Document Analysis Quiz

Introduction to Computer Networking

• A note on the use of slides: Slides are freely available for faculty, students, and readers. They are in PowerPoint form and can be modified and adapted to individual needs. They should be cited properly.

• Computer Networking (A Top Down Approach, 6th edition): Authored by Jim Kurose and Keith Ross, published by Addison-Wesley in March 2012.

Roadmap for Chapter 1

• 1.1 What is the Internet?
• 1.2 Network Edge: End systems, access networks, links.
• 1.3 Network Core: Packet switching, circuit switching, network structure.
• 1.4 Delay, Loss, Throughput in Networks: How networks handle transmission, data loss, and rates.
• 1.5 Protocol Layers, Service Models: How different layers communicate and provide services.
• 1.6 Networks Under Attack: Security: Threats and vulnerabilities.
• 1.7 History: Background of the internet.

"Nuts and Bolts" View of the Internet

• Millions of connected computing devices (hosts/end systems).
• End systems running network applications.
• Communication links (fiber, copper, radio, satellite).
• Transmission rate (bandwidth).
• Packet switches (routers and switches) forward packets (chunks of data).

"Network of Networks" View of the Internet

• Internet as interconnected internet service providers (ISPs).
• Protocols control message sending and receiving (e.g., TCP, IP, HTTP, Skype, 802.11).
• Internet Standards documented in RFCs (requests for comments).
• IETF (Internet Engineering Task Force) defines and maintains these standards.

Internet as a Service View

• Infrastructure that serves applications like Web, VoIP, email.
• Programming interfaces for applications.
• Service options similar to postal service.

What is a Protocol?

• Protocols define message format, order of communications.
• Govern communication between network entities (machines).
• Controls the actions taken during transmission.

Access Networks and Physical Media

• Connecting end systems to edge routers.
• Residential, institutional, and mobile access networks.
• Physical media type and bandwidth (shared or dedicated).

Examples of Access Networks

• DSL (Digital Subscriber Line): Uses existing phone lines to transmit data and voice, with varied upstream and downstream transmission rates.
• Cable Network: Uses cable TV infrastructure to transmit data. Uses frequency division multiplexing (FDM).
• Hybrid Fiber Coax (HFC): Combines fiber optic and coaxial cable technologies for high-speed data transmission.
• Wireless LANs: Internal to buildings via wireless access points.
• Wide-area Wireless Access: Mobile cellular networks (3G, 4G, LTE) extending over broader areas.
• Enterprise Access (Ethernet): Used in companies and university networks, using switches for connection.

How Loss and Delay Occur

• Packet queues in router buffers.
• Packet arrival rate exceeding output link capacity.
• Packets queue up, waiting their turn to be transmitted which causes delay.

Four Sources of Packet Delay

• Transmission: L/R (bits/packet length divided by link bandwidth).
• Propagation: d/s (distance divided by propagation speed).
• Nodal Processing: Checking bits, determining output link.
• Queueing: Waiting in buffer for transmission.

Caravan Analogy

• Illustrates packet propagation delays and queues.

Queueing Delay (Revisited)

• Average delay influenced by traffic intensity (La/R).
• Relationship with traffic intensity and average queueing delay, small for La/R approaching 0. Large for La/R as it approaches 1 and becomes infinite when La/R is greater than 1.

"Real" Internet Delays and Routes

• Traceroute program measures delay.
• Routes packets through intermediate routers.

Packet Loss

• Queueing buffering preceding a link has finite capacity.
• Packets arriving at a full queue are dropped.
• Lost packets may need retransmission.

Throughput

• Rate at which bits are transferred between sender and receiver.
• Instantaneous and average throughput rates.
• Bottleneck link constrains end-end throughput.
• Per-connection end-end throughput affected by limited bandwidth or contention with other connections.

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