You might meet this error : "object_detection/protos/model.proto:12:5: "Ssd" is not defined.", when you try below command.
# From tensorflow/models/research/
protoc object_detection/protos/*.proto --python_out=.
I solved this error to use below work.
# Make sure you grab the latest version
curl -OL https://github.com/google/protobuf/releases/download/v3.2.0/protoc-3.2.0-linux-x86_64.zip
unzip protoc-3.2.0-linux-x86_64.zip -d protoc3
# Move protoc to /usr/local/bin/
sudo mv protoc3/bin/* /usr/local/bin/
# Move protoc3/include to /usr/local/include/
sudo mv protoc3/include/* /usr/local/include/
# Optional: change owner
sudo chwon [user] /usr/local/bin/protoc
sudo chwon -R [user] /usr/local/include/google
refer to this url: