IPv6 技術理論與實務研習班 IPv6 Addressing

1. IPv6 技術理論與實務研習班 IPv6 Addressing

2. Content • Introduction • IPv6 Addressing • IPv6 Header • ICMPv6 • Neighbor Discovery • Address Autoconfiguration • Addressing Allocation Policy • Global IPv6 actions

3. Content • Introduction • IPv6 Addressing • IPv6 Header • ICMPv6 • Neighbor Discovery • Address Autoconfiguration • Addressing Allocation Policy • Global IPv6 actions

4. IPv4定址 • IPv4以32bit來做定址空間 • 共四十億個IPv4位址可用 • IPv4位址表示方式為xxx.xxx.xxx.xxx例如211.72.211.1 • IPv4定址架構(classfull)如下 • 001 - 126 = Class A • 128 - 191 = Class B • 192 - 223 = Class C • 224 - 239 = Class D • 240 - 254 = Class E

5. Problems with IPv4(1/2) • Address depletion/ exhaustion and its implications • NAT (Network Address Translation) • CIDR IPv4 address allocation rate

6. Problems with IPv4(1/2) • Scaling problems with Inter- domain routing • CIDR (Classless Inter-Domain Routing) • Manual configuration required • DHCP (Dynamic Host Configuration Protocol) • Multicast, Security, Quality of Service and Mobility • IP multicast, IPSec, DiffServ and IP mobility • Header and format limitations that limit future flexibility

7. NAT • Network Address Translation allows a site to use private addresses behind a NAT gateway/ firewall when communicating locally, • and then automatically get a global IPv4 address assigned from a smaller pool when needed for Internet communication, • which requires changing the IPv4 header’s source address on the fly, which has a few problems...

8. Potential IPv6 Services • Broadband Access Subscribers • 95% FTTH coverage by 2008 • 6 millions by 2008 • 3G and WLAN Services • 3G services to be launched in 4Q 2003 • Public Hotspots deployment plan to make Taiwan a “Wireless Island • Home network and IA Services • e-Taiwan Projects will catalyze the development of home & IA • More IP addresses will be consumed • 2. More advanced features (e.g. Mobility, Auto-configuration, QoS, Security) will be required IPv6

9. Content • Introduction • IPv6 Addressing • IPv6 Header • ICMPv6 • Neighbor Discovery • Address Autoconfiguration • Addressing Allocation Policy • Global IPv6 actions

10. Address Notation • 以16進位，每16位元為單位並以‘：’為區隔來表示 • 3FFE:3600:4368:1234:0008:AB12:98CE:1000 • IPv4以十進位，每8位元為單位並以‘‧’為區隔來表示，如202.39.157.141 • 為使標示簡潔，位於一單位內前方之0可省略 • 3FFE:3600:4368:1234:8:AB12:98CE:1000 • 為使標示簡潔，若有連續為0 之位元，可以“::”表示，但一個位址中只能使用一次 • 3FFE:3600::1 與 3FFE:3600:0000:0000:0000:0000:0000:0001 • 3FFE:3600::3:0000:1與3FFE:3600:0000:0000:0000:0003:0000:0001

11. IPv6 - Addressing Model • Addresses are assigned to interfaces • No change from IPv4 Model • Interface ‘expected’ to have multiple addresses • Addresses have scope • Link Local • Site Local • Global • Addresses have lifetime • Valid and Preferred lifetime Link-Local Global Site-Local

12. Basic Address Types U • Unicast • Address of a single interface • Delivery to single interface • for one-to-one communication • Multicast • Address of a set of interfaces • Delivery to all interfaces in the set • for one-to-many communication • Anycast • Address of a set of interfaces • Delivery to a single interface in the set • for one-to-nearest communication • Nearest is defined as being closest in term of routing distance M M M A A A

13. Address Type Prefixes Address typeBinary prefix IPv4-compatible 0000...0 (96 zero bits) global unicast 001 link-local unicast 1111 1110 10 site-local unicast 1111 1110 11 multicast 1111 1111 • all other prefixes reserved (approx. 7/8ths of total) • anycast addresses allocated from unicast prefixes

14. Aggregatable Global Unicast Addresses 001 TLA Res NLA subnet interface ID • TLA(Top Level Aggregator) = 13 bits • TLA routers(default-free router) do not have a default route, only route with 16 bits prefix • may be assigned to providers or exchanges • Res= 8 bits • Reserved for future use in expanding the size of either the TLA or NLA • NLA(Next Level Aggregator)= 24 bits • SLA(Site level Aggregator)= 16 bits • Public topology • Collection of larger and smaller ISP • Site topology • Collection of subnets within an organization’s site public topology (45 bits) site topology (16 bits) interface identifier (64 bits)

15. Link-Local Unicast Addresses • meaningful only in a single link zone, and may be re-used on other links • Link-local addresses for use during auto-configuration and when no routers are present • Required for Neighbor Discovery process, always automatically configuration • An IPv6 router never forwards link-local traffic beyond the link • Prefix= FE80::/64 1111111010 0 interface ID 10 bits 54 bits 64 bits

