protocol buffers - protobuf message containing fields which are protobuf messages marshaling and unmarshaling -

i have protobuf message similar message below.

message {     message b xyz = 1; //message defined using message b here. } message b {     int age = 1; } 

now, when sending message of type a, want know if need marshal message b first, marshal - unmarshal msg (type a) followed unmarshal of xyz(type b) data?

i didn't find in protobuf documentation, maybe not required. wondering if simple marshal (type a) , unmarshal (type a) sufficient.