet been evaluated in the field.

On October 22nd, 2020, the chairs of the QUIC working group organised an interim meeting to better understand the multipath requirements and how they could be included in QUIC. Key presentations during this interim meeting include :

The recordings are also available on