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What layer of the OSI model does Token Ring technology operate at?
What layer of the OSI model does Token Ring technology operate at?
Token Ring technology allows multiple tokens to circulate simultaneously on a 4 Mbit/s network.
Token Ring technology allows multiple tokens to circulate simultaneously on a 4 Mbit/s network.
False
What is the purpose of the token in Token Ring technology?
What is the purpose of the token in Token Ring technology?
To grant permission to transmit on the medium.
In Token Ring, when a workstation receives a message, it changes the token back to ___ before sending it again.
In Token Ring, when a workstation receives a message, it changes the token back to ___ before sending it again.
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Match the following Token Ring components with their functions:
Match the following Token Ring components with their functions:
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What happens to the token frame when a workstation needs to transmit data?
What happens to the token frame when a workstation needs to transmit data?
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The Token Ring protocol was initially used only by IBM computers.
The Token Ring protocol was initially used only by IBM computers.
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What happens to a data frame once the sending station receives its own data?
What happens to a data frame once the sending station receives its own data?
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What is the purpose of token priority in Token Ring networks?
What is the purpose of token priority in Token Ring networks?
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A data token frame is only used for transmitting data from upper-layer protocols.
A data token frame is only used for transmitting data from upper-layer protocols.
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How many priority levels are specified in Token Ring for token priority?
How many priority levels are specified in Token Ring for token priority?
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The Starting Delimiter consists of a special bit pattern denoting the ________ of the frame.
The Starting Delimiter consists of a special bit pattern denoting the ________ of the frame.
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Match the components of the Token Ring data/command frame with their descriptions:
Match the components of the Token Ring data/command frame with their descriptions:
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What does the T bit indicate when set in a frame?
What does the T bit indicate when set in a frame?
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What does the Access Control byte in a Token Ring data/command frame consist of?
What does the Access Control byte in a Token Ring data/command frame consist of?
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Tokens in Token Ring networks are always 3 bytes in length.
Tokens in Token Ring networks are always 3 bytes in length.
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The Frame Check Sequence is an optional field in the frame structure.
The Frame Check Sequence is an optional field in the frame structure.
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The Ending Delimiter marks the ________ of the frame.
The Ending Delimiter marks the ________ of the frame.
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What is the maximum allowable size of the data field in a frame?
What is the maximum allowable size of the data field in a frame?
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The source address field contains the physical address of the sending station and can either be a ______ or ______.
The source address field contains the physical address of the sending station and can either be a ______ or ______.
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Match the following fields with their descriptions:
Match the following fields with their descriptions:
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Which bit is used by the Active Monitor station to indicate that it has seen the frame?
Which bit is used by the Active Monitor station to indicate that it has seen the frame?
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The Frame type '01' indicates a MAC frame and disregards control bits.
The Frame type '01' indicates a MAC frame and disregards control bits.
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What is the purpose of the Frame Check Sequence in a frame?
What is the purpose of the Frame Check Sequence in a frame?
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What is one of the primary functions of the active monitor in a token ring network?
What is one of the primary functions of the active monitor in a token ring network?
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In a token ring network, more than one active monitor can exist simultaneously.
In a token ring network, more than one active monitor can exist simultaneously.
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What frame is transmitted by a station to announce that it wants to become the new monitor?
What frame is transmitted by a station to announce that it wants to become the new monitor?
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If a station has not seen a token frame in the past ______ seconds, it may initiate a monitor contention process.
If a station has not seen a token frame in the past ______ seconds, it may initiate a monitor contention process.
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Match the following terms with their definitions:
Match the following terms with their definitions:
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What happens if two stations try to become the active monitor at the same time?
What happens if two stations try to become the active monitor at the same time?
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The active monitor is responsible for inserting a 24-bit delay into the ring.
The active monitor is responsible for inserting a 24-bit delay into the ring.
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Name one condition that initiates the monitor contention process.
Name one condition that initiates the monitor contention process.
