2001 Copyright SCUT DT&P Labs 1 IP Version 6. 2001 Copyright SCUT DT&P Labs 2 IPv6 Overview & The IPv6 Header Format

2001 Copyright 2001 Copyright SCUT DT&P LabsSCUT DT&P Labs 1

IP Version 6IP Version 6


IPv6 OverviewIPv6 Overview&&

The IPv6 Header FormatThe IPv6 Header Format


1.The main causes for change from 1.The main causes for change from IPv4 to IPv6IPv4 to IPv6

(1)Dramatically increase the number of IP addressesIP Address ExhaustionThe global internet is growing exponentially, with the size more than doubling annually.

The estimates were that the IP address space would be exhausted at some point between 2005 and 2011.


1.The main cause for change from IPv4 to IPv61.The main cause for change from IPv4 to IPv6

(2) Provide better support for real-time applications Traffic priorityFor example, applications that deliver audio and video need to deliver data at regular intervals.

To keep such information flowing through the Internet without disruption, IP must avoid changing routes frequently.


1.The main cause for change from IPv4 to IPv61.The main cause for change from IPv4 to IPv6

(3) Security features

The security implemented in IPv6 guarantees that that a packet is actually coming from the host indicated in its source address, unlike in IPv4 where the packet could be coming from a host other than that indicated in the source -this is known as “spoofing”.


2. New significant features of IPv62. New significant features of IPv6

(1) Address size: 128-bit128-bit addresses

It is said to be sufficient for the next 30

years.

There are enough addresses supported by

IPv6 to provide an order of 6×1023 unique

addresses per square meter of the surface

of the earth.



(2) Improved option mechanism

Simplifies and speeds up router

processing of IPv6 packets.

IPv6 options are placed in separate

optional headers that are located between

the IPv6 header and the transport layer

header.

Most of these optional headers are not

examined or processed by any router on the

packet’s path.



(3) Address autoconfiguration

Dynamic assignment of IPv6 addresses

A version of DHCP has been developed

for IPv6.

It maintains static tables that determine

which addresses are assigned to a new or

moved stations.



Stateless autoconfiguration makes it

possible for devices to configure their

own addresses with the help of a local

IPv6 router.



(4) Improving multicast routing support.

(5) Built-in authentication and encryption.


3. The IPv6 Packet Format3. The IPv6 Packet Format

The IPv6 datagram begins with a base header, which is followed by zero or more extension headers, followed by data.

The only header required is that of the IPv6 header. This is of fixed size with a length of 40 octets compared to 20 octets for the mandatory portion of the IPv4 header.

BaseHeader

ExtensionHeader 1

ExtensionHeader N

Data area…...

Optional40 bytes


3. The IPv6 Header Format3. The IPv6 Header Format

Version Priority Flow Label

Payload Length Next Header Hop Limit

Source Address

Destination Address

0 4 8 16 24 31

10 x

32

bit

s =

40

octe

ts



The IPv6 header has a fixed length of 40 octets, consisting of eight fields:

•Version (4 bits): IP version number; the value is 6.

•Priority (4 bits): Priority value of each packet specifies the traffic class.

Values between 0 and 7 are defined for congestion controlled traffic (data) and between 8 and 15 for non-congestion controlled traffic (video and audio).



•Flow Label (24 bits): used by applications that require a performance guarantee to specify the path.

The IPv6 standard defines a flow as a sequence of packets sent from a particular source to a particular destination.

A flow is uniquely identified by the combination of source address and a 24-bit flow label. Thus all packets that are to be part of the same flow are assigned the same flow label by the source.



•Next Header (8 bits): identifies the type of header immediately following the IPv6 header.

A TCP/UDP header (upper layer protocol) or

A IPv6 optional header (extension header).

•Payload Length (16 bits): specifies the size of the data being carried.



•Hop Limit (8 bits): the remaining number of hops for this packet.

The hop limit is set to a desired maximum value by the source and decremented by 1 by each node that forwards this packet.

The packet is discarded if the hop limit is decremented to zero.



•Source Address (128 bits): the address of the sender of the packet.

•Destination Address (128 bits): address of the intended recipient of packet.

Although the IPv6 Header is longer than that of the IPv4 header, it contains fewerfewer fields. Thus routers have less processing to do per header, which should speed up routing.



