IPv6

1
IPv6

• This will be real shortly
• Packet format
• Header format and contents
• Address space allocation
• Header extensions
• Fragmentation
• ICMPv6
• Security

2
Ipv6

• Internet Protocol
• Connectionless communication
• Best effort delivery
• Virtual addressing
• Address is 128 bits
• 2128 340,000,000,000,000,000,000,000,000,000,000
  ,000,000
• Provides for some increase in security
• Increases the address space from 232 to 2128
• A modest increase of
• 296 90,000,000,000,000,000,000,000,000,000

3
Ipv6 RFC's

• RFC 2460 Ipv6 Specification
• RFC 2373 Addressing Architecture
• RFC 2463 ICMP
• RFC 2473 Packet Tunneling
• RFC 2675 - Jumbograms
• RFC 2732 Ipv6 addresses in URL's
• RFC 3041 Privacy Extensions
• RFC 2464 Ipv6 over Ethernet
• RFC 3879 SiteLocal Addresses
• Plus many others

4
IPv6 Datagram Format
Total datagram size constraints Maximum 216
-1 bytes, unless! Header length 10 32-bit words
(40 bytes)? Plus other headers
...
nth Header
1st Header
Payload
5
IPv6 Datagram Header
Bit
0
15 16
31
11 12
3 4
23 24
Traffic Class
Ver
Flow Label
Word 0
Word 1
Next Header
Payload Length
Hop Limit
Word 3
Source Address 4 4 8 bits
Word 7
Destination Address 4 4 8 bits
6
IP Datagram (cont)?

• Ver IP Version 6
• Traffic Class 8 bit priority value
• Flow Label May indicate special handling
• Payload Length Actual length of payload including
  all extension headers or 0
• Next header 8-bits that identifies the next
  header
• Similar to protocol field in IPv4
• Hop limit Similar to IPv4 ttl
• Source Address IP address of sender
• Destination Address IP address of destination

7
Definitons

• Node A device that implements Ipv6
• Router A node that forwards Ipv6 packets not
  explicitly addressed to itself.
• Host Any node that is not a router.
• Link Layer 2 communication link over which nodes
  can communicate.
• Neighbors Nodes attached to the same link.
• Interface A node's attachment to a link.
• Address An IPv6 identifier for an interface or
  set of interfaces.
• Packet An IPv6 header plus payload.

8
Ipv6 Address Types

• Unicast An identifier for a single interface. A
  packet sent to a unicast address is delivered to
  that addressed interface.
• Anycast An identifier for a set of interfaces.
  A packet sent to an anycast address is delivered
  to one (usually the neaest) of the addressed
  interfaces.
• Multicast An identifier for a set of interfaces.
  A packet sent to a multicast address is delivered
  to all interfaces identified by that address.
• Broadcast No longer. Must use multicast.

9
IPv6 Address Model

• Addresses are assigned to interfaces not to
  nodes.
• Every interface is required to have at least one
  link-local unicast address.
• An interface may have multiple addresses.
• A subnet prefix is associated with one link.
• Multiple subnets may be assigned to the same link.

10
IPv6 Address Representation

• Generally an IPv6 address is 8 16 bit hex numbers
  separated by 's.
• For example
• FEDCBA9876543210FEDCBA9876543210
• 10800000000000080080200C417A1234
• 108000880200C417A1234
• (Note the last two are equivalent)?
• Leading zeros can be suppressed within a field.

