OSI Data Link Layer Flashcards
- Allows the upper layers to access the media using techniques such as framing.
- Controls how data is placed onto the media and is received from the media using techniques such as media access control (MAC) and error detection.
Data Link Layer 2 Basic Services
Data Link Layer 2 Basic Services
- Allows the upper layers to access the media using techniques such as framing.
- Controls how data is placed onto the media and is received from the media using techniques such as media access control (MAC) and error detection.
At each hop the received frame is examined for errors, if an error is found in a frame, then the frame is ____
Discarded
The technique used for getting the frame on and off media is called_____
the media access method or MAC Method
Control information can describe the following
- Which nodes are in communication with each other
- When communication between individual nodes begins and ends
- If errors occurred while the nodes communicated
- Which nodes will communicate next
The data link layer frame includes the following elements:
Data, Header, Trailer
The packet from the network layer
____ link layer addressing is contained within the frame header and specifies the frame destination node on the local network.
Data
The control information, such as addressing, located at the beginning of the PDU
The frame ____ contains the control information specified by the data link layer protocol for the specific logical topology and media used.
Header
The control information added to the end of the PDU
Data link layer protocols add a ____ to the end of each frame.
Trailer
Typical field types include:
- Start and Stop Indicator Fields
- Addressing or naming fields
- Type fields
- Quality
- Data Field
The beginning and end limits of the frame
Start and stop indicator fields
The destination and/or source devices
Addressing or naming fields
The type of PDU contained in the frame
Type field
The control fields
Quality
The frame payload (network layer packet)
Data field
the data link layer is embodied as a physical entity, such as an Ethernet ______, which inserts into the system bus of a computer and makes the connection between running software processes on the computer and the physical media.
network interface card (NIC)
The two common LAN sublayers are as follows:
Logical Link Control (LLC)
MAC
places information in the frame that identifies which network layer protocol is being used for the frame.
Logical Link Control (LLC)
provides data link layer addressing and delimiting of data according to the physical signalling requirements of the medium and the type of data link layer protocol in use.
MAC
Engineering organisations that define open standards and protocols that apply to the data link layer include:
- International Organisation for Standardisation
- Institute of Electrical and Electronics Engineers (IEEE)
- American National Standards Institute (ANSI)
- International Telecommunication Union (ITU)
- Network devices take turns, in sequence, to access the
medium. - Also known as scheduled access or deterministic
Controlled Access for Shared Media
- Allow any device to try to access the medium whenever it
has data to send. - Sometimes referred to as nondeterministic
Contention-Based Access for Shared Media
in Contention-Based Access, Uses a _____ process
to first detect whether the media is carrying a signal
carrier sense multiple access (CSMA)
CSMA is usually implemented in conjunction with a method for resolving the media contention.
The two commonly used methods are:
CSMA/Collision Detect (CSMA/CD)
CSMA/Collision Avoid (CSMA/CA)
The device monitors the media for the presence of a data signal.
CSMA/Collision Detect (CSMA/CD)
The device examines the media for the presence of a data signal.
CSMA/Collision Avoid (CSMA/CA)
In a _____, the nodes do not have to
share the media with other hosts or determine whether
a frame is destined for that node.
point-to-point topology
In _______, Ethernet has established
arbitration rules for resolving conflicts arising from
instances when more than one station attempts to
transmit at the same time.
half-duplex communication
In ____, both devices can transmit
and receive on the media at the same time.
full-duplex communication
The ____ is an arrangement of the nodes and the physical connections between them.
physical topology
A_____ is the way a network transfers frames from one node to the next.
logical topology
The logical and physical topologies typically used in networks:
- Point-to-point
- Multiaccess
- Ring
- Connects two nodes directly.
- MAC protocol can be very simple.
- All frames on the media can only travel to or from the two nodes.
Point-to-Point Topology
- Enables a number of nodes to communicate by using the same shared media.
- The MAC methods used are CSMA/CD or CSMA/CA.
Multiaccess Topology
- Each node in turn receives a frame.
- Uses a controlled MAC technique called token passing.
Ring Topology
3 Parts of a Frame in Data Link Layer Protocols
Header, Data, Trailer