ConEx

Congestion Exposure (ConEx) is a mechanism by which senders inform the network about expected congestion based on congestion feedback from previous packets in the same flow. This document describes the necessary modifications to use ConEx with the Transmission Control Protocol (TCP).

Congestion Exposure (ConEx) is a mechanism by which senders inform the network about the congestion encountered by packets earlier in the same flow. This document specifies an IPv6 destination option that is capable of carrying ConEx markings in IPv6 datagrams.

This memo describes a mobile communications use case for congestion exposure (ConEx) with a particular focus on those mobile communication networks that are architecturally similar to the 3GPP Evolved Packet System (EPS). This memo provides a brief overview of the architecture of these networks (both access and core networks) and current QoS mechanisms and then discusses how congestion exposure concepts could be applied. Based on this discussion, this memo suggests a set of requirements for ConEx mechanisms that particularly apply to these mobile networks.

This document describes an abstract mechanism by which senders inform the network about the congestion recently encountered by packets in the same flow. Today, network elements at any layer may signal congestion to the receiver by dropping packets or by Explicit Congestion Notification (ECN) markings, and the receiver passes this information back to the sender in transport-layer feedback. The mechanism described here enables the sender to also relay this congestion information back into the network in-band at the IP layer, such that the total amount of congestion from all elements on the path is revealed to all IP elements along the path, where it could, for example, be used to provide input to traffic management. This mechanism is called Congestion Exposure, or ConEx. The companion document, "Congestion Exposure (ConEx) Concepts and Use Cases" (RFC 6789), provides the entry point to the set of ConEx documentation.

This document provides the entry point to the set of documentation about the Congestion Exposure (ConEx) protocol. It explains the motivation for including a ConEx marking at the IP layer: to expose information about congestion to network nodes. Although such information may have a number of uses, this document focuses on how the information communicated by the ConEx marking can serve as the basis for significantly more efficient and effective traffic management than what exists on the Internet today. This document is not an Internet Standards Track specification; it is published for informational purposes.