16. Site-Local Unicast Addresses • meaningful only in a single site zone, and may be re-used in other sites • Equivalent to the IPv4 private address space • Address are not automatically configured and must be assigned • Prefix= FEC0::/48 1111111011 0 subnet ID interface ID 10 bits 38 bits 16 bits 64 bits

17. Special IPv6 address • Unspecified address(0:0:0:0:0:0:0:0 or ::) • Indicate the absence of an address • Equivalent to IPv4 0.0.0.0 • Never assigned to an interface or used as a destination address • Loopback address (0:0:0:0:0:0:0:1 or ::1) • Identify a loopback interface • IPv4-compatible address (0:0:0:0:0:0:w.c.x.z or ::w.c.x.z) • Used by dual-stack nodes • IPv6 traffic is automatically encapsulated with an IPv4 header and send to the destination using the IPv4 infrastructure • IPv4 mapped address (0:0:0:0:0:FFFF:w.c.x.z or ::FFFF:w.c.x.z) • Represent an IPv4-only node to an IPv6 node • Never used as a source or destination address of IPv6 packet • NSAP(Network Service Access Point) address(FP=0000001) • IPX(Internetwork Packet Exchange) address (FP=0000010)

18. Multicast IPv6 addresses • Multicast address can not be used as source or as intermediate destination in a Routing header • low-order Transient(T) flag indicates permanent (T=0) / transient(T=1) group; three other flags reserved • Scope field • 1: node-local • 2: link-local • 5: site-local • 8: organization-local • E: global • Others: reserved flags scope group ID 11111111 8 4 4 112 bits

19. Other IPv6 addresses • Solicited-node address • Facilitates the efficient query of network node during address resolution • Prefix= FF02::1FF00/104 and the last 24-bits of IPv6 address • Anycast IPv6 address • Assigned to multiple interface • Only used as destination address • Only assigned to router • anycast addresses are indistinguishable from unicast • Subnet-router anycast address is predefined and requires Subnet Prefix 000…000 n bits 128 - n bits

20. IPv6 interface identifier • Lowest-order 64-bit field of unicast address • Globally unique or locally unique within a subnet • Future higher-layer protocols may take advantage of globally-unique interface IDs to identify nodes independently of their current location • Configure interface identifier • manual configuration • DHCPv6 (configures whole address) • automatic derivation from MAC address or other hardware serial number • pseudo-random generation (for client privacy) • the latter two choices enable “serverless” or “stateless” autoconfiguration, when combined with high-order part of the address learned via Router Advertisements

21. The conversion of a universally administered, unicast IEEE 802 address to an IPv6 interface identifier

22. Content • Introduction • IPv6 Addressing • IPv6 Header • ICMPv6 • Neighbor Discovery • Address Autoconfiguration • Addressing Allocation Policy • Global IPv6 actions

23. IPv6 vs. IPv4 Packet Data Unit maximum 65535 octets minimum 20 octets IPv4 Header Data Field IPv4 PDU maximum 65535 octets Fixed 40 octets 0 or more IPv6 Header Extension Header Extension Header Transport-level PDU IPv6 PDU

24. Comparison of IPv4 and IPv6 Header IPv6 Packet Header IPv4 Packet Header Traffic Class Service Type Ver Flow Label Ver IHL Total Length Next Header Hop Limit Payload Length Identification Flags Offset TTL Protocol Header Checksum Source Address Source Address Destination Address Options + Padding 32 bits Destination Address

25. Summary of Header Changes between IPv4 & IPv6 • Streamlined • Fragmentation fields moved out of base header • IP options moved out of base header • Header Checksum eliminated • Header Length field eliminated • Length field excludes IPv6 header • Alignment changed from 32 to 64 bits • Revised • Time to Live ’ Hop Limit • Protocol ’ Next Header • Precedence & TOS ’ Traffic Class • Addresses increased 32 bits ’ 128 bits • Extended • Flow Label field added

26. IPv6 extension header 40 octets 0 or more • Hop-by-hop options header • Routing header • Fragment header • Authentication header • Encapsulating security payload header • Destination options header IPv6 Header Extension Header Extension Header Transport-level PDU IPv6 PDU general form

27. IPv6 extension header(cont.) Octets: 40 IPv6 header • IPv6 specification recommended order: • IPv6 header • Hop-by-hop options header • Destination options header(for intermediate destination when the routing header is present) • Routing header • Fragment header • Authentication header • Encapsulation security payload header • Destination options header(for final destination) Variable Hop-by-hop options header Variable Routing header 8 Fragment header Variable Authentication header Variable Encap security payload header Variable TCP header Variable Application data = Next header field IPv6 packet with all extension headers

28. Hop-by-Hop option header • Specify delivery parameters at each hop on the path to the destination • Header Extension Length • No of 8-byte block in Hop-by-Hop option header • Not including first 8 bytes • Option • Type-Length-Value(TLV) format • 0: Pad1– insert single byte of padding • 1: PadN – insert 2 or more byte of padding • 5: Router Alert – indicate to the router the packets require additional processing(MLD and RSVP) • 194: Jumbo Payload – indicate payload size over 65,535 (65,535~2^32-1)

29. Destination option header • Specify packet delivery parameter for either intermediate destinations or final destinations • If Routing header exists, it specifies delivery or processing options at each intermediate destination

30. Routing header • Similar to the source routing in IPv4 • Use of Routing header with anycast addresses allows routing packets through particular regions • e.g., for provider selection, policy, performance, etc.