11
Ipv6 Address Representation(cont'd)?

• Ipv6 addresses tend to have way to many zeros.
  Sometimes these
• strings of zeros can be compressed.
• indicates multiple groups of 16-bits of zeros.
• Only one per address.
• can be used to compress both leading and
  trailing zeros.
• For example
• 10800008800200C417A 10808800200C417A
• FF01000000101 FF01101
• 00000001 1
• 00000000

12
IPv4 Addresses inIPv6 Addresses

• IPv4 addresses can be embedded within an IPv6
  address.
• Generally it looks like xxxxxxd.d.d.d
• For example
• 00000013.1.68.3 or 13.1.68.3
• 00000FFFF129.144.52.38 or
  FFFF129.144.52.38

13
IPv6 Address Prefixes

• As in IPv4, IPv6 the network address is
  represented as an address prefix.
• Usually indicated by a number of left most bits.
• For example representations of the 60-bit prefix
  12AB00000000CD3 (hex) are
• 12AB00000000CD300000000000000000/60
• 12ABCD30000/60
• 12AB00CD30/60
• Often both a node's address and it's prefix can
  be combined
• 12ABCD301234456789ABCDEF/60

14
Address Types
15
Address Types cont'd
16
Special Addresses
00000000 Is the Unspecified
address The only permitted use of this
address is as the source address before the
node has learned its own address.
00000001 Is the Loopback
address Must never appear outside of a single
node.
17
IPv4 Addressesin IPv6 Addresses
0
32 bits
80 bits
16 bits
0000 0000 Something goes here
IPv4 Address
Node address
18
Unicast Addresses
0
127
128 bits
Node address
0
127
m-1
m bits
128-m bits
Subnet prefix
Interface ID
Node address
0
127
128-m-n bits
m bits
n bits
Subnet1 prefix
Subnet2 prefix
Interface ID
Node address
19
Interface Identifiers
63
64
0
127
64 bits
64 bits
Subnet prefix, link address
Interface ID
Node address
Interface IDs are used to identify interfaces on
a link. They must be unique on the link. They may
be unique over a broader scope, i.e. the entire
net. Often the interface ID is the interface's
link-layer address, e.g. The ethernet NIC's MAC
address. A single node with multiple interfaces
may have the same interface ID's.
20
EUI-64 Interface IdentifiersExtended Unique
Identifier
0
127
63
64 bits
64 bits
Subnet prefix, link address
Interface ID
Node address
EUI-64 Interface IDs have global scope when a
global token is available.
0
78
1516
2324
3132
4748
63
ccccccugccccccccccccccccmmmmmmmmmmmmmmmmmm
mmmmmmmmmmmmmmmmmmmmmm
c are the company ID bits. m are the
company's extension identifier, as in IEEE ether
net NICs. u is the universal/local bit u 1
indicates global scope. g is the
individual/group bit
21
EUI-64 Interface Identifiersfor IEEE 802 MAC
addresses
0
127
63
64 bits
64 bits
Subnet prefix, link address
Interface ID
Node address
EUI-64 Interface IDs should have global scope
when a global token is available.
0
78
1516
2324
3132
4748
63
cccccc1gcccccccccccccccc1111111111111110mm
mmmmmmmmmmmmmmmmmmmmmm
c are the company ID bits. m are the
company's extension identifier, as in IEEE ether
net NICs. Global scope. g is the
individual/group bit
22
Local-Use IPv6 Addresses
Link-Local addresses
64 bits
10 bits
54 bits
0
Interface ID
1111111010
Auto-address configuration, neighbor discovery
Site-Local addresses (deprecated in 2004)
64 bits
10 bits
38 bits
16 bits
0
Interface ID
Subnet ID
1111111011
Addressing inside a site without the need for a
global prefix.
This the site-local address type has be
deprecated by RFC 3879, 9/04.
23
Aggregatable Global Unicast Addresses
Provides support for current provider based
aggregation and exchanges, a new type of
aggregation.
64 bits
3
13
24
Bits
8
16
NLA ID
SLA ID
FP
TLAID
RES
Interface ID
FP Format prefix 001 TLA ID Top Level
Aggregation Identifier RES Reserved for future
use NLA ID Next-Level Aggregation Identifier SLA
ID Site-Level Aggregation Identifier Interface
ID Interface Identifier
Reference RFC 2374
24
Aggregatable Global Unicast Addresses for Testing
Provides support for 6bone IPv6 testing.
64 bits
3
13
24
Bits
8
16
NLA ID
SLA ID
FP
TLAID
RES
Interface ID
FP Format prefix 001 TLA ID 0x1ffe - Top
Level Aggregation Identifier RES Reserved for
future use NLA ID Next-Level Aggregation
Identifier SLA ID Site-Level Aggregation
Identifier Interface ID Interface Identifier
Reference RFC 2471
25
Multicast IPv6 Addresses
Multicast addresses An identifier for a group of
nodes A node may belong to any number of
multicast groups
8 4 4 112 bits

