IE1030 Data Communication Networks - Link Layer Flashcards

Comprehensive vocabulary flashcards for IE1030 covering the Link Layer, Ethernet operations, Switching, VLANs, and IEEE 802.11 Wireless LANs.

Link Layer

The layer responsible for encapsulating network layer datagrams in frames and delivering them over a physical link between nodes.

Frame

The link layer data unit which consists of a header, a payload (the network layer datagram), and a trailer.

MAC Address (L2 Address)

A unique $48$-bit ($6$ bytes) address used for communication within a specific network, often expressed as hexadecimal numbers like $00:80:3F:2A:17:21$.

Broadcast Address

A special destination address reserved for all hosts on a network, represented as all 1s or $FF:FF:FF:FF:FF:FF$ in hexadecimal.

Ethernet

The dominant wired LAN technology defined by IEEE $802.3$ standards, initially using bus topology and currently utilizing switched star topology.

CSMA/CD

Carrier Sense Multiple Access with Collision Detection; a protocol where a host senses the channel before transmitting and aborts the transmission if a collision is detected.

Preamble

An Ethernet frame component consisting of $7$ bytes of $10101010$ followed by one byte of $10101011$, used by the receiver to identify bit times.

CRC (Cyclic Redundancy Check)

An error control mechanism where the sender calculates a checksum and appends it to the frame trailer for the recipient to verify data integrity.

Hub

A physical layer device that copies an incoming signal to all other ports; it operates in half-duplex mode and creates a single collision domain.

Ethernet Switch

A link-layer device that takes an active role in storing and forwarding frames based on MAC addresses, effectively creating separate collision domains for each link.

Self-learning

The process by which a switch automatically builds its MAC address table by recording the source MAC address and the incoming port of received frames.

Flooding

A switch forwarding action where a frame is sent out on all ports except the arriving port, occurring when the destination MAC address is not found in the switch table.

Half-duplex mode

A communication mode where only one device in a segment can transmit at a time, and collisions occur if multiple devices transmit simultaneously.

Full-duplex mode

A communication mode where both devices in a segment can send and receive data at the same time, eliminating collisions and the need for CSMA/CD.

Ethernet Auto-negotiation

The process where a host and a switch agree on the highest possible speed and the best duplex mode (half or full) supported by both devices.

VLAN (Virtual LAN)

A technology that allows multiple virtual local area networks to be configured over a single physical LAN infrastructure to provide traffic isolation and manage broadcast domains.

Trunk Port

A switch port designed to connect to another switch, capable of carrying traffic for multiple VLANs simultaneously.

802.1Q

A protocol that adds a $4$-byte VLAN tag to Ethernet frames forwarded via trunk ports to identify which VLAN the frame belongs to.

BSS (Basic Service Set)

The fundamental building block of a wireless LAN architecture, containing wireless hosts and potentially an Access Point (AP).

Infrastructure Mode

A wireless network configuration where hosts communicate through a base station known as an Access Point (AP).

Ad hoc Mode

A wireless network configuration consisting only of hosts without an Access Point; also called an ad hoc BSS.

ESS (Extended Service Set)

A network formed by two or more BSSs with Access Points interconnected by a distribution system (wired or wireless).

Passive Scanning

A process where wireless hosts listen for Beacon frames sent by Access Points to discover and join a network.

Active Scanning

A process where a wireless host broadcasts a Probe Request frame and listens for Probe Response frames from Access Points to join a network.

CSMA/CA

Carrier Sense Multiple Access with Collision Avoidance; the protocol used in $802.11$ wireless LANs to prevent collisions since detection is difficult in wireless environments.

DCF (Distributed Co-ordinated Function)

A contention-based service in $802.11$ where all stations contend for access to the shared medium.

PCF (Point Co-ordinated Function)

A contention-free service in $802.11$ where the Access Point polls stations and grants them permission to transmit.

SSID

The name of a wireless network included in beacon frames or probe responses.

BSSID

The MAC address of an Access Point (AP) in a wireless network.