diff --git a/g3doc/sitemap.md b/g3doc/sitemap.md
index 297ac53..d7445c5 100644
--- a/g3doc/sitemap.md
+++ b/g3doc/sitemap.md
@@ -8,8 +8,9 @@
     * Network
       * [ICE](/p2p/g3doc/ice.md)
       * STUN
-      * DTLS
       * TURN
+      * DTLS
+      * [SCTP](/pc/g3doc/sctp_transport.md)
     *   Congestion control and bandwidth estimation
     *   Audio
       * AudioEngine
diff --git a/pc/g3doc/sctp_transport.md b/pc/g3doc/sctp_transport.md
new file mode 100644
index 0000000..254e264
--- /dev/null
+++ b/pc/g3doc/sctp_transport.md
@@ -0,0 +1,44 @@
+
+<?% config.freshness.reviewed = '2021-04-13' %?>
+<?% config.freshness.owner = 'hta' %?>
+
+# SctpTransport
+
+## webrtc::SctpTransport
+
+The [`webrtc::SctpTransport`](https://source.chromium.org/chromium/chromium/src/+/master:third_party/webrtc/pc/sctp_transport.h;l=33?q=class%20webrtc::SctpTransport) class encapsulates an SCTP association, and exposes a
+few properties of this association to the WebRTC user (such as Chrome).
+
+The SctpTransport is used to support Datachannels, as described in the [WebRTC
+specification for the Peer-to-peer Data
+API](https://w3c.github.io/webrtc-pc/#peer-to-peer-data-api).
+
+The public interface ([`webrtc::SctpTransportInterface`](https://source.chromium.org/chromium/chromium/src/+/master:third_party/webrtc/api/sctp_transport_interface.h?q=webrtc::SctpTransportInterface)) exposes an observer
+interface where the user can define a callback to be called whenever the state
+of an SctpTransport changes; this callback is called on the network thread (as
+set during PeerConnectionFactory initialization).
+
+The implementation of this object lives in pc/sctp_transport.{h,cc}, and is
+basically a wrapper around a `cricket::SctpTransportInternal`, hiding its
+implementation details and APIs that shoudldn't be accessed from the user.
+
+The `webrtc::SctpTransport` is a ref counted object; it should be regarded
+as owned by the PeerConnection, and will be closed when the PeerConnection
+closes, but the object itself may survive longer than the PeerConnection.
+
+## cricket::SctpTransportInternal
+
+[`cricket::SctpTransportInternal`](https://source.chromium.org/chromium/chromium/src/+/master:third_party/webrtc/media/sctp/sctp_transport_internal.h?q=cricket::SctpTransportInternal) owns two objects: The SCTP association object (currently
+implemented by wrapping the usrsctp library) and the DTLS transport, which is
+the object used to send and receive messages as emitted from or consumed by the
+usrsctp library.
+
+It communicates state changes and events using sigslot.
+
+See header files for details.
+
+
+
+
+
+