Module 8- Lessons 1 and 2 Explaining IPv6IPv6 Addressing docx

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BSCI Module 8 Lessons 1 and 2

Explaining IPv6

IPv6 Addressing

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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

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Why Do We Need a Larger Address

Space?

 Internet population

– Approximately 973 million users in November 2005

– Emerging population and geopolitical and address space

– 1 billion automobiles forecast for 2008

– Internet access in planes – Example: Lufthansa

 Consumer devices

– Sony mandated that all its products be IPv6-enabled by 2005

– Billions of home and industrial appliances

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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

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IPv6 Advanced Features

Larger address space

 Global reachability and

 No broadcasts

 No checksums

 Extension headers

 Flow labels

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IPv6 Advanced Features (Cont.)

Mobility and security

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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 * 10 38 possible addressable nodes

• 340,282,366,920,938,463,374,607,432,768,211,456

• 5 * 10 28 addresses per person

Larger Address Space

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Larger Address Space Enables Address

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2 How many bits are included in an IPv6 address?

3 How will IPv6 enable smaller routing tables in Internet

routers?

4 Why is NAT not a requirement for IPv6?

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Addressing

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Simple and Efficient Header

A simpler and more efficient header means:

 64-bit aligned fields and fewer fields

 Hardware-based, efficient processing

 Improved routing efficiency and performance

 Faster forwarding rate with better scalability

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MTU Issues

 Minimum link MTU for IPv6 is 1280 octets

(vs 68 octets for IPv4)

–On links with MTU < 1280, link-specific fragmentation and reassembly must be used

 Implementations are expected to perform path MTU

discovery to send packets bigger than 1280

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IPv4 and IPv6 Header Comparison

Fragment Offset Flags

Total Length

Type of Service IHL

Padding Options

Destination Address Source Address

Header Checksum Protocol

Flow Label

Traffic Class

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IPv6 Extension Headers

Simpler and more efficient header means:

 IPv6 has extension headers

 IPv6 enables faster forwarding rate and end nodes

processing

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IPv6 Address Representation

 x:x:x:x:x:x:x:x, where x is a 16-bit hexadecimal field

 Leading zeros in a field are optional:

–2031 :0: 130F :0:0:9C0: 876A:130B

 Successive fields of 0 can be represented as ::, but only

once per address

Examples:

2031:0000:130F:0000:0000:09C0:876A:130B 2031:0:130f :: 9c0:876a:130b

FF01:0:0:0:0:0:0:1 >>> FF01::1 0:0:0:0:0:0:0:1 >>> ::1

0:0:0:0:0:0:0:0 >>> ::

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IPv6—Addressing Model

 Addresses are assigned to interfaces

–Change from IPv4 mode:

 Interface ―expected‖ to have multiple addresses

 Addresses have scope

–Link Local –Unique Local –Global

 Addresses have lifetime

–Valid and preferred lifetime

Link Local Unique Local

Global

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IPv6 Address Types

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IPv6 Address Types

 Unicast

– Address is for a single interface.

– IPv6 has several types (for example, global and IPv4 mapped).

 Multicast

– One-to-many

– Enables more efficient use of the network

– Uses a larger address range

 Anycast

– One-to-nearest (allocated from unicast address space).

– Multiple devices share the same address.

– Source devices send packets to anycast address.

– Routers decide on closest device to reach that destination.

– Suitable for load balancing and content delivery services.

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Link-Local Address

 The unicast link-local address is scoped and is used only

between nodes connected on the same local link The local address is used by several IPv6 mechanisms, such as Neighbor Discovery Protocol (NDP).

link- When an IPv6 stack is enabled on a node, one link-local address

is automatically assigned to each interface of the node at boot time.