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Study Notes
Token Ring Protocol
- Token ring is a LAN protocol operating at the data link layer (DLL) of the OSI model.
- It uses a special three-byte frame, the token, that circulates around the ring.
- Token possession grants permission to transmit on the medium.
- Initially used in IBM computers, it's now standardized with IEEE 802.5 protocol.
Data Transmission Process
- Empty frames circulate continuously on the ring.
- When a computer needs to send a message, it modifies an empty frame (inserting a 1 for example).
- The frame includes the message and destination ID.
- Each station checks the frame; the destination station copies the message and resets the token bit (back to 0).
- The originating station removes the message once it sees the changed token bit and that the message has been delivered.
- The frame then continues circulating as an empty frame ready to be used again.
Token Frame Usage with Bus Topology
- When no station transmits, a special token frame circulates.
- A station needing to transmit converts the token frame into a data frame.
- After data transmission, the frame is converted back to a token frame.
- An active monitor detects transmission errors and corrects them. Removing or inserting tokens as necessary.
- 4Mbit/s rings support only one token; 16Mbit/s rings support multiple tokens.
Token Frame Details
- The special token frame consists of three bytes.
- J and K are special non-data characters used for code violations.
Token Priority
- Token ring allows for priority transmission.
- 8 priority levels (0-7) are used
- A station with a higher priority can request priority access to the token.
- Priority is reflected in the bits when the token is received
- The station lowers its priority back to the original value after sending/receiving.
Token Ring Frame Format
- Token ring frames are expanded versions of token frames.
- Used by stations for MAC management or data transmission (from higher levels).
- Two basic frame types exist: tokens and data/command frames.
- Token frames consist of: start delimiter, access control byte, and end delimiter.
- Data/command frames vary in size, with information field sizes determining this.
Data/Command Frame Structure
- Data/command frame layout: start delimiter (SD), access control (AC), frame control (FC), destination address (DA), source address (SA).
- Additional: Protocol Data Unit (PDU) from Logical Link Control (LLC), Cyclic Redundancy Check (CRC), End delimiter (ED), and Frame Status (FS).
- Data frames carry upper-layer protocol information; Command frames carry control information.
Starting Delimiter
- A special bit pattern marks the beginning of the frame. J,K,0,J,K,0,0,0 is example.
- J and K are code violations in Manchester encoding.
Access Control
- P bits are the priority bits.
- T bit specifies a token frame.
- M bit is set by the Active Monitor (AM) station, present in the frame.
- R bits are reserved bits.
Frame Control
- This byte describes the data portion of the frame (if present).
- It indicates if the frame contains data or control information.
Destination and Source Addresses
- Six-byte fields specifying destination/source physical addresses.
- Local assigned address (LAA) or universally assigned address (UAA) of the station adapter.
Data Field
- Variable length field with a maximum size that depends on the ring speed.
- Can hold MAC management data or higher-layer information (around 4500 bytes max).
Frame Check Sequence (FCS)
- Four bytes used to store Cyclic Redundancy Check (CRC) for frame integrity.
- Used by the receiver for error detection.
Ending Delimiter
- Marks the end of a frame; counterpart to the starting delimiter.
- Bit pattern of J,K,1,J,K,1,I,E
Frame Status
- One-byte field used for acknowledgement.
- Indicates if the frame was received and copied by the intended receiver.
Active and Standby Monitors
- Every station belongs to an "active monitor (AM)" or "standby monitor (SM)" category.
- Only one active monitor exists on a ring at a time.
- Election or monitor contention chooses the active monitor.
- Monitors are selected when a signal loss occurs, another monitor isn't responding, or a timer on end-stations expires. (no token in 7 seconds).
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Description
This quiz covers the Token Ring protocol, which operates at the data link layer of the OSI model. It explores the process of data transmission using token frames and the protocol's historical background with IBM and IEEE standards. Test your understanding of how this LAN technology functions.
