ip v6

© 2006 Cisco Systems, Inc. All rights reserved. Cisco PublicBSCI Module 8Lessons 1 and 2 1

Module 8 Introducing IPv6 and Defining IPv6 Addressing

Postgraduate Programme

© 2006 Cisco Systems, Inc. All rights reserved. Cisco PublicBSCI Module 8

Lessons 1 and 2 2

Objectives

Explain the need for IPv6 address space.

Explain how IPv6 deals with the limitations of IPv4.

Describe the features of IPv6 addressing.

Describe the structure of IPv6 headers in terms of format and extension headers.

Show how an IPv6 address is represented.

Describe the three address types used in IPv6.


Lessons 1 and 2 3

Introducing IPv6


Lessons 1 and 2 4

Why Do We Need a Larger Address Space? Internet population

Approximately 973 million users in November 2005

Emerging population and geopolitical and address space

Mobile usersPDA, pen-tablet, notepad, and so on

Approximately 20 million in 2004

Mobile phonesAlready 1 billion mobile phones delivered by the industry

Transportation1 billion automobiles forecast for 2008

Internet access in planes – Example: Lufthansa

Consumer devicesSony mandated that all its products be IPv6-enabled by 2005

Billions of home and industrial appliances


Lessons 1 and 2 5

IP Address Allocation History

In 1981, IPv4 Protocol was published. In 1985, about 1/16 of the total IPv4 address space was in use. By mid-2001, about 2/3 of the total IPv4 address space was in use.


Lessons 1 and 2 6

IPv6 Advanced Features

Larger address space

Global reachability and flexibility

Aggregation

Multihoming

Autoconfiguration

Plug-and-play

End to end without NAT

Renumbering

Simpler header

Routing efficiency

Performance and forwarding rate scalability

No broadcasts

No checksums

Extension headers

Flow labels


Lessons 1 and 2 7

IPv6 Advanced Features (Cont.)

Mobility and security

Mobile IP RFC-compliant

IPSec mandatory(or native) for IPv6

Transition richness

Dual stack

6to4 tunnels

Translation


Lessons 1 and 2 8

Defining IPv6 Addressing


Lessons 1 and 2 9

IPv4 32 bits or 4 bytes long

4,200,000,000 possible addressable nodes

IPv6 128 bits or 16 bytes: four times the bits of IPv4

3.4 * 1038 possible addressable nodes 340,282,366,920,938,463,374,607,432,768,211,456 5 * 1028 addresses per person

Larger Address Space

~=~=~=

~=


Lessons 1 and 2 10

Address Representation

128-bit IPv6 addresses are represented by breaking them up into eight 16-bit segments.

Each segment is written in hexadecimal between 0x0000 and 0xFFFF, separated by colons.

An example of a written IPv6 address is

3ffe:1944:0100:000a:0000:00bc:2500:0d0b


Lessons 1 and 2 11

Rule 1: Leading 0’s Two rules for reducing the size of written IPv6 addresses.

The first rule is:

The leading zeroes in any 16-bit segment do not have to be written; if any 16-bit segment has fewer than four hexadecimal digits, it is assumed that the missing digits are leading zeroes.

Example

3ffe : 1944 : 0100 : 000a : 0000 : 00bc : 2500 : 0d0b

3ffe : 1944 : 100 : a : 0 : bc : 2500 : d0b


Lessons 1 and 2 12

Rule 1: Leading 0’sPractice

3ffe : 0404 : 0001 : 1000 : 0000 : 0000 : 0ef0 : bc00

3ffe : 0000 : 010d : 000a : 00dd : c000 : e000 : 0001

ff02 : 0000 : 0000 : 0000 : 0000 : 0000 : 0000 : 0005


Lessons 1 and 2 13

Rule 1: Leading 0’sPractice

3ffe : 0404 : 0001 : 1000 : 0000 : 0000 : 0ef0 : bc00

3ffe : 404 : 1 : 1000 : 0 : 0 : ef0 : bc00

3ffe : 0000 : 010d : 000a : 00dd : c000 : e000 : 0001

3ffe : 0 : 10d : a : dd : c000 : e000 : 1

ff02 : 0000 : 0000 : 0000 : 0000 : 0000 : 0000 : 0005

ff02 : 0 : 0 : 0 : 0 : 0 : 0 : 5


Lessons 1 and 2 14

Rule 1: Leading 0’s

Notice that only leading zeroes can be omitted; trailing zeroes cannot, because doing so would make the segment ambiguous.