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Site-Local Address

 A site-local address is another unicast scoped

address to be used only within a site Site-localaddresses are not enabled by default on nodes likelink-local addresses, meaning that they must beassigned

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Aggregatable Global Unicast Address

 Aggregatable global unicast addresses are IPv6

addresses used for the generic IPv6 traffic on the IPv6Internet

 Each aggregatable global unicast IPv6 address has

three parts as below:

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Unicast Prefixes

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Multicast Address

 Multicast is a technique in which a source node sends a

single packet to multiple destinations simultaneously (one-to-many)

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Multicast Address

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Multicast Assigned Address

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Solicited-Node Multicast Address

 The second type of multicast addressing is solicited-node

multicast addressing For each unicast and anycast address configured on an interface of a node or router, a corresponding solicited-node multicast address is automatically enabled The solicited-node multicast address is scoped to the local link.

 The solicited-node multicast address consists of the prefix FF02:

:1:FF00:0000/104 and the low-order 24-bit of the unicast or anycast address.

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Anycast Address

 Unicast is a method used by a source node to send a

packet to one destination (one-to-one), multicast is used for one-to-many communication, and anycast

is used for one-to-nearest communication

 Anycast addresses use aggregatable global unicast

addresses They can also use site-local or link-localaddresses Note that it is impossible to distinguish ananycast address from a unicast address

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Loopback Address

 Similar to the IPv4 protocol , each device has one

loopback address, which is used by the node itself

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Unspecified Address

 An unspecified address is a unicast address not

assigned to any interface It indicates the absence of anaddress and is used for special purposes

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Required IPv6 Addresses for Nodes

 As soon as the node is IPv6-enabled, i t has one

link-local address per interface, one loopback address, and

al l -nodes multicast addresses FF01: :1 and FF02: :1

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Required IPv6 Addresses for Routers

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 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

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BSCI Module 8 Lesson 3

Dynamic IPv6 Address

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 Explain how Ethernet MAC addresses can be used to

generate a 64-bit interface ID for the host

 Explain how IPv6 improves multicast

 Describe how IPv6 simplifies mobile IP connections

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Aggregatable Global Unicast Addresses

Aggregatable Global Unicast Addresses Are:

 Addresses for generic use of IPv6

 Structured as a hierarchy to keep the aggregation

001

64 Bits

3 45 Bits 16 Bits

Provider Site Host

Global Routing Prefix Subnet Interface ID

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IPv6 Interface ID

 Cisco uses the extended universal identifier (EUI)-64

format to do stateless autoconfiguration

 This format expands the 48-bit MAC address to 64 bits

by inserting ―FFFE‖ into the middle 16 bits

 To make sure that the chosen address is from a unique

Ethernet MAC address, the universal/local (U/L bit) is set to 1 for global scope (0 for local scope)

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MAC Address to EUI-64

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Link-Local Address

devices (similar to ARP but at Layer 3)

Remaining 54 bits

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Examples of Permanent Multicast

Addresses

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 Used in neighbor solicitation messages

 Multicast address with a link-local scope

 Solicited-node multicast consists of prefix + lower 24

bits from unicast, FF02::1:FF:

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R1#sh ipv6 int e0

Ethernet0 is up, line protocol is up

IPv6 is enabled, link-local address is FE80::200:CFF:FE3A:8B18

No global unicast address is configured

Joined group address(es):

FF02::1

FF02::2

FF02::1:FF 3A:8B18

MTU is 1500 bytes

ICMP error messages limited to one every 100 milliseconds

ICMP redirects are enabled

ND DAD is enabled, number of DAD attempts: 1

ND reachable time is 30000 milliseconds

ND advertised reachable time is 0 milliseconds

ND advertised retransmit interval is 0 milliseconds

ND router advertisements are sent every 200 seconds

ND router advertisements live for 1800 seconds

Hosts use stateless autoconfig for addresses.