flgs
group ID
scope
11111111
Multicast addresses must never be used as a
source address in IPv6.
26
Multicast IPv6 Addresses(cont'd)?
Multicast addresses
8 4 4 112 bits

Flgs
group ID
scope
11111111
Flgs is a set of 4 flags 0 0 0 T
The first 3 bits of flgs are reserved and must
be (0) zero. T 0 indicates a permanently
assigned multicast address This address
is assigned by the global Internet numbering
authority T 1 indicates a non-permanently
assigned multicast address
27
Multicast IPv6 Addresses(cont'd)?
Multicast addresses
8 4 4 112 bits

flgs
group ID
scope
11111111
scope is a 4-bit multicast scope value to limit
the scope of the multicast group. reserved 0,
F unassigned 3, 4, 6, 7, 9, A, B, C,
D node-local 1 link-local 2 site-local 5 org
anization-local 8 global E
28
Multicast IPv6 Addresses(cont'd)?
Examples of multicast addresses
Assume that NTP is assigned a permanent multicast
group ID of 0x101, then FF01000000101 mea
ns all NTP servers on the same node as the
sender. FF02000000101 means all NTP
servers on the same link as the
sender. FF05000000101 means all NTP
servers on the same site as the
sender. FF0E000000101 means all NTP
servers on the internet.
All nodes addresses All routers
addresses node-local and Link-local node-local,
Link-local and site-local FF010000001 FF0
10000002 FF020000001 FF0200000
02 FF050000002
The following multicast addresses are reserved
and shall never be assigned to any
group FF0X0000000 where X ranges from 0
F.
29
Required Addresses

• A node is required to recognize the following
  addressses
• as itself
• Its link-local address
• Assigned unicast addresses
• Loopback address
• All-nodes multicast address
• Solicited-node multicast

30
Frame 15 (70 bytes on wire, 70 bytes
captured)? Ethernet II, Src 000d93886a48,
Dst 333300000002 Destination
333300000002 (Ipv6-Neighbor-Discovery_00000
002)? Source 000d93886a48
(AppleCom_886a48)? Type IPv6
(0x86dd)? Internet Protocol Version 6
Version 6 Traffic class 0x00 Flowlabel
0x00000 Payload length 16 Next header
ICMPv6 (0x3a)? Hop limit 255 Source
address fe8020d93fffe886a48
(fe8020d93fffe886a48)? Destination
address ff022 (ff022)? Internet Control
Message Protocol v6 Type 133 (Router
solicitation)? Code 0 Checksum 0x7f72
(correct)? ICMPv6 options Type 1
(Source link-layer address)? Length 8
bytes (1)? Link-layer address
000d93886a48 0000 33 33 00 00 00 02 00 0d
93 88 6a 48 86 dd 60 00 33........jH... 0010
00 00 00 10 3a ff fe 80 00 00 00 00 00 00 02 0d
............... 0020 93 ff fe 88 6a 48 ff 02 00
00 00 00 00 00 00 00 ....jH.......... 0030 00
00 00 00 00 02 85 00 7f 72 00 00 00 00 01 01
.........r...... 0040 00 0d 93 88 6a 48
....jH
31
Ethernet frame header (6 bytes dst, 6 bytes src 2
bytes size/type) 0000 33 33 00 00 00 02 00 0d
93 88 6a 48 86 dd Ipv6 Ver, Type, Flow,
Payload Length, Next Header, hop limit 0000
60 00
0010 00 00 00 10 3a ff Next header 3a 58
ICMP Source Address 0010 fe
80 00 00 00 00 00 00 02 0d 0020 93 ff fe 88
6a 48 1111 1110 0100 00000 0010 0d 93 ff fe
88 6a 48 link local address c ug cc cc
Mac Address Destination Address (multicast all
nodes link-local) 0020 ff 02
00 00 00 00 00 00 00 00 0030 00 00 00 00 00
02 ICMP Message (Type 85 133 router
solicitation) Type
Checksum 0030 85 Code
00 Checksum
7f 72 Reserved
00 00 00 00
TLV Type
01 Length of
this TLV Header in 8-octet units 01
Source Link layer address 0040 00 0d 93 88 6a 48

