Start With The Message
Each wave begins with a source, a destination address, and a TTL value in the Network PDU.
BLE Mesh Managed Flooding Workbench
Step through Bluetooth Mesh relay decisions, TTL limits, duplicate cache drops, and relay placement tradeoffs.
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Interactive BLE Mesh animation showing managed flooding, Relay feature enablement, TTL stop rules, Network Message Cache duplicate suppression, group delivery, low-power nodes, proxy nodes, and directed forwarding contrast.
BLE Mesh Managed Flooding Workbench
Follow one Bluetooth Mesh message as it ripples through relay-enabled nodes, reaches its destination group, and gets stopped by TTL limits or the Network Message Cache.
Scenario
Stage lights group
TTL Rule
TTL 3 allows two relay waves
Relay Load
Balanced
Cache Drops
0 duplicates
Check Relay Eligibility
A node forwards only when its Relay feature is enabled and the received TTL is still greater than one.
Use The Cache
The Network Message Cache suppresses repeated receptions of the same source and sequence number.
Tune The Flood
Good relay placement and small-enough TTL values give coverage without wasting radio capacity.
Message Propagation Map
The source publishes a group message. Relay nodes rebroadcast it until TTL or cache rules stop the flood.
Source
Relay
Destination
Cache drop
Current Wave
Origin
Relay Transmits
0
Delivered
0 / 3
TTL Status
Ready
What Happened
Ready to publish
Press Play or Step to watch the first network wave leave the source.
Why It Matters
Managed flooding is controlled flooding
Relay enablement, TTL, and cache behavior keep the flood useful instead of unlimited.
Event Log
Bluetooth Mesh Quick Reference
MFManaged Flooding
Relays retransmit selected Network PDUs so the message spreads outward. It is simple, resilient, and intentionally not a route table.
RYRelay Feature
A Relay node supports and has enabled the Relay feature. Ordinary nodes can still receive and originate mesh messages.
TTTTL
TTL limits hop count. TTL 0 is single-hop only; TTL 1 is a stop/local value; TTL 2 or more may be relayed with decrement.
CAMessage Cache
All nodes implement a Network Message Cache. A repeated source and sequence number is discarded instead of processed again.
ADAddressing
Mesh messages target unicast, group, virtual, or fixed group addresses. A group message may have several valid recipients.
LPLow Power And Friend
Low Power Nodes conserve energy by polling a Friend node that stores messages for them. They are usually not relay workhorses.
PXProxy
A Proxy node bridges GATT-connected devices, such as phones, to mesh network PDUs carried over the advertising bearer.
DFDirected Forwarding
Bluetooth Mesh 1.1 adds directed forwarding for more informed relaying. This page focuses on managed flooding behavior.
Learning Support
- First set TTL to 0. Notice that neighbors may hear the message, but nobody relays it.
- Then use TTL 2 or 3. Watch how each relay wave consumes one TTL count.
- Switch to the duplicate path scenario. The same destination can hear the message from several relays, but the cache prevents reprocessing.
- Compare sparse and dense relay placement. Sparse relays can miss parts of the building; dense relays create more airtime pressure.
Technical Accuracy Notes
- This workbench models Bluetooth Mesh managed flooding, not IP routing and not Bluetooth Mesh directed forwarding.
- A relay decision is simplified to the core learner rules: relay feature enabled, first reception in cache, and received TTL greater than one.
- The demo uses TTL 0 to 7 so the waves stay readable. Bluetooth Mesh supports a larger field, but normal teaching examples should avoid implying that a high TTL is automatically good design.
- Security is shown at concept level: relays forward network PDUs and do not need to understand the application model payload.