Networking Concepts Flashcards

These flashcards cover important concepts in networking, including protocols, architectures, and functions within the Internet and its layers.

What is the Internet?

A network of networks that connects millions of private, public, academic, business, and government networks.

What is a protocol?

A set of rules defining message format, order, and actions taken upon message transmission and receipt.

What are the main components of the Internet’s edge?

Hosts (clients and servers), access networks, and physical media.

What are the main types of access networks?

Cable (HFC), DSL, Fiber, Wi-Fi, and Cellular (4G/5G).

What is a packet?

A chunk of data sent from a host across a network; consists of header and payload.

Define packet switching.

Data is broken into packets that are sent independently through routers and reassembled at the destination.

Define circuit switching.

Dedicated resources (bandwidth) are reserved for a connection before data transfer.

Compare packet switching vs. circuit switching.

Packet switching allows resource sharing and is efficient for bursty data; circuit switching reserves resources and is predictable but less efficient.

What is the network core?

The mesh of interconnected routers that forward packets from source to destination.

What causes delay in packet networks?

Processing, queuing, transmission, and propagation delays.

What is throughput?

The rate (bits per second) at which bits are transferred between sender and receiver.

What are Tier-1 ISPs?

Large, well-connected networks providing global Internet connectivity (e.g., AT&T, NTT, Level 3).

What is the purpose of the Application Layer?

It provides network services directly to end-user applications.

What are two main application architectures?

Client-server and peer-to-peer (P2P).

Define client-server model.

A server is always on with a fixed IP, clients connect to it and request services.

Define peer-to-peer (P2P).

End systems communicate directly, sharing resources without always-on servers.

What is a socket?

The interface between an application process and the transport layer.

What two pieces of information identify a process on the network?

IP address and port number.

What does the application-layer protocol define?

Message types, syntax, semantics, and communication rules.

What are the main transport protocols used by applications?

TCP (reliable, connection-oriented) and UDP (unreliable, connectionless).

What applications typically use TCP?

HTTP, FTP, SMTP, IMAP.

What applications typically use UDP?

DNS, VoIP, streaming, gaming.

What is HTTP?

HyperText Transfer Protocol — the protocol for transferring web content.

What is the difference between persistent and non-persistent HTTP?

Non-persistent uses a new TCP connection per object; persistent reuses one connection for multiple objects.

What are cookies used for?

Maintaining state between HTTP requests (e.g., sessions, shopping carts).

What is a Web cache?

A server that stores frequently accessed web objects to reduce latency and bandwidth use.

What is the main function of SMTP?

Transfers email messages between mail servers.

What is the difference between SMTP and HTTP?

SMTP is a push protocol using persistent connections; HTTP is a pull protocol.

What are IMAP and POP3 used for?

Retrieving emails from mail servers.

What is DNS?

The Domain Name System — translates human-readable domain names to IP addresses.

What are the types of DNS servers?

Root, Top-Level Domain (TLD), authoritative, and local DNS servers.

What is a DNS record (RR)?

A 4-tuple: (Name, Value, Type, TTL).

What is a CDN (Content Delivery Network)?

A distributed system of servers that deliver content based on user location for faster access.

What is the main role of the transport layer?

Provides logical communication between processes across networked hosts.

What are the two Internet transport protocols?

UDP and TCP.

What is multiplexing/demultiplexing?

Directing data from multiple applications to the correct sockets using port numbers.

What is UDP?

A connectionless, unreliable protocol that provides best-effort data delivery.

What applications benefit from UDP?

Real-time apps like VoIP, video streaming, and online games.

What is the purpose of the UDP checksum?

Detects bit errors in transmitted segments.

What is reliable data transfer (RDT)?

Ensures all data is delivered correctly and in order.

What is stop-and-wait ARQ?

Sender transmits one packet, waits for ACK before sending next.

What is Go-Back-N?

Sender can send up to N unacknowledged packets; upon error, retransmits from the failed packet onward.

What is Selective Repeat?

Only retransmits packets that were lost or corrupted, improving efficiency.

What are TCP features?

Reliable, ordered, byte-stream transfer with congestion and flow control.

What does TCP’s sequence number represent?

The byte number of the first byte in the segment’s data field.

What is a cumulative ACK?

Acknowledges all bytes up to a certain number as received.

What is TCP flow control?

Prevents sender from overwhelming receiver by using the receiver’s advertised window size.

What is congestion control?

Mechanism to prevent network overload by adjusting sending rate.

What are the TCP congestion control phases?

Slow start, congestion avoidance, fast retransmit, and fast recovery.

What does RTT stand for?

Round Trip Time — the time for a signal to travel from sender to receiver and back.

How is TCP timeout calculated?

Using EstimatedRTT and deviation (DevRTT) via exponential weighted moving average (EWMA).