31. S A B D Example: Header when S to A

32. S A B D Example: Header when A to B

33. S A B D Example: Header when B to D

34. Fragment header • Fragmentation and reassembly services is an end-to-end function; routers do not fragment packets en-route if too big—they send ICMP “packet too big” instead • Support only on source nodes

35. Authentication header • Provide data authentication • verification of the node that sent the packet • Provide data integrity • verification that the data was not modified in transit • Provide anti-replay protection • assurance that captured packets cannot be retransmitted and accepted as valid data

36. Encapsulating security payload(ESP) header and trailer • Provides data confidentiality, data authentication, and data integrity

37. Content • Introduction • IPv6 Addressing • IPv6 Header • ICMPv6 • Neighbor Discovery • Address Autoconfiguration • Addressing Allocation Policy • Global IPv6 actions

38. Features of ICMPv6 • An integral part of IPv6 and MUST be fully implement by every IPv6 node (RFC 2463) • Next Header value= 58 • Report delivery or forwarding errors • Provide simple echo service for troubleshooting • Multicast Listener discovery(MLD) – 3 ICMP messages • Neighbor Discovery(ND) – 5 ICMP messages

39. ICMPv6 message format

40. Two types of ICMP messages • Error messages • Report error in the forwarding or delivery • Informational messages • Provide diagnostic function, MLD, and ND

41. Error message(Destination Unreachable) • Send by router or destination host

42. Error message(Packet Too Big) • Send when link MTU is smaller than the size of packet • Used for IPv6 Path MTU Discovery process

43. Error message(Time Exceeded) • Send by router when Hop limit field is zero • Code field: • 0: Hop limit= 0 • Hop limit of outgoing packets is not large enough to reach destination, or • Routing loop exist • 1: fragmentation reassembly time of destination host is exceeded

44. Error message(Parameter Problem) • Send by router or destination host when errors of IPv6 header or extension header

45. Informational message • Echo Request message • Echo Reply message • Identifier and Sequence Number are send by host and used to match incoming Echo Reply with corresponding Echo Request(same as IPv4) • Multicast Listener Query messages: • Query, Report, done(like IGMP for IPv4)

46. Minimum MTU • Link MTU • A link’s maximum transmission unit(ex: the max IP packet size that can be transmitted over the link) • Path MTU • The minimum MTU of all the links in a path between a source and a destination • Minimum link MTU for IPv6 is 1280 octets vs 68 octets for IPv4 • On links with MTU < 1280, link-specific fragmentation and reassembly must be used • On links that have a configurable MTU, it’s recommended a MTU of 1500 bytes

47. Path MTU Discovery • RFC 1981 • Implementations are expected to perform path MTU discovery to send packets bigger than 1280 octets • For each destination, start by assuming MTU of first-hop link • If a packet reach a link in which it can’t fit, will invoke ICMP “packet too big” message to source, reporting the link’s MTU; MTU is cached by source for specific destination • Occasionally discard cached MTU to detect possible increase • Minimal implementation can omit path MTU discovery as long as all packets kept <= 1280 octets • Ex: in a boot ROM implementation

48. Content • Introduction • IPv6 Addressing • IPv6 Header • ICMPv6 • Neighbor Discovery • Address Autoconfiguration • Addressing Allocation Policy • Global IPv6 actions

49. Neighbor Discovery(ND) • RFC 2461 • Node(Hosts and Routers) use ND to determinate the link-layer addresses for neighbors known to reside on attached links and quick purge cached valued that become invalid • Hosts also use ND to find neighboring router that willing to forward packets on their behalf • Nodes use the protocol to actively keep track of which neighbors are reachable and which are not, and to detect changed link-layer addresses • Replace ARP, ICMP Router Discovery, and ICMP Redirect used in IPv4

50. IPv6 ND processes • Router discovery • Discover the local hosts on an attached link • Equivalent to ICMPv4 Router Discovery • Prefix discovery • Discovery the network prefix • Equivalent to ICMPv4 Address Mask Request/Reply • Parameter discovery • Discovery additional parameter(ex: link MTU, default hop limit for outgoing packet) • Address autoconfiguration • Configure IP address for interfaces • Address resolution • Equivalent to ARP in IPv4