fix: Add missing documentation for RTCSessionDescriptionInit, RTCLoca…

…lSessionDescriptionInit

Add missing documentation for RTCSessionDescriptionInit,
RTCLocalSessionDescriptionInit interfaces. Also correct several links
referencing those interfaces. Also add a clear explanation of the
relationship between RTCSessionDescription, RTCSessionDescriptionInit,
and RTCLocalSessionDescriptionInit interfaces.

Fixes mdn#33962

files/en-us/web/api/rtclocalsessiondescriptioninit/index.md

@@ -0,0 +1,29 @@
+---
+title: RTCLocalSessionDescriptionInit
+slug: Web/API/RTCLocalSessionDescriptionInit
+page-type: web-api-interface
+browser-compat: api.RTCSessionDescription
+---
+
+{{APIRef("WebRTC")}}
+
+The **`RTCLocalSessionDescriptionInit`** dictionary is used to provide {{Glossary("SDP")}} values in {{domxref("RTCPeerConnection.setLocalDescription")}}. Especially, empty object(`{}`) conforms the `RTCLocalSessionDescriptionInit` dictionary.
+
+### Properties
+
+- `type`
+  - : A string which is used to set the `type` property of the new `RTCSessionDescription` object. For more information, see documentation for the {{domxref("RTCSessionDescription.type")}} property.
+- `sdp`
+  - : A string containing the {{Glossary("SDP")}} describing the session. If `type` is `"rollback"`, this member is unused.
+
+
+## Specifications
+
+https://w3c.github.io/webrtc-pc/#dom-rtclocalsessiondescriptioninit
+
+## See also
+
+- [WebRTC](/en-US/docs/Web/API/WebRTC_API)
+- {{domxref("RTCSessionDescription")}}
+- {{domxref("RTCSessionDescriptionInit")}}
+- {{domxref("RTCPeerConnection.setLocalDescription")}}

files/en-us/web/api/rtcpeerconnection/createoffer/index.md

@@ -57,7 +57,7 @@ The parameters for the older form of `createOffer()` are described below, to aid
 
 ### Return value
 
-A {{jsxref("Promise")}} whose fulfillment handler will receive an object conforming to the [RTCSessionDescriptionInit](/en-US/docs/Web/API/RTCSessionDescription/RTCSessionDescription#rtcsessiondescriptioninit) dictionary which contains the SDP describing the generated offer.
+A {{jsxref("Promise")}} whose fulfillment handler will receive an object conforming to the {{domxref("RTCSessionDescriptionInit")}} dictionary which contains the SDP describing the generated offer.
 That received offer should be delivered through the signaling server to a remote peer.
 
 ### Exceptions
@@ -98,7 +98,7 @@ myPeerConnection
   });
 ```
 
-In this code, the offer is created, and once successful, the local end of the {{domxref("RTCPeerConnection")}} is configured to match by passing the offer (which is represented using an object conforming to [RTCSessionDescriptionInit](/en-US/docs/Web/API/RTCSessionDescription/RTCSessionDescription#rtcsessiondescriptioninit)) into {{domxref("RTCPeerConnection.setLocalDescription", "setLocalDescription()")}}.
+In this code, the offer is created, and once successful, the local end of the {{domxref("RTCPeerConnection")}} is configured to match by passing the offer (which is represented using an object conforming to {{domxref("RTCSessionDescriptionInit")}} into {{domxref("RTCPeerConnection.setLocalDescription", "setLocalDescription()")}}.
 Once that's done, the offer is sent to the remote system over the signaling channel; in this case, by using a custom function called `sendToServer()`.
 The implementation of the signaling server is independent from the WebRTC specification, so it doesn't matter how the offer is sent as long as both the caller and potential receiver are using the same one.
 

files/en-us/web/api/rtcpeerconnection/setlocaldescription/index.md

@@ -28,7 +28,7 @@ setLocalDescription(sessionDescription, successCallback, errorCallback) // depre
 ### Parameters
 
 - `sessionDescription` {{optional_inline}}
-  - : An {{domxref("RTCSessionDescriptionInit")}} or {{domxref("RTCSessionDescription")}} which specifies the configuration to be applied to the local end of the connection.
+  - : An {{domxref("RTCLocalSessionDescriptionInit")}} or {{domxref("RTCSessionDescription")}} which specifies the configuration to be applied to the local end of the connection.
     If the description is omitted, the WebRTC runtime tries to automatically do the right thing.
 
 ### Return value
@@ -47,7 +47,7 @@ Otherwise, `setLocalDescription()` creates an answer, which becomes the new loca
 
 #### Type of the description parameter
 
-The description is of type `RTCSessionDescriptionInit`, which is a serialized version of a {{domxref("RTCSessionDescription")}} browser object. They're interchangeable:
+The description is of type `RTCLocalSessionDescriptionInit`, which is a serialized version of a {{domxref("RTCSessionDescription")}} browser object. They're interchangeable:
 
