Intro to computing networks midterm flash1

#midterm

What is the Internet?

A network of networks, connecting millions of devices using protocols.

What is a Protocol?

A set of rules that define format and order of messages sent and received among network entities; and action taken on message transmission or reciept. (e.g., TCP, HTTP, DNS)

Access Networks and Physical Media

The means by which end devices connect to the Internet. Examples:

• Wired: DSL, Cable, Fiber Optics.

• Wireless: WiFi, LTE, 5G.

• Physical Media: Twisted pair, coaxial cable, fiber optics, radio waves.

Packet Switching

• Data is broken into packets and sent independently.

• Used in the Internet (TCP/IP).

Circuit Switching

• A dedicated communication path is established before data transmission.

• Used in traditional telephone networks.

Multiplexing Methods

• FDM (Frequency Division Multiplexing): Different channels use different frequencies.

• TDM (Time Division Multiplexing): Different channels share the same frequency but take turns in time slots.

Throughput

Actual rate (bits/time unit) at which bits are transferred between sender/receiver

(Network Performance Metrics) Throughput Calculation

• Instantaneous Throughput: Rate at a specific time.

• Average Throughput: Rate over a period of time.

(Network Performance Metrics) Sources of Delay

• Processing Delay: Time taken to check for errors.

• Queuing Delay: Time spent waiting in a router queue.

• Transmission Delay: Time required to push the data onto the link.

• Propagation Delay: Time for a signal to travel from source to destination.

Layers of OSI Model

• Physical: Bits on the wire.

• Data Link: MAC addresses, Ethernet, WiFi.

• Network: Routing (IP).

• Transport: End-to-end communication (TCP/UDP).

• Session: Manages sessions.

• Presentation: Encryption, compression.

• Application: User applications (HTTP, FTP, Email).

Encapsulation

Process of wrapping data with necessary protocol information as it moves through OSI layers.

Client-Server vs. P2P Architecture

• Client-Server: Centralized server provides services (e.g., Web browsing).

• P2P: Peers communicate directly without a central server (e.g., BitTorrent).

Process & Sockets

• Sockets allow communication between applications over a network.

• Identified by: IP Address + Port Number.

Transport Services

• TCP (Transmission Control Protocol): Reliable, connection-oriented.

• UDP (User Datagram Protocol): Unreliable, fast, connectionless.

Persistent vs. Non-Persistent HTTP

• Non-Persistent: A new TCP connection for each object.

• Persistent: Uses the same TCP connection for multiple objects.

HTTP Methods

• GET: Request data.

• POST: Submit data.

• HEAD: Get metadata.

• PUT: Upload data.

• DELETE: Remove data.

HTTP Status Codes

• 200 OK: Successful request.

• 301 Moved Permanently: Resource has a new URL.

• 400 Bad Request: Client-side error.

• 404 Not Found: Page not found.

• 500 Internal Server Error: Server-side error.

Cookies

Small pieces of data stored in the browser to track user sessions.

Web Caching

Stores frequently accessed web pages to improve load times and reduce traffic.

File Transfer Protocol (FTP)

Uses two connections:

• Control connection (port 21): Sends commands.

• Data connection (port 20): Transfers files.

SMTP (Simple Mail Transfer Protocol)

Used for sending emails.

POP3 (Post Office Protocol v3)

Downloads emails and deletes them from the server.

IMAP (Internet Message Access Protocol)

Allows access to emails without downloading them.

Domain Name System (DNS)

Translates domain names into IP addresses.

DNS Hierarchy

Root DNS Servers → TLD (Top-Level Domain) Servers → Authoritative DNS Servers.

DNS Records:

A - IP Address Mapping.

CNAME - Alias Name.

MX - Mail Server.

DDoS (Distributed Denial of Service)

Overwhelms a server.

Man-in-the-Middle Attack

Intercepts communication.

Packet Sniffing

Captures unencrypted data.

Encryption

Protects data from being read by attackers

Firewalls

Blocks unauthorized access.

network edge

hosts: clients and servers

servers often in data centers

access networks, physical media

wired, wireless communication links

network core

interconnected routers

network of networks

bit

propagates between transmitter/receiver pairs

physical link

what lies between transmitter & receiver

guided media

signals propagate in solid media: copper, fiber, coax

unguided media

signals propagate freely, e.g., radio

twisted pair (TP)

two insulated copper wires

Category 5: 100 Mbps, 1Gpbs Ethernet

Category 6: 10Gbps

coaxial cable

two concentric copper

conductors

• bidirectional

• broadband:

– multiple channels on cable

– HFC

fiber optic cable

glass fiber carrying light pulses, each pulse a bit

high-speed operation:

-high-speed point-to-point

transmission (e.g., 10’s-100’s Gpbs transmission rate)

low error rate:

-repeaters spaced far apart

-immune to electromagnetic noise