The fields in IPv4 header that no no longer appear in the IPv6 header:

Type of Service, its function can be replaced by the “Flow Labels”;

Identification, Fragmentation Flags and Fragment Offset. Higher-level protocols tend to avoid the fragmentation and an extension can be employed if Fragmentation is needed.

Header Checksum. IPv6’s optional authentication header that can also be used to ensure integrity.


4. IPv6 Extension Header

Hop-by-hop options

Extension header Description

Miscellaneous information for routers

Routing

Fragmentation

Authentication

Encrypted security payload

Destination options -2

Full or partial route to follow

Management of datagram fragments

Verification of the sender’s identity

Information about the encrypted contents

Additional information for the final destination only

Destination options -1 Information for 1st destination

Note: the extension header order


4. IPv6 Extension 4. IPv6 Extension HeaderHeadervers

The type of extension header (with exception of 59: no next header) is defined in the “Next Header”.

priority

Payload length nxt h:0

TCP header and data

Flow label

nxt h:43

Hop limit

Source address

Destination address

h length

Hop-by-hop options

nxt h: 6h length

Routing information


Hop-by-hop Options Header: •defines special options that require hop-by-hop processing.

•It must immediately follow the IPv6 header if present and is defined by the special value 0 in the Next Header field of the IPv6 basic header.

•The header contains the different length options with Type-Length-ValueType-Length-Value format.

4. IPv6 Extension 4. IPv6 Extension HeaderHeader


Hop-by-hop Options Header Type-Length-Value format

typetype lengthlength valuevalue

xxxx yy zzzzzzzzzz

Type:

xx: indicate how an IPv6 node that dose not recognize the option should treat it: skip, discard, …

Y: if set, indicate that the value of the option may change in rout and the field is excluded from any integrity calculation performed on the packet.



Hop-by-hop Options Header

zzzzz: define the option:

Pad1: A X’00 byte used for padding a single byte;

PadN: N X’00 bytes used for padding, N is given in the field of the length byte.

The padding is used to retain 8-byte alignment for subsequent headers to make processing header more efficient.



Example1

xx y zzzzz = 194: the hop-by-hop header is the Jumbo Payload Length.

This option is used to indicate a packet that has a payload size in excess of 65,535 byte.

Type:194Type:194Len.: 4Len.: 4

Jumbo Payload Length:0~4,294,967,296Jumbo Payload Length:0~4,294,967,296



Example2

xx y zzzzz = 5: the hop-by-hop header is the Router Alert.

This option is used to indicate a Router Alert information.

Type:5Type:5 Len.: 2Len.: 2

Router Alert: 0~65,535Router Alert: 0~65,535


Different number implies different alert to the routers.


•Destination Option Header -1:

Contains optional information to be examined by the first destination listed in the IPv6 address field.

This header can also be read by a subsequent destination listed in the source routing header address fields.



•Destination Options Header -2:

Contains optional information to be examined only by the final destination node.

Currently, only the Pad1 and PadN types of option are specified for the Destination Options Header.



•Routing Header:

Address [0]

nxt h h length

reserved

Type:0Addrs left

Address [n-1]


The header allows a source node to specify a list of IP addresses that dictate what path a packet will traverse.

Type: 0


Type-specific Data

nxt h h length Type Seg. leftThe generic routing header.

Other type

•Routing Header:



Routing Header

Addresser/Segment Left:

The number of intermediate nodes still to be visited on route to the final destination.

The field of a packet is decreased by one while it passes through a router.



•Fragment Header:

contains fragmentation and reassemble information.

nxt h reservedfrag. offset M

Fragment identification

res

Fragment Offset (13-bit): it indicates the data that follows relative (in 8-byte units) to the start of the original data before is was fragmented.



Fragment Header

Res (2-bit): reserved field.

M (more flag):

M = 0: the last fragment;

M = 1: not the last fragment.

Fragment Identification: an unambiguous identifier used to identify fragments of the same datagram.

Keep same value for a divided packet.



•Authentication Header: provides packet integrity and authentication.

•Encapsulated Security Payload Header (ESP): Provides privacy. All data following the ESP header is encrypted.

ESP provides encryption at the network at the network layerlayer, making it available to all applications in a highly standardised fashion.



Encapsulated Security Payload Header

Two modes to provide confidentiality:

Transport mode ESP

In this mode only the payload is encrypted.

The IP header and IP options are unencrypted and are used for routing the packet.

