Draft ADR about network properties and etcd implementation

cardano-scaling · Feb 12, 2025 · 433ccc6 · 433ccc6
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diff --git a/docs/adr/2022-03-28_017-udp-networking.md b/docs/adr/2022-03-28_017-udp-networking.md
@@ -3,12 +3,12 @@ slug: 17
 title: |
   17. Use UDP protocol for Hydra networking
 authors: []
-tags: [Proposed]
+tags: [Superseded]
 ---
 
 ## Status
 
-Proposed
+Superseded (as never implemented) by [ADR 32](/adr/32)
 
 ## Context
 

diff --git a/docs/adr/2023-09-09_027-network-resilience.md b/docs/adr/2023-09-09_027-network-resilience.md
@@ -3,12 +3,12 @@ slug: 27
 title: |
   27. Network failures model
 authors: [abailly, pgrange]
-tags: [Accepted]
+tags: [Superseded]
 ---
 
 ## Status
 
-Accepted
+Superseded by [ADR 32](/adr/32)
 
 ## Context
 

diff --git a/docs/adr/2025-02-12_032-network-properties-etcd.md b/docs/adr/2025-02-12_032-network-properties-etcd.md
@@ -0,0 +1,46 @@
+---
+slug: 32
+title: |
+  32. Network layer properties, implementation using etcd
+authors: [ch1bo]
+tags: [Accepted]
+---
+
+## Status
+
+Accepted
+
+## Context
+
+TODO write context
+
+- First relevant is [ADR 6](/adr/6) which defines the multicast/broadcast primitive
+- Related to [ADR 27](/adr/27)
+  - re-confirm the failure model
+  - superseded decision taken in there 
+- correspondence of reliable broadcast and consensus
+- summarize properties of network layer
+
+## Decision
+
+- We supersede [ADR 17](/adr/17) and [ADR 27](/adr/27) with the current ADR.
+
+TODO write decision
+
+- Define properties of the network layer
+- Precise definition of broadcast to be a reliable broadcast (including Agreement)
+  - https://hydra.family/head-protocol/docs/dev/architecture/networking#interface
+
+TODO write decision (separate ADR?)
+
+- Decide to use `etcd` as a proxy to achieve reliable broadcast via its raft consensus
+- (or consequence?) Change of `PeerConnected` to `HydraNetworkConnected` semantics
+
+## Consequences
+
+TODO write consequences
+
+- Drop existing implementation using `Reliability` layer (could be revisited, as in theory it would satisfy properties if implemented correctly -> link to Cachin, Uniform reliable broadcast = only deliver when seen by everyone = not what we had implemented)
+- Run time dependency on `etcd`
+- Improved introspectability
+- Crash tolerance of up to `n/2` failing nodes