code: public void write(DataOutput out) throws IOException {
      if (getDataTransferVersion() >= DataTransferProtocol.FEDERATION_VERSION) {
        out.writeInt(namespaceId);
      }
      out.writeLong(blockId);
      out.writeLong(numBytes);
      out.writeLong(genStamp);
      out.writeInt(pipelineDepth);
      getWritePipelineInfo().write(getDataTransferVersion(), out);
    }
docs: ///////////////////////////////////