To upgrade your multi server infrastructure, I would recommend following sequence:

• Upgrade the service discover server node. In your case, I assume your service discover server node (Consul Mesh server node) is same as your ldap node.
• Once service-discover server node is up with all services running, then upgrade all other nodes one by one.

Now about upgrading process on each nodes, follow the official guidelines as mentioned here:

https://docs.zextras.com/carbonio-ce/html/upgrade/toc.html

Keep in mind:

• Upgrading is a critical task, so make sure you have taken all precautions like, backups, snapshots etc. so that in case of unprecedented situation you can roll back to your previous state.

Thanks.