user62184: Let's say node is on a chain of length N+4, and receives a block from the chain of the same length N+4, but diverged by 4 blocks.

Is the information of the length and accumulated difficulty broadcasted along with mined block?
How will the recipient node handle this situation?


user31586: This phenomenon is known as a chain-split (i.e. the bitcoin network can no longer agree which chain is the canonical chain).
Nodes will be network-partitioned until one chain becomes dominant.
Therefore:

Is the information of the length and accumulated difficulty broadcasted along with mined block?

No. 

How will the recipient node handle this situation?

Nodes will handle equal branches on a First Come, First Serve basis, so there will be a network partition where some nodes agree chain A with length N+4 is the canonical chain and the other set of nodes will assume chain B with length N+4 is the canonical chain. In the event of such a chain-split, the race is on for miners to produce a new block-tip and broadcast it across the bitcoin network ASAP to achieve convergence. When the contention is resolved, the node can switch to longer branch and obsolete the old branch.

62184: <p>Let's say node is on a chain of length N+4, and receives a block from the chain of the same length N+4, but diverged by 4 blocks.</p>

<ol>
<li><p>Is the information of the length and accumulated difficulty broadcasted along with mined block?</p></li>
<li><p>How will the recipient node handle this situation?</p></li>
</ol>
 31586: <p>This phenomenon is known as a chain-split (i.e. the bitcoin network can no longer agree which chain is the canonical chain).</p>

<p>Nodes will be network-partitioned until one chain becomes dominant.</p>

<p>Therefore:</p>

<blockquote>
  <p>Is the information of the length and accumulated difficulty broadcasted along with mined block?</p>
</blockquote>

<p>No. </p>

<blockquote>
  <p>How will the recipient node handle this situation?</p>
</blockquote>

<p>Nodes will handle equal branches on a First Come, First Serve basis, so there will be a network partition where some nodes agree chain A with length N+4 is the canonical chain and the other set of nodes will assume chain B with length N+4 is the canonical chain. In the event of such a chain-split, the race is on for miners to produce a new block-tip and broadcast it across the bitcoin network ASAP to achieve convergence. When the contention is resolved, the node can switch to longer branch and obsolete the old branch.</p>
