# Delay-Tolerant Networking

Delay-Tolerant Networking (DTN) is a networking approach that enables communication over networks with intermittent or disrupted connectivity, such as those found in mobile, satellite, or disaster-recovery scenarios, by using store-and-forward messaging and routing protocols that can tolerate delays, disruptions, and partitions in the network.

Z-Mesh supports Delay-Tolerant Networking as data is stored in the network. When Content is produced it labeled with a sequence-number (FSEQ), this allows for later retrieval when connectivity is restored.

# Content is numbered

Get Content

When a motion sensor in the 3rd floor meetingroom-341 produces data, successive events produced by the motion-sensor will have the same Content Name, and it's Frame Sequence Number (FSEQ) is incremented.

ContentName=location/hq/floor/3/room/mr341/motion, FSEQ=840

Successive motion-sensor events will therefore have Frame Sequence numbers FSEQ=841, FSEQ=842, FSEQ=843...

# Network split

What happens when a Z-Mesh network is split into multiple networks? Maybe parts of your network is mobile or maybe you want to be independent of cloud-connectivity.

Delay tolerant

Z-Mesh is a distributed network, so all networks will continue to operate normally, except that they will not receive data from networks that there is no connection to. Content generated by sensors and applications will continue to be stored in the network for later retrival by other networks.

When the connection between the two networks is restored, either by a temporary solution (eg. Drone) or because the Internet Connection is working again, data can then be retrieved by other networks using the Frame Sequence number (FSEQ). For example, if the database in the cloud last received motion-sensor event with FSEQ=839, it can request FSEQ=840, 841... when the connection is restored.