diff --git a/School/Analyse/OSI Model.md b/School/Analyse/OSI Model.md
index 9bd2c7f..f96427f 100644
--- a/School/Analyse/OSI Model.md	
+++ b/School/Analyse/OSI Model.md	
@@ -43,9 +43,17 @@ Also when sending of receiving data we sometimes want to compress the data so th
 ## 5. Session Layer
 The session layer is responsible for opening and closing connections between two devices. The duration of a connection is called the session.
 
-The session layer ensures that the connections remains active and open so that the data being received and/or send is complete. For example whe
+The session layer ensures that the connections remains active and open so that the data being received and/or send is complete. 
+
+For example when sending a big file to someone, which takes some time, the session layer will keep the connection open long enough to send the complete file.
+
+The session layer also synchronizes the data transfer with checkpoints. For example, if a 50 MB file is send to a device, the session layer could set a checkpoint every 10 MB. In case of a disconnect (session close), the session could be restored to a certain checkpoint and the data transfer can resume where it disconnected. 
+
+This way we do not need to completely resend the file. 
 
 ## 4. Transport Layer
+
+
 ## 3. Network Layer
 ## 2. Data Link Layer
 ## 1.  Physical Layer
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