Network Glossary
ISP technical terms explained in plain language — from engineers who operate provider networks daily.
AS — Autonomous System
A group of IP networks under a single administration, identified by an ASN. Every ISP needs at least one AS to advertise its routes via BGP.
Anycast — Anycast Routing
Multiple servers share the same IP from different locations; the network delivers each packet to the closest one. Common in DNS (8.8.8.8, 1.1.1.1) and CDNs.
BGP — Border Gateway Protocol
The routing protocol between Autonomous Systems — what makes the internet work between ISPs. Misconfigured BGP can take you off the internet or leak someone else's routes.
B-RAS — Broadband Remote Access Server
Server that terminates subscriber PPPoE sessions and routes traffic. Huawei NE8000/NE40, Juniper MX, Cisco ASR. Single point of failure without redundancy.
CGNAT — Carrier-Grade NAT
Large-scale NAT that lets you share one public IPv4 across many subscribers. Cheaper than buying IPv4, but breaks some services (P2P, port forwarding, gaming).
DNS — Domain Name System
Translates names (rasys.net) into IPs (200.x.x.x). ISPs need to run their own resolvers or point to public ones. Slow DNS is the first thing customers complain about.
GPON — Gigabit Passive Optical Network
Passive FTTH technology (no power in the path). One OLT serves up to 128 ONUs per port via optical splitter. Dominant standard for residential fiber in Brazilian ISPs.
IPv6 — Internet Protocol version 6
Next-generation IP with 128-bit addresses. Solves IPv4 scarcity. ISPs without IPv6 lose competitiveness — Google and Netflix penalize networks missing dual-stack.
IX — Internet Exchange Point
Location where ISPs interconnect directly without paying for IP transit. In Brazil, IX.br has PoPs in major cities. Peering at IX cuts latency and cost.
MPLS — Multiprotocol Label Switching
Switches packets based on labels instead of IP destination. Used in large backbones to build L2/L3 VPNs and perform traffic engineering. Common in multi-PoP ISPs.
OLT — Optical Line Terminal
Central device of a GPON/EPON FTTH network. Connects the ISP backbone to the ONUs (subscriber side). Huawei MA5800, ZTE C300, FiberHome AN5516 are common.
OSPF — Open Shortest Path First
Interior gateway protocol based on link-state. Calculates shortest paths inside the ISP's AS. Faster than RIP, simpler than IS-IS.
Peering — BGP Peering
Direct route exchange between two ASes without paying transit. Can be bilateral (direct agreement) or multilateral (via IX). Cuts bandwidth cost and improves latency.
PPPoE — Point-to-Point Protocol over Ethernet
Authentication protocol still dominant in Brazilian ISPs. Client authenticates via login/password over a PPP session encapsulated in Ethernet. The B-RAS terminates the session.
RADIUS — Remote Authentication Dial-In User Service
Central authentication, authorization and accounting (AAA) system that validates PPPoE login, enforces contracted speed and tracks online time. FreeRADIUS is the most common base.
Want to dig deeper?
Rasys has been operating ISP networks in Brazil for over 5 years. If any of these terms is a headache in your operation, talk to us — initial assessment is free.