Name node and Data node protocol

[#1]

Hello,

From my understanding namenode and datanodes uses RPC to protocol to exchange data between name node and datanodes (HDFS data). Is this correct Or Do they used different protocol?

[#2]

@Mokkan Mok

Below is the note form HDFS documentation:

"All HDFS communication protocols are layered on top of the TCP/IP protocol. A client establishes a connection to a configurable TCP port on the NameNode machine. It talks the ClientProtocol with the NameNode. The DataNodes talk to the NameNode using the DataNode Protocol. A Remote Procedure Call (RPC) abstraction wraps both the Client Protocol and the DataNode Protocol. By design, the NameNode never initiates any RPCs. Instead, it only responds to RPC requests issued by DataNodes or clients."

Ref: https://hadoop.apache.org/docs/r3.1.0/hadoop-project-dist/hadoop-hdfs/HdfsDesign.html#The_Communicat...