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)