32
IPv6 Datagram Extension Headers
Bit
0
15 16
31
11 12
3 4
23 24
Traffic Class
Ver
Flow Label
Word 0
Word 1
Next Header
Payload Length
Hop Limit
Word 3
Source Address 4 4 8 bits
Word 7
Destination Address 4 4 8 bits
Word 11
Extension Headers
33
Extension Headers

• Currently defined extension headers
• Next Header Value
• Hop-by-Hop Options 0
• Routing Header 43
• Fragment Header 44
• Destination Options 60
• Authentication 51
• Encapsulating Security Payload 50
• ICMP Header 58
• No next header 59

34
Extension Headers

• Next header values also indicate the protocol
  field that follows the extension headers.
• Next Header Value
• TCP 1
• UDP 17
• OSPF 89

35
Extension Header Order

• IPv6 header
• Hop-by-Hop Options header
• Destination Options header
• Routing header
• Fragment header
• Authentication header
• Encapsulating Security Payload header
• Destination Options header
• ICMP header
• Upper-layer header

36
Hop-by-Hop Options Header
This header carries additional information that
must be examined by every node along the packet's
delivery path.
Bit
0
15 16
31
7 8
Next Header
Hdr Ext Len
Options
Next Header 8-bit selector identifies the type of
the next header. Hdr Ext Len 8-bit unsigned
integer indicating the length of this header in
8-octet units, not including the first 8
octets. Options Contains one or more TLV-encoded
options and padding so that the entire header is
and integer multiple of 8-octets long.
37
TLV (type-length-value) Encoded Options
This header carries additional information that
must be examined by every node along the packet's
delivery path.
Bit
0
15 16
31
7 8
Option Type
Opt Data Len
Option Data
Option Type 8-bit identifier of the type of
option. Opt Data Len 8-bit unsigned integer
indicating the length of the option data field
of this option, in octets Options Variable
length field. Option-Type_specific data.
38
TLV Option Types
The Option Type identifiers are internally
encoded such that that the highest-order 2 bits
specify the action that must be taken. The third
highest bit specifies whether or not the Option
Data may be changed. These are used primarily
for padding within the options area of a header.
Bit
0
15 16
31
7 8
12345678
Opt Data Len
Option Data
Bit 1 2 3 Action Taken if the option type is not
recognized 0 0 Skip over this option and
continue processing the header 0 1 Discard
packet 1 0 Discard packet and send ICMP
Parameter Problem 1 1 Discard 0 Option Data
does not change enroute 1 Option Data may
change
39
Jumbograms (RFC 2147)?

