Lecture Eight Flashcards
1
Q
What is a Network?
A
A system or group of interconnected entities.
2
Q
Examples of Networks
A
Social Networks: Interactions and connections among individuals or groups.
Professional Networks: Connections based on professional affiliations.
Road/Rail Networks: Infrastructure for transportation and logistics.
Biological Networks: Interconnected biological systems, such as neural networks.
Radio Networks: Systems of interconnected radio stations and transmitters.
Electrical Networks: Systems of interconnected electrical components.
3
Q
Network Characteristics
A
Defined by their constituent entities and the nature of their interconnections.
4
Q
Data Networks - Purpose
A
Facilitate efficient transfer and exchange of information.
5
Q
Data Networks - Modern Context
A
Transition from physical to digital data exchange, emphasizing speed and efficiency.
6
Q
Coaxial Cables
A
Thinnet (10Base2): Maximum length of 200 meters, largely obsolete in modern networks.
Thicknet (10Base5): Maximum length of 500 meters, also obsolete.
7
Q
Twisted Pair Cables
A
Utilize differential mode transmission.
Shielded Twisted Pair (STP): Provides protection against electromagnetic interference.
Unshielded Twisted Pair (UTP):
Cat3: Supports 10 Mbps, used in older telecommunication setups.
Cat5: Supports 100 Mbps, common in traditional Ethernet networks.
Cat6: Supports 1 Gbps, used for high-speed Ethernet.
8
Q
UTP Cabling - Advantages Over Coaxial
A
Less prone to electromagnetic interference and crosstalk.
9
Q
UTP Cabling - Differential Model Transmission
A
Signal Encoding: Utilizes two complementary signals.
Signal Detection: Based on voltage differences between the pair.
Noise Handling: Uniform noise across pairs allows for effective decoding.
10
Q
UTP Cabling - Twist Rates
A
Different twist rates minimize interference in bundled cables.
11
Q
UTP Cabling - Ethernet Cable Types
A
Straight-Through Cables: Connect devices of different types (e.g., switch to router).
Crossover Cables: Connect devices of the same type (e.g., switch to switch).
12
Q
Optical Fibre - Material
A
Made by drawing glass (silica) or plastic to a fine diameter.
13
Q
Optical Fibre - Single Mode Fibres (SMF)
A
Supports one propagation path.
Used for long-distance communication (>1 km).
14
Q
Optical Fibre - Multi Mode Fibres (MMF)
A
Supports multiple propagation paths.
Wider core diameter, used for short-distance links.
15
Q
Optical Fibre - Applications
A
Used in long-haul trunks, metropolitan trunks, local loops, and Local Area Networks (LANs).
16
Q
Wireless Transmission Media - Transmission Without Conductors
A
Information transmitted using electromagnetic waves.
17
Q
Wireless Transmission Media - Characteristics
A
Unbound and Unguided: No physical medium required for transmission.
Long-Distance Capabilities: Can travel vast distances without the need for a line of sight.
Stochastic Medium: Affected by scattering and deflection, making it unpredictable.
18
Q
A
19
Q
Wireless Transmission Media - Examples
A
Sound Waves
Water Waves
Light Waves
Vacuum (Space)
19
Q
Wireless Technologies
A
Wi-Fi
Bluetooth
3G/4G/5G LTE
Satellite Communications
20
Q
Hubs - Definition
A
Basic networking devices operating at the Physical Layer.
21
Q
Hubs - Functionality
A
Repeaters: Relay incoming bits to all other connected links.
Collision Domains: Define areas where data packets can interfere with each other.
Limitations: No framing or MAC protocol, rely on host Network Interface Cards (NICs) to detect collisions.
22
Q
Hubs - Usage
A
Historically used in simple network setups, largely replaced by switches in modern networks.
23
Q
Collision Domains - Defintion
A
A network segment where data packets can interfere and collide, causing transmission failures.
24
Collision Domains - Collisions
Occur when two devices attempt to transmit simultaneously on the same medium.
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Collision Domains - Size and Timing
Impact: Collision domains and packet size affect the likelihood and severity of collisions.
Late Collisions: Occur when the sender finishes transmission before the initial bits reach the most remote node.
