Introduction to Computer Networking - Chapter 1

Introduction to Computer Networking

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Chapter 1 Roadmap

• 1.1 What is the Internet?: Fundamental questions about the Internet.
• 1.2 Network Edge: End systems, access networks, links.
• 1.3 Network Core: Packet switching, circuit switching, network structures.
• 1.4 Delay, Loss, Throughput in Networks: Analyzing network performance metrics.
• 1.5 Protocol Layers, Service Models: Understanding different layers and their functions in network communication.
• 1.6 Networks Under Attack: Security: Examining security issues in networking.
• 1.7 History: Overview of the evolution of networking.

Network Structure

• Network Edge: Hosts (clients and servers), data centers.
• Access Networks: Physical media (wired, wireless), communication links.
• Network Core: Interconnected routers, network of networks.

Access Networks and Physical Media

• Residential Access: Residential networks.
• Institutional Access: School and company networks.
• Mobile Access: Mobile networks.
• Bandwidth: The bits per second access network can handle.
• Shared/Dedicated Networks: Understanding how resources are allocated.

Access Network Examples

• DSL (Digital Subscriber Line): Uses existing telephone lines, with dedicated lines for voice and data transmission. Upstream and downstream rates vary (e.g., 1-2.5 Mbps up, <24 Mbps down).
• Cable Network: Uses shared cable lines, and frequency division multiplexing, with different channels for data and TV transmission. HFC offers asymmetric bandwidth rates (e.g., up to 30Mbps down, 2Mbps up).
• Home Network: Combining multiple wireless and wired devices into a single network using a router, firewall, NAT, and wired/wireless access.
• Enterprise Access: Ethernet networks used by companies and universities. Fast data transfer rates typical.
• Wireless Access: Shared networks connected via base stations (access points). LANs (local area networks) support 802.11b/g (WiFi). Wide-area networks like 3G and LTE.

Protocols

• Human Protocols: Everyday interactions (e.g., "What's the time?").
• Network Protocols: Precise, automated communication rules for machines (e.g., TCP, IP, HTTP).
• Protocol Format and Order: Defining messages, their format, and sequence for communications between network entities. 
• Actions on Message Transmission and Receipt: Outline actions taken when a message is sent and received.

Protocols: Example

• TCP connection request and response: Part of the communication protocol for getting a file from a website.

What's a Protocol? (Illustration)

• Shows human protocol ("Hi", "Got the time?") and computer network counterpart (e.g., TCP connection messages).

Host: Sending Packets of Data

• Hosts break messages into packets.
• Packets are transported across the network.
• Sending speed (transmission rate) is a parameter.

Physical Media

• Bit Propagation: Transmission of bits between transmitter and receiver via physical connections.
• Guided Media: Transmission through wires (e.g., twisted pair, coaxial, fiber).
• Unguided Media: Broadcasting, such as radio waves.

Physical Media Types

• Twisted Pair (TP): Two insulated copper wires (e.g., Ethernet).
• Coaxial Cable: Two concentric copper conductors.
• Fiber Optic: Glass fiber carrying light pulses.

Physical Media: Radio

• Signals are propagated using electromagnetic spectrum.
• Radio Link Types: Terrestrial microwave, LANs, cellular (3G, 4G, LTE), satellite networks.
• Propagation Effects: Interference, reflection, obstruction.

Delay and Loss

• Packet Queuing: Packets wait in buffers if the arrival rate is higher than the network capacity. Loss occurs when buffers overflow.
• Delay Sources: Transmission delay, propagation delay, nodal processing delay, and queuing delay.
• Caravan Analogy: Illustrates the concepts of transmission time and propagation time using car/truck analogies.

Throughput

• Throughput: The rate of bits sent and received over time.
• Instantaneous Throughput: Throughput at a particular moment.
• Average Throughput: Throughput measured over an extended period. 
• Bottleneck Link: Limits total throughput in a network path.

Traceroute

• Tool to measure delays and loss from the source to the destination router by sending probes.
• Network delays and routes can be tracked using the traceroute command.

Packet Loss

• Buffer Overflow: When the buffer capacity is exceeded, packets are dropped.
• Retransmission: Strategies for handling lost packets.