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© 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.
© 2006 Cisco Systems, Inc. All rights reserved. Cisco PublicBSCI Module 8
Lessons 1 and 2 3
Introducing IPv6
© 2006 Cisco Systems, Inc. All rights reserved. Cisco PublicBSCI Module 8
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
© 2006 Cisco Systems, Inc. All rights reserved. Cisco PublicBSCI Module 8
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.
© 2006 Cisco Systems, Inc. All rights reserved. Cisco PublicBSCI Module 8
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
© 2006 Cisco Systems, Inc. All rights reserved. Cisco PublicBSCI Module 8
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
© 2006 Cisco Systems, Inc. All rights reserved. Cisco PublicBSCI Module 8
Lessons 1 and 2 8
Defining IPv6 Addressing
© 2006 Cisco Systems, Inc. All rights reserved. Cisco PublicBSCI Module 8
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
~=~=~=
~=
© 2006 Cisco Systems, Inc. All rights reserved. Cisco PublicBSCI Module 8
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
© 2006 Cisco Systems, Inc. All rights reserved. Cisco PublicBSCI Module 8
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
© 2006 Cisco Systems, Inc. All rights reserved. Cisco PublicBSCI Module 8
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
© 2006 Cisco Systems, Inc. All rights reserved. Cisco PublicBSCI Module 8
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
© 2006 Cisco Systems, Inc. All rights reserved. Cisco PublicBSCI Module 8
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
© 2006 Cisco Systems, Inc. All rights reserved. Cisco PublicBSCI Module 8
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
© 2006 Cisco Systems, Inc. All rights reserved. Cisco PublicBSCI Module 8
Lessons 1 and 2 16
Rule 2: Double colon :: equals 0000…0000
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
© 2006 Cisco Systems, Inc. All rights reserved. Cisco PublicBSCI Module 8
Lessons 1 and 2 17
Rule 2: Double colon :: equals 0000…0000
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
© 2006 Cisco Systems, Inc. All rights reserved. Cisco PublicBSCI Module 8
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
© 2006 Cisco Systems, Inc. All rights reserved. Cisco PublicBSCI Module 8
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
© 2006 Cisco Systems, Inc. All rights reserved. Cisco PublicBSCI Module 8
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
© 2006 Cisco Systems, Inc. All rights reserved. Cisco PublicBSCI Module 8
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
© 2006 Cisco Systems, Inc. All rights reserved. Cisco PublicBSCI Module 8
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.
© 2006 Cisco Systems, Inc. All rights reserved. Cisco PublicBSCI Module 8
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
© 2006 Cisco Systems, Inc. All rights reserved. Cisco PublicBSCI Module 8
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.
© 2006 Cisco Systems, Inc. All rights reserved. Cisco PublicBSCI Module 8
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.
© 2006 Cisco Systems, Inc. All rights reserved. Cisco PublicBSCI Module 8
Lessons 1 and 2 26
Global Unicast Addresses
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.
© 2006 Cisco Systems, Inc. All rights reserved. Cisco PublicBSCI Module 8
Lessons 1 and 2 27
Global Unicast Addresses
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.
© 2006 Cisco Systems, Inc. All rights reserved. Cisco PublicBSCI Module 8
Lessons 1 and 2 28
Global Unicast Addresses
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.
© 2006 Cisco Systems, Inc. All rights reserved. Cisco PublicBSCI Module 8
Lessons 1 and 2 29
Global Unicast Addresses
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.
© 2006 Cisco Systems, Inc. All rights reserved. Cisco PublicBSCI Module 8
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.
© 2006 Cisco Systems, Inc. All rights reserved. Cisco PublicBSCI Module 8
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
© 2006 Cisco Systems, Inc. All rights reserved. Cisco PublicBSCI Module 8
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)
© 2006 Cisco Systems, Inc. All rights reserved. Cisco PublicBSCI Module 8
Lessons 1 and 2 33
Multicast Addresses
© 2006 Cisco Systems, Inc. All rights reserved. Cisco PublicBSCI Module 8
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.
© 2006 Cisco Systems, Inc. All rights reserved. Cisco PublicBSCI Module 8
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
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