26
Collision Domains - MAC Protocols
Ethernet Example: Uses Carrier Sense Multiple Access with Collision Detection (CSMA/CD) to manage collisions.
27
Broadcast Domains - Definition
A network segment where devices can communicate via broadcast messages at the Data Link Control (DLC) layer.
28
Broadcast Domains - Characteristic
Defined by Routers: Layer 3 devices create distinct broadcast domains.
Scope: Includes all interconnected Layer 2 networks, such as those linked by switches and bridges.
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Broadcast Domains - Separation of Domains
Collision Domains: Smaller segments within broadcast domains where collisions can occur.
Broadcast Domains: Larger areas encompassing multiple collision domains.
30
Switches - Operational Layer
Function at the Data Link Control (Layer 2).
31
Switches - Functionality
Frame Forwarding: Directs frames only to the destination port, reducing unnecessary network traffic.
Collision Domain Separation: Each port on a switch typically represents a separate collision domain, eliminating collisions.
Efficiency: Increases network efficiency by reducing congestion and enhancing bandwidth usage.
32
Switch Tables - Functionality
Switches maintain tables to track devices connected to each port.
33
Switch Tables - Structure
Consist of tuples containing Host MAC Address, Port Number, and Time-to-Live (TTL).
34
Switch Tables - Creation
Self-Learning: When a frame is received, the switch records the source MAC address and associated port.
Frame Handling: Uses the switch table to forward frames to the correct destination port or flood if unknown.
35
Frame Filtering/Forwarding
two basic functions of an Ethernet switch that help determine how to forward frames
36
Frame Filtering
Filters out ports and only forwards data to the destination MAC address. Switches will never forward a frame back out the same port it received it on.
37
Frame Forwarding
Looks up the destination address in the MAC address table and forwards the frame to that port. Switches can use three different methods to forward frames out the appropriate switchport:
Store and forward: Copies the entire frame into a memory buffer and inspects it for errors
Cut-through: Stores nothing and only inspects the destination MAC address
Fragment free: Inspects only the first portion of the frame
38
Frame Filtering/ Forwarding - Process Overview
Record Link: Note the link associated with the sending host.
Lookup: Check the destination MAC address in the switch table.
Decision:
If destination found on the same segment, drop the frame.
Otherwise, forward the frame to the indicated interface.
If unknown, flood the frame to all ports except the incoming one.
39
Frame Filtering/ Forwarding - Objective
Enhance efficiency by minimizing unnecessary network traffic and optimizing frame delivery.
40
Multiple Switch Topologies - Complexity Management
Utilizes the self-learning method for topology discovery and management.
41
Multiple Switch Topologies - Scalability
Supports large-scale networks by interconnecting multiple switches and creating extended networks.
42
Multiple Switch Topologies - Resilience
Provides multiple pathways for data, enhancing fault tolerance and reliability.
43
Spanning Tree Protocol - Purpose
Prevents network loops in Ethernet networks with multiple paths.
44
Spanning Tree Protocol - Process
Root Bridge/Switch Definition: Elect the root bridge based on bridge priority and MAC address.
Least Cost Paths: Calculate shortest paths to the root bridge.
Loop Breaking: Identify and disable redundant paths to prevent loops.
Redundant Links: Utilize alternative paths for network resilience and recovery.
45
LAN Using Switches - Switching Operation
Takes place at the Data Link Layer (Layer 2).
46
LAN Using Switches - Broadcast Domains
All connected devices share the same broadcast domain.
Increases traffic overhead, collision risks, and reduces efficiency.
47
LAN Using Switches - Scalability
Limited scalability in traditional Ethernet networks due to broadcast overhead.
48
LAN Using Switches - Example
Comparison of Network Throughput:
Traditional Ethernet Network: 10 Mbps bandwidth results in limited throughput, suitable for small networks.
Telephone Network: Despite lower bandwidth (56 Kbps), achieves higher throughput due to efficient switching and reduced collisions.
Implications: Highlights the importance of efficient switching and network design in enhancing performance.
49
Routers - Operational Layer
Function at the Networking Layer (Layer 3).
