Computer Networks – Comprehensive Vocabulary Review

120 vocabulary flashcards covering major concepts in IP addressing, subnetting, routing, flow control, Ethernet, TCP/UDP, error control, and OSI model as presented in the lecture notes.

IP Address

A 32-bit numerical label assigned to each device connected to a network that uses Internet Protocol for communication.

DNS (Domain Name System)

Service that translates human-readable domain names into IP addresses.

Port Number

16-bit logical address that identifies a specific process or service on a host (e.g., HTTP-80, FTP-21).

Network ID (NID)

The portion of an IP address that identifies the network segment.

Host ID (HID)

The portion of an IP address that identifies an individual host within a network.

Class A Address

IPv4 address range 0.0.0.0 – 127.255.255.255 with default mask 255.0.0.0; first bit 0.

Class B Address

IPv4 address range 128.0.0.0 – 191.255.255.255 with default mask 255.255.0.0; first bits 10.

Class C Address

IPv4 address range 192.0.0.0 – 223.255.255.255 with default mask 255.255.255.0; first bits 110.

Class D Address

IPv4 multicast range 224.0.0.0 – 239.255.255.255; first bits 1110.

Class E Address

IPv4 experimental range 240.0.0.0 – 255.255.255.255; first bits 1111.

Subnet Mask

32-bit number used to partition an IP network into sub-networks by masking host bits.

Subnetting

Process of dividing a network into smaller logical subnets to improve management, routing, or security.

Directed Broadcast

IP packet whose destination is the broadcast address of a remote network (all host bits 1).

Limited Broadcast

Packet sent to 255.255.255.255, received by all hosts on the local network only.

CIDR (Classless Inter-Domain Routing)

IPv4 addressing method that ignores class boundaries and expresses networks as A.B.C.D/PrefixLength.

Slash Notation

CIDR representation indicating the number of fixed network bits after the IP address (e.g., /27).

VLSM (Variable Length Subnet Mask)

Use of different subnet masks within the same network to create subnets of unequal size.

Supernetting

Combining multiple contiguous networks into a larger address block (route aggregation).

ISP

Internet Service Provider; organization that provides Internet access and related services.

Flow Control

Techniques ensuring a sender does not overwhelm a receiver with too much data.

Stop-and-Wait ARQ

Basic reliable protocol where sender transmits a frame and waits for an acknowledgment before sending next.

Sliding Window Protocol

Flow control mechanism allowing multiple outstanding frames within a window size.

Go-Back-N

Sliding window ARQ where, upon error, sender retransmits the erroneous frame and all subsequent ones.

Selective Repeat

Sliding window ARQ where only erroneous or lost frames are retransmitted.

Bandwidth-Delay Product (Pipe Capacity)

Maximum amount of data that can fill the link = Bandwidth × Round-Trip Time.

CSMA/CD

Carrier Sense Multiple Access with Collision Detection; Ethernet medium access method.

Backoff Algorithm

Random wait time after a collision in CSMA/CD, determined by 0–2^k −1 slots.

Token Ring

LAN access method where a token circulates; only the station holding the token may transmit.

Pure ALOHA

Random-access method where stations transmit whenever data is ready, leading to max efficiency 18.4%.

Slotted ALOHA

Improved ALOHA with time slots; max efficiency 36.8%.

Ethernet Preamble

7-byte pattern (10101010…) used to synchronize receivers before frame arrival.

SFD (Start Frame Delimiter)

1-byte 10101011 pattern indicating the start of an Ethernet frame.

MAC Address

48-bit hardware address burned into NIC, displayed in hexadecimal (e.g., 3C:5A:B4:9E:28:1F).

Unicast MAC

MAC address with least-significant bit of first octet 0; targets a single device.

Multicast MAC

MAC address with LSB of first octet 1; targets a group of devices.

Broadcast MAC

FF:FF:FF:FF:FF:FF; addressed to all devices on LAN.

Frame Check Sequence (FCS)

32-bit CRC used by Ethernet to detect transmission errors.

MTU (Maximum Transmission Unit)

Largest packet size that can be sent over a medium without fragmentation.

IP Fragmentation

Splitting an IP datagram into smaller pieces to fit MTU limits of a network.

DF (Don’t Fragment) bit

IP header flag instructing routers not to fragment the packet.

MF (More Fragments) bit

IP header flag set on all fragments except the last to indicate more pieces follow.

Fragment Offset

Field indicating the relative position of a fragment within original datagram in 8-byte units.

TTL (Time To Live)

IP header field limiting hops; decremented by 1 each router; packet discarded at 0.

ARP (Address Resolution Protocol)

Protocol mapping an IP address to its corresponding MAC address on a local network.

RARP

Reverse ARP; maps a MAC address to an IP address (obsolete, replaced by BOOTP/DHCP).

BOOTP

Bootstrap Protocol providing IP configuration to diskless hosts using UDP port 67/68.

DHCP

Dynamic Host Configuration Protocol that dynamically assigns IP addresses with lease times.

