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The switches the we'll spend so much time with later in the course operate at Layer 2. Wireless Access Points (WAPs) also operate at this layer - more on WAPs in the Wireless section. Devices that you may well be using right now to access the Internet, cable modems and DSL modems, also run at L2,
We've got four major specifications that run here, some of which you may already be familiar with :
- Ethernet
- High Data link Control ( HDLC )
- Point-to-Point Protocol ( PPP )
- Frame Relay
A very important distinction : The data link layer does perform error detection through something called the Frame Check Sequence, but this layer does not perform error recovery.
The Data Link Layer is generally referred to as Layer 2, and MAC addresses as Layer 2 addresses. If you're not familiar with MAC addresses, they will be discussed in more detail in the Ethernet and LAN Switching section.
Another name for the MAC address is a little misleading, so let's nail this down. MAC addresses are sometimes called hardware addresses and physical addresses. That's because a MAC address is physically burned into the Network Interface Card (NIC), which leads to another name for this address - a burned-in address (BIA).
What's the misleading part? Remember that physical addresses are not used at the Physical Layer of the OSI model - they're Data Link layer address. That's right - a physical address is used to deliver a frame, but not a physical layer address.
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The switches the we'll spend so much time with later in the course operate at Layer 2. Wireless Access Points (WAPs) also operate at this layer - more on WAPs in the Wireless section. Devices that you may well be using right now to access the Internet, cable modems and DSL modems, also run at L2,
We've got four major specifications that run here, some of which you may already be familiar with :
- Ethernet
- High Data link Control ( HDLC )
- Point-to-Point Protocol ( PPP )
- Frame Relay
A very important distinction : The data link layer does perform error detection through something called the Frame Check Sequence, but this layer does not perform error recovery.
The Data Link Layer is generally referred to as Layer 2, and MAC addresses as Layer 2 addresses. If you're not familiar with MAC addresses, they will be discussed in more detail in the Ethernet and LAN Switching section.
Another name for the MAC address is a little misleading, so let's nail this down. MAC addresses are sometimes called hardware addresses and physical addresses. That's because a MAC address is physically burned into the Network Interface Card (NIC), which leads to another name for this address - a burned-in address (BIA).
What's the misleading part? Remember that physical addresses are not used at the Physical Layer of the OSI model - they're Data Link layer address. That's right - a physical address is used to deliver a frame, but not a physical layer address.
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