R1#

Router Interface

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Anycast

 An IPv6 anycast address is a global unicast address that

is assigned to more than one interface

packet to one destination (one-to-one), multicast is used

anycast address of the nearest node member of the

anycast group

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 Internet Control Message Protocol for IPv6 (ICMPv6)

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(ICMPv6)

 ICMP for IPv6 (ICMPv6), as defined in RFC 2463, handles

messages supported by ICMP for IPv4 (ICMPv4) and has additional messages for the specific operation of the IPv6 protocol

 ICMPv6 handles the same basic errors and informational

messages as ICMPv4 such as Destination Unreachable, Packet Too Big, Time Exceeded, Echo Request, and Echo Reply.

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Internet Control Message Protocol for

IPv6 (ICMPv6)

 In IPv6, several mechanisms and functional i ties of

the protocol use ICMPv6 messages:

– Replacement of the Address Resolution Protocol(ARP) A mechanism used on local-link scope toreplace ARP in IPv4

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Path MTU Discovery (PMTUD) for IPv6

 The main goal of PMTUD is finding out the MTU value

along a path when a packet is sent to a destination to

avoid fragmentation

 As defined in RFC 1981, Path MTU Discovery for IP

version 6, PMTUD for IPv6 uses ICMPv6 error message Type 2, Packet Too Big.

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Neighbor Discovery Protocol (NDP)

 Neighbor Discovery Protocol (NDP), as defined in

RFC 2461, Neighbor Discovery for IP Version 6 (IPv6), is a key protocol of IPv6

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Replacement of ARP Protocol

 In IPv6, the determination of nodes’ link-layer

addresses uses a combination of neighbor solicitation

advertisement messages (ICMPv6 Type 136), and

:1:FFxx:xxxx)

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Stateless Autoconfiguration

 As defined in RFC 2462, IPv6 Stateless Address

Autoconfiguration, stateless autoconfiguration is one of the most interesting and useful new feature

of IPv6

 This section describes the mechanisms involved in

stateless autoconfiguration Mechanisms are asfollows:

– Prefix advertisement— Advertises prefixes and parameters

on a local l ink The prefix advertisement information is used by IPv6 nodes to configure thei r IPv6 addresses.

–DAD— Ensures that each IPv6 address configured on an interface using stateless autoconfiguration is unique on the l ink local scope.

–Prefix renumbering— Advertises modi fied prefixes or new prefixes and parameters on the local l ink to renumber a prefix

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Prefix Advertisement

 Prefix advertisement is the initial mechanism

involved in stateless autoconfiguration. The prefixadvertisement mechanism uses router advertisementmessages (ICMPv6 Type 134) and all -nodes multicastaddress FF02: :1 Router advertisement messages aresent periodically on the local link to the all -nodes multicast address

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Prefix Advertisement

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Requesting Router Advertisement Using Router Solicitation

 When nodes boot, any node can send a router solicitation

message (ICMPv6 Type 133) to the all -routers multicast address FF02: :2 on the local link When the router solicitation message is received, a router on the local link responds with a router advertisement message (ICMP Type 134) using the al l - nodes multicast address FF02: :1.

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 DAD uses neighbor solicitation messages (ICMPv6

Type 135) and solicited-node multicast addresses toperform this task

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How Prefix Renumbering Works

 Prefix renumbering is performed by routers already

advertising prefixes on local links This mechanismuses the same ICMPv6 messages and multicastaddresses as the prefix advertisement mechanism

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Router Redirection

 Router redirection is an NDP mechanism in IPv6

Routers use ICMPv6 redirection messages to informnodes on the l ink that a better router exists on the l ink

to forward packets

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Stateless Autoconfiguration

 A router sends network information to all the nodes on the local

link

 A host can autoconfigure itself by appending its IPv6 interface

identifier (64-bit format) to the local link prefix (64 bits)

 The result is a full 128-bit address that is usable and guaranteed to

Tiêu đề	Explaining IPv6
Trường học	Bachkhoa Networking Academy
Chuyên ngành	Networking
Thể loại	lecture notes
Năm xuất bản	2008

Định dạng
Số trang	71
Dung lượng	1,59 MB