• Permit Datagrams larger than 65,535
• Actually between 65,536 and 4,294,967,295 232 -
  1
• A Jumbo Payload Option must be carried in a
  Hop-by-Hop extension
• IP header must have payload length 0
• Next Header 0 next header is a Hop-by-Hop
  header
• Can be used only on links with large enough MTU's
• Cannot carry a Fragment Header
• Payload can be either TCP or UDP

40
Jumbograms
15 16
Bit
0
31
7 8
Next Header
Hdr Ext Len
Option Type
Opt Data Len
Jumbo Payload Length
Option Type 8-bit 0xC2 ( 11000010 Option data
does not change)? Opt Data Len 8-bit value
4 Payload Len 32-bit unsigned integer
41
Routing Header
15 16
Bit
0
31
7 8
Next Header
Hdr Ext Len
Routing Type
Segments Left
Type-specific data
Next Header 8-bit selector identifies the type of
the next header. Hdr Ext Len 8-bit unsigned
integer indicating the length of this header in
8-octet units, not including the first 8
octets. Routing Type 8-bit identifier of a
particular routing header variant. Segments
Left 8-bit unsigned integer indicating the number
of nodes to be visited. Type-specific data Info
required by the routing type.
42
Routing Header
15 16
Bit
0
31
7 8
Next Header
Hdr Ext Len
Routing Type
Segments Left
Type-specific data
Next Header 8-bit selector identifies the type of
the next header. Hdr Ext Len 8-bit unsigned
integer indicating the length of this header in
8-octet units, not including the first 8
octets. Routing Type 8-bit identifier of a
particular routing header variant. Segments
Left 8-bit unsigned integer indicating the number
of nodes to be visited. Type-specific data Info
required by the routing type.
43
Type 0 Routing Header
Bit
0
15 16
31
7 8
Next Header
Hdr Ext Len
Routing Type
Segments Left
Reserved
Address 1
Address 2
. . .
Address n
44
Fragment Header
Bit
0
15 16
31
7 8
28 29
Fragment Offset
M
Res
Next Header
Reserved
Identification
Next Header 8-bit selector identifies the type of
the next header. Reserved 8-bit reserved field
initialized to 0. Fragment Offset 13-bit unsigned
integer indicating the offset of this fragment
in 8-octet units. Res 2reserved field that is
initialized to 0. M 1-bit flag 1 more
fragments 0 last fragment. Identification 32
bits IP datagram identification number.
45
Fragmenting Packets
Unfragmentable Part
Fragmentable Part
Unfragmentable Part IPv6 Header and all extension
headers. Fragmentable Part The rest of the
packet.. Original Packet Fragments
Unfragmentable Part
First fragment
Second fragment
Last fragment
. . .
Unfragmentable Part
Fragment Header
First fragment
Unfragmentable Part
Fragment Header
Second fragment
. . .
Unfragmentable Part
Fragment Header
Last fragment
46
Destination Options Header
This header carries optional information that
must be examined only by a packet's destination
node. Again this is used primarily for padding.
Bit
0
15 16
31
7 8
Next Header
Hdr Ext Len
Options
Next Header 8-bit selector identifies the type of
the next header. Hdr Ext Len 8-bit unsigned
integer indicating the length of this header in
8-octet units, not including the first 8
octets. Options Contains one or more TLV-encoded
options and padding so that the entire header is
and integer multiple of 8-octets long.
47
Size Issues

• IPv6 requires that every link in the internet
  have an MTU of 1280 octets or greater.
• Otherwise there must a provision in Layer 2 for
  fragmentation and reassembly.

48
ICMPv6

• Internet Control Message Protocol Ver. 6
• RFC 2463
• Used to
• Return error codes
• Return informational messages
• Sent within an IP datagram
• Next Header value of 58
• Highly abused protocol

49
ICMPv6Message Codes

• Error Messages Code 0 127
• 1 Destination Unreachable
• 2 Packet too big
• 3 Time exceeded
• 4 Parameter problem
• Informational Messages 128 255
• 128 Echo request
• 129 Echo reply

