diff --git a/CHANGES b/CHANGES
index c2fd95a339..d7c1c904e8 100644
--- a/CHANGES
+++ b/CHANGES
@@ -33,6 +33,14 @@ SIP Changes
  * Added two new configuration options, "qualifygap" and "qualifypeers", which allow
    finer control over how many peers Asterisk will qualify and the gap between them
    when all peers need to be qualified at the same time.
+ * Added a new 'ignoresdpversion' option to sip.conf.  When this is enabled
+   (either globally or for a specific peer), chan_sip will treat any SDP data
+   it receives as new data and update the media stream accordingly.  By
+   default, Asterisk will only modify the media stream if the SDP session
+   version received is different from the current SDP session version.  This
+   option is required to interoperate with devices that have non-standard SDP
+   session version implementations (observed with Microsoft OCS).  This option
+   is diabled by default.
 
 Skinny Changes
 --------------
diff --git a/channels/chan_sip.c b/channels/chan_sip.c
index a216316231..46e7958c0e 100644
--- a/channels/chan_sip.c
+++ b/channels/chan_sip.c
@@ -1328,6 +1328,7 @@ struct sip_auth {
 #define SIP_PAGE2_ALLOWSUBSCRIBE	(1 << 16)	/*!< GP: Allow subscriptions from this peer? */
 #define SIP_PAGE2_ALLOWOVERLAP		(1 << 17)	/*!< DP: Allow overlap dialing ? */
 #define SIP_PAGE2_SUBSCRIBEMWIONLY	(1 << 18)	/*!< GP: Only issue MWI notification if subscribed to */
+#define SIP_PAGE2_IGNORESDPVERSION	(1 << 19)	/*!< GDP: Ignore the SDP session version number we receive and treat all sessions as new */
 
 #define SIP_PAGE2_T38SUPPORT		(7 << 20)	/*!< GDP: T38 Fax Passthrough Support */
 #define SIP_PAGE2_T38SUPPORT_UDPTL	(1 << 20)	/*!< GDP: T38 Fax Passthrough Support */
@@ -1348,10 +1349,10 @@ struct sip_auth {
 #define SIP_PAGE2_VIDEOSUPPORT_ALWAYS	(1 << 31)       /*!< DP: Always set up video, even if endpoints don't support it */
 
 #define SIP_PAGE2_FLAGS_TO_COPY \
-	(SIP_PAGE2_ALLOWSUBSCRIBE | SIP_PAGE2_ALLOWOVERLAP | SIP_PAGE2_VIDEOSUPPORT | \
-	SIP_PAGE2_T38SUPPORT | SIP_PAGE2_RFC2833_COMPENSATE | SIP_PAGE2_BUGGY_MWI | \
-	SIP_PAGE2_TEXTSUPPORT | SIP_PAGE2_FAX_DETECT | SIP_PAGE2_UDPTL_DESTINATION | \
-	SIP_PAGE2_VIDEOSUPPORT_ALWAYS)
+	(SIP_PAGE2_ALLOWSUBSCRIBE | SIP_PAGE2_ALLOWOVERLAP | SIP_PAGE2_IGNORESDPVERSION | \
+	SIP_PAGE2_VIDEOSUPPORT | SIP_PAGE2_T38SUPPORT | SIP_PAGE2_RFC2833_COMPENSATE | \
+	SIP_PAGE2_BUGGY_MWI | SIP_PAGE2_TEXTSUPPORT | SIP_PAGE2_FAX_DETECT | \
+	SIP_PAGE2_UDPTL_DESTINATION | SIP_PAGE2_VIDEOSUPPORT_ALWAYS)
 
 /*@}*/ 
 
@@ -7341,8 +7342,11 @@ static int process_sdp(struct sip_pvt *p, struct sip_request *req, int t38action
 		return -1;
 	}
 