 ```js
 myPeerConnection
@@ -90,7 +90,7 @@ When using the deprecated callback-based version of `setLocalDescription()`, the
 - `InvalidStateError` {{domxref("DOMException")}} {{deprecated_inline}}
   - : Thrown if the connection's {{domxref("RTCPeerConnection.signalingState", "signalingState")}} is `"closed"`, indicating that the connection is not currently open, so negotiation cannot take place.
 - `InvalidSessionDescriptionError` {{domxref("DOMException")}} {{deprecated_inline}}
-  - : Thrown if the {{domxref("RTCSessionDescription")}} specified by the `sessionDescription` parameter is invalid.
+  - : Thrown if the {{domxref("RTCLocalSessionDescriptionInit")}} specified by the `sessionDescription` parameter is invalid.
 
 ## Examples
 
@@ -140,3 +140,4 @@ called `signalRemotePeer()`.
 ## See also
 
 - [WebRTC API](/en-US/docs/Web/API/WebRTC_API)
+- {{domxref("RTCLocalSessionDescriptionInit")}}

files/en-us/web/api/rtcpeerconnection/setremotedescription/index.md

@@ -124,7 +124,7 @@ When using the deprecated callback-based version of `setRemoteDescription()`, th
 - `InvalidStateError` {{deprecated_inline}}
   - : The connection's {{domxref("RTCPeerConnection.signalingState", "signalingState")}} is `"closed"`, indicating that the connection is not currently open, so negotiation cannot take place.
 - `InvalidSessionDescriptionError` {{deprecated_inline}}
-  - : The {{domxref("RTCSessionDescription")}} specified by the `sessionDescription` parameter is invalid.
+  - : The {{domxref("RTCSessionDescriptionInit")}} specified by the `sessionDescription` parameter is invalid.
 
 ## Examples
 
@@ -168,4 +168,5 @@ When our promise fulfillment handler is called, indicating that this has been do
 - [WebRTC](/en-US/docs/Web/API/WebRTC_API)
 - {{domxref("RTCPeerConnection.remoteDescription")}},
   {{domxref("RTCPeerConnection.pendingRemoteDescription")}},
-  {{domxref("RTCPeerConnection.currentRemoteDescription")}}
+  {{domxref("RTCPeerConnection.currentRemoteDescription")}} 
+- {{domxref("RTCSessionDescriptionInit")}}

files/en-us/web/api/rtcsessiondescription/index.md

@@ -25,7 +25,7 @@ _The `RTCSessionDescription` interface doesn't inherit any properties._
 _The `RTCSessionDescription` doesn't inherit any methods._
 
 - {{domxref("RTCSessionDescription.RTCSessionDescription", "RTCSessionDescription()")}} {{deprecated_inline}}
-  - : This constructor returns a new `RTCSessionDescription`. The parameter is a `RTCSessionDescriptionInit` dictionary containing the values to assign the two properties.
+  - : This constructor returns a new `RTCSessionDescription`. The parameter is a {{domxref("RTCSessionDescriptionInit")}} dictionary containing the values to assign the two properties.
 - {{domxref("RTCSessionDescription.toJSON()")}}
   - : Returns a {{Glossary("JSON")}} description of the object. The values of both properties, {{domxref("RTCSessionDescription.type", "type")}} and {{domxref("RTCSessionDescription.sdp", "sdp")}}, are contained in the generated JSON.
 
