Outline IPv6 IPv6 Header IPv6 Addressing IPv6 Neighbor Discovery Jyh-Cheng Chen Department of Computer Science and IPv6 Autoconfiguration Institute of Communications Engineering National Tsing Hua University jcchen@cs.nthu.edu.tw http://www.cs.nthu.edu.tw/~jcchen 2 Format of IPv4 Address IPv4 Header 0 8 16 24 31 24 31 4 8 16 Class A netid hostid 0 Ver IHL Service Type Total Length Class B 1 0 netid hostid Identifier Flags Fragment Offset Time to Live Protocol Header Checksum Class C 1 1 0 netid hostid 32 bit Source Address Class D 1 1 1 0 multicast address 32 bit Destination Address Class E 1 1 1 1 reserved for future use Options and Padding IHL: Internet Header Length 3 4 IPv6 Header V6 vs. V4 0 4 12 16 24 31 Fields removed � IHL Version Traffic Class Flow Label � Flags Payload Length Next Header Hop Limit � Identification � Fragmentation offset 128 bit Source Address � Header Checksum Field added 128 bit Destination Address � Flow Label 5 6
V6 vs. V4 (cont.) IPv4 and IPv6 Packets Fields renamed maximum 65535 octets � Total Length -> Payload Length minimum 20 octets � Time to Live -> Hop Limit � Protocol -> Next Header IPv4 Header Payload � Service Type -> Traffic Class IPv4 Field revised maximum 65535 octets � 32-bit address to 128-bit address Fixed 0 or more 40 octets � Option: variable length replaced by extension Extension Extension header IPv6 Header Payload Header Header IPv6 7 8 0 Hop-by-Hop Options Header Next Header 4 Internet Protocol 6 Transmission Control Protocol Identify which header follows the basic IP 17 User Datagram Protocol header in the datagram 43 Routing Header 44 Fragment Header Can indicate an optional IP header or an upper layer protocol 45 Interdomain Routing Protocol 46 Resource Reservation Protocol The table in next page lists the mapping 50 Encapsulating Security Payload � Not a completed list 51 Authentication Header 58 Internet Control Message Protocol 59 No Next Header 60 Destination Option Header 9 10 Vers. Class Flow Label Payload Length Next Header:0 Hop limit Examples Source Address Destination Address IPv6 header TCP header + data next header = TCP Nxt Hdr:43 Hdr Length Hop-by-Hop Options IPv6 header Routing header TCP header + data Nxt Hdr:44 Hdr Length next header = next header = Routing Information Routing TCP Nxt Hdr:51 Reserved Fragment Offset M Fragment Identification IPv6 header Routing header Fragment header fragment of TCP Nxt Hdr:6 Hdr Length header + data next header = next header = next header = Authentication Data Routing Fragment TCP TCP Header and Data 11 12
IPv6 Extension Headers Hop-by-Hop Compromise between generality and Specify delivery parameters at each hop on the path to the destination efficiency Header Extension Length Support functions such as fragmentation, � Number of 8-byte block in Hop-by-Hop header routing, authentication, etc. � Don’t include the first 8 bits Option A sender can choose which extension headers � Type-Length-Value (TLV) format to be included � 0: Pad1– insert single byte of padding Intermediate routers only need to examine � 1: PadN – insert 2 or more byte of padding the hop-by-hop extension header � 5: Router Alert – indicate to the router the packets require additional processing (MLD and RSVP) � Only endpoints process other extension headers � 194: Jumbo Payload – indicate payload size over 65,535 13 14 Hop-by-Hop Extension Header Fragmentation Fragmentation by sources only � No fragmentation by routers Next Header Header Extension Length � End-to-end fragmentation Source Options � Use the Guaranteed Minimum MTU (maximum transfer unit) of 1280 octets � Perform Path MTU Discovery to identify the minimum MTU along the path 15 16 Fragmentation Process Fragmentation Extension Header Unfragmentable part must be processed by each intermediate node and destination Fragmentable part must only processed at final destination 17 18
