Introduction to OMA-DM protocol

OMA-DM stands for Open Mobile Alliance Device Management. It is the protocol that supports communication between the Access Network Discovery and Selection Function (ANDSF) server and Client. This protocol is based on client-server architecture. It is IP based and is related to the transport protocol used. This protocol is based on SyncML which is a lighter version of XML. It uses a messaging sequence that consists of three parts: 

Alert Phase: 

This is an optional phase used for server-initiated management sessions. In this phase, data flows only from server to client. When the server wants to push settings to the device, it has to send a notification packet to it to start new management session. This phase is done using Wireless Application Protocol (WAP) push message over the SMS bearer. 

Setup phase: 

This is a mandatory phase used for authentication and device management purpose. In this phase, data flows between UE to the ANDSF server. The client sends and setup request which is followed by server response. The setup request has the following information: 

      1) Device information like the device ID, phone language and model tag 

      2)Client credentials for authentication purpose 

      3) Session origin which determines who initiated the session

Data Management Session: 

The setup phase ends with the server sending the command to the client. In this phase, the client sends status information to the server in response to the command's received.  After this, the server sends commands to the client or indicate that there are no more operations. If the server sends there are no more options, then the client stops sending messages to the server and close the session. 

The first two phases are carried over a TLS session with UE and server. Note that the session is always started by the client but the server may request with the notification alert SMS.  In General Authentication Architecture (GAA), the TLS session is secured using the PSK key. In the generic OMA-DM mode, it is a normal HTTPS session. 

If GAA is not used, the server responds to the client with its credentials for authentication purposes. Also, along with the credentials, it sends initial DM commands. In OMA-DM mode, the server issues commands and the client follows them.  

 

OMA-DM Management objects: 

In OMA-DM, the device configuration data is arranged in the hierarchical manner called device management tree. In this tree, subtrees are called as device management nodes and leaf nodes are called as Manageable Objects (MO). Note that the ANDSF MO is subtree under “./ANDSF” node. It uses SyncML messages to manipulate Manageable objects using the following commands: 

1) Add – Add a node to the device management tree 

2) Get – Get the name of the node based on the URI request in GET method 

3) Replace – Replace an object of the device management tree 

4) Delete – Delete an object of the device management tree 

5) Copy – Copy an object of the device management tree 

6) Exec –Exceutes the device defined command on the object int the device management tree 

The ANDSF MO generally uses ADD, DELETE, GET, and REPLACE frequently. Each MO is an interface for functionality and the following MO are mandatory in OMA-DM. 

1) Devinfo 
2) DevDetail 
3) DmAcc