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IPv6

IPv6. Paul Schopis pschopis@itecohio.org. IPv4 has 12 mandatory fields in its Header. Version. HD Len. TOS. Total Length. Identification. Flags. Frg Offset. TTL. Protocol. Header Checksum. Source Address. Destination Address. Options. Padding. 32 bits. 20 Octets.

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IPv6

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  1. IPv6 Paul Schopis pschopis@itecohio.org

  2. IPv4 has 12 mandatory fields in its Header. Version HD Len TOS Total Length Identification Flags Frg Offset TTL Protocol Header Checksum Source Address Destination Address Options Padding 32 bits 20 Octets

  3. IPv6 removes Six fields and is simpler Flow Label Version Traffic Class Payload Length Next Header Hop Limit Source Address Destination Address Next Header Extension Header Info 32 bits IPv6 Headers are 40 bits long and 64 bit aligned for fast processing. Addresses are 128 bits e.g. 4x IPv4.

  4. Extension HeadersMultiple headers must followdesignated order IPv6 Header Hop-by-Hop Options Destination Header(Placed here used with Routing Header) Routing Header Fragment Header Authentication Header

  5. Extension Headers 7. Encapsulation Security Payload (ESP) 8. Destination Options 9. Upper Layer (TCP/UDP)

  6. Hop-by-Hop Options Header • Every node processes the Hop-by-Hop Header • Primarily used for • Router Alerts • Jumbograms • Jumbogram = Type 194 • Fragment Header is not present • Packet Exceeds 65,535 octets

  7. Destination Options • Not processed by routers • Header Type = 60 • Options field allows rich number of options e.g. > 256. Options Next Header Ext Header Length Options Continued

  8. Option Type 8bits Option Data Option Data Len Change Number Action Action Bits Action “00” Skip this Option “01” Discard No ICMP Report “10” Discard send ICMP Report for both unicast and multicast “11” Discard send ICMP Report only if not Multicast.

  9. Routing Header • Type = 43 • Explicit Routing Path • Does not require a complete list • Number of Headers does not change but is updated.

  10. Fragment Header • Host is responsible for fragmenting • Assumes MTU discovery is in use • Only used when packet exceeds MTU • Routers do not deal with Fragmentation Next Header Reserved Fragment Offset Reserved More Frag Identification

  11. Authentication HeaderType = 51 1 1 1 1 1 1 1 1 1 1 2 2 2 2 2 2 2 2 2 2 3 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 Next Header Reserved Payload Len Security Parameters Index SPI Sequence Number Authentication Data

  12. Upper Layer Protocols • TCP is unchanged • UDP unlike IPv4, checksum is no longer optional it is mandatory.

  13. ICMPv6 • Now includes Multicast functions • Multicast Listener Protocol • Type Field and Code Field allow more discrete treatment per Type. 1 1 1 1 1 1 1 1 1 1 2 2 2 2 2 2 2 2 2 2 3 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 Type Code Checksum Options Packet Data

  14. Two Broad Categories • Error Messages • Informational

  15. Destination Unreachable • Code Meaning • 0 No route to Destination • 1 Communication with destination • administratively prohibited • (Not Assigned) • Address Unreachable • Port Unreachable Type = 1 Code = 0-4 Checksum Unused As much of the original packet that will fit without Violating the MTU

  16. Packet Too Big Type = 2 Code = 0 Checksum MTU As much of the original packet that will fit without Violating the MTU

  17. Time Exceeded Message • Type = 3 • It has two codes • 0 = Hop Limit Exceeded • 1 = Fragment reassembly time exceeded. • Identical to Destination Unreachable except for type and code values.

  18. Parameter Problem • Code Meaning • 0 Erroneous Header Field Encountered • Unrecognized Next Header Type • Unrecognized IPv6 Option encountered Type = 4 Code = 0 - 2 Checksum Pointer As much of the original packet that will fit without Violating the MTU

  19. Echo and Echo Reply Type = 128/129 Code = 0 Checksum Identifier Sequence Number Data

  20. Multicast Listener Protocol Types 130 = Query 131 = Report 132 = Done Type Code Checksum Maximum Response Delay Reserved Multicast Address

  21. Neighbor Discovery Protocol • Combines several IPv4 features into a single protocol. • Replaces • ARP • Router Discovery • Redirect Messages

  22. Router Solicitation Message Type = 133 Code = 0 Checksum Reserved Destination Address Source Link Layer Address (optional) Destination Address = All routers Multicast Address Source Address = Sending Nodes Address or unspecified

  23. Neighbor Discovery –Router Solicitations RS RA ICMP Type = 133 Src = Unspecified address Dst = All-routers multicast address At boot time, nodes send router solicitations to receive Router Advertisements

  24. Router Advertisement Message 1 1 1 1 1 1 1 1 1 1 2 2 2 2 2 2 2 2 2 2 3 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 Type = 134 Code = 0 Checksum Hop Limit M O Reserved Router Lifetime Reachable Time Retransmission Timer Options: 1 Source Link Layer Address 2.MTU 3. Prefix Information If M = 1 hosts use stateful address management ex. DHCPv6 IF O = 1 Hosts use stateful autoconfiguration for non- address configuration

  25. Neighbor Discovery –Router Advertisements RA RA ICMP Type = 134 Src = Router link-local address Dst = All nodes multicast address Data = options, prefix, lifetime, autoconfig flag

  26. Neighbor Solicitation Message 1 1 1 1 1 1 1 1 1 1 2 2 2 2 2 2 2 2 2 2 3 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 Type = 135 Code = 0 Checksum Reserved Target Address Optional Source Link Layer Address Sender is requesting Data Link Layer address from Target and provides its Data Link Layer Address

  27. Neighbor Advertisement Message Type =136 Code = 0 Checksum R S O Reserved Target Address Optional Target Link Layer Address R = Router S = Response to Neighbor Solicitation O = Over ride existing LLA cache

  28. Neighbor Discovery-Neighbor Solicitation B A ICMP Type =135 Src =A Dst = Solicited-node multicast of B Data = Link-Layer address of A Query = what is your link address?

