ipv6

IPv6

Paul Schopis

[email protected]

IPv4 has 12 mandatory fields in its Header.

Version HD Len TOS Total LengthIdentification Flags Frg Offset

TTL Protocol Header ChecksumSource Address

Destination Address

Options Padding

32 bits

20 Octets

IPv6 removes Six fields and is simpler

Version Traffic ClassPayload Length Next Header Hop Limit

Source Address

Next Header Extension Header Info

Flow Label

Destination Address

32 bits

IPv6 Headers are 40 bits long and 64 bit aligned for fast processing. Addresses are 128 bits e.g. 4x IPv4.

Extension HeadersMultiple headers must follow

designated order

1. IPv6 Header

2. Hop-by-Hop Options

3. Destination Header(Placed here used with Routing Header)

4. Routing Header

5. Fragment Header

6. Authentication Header

Extension Headers

7. Encapsulation Security Payload (ESP)

8. Destination Options

9. Upper Layer (TCP/UDP)

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

Destination Options

• Not processed by routers

• Header Type = 60

• Options field allows rich number of options e.g. > 256.

Next Header Ext Header LengthOptions Continued

Options

Option Type 8bits Option Data Len Option Data

Action Change Number

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.

Routing Header

• Type = 43

• Explicit Routing Path

• Does not require a complete list

• Number of Headers does not change but is updated.

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 FragIdentification

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 Payload Len Reserved

Security Parameters Index SPI

Sequence Number

Authentication Data

Upper Layer Protocols

• TCP is unchanged

• UDP unlike IPv4, checksum is no longer optional it is mandatory.

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 1Type Code Checksum

Options

Packet Data

Two Broad Categories

• Error Messages

• Informational

Destination UnreachableCode Meaning0 No route to Destination1 Communication with destination

administratively prohibited2 (Not Assigned)3 Address Unreachable4 Port Unreachable

Code = 0-4 ChecksumUnused

As much of the original packet that will fit without Violating the MTU

Type = 1

Packet Too Big

Type = 2 Code = 0 Checksum

MTU


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.

Parameter ProblemCode Meaning0 Erroneous Header Field Encountered1 Unrecognized Next Header Type2 Unrecognized IPv6 Option encountered

Type = 4 Code = 0 - 2 ChecksumPointer


Echo and Echo Reply

Type = 128/129 Code = 0 ChecksumIdentifier Sequence Number

Data

Multicast Listener ProtocolTypes130 = Query131 = Report132 = Done

Type Code ChecksumMaximum Response Delay Reserved

Multicast Address

Neighbor Discovery Protocol

• Combines several IPv4 features into a single protocol.

• Replaces– ARP– Router Discovery– Redirect Messages

Router Solicitation MessageType = 133 Code = 0 Checksum

Reserved

Destination Address

Source Link Layer Address (optional)

Destination Address = All routers Multicast AddressSource Address = Sending Nodes Address or unspecified

Neighbor Discovery –Router Solicitations

RA

ICMP Type = 133Src = Unspecified addressDst = All-routers multicast address

At boot time, nodes send router solicitations to receiveRouter Advertisements

RS

Router Advertisement Message 1 1 1 1 1 1 1 1 1 1 2 2 2 2 2 2 2 2 2 2 3 30 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 MO Reserved Router Lifetime

Reachable Time

Retransmission Timer

Options: 1 Source Link Layer Address2.MTU

3. Prefix Information

If M = 1 hosts use stateful address management ex. DHCPv6IF O = 1 Hosts use stateful autoconfiguration for non- address configuration

Neighbor Discovery –Router Advertisements

RA RA

ICMP Type = 134Src = Router link-local addressDst = All nodes multicast addressData = options, prefix, lifetime, autoconfig flag

Neighbor Solicitation Message 1 1 1 1 1 1 1 1 1 1 2 2 2 2 2 2 2 2 2 2 3 30 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 ChecksumReserved

Target Address

Optional Source Link Layer Address

Sender is requesting Data Link Layer address from Target and provides its Data Link Layer Address

Neighbor Advertisement Message

Type =136 Code = 0 ChecksumRSO Reserved

Target Address

Optional Target Link Layer Address

R = RouterS = Response to Neighbor SolicitationO = Over ride existing LLA cache

Neighbor Discovery-Neighbor Solicitation

A B

ICMP Type =135

Src =A

Dst = Solicited-node multicast of B

Data = Link-Layer address of A

Query = what is your link address?

Neighbor Discovery-Neighbor Advertisement

A B

ICMP type = 136Src = BDst = AData = link-layer address of B

A and B can now exchange packets

Redirect MessageType = 137 Code = 0 Checksum

Reserved

Target Address

Destination Address

Options: Target Link Layer AddressRedirected Header

Sent by router to inform host of better first hop.

Neighbor Discovery –Redirect

R2

Src = ADst IP = 2001:468:B01:2::1/64Ether Default = R2Redirect:Src = R2Dst = AData = good router = R1

R1A B

2001:468:B01:2::1/64

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 30 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

Prefix Information Option 1 1 1 1 1 1 1 1 1 1 2 2 2 2 2 2 2 2 2 2 3 30 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 ReservedValid Lifetime

Preferred Lifetime

Reserved2

Prefix

L Bit = May used for on-link determinationA Bit = Prefix may be used for address autoconfiguration

Redirected Header Option

Type = 4 Length ReservedReserved

IP Header + Data

IP Header and Data field contains original packet tuncated soIt is <= 1280 Octets

MTU Discovery Option

Type = 5 Length = 1 Reserved

MTU

Ensures all links use same MTU

Path MTU Algorithm

Source MTU =Path MTU

Send Packet Packet TooBig Message

Reduce PacketSize

Yes No

Send PacketPeriodically retest

For Path MTU

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

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

http://[2001:1:4f3a::206:ae14]:8080/index.html

Address Representation Continued

• IPv4 Mapped addresses.– 0:0:0:0:0:FF:192.168.30.1– =::FF:192.168.30.1– =::FF:C0A8:1E01

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.

