Computer Networking: CRC and CSMA/CD

A powerful error detection coding method. It uses a generator polynomial (G) to calculate a checksum (CRC bits) that is appended to the data bits (D). The receiver uses the same generator polynomial to check if the data is corrupted. If the remainder after dividing the received data by G is non-zero, an error is detected.

The data that is transmitted, represented as a binary number.

A specific bit pattern used in the calculation of the CRC. It's like a secret code template defining how to generate the CRC bits.

The extra bits calculated and added to the data bits to detect errors. They are like a signature or fingerprint for the data.

The process of dividing the data (D.2^r) and CRC bits (R) by the generator polynomial (G) to check for errors. If the remainder is non-zero, an error has occurred during transmission.

The process of forwarding data packets from one network to another, often across different networks or subnets.

A device responsible for forwarding data packets between networks based on their destination IP addresses.

The process of determining the next hop (router) for a data packet based on its destination IP address.

A table used by a router to store information about networks and their corresponding network addresses.

The address used to identify a device or host within a local network.

The address used to identify a device or host on a network.

The process of mapping an IP address to a MAC address.

A special type of IP packet that contains information about the MAC address of a device on the local network.

A special type of IP packet that contains information about the MAC address of a device on the local network.

A table used by a device to cache MAC addresses of recently contacted devices on the local network.

CSMA/CD stands for Carrier Sense Multiple Access with Collision Detection. This protocol is used in wired Ethernet networks to minimize collisions and improve efficiency. It works by having each node listen to the network before transmitting (Carrier Sense). If the network is busy, they wait until it is idle. If a collision occurs during transmission, the node immediately stops transmitting and sends a jam signal (Collision Detection). This allows for a more efficient use of the network bandwidth.

CSMA, or Carrier Sense Multiple Access, is a communication method where each node listens to the network before transmitting. This helps to prevent collisions but doesn't eliminate them completely. Due to propagation delay, two nodes might not hear each other's transmission, leading to a collision. In these cases, the entire packet transmission is lost.

CSMA/CD is more effective than CSMA in reducing wasted time due to collisions. When a collision is detected, the transmission is aborted immediately, saving valuable channel time. However, it's crucial to note that collision detection is easier in wired networks than in wireless environments.

In the Ethernet CSMA/CD algorithm, when a collision occurs, a node enters binary exponential backoff. This means the node waits for a random amount of time before attempting to resend the data. The waiting time increases exponentially with the number of collisions, giving priority to nodes that haven't collided before.

Channel partitioning MAC protocols divide the network channel into time slots or frequencies, ensuring fair and efficient sharing of the channel at high network loads. However, they can be inefficient at low loads because even if only one node needs the channel, a portion is still allocated to other nodes, leading to unused bandwidth.

Random access MAC protocols, like Aloha and CSMA, allow any node to transmit whenever they want. This is efficient at low loads, as a single node can fully utilize the channel. But, at high loads, collisions become frequent, leading to wasted transmission time.

Taking turns MAC protocols aim to combine the efficiency of random access protocols at low loads with the fairness of channel partitioning protocols at high loads. These protocols try to balance the benefits of both approaches, providing a better overall performance across different network conditions.

Propagation delay is the time it takes for a signal to travel from one point to another in a network. This delay can cause collisions in CSMA, as two nodes might not hear each other's transmission due to the time it takes the signal to reach them.

A device that filters network traffic based on rules to protect a network from unauthorized access.

A large-scale computer system that houses servers, networking equipment, and other infrastructure, often with high levels of redundancy and security.

A communication protocol used for routing data packets between different autonomous systems (AS) on the internet.

A communication protocol used for routing data packets within the same autonomous system (AS).

A network communication protocol used for routing data packets within a single network.

A device that connects devices within a local network, typically using Ethernet technology, and forwards data packets based on MAC addresses.

A device that controls access to a wireless network, authenticates users, and manages network resources.

The network layer address is the IP address. It identifies a unique device on the entire internet.

The data link layer address is the MAC address, a unique identifier for a device on a local network (LAN).

A frame is a data packet at the data link layer. It encapsulates other protocols like IP, adding headers for local network transmission.

Each network interface card or device has a unique MAC address, usually burned into its hardware. This enables devices on a local network to identify and communicate with each other.

Ethernet is the most common wired LAN technology, using a bus or switched topology with high speeds. It's known for its simplicity and cost-effectiveness.

A collision domain is a section of a network where devices can interfere with each other's transmissions.

In a bus topology, all nodes share a single cable. They can collide with each other since transmission is broadcast on the cable.

A switched Ethernet network uses a central switch to connect devices. Each connection is individual, eliminating collisions.

ARP is a protocol that translates IP addresses into MAC addresses, allowing devices to communicate on a local network.

VLANs (Virtual Local Area Networks) allow administrators to segment a physical network logically, isolating traffic based on user groups or applications.

A virtual network that segregates devices on a physical network into logical groups based on their requirements. Each VLAN acts like a separate broadcast domain, improving security, performance, and manageability.

A type of VLAN implementation where each port on a switch is configured to belong to a specific VLAN. This allows for precise control over which devices can communicate with each other.

A process that occurs when a switch needs to learn the MAC address associated with a specific device. This is typically done through a learning procedure where the switch observes the traffic sent by devices on a network.

The process of forwarding data frames between devices on the same network based on their MAC addresses. Switches maintain a forwarding table to store MAC address-to-port mappings.

All devices connected to a single switch share the same broadcast domain. This means all Layer 2 broadcast traffic (e.g., ARP, DHCP) is forwarded to all devices on the network.