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+---
+title: Link_Layer_of_the_Internet_Protocol
+tags: []
+created: Tuesday, August 06, 2024
+---
+
+# Link Layer of the Internet Protocol Suite
+
+> The Link Layer is the lowest level of the network stack that makes up the
+> Internet Protocol Suite. It is concerned with the physical and logical
+> connections between [hosts](./Network_hosts.md) on the same local network.
+
+The physical and logical connections are known as **Links**.
+
+Link Layer protocols goven communication between devices. Examples include:
+
+- **WiFi**
+  - For wireless communication between devices using radio waves
+- **Ethernet**
+  - Wired communication
+
+## 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.
+
+A device receives data addressed to its MAC address.
+
+MAC addresses are limited to local networks. Remote networks cannot send data to
+a specific MAC address. This is off-limits from the outside.
+
+## Frames
+
+Link Layer data is divided into small units called "frames". The anatomy of a
+frame is as follows:
+
+```
+--------------------------
+| header | data | footer |
+--------------------------
+```
+
+The header contains the source and destination MAC address plus a descriptor of
+the type of data it contains. The data is the payload. The footer is used to
+detect errors.
diff --git a/zk/MAC_addresses.md b/zk/MAC_addresses.md
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+---
+title: MAC_addresses
+tags: [networks]
+created: Tuesday, August 06, 2024
+---
+
+# MAC addresses
+
+A Media Access Control (MAC) address is a physical address in contrast to, say,
+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 hardware-based and the addresses are typically
+burned into the network card by the manufacturer, making them a physical
+attribute of the device.
+
+MAC addresses consist of 6 bytes (48-bits) represented as 12
+[hexadecimal_digits](Hexadecimal_number_system.md)
diff --git a/zk/Network_hosts.md b/zk/Network_hosts.md
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+++ b/zk/Network_hosts.md
@@ -7,7 +7,7 @@ created: Saturday, August 03, 2024
 # Network_hosts
 
 A network **host** or **node** is a single computing device attached to a
-![network](Network_fundamentals.md).
+![network](Network_fundamentals.md)
 
 Hosts can act as servers or clients, or both.