ICMP

Internet Control Message Protocol; carries error and diagnostic messages (e.g., Echo Request, TTL Exceeded).

Ping

Utility using ICMP Echo Request/Reply to test reachability and measure round-trip time.

Traceroute

Diagnostic tool sending packets with increasing TTL to discover the path to a destination.

PMTUD (Path MTU Discovery)

Process of discovering the smallest MTU along a path using ICMP ‘Fragmentation Needed’ responses.

Routing Table

Data structure in routers mapping destination networks to next-hop addresses and interfaces.

Distance Vector Routing

Algorithm where routers share vector of distances to networks with neighbors (e.g., RIP).

Count-to-Infinity Problem

Slow convergence issue in distance-vector routing leading to progressively increasing metric loops.

Split Horizon

Technique preventing a router from advertising routes back on the interface from which they were learned.

Link State Routing

Algorithm where routers flood link-state information and compute shortest paths (e.g., OSPF).

Dijkstra’s Algorithm

SPF algorithm used by link-state protocols to build shortest-path trees.

RIP

Routing Information Protocol; distance-vector protocol with hop-count metric and 15-hop limit.

OSPF

Open Shortest Path First; link-state IGP supporting areas and cost metrics.

EIGRP

Enhanced Interior Gateway Routing Protocol; Cisco hybrid routing protocol using Diffusing Update Algorithm.

CIDR Aggregation

Combining multiple subnets into one routing table entry to reduce table size.

TCP (Transmission Control Protocol)

Connection-oriented, reliable transport protocol using sequence numbers, ACKs, and flow control.

UDP (User Datagram Protocol)

Connectionless, unreliable transport protocol with minimal overhead; used for DNS, VoIP, video.

Socket

Endpoint of communication defined by IP address and port number combination.

Three-Way Handshake

TCP connection setup sequence: SYN, SYN-ACK, ACK.

FIN Flag

TCP control bit indicating sender has finished transmitting data.

RST Flag

TCP control bit used to abruptly reset a connection.

PSH Flag

TCP flag requesting immediate delivery of data to the receiving application.

URG Flag

TCP flag indicating urgent data; offset specified by Urgent Pointer.

MSS (Maximum Segment Size)

Largest TCP payload a host is willing to accept, typically MTU − 40 bytes.

TCP Window Size

Field advertising the number of bytes the receiver is currently willing to accept.

Slow Start

TCP congestion-control phase where cwnd doubles each RTT until threshold.

Congestion Avoidance

TCP phase increasing cwnd linearly after slow start until loss is detected.

Fast Retransmit

TCP mechanism retransmitting a segment after receiving three duplicate ACKs.

Fast Recovery

TCP algorithm adjusting cwnd after fast retransmit without entering slow start.

Bandwidth-Delay Product

Amount of data ‘in flight’ equal to link bandwidth multiplied by RTT.

Wrap-Around Time (WAT)

Time for TCP 32-bit sequence numbers to cycle at a given bandwidth.

Checksum

Error-detection value computed over header and data (IP, TCP, UDP).

CRC (Cyclic Redundancy Check)

Polynomial-based error-detection code used in Ethernet frames and other protocols.

Parity Bit

Single bit added to data to make number of 1s even (even parity) or odd (odd parity).

Hamming Distance

Number of differing bits between two codewords; measures error-detecting/correcting capability.

Hamming Code

Error-correcting code that can detect two-bit errors and correct single-bit errors using redundant parity bits.

Stop-and-Wait Efficiency

Throughput = L / (L + 2Tp × Bw), where L is frame length, Tp propagation time.

Capacity of Pipe

Maximum bits that can reside on a link = Bandwidth × Propagation Delay.

TDM (Time Division Multiplexing)

Access method allocating fixed time slots to stations in round-robin order.

Polling

Central controller grants the right to transmit to one station at a time, eliminating wasted slots.

Collision Domain

Network segment where simultaneous transmissions can collide (shared medium).

Broadcast Domain

Set of devices that receive broadcast frames from a device; bounded by routers.

Hub

Multiport repeater operating at physical layer; extends collision domain.

Bridge

Device that connects LAN segments at data-link layer; filters frames using MAC addresses.

Switch

Multi-port bridge with hardware forwarding; each port forms separate collision domain.

Router

Layer-3 device forwarding packets based on IP addresses; separates broadcast domains.

Gateway

Device performing protocol conversion between different network architectures/application layers.

OSI Model

Seven-layer reference model: Physical, Data Link, Network, Transport, Session, Presentation, Application.

Presentation Layer

OSI layer handling syntax translation, encryption, and compression.

Session Layer

OSI layer managing dialog control and synchronization between hosts.

Application Layer

OSI layer providing network services directly to user applications (e.g., HTTP, FTP).

HTTP

Hypertext Transfer Protocol; application protocol for web communication using TCP port 80.

HTTPS

Secure version of HTTP using TLS encryption, TCP port 443.

FTP

File Transfer Protocol; uses TCP ports 21 (control) and 20 (data) for file exchange.