5.1 Use of MQTT

This binding makes use of MQTT to provide reliable two-way communications between two parties (AEs and CSEs). It uses the following features of MQTT:

• Durable Sessions, providing Store and Forward in cases where network connectivity is not available.
• MQTT's "QoS 1" message reliability level. This provides reliability without incurring the overhead implied by QoS 2.
• NAT traversal (neither of the two parties is required to have prior knowledge of the other party's IP address).
• Dynamic topic creation and wild-carded subscription filters.

It does not use the following features:

• One-to-many publish/subscribe.
• Retained Messages.
• Will Messages.
• QoS 0 or QoS 2 message reliability levels.