Networking glossary

Curated terms for the REBASH Networking course book.

• ACL — Access Control List; permit/deny rules on firewalls, routers, or security groups.
• ARP — Address Resolution Protocol; maps an IPv4 address to a MAC address on a LAN.
• ASN — Autonomous System Number; identity of a network on the public Internet (BGP).
• BGP — Border Gateway Protocol; routing protocol between autonomous systems.
• CIDR — Classless Inter-Domain Routing; prefix notation such as 10.0.0.0/24.
• DHCP — Dynamic Host Configuration Protocol; assigns IP address, gateway, and DNS to clients.
• DNS — Domain Name System; maps names to addresses (and other records).
• egress — Traffic leaving a network, VPC, or host toward an outside destination.
• firewall — Filter that allows or denies traffic by policy (host or network).
• gateway — Next hop that forwards traffic out of a subnet (default route).
• HTTP / HTTPS — Application protocols for the web; HTTPS adds TLS encryption.
• ICMP — Internet Control Message Protocol; used by tools such as ping and some path errors.
• ingress — Traffic entering a network, VPC, service, or Kubernetes Ingress resource.
• IP — Internet Protocol; addressing and forwarding at the network layer (IPv4/IPv6).
• LAN — Local Area Network; typically a switched Ethernet segment or VLAN.
• latency — Time delay for a packet or request to travel (one-way or round-trip).
• load balancer — Distributes connections or requests across multiple backends.
• MAC address — Hardware address on an Ethernet interface (Layer 2).
• MTU — Maximum Transmission Unit; largest packet/frame payload a link accepts.
• NAT — Network Address Translation; rewrites addresses/ports (often private to public).
• OSI model — Seven-layer reference model for describing network functions.
• packet — Unit of data at the network/transport stack (context-dependent).
• port — 16-bit transport endpoint number used by TCP and UDP.
• reverse proxy — Proxy that terminates client traffic and forwards to upstream servers.
• route — Rule that decides the next hop for a destination prefix.
• RTT — Round-Trip Time; latency for a request and its response.
• security group — Cloud firewall rules attached to instances or ENIs (vendor term).
• subnet — Contiguous block of addresses within a larger network or VPC.
• TCP — Transmission Control Protocol; reliable, connection-oriented transport.
• TLS — Transport Layer Security; encrypts application traffic (HTTPS, and others).
• TTL — Time To Live; hop limit on IP packets, or cache lifetime on DNS records.
• UDP — User Datagram Protocol; connectionless transport without built-in reliability.
• VLAN — Virtual LAN; Layer-2 segmentation on a switched network.
• VPC — Virtual Private Cloud; isolated virtual network in a cloud provider.
• VPN — Virtual Private Network; encrypted tunnel between networks or users.
• VXLAN — Virtual Extensible LAN; overlay encapsulation common in cloud and Kubernetes.
• WAN — Wide Area Network; links sites or regions across longer distances.