@@ -57,6 +57,16 @@ signalingChannel.onmessage = (evt) => {
 };
 ```
 
+## RTCSessionDescription, RTCSessionDescriptionInit, and RTCLocalSessionDescriptionInit
+
+There are other similar interfaces that are used to provide the SDP values for `RTCSessionDescription` objects. These are:
+- {{domxref("RTCSessionDescriptionInit")}}
+- {{domxref("RTCLocalSessionDescriptionInit")}}
+
+These interfaces are used in several methods of the {{domxref("RTCPeerConnection")}} interface utilize these interfaces, including {{domxref("RTCPeerConnection.createOffer")}}, {{domxref("RTCPeerConnection.createAnswer")}}, {{domxref("RTCPeerConnection.setLocalDescription")}}, and {{domxref("RTCPeerConnection.setRemoteDescription")}}.
+
+In essence, `RTCSessionDescriptionInit` and `RTCLocalSessionDescriptionInit` are defined as dictionaries, enabling users to provide necessary values without creating a full `RTCSessionDescription` object. Also, `RTCPeerConnection.setLocalDescription()` accepts `RTCLocalSessionDescriptionInit` as an argument, allowing users to omit this argument altogether. This eliminates the need for separate calls to `RTCPeerConnection.createOffer()` and `RTCPeerConnection.setLocalDescription()`. (For more information, see [Implicit description in RTCPeerConnection.setLocalDescription()](/en-US/docs/Web/API/RTCPeerConnection/setLocalDescription#implicit_description)).
+
 ## Specifications
 
 {{Specifications}}
@@ -69,3 +79,5 @@ signalingChannel.onmessage = (evt) => {
 
 - [WebRTC](/en-US/docs/Web/API/WebRTC_API)
 - {{domxref("RTCPeerConnection.setLocalDescription()")}} and {{domxref("RTCPeerConnection.setRemoteDescription()")}}
+- {{domxref("RTCSessionDescriptionInit")}}
+- {{domxref("RTCLocalSessionDescriptionInit")}}

files/en-us/web/api/rtcsessiondescription/rtcsessiondescription/index.md

@@ -17,7 +17,7 @@ specified object.
 > **Note:** This constructor has been deprecated because
 > {{domxref("RTCPeerConnection.setLocalDescription()")}} and other methods which take
 > SDP as input now directly accept an object conforming to the
-> `RTCSessionDescriptionInit` dictionary, so you don't have to instantiate an
+> {{domxref("RTCSessionDescriptionInit")}} dictionary, so you don't have to instantiate an
 > `RTCSessionDescription` yourself.
 
 ## Syntax
@@ -31,7 +31,7 @@ new RTCSessionDescription(options)
 - `options` {{optional_inline}}
 
   - : An object providing the default values for the session description; the object
-    conforms to the `RTCSessionDescriptionInit` dictionary. That dictionary has
+    conforms to the {{domxref("RTCSessionDescriptionInit")}} dictionary. That dictionary has
     the following properties:
 
     - `type`

files/en-us/web/api/rtcsessiondescriptioninit/index.md

@@ -0,0 +1,30 @@
+---
+title: RTCSessionDescriptionInit
+slug: Web/API/RTCSessionDescriptionInit
+page-type: web-api-interface
+browser-compat: api.RTCSessionDescription
+---
+
+{{APIRef("WebRTC")}}
+
+The **`RTCSessionDescriptionInit`** dictionary is used to provide {{Glossary("SDP")}} values in several methods of the {{domxref("RTCPeerConnection")}} interface, such as {{domxref("RTCPeerConnection.createOffer")}}, {{domxref("RTCPeerConnection.createAnswer")}}, and {{domxref("RTCPeerConnection.setRemoteDescription")}}. Also it can be used to create new `RTCSessionDescription` objects, though this is less common.
+
+### Properties
+
+- `type`
+  - : A string which is used to set the `type` property of the new `RTCSessionDescription` object. This is a required property. For more information, see documentation for the {{domxref("RTCSessionDescription.type")}} property.
+- `sdp`
+  - : A string containing the {{Glossary("SDP")}} describing the session. If `type` is `"rollback"`, this member is unused.
+
+## Specifications
+
+https://w3c.github.io/webrtc-pc/#dom-rtcsessiondescriptioninit
+
+## See also
+
+- [WebRTC](/en-US/docs/Web/API/WebRTC_API)
+- {{domxref("RTCSessionDescription")}}
+- {{domxref("RTCLocalSessionDescriptionInit")}}
+- {{domxref("RTCPeerConnection.createOffer")}}
+- {{domxref("RTCPeerConnection.createAnswer")}}
+- {{domxref("RTCPeerConnection.setRemoteDescription")}}