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diff --git a/zk/Internet_Layer_of_Internet_Protocol.md b/zk/Internet_Layer_of_Internet_Protocol.md
new file mode 100644
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@@ -0,0 +1,10 @@
+---
+title: Internet_Layer_of_Internet_Protocol
+tags: []
+created: Thursday, August 15, 2024 
+---
+# Internet_Layer_of_Internet_Protocol
+
+
+
+
diff --git a/zk/Internet_fundamentals.md b/zk/Internet_fundamentals.md
index d9fe3af..f319423 100644
--- a/zk/Internet_fundamentals.md
+++ b/zk/Internet_fundamentals.md
@@ -27,10 +27,11 @@ protocols. From the top:
 
 ![TCP/IP stack diagram](../img/TCP_IP.png)
 
-- The **Link Layer** concerns communication between devices on the same local
-  network. The transfer of information once it has been received from the
-  internet or its transfer between devices before it sent out into the internet.
-  Ethernet and WiFi are two core protocols utilised at this layer.
+- The ![Link Layer](Link_Layer_of_Internet_Protocol.md) concerns communication
+  between devices on the same local network. The transfer of information once it
+  has been received from the internet or its transfer between devices before it
+  sent out into the internet. Ethernet and WiFi are two core protocols utilised
+  at this layer.
 
 - The **Internet Layer** is concerned with communication accross networks. It is
   responsible for identifying hosts on the inter-network by their addresses and
diff --git a/zk/Link_Layer_of_Internet_Protocol.md b/zk/Link_Layer_of_Internet_Protocol.md
index f996e23..721d03d 100644
--- a/zk/Link_Layer_of_Internet_Protocol.md
+++ b/zk/Link_Layer_of_Internet_Protocol.md
@@ -19,10 +19,19 @@ Link Layer protocols goven communication between devices. Examples include:
 - **Ethernet**
   - Wired communication
 
+All devices connected to the internet participate in the Link Layer since it is
+the base level and the gateway out of the local network to other networks. The
+same is not true for other layers. For example a device like a laptop
+participates in all four layers up to the Application Layer but a network router
+does not:
+
+![Link Layer diagram](../img/link-layer-internet-diagram.png)
+
 ## MAC addresses
 
 Each device on a link has a network address that uniquely identifies it. For
-most Link Layer Protocols this is a Media Access Control (MAC) address.
+most Link Layer Protocols this is a
+[Media Access Control (MAC) address](MAC_addresses.md).
 
 A device receives data addressed to its MAC address.
 
diff --git a/zk/MAC_addresses.md b/zk/MAC_addresses.md
index 2c2a822..bbbe763 100644
--- a/zk/MAC_addresses.md
+++ b/zk/MAC_addresses.md
@@ -12,7 +12,7 @@ an IP address which is logical.
 Each device on a [local network](./Link_Layer_of_Internet_Protocol.md) has a MAC
 as a unique identifier. It is a hardware-based, physical attribute of the
 device, typically permanently encoded onto a non-volatile memory chip attached
-to the network card.
+to the ![network_card](Network_card.md).
 
 MAC addresses consist of 6 bytes (48-bits) represented as 12
 [hexadecimal_digits](Hexadecimal_number_system.md).