Open Stack

I am working on install openstack from scratch, but get confused with network part. I want to have one controller node, two compute nodes. 

the controller node will only handle following services:
glance-api
glance-registry
keystone
nova-api
nova-cert
nova-conductor
nova-consoleauth
nova-novncproxy
nova-scheduler
qpid
mysql
neutron-server

compute nodes will have following services:
neutron-dhcp-agent
neutron-l3-agent
neutron-metadata-agent
neutron-openvswitch-agent
neutron-ovs-cleanup
openvswtich
nova-compute

all three nodes will have eth0 on management/api network. since I am using ml2 plugin with vlan for tenant network, I think all compute node should have eth1 as the second nic on provider network. Is this correct?  I understand provider network is for instance to get external access  to internet, but how is instance live on compute1  communicate with instance live on compute2? are they also go through provider network?