Ch. 6 - Link Layer & LANs Flashcards
Link Layer
Layer responsible for node-to-node data transfer.
LAN
Local Area Network for connecting devices in proximity.
Multiple Access Protocols
Methods for multiple devices to share a channel.
Framing
Encapsulating datagrams into frames for transmission.
MAC Address
Unique identifier for network interface at link layer.
Half-Duplex
Communication mode where transmission is one-way at a time.
Full-Duplex
Communication mode allowing simultaneous two-way transmission.
VLAN
Virtual Local Area Network for segmenting network traffic.
Cyclic Redundancy Check (CRC)
Error-detecting code for ensuring data integrity.
Point-to-Point Link
Direct connection between two network nodes.
Broadcast Link
Shared medium allowing multiple devices to communicate.
Signal Attenuation
Loss of signal strength during transmission.
Noise
Unwanted electrical signals interfering with data transmission.
Datagram
Basic unit of data used in packet-switched networks.
Transport Segment
Data unit passed between transport and link layers.
Redundancy
Extra data added for error detection and correction.
Two-Dimensional Bit Parity
Error detection method using rows and columns of bits.
Single Bit Parity
Error detection using a single parity bit.
Link Virtualization
Abstracting physical links for improved resource management.
Shared Wire
Physical medium for multiple nodes to communicate.
Shared Radio
Wireless medium allowing multiple nodes to transmit.
Collision
Interference when multiple nodes transmit simultaneously.
Multiple Access Protocol
Algorithm for nodes to share communication channels.
Channel Partitioning
Divides channel into exclusive segments for nodes.
Random Access
Allows nodes to transmit without prior coordination.
Taking Turns
Nodes transmit sequentially, allowing longer turns.
What is ALOHA?
Random access protocol allowing unsynchronized transmissions.
Slotted ALOHA
Transmissions occur at the start of time slots.
Efficiency of ALOHA
Maximum throughput of Pure ALOHA is 18%.
What is CSMA?
Carrier Sense Multiple Access; listen before transmitting.
What is CSMA/CD?
Collision Detection in CSMA; aborts on collision.
Polling
Controller node invites others to transmit in turn.
Token Passing
Control token passed sequentially among nodes.
Backoff Algorithm
Random wait time after collision before retransmitting.
Channel Data Rate (R)
Maximum data transmission rate of a channel.
Synchronization
Nodes must coordinate timing for effective communication.
Collision Detection
Identifying simultaneous transmissions to minimize waste.
Jam Signal
Signal sent to indicate a collision has occurred.
Exponential Backoff
Increases wait time exponentially after each collision.
Transmission Latency
Delay experienced before a node can transmit.
Single Point of Failure
System vulnerability where one component failure halts operation.
Cable Headend
Facility where cable signals are processed.
What is CMTS?
Cable Modem Termination System for managing cable modems.
Cable Modem
Device that connects a home network to the internet.
Upstream Channel
Path for data sent from users to CMTS.
Downstream Channel
Path for data sent from CMTS to users.
What is DOCSIS?
Data Over Cable Service Interface Specification standard.
MAP Frame
Management frame for upstream slot assignments.
Random Access Protocols
Protocols allowing multiple users to access channels.
CSMA/CA
Carrier Sense Multiple Access with Collision Avoidance.
Ethernet Frame
Data packet format used in Ethernet networks.
MAC Table
Table mapping IP addresses to MAC addresses.
Minislots
Small time slots for upstream data transmission.
Contention
Competition among users for channel access.
Preamble
Synchronization pattern for sender and receiver clocks.
Switch
Link-layer device that forwards Ethernet frames.
Broadcast domain
Logical division of a network segment for broadcasts.
Port-based VLAN
VLANs defined by switch port assignments.
Ethernet payload
Data carried within an Ethernet frame.
Link virtualization
Techniques to create virtual links over physical networks.
Ethernet speeds
Range from 10 Mbps to 400 Gbps.
Switch forwarding table
Table mapping MAC addresses to switch interfaces.
Self-learning switch
Switch that learns MAC addresses dynamically.
Dynamic membership
Ports can be assigned among VLANs dynamically.
Forwarding between VLANs
Requires routing, similar to separate switches.
Trunk port
Carries frames between VLANs across switches.
802.1Q protocol
Adds VLAN ID info to Ethernet frames.
Label-switched router
Router that forwards based on label value.
Traffic engineering
Routes flows differently based on source/destination.
Fast reroute
Pre-computes backup paths for link failures.
Multiprotocol Label Switching (MPLS)
High-speed IP forwarding using fixed-length labels.
MPLS signaling
Uses modified protocols to carry MPLS info.
RSVP-TE
Signaling protocol for MPLS forwarding setup.
Border routers
Connect datacenter to external networks.
Tier-1 switches
Connect to multiple Tier-2 switches.
Top of Rack (TOR) switch
Connects server blades within a rack.
Application-layer routing
Load balancer directs requests within datacenter.
RoCE
Remote DMA over Converged Ethernet.
Data center challenges
Managing load and ensuring reliability.
MPLS forwarding table
Distinct from IP forwarding tables.
A day in the life
Synthesis of protocols in web request process.
Demultiplexing
Process of separating multiple signals into individual streams.
First-hop Router
Initial router that forwards packets from a client.
