--- title: "Backbone and number resource management hierarchy" subject: "Internet and Intranet" chapter: 1 key: "semester_8/internet_and_intranet:backbone-number-resources-hierarchy" source: https://www.bctengineer.com/q/semester_8/internet_and_intranet/backbone-number-resources-hierarchy site: BCT Engineering --- # Backbone and number resource management hierarchy Internet and Intranet · Chapter 1: Introduction - Asked in: 2074 Magh, 2+8 marks - Answer checked by Claude Opus 5.5 (high effort) on 2026-10-14 - Page: https://www.bctengineer.com/q/semester_8/internet_and_intranet/backbone-number-resources-hierarchy - Whole chapter: https://www.bctengineer.com/md/semester_8/internet_and_intranet/chapter-1 ## Question What is internet backbone network? Explain the hierarchical structure for management of internet number resources. ## Short answer The backbone is the high-capacity core interconnecting major networks. IP addresses and ASNs are managed hierarchically: IANA → Regional Internet Registries (e.g. APNIC) → National/Local Internet Registries (ISPs) → end users. This ensures global uniqueness, efficient allocation, and route aggregation. ## Answer #### Internet backbone network The **Internet backbone** is the high-capacity core of the Internet: the principal fibre routes (terrestrial and submarine) and the powerful core routers operated by Tier-1 and large Tier-2 ISPs. It interconnects regional and national networks at IXPs and through private peering, carries long-distance traffic at 100 Gbps and above, and uses BGP to exchange routes between autonomous systems. #### Hierarchy for management of Internet number resources Number resources are IP addresses (IPv4/IPv6) and Autonomous System Numbers (ASNs). They are managed in a top-down hierarchy so that every address is unique worldwide and can be aggregated for routing. ```text IANA (global pool, under ICANN) | +------+-----+-----+------+ AFRINIC APNIC ARIN LACNIC RIPE NCC <- 5 RIRs | NIRs (e.g. JPNIC, CNNIC, KRNIC, TWNIC) | LIRs = ISPs / large organisations | End users (customers) ``` 1. **IANA:** holds the unallocated global pool. It allocates large blocks (IPv4 /8, IPv6 /12) and ASN ranges to the Regional Internet Registries according to global policy. The IANA IPv4 pool was exhausted in February 2011. 2. **RIRs:** five registries, each for one region (AFRINIC for Africa, APNIC for Asia-Pacific, ARIN for North America, LACNIC for Latin America and Caribbean, RIPE NCC for Europe, Middle East and Central Asia). They allocate to NIRs and LIRs, keep the WHOIS database and run policy development through open community processes. 3. **NIRs (National Internet Registries):** exist in some countries, e.g. Japan, China, Korea, Taiwan, India (IRINN). They serve ISPs in their country on behalf of the RIR. 4. **LIRs (Local Internet Registries):** usually ISPs, which receive blocks (e.g. IPv6 /32) from the RIR or NIR and assign smaller blocks to customers (e.g. IPv6 /48 per site, or a single IPv4 /24). 5. **End users:** organisations and individuals who use the assigned addresses. In Nepal there is no NIR, so Nepali ISPs obtain IP blocks and ASNs directly from **APNIC** as members. The hierarchy supports **aggregation**, because each ISP's customers fall under one prefix, which keeps the global routing table small. ## Check yourself The answer's key points as multiple-choice questions, with the correct option and why. 1. Which describes the Internet backbone correctly? A. A low-speed access network for end users B. The principal fibre routes and core routers of Tier-1 and large Tier-2 ISPs that interconnect networks at IXPs and via private peering, using BGP C. The hierarchy of IANA and RIRs D. A private intranet of a large company Answer: B. The backbone is the high-capacity core carrying long-distance traffic at 100 Gbps and above, using BGP between autonomous systems. (Key point: Backbone definition) 2. What is the correct order of the number resource management hierarchy? A. RIRs, IANA, LIRs, NIRs, end users B. IANA, LIRs, RIRs, NIRs, end users C. End users, LIRs, NIRs, RIRs, IANA is not part of it D. IANA, RIRs, NIRs (optional), LIRs (ISPs), end users Answer: D. IANA gives large blocks to the five RIRs, which allocate to NIRs and LIRs (ISPs), who assign to end users. (Key point: Top-down hierarchy order) 3. How do Nepali ISPs obtain IP blocks and ASNs? A. Through a Nepal NIR B. Directly from APNIC as members, since Nepal has no NIR C. From IANA directly D. From their Tier-1 upstream provider only Answer: B. There is no NIR in Nepal, so ISPs act as LIRs and get resources directly from APNIC. (Key point: Nepal's source of addresses) 4. Why does the hierarchy keep the global routing table small? A. Each ISP's customers fall under one prefix, so one route entry covers them all B. Every customer receives a block from IANA C. Addresses are reused in different regions D. BGP is not used for hierarchical blocks Answer: A. Hierarchical allocation lets an ISP advertise a single aggregate prefix for all its customers. (Key point: Aggregation) ## Related in Internet and Intranet - [Teleports and number resource hierarchy](https://www.bctengineer.com/question.md?key=semester_8%2Finternet_and_intranet%3Ateleports-number-resources-hierarchy) — Internet and Intranet, chapter 1 - [Internet backbone and ecosystem components](https://www.bctengineer.com/question.md?key=semester_8%2Finternet_and_intranet%3Ainternet-backbone-ecosystem) — Internet and Intranet, chapter 1 - [Redundant hierarchical network design for bank](https://www.bctengineer.com/question.md?key=semester_8%2Finternet_and_intranet%3Aredundant-network-bank-four-departments) — Internet and Intranet, chapter 5 - [Intranet, Internet, Extranet comparison and resources](https://www.bctengineer.com/question.md?key=semester_8%2Finternet_and_intranet%3Aintranet-internet-extranet-compare) — Internet and Intranet, chapter 1 - [N-tier challenges and tiered ISP backbone](https://www.bctengineer.com/question.md?key=semester_8%2Finternet_and_intranet%3An-tier-challenges-tiered-isp) — Internet and Intranet, chapter 1 ## Related in other subjects - [Natural resource management approaches and sustainability](https://www.bctengineer.com/question.md?key=semester_6%2Fenergy_resources%3Aenvironment-development-society-resource-management) — Energy Resources, chapter 8 - [Internet structure: repeater, bridge, router, gateway](https://www.bctengineer.com/question.md?key=semester_8%2Ftelecommunications%3Ainternet-structure-devices) — Telecommunications, chapter 8 - [Complex number multiplication using structure](https://www.bctengineer.com/question.md?key=semester_1%2Fcomputer_programming%3Astruct-complex-multiply) — Computer Programming, chapter 8 - [Cache management; direct vs associative address structure](https://www.bctengineer.com/question.md?key=semester_5%2Fcomputer_organization_and_architecture%3Adirect-vs-assoc-address) — Computer Organization and Architecture, chapter 6