DTN Store-Carry-Forward Animation

DTN Store-Carry-Forward Animation

Trace how delay-tolerant networks store a bundle, carry it through disconnection, and forward it during short contacts.

animation
dtn
wsn
architecture
routing
interactive
Interactive DTN store-carry-forward animation with moving bundles, contact windows, buffer pressure, forwarding strategy comparison, delivery estimates, and mobile-friendly learning support.
Delay-tolerant networking Store-carry-forward Intermediate

Store a bundle, carry it through disconnection, forward it when contact appears.

DTN does not assume a live end-to-end route. This animation shows how a bundle survives disconnected time by living in node buffers, moving with mobile carriers, and transferring only during short contact windows.

88% estimated delivery probability for this trace
28 h expected delivery latency, not round-trip delay
1 copy active bundle copies carried in the network
3.1x copy overhead compared with one delivered bundle
TryReduce Buffer slots per node to 4, keep contact capacity at 80 KB/s, and select Play.
ObserveFollow Buffered bundles, Evicted and Delivery ratio across contact windows; arrivals that cannot wait for the next contact are dropped.
ExplainStore-carry-forward moves bundles only during a contact opportunity. Finite slots and a 48 h TTL independently bound how many messages survive until a usable path appears.
Technical boundariesThe contact schedule is deterministic and leaves out mobility uncertainty, custody-transfer failures, energy consumption, corrupted storage, routing-policy negotiation, security decisions and heterogeneous radio rates.
Colour keyemerging paradigms identitycurrent / primaryreference / datasuccesscautionerror / failure

DTN Store-Carry-Forward Workbench

Goal

See why DTN treats disconnection as normal operating state, not as a broken route.

Try

Use 4 Buffer slots per node and Play until the first scheduled contact opens; then inspect which bundle receives the slot.

Watch

The bundle token should sit in storage, move with a carrier, and only cross links during contact windows.

Reflect

Pick the cheapest strategy that still meets the application delay and reliability requirement.

Bundle journey

A source stores a bundle while no path exists. Contacts appear as nodes move into radio range.

Store
Store at source The bundle waits in local storage because no simultaneous path to the destination exists.
1 copy
1 Store Bundle enters nonvolatile local storage.
2 Contact Nodes exchange summaries when radios overlap.
3 Carry Carrier moves while disconnected.
4 Forward Strategy decides whether a better carrier gets a copy.
5 Deliver Destination contact completes the payload transfer.
6 Retire TTL, status reports, or policy remove stale copies.

Readouts

180 KB payload size
3.28 MB one-contact capacity
25% buffer pressure
limited copy current forwarding decision
Strategy diagnosis

Spray-and-wait limits extra copies while still giving several mobile carriers a chance to meet the destination.

Controls

Select a deployment pattern.

Choose how a contact forwards the bundle.

Learning support

DTN is not simply slow TCP/IP. Traditional routing expects a contemporaneous path. DTN accepts that the useful path may be spread over time.

  • Store: a bundle persists in a node buffer while disconnected.
  • Carry: mobility transports the bundle between disconnected regions.
  • Forward: a contact window lets nodes exchange summaries and transfer useful bundles.
  • Retire: delivery, TTL expiration, or policy removes stale copies.
Strategy quick reference
Strategy Use when Watch out
Direct Source is likely to meet destination and energy is scarce. Delivery may wait a long time or fail within TTL.
Epidemic Message is critical and buffers, energy, and bandwidth are available. Copies can overwhelm radios and storage.
Spray-and-wait You need bounded overhead with better delivery odds than direct. Too few tickets can strand the bundle.
PRoPHET-style Mobility has history or regular patterns. Bad history gives false confidence.
Technical checks

This demo uses teaching estimates, not a full simulator. The formulas connect the visible behavior to real design factors.

  • Contact capacity: bandwidth multiplied by contact duration. If it is smaller than the payload, a real system needs fragmentation or another contact.
  • Delivery probability: a rough trace estimate based on TTL, range, strategy, and predictability.
  • Bundle Protocol: BPv7 is RFC 9171. Reliability is not an end-to-end TCP session; it depends on bundle lifetime, status reports, convergence layers, and local policy.
  • Latency: DTN latency is often minutes, hours, or days. It is acceptable only when the application can tolerate delay.
TTL limits stale storage Buffers are finite Contacts are short Copies cost energy

Related resources

Use these after the animation to connect the trace to surrounding course material.

DTN fundamentals Epidemic and spray-and-wait Social and PRoPHET-style routing Human-centric WSN and DTN Ad-hoc self-organization