Computer Networking: Chapters 1 & 2 Overview

Vocabulary practice flashcards covering fundamental networking concepts, protocol layers, Internet edge and core architectures, delay calculations, security principles, and application-layer models from COMP 2100 lectures.

Host (End System)

A computing device connected to the Internet (such as a PC, server, smartphone, or laptop) that runs network application programs.

Transmission Rate (Bandwidth)

The maximum capacity of a communication link to carry data, measured in bits per second ($\text{bps}$).

Packet Switch

An intermediate network hardware device, such as a router or link-layer switch, that forwards chunks of data known as packets across communication links.

Request for Comments (RFC)

Official technical standard and specification documents defining Internet protocols, published and maintained by the Internet Engineering Task Force (IETF).

Internet Engineering Task Force (IETF)

The principal international standards organization responsible for developing and promoting open Internet standards and protocols.

Network Protocol

A formal set of rules that defines the format, ordering, and syntax of messages sent and received among network entities, as well as the actions taken on message transmission or receipt.

Access Network

The network and physical communication infrastructure (e.g., DSL, cable, fiber, cellular) that physically connects an end system to the edge router of its service provider.

Guided Media

Physical transmission media where signals propagate within solid physical conductors, such as copper twisted-pair, coaxial cable, or fiber-optic cable.

Unguided Media

Wireless transmission media where electromagnetic signals propagate freely through the atmosphere or outer space without a physical conductor, such as radio, microwave, or satellite links.

Circuit Switching

A networking method in which dedicated transmission resources and an end-to-end communication channel are reserved exclusively between two nodes before communication begins.

Packet Switching

A networking approach where hosts break application-layer messages into discrete packets that share communication links dynamically and are transmitted at full link capacity.

Store-and-Forward Transmission

The packet-switching mechanism where an intermediate packet switch must completely receive all bits of a packet before it can begin transmitting the first bit onto the outbound link.

Packet Transmission Delay ($d_{\text{trans}}$)

The amount of time required to push all of a packet's bits into the communication link, expressed as $d_{\text{trans}} = \frac{L}{R}$, where $L$ is the packet length in bits and $R$ is the link transmission rate in bits per second.

Forwarding

The router-local operation of transferring an arriving packet from an input link interface to the appropriate output link interface based on the destination address and a local forwarding table.

Routing

The network-wide control process that calculates and determines the end-to-end routes taken by packets from source to destination using routing algorithms.

Internet Exchange Point (IXP)

A physical meeting infrastructure that allows multiple independent Internet service providers (ISPs) to interconnect and exchange traffic directly.

Peering Link

A direct connection between two commercial ISPs allowing them to exchange customer traffic directly without routing through upstream transit providers.

Point of Presence (POP)

A group of one or more routers within a provider's network where customer ISPs and subscriber networks connect to the provider backbone.

Tier-1 ISP

A major global commercial network provider (such as Level 3, Sprint, AT&T, or NTT) that can reach every other network on the Internet solely through free peering arrangements without buying transit.

Nodal Processing Delay ($d_{\text{proc}}$)

The time required by a router to inspect a packet's header, check for bit-level errors, and determine the appropriate outbound interface; typically less than a millisecond.

Queuing Delay ($d_{\text{queue}}$)

The time a packet spends waiting in a router's buffer queue before it can be transmitted onto the outgoing link, which varies according to network congestion.

Propagation Delay ($d_{\text{prop}}$)

The time required for a bit to physically travel across a transmission medium from one node to the next, calculated as $d_{\text{prop}} = \frac{d}{s}$, where $d$ is distance and $s$ is propagation speed ($\approx 2 \times 10^8\,\text{m/s}$).

Traffic Intensity

The dimensionless ratio $\frac{L \cdot a}{R}$, where $L$ is packet length, $a$ is average packet arrival rate, and $R$ is link transmission rate; as this ratio approaches $1$, queuing delay rises rapidly toward infinity.

Packet Loss

The dropping of arriving packets by a router when its finite memory buffer (queue) becomes completely filled due to incoming traffic exceeding link capacity.

Throughput

The actual rate (measured in bits per second) at which data is successfully transferred from a sender to a receiver across a network path.

Bottleneck Link

The communication link on an end-to-end path that has the lowest transmission capacity, thereby constraining the overall throughput of the connection.

Traceroute

A diagnostic utility that determines the path and round-trip delay to a destination by dispatching three probe packets to each successive router along the route.

Encapsulation

The layering process where each protocol layer adds its own header information (such as $H_t$, $H_n$, or $H_l$) to the data payload received from the layer directly above it.

Application Layer

The top layer of the Internet protocol stack responsible for supporting user network applications and services (e.g., HTTP, SMTP, FTP, DNS).

Transport Layer

The protocol layer responsible for providing process-to-process data communication between end systems (e.g., TCP, UDP).

Network Layer

The protocol layer responsible for host-to-host routing of datagrams across multiple intermediate links and networks from source to destination (e.g., IP, routing protocols).

Link Layer

The protocol layer responsible for transferring data frames between directly adjacent network elements across an individual link (e.g., Ethernet, WiFi 802.11, PPP).

Physical Layer

The lowest protocol layer responsible for moving individual raw bits across the physical medium connecting transmitter and receiver pairs.

Presentation Layer

The OSI model layer that allows applications to interpret the meaning of data by providing services such as encryption, compression, and machine-specific syntax conversion.

Session Layer

The OSI model layer responsible for managing, checkpointing, synchronizing, and recovering active communication sessions between processes.

Denial of Service (DoS)

An attack where malicious actors render a network resource, server, or link unavailable to legitimate users by overwhelming it with bogus traffic or requests.

Packet Sniffing

A passive security attack where a promiscuous network interface reads and records all packets traversing a shared or broadcast communication medium.

IP Spoofing

A malicious injection technique in which an attacker generates and transmits packets containing a forged source IP address to conceal identity or impersonate another system.

ARPAnet (1969 Initial Topology)

The pioneering four-node packet-switching network operational in 1969, linking node computers at UCLA, Stanford Research Institute (SRI), UC Santa Barbara (UCSB), and the University of Utah.

Cerf and Kahn's Internetworking Principles

Architectural guidelines formulated in 1974 defining the modern Internet: network minimalism and autonomy, best-effort service, stateless routers, and decentralized control.

Client-Server Architecture

An application design pattern with an always-on host with a fixed IP address (server) that services incoming requests from many intermittently active end systems (clients).

Peer-to-Peer (P2P) Architecture

A distributed application structure featuring arbitrary, direct communication between pairs of intermittently connected hosts (peers) without requiring dedicated central servers.

Client Process

The application-level program execution instance that initiates network communication by sending a request.

Server Process

The application-level program execution instance that passively waits on a host to be contacted by client processes.

Socket

The software interface and communication endpoint (analogous to a door) through which an application process sends and receives data to and from the network via the transport layer.

Port Number

A 16-bit numerical identifier assigned to an endpoint on a host allowing the transport layer to route incoming traffic to a specific application process (e.g., port 80 for HTTP, port 25 for SMTP).

Transmission Control Protocol (TCP)

A reliable, connection-oriented transport-layer protocol providing in-order byte-stream delivery, flow control, and network congestion control.

User Datagram Protocol (UDP)

A lightweight, connectionless transport-layer protocol providing unacknowledged, best-effort datagram delivery without reliability guarantees, flow control, or congestion control.

Secure Sockets Layer (SSL)

An application-layer security mechanism that augments TCP by providing cryptographic encryption, data integrity, and endpoint authentication for socket data streams.