--- title: "IPv6 features, header format, RFC streams" subject: "Internet and Intranet" chapter: 2 key: "semester_8/internet_and_intranet:ipv6-features-header-rfc" source: https://www.bctengineer.com/q/semester_8/internet_and_intranet/ipv6-features-header-rfc site: BCT Engineering --- # IPv6 features, header format, RFC streams Internet and Intranet · Chapter 2: Internet Protocol Overview - Asked in: 2074 Bhadra, 10 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/ipv6-features-header-rfc - Whole chapter: https://www.bctengineer.com/md/semester_8/internet_and_intranet/chapter-2 ## Question List the advanced features of IPv6. Describe IPv6 header format with suitable diagram. Describe internet RFC along with its streams. ## Short answer IPv6 features include 128-bit addresses, fixed 40-byte header, extension headers, no checksum, autoconfiguration, IPsec, flow label, multicast/anycast, and neighbor discovery. Header fields: Version, Traffic Class, Flow Label, Payload Length, Next Header, Hop Limit, 128-bit source/destination. RFC streams are IETF, IAB, IRTF, and independent submission. ## Answer #### Advanced features of IPv6 1. **128-bit address space:** about 3.4 x 10^38 addresses; every device can have a global address, so NAT is not needed. 2. **Simplified fixed header:** 40 bytes with fewer fields, which makes routing faster. 3. **Extension headers:** optional features (routing, fragmentation, authentication, ESP) are in separate headers, chained by Next Header. 4. **No header checksum and no router fragmentation:** less work for routers. 5. **Auto-configuration:** SLAAC and DHCPv6 let hosts configure themselves ("plug and play"). 6. **Built-in security:** IPsec support (AH and ESP) is part of the architecture. 7. **Better QoS:** Traffic Class and 20-bit Flow Label identify packets of one flow. 8. **Multicast and anycast:** broadcast is removed; multicast is more efficient. 9. **Better mobility and aggregation:** Mobile IPv6 and hierarchical addressing reduce routing table size. 10. **Neighbour Discovery:** ICMPv6 replaces ARP and router discovery. 11. **Jumbograms:** packets larger than 64 KB are possible. #### IPv6 header format ```text +---------+-------------+-----------------------+ | Ver (4) | Traffic | Flow Label (20) | | | Class (8) | | +---------+-------------+---------+-------------+ | Payload Length (16) | Next | Hop Limit | | | Hdr (8) | (8) | +-----------------------+---------+-------------+ | Source Address (128 bits) | +-----------------------------------------------+ | Destination Address (128 bits) | +-----------------------------------------------+ ``` - **Version (4 bits):** value 6. - **Traffic Class (8 bits):** priority/DiffServ class. - **Flow Label (20 bits):** identifies packets of the same flow for special handling. - **Payload Length (16 bits):** size of data (and extension headers) after the base header. - **Next Header (8 bits):** type of the next header (6 = TCP, 17 = UDP, 58 = ICMPv6, 44 = fragment). - **Hop Limit (8 bits):** decremented by each router; packet is dropped at 0 (replaces TTL). - **Source and Destination Address (128 bits each).** Total = 40 bytes. #### Internet RFC and its streams A **Request for Comments (RFC)** is a numbered, permanent public document that specifies Internet protocols and practices, published by the RFC Editor. Streams (RFC 4844): 1. **IETF stream:** working-group documents, including all standards-track RFCs. 2. **IAB stream:** architecture and policy documents. 3. **IRTF stream:** research group documents. 4. **Independent submission stream:** documents sent by individuals outside the other streams. Status types include Proposed Standard, Internet Standard, Best Current Practice, Informational, Experimental and Historic. ## Check yourself The answer's key points as multiple-choice questions, with the correct option and why. 1. How is the IPv6 base header structured? A. Variable 20-60 bytes with a header checksum B. Fixed 40 bytes with no checksum C. Fixed 20 bytes with options D. Variable 40-80 bytes with fragmentation fields Answer: B. The base header is fixed at 40 bytes with 8 fields and no checksum. (Key point: IPv6 header size) 2. What do the Hop Limit and Next Header fields do in IPv6? A. Hop Limit sets priority; Next Header gives packet length B. Hop Limit is decremented at each router and the packet is dropped at 0; Next Header gives the type of the following header C. Hop Limit holds the flow label; Next Header holds the checksum D. Hop Limit counts bytes; Next Header is the destination address Answer: B. Hop Limit replaces IPv4 TTL; Next Header replaces Protocol and chains extension headers (6 = TCP, 17 = UDP, 58 = ICMPv6, 44 = fragment). (Key point: Hop Limit and Next Header) 3. Which IPv6 header fields support quality of service? A. Version and Payload Length B. Traffic Class and 20-bit Flow Label C. Hop Limit and Next Header D. Source and Destination Address Answer: B. Traffic Class gives priority/DiffServ class, and Flow Label identifies packets of one flow. (Key point: QoS support) 4. Where does IPv6 place optional features such as routing, fragmentation and authentication? A. In a variable Options field in the base header B. In separate extension headers chained by Next Header C. In the Flow Label D. In the link-layer frame Answer: B. Optional features are separate extension headers linked through the Next Header field, keeping the base header simple. (Key point: Extension headers) 5. Which is NOT one of the RFC streams? A. IETF stream B. IAB stream C. IRTF stream D. ISP stream Answer: D. The streams are IETF, IAB, IRTF and Independent submission. (Key point: RFC streams) ## Related in Internet and Intranet - [RFC management by streams and status](https://www.bctengineer.com/question.md?key=semester_8%2Finternet_and_intranet%3Arfc-streams-status) — Internet and Intranet, chapter 1 - [RFC role and IPv6 addressing](https://www.bctengineer.com/question.md?key=semester_8%2Finternet_and_intranet%3Arfc-development-ipv6-addressing) — Internet and Intranet, chapter 2 - [RFC and IPv4/IPv6 fragmentation](https://www.bctengineer.com/question.md?key=semester_8%2Finternet_and_intranet%3Arfc-fragmentation-ipv4-ipv6) — Internet and Intranet, chapter 2 - [WWW; HTTP header and connection types](https://www.bctengineer.com/question.md?key=semester_8%2Finternet_and_intranet%3Awww-http-header-connection) — Internet and Intranet, chapter 4 - [IPv4 vs IPv6 datagram fragmentation](https://www.bctengineer.com/question.md?key=semester_8%2Finternet_and_intranet%3Aipv4-ipv6-fragmentation) — Internet and Intranet, chapter 2, asked 2× - [TCP/IP applications; IPv4 vs IPv6 routing](https://www.bctengineer.com/question.md?key=semester_8%2Finternet_and_intranet%3Atcpip-application-ipv4-ipv6-routing) — Internet and Intranet, chapter 2 ## Related in other subjects - [IPv6 datagram format](https://www.bctengineer.com/question.md?key=semester_7%2Fcomputer_networks_and_security%3Aipv6-datagram-format) — Computer Networks and Security, chapter 7, asked 2× - [Header translation and tunneling](https://www.bctengineer.com/question.md?key=semester_7%2Fcomputer_networks_and_security%3Aheader-translation-tunneling) — Computer Networks and Security, chapter 7 - [MBI block diagram and basic features](https://www.bctengineer.com/question.md?key=semester_5%2Finstrumentation_ii%3Ambi-block-features) — Instrumentation II, chapter 1, asked 4× - [Compare IPv6/IPv4 headers; migration](https://www.bctengineer.com/question.md?key=semester_7%2Fcomputer_networks_and_security%3Aipv6-ipv4-header-migration) — Computer Networks and Security, chapter 7, asked 2×