Multi-Path QUIC proxying IP in HTTP

Description

MPQUIC-IP, or Multi-Path QUIC proxying IP in HTTP, is a Release 19 feature that enables the transport of IP packets over HTTP using the Multi-Path QUIC (MPQUIC) protocol. It is part of 3GPP's framework for non-3GPP access to the 5G core network, specifically for devices that use IP as their network-layer protocol. The feature is specified in TS 24.193 (Access traffic steering, switching, and splitting) and TS 29.244 (Interface between the Control Plane and the User Plane of the 5G System).

In a 5G network, non-3GPP access can be integrated via the N3IWF or TNGF. MPQUIC-IP extends this by encapsulating IP packets into HTTP/3 messages, which are then carried over MPQUIC. MPQUIC is an extension of QUIC that supports simultaneous use of multiple network paths, providing benefits such as increased bandwidth, reduced latency, and improved resilience through path redundancy. By proxying IP in HTTP, MPQUIC-IP enables IP devices to connect to the 5G core using web-based protocols, simplifying deployment and leveraging the advantages of QUIC.

The architecture involves a client (the device or a proxy) and a server (the TNGF or N3IWF). The client encapsulates IP packets into HTTP/3 data streams, which are multiplexed over one or more QUIC connections. MPQUIC manages the multiple paths, scheduling packets across them based on policies. The server decapsulates the IP packets and forwards them to the 5G core via the appropriate interface (e.g., N2/N3). This approach allows for seamless mobility and multi-access aggregation, as the device can use multiple access networks simultaneously.

Key components include the MPQUIC-IP client, the MPQUIC-IP server, and the underlying QUIC transport. The client is typically integrated into the device's operating system or a dedicated application. The server resides in the TNGF or N3IWF. The feature relies on HTTP/3, which uses QUIC as its transport, and on MPQUIC for path management. 3GPP specifies the encapsulation format, the signaling for path establishment and teardown, and the interaction with the 5G core's session management functions.

MPQUIC-IP is particularly useful for mobile devices and IoT devices that use IP and need reliable, high-throughput connectivity over multiple access networks. It allows devices to benefit from 5G's reliability and performance without requiring complex IPsec tunnels. By using HTTP, it also aligns with web technologies, potentially simplifying integration with cloud services. The feature is part of Rel-19's broader work on enhancing non-3GPP access and multi-path support, and it is expected to be further refined in future releases.

Purpose & Motivation

MPQUIC-IP was created to address the need for efficient and reliable transport of IP traffic over non-3GPP access in 5G networks. Traditional methods for integrating IP devices into 5G, such as using IPsec tunnels or GTP-U, can be complex and may not fully leverage the capabilities of modern transport protocols. MPQUIC-IP solves this by using Multi-Path QUIC, which provides multiplexing, low-latency connection establishment, and multi-path support, all within an HTTP/3 framework.

The motivation comes from the growing demand for IP-based services in mobile and IoT environments, where devices require seamless connectivity and high reliability. By proxying IP in HTTP, MPQUIC-IP allows these devices to connect to the 5G core through a web-friendly protocol, enabling easier integration with application servers and cloud platforms. It also supports multi-path operation, which can improve reliability by using multiple access networks simultaneously, and increase throughput by aggregating bandwidth.

Historically, 3GPP has defined various non-3GPP access mechanisms, but they were primarily IP-centric and often relied on IPsec. With the rise of QUIC and HTTP/3, Rel-19 introduced MPQUIC-IP to provide an IP-over-HTTP solution. This complements existing features like ATSSS and extends them to IP traffic. The feature is expected to simplify deployments and enhance performance for IP devices in 5G networks.