50
Routers - Purpose
Connect networks of different types and address spaces.
Route packets based on destination IP addresses using routing tables.
51
Routers - Characteristics
Specialized hardware and software for efficient packet forwarding and routing.
Enable communication between distinct networks, such as LANs and WANs.
52
Switches
Operate at the Data Link Control (DLC) layer.
Handle frames within local networks.
Utilize switch tables, filtering, and self-learning algorithms.
53
Routers
Operate at the Network Layer.
Handle packets among different networks.
Use routing tables and algorithms/protocols for packet forwarding.
54
Switches vs. Routers - Comparison
Switches optimize internal network traffic, while routers manage inter-network communication.
55
Queueing Theory - Definition
Mathematical study of waiting lines or queues.
55
Queueing Theory - Purpose
Predict queue lengths and waiting times to inform resource provisioning and management decisions.
56
Queueing Theory - Application Areas
Telecommunications
Traffic Engineering
Computing
Industrial Engineering
57
Queueing System Model
Arrival: Customers (jobs) arrive at the queue.
Waiting: Jobs wait to be admitted to the service.
Processing: Jobs are processed by servers.
Departure: Jobs leave the system after processing.
58
Queueing Theory: Basic Model - Components
Customers: Represent jobs or tasks requiring service.
Queue: Line where customers wait for service.
Servers: Nodes that process customer requests.
59
Queueing Theory: Basic Model - Complexity
Systems may have multiple servers and shared queues, impacting service dynamics.
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Queueing Theory: Basic Model - System Definition
Crucial to understand system boundaries and customer flow for accurate modeling and analysis.
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Examples of Queueing Systems
Data Networks: Packets are customers assigned to communication links for transmission.
Virtual Circuits: Customers represent ongoing conversations between network points.
Telephone Networks: Active calls are customers, with service time as call duration.
62
Service Time Calculations
For packets: Service time is the ratio of packet length to link transmission capacity.
For conversations: Service time corresponds to conversation duration.
63
Queueing Theory - Parameters
Customer Arrival Rate: Frequency of customers entering the system per unit time.
Service Rate: Number of customers served per unit time when the system is busy.
Interarrival Times: Patterns of customer arrivals (e.g., evenly spaced, batch arrivals).
64
Littleβs Theorem - Statement
In a steady state, the average number of customers π in the system is equal to the arrival rate π multiplied by the average time π spent in the system: π = ππ
65
Littleβs Theorem: Intuition - Conceptual Understanding
Crowded systems (large π) are associated with long delays (large
π), and vice versa.
66
Littleβs Theorem: Intuition - Examples
Traffic on a Rainy Day: Increased traffic congestion leads to longer travel times.
Fast-Food Restaurant: Shorter service times result in smaller waiting areas compared to traditional restaurants.
67
Littleβs Theorem - System Definition
Careful selection of the system and arrival points is crucial for applying Little's Theorem effectively.
68
Littleβs Theorem Applications - Multi-Line Network Example
Scenario: Network of π transmission lines receiving packets at rates π1,π2,...,ππ
Observation: Average total number of packets (π) in the system.
Average Delay Calculation:
π=π/βππ : Average delay per packet, independent of packet length distribution and routing methods.
69
Local Area Network (LANs) - Definition
Networks connecting computers and devices within a limited geographic area, managed locally.
70
Local Area Networks (LANs) - Purpose
Facilitate resource sharing, such as printers and storage, among multiple devices.
71
Local Area Network (LANs) - Components
Devices: Computers, peripherals.
Infrastructure: Cabling, switches, gateways, firewalls.
72
Local Area Networks (LANs) - Common Technologies
Ethernet: Wired LAN standard.
Wi-Fi: Wireless LAN technology.
73
Local Area Networks (LANs) - Legacy Technologies
ARCNET: Early LAN protocol.
AppleTalk: Networking protocol for Apple devices.
Token Ring: Legacy LAN technology using token-passing protocol.
74
LAN Topologies (Bus Topology) - Structure
Nodes directly connected to a common linear or branched half-duplex link called a bus
75
LAN Topologies (Bus Topology) - Characteristics
Every host receives every packet with equal transmission priority.
