Networking Concepts Quiz

Computer Networks

Presented by Dr. Keyvan Moataghed
Slides adapted from Computer Networking: A Top-Down Approach, 8th Edition by J.F. Kurose and K.W. Ross
Part 1, 2, 3, etc. numbered divisions of the presentation

Introduction

Overview of internet structure, protocols, layers, services, and security
What is the internet?
What is a protocol?
Network edge (hosts, access networks, physical media)
Network core (packet/circuit switching, internet structure)
Performance (loss, delay, throughput)
Protocol layers and service models
Security
History
The Internet: a "nuts and bolts" view
- Billions of connected computing devices (hosts)
- Internet's "edge" (running network apps at hosts)
- Packet switches (routers and switches forwarding data)
- Communication links (fiber optics, copper wire, radio frequency, etc)
The Internet: a "services" view
- Infrastructure (Web, streaming video, multimedia, etc.)
- Programming interface (sending/receiving apps connecting to Internet transport services)
- Service options (analogous to postal service)
What is Protocol?
- Human protocols (“What's the time? I have a question”, etc.)
- Received messages follow actions
- Network protocols (computers or machines, govern all Internet communication)
- Protocols: Define format, order of messages sent and received among network devices, and actions on those messages.
Network structure:
- Network edge: Hosts, clients, and servers in data centers
- Access networks, physical media: Wired and wireless communication links
- Network core: Interconnected routers, network of networks
Access networks: DSL (Digital Subscriber Line)
- Using existing (landline) telephone lines to central office DSLAM
- Data over DSL phone line to Internet
- Voice over DSL phone line to telephone net
- 24-52 Mbps dedicated downstream rate
- 3.5-16 Mbps dedicated upstream rate
Access networks: cable-based access
- FDM: Frequency Division Multiplexing
Access networks: home networks
- Wireless and wired devices
- Often combined in single box
- WiFi, wired Ethernet
Wireless access networks
- Connects end systems to routers via access points (base stations or Wifi access points)
- Wireless local area networks (WLANs):
  - Operate within a building(100 ft)
  - 802.11b/g/n (WiFi) transmission rates (11, 54, 450 Mbps)
  - Wide-area cellular access networks, provided by mobile operators (10's km)
Enterprise networks
- Mix of wired and wireless link technologies connecting a mix of switches and routers.
Access networks: datacenter networks
- High bandwidth links connecting hundreds to thousands of servers and to the Internet
Host: Sends packets of information (Data, Voice, Video)
- Host takes application message
- Breaks into smaller packets of length L bits
- Transmits at rate R
Packet switching: Major functions
- Routing: Determines source-destination paths & routing algorithms.
- Forwarding (Switching): Moves arrived packets from router input link to the appropriate router's output link.
- Store-and-Forward: Entire packet must arrive at router before it is transmitted on the next link. (transmission delay)
- Queueing: Packet arrives faster than it can be processed.
- Queuing and loss: If arrival rate to link exceeds transmission rate packets are queued or dropped.
Circuit Switching
- End-to-End Resources allocated and reserved for "call" between source and destination
- Each link has circuits; Dedicated resources- no sharing
- Circuit-like guaranteed performance (no sharing)
Circuit Switching Types
- FDM (Frequency Division Multiplexing)
- TDM (Time Division Multiplexing)
Packet Switching vs. Circuit Switching
Protocol layers and service models
- Layering
- Reference models (TCP/IP protocol layered Internet protocol stack & ISO OSI protocols)
- TCP/IP protocol layered Internet protocol stack (Layers: Application, Transport, Network, Link, Physical)

Internet Structure

Network of networks
Interconnected ISPs, hosts connect via access ISPs
Complex evolution driven by economics and national policies

Internet Architecture

Backbone: Connectivity between different segments of the Internet.
Tier 1 ISPs (building the backbone)
IXP (Internet exchange point) connects ISPs to backbone
POP (Point of Presence)

Protocol Layers

The TCP/IP Protocol Stack Services, Layering and Encapsulation
Support for application-layer services
Service delivery for different levels
Encapsulation: process of protocol adding messages onto already existing protocol's messages

Access Networks, Service Models, Protocols

Includes DSL, home networks, wireless access networks, enterprise, and datacenter network architectures

Packet Delay and Loss

Four sources of packet delay (transmission, propagation, queuing, and processing)
Packet queuing delay
Internet delays and routes
Packet loss
Throughput (bits/time unit)

Network Security

Firewalls: Isolates organization's internal network from the broader Internet.
Prevents Denial of Service (DoS) and other attacks.
Packet filters (stateless and Stateful)
Application gateways
Security in wireless and mobile networks (authentication and encryption)
- 802.11 (wireless local area network)
- 4G/5G (cellular)
Cryptography classification including different types of keys (symmetric and asymmetric)
- Hash methods
- Authentication Methods
- Encryption methods
Cryptanalysis
- Ciphertext only attack, Brute force, known-plaintext attack
Secure e-mail
IP Sec (IP Security): Authentication Header Protocol (AH) and Encapsulation Security Protocol(ESP).
SPD (Security Policy Database) and SAD (Security Association Database)