50
ICMP Message General Format
Bit
0
15 16
31
7 8
Type
Checksum
Code
Message Body
The Type field indicates the type of the message
and determines the format of the remaining
data. The Code field depends on the message
type. Checksum detects data corruption.
51
Destination Unreachable Message
15 16
7 8
Bit
0
31
Checksum
Type
Code
Unused
As much of the invoking packet without exceeding
the my
Type 1 Code 0 no route to destination 1
communication with destination admin
prohibited 2 not assigned 3 address
unreachable 4 port unreachable
52
Packet Too BigMessage
15 16
7 8
Bit
0
31
Type
Checksum
Code
MTU
As much of the invoking packet without exceeding
the my
Type 2 Code 0 set by sender, ignored by
receiver. MTU The Maximum Transmission of the
next-hop link.
53
Time ExceededMessage
15 16
7 8
Bit
0
31
Type
Checksum
Code
Unused
As much of the invoking packet without exceeding
the my
Type 3 Code 0 hop limit exceeded in transit 1
fragment reasssembly time exceeded Unused set
to 0 by sender, ignored by receiver.
54
Parameter ProblemMessage
15 16
7 8
Bit
0
31
Type
Checksum
Code
Pointer
As much of the invoking packet without exceeding
the my
Type 4 Code 0 erroneous header field
encountered 1 unrecognized Next Header type
encountered 2 unrecognized IPv6 option
encountered Pointer The octet offset of the error
within the invoking packet
55
Echo RequestMessage
15 16
7 8
Bit
0
31
Type
Checksum
Code
Identifier
Sequence Number
Data ...
Type 128 Code 0 Identifier An identifier to aid
in matching Echo Replies to this Echo Request.
May be zero. Seg. No. An identifier to aid in
matching Echo Replies to this Echo Reauest. May
be zero. Data Zero or more octets of arbitrary
data.
56
Echo ReplyMessage
15 16
Bit
0
31
7 8
Type
Checksum
Code
Identifier
Sequence Number
Data ...
Type 129 Code 0 Identifier The identifier the
invoking Echo Reauest. Seg. No. The sequence
number from the invoking Echo Request. Data The
data from the invoking Echo Request message.
57
Other InformationalMessages
RFC 2461 Neighbor Discovery Neighbor Discovery
protocol is used to discover nodes on the same
link, their link-layer addresses and to find
routers.
These are ICMP Informational Messages Type Code N
ame 133 0 Router Solicitation 134 0 Router
Advertisement 135 0 Neighbor Solicitation 136 0 Ne
ighbor Advertisement 137 0 Redirect
58
Router SolicitationMessage
Hosts send Router Solicitations in order to
prompt routers to generate Router Advertisements
quickly.
Bit
0
15 16
31
7 8
Type
Checksum
Code
Reserved
Options ...
Type 133 Code 0 Identifier The identifier the
invoking Echo Reauest. Reserved Set to
zero Options Source link-layer address
59
Router AdvertisementMessage
Routers send out Router Advertisement message
periodically, or in response to a Router
Solicitation.
Bit
0
15 16
31
7 8
Type
Checksum
Code
Current hop limit
Router Lifetime
Reserved
M O
Reachable Time
Retrans Time
Options ...
60
Router AdvertisementFields
Type 134 Code 0 Cur Hop Limit 8-bit unsigned int.
Default value that should be placed in the Hop
Count field of the IP header. M 1-bit Managed
address configuration flag. O 1-bit Other
stateful configuration flag. Reserved 6-bit
unsed field. Router Lifetime 16-bit uint.
Lifetime associated with the default router in
seconds, max 18.2 hours.
61
Router AdvertisementFields (cont'd)?
Reachable Time 32-bir uint. The time, in
milliseconds, a node assumes a neighbor is
reachable. Retrans Time 32-bit uint. The time
between retransmitted Neighbor Solicitation
messages. Possible options Source link-layer
address The link-layer address of the interface
from which the Router Ad is sent. MTU Should be
sent on links that have a variable MTU.
62
Neighbor SolicitationMessage
Nodes send Neighbor Solicitations to request the
link-layer address of a target node while also
providing their own link-layer address to the
target.
15 16
Bit
0
31
7 8
Type
Checksum
Code
Reserved
Target Address
Options ...
63
Neighbor SolicitationFields
Type 135 Code 0 Reserved Unused Target
Address The IP address of the solicitation. It
must not be a multicast address. Possible
Options Source link-layer address Link-layer
address of the sender
64
Neighbor AdvertisementMessage
A node sends Neighbor Advertisements in response
to Neighbor Solicitations and sends unsolicited
Neighbor Advertisements in order to propagate
new information quickly.
Bit
0
15 16
31
7 8
Type
Checksum
Code
Reserved
R S O
Target Address
Options ...
65
Neighbor AdvertisementFields
Type 136 Code 0 R Router flag. When set
indicates that the sender is a
router. S Solicited flag. When set indicates
that the ad was sent in response to a
Solicitation from the Destination
address. O Override flag. Indicates that the ad
should override an existing cache
entry. Reserved 29-bit field that is
unused. Target Address The Target Address field
in the Solicitation. Possible options Target
link-layer address
66
Redirect Message
Routers send redirects to a host of a better
first-hop.
15 16
Bit
0
31
7 8
Type
Checksum
Code
Reserved
Target Address
Destination Address
Options ...
67
Redirect MessageFields
Type 137 Code 0 Reserved Unused Target Address An
IP address that is a better first hop to use for
the ICMP Destination Address. Destination
Address The IP address of the destination
which is redirected to the target. Possible
options Target link-layer address Link-layer
address for the target. Redirected Header As
much as possible of the IP packet that
triggered the sending of the Redirect.
68
IPv6 StatelessAddress Autoconfiguration

