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Understanding IPv6: Migration Methods, Transition Issues, and Expected Outcomes

This comprehensive guide provides an in-depth understanding of IPv6 migration methods and the challenges faced during the transition from IPv4. It explores IPv4 limitations, the benefits of IPv6 such as a larger address space, improved security, and auto-configuration. Key aspects include the description of IPv6 addressing, the role of various transition mechanisms (such as dual stacks and tunneling), and the high-level architecture of IPv6. By understanding these elements, readers will be better equipped to navigate the complexities of transitioning to IPv6.

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Understanding IPv6: Migration Methods, Transition Issues, and Expected Outcomes

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  1. 1 NETS 3303 IPv6 and migration methods

  2. 2 Expected outcomes • Understanding the background • What’s wrong with v4 • How does v6 address this • What else does v6 introduce • Knowing about issues with transition from v4 to v6 • Understanding transition Mechanisms

  3. 3 IPv6, Background • IPv4 address space 232 • About half assigned • Introduction of 3G, embedded devices etc. • Clearly, we need a larger address space

  4. 4 IPv6, Background • IPv6 address space 2128 • Some other improvements over v4 • Simple fixed 40 byte header (routing) • Improved encryption and authentication • Address auto-configuration

  5. 5 IPv6 Header 32 0 5 13 17 25 Version Traffic class Flow label Payload length Next header Hop limit Source address Destination address

  6. 6 IPv6 Extension Headers • Hop-by-hop Options • Information for routers, e.g. jumbogram length • Routing • Source routing list • Fragment • Tells end host how to reassemble packets • Authentication (for destination host) • Encapsulating Security Payload • For destination host, contains keys etc. • Destination options (extra options for destination)

  7. 7 IPv6 Addressing • in theory, 1500 or so addresses per square meter of earth’s surface (2 ^128 is big number) • Notation format FEDC:BA98:7654:3210:0000:0000:0000:0089 • Interoperability with IPv4 • Use prefix 0000 0000 • 0000 0000 0000 v4: IPv4 host to IPv6 host • 0000 0000 FFFF v4: Tunnel v6 over v4, the v4 address is the tunnel end point. • Thus, v4 addresses can be embedded in v6 addresses • However, if a v6 host needs to talk to a v4 host it still needs to occupy a v4 address!!!!!!!!

  8. 8 Local Addresses • link-local used on single link (0xfe) 1111111010 | 0 (54 zeroes total) | if ID (64 bits) • auto-address configuration • neighbor discovery • no routers present • site-local used within site only 1111111011 | 0 (38) | subnet (16) | if ID • routers do not forward outside site • intended to replace “intranet” addrs, 10.0.0.0, etc.

  9. 9 address high-level architecture • FP, format prefix at FRONT is variable length allocation reserved address-space-slice reserved 00000000 1/256 unicast 001 1/8 link-local unicast 1111 1110 10 1/1024 site-local unicast 1111 1110 11 1/1024 multicast 1111 1111 1/256

  10. 10 IPv6 Hierarchy • IPv4 address space completely flat (no geographic dependency) • IPv6 semi-hierarchical (compare telephone numbers) • Top level routers have address ranges with regional meaning in routing tables • Next level routers have knowledge of ranges to organisations (corporations, ISPs etc.) • Site level routers have host and network specific routing tables

  11. 11 IPv6 Autoconfiguration • Two methods available • Dynamic Host Configuration Protocol, DHCP • Neighbour Discovery, ND • Host issues Router Solicitation message on “all routers multicast address” • Router answers with Router Advertisement message • Both ICMPv6 • Advertisement {subnet prefix:hosts 48 bit MAC address}

  12. 12 Migration Methods • dual-stacks, IPv6 and IPv4 • Tunnelling • NAT • Traditional NATs • RSIP and SIIT • REBEKAH-IP • transition likely to take a very long time

  13. 13 Tunnelling • tunnels: IPv6 internets can tunnel IPv6 packets over IPv4 networks, “short-term” • if and when more IPv6, then IPv4 tunnelled over IPv6

  14. 14 Data Data Data Data IPv6 IPv6 IPv6 IPv6 UDP UDP UDP UDP Tunnelling Dual stack routers V4 removed Host 2 Host 1 v4 v6 v6 V4 added

  15. 15 NAT Address realm 2, IPv4 Address realm 1, IPv6 Translation

  16. 16 Classical NAT • NAT has pool of public IPv4 addresses • One public address assigned to each private node on packet arrival at NAT • Address held until session closed or timeout

  17. 17 Classical NAT • Is there a problem with assigning addresses this way?

  18. 18 Classical NAT • Answer: This does not scale at all.

  19. 19 NAPT • Private hosts share a public IP address • Each identified flow is assigned a unique sender port number • Return packet translated to private address and port depending on dst. Port number

  20. 20 NAPT • Is there a problem with this approach? • Hint: reachability

  21. 21 NAPT • Network initiated communication not possible. We cannot separate hosts with same IP address.

  22. 22 ALG • Another problem: • In-band signalling • SIP • HTML • Exchange • ICQ • Netmeeting • Etc.

  23. 23 ALG • Solution: ALG • Application specific filtering • Reads and rewrites payload • Problems • Security? • Who will implement ALG?

  24. 24 RSIP • Private realm host incorporates RSIP client • RSIP client requests public IP address from RSIP server • RSIP server assigns address to client and sets up IP tunnel • Client configures private host with public address and uses tunnel to RSIP server

  25. 25 RSIP • Two versions corresponding to classical NAT and NAPT, RSA-IP and RSAP-IP • Advantage: • No ALGs necessary • Disadvantage: • Network initiated communication still impossible

  26. 26 REBEKAH-IP • Each flow has a unique address in the Internet • Sender and receiver IP addresses and port numbers • Dynamically assign a combination rather than occupying a specific address or port

  27. 27 REBEKAH-IP • Switch traffic depending on sender and receiver IP addresses and port numbers • Assign same public address to multiple private hosts • Rely on a series of dispatch mechanisms for resolving clashes in advance

  28. 28 REBEKAH-IP • Use RSIP client server concept to avoid ALG for application data • Add an ALG to DNS • Have DNS assign public addresses to private nodes • Supports Network initiated and terminated traffic

  29. 29 REBEKAH-IP Pool of public IP addresses Signalling DNS/ALG Address realm 2 Address realm 1 Data RS

  30. 30 REBEKAH-IP • DNS refinement: • Return Authoritative address to first query (make sure to get host address) • Implement SRV record for optimised client • Client optimisation • Ask for “ANY” record • Read port to use in answer

  31. 31 REBEKAH-IP • Scalability: • NAPT: C =X*216 • REBEKAH-IP: 216*216*(232-X)*X; • X*216 > C > X*296 • C = number of possible combinations • X = number of available IP addresses

  32. 32 Further reading • RFC 2460 Internet Protocol, Version 6 (IPv6) Specification. S. Deering, R. Hinden. December 1998. • RFC 2663 IP Network Address Translator (NAT) Terminology and Considerations. P. Srisuresh, M. Holdrege. August 1999. • REBEKAH-IP paper from http://mobqos.ee.unsw.edu.au

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