diff --git a/beacon_node/network/src/message_handler.rs b/beacon_node/network/src/message_handler.rs
index 0e56b4c331..0050bd0e66 100644
--- a/beacon_node/network/src/message_handler.rs
+++ b/beacon_node/network/src/message_handler.rs
@@ -204,7 +204,7 @@ impl<T: BeaconChainTypes + 'static> MessageHandler<T> {
                     let should_forward_on = self
                         .message_processor
                         .on_block_gossip(peer_id.clone(), block);
-                    // TODO: Apply more sophisticated validation and decoding logic
+                    // TODO: Apply more sophisticated validation and decoding logic - 524 verify block
                     if should_forward_on {
                         self.propagate_message(id, peer_id.clone());
                     }
@@ -215,7 +215,7 @@ impl<T: BeaconChainTypes + 'static> MessageHandler<T> {
             },
             PubsubMessage::Attestation(message) => match self.decode_gossip_attestation(message) {
                 Ok(attestation) => {
-                    // TODO: Apply more sophisticated validation and decoding logic
+                    // TODO: Apply more sophisticated validation and decoding logic - 524 verify attestation
                     self.propagate_message(id, peer_id.clone());
                     self.message_processor
                         .on_attestation_gossip(peer_id, attestation);
@@ -297,7 +297,7 @@ impl<T: BeaconChainTypes + 'static> MessageHandler<T> {
         &self,
         beacon_block: Vec<u8>,
     ) -> Result<BeaconBlock<T::EthSpec>, DecodeError> {
-        //TODO: Apply verification before decoding.
+        //TODO: Apply verification before decoding. - 524
         BeaconBlock::from_ssz_bytes(&beacon_block)
     }
 
@@ -305,7 +305,7 @@ impl<T: BeaconChainTypes + 'static> MessageHandler<T> {
         &self,
         beacon_block: Vec<u8>,
     ) -> Result<Attestation<T::EthSpec>, DecodeError> {
-        //TODO: Apply verification before decoding.
+        //TODO: Apply verification before decoding. - 524
         Attestation::from_ssz_bytes(&beacon_block)
     }
 
diff --git a/beacon_node/network/src/sync/simple_sync.rs b/beacon_node/network/src/sync/simple_sync.rs
index 83aa7ebd29..34f36f8c18 100644
--- a/beacon_node/network/src/sync/simple_sync.rs
+++ b/beacon_node/network/src/sync/simple_sync.rs
@@ -387,7 +387,16 @@ impl<T: BeaconChainTypes> MessageProcessor<T> {
     ///
     /// Attempts to apply to block to the beacon chain. May queue the block for later processing.
     ///
-    /// Returns a `bool` which, if `true`, indicates we should forward the block to our peers.
+    /// Returns a `bool` which, if `true`, indicates we should forward the block to our peers. 524
+    /// Old blocks or blocks on a different fork. Will need to recalc proposer shuffle.
+    /// May need heuristics...
+    /// Cases:
+    /// Do we know the block's parent?
+    /// 1.) It's a recent block on the same chain. We can use the current cache in the BeaconChain. (cheap)
+    /// 2.) Old block on a different fork. (may have to recalc shuffling)
+    /// If we don't know the block's parent, we don't who is supposed to sign it, therefore we can
+    /// not validate the signature.
+    /// 1.) We can try to look up the block's parent using the syncing thread. (it's expensive not sure how to reprop from sync thread)
     pub fn on_block_gossip(&mut self, peer_id: PeerId, block: BeaconBlock<T::EthSpec>) -> bool {
         match self.chain.process_block(block.clone()) {
             Ok(outcome) => match outcome {