76
LAN Topologies (Bus Topology) - Advantages
Simple setup and easy connection of devices.
Efficient cabling compared to other topologies.
Suitable for small networks.
77
LAN Topologies (Bus Topology) - Disadvantages
Single points of failure, such as a cut bus or repeater failure.
Frequent collisions leading to inefficiencies.
Scalability limitations.
78
LAN Topologies (Ring Topology) - Structure
Each node connects to exactly two other nodes, forming a continuous pathway for signals (a ring).
79
LAN Topologies (Ring Topology) - Characteristics
Can be unidirectional or bidirectional.
Uses token passing to control access to the medium.
80
LAN Topologies (Ring Topology) - Advantages
Fair service distribution among hosts.
Better performance than bus topologies.
No central host required.
Easy maintenance and fault identification.
81
LAN Topologies (Ring Topology) - Disadvantages
Single point of failure if a host fails.
Communication delay proportional to ring size.
Complex configuration when adding hosts.
82
LAN Topologies (Star Topology) - Structure
Each host is connected to a central node that manages network traffic.
83
LAN Topologies (Star Topology) - Characteristics
Central node can be a hub, switch, or computer.
Passive central nodes echo traffic, while active nodes prevent duplicate receptions.
84
LAN Topologies (Star Topology) - Advantages
High reliability; a faulty host does not impact the rest of the network.
85
LAN Topologies (Star Topology) - Disadvantages
Requires more cabling, increasing costs.
Central node is a single point of failure.
86
Network Components
Bridges: Connect same-type networks.
Routers: Connect different-type networks and manage routing between them.
Packet-Switch Exchange (PSE): Handles packet switching between networks.
Gateways: General-purpose computers connecting distinct networks.
87
Diverse Set of Network Services
Integration Needs: Accommodate various traffic types on the same network infrastructure.
Examples:
Internet Traffic: Short messages, low arrival rates, fast response, high reliability.
File Transfer: Long messages, bursty traffic, high reliability, tolerance for delays.
VoIP: Short packets, smooth traffic, minimal delay, lower reliability concerns.
Graphics and Video: Long messages, delay variability critical for video, traffic can be smooth or bursty.
88
Layered Network Architecture
Standard: ISO (International Standards Organization) OSI Model (Open Systems Interconnection).
Design: Modular, hierarchical, distributed system organization.
Modular: System comprised of simpler components with interlocking interfaces.
Advantages:
Interchangeability: Easier replacement and upgrading of components.
Standardization: Ensures compatibility and consistency across implementations.
Problem Solving: Employs a divide-and-conquer approach for complex issues.
89
Network Architecture Modules
Structure: Modules organized in vertical layers, each as a Black Box.
Interactions: Modules use services from lower layers to provide services to upper layers.
Isolation: Each layer operates independently, providing specific functionalities.
Objective: Simplifies complexity by isolating responsibilities and facilitating modular design.
90
Layered Network Architecture
Hierarchy:
Service: Functionality provided by a layer to the above layers.
Functions: Implementation of services within the layer.
Interfaces: Standardized communication mechanisms between layers.
Example: Application, Presentation, Session, Transport, Network, Data Link, Physical layers in OSI model.
91
Layered Network Architecture (Distributed)
Concept: Layers expose a unified interface but operate in a distributed manner.
Functionality: Provides consistent services across distributed systems.
Implementation: Ensures interoperability and cohesion in distributed network environments.
92
The OSI Standard
Purpose: Framework for standardizing network communication protocols.
Layers:
Application: Provides network services to applications.
Presentation: Translates data formats between application and network.
Session: Manages sessions between applications.
Transport: Ensures reliable data transfer.
Network: Routes packets across networks.
Data Link: Handles node-to-node data transfer.
Physical: Manages transmission of raw bits over physical medium.
93
OSI Standard Protocols
Layer Protocol Examples:
Application Layer: FTP, Telnet.
Session Layer: (No specified protocols in the slide).
Transport Layer: TCP (Transmission Control Protocol), UDP (User Datagram Protocol).
Networking Layer: IP (Internet Protocol).
Protocol Functions: Each protocol provides specific services aligned with its layer's responsibilities.