Fragmentation Packets IPv6 Source Routing Source routing is optional in IPv4 Source routing in IPv6 � Leverage Routing Header 19 20 Routing Header Routing Extension Header So far only one type of routing header has been defined, known as type 0 The basic IP header’s destination address indicates the first hop on the desired path. The list in the routing header identifies subsequent hops along that path. The Segment left ( Addrs left ) field keeps track of the current position in the list. � Each router decrements this field by one 21 22 2 Router C Router D 4 Destination Option Destination Source 3 Router A Router E The destination options header contains 5 1 IP options for the datagram’s 6 4 Flow label 6 4 Flow label 6 4 Flow label destination. Payload length Nxt:43 hops Payload length Nxt:43 hops Payload length Nxt:43 hops Src: Source Src: Source Src: Source If the datagram includes a routing Dst: Router A Dst: Router C Dst: Destination header, this header can also precede Nxt Len Type:0 I:4 Nxt Len Type:0 I:3 Nxt Len Type:0 I:0 0x00 0x000000 0x00 0x000000 0x00 0x000000 that header. In that case, its options Address [0]: Router C Address [0]: Router A Address [0]: Router A will be processed by each intermediate Address [1]: Router D Address [1]: Router D Address [1]: Router C hop included in the routing header’s list. Address [2]: Router E Address [2]: Router E Address [2]: Router D Address [3]: Destination Address [3]: Destination Address [3]: Router E 23 24
Destination Option Header Outline IPv6 Header IPv6 Addressing Next Header Header Extension Length IPv6 Neighbor Discovery IPv6 Autoconfiguration Options 25 26 Address Space Addressing Model 2 128 = 3.4 × 10 38 addresses Addresses are assigned to interfaces � No change from IPv4 Model � 6.65 × 10 23 addresses per m 2 of earth Interface ‘expected’ to have multiple surface addresses If assigned at the rate of 10 6 / µ s, it Addresses have scope � Link Local would take 20 years � Site Local � Global Addresses have lifetime � Valid and Preferred lifetime 27 28 Addressing Types IPv6 Internet Global Company A Unicast Router Site-local � Address of a single interface � Delivery to single interface Link-local 1 Link-local 2 Multicast Router Router � Address of a set of interfaces � Delivery to all interfaces in the set Anycast H A H B � Address of a set of interfaces H 1 H 2 � Delivery to a single interface in the set No more broadcast addresses 29 30
Address Format Address Format (cont.) Breaks 128 bits into eight 16-bit pieces. For compact representation, a series of Colons separate each piece. consecutive zero is abbreviated with � FEDC:BA89:33FE:2145:D34C:3411:2311:A23B two colons. For example: The leading zeros are not necessary, � 1080::8:800:200C:417A but at least one digit must be present. � the “::” abbreviation may only appear once � 1080:0000:0001:0000:0008:0800:200C:417A in an address. => 1080:0:1:0:8:800:200C:417A IPv4-embedded � 0:0:0:0:0:0:13.1.68.3 or ::13.1.68.3 31 32 Prefix Type of Address 0000 0000 Reserved Address Prefix 0000 0001 Unassigned 0000 001 Reserved for NSAP allocation 0000 010 Reserved for IPX allocation 0000 011 Unassigned IPv6-address/prefix-length 0000 1 Unassigned 0001 Unassigned � prefix-length: a decimal value specifying 001 Aggregatable Global Unicast Address how many of the leftmost contiguous bits 010 Unassigned 011 Unassigned of the address comprise the prefix 100 Unassigned 101 Unassigned � 1080:0:FF:0::/64 110 Unassigned 1110 Unassigned � specify the first 64 bits 1111 0 Unassigned 1111 10 Unassigned � no mask in IPv6 1111 110 Unassigned 1111 1110 0 Unassigned 1111 1110 10 Link local use address (e.g. fe80::/10) 1111 1110 11 Site local use address (e.g. fec0::/10) 1111 1111 Multicast address (e.g. ff00::/8) 33 34 Aggregatable Global Unicast Addresses Prefix 001 TLA Res NLA subnet interface ID public site interface Address type Binary prefix topology topology identifier (45 bits) (16 bits) (64 bits) IPv4-compatible 0000...0 (96 zero bits) TLA (Top Level Aggregator) = 13 bits global unicast 001 � TLA routers do not have a default route, only route with 16 bits prefix link-local unicast 1111 1110 10 � may be assigned to providers or exchanges site-local unicast 1111 1110 11 Res= 8 bits � Reserved for future use in expanding the size of either the TLA multicast 1111 1111 or NLA NLA (Next Level Aggregator)= 24 bits all other prefixes reserved (approx. 85% SLA (Site level Aggregator)= 16 bits of total) Public topology � Collection of larger and smaller ISP anycast addresses allocated from unicast Site topology prefixes � Collection of subnets within an organization’s site 35 36
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