You would not be able to tell whether the missing zeroes belonged before or after the written digits.

3ffe : 1944 : 100 : a : 0 : bc : 2500 : d0b

Correct Original Address

3ffe : 1944 : 0100 : 000a : 0000 : 00bc : 2500 : 0d0b

OR

Wrong, Ambiguous Original Address

3ffe : 1944 : 1000 : a000 : 0000 : bc00 : 2500 : d0b0


Lessons 1 and 2 15

Rule 2: Double colon :: equals 0000…0000

The second rule can reduce this address even further:

Any single, contiguous string of one or more 16-bit segments consisting of all zeroes can be represented with a double colon.

ff02 : 0000 : 0000 : 0000 : 0000 : 0000 : 0000 : 0005

ff02 : 0 : 0 : 0 : 0 : 0 : 0 : 5

ff02 : : 5

ff02::5


Lessons 1 and 2 16


Only a single contiguous string of all-zero segments can be represented with a double colon.

Example: Both of these are correct

2001 : 0d02 : 0000 : 0000 : 0014 : 0000 : 0000 : 0095

2001 : d02 :: 14 : 0 : 0 : 95

2001 : d02 : 0 : 0 : 14 :: 95

2001 : 0d02 : 0000 : 0000 : 0014 : 0000 : 0000 : 0095

2001 : d02 :: 14 : 0 : 0 : 95

OR

2001 : d02 : 0 : 0 : 14 :: 95


Lessons 1 and 2 17


Using the double colon more than once in an IPv6 address can create ambiguity.

Example

2001:d02::14::95

Illegal because the length of the two all-zero strings is ambiguous; it could represent any of the following IPv6 addresses:

2001:0d02:0000:0000:0014:0000:0000:00952001:0d02:0000:0000:0000:0014:0000:00952001:0d02:0000:0014:0000:0000:0000:0095


Lessons 1 and 2 18

Network Prefixes

IPv4, the prefix—the network portion of the address—can be identified by a dotted decimal or hexadecimal address mask or a bitcount.

255.255.255.0 or /24

IPv6 prefixes are always identified by bitcount.

The address is followed by a forward slash and a decimal number indicating how many of the first bits of the address are the prefix bits.

3ffe:1944:100:a::/64


Lessons 1 and 2 19

All 0’s IPv6 Address An IPv6 address consisting of all zeroes can be written simply with a

double colon.

Default address, as discussed previously, "Default Routes and On-Demand Routing," in which the address is all zeroes and the prefix length is zero:

0:0:0:0:0:0:0:0 Equals ::

IPv6’s Loopback address: (The Equivalent 127.0.0.1 in IPv4)

0:0:0:0:0:0:0:1 Equals ::1


Lessons 1 and 2 20

Simple and Efficient Header

A simpler and more efficient header:

The header in IPv6 has half the fields, aligned to only 64-bits

Hardware-based, efficient processing

Improved routing efficiency and performance

Faster forwarding rate with better scalability


Lessons 1 and 2 21

IPv4 and IPv6 Header Comparison

Fragment Offset

Flags

Total LengthType of Service

IHL

PaddingOptions

Destination Address

Source Address

Header ChecksumProtocolTime to Live

Identification

Version

IPv4 Header

Next Header

Hop Limit

Flow LabelTraffic Class

Destination Address

Source Address

Payload Length

Version

IPv6 Header

Field’s Name Kept from IPv4 to IPv6

Fields Not Kept in IPv6

Name and Position Changed in IPv6

New Field in IPv6Leg

end


Lessons 1 and 2 22

IPv6 Extension Headers

Simpler and more efficient header means: IPv6 has extension headers. IPv6 handles the options more efficiently. IPv6 enables faster forwarding rate and end nodes

processing.


Lessons 1 and 2 23

MTU Issues Routers handle fragmentation in IPv4, which causes a variety of

processing issues.

IPv6 routers do not perform fragmentation.

