Multiple access protocols

Let’s explore into the fascinating world of multiple access protocols in computer networks. These protocols play a crucial role in managing access to shared communication channels, ensuring efficient data transmission among numerous devices

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Let’s explore the definitions of random-access protocol, controlled access, and channelized:

1. Random Access Protocol:

A random-access protocol is a communication method that allows multiple devices to access a shared communication channel in a random or arbitrary order. Unlike scheduled access methods, where devices wait for specific time slots or permission, random access protocols allow devices to transmit data whenever they need to.

Think of it like a group chat where everyone can send messages without waiting for their turn. These protocols help manage the chaos by dividing the channel into time slots or packets of data, ensuring efficient communication1.

2. Controlled Access: In apartment buildings, controlled access allows only residents (or authorized individuals) to enter the building using keys, key cards, or access codes2.

In data access models, controlled access restricts data availability to qualified researchers whose research plans are reviewed and approved3.

On highways, controlled-access highways (such as freeways or motorways) have regulated traffic flow, no at-grade crossings, and no direct access to properties4.

3. Channelized:

Channelized (or channelize) means to guide something through a channel or provide a specific pathway. It can refer to physical channels (e.g., waterways) or abstract pathways (e.g., communication channels).

Examples:

Engineers channelized rivers to prevent flooding and improve navigation.In networking, channelization involves dividing available bandwidth into smaller portions (e.g., time slots or frequency bands) for multiple users or devices5.

Random Access Protocol:Random Access Protocol:

• In this protocol, all stations have equal priority, meaning no station has more authority than another.
• Stations can send data based on the medium’s state (idle or busy).
• Features: No fixed time for sending data. No fixed sequence for stations sending data.
• Subdivisions:
• Pure ALOHA: Designed for wireless LANs but applicable to shared media. Multiple stations can transmit data simultaneously, leading to collisions. After sending data, a station waits for an acknowledgment. If none arrives within the allotted time, it waits for a random back-off time and re-sends the data. Vulnerable Time: 2×Frame?transmission?time Maximum throughput: 0.184 for G=0.5

Slotted ALOHA:

• Divides time into slots, allowing data transmission only at the beginning of slots.
• If a station misses its allowed time, it waits for the next slot.
• Reduces collision probability.
• Vulnerable Time: Frame?transmission?time
• Maximum throughput: 0.368 for G=1 .
• CSMA/CD deals with collisions after they happen, while CSMA/CA prevents collisions proactively.
• CSMA/CD is for wired networks (like Ethernet), and CSMA/CA is for wireless networks (like Wi-Fi).

Remember, these protocols ensure efficient communication and help manage network resources! ??

For more details, you can explore resources like GeeksforGeeks1 and ComputerNetworkingNotes2. Happy learning! ??

Remember, these protocols are like teachers managing students in a classroom. They ensure orderly communication, preventing chaos and data overlap. ??

For more information, you can explore resources like GeeksforGeeks, TutorialsPoint, and PrepBytes. Happy learning! ??

: GeeksforGeeks: Multiple Access Protocols : TutorialsPoint: Computer Networks - Multiple Access Protocols : PrepBytes: Multiple Access Protocols

Controlled Access Protocols

Controlled access protocols ensure orderly communication by allowing only one node to send at a time, avoiding collisions on a shared medium. Here are the three primary controlled access methods:

1. Reservation: In the reservation method, a station must make a reservation before sending data.

The timeline consists of two periods:

Reservation interval: Fixed time length during which stations reserve slots. Data transmission period: Variable frames for actual data transmission.

If there are M stations, the reservation interval is divided into M slots, with each station having one slot.

During its slot, a station announces its intention to transmit by inserting a 1-bit.

After checking all slots, each station knows which others wish to transmit.

Stations with reserved slots then transfer their frames in the specified order.

Advantages of Reservation: Predictable network performance: Reservation-based methods provide predictable performance, crucial for real-time applications. Reduced contention: Pre-allocated access reduces contention for network resources. Quality of Service (QoS) support: Different reservation types can prioritize traffic. Efficient bandwidth use: Time and frequency multiplexing optimize bandwidth. Support for multimedia applications: Ensures guaranteed resources for voice, video, and data1.

Disadvantages: Complexity due to reservation management.

2. Polling:

In polling, a central controller (e.g., a base station) queries stations to determine which one can transmit.

The controller polls stations sequentially.

If a station has data, it responds with permission to transmit.

Advantages of Polling:

Centralized control: Efficient for small networks.

Fairness: Ensures each station gets a turn.

Low overhead: Minimal contention.

Disadvantages:

Single point of failure (the controller).

Overhead for polling messages.

3. Token Passing:

Stations pass a token (a special frame) to indicate their right to transmit.

• Only the station holding the token can send data.
• After transmission, the token moves to the next station.
• Advantages of Token Passing:
• Fairness: Each station gets a turn.
• No collisions: Only one station transmits at a time.
• Simple implementation.
• Disadvantages:
• Token overhead.
• Token loss can disrupt communication.

Channelization

Channelization involves dividing the available bandwidth of a link into smaller portions for multiple stations to access simultaneously. Here are the key channelization methods:

1. Time Division Multiple Access (TDMA):

• Divides time into fixed slots.
• Each station gets a dedicated time slot.
• Efficient for bursty traffic.
• Used in cellular networks and satellite communication.

2. Frequency Division Multiple Access (FDMA):

• Divides the frequency spectrum into non-overlapping channels.
• Each station uses a specific frequency band.
• Common in radio communication.

3. Code Division Multiple Access (CDMA):

• Assigns unique codes to each station.
• All stations transmit simultaneously using different codes.
• Widely used in 3G and 4G cellular networks.

Remember, controlled access ensures orderly transmission, while channelization optimizes resource sharing. ??

For more details, you can explore resources like GeeksforGeeks2 and Baeldung3. Happy learning! ??