Changes between Version 5 and Version 6 of Symbian_AP_Reconnection

Timestamp:

Feb 25, 2009 5:36:38 PM (15 years ago)

Author:

bennylp

Comment:

--

Symbian_AP_Reconnection

@@ -25 +25 @@
 [[BR]]
 
-== Issues ==
+== Issues and solution related to IP address change ==
 
 When the connection is reconnected, the handset may get different IP address than what it previously got. There are few ramifications of this, for example if PJSUA-LIB is used:
@@ -57 +57 @@
  The account URI needs to be updated with the new address, and re-registration is necessary to inform the registrar about the new URI.
 
- '''Solution:''' ::
+ '''Description:''' ::
  PJSUA-LIB has the capability to detect the (SIP) IP address change based on the response of REGISTER request and automatically update the registration with the correct IP if it detects that the IP/port seen by the server is different than the address specified in the Contact URI. This feature is enabled by default, via the {{{pjsua_acc_config.allow_contact_rewrite}}} setting.
 
@@ -67 +67 @@
  The media (RTP/RTCP) addresses in PJSUA-LIB are normally determined during PJSUA-LIB startup, hence they need to be updated with the new address.
 
- '''Solution:''' ::
+ '''Description:''' ::
  If ICE media transport is used, and STUN is enabled on the media transport, then the media transport will automatically update its publicly mapped IP address from the STUN Binding response. The transport should send STUN Binding request periodically (approximately every 15 seconds) as NAT keep-alive mechanism, so the address change will be detected by the transport automatically during this operation.
 
@@ -80 +80 @@
  Dialog's Contact URI needs to be updated.
 
- '''Solution:''' ::
+ '''Description:''' ::
  The dialog's Contact URI is set initially when the dialog is created, from the account's Contact URI. While at the PJSIP level the {{{pjsip_inv_reinvite()}}} allows changing of Contact URI via the {{{new_contact}}} argument, currently this feature is not used by PJSUA-LIB, i.e. the {{{pjsua_call_reinvite()}}} does not allow the application to change the Contact URI.
 
@@ -88 +88 @@
  Changing of RTP/RTCP media addresses of ongoing call
 
- '''Solution:''' ::
+ '''Description:''' ::
  If ICE is used, then new STUN srflx address will be signaled in updated SDP offer, as long as:
-   - ICE media transport has detected that the IP address has changed (via the keep-alive above)
+   - ICE media transport has detected that the IP address has changed (via the keep-alive above), and
    - the media was previously inactive, since if media has been active (hence ICE session is active), the SDP will contain only the used candidates and not all the list of candidates.
 
  Alternatively, '''we may not need to inform the new RTP/RTCP address at all'''. If the remote media endpoint has the capability to switch its RTP/RTCP transmission to the source address of the RTP/RTCP packets (note: PJMEDIA has this capability), then it should automatically switch its destination address to our new address.
+
+
+[[BR]]
+
+== Symbian specific issues == #sym
+
+=== Socket call get stucked after reconnecting to different access point (AP) ===
+Steps to reproduce:
+ 1. Create RConnection, call Start() to connect to AP
+ 1. Create UDP socket, call !SendTo() to send a packet
+ 1. Disconnect the AP (Menu -> Connectivity -> Conn. mgr. -> Active data connections -> (highlight the AP) -> Options (menu) -> Disconnect).
+ 1. Call udp.!SendTo() again
+ 1. AP selection dialog appears, select different AP
+ 1. !WaitForRequest() to the udp.!SendTo() operation now '''will get stuck for 1-2 minutes'''.
+ 1. Now if you call udp.!SendTo() again, now !WaitForRequest() will get stuck indefinitely
+
+The problem above does not occur if:
+ - the user selects the same AP. In this case the udp.!SendTo() should complete successfully
+ - the user cancels the AP selection dialog. In this case the udp.!SendTo() will fail immediately with KErrCancel without blocking the application.
+ - the socket is closed and re-opened. In this case the udp.!SendTo() should complete successfully
+
+The implication of above symptom is the library may get stucked in {{{pjsua_destroy()}}} when the application tries to destroy the stack when it detects that the AP connection is down. 
+
+Currently we don't have a solution for this, except to only use one AP (perhaps to select the AP when PJSIP is started and lock the RConnection that is assigned to PJLIB to this AP).