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May, 2007: American Registry for Internet Numbers (ARIN)

“advises the Internet community that migration to IPv6 numbering resources is necessary for any applications which require ongoing availability of contiguous IP numbering resources”

US Government has mandated that all agencies support IPv6 in their backbone networks by June, 2008.

Microsoft Windows 7 defaults to IPv6

Recent Developments in IPv6

Chapter 31 - A Next Generation IP (IPv6)

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31.6 Features of IPv6

● Larger Addresses

● Extended Address Hierarchy

● Flexible Header Format

Not backward compatible with IPv4! Dual stacks

● Improved Options

● Provision for Protocol Extension

● Support for Autoconfiguration and Renumbering

● Support for Resource Allocation

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Recall IPv4 Datagram Format

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31.7 General Form of an IPv6 Datagram

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31.8 IPv6 Base Header Format

Changes from IPv4

● Alignment has been changed from 32-bit to 64-bit

● Header Length field has been replaced by Payload Length (base header fixed length of 40 bytes)

●Address fields now 16 octets 128-bit

● Fragmentation information moved out of fixed header into extension

● TIME-TO-LIVE replaced by HOP LIMIT

● SERVICE TYPE field renamed TRAFFIC CLASS and extended with a FLOW LABEL field

● PROTOCOL field replaced by NEXT HEADER field

● No HEADER CHECKSUM field

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31.9 IPv6 Extension Headers

With 32 octets needed for source and destination addresses, IPv6 datagram header is already much larger than IPv4 (20 bytes).

Hold header down to 40 bytes by moving all data not needed in all cases into extension headers

Eg. Fragmentation, source routing, authentication.

IPv6 extension header are similar to IPv4 options. Each datagram includes extension headers for only those facilities that the datagram uses.

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31.10 Parsing an IPv6 Datagram

Hop-by-hop headers precede end-to-end headers.

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31.11 IPv6 Fragmentation and Reassembly – omit

31.12 Consequences of End-to-End Fragmentation - omit

31.13 IPv6 Source Routing - omit

31.14 IPv6 Options - omit

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31.15 Size of the IPv6 Address Space

1024 addresses per square meter of the earth’s surface!

Every person on the planet can have a private internet the size of the present global Internet.

Assigning all possible addresses at a rate of one million million

per sec would take 1020 years.

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31.16 IPv6 Colon Hexadecimal Notation

128-bit address in dotted-decimal form:

104.230.140.100.255.255.255.255.0.0.17.128.150.10.255.255

Same 128-bit address in colon-hexadecimal form:

68E6:8C64:FFFF:FFFF:0:1180:96A:FFFF

Compression:

FF05:0:0:0:0:0:0:B3

written as FF05::B3

(left-align what is to left of :: right-align what is to right)

CIDR-like: 12AB::CD30:0:0:0:0 /60

means high-order 60 bits of address are 12AB00000000CD3

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31.17 Three Basic IPv6 Address Types

31.18 Duality of Broadcast and Multicast – omit

31.19 Engineering Choice and Simulated Broadcast - omit

● Anycast

● Multicast

● Unicast

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31.20 Proposed IPv6 Address Space Assignment

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31.21 Embedded IPv4 Addresses and Transition

The 16-bit field contains 0000 if the host also has a “conventional” IPv6 address, FFFF if it does not.

Transition: expect to run dual IPv4 IPv6 stacks for many years

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31.22 Unspecified and Loopback Addresses

0:0:0:0:0:0:0:0 is an unspecified address

(used at startup of a machine that does not yet have

an assigned IPv6 address – same in IPv4)

0:0:0:0:0:0:0:1 is the loopback address

(like 127.0.0.0 in IPv4)

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31.23 Unicast Address Structure

Situation with IPv6 unicast addresses:

The expanded address space allows the interface hardware address to be embedded in the IPv6 address (next slide).

Recall situation with IPv4 subnetting (fig 9.3):

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31.24 Interface Identifiers

The EUI-64 standard specifies how a 48-bit Ethernet address can be expanded to 64 bits.

Recall that the high-order 24 bits identify the manufacturer (“company”)

Low order 24 bits are serial number (“manufacturer’s extension”)

Fig 31.11

This is used in IPv6 Link-Local Addresses

F F F E

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31.25 Local Addresses

“In addition to the global unicast addresses described above, IPv6 includes prefixes for unicast addresses that have local scope …”

These are link-local addresses restricted to the local network (IPv6 datagrams so addressed cannot cross a router).

The first 10 bits are (from fig. 31.8)

1111 1110 10

If the following 6 bits are zero, this would be hexadecimal FE80

The low-order 64 bits encode the interface’s hardware address

Example from network lab machine F1:

Ethernet address: 00:B0:D0:63:5B:92

Link-local address: FE80::2B0:D0FF:FE63:5B92

No need for ARP in IPv6!

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Ethernet address: 00:B0:D0:63:5B:92Link-local address: FE:80::2B0:D0FF:FE63:5B92

00000010

F F F E 6 3 5 B 9 2B 0 D 0 0 2

So the complete IPv6 address of eth1 on F1 is

FE:80::2B0:D0FF:FE63:5B92

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31.26 Autoconfiguration and Renumbering

In IPv4 we had Dynamic Host Configuration Protocol that allowed a DHCP server to assign IPv4 addresses.

The same option exists in IPv6 – DHCPv6

An alternative is serverless autoconfiguration

that effectively uses a host’s default router as a DHCP server.

Renumbering:

“not straightforward in any practical sense”!

END OF COURSE!!!

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