Unencrypted Encrypted

IPv6Header

ExtensionHeaders ESP Header

Transport Headerand Payload



Encapsulated Security Payload Header

Tunnel mode ESP

In this mode, the original IP datagram and header are encrypted.

Transport Headerand Payload

IPv6Header

ExtensionHeaders ESP Header

IPv6Header

ExtensionHeaders

Tunnel Mode

Unencrypted Encrypted



5. IPv6 Addressing5. IPv6 Addressing

IPv6 Colon Hexadecimal Notation

To help reduce the number of characters in an address, the designers of IPv6 propose using a more compact syntactic form known as hexadecimal notation;

Each group of 16 bits is written in hexadecimal with a colon separating groups;

For example:

69DC:8864:FFFF:FFFF:0:1280:8C0A:FFFF


IPv6 Colon Hexadecimal Notation

To shorten the notation of addresses, leading zeroes in any of the groups can be omitted, for example:

FE80:0000:0000:0000:0001:0800:23E7:F5DB

FE80:0:0:0:1:800:23E7:F5DB A group of all zeroes, or consecutive groups of all zeroes, can be substituted by a double colon:

FE80:0:0:0:1:800:23E7:F5DB

FE80::1:800:23E7:F5DB

The double colon shortcut can be used only once in the notation of an IPv6 address.

5. IPv6 5. IPv6 AddressingAddressing


Like IPv4, IPv6 assigns a unique address for each connection between a computer and a physical network.

There are three types of IPv6 addresses:

– Unicast

– Multicast

– Anycast

.



(1) Unicast Address

•A unicast address is an identifier assigned to a single interface;

•The address corresponds to a single computer;

•Special- purpose unicast addresses:

Loopback address ( ::1 ); It is assigned to a virtual interface over which a host can send packets only to itself; (IPv4: 127.0.0.1)

Unspecified address ( :: ); It is used as a source address by a host while performing autoconfiguration; (IPv4: 0.0.0.0)



IPv4-compatible address ( ::< IPv4_address > ): They are used when IPv6 traffic needs to be tunneled across existing IPv4 networks.

IP-mapped address ( ::FFFF:< IPv4_address > ): Addresses of this kind are used when an IPv6 host needs to communicate with an IPv4 host.

Link-local address Addresses of this kind can be used only on the physical network that’s interface is attached to.

Site-local address Addresses of this kind cannot be routed into the Internet.

(IPv4 private addresses)



GGlobal Uincast Address Formatlobal Uincast Address Format: The format is expected to become the predominant format used for IPv6 nodes connected to the Internet.

Three sections of the address format:

Public TopologyPublic Topology: It is for providers and exchanges that provide public Internet transit services.

Site TopologySite Topology: It is local to an organization that does not provide public transit service to nodes outside of the site.

Interface IdentifiersInterface Identifiers: These identify interfaces on links.



GGlobal Uincast Address Formatlobal Uincast Address Format

0 3 16 24 48 64 127

FPTALID

RESNLAID

Interface IDSLAID

Public Topology Site Interface Identifier

Topology

The field definition

FPFP: Format Prefix (001)

TLA IDTLA ID: Top-Level Aggregation Identifier ( 13-bit): The

top level in the routing hierarchy.

RESRES: Reserved for future use (8-bit).



GGlobal Uincast Address Formatlobal Uincast Address Format

NLA IDNLA ID Next-Level Aggregation Identifier (24-bit): It is used to create the second addressing hierarchy and to identify sites.

SLA IDSLA ID Site-Level Aggregation Identifier (16-bit): It is used to create a local addressing hierarchy.



(2) Multicast Address

A multicast address is an identifier assigned to a set of interfaces on multicast (broadcast) hosts;

0 8 16 127 FP Flags Group IDScope

FP Format Prefix: 1111 1111.

Flags: (only the low-order bit being defined)

0000: Permanent address assigned by a numbering authority.

0001: Transient address.



Multicast Address

Scope (4-bit): It indicates the scope of the multicasting:

0: Reserved

1: Confined to interfaces on the local node (node-local)

2: Confined to nodes on the local link (link-local)

5: Confined to the local site

8: Confined to the organization

E: Global scope

F: Reserved

Group ID: It identifies the multicast group.



