Networking Exam Review Flashcards (Chapters 1–4)

Vocabulary practice flashcards based on Networking Exam Review Chapters 1–4.

Host

An end system running applications at the network edge.

Network Protocol

A specification defining message formats, message ordering, and actions taken when messages or other events occur.

Network Edge

Hosts and their applications located at the periphery of the network.

Access Network

The connection infrastructure that links hosts toward their first router.

Network Core

The mesh of interconnected routers and links that carries packets between networks.

Transit

A service model where a network purchases reachability through an upstream provider network.

Peering

Direct traffic exchange between networks without paying an intermediate transit provider.

Internet Exchange Point (IXP)

A shared physical infrastructure where multiple networks interconnect to exchange traffic.

Packet Switching

A switching method where network capacity is shared on demand and data is divided into packets.

Circuit Switching

A switching method where dedicated network capacity is reserved for the duration of a connection.

Frequency Division Multiplexing (FDM)

A multiplexing technique that separates channels across dedicated frequency bands.

Time Division Multiplexing (TDM)

A multiplexing technique that allocates channels across recurring time slots.

Store-and-Forward

A packet-switching requirement stating that an entire packet must arrive at a node before it can be transmitted onto the next link.

Nodal Delay

The total delay experienced by a packet at a router node, equal to processing delay plus queueing delay plus transmission delay plus propagation delay.

Transmission Delay

The amount of time required to push all of a packet's bits onto a link, calculated as $\frac{L}{R}$.

Propagation Delay

The time required for a bit or signal to travel through the physical medium from sender to receiver, calculated as $\frac{d}{s}$.

Traffic Intensity

A unitless measure of offered load relative to link capacity, calculated as $\frac{aL}{R}$ where $a$ is packet arrival rate, $L$ is packet length, and $R$ is transmission rate.

Bottleneck Link

The path link or resource that restricts the overall sustained end-to-end transmission rate.

Goodput

The rate at which useful application data is delivered to the destination, excluding protocol headers and duplicate retransmissions.

Encapsulation

The process of wrapping higher-layer data with lower-layer control headers and optional trailers.

Socket

The application-level software interface through which a process sends and receives messages from the transport layer.

Stateless Protocol

A protocol, such as HTTP, in which requests do not inherently require protocol-level memory of prior requests.

Persistent HTTP

An HTTP execution mode where multiple requests and responses share a single persistent TCP connection.

Nonpersistent HTTP

An HTTP execution mode where a separate TCP connection is created and closed for each requested object.

HTTP Pipelining

A mechanism where a client sends multiple HTTP requests over a persistent connection without waiting for each earlier response.

Conditional GET

An HTTP request mechanism that allows a cache to verify whether a stored representation is up-to-date with the origin server.

Local Resolver

A local DNS server that handles a host's recursive queries by making iterative requests to the global DNS hierarchy.

Authoritative DNS Server

A DNS server that maintains the official, definitive resource records for a specific domain or zone.

DNS Resource Record (RR)

A four-tuple entry in a DNS database containing Name, Value, Type, and Time To Live (TTL).

CNAME Record

A DNS resource record mapping an alias hostname to its canonical (official) hostname.

MX Record

A DNS resource record specifying the mail exchanger host for a given domain.

DNSSEC

Security extensions for DNS that authenticate DNS record data and protect its integrity without providing encryption.

Content Delivery Network (CDN)

A globally distributed network of servers that caches and delivers content near users to reduce delay and origin load.

Multiplexing

The transport-layer function of gathering data from multiple application sockets and encapsulating it with headers for network transmission.

Demultiplexing

The transport-layer function of delivering incoming segments to the appropriate application socket based on header fields.

Stop-and-Wait

A reliable transport protocol mode where the sender sends one packet and pauses until receiving an ACK before sending the next.

Go-Back-N (GBN)

A pipelined reliable transfer protocol that uses cumulative acknowledgments and retransmits all unacknowledged outstanding packets starting from the oldest missing packet upon timer expiration.

Selective Repeat (SR)

A pipelined reliable transfer protocol that individually acknowledges received packets, buffers out-of-order data, and retransmits only missing timed-out packets.

Cumulative Acknowledgment

An acknowledgment scheme where an ACK number informs the sender that all bytes up to that sequence number have been correctly received in order.

Maximum Segment Size (MSS)

The maximum payload size of application data that a TCP segment can carry, excluding TCP and IP headers.

Fast Retransmit

A TCP mechanism that triggers a segment retransmission upon receiving three duplicate ACKs before the retransmission timer expires.

Receive Window (rwnd)

A TCP header field indicating the amount of available buffer space at the receiver to enforce flow control.

Congestion Window (cwnd)

A state variable maintained by a TCP sender that limits the amount of outstanding unacknowledged data on the network for congestion control.

Slow Start

The initial TCP congestion control phase where cwnd starts at $1\,MSS$ and doubles every RTT until reaching ssthresh.

Additive Increase Multiplicative Decrease (AIMD)

A congestion control principle where cwnd increases linearly by $1\,MSS$ per RTT in congestion avoidance and decreases by half upon congestion detection.

Explicit Congestion Notification (ECN)

A network feature allowing intermediate routers to mark IP headers with congestion flags so endpoints can adjust rates without packet loss.

QUIC

A transport protocol running over UDP that provides secure, reliable stream multiplexing and reduced handshake latency.

Forwarding

A router data-plane operation that transfers a packet from an incoming interface to an outgoing interface according to a local lookup table.

Routing

A router control-plane process that computes end-to-end paths across the network to generate forwarding tables.

Head-of-Line (HOL) Blocking

A performance condition where a queued packet at the front of a buffer delays subsequent packets behind it, even if their path or destination is available.

Bufferbloat

High queueing delay caused by oversized router buffers retaining large numbers of backlogged packets under persistent load.

Weighted Fair Queueing (WFQ)

A router scheduling algorithm that serves active traffic queues in proportional turns based on configured weights.

Classless Inter-Domain Routing (CIDR)

An IP addressing convention using prefix notation ($/x$) to flexibly allocate IP address blocks and enable route aggregation.

Longest Prefix Matching

A forwarding table lookup rule that selects the matching route entry with the longest (most specific) subnet mask prefix.

Ternary Content-Addressable Memory (TCAM)

Specialized router hardware memory that supports high-speed lookup across binary states ($0$, $1$) and wildcard (don't-care) masks.

Dynamic Host Configuration Protocol (DHCP)

A network management protocol that automatically assigns IP addresses, masks, default gateways, and DNS server addresses to hosts using the DORA exchange.

Network Address Translation (NAT)

A technique that maps private IP addresses and transport ports inside a local network to public IP addresses and ports for Internet communication.

Maximum Transmission Unit (MTU)

The maximum size of an IP packet (including header) that can be transmitted on a physical link without fragmentation.

End-to-End Principle

A system design concept stating that network functions should be placed at end systems unless lower layers can implement them completely and correctly.

Middlebox

Any network device intermediate to the end systems that performs functions beyond standard IP packet forwarding, such as firewalls or NATs.