  29. Neighbor Discovery-Neighbor Advertisement B A ICMP type = 136 Src = B Dst = A Data = link-layer address of B A and B can now exchange packets

  30. Redirect Message Type = 137 Code = 0 Checksum Reserved Target Address Destination Address Options: Target Link Layer Address Redirected Header Sent by router to inform host of better first hop.

  31. Neighbor Discovery –Redirect 2001:468:B01:2::1/64 A B R2 R1 Src = A Dst IP = 2001:468:B01:2::1/64 Ether Default = R2 Redirect: Src = R2 Dst = A Data = good router = R1

  32. Neighbor Discovery Options • Type 1 and 2 share the same format • Type 1 is Source Data Link Layer • Type 2 is Target Data Link Layer 1 1 1 1 1 1 1 1 1 2 2 2 2 2 2 2 2 2 2 3 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 Type Length Link Layer Address

  33. Prefix Information Option 1 1 1 1 1 1 1 1 1 1 2 2 2 2 2 2 2 2 2 2 3 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 Type = 3 Length Prefix Length L A Reserved Valid Lifetime Preferred Lifetime Reserved2 Prefix L Bit = May used for on-link determination A Bit = Prefix may be used for address autoconfiguration

  34. Redirected Header Option Type = 4 Length Reserved Reserved IP Header + Data IP Header and Data field contains original packet tuncated so It is <= 1280 Octets

  35. MTU Discovery Option Type = 5 Length = 1 Reserved MTU Ensures all links use same MTU

  36. Path MTU Algorithm Packet Too Big Message Source MTU = Path MTU Send Packet Yes No Reduce Packet Size Send Packet Periodically retest For Path MTU

  37. Address Representation • Format • X:X:X:X:X:X:X:X where X is a 16 bit hexadecimal field • 2001:0468:0B01:0003:0000:0000:0000:0001 • Leading zeros • Leading Zeros may be truncated • 2001:486:B01:3:0:0:0:1 • Successive fields of zeros • May be eliminated with :: but only once within an address • 2001:468:B01:3::1

  38. Address Representation • IPv4-Compatible • =0:0:0:0:0:0:192.168.30.1 • =::192.168.30.1 • =::C0A8:1E01 • In a URL use brackets • http://[2001:1:4F3A::206:AE14]:8080/index.html • Brackets delimiter for : as part of IPv6 address verses port number

  39. Address Representation Continued • IPv4 Mapped addresses. • 0:0:0:0:0:FF:192.168.30.1 • =::FF:192.168.30.1 • =::FF:C0A8:1E01

  40. Unspecified and Loopback Address • Unspecified address: • 0:0:0:0:0:0:0:0 or more simply :: • Used as a place holder when no address is available. • Loopback Address: • 0:0:0:0:0:0:0:1 or ::1 • Same as 127.0.0.1 in IPv4 • Ids self.

  41. Link-Local 54 bits set to 0 10 bits 64 bits interface ID • Reserved address: • In binary is 1111 1110 10 • In hexadecimal is FE80::/10 • Link-Local Addresses: • Have scope limited to Link • Automatically configured with interface ID

  42. Site-Local 10 bits Site Local 38 bits of 0 16 bits subnet ID 64 bits Interface • Reserved Address: • In binary 1111 1110 11 • In Hexadecimal FEC0::/10 • Site-Local Address: • Have site limited scope • Gives topology info via the subnet field.

  43. Aggregatable Global Unicast Addresses Host Provider Site • TLA – Top Level Aggregator • RES – Reserved • NLA – Next Level Aggregator • SLA – Site Level Aggregator TLA RES NLA SLA Interface ID 3 13 8 24 bits 16 bits 64 bits

  44. Multicast • First byte is FF e.g. 1111 1111 binary. • First half of next byte is Flag. • 0 = permanent • 1 = temporary • Second half is scope. • 1= node • 2 = link • 5 = site • 8 = organization • E = global

  45. Multicast F F 0 or 1 1,2,5,8 or E • Examples • FF02::/16 = Link-Local • FF08::/16 = Organizational • FF0E::/16 = Global

  46. Multicast Assigned Addresses FF0X:: is reserved where x=(0..F)

  47. Anycast • Similar to multicast except only one node needs to receive packet • All routers are required to support it • In it’s simplest form it is: Subnet Prefix n bits 128-n of 0s Example: 2002:C058:6301:: for 6t04 relay routers

  48. Anycast EUI-64 Format • 64 bit prefix • 57 bits of ones, except 7th bit from left set to zero • 7 bit Anycast ID 64 bit prefix 11111101…111 Anycast ID

  49. Anycast Non-EUI-64 • N number of bits in prefix (Variable) • allows greater granularity • (128-n of ones)-7 • 7 bits of Anycast ID Anycast ID Prefix 111111111… Defined Anycast Ids: 7F reserved 7E Mobile home networks 00 – 7D Reserved

  50. Required Node Addresses • Link-Local • Loopback Address • Assigned Unicast Address • All-Nodes Multicast Address • Solicited-Node Multicast for each unicast and anycast address • Multicast address for all groups to which it belongs • Site-Local address if used

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