Link-Local

• 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

10 bits 64 bits interface ID54 bits set to 0

Site-Local

• 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.

10 bits Site Local 38 bits of 0 16 bits subnet ID 64 bits Interface

Aggregatable Global Unicast Addresses

• TLA – Top Level Aggregator

• RES – Reserved

• NLA – Next Level Aggregator

• SLA – Site Level Aggregator

Provider Site Host

TLA RES NLA SLA Interface ID

3 13 8 24 bits 16 bits 64 bits

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

Multicast

– Examples • FF02::/16 = Link-Local• FF08::/16 = Organizational• FF0E::/16 = Global

F F 0 or 1 1,2,5,8 or E

Multicast Assigned AddressesFF0X:: is reserved where x=(0..F)

Address Scope MeaningFF01::1 Node-Local All NodesFF02::1 Link-Local All NodesFF01::2 Node-Local All RoutersFF02::2 Link-Local All RoutersFF05::2 Site-Local All RoutersFF02::1:FFXX:XXXX Link-Local Solicited Node

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

Anycast EUI-64 Format

• 64 bit prefix• 57 bits of ones, except 7th bit from left set to

zero• 7 bit Anycast ID

11111101…111 Anycast ID64 bit prefix

Anycast Non-EUI-64

• N number of bits in prefix (Variable)– allows greater granularity

• (128-n of ones)-7

• 7 bits of Anycast ID

Prefix 111111111… Anycast ID

Defined Anycast Ids: 7F reserved7E Mobile home networks00 – 7D Reserved

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

Kernel IPv6 routing table

Destination Flags Metric Ref Use Iface

::1/128 U 0 0 0 lo

fe80::206:5bff:fe01:7e02/128 U 0 0 0 lo

fe80::/10 UA 256 0 0 eth0

ff00::/8 UA 256 0 0 eth0

::/0 UDA 256 0 0 eth0

eth0 Link encap:Ethernet HWaddr 00:06:5B:01:7E:02inet addr:199.18.97.146 Bcast:199.18.97.255 Mask:255.255.254.0 inet6 addr: fe80::206:5bff:fe01:7e02/10 Scope:LinkUP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1

lo Link encap:Local

Loopbackinet addr:127.0.0.1 Mask:255.0.0.0

inet6 addr: ::1/128 Scope:Host

UP LOOPBACK RUNNING MTU:16436 Metric:1

sit0 Link encap:IPv6-in-IPv4 NOARP MTU:1480 Metric:1

Required Router Addresses

• All required node addresses• Subnet-router anycast addresses for

interfaces configured to act as forwarding interfaces.

• Other anycast configured addresses• All-routers multicast address• Specific multicast addresses for routing

protocols.

FastEthernet0/0 is up, line protocol is up

IPv6 is enabled, link-local address is FE80::201:42FF:FE59:B310

Description: Native IPv6

Global unicast address(es):

2001:468:B01:0:201:42FF:FE59:B310, subnet is 2001:468:B01::/64

Joined group address(es):

FF02::1

FF02::2

FF02::1:FF59:B310

Addressing Architecture

Prefix Hex Size Allocation0000 0000 0000-00FF 1/256 Reserved0000 0001 0100-01FF 1/256 Unassigned0000 001 0200-03FF 1/128 NSAP0000 010 0400-05FF 1/128 IPX->Moving to Unassigned0000 011 0600-07FF 1/128 Unassigned0000 1 0800-0FFF 1/32 Unassigned0001 1000-1FFF 1/16 Unassigned001 2000-3FFF 1/8 IANA to registries

Addressing Architecture Continued

Prefix Hex Size Allocation

010,011,100,101,

110

4000-CFFF 5*1/8=5/8 Uassigned

1110 D000-EFFF 1/16 Unassigned

1111 0 F000-F7FF 1/32 Unassigned

1111 10 F800-FBFF 1/64 Unassigned

1111 110 FC00-FDFF 1/128 Unassigned

1111 1110 0 FE00-FE7F 1/512 unassigned

1111 1110 10 FE80-FEBF 1/1024 Link-Local

1111 1110 11 FEC0-FEFF 1/1024 Site-Local

1111 1111 FF00-FFFF1/256 1/256 Multicast

IPv6 over Data Link Layers

• Ethernet• FDDI• Token Ring• Arcnet• PPP• NBMA• ATM• Frame Relay

IPv6 over Ethernet

• IPv6 has a specific Ethernet protocol ID

0x86DDEthernet DestinationAddress

EthernetSourceAddress

IPv6 packet

EUI-6400 90 27 FC 0F17Ethernet MAC

Address 48 bits

00 90 27

FF FE

17 FC 0F

00 90 27 FF FE 17 FC 0F64 bits Version

Uniqueness mask 000000X0 where X=1 is unique and X=0 in not unique. So if X=1 then the EUI-64 Address is 02 90 27 FF FE 17 FC 0F

Multicast Mapping over Ethernet

FF02 0000 0000 0000 0000 0001 FF17 FC0F

IPv6 Multicast Address

33 33 FF 17 FC 0F

Ethernet multicast prefix

ipv6

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