• Creates link-local addresses
• Verifies its uniqueness on a link
• Determines what information should be
  autoconfigured
• Should a stateful mechanism be used
• (i.e. Is there a DHCP close at hand)?
• Requires no manual configuration of hosts
• Minimal configuration of routers
• No additional hosts

69
IPv6 StatelessAddress Autoconfiguration

• Routers advertise prefixes the subnet associated
  with a link.
• Hosts generate an interface identifier.
• Combined generates an IPv6 compliant address.
• With no router, hosts can generate link-local
  addresses.
• Good enough for communication among nodes
  attached
• to the same link.

70
IPv6 Address Leases

• IPv6 addresses are leased to an interface
• For a fixed length of time.
• May be infinite
• An address is valid within its lease time.
• Invalid otherwise.
• For graceful lease expiration the address goes
  through
• 2 phases
• Preferred
• Deprecated

71
IPv6 Address Generation

• Required when
• The interface is initialized at system startup
• Reinitialized after failure
• Reinitialized after sys mgnt disables
• Interface attaches to a link for the first time

72
IPv6 Address Generation

• Prepend the link-local prefix to the EUI-64
  interface identifier.
• FE80000Interface ID
• Link-local addresses have infinite preferred and
  valid lifetimes

73
IPv6 Address Uniqueness

• Ipv6 addresses should be unique.
• The Duplicate Address Detection Algorithm is
  used.
• The Duplicate Address Detection Algorithm uses
• Neighbor Solicitation
• Neighbor Advertisement
• Possible DoS
• Claim every address is a duplicate

74
IPv6 AddressesPrivacy Considerations

• Certain amount of surveillance can be performed
  if
• Some part of your address remains constant over
  time.
• Privacy advocates say bad, bad, bad.
• Are you at the office or are you at home on a
  dialup, etc.

75
IPv6 AddressesRandomized

1. Take the history from the previous iteration and
   append it to the interface ID (IEEE 802 MAC
   address). If there is no previous history
   generate a random number
2. Compute the MD5 hash of the above.
3. Take the left-most 64-bits. Set bit 6 to zero
   thus setting the local/global bit indicating
   local. This is the interface ID.
4. Take the right-most 64-bits of the hash is step
   2) and sve them in the history value for the next
   iteration.