-	if (p->sessionversion_remote < 0 || p->sessionversion_remote != rua_version) {
- 		p->sessionversion_remote = rua_version;
+	if (ast_test_flag(&p->flags[1], SIP_PAGE2_IGNORESDPVERSION)
+		|| p->sessionversion_remote < 0
+		|| p->sessionversion_remote != rua_version) {
+ 		
+		p->sessionversion_remote = rua_version;
 		p->session_modify = TRUE;
 	} else if (p->sessionversion_remote == rua_version) {
 		p->session_modify = FALSE;
@@ -14056,6 +14060,7 @@ static char *_sip_show_peer(int type, int fd, struct mansession *s, const struct
 		ast_cli(fd, "  User=Phone   : %s\n", cli_yesno(ast_test_flag(&peer->flags[0], SIP_USEREQPHONE)));
 		ast_cli(fd, "  Video Support: %s\n", cli_yesno(ast_test_flag(&peer->flags[1], SIP_PAGE2_VIDEOSUPPORT)));
 		ast_cli(fd, "  Text Support : %s\n", cli_yesno(ast_test_flag(&peer->flags[1], SIP_PAGE2_TEXTSUPPORT)));
+		ast_cli(fd, "  Ign SDP ver  : %s\n", cli_yesno(ast_test_flag(&peer->flags[1], SIP_PAGE2_IGNORESDPVERSION)));
 		ast_cli(fd, "  Trust RPID   : %s\n", cli_yesno(ast_test_flag(&peer->flags[0], SIP_TRUSTRPID)));
 		ast_cli(fd, "  Send RPID    : %s\n", cli_yesno(ast_test_flag(&peer->flags[0], SIP_SENDRPID)));
 		ast_cli(fd, "  Subscriptions: %s\n", cli_yesno(ast_test_flag(&peer->flags[1], SIP_PAGE2_ALLOWSUBSCRIBE)));
@@ -14459,6 +14464,7 @@ static char *sip_show_settings(struct ast_cli_entry *e, int cmd, struct ast_cli_
 	}
 	ast_cli(a->fd, "  Videosupport:           %s\n", cli_yesno(ast_test_flag(&global_flags[1], SIP_PAGE2_VIDEOSUPPORT)));
 	ast_cli(a->fd, "  Textsupport:            %s\n", cli_yesno(ast_test_flag(&global_flags[1], SIP_PAGE2_TEXTSUPPORT)));
+	ast_cli(a->fd, "  Ignore SDP sess. ver.:  %s\n", cli_yesno(ast_test_flag(&global_flags[1], SIP_PAGE2_IGNORESDPVERSION)));
 	ast_cli(a->fd, "  AutoCreate Peer:        %s\n", cli_yesno(sip_cfg.autocreatepeer));
 	ast_cli(a->fd, "  Match Auth Username:    %s\n", cli_yesno(global_match_auth_username));
 	ast_cli(a->fd, "  Allow unknown access:   %s\n", cli_yesno(sip_cfg.allowguest));
@@ -21583,6 +21589,9 @@ static int handle_common_options(struct ast_flags *flags, struct ast_flags *mask
 	} else if (!strcasecmp(v->name, "allowsubscribe")) {
 		ast_set_flag(&mask[1], SIP_PAGE2_ALLOWSUBSCRIBE);
 		ast_set2_flag(&flags[1], ast_true(v->value), SIP_PAGE2_ALLOWSUBSCRIBE);
+	} else if (!strcasecmp(v->name, "ignoresdpversion")) {
+		ast_set_flag(&mask[1], SIP_PAGE2_IGNORESDPVERSION);
+		ast_set2_flag(&flags[1], ast_true(v->value), SIP_PAGE2_IGNORESDPVERSION);
 	} else if (!strcasecmp(v->name, "faxdetect")) {
 		ast_set_flag(&mask[1], SIP_PAGE2_FAX_DETECT);
 		ast_set2_flag(&flags[1], ast_true(v->value), SIP_PAGE2_FAX_DETECT);
@@ -22594,6 +22603,7 @@ static int reload_config(enum channelreloadreason reason)
 	ast_clear_flag(&global_flags[1], SIP_PAGE2_FAX_DETECT);
 	ast_clear_flag(&global_flags[1], SIP_PAGE2_VIDEOSUPPORT | SIP_PAGE2_VIDEOSUPPORT_ALWAYS);
 	ast_clear_flag(&global_flags[1], SIP_PAGE2_TEXTSUPPORT);
+	ast_clear_flag(&global_flags[1], SIP_PAGE2_IGNORESDPVERSION);
 
 
 	/* Read the [general] config section of sip.conf (or from realtime config) */
diff --git a/configs/sip.conf.sample b/configs/sip.conf.sample
index a3b0570da8..42bb57f8e2 100644
--- a/configs/sip.conf.sample
+++ b/configs/sip.conf.sample
@@ -589,6 +589,15 @@ srvlookup=yes                   ; Enable DNS SRV lookups on outbound calls
                                 ; instead of INVITE. This can be combined with 'nonat', as
                                 ; 'canreinvite=update,nonat'. It implies 'yes'.
 
+;ignoresdpversion=yes           ; By default, Asterisk will honor the session version
+                                ; number in SDP packets and will only modify the SDP
+                                ; session if the version number changes. This option will
+                                ; force asterisk to ignore the SDP session version number
+                                ; and treat all SDP data as new data.  This is required
+                                ; for devices that send us non standard SDP packets
+                                ; (observed with Microsoft OCS). By default this option is
+                                ; off.
+
 ;----------------------------------------- REALTIME SUPPORT ------------------------
 ; For additional information on ARA, the Asterisk Realtime Architecture,
 ; please read realtime.txt and extconfig.txt in the /doc directory of the
@@ -763,6 +772,7 @@ srvlookup=yes                   ; Enable DNS SRV lookups on outbound calls
 ; allowoverlap
 ; allowsubscribe
 ; allowtransfer
+; ignoresdpversion
 ; subscribecontext
 ; template
 ; videosupport