<include>
  <gateway name="sip_gw">
    <param name="username" value="+123456789"/>
    <param name="auth-username" value="+123456789@ims.mno.com"/> //for digest authentication 
    <param name="password" value="1234"/>
    <param name="outbound-proxy" value="1.1.1.1"/>
    <param name="register" value="true"/>
    <param name="realm" value="ims.mno.com"/> // it will take gateway name (sip_gw) if blank 
    <param name="proxy" value="ims.mno.com"/> 
    <param name="sip_cid_type" value="pid"/>
    <param name="caller-id-in-from" value="true"/>
    <variables>
       <variable name="sip_h_P-Asserted-Identity" value="sip:123456789@1.1.1.1;user=phone"/>
       <variable name="sip_invite_to_params" value="user=phone"/>
       <variable name="sip_invite_from_params" value="user=phone"/>
    </variables>
  </gateway>
</include>