Instead, a discovery process determines the optimum maximum transmission unit (MTU) to use during a given session.

In the discovery process, the source IPv6 device attempts to send a packet at the size that is specified by the upper layers, such as the transport or application layer.

If the device receives an “ICMP packet too big” message, it retransmits the MTU discover packet with a smaller MTU and repeats the process until it gets a response that the discover packet arrived intact.

Then it sets the MTU for the session


Lessons 1 and 2 24

Three types of IPv6

The three types of IPv6 address follow:

1. Unicast

2. Anycast

3. Multicast

Unlike IPv4, there is no IPv6 broadcast address.

There is, however, an "all nodes" multicast address, which serves essentially the same purpose as a broadcast address.


Lessons 1 and 2 25

Global Unicast Addresses

A unicast address is an address that identifies a single device.

A global unicast address is a unicast address that is globally unique.

Global unicast addresses, we mean an address with global scope.

That is, an address that is globally unique and can therefore be routed globally with no modification.


Lessons 1 and 2 26


The host portion of the address is called the Interface ID.

The reason for this name is that a host can have more than one IPv6 interface, and so the address more correctly identifies an interface on a host than a host itself.

But that subtlety only goes so far:

A single interface can have multiple IPv6 addresses, and can have an IPv4 address in addition.


Lessons 1 and 2 27


Most striking difference between IPv4 addresses and IPv6 addresses, (aside from their lengths): location of the Subnet Identifier

Subnet Identifier is part of the network portion of the address rather than the host portion.


Lessons 1 and 2 28


With very few exceptions:

Interface ID is 64 bits long

Subnet ID field is 16 bits

provides for 65,536 separate subnets

The IANA and the Regional Internet Registries (RIRs) assign IPv6 prefixes—normally /32 or /35 in length—to the Local Internet Registries (LIRs).

The LIRs, which are usually large Internet Service Providers, then allocate longer prefixes to their customers. In the majority of cases, the prefixes assigned by the LIRs are /48.


Lessons 1 and 2 29


Exceptions

If the customer is very large, a prefix shorter than /48 might be assigned.

If one and only one subnet is to be addressed, a /64 might be assigned.

If one and only one device is to be addressed, a /128 might be assigned.


Lessons 1 and 2 30

Anycast Addresses

An anycast address represents a service rather than a device

The same address can reside on one or more devices providing the same service.


Lessons 1 and 2 31

Anycast Addresses A service is offered by three servers, all advertising the service at the IPv6 address

3ffe:205:1100::15.

The router, receiving advertisements for the address, does not know that it is being advertised by three different devices; instead, the router assumes that it has three routes to the same destination and chooses the lowest-cost route.

In this is the route to server C with a cost of 20.

Preferred route


Lessons 1 and 2 32

Multicast Addresses

A multicast address identifies not one device but a set of devices—a multicast group.

A packet being sent to a multicast group is originated by a single device; therefore a multicast packet normally has a unicast address as its source address and a multicast address as its destination address.

A multicast address never appears in a packet as a source address.

IPv6 does not have a reserved broadcast address like IPv4, but it does have a reserved all-nodes multicast group. (FF02::1)


Lessons 1 and 2 33

Multicast Addresses


Lessons 1 and 2 34

Summary IPv6 is a powerful enhancement to IPv4. Features that

offer functional improvement include a larger address space, simplified header, and mobility and security.

IPv6 increases the number of address bits by a factor of four, from 32 to 128.

The IPv6 header has 40 octets and is simpler and more efficient than the IPv4 header.

IPv6 addresses use 16-bit hexadecimal number fields separated by colons (:) to represent the 128-bit addressing format.

The three types of IPv6 addresses are unicast, multicast, and anycast.


Lessons 1 and 2 35

Resources

IPv6 Addressing At-A-Glancehttp://cisco.com/application/pdf/en/us/guest/tech/tk872/c1550/cdccont_0900aecd8026003d.pdf

IPv6 Extension Headers Review and Considerationshttp://cisco.com/en/US/partner/tech/tk872/technologies_white_paper0900aecd8054d37d.shtml

IPv6 Headers At-A-Glancehttp://cisco.com/application/pdf/en/us/guest/tech/tk872/c1482/cdccont_0900aecd80260042.pdf

Education

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