data link layer Flashcards
What are the networking devices working on data link layer called?
A switch
What do switches use to determine correct port to transfer a frame to?
Destination MAC addresses
What’s the most common standard for wired LANs?
Ethernet
Describe the content of an ethernet frame.
Header, payload and trailer. Header has destination and source addresses and type. Payload is the data itself, usually an IP packet. Trailer has FCS (Frame Check sequence) for determining if the frame was damaged or not.
How long is MAC address and how is it written?
48 bits / 6 bytes, two hexadecimal digits divided with : or ~
What’s the function of a switch?
To quickly switch ethernet frames between different ports.
How can a switch know on which port to forward an incoming Ethernet frame?
There’s a destination MAC address in the header of an Ethernet frame. Switch stores MAC addresses in a MAC address table (stored locally on the switch) where known MAC addresses are linked to ports. If the destination MAC address is found on the table, the switch sends the packet out of the corresponding port. If its not on the table, the Ethernet frame is forwarded out of every port excluding the port it came in to.
How can layer 2 loops happen and how switches prevent them from happening?
When multiple switches are connected to each other, there is a possibility that frames are endlessly circulated between them. The switches use Spanning Tree Protocol to prevent loops from occuring.
What is duplex and half-duplex?
Duplex means that two connected devices can both send and recieve data on the shared link at the same time. Half-duplex means that when one device is sending, the other can only receive.
What are VLANs?
Virtual Local Area Networks
What are the benefits on using VLANs?
Smaller broadcast domains, Fewer users in networks, less traffic per network, easier management, enhanced security
What is the current Wi-Fi standard and what is the maximum transfer rate?
Wi-Fi 6 / 802.11ax, 10Gbps
