Add Section on config changes for block prop

Add section on config changes for improveing block propagatin for larger
blocks.

blog/2025-01-20-network.md

@@ -51,6 +51,39 @@ optimisations and is making progress on them. See
 
 We cut `ouroboros-network-0.19` and `0.19.1` [releases][on-releases].
 
+### Configuration Changes for Block Propagation Times
+
+Block propagation times are influenced by the number of TCP round trips
+required to transmit a block.
+
+In mid-December, we published a [post][cfpost] discussing configuration
+changes to the Linux IP stack. These adjustments involved increasing the
+initial TCP congestion window to 42 segments and ensuring that the
+congestion window remained open for idle connections.
+
+IOG applied these changes to four stake pools located in Brazil,
+South Africa, Dubai, and Japan around December 15th.
+
+The Cardano Foundation manages a standard peer-to-peer (P2P) node in Paris,
+which operates without manual connections to other Cardano
+Foundation nodes or IOG nodes. After implementing the configuration changes,
+we noted a statistically significant improvement in the propagation times
+for blocks larger than 10 segments (about 14,480 bytes) produced by IOG's pools.
+
+| Block Size (bytes)    | Improvement (ms) |
+| --------------------- | ---------------- |
+| 14,480 - 28,960       | -132 to -78      |
+| 28,960 - 57,920       | -197 to -130     |
+| >57,920               | -255 to -176     |
+
+<div style="text-align: center;">
+  <img src="/images/network/2025-01-20-blocks.png" alt="Block Propagation Times" width="600" />
+</div>
+
+These results demonstrate that a Stake Pool Operator (SPO) can enhance the
+propagation times of their own pool's blocks by applying config changes
+targeting TCP's congestion window.
+
 ## Low-level summary
 
 ### Querying Network State through Node-to-Client Protocol
@@ -116,3 +149,4 @@ data NetworkState peeraddr = NetworkState {
 [on#5044]: https://github.com/IntersectMBO/ouroboros-network/pull/5044
 [on#5046]: https://github.com/IntersectMBO/ouroboros-network/pull/5046
 [on-releases]: https://github.com/orgs/IntersectMBO/projects/5/views/18
+[cfpost]: https://forum.cardano.org/t/problem-with-increasing-blocksize-or-processing-requirements/140044/7