message: Update protocol.hpp
  The word is misspelled.
diff: @@ -135,7 +135,7 @@ parallel fetches, request in groups
  only relay transactions to peers if we don't already know about it.
  -send a notification rather than a transaaction if the txn is > 3mtu size.
  +send a notification rather than a transaction if the txn is > 3mtu size.
  