OSI Data Link Layer Flashcards
What are the two common LAN sublayers?
Logical Link Control (LLC) and Media Access Control (MAC)
What is the role of the data link layer in data transmission?
To prepare data for transmission on network media
What does LLC (Logical Link Control) do?
Places information in the frame that identifies which network layer protocol is being used for the frame
What is the MAC (Media Access Control) method?
The technique used for getting the frame on and off media
Which device usually processes the frame at each hop along the path?
A router
What is the data link layer responsible for?
The exchange of frames between nodes over the media of a physical network
What is the purpose of encapsulating packets into frames?
To facilitate media access
What organizations define open standards and protocols that apply to the data link layer?
International Organization for Standardization (ISO), Institute of Electrical and Electronics Engineers (IEEE), American National Standards Institute (ANSI), International Telecommunication Union (ITU)
What organization is responsible for defining open standards and protocols related to the data link layer?
International Organization for Standardization (ISO)
Institute of Electrical and Electronics Engineers (IEEE)
American National Standards Institute (ANSI)
What is the role of the data link layer in data transmission?
To prepare data for transmission on network media
What are the two common LAN sublayers?
Logical Link Control (LLC) and Media Access Control (MAC)
What does LLC do?
Places information in the frame that identifies which network layer protocol is being used for the frame
What is the MAC method?
The technique used for getting the frame on and off media
Which device usually processes the frame at each hop along the path?
A router
What is the purpose of encapsulating packets into frames?
To facilitate media access
Which organizations define open standards and protocols that apply to the data link layer?
International Organization for Standardization (ISO), Institute of Electrical and Electronics Engineers (IEEE), American National Standards Institute (ANSI), International Telecommunication Union (ITU)
What are the three elements of data link layer frame?
- Data
- Header
- Trailer
It is an Ethernet that is inserted into the bus system of the computer and makes the connection between running software processes on the computer and the physical media.
Network Interface Card (NIC)
What is contained within the frame header?
Start of Frame field
What is CSMA?
A media access method used in multiaccess topology
What is CSMA/CD?
A method for resolving media contention in shared media and the device monitors the media for the presence of data signal
What is the purpose of the trailer?
To check for errors
What is the purpose of PPP authentication?
To authenticate the nodes on each end of the PPP link
What are the three functions and subfunctions of an 802.11 frame?
control, data, and management
What is the purpose of MAC addressing?
To specify the frame destination node on the local network
What is the purpose of the FCS field in a PPP frame?
to provide improved error detection
What is the binary sequence for the flag field in a PPP frame?
01111110
What is the difference between scheduled access and nondeterministic access in shared media?
Scheduled access takes turns for devices to access the medium, while nondeterministic access first detects whether the media is carrying a signal before allowing any device to try to access it
What is the purpose of addressing in the data link layer?
To specify the frame destination node on the local network
What is the difference between CSMA/CD and CSMA/CA?
CSMA/CD monitors the media for the presence of a data signal, while CSMA/CA examines the media for the presence of a data signal
What is the purpose of the Protocol Version field in an 802.11 frame?
to indicate the version of 802.11 frame in use
What is the purpose of the Frame Check Sequence (FCS) field?
To check for errors
What is the purpose of the Authentication option in PPP?
To require the nodes on each end of the PPP link to authenticate in order to establish communications over a point-to-point link
What is the difference between logical and physical topology in a network?
Physical topology refers to the physical arrangement of nodes and connections, while logical topology refers to the way a network transfers frames from one node to the next
What is the purpose of the Stop field in the frame trailer?
To indicate the end of the frame
What is the difference between physical and logical addresses in the data link layer?
Physical addresses are contained within the frame header, while logical addresses are used only for local delivery.
What is the standard PPP broadcast address?
a single byte that contains the standard PPP broadcast address
What is a ring topology?
A topology in which each node in turn receives a frame
What is the purpose of the To DS field in an 802.11 frame?
To identify frames destined for the distribution system (devices in the wireless structure)
What is the purpose of the Sequence Number field in an 802.11 frame?
To indicate the sequence number assigned to the frame; retransmitted frames are identified by duplicate sequence numbers
What options can be negotiated in a PPP session?
Compression
Authentication
Multilink
What is the purpose of the Preamble field in Ethernet frames?
To indicate the beginning of the frame
What is the difference between controlled access and contention-based access in shared media?
Controlled access takes turns for devices to access the medium, while contention-based access first detects whether the media is carrying a signal before allowing any device to try to access it
What is a point-to-point topology?
A topology that connects two nodes directly
What is the purpose of the Power Management field in an 802.11 frame?
to indicate that a node will be in power-save mode
What is the purpose of the frame header?
To contain the control information specified by the data link layer protocol