Multicast Address

Certain special-purpose multicast addresses:FF01::1 All interface node-local (Defines all interface on the host itself);

FF02::1 All nodes link-local (Defines all systems on the local network);

FF01::2 All routers node-local (Defines all routers local to the host itself);

FF02::2 All routers link-local (Defines all routers on the same link as the host);

FF05::2 All routers site-local (Defines all routers on the same site as the host);



Multicast Address

Certain special-purpose multicast addresses:FF02::B Mobile agents link-local;

FF02::1:2 All DHLC agents link-local;

FF05::1:3 All HDLC servers site-local;

Note:

The flags of all above special-purpose multicast address are 0000 (defined by the numbering authority);

The function scope of the multicasting is determined by the scope field of the address;



Multicast Address

Solicited node address: It is another special-purpose multicast address, which is used by ICMPv6 for neighbor discovery and to detect duplicate addresses.

The format of a solicited node address

FF02::1:FFxx:xxxx

FF02::1:FF the prefix of the address;

xx:xxxx the last 24 bits of a nodes unicast address



(3) Anycast Address

Anycast address is a special type of unicast address that is assigned to interfaces on multiple hosts.

Packets sent to such an address are delivered to the nearest interface with that address.

The features of Anycast addresses:

Same format as unicast addresses

Must not be used as the source address

May only be assigned to a router



Anycast Address

Sub-router address: A special anycast address

An sub-router address consists of the subnet prefix for a particular subnet followed by trailing zeros.

The address may be used when a node needs to contact a router on a particular subnet.




Distribution of the IPv6 addresses & the assigning organization

APNIC (Asia & Oceania): 23%ARIN (America): 16%RIPE NCC (Europe): 49%LACNIC (Latin America & Africa): 1%IX (International Switch Center): 11%


5. IPv6 5. IPv6 AddressingAddressingDistribution of the IPv6 addresses

in Chinese mainland (up to 2003-12-19)

CERNET-CN-20000426 ( 中国教育科研网 ): 2001:0250::/32BIIV6-CN-20020704 ( 天地互连 ): 2001:03F8::/32

CHINANET-20020830 ( 中国电信 ): 2001:0C68::/32

CSTNET-CNNIC-20021015 ( 中国科技网 ): 2001:0CC0::/32

V6TNET-BII-CN-20030616 (BII 测试地址 ): 2001:0D60::/32

CNGI-CERNET2-CN-20031110 (CNGI 中国教育网 ): 2001:0DA8::/32

CERNET-CN-20031111 ( 中国教育网 ): 2001:0251::/32CRTC-CNNIC-CN-20031121 ( 中国铁通 ): 2001:0E08::/32

CNCGROUP-CN-20031219 ( 中国网通 ): 2001:0E18::/32

CNGI-BJIX-CN-20031106 (CNGI 国际交换中心 ): 2001:07FA:0005::/48


6. Priority6. Priority

The 4-bit priority field allows applications to specified a certain priority for the traffic and introduce the concept of Class of Service.

Priorities 0 to 7, for congestion-controlled traffic.

Dropping the packets while congestion

Priorities 8 to 15, for noncongestion-controlled traffic (such as real-time traffic)

Trying to forward the packets even when congestion


7. Flow Labels7. Flow Labels

Flow: a series of related packets from a source to a destination that requires a particular type of handing by the intervening routers.

Flow Label: be used to mark a specific flow.

An router may use the Flow Label ONLY to efficiently decide how to route and forward the packets.

Each flow is distinctly labeled by the 24-bit flow label field in the IPv6 packet.


Internet Control Message ProtocolInternet Control Message ProtocolVersion 6 (ICMPv6)Version 6 (ICMPv6)


1. The Functions of ICMPv61. The Functions of ICMPv6(1)Error reporting, route discovery and

diagnostics, etc. (The functions of ICMPv4).

(2) Conveying multicast group membership information (The function of IGMPv4).

(3) Address resolution (ARP protocol).

IGMP: Internet Group Management Protocol

ARP: Address Resolution Protocol

1. The Functions of ICMPv61. The Functions of ICMPv6


2. The ICMPv6 Header Format2. The ICMPv6 Header Format

The ICMPv6 is identified by a Next Header value of 58 in the immediately preceding header.

0 8 16 31

TypeType CodeCode

Body of ICMP MessageBody of ICMP Message

ChecksumChecksum



The field of ICMPv6 Header

(1)Type values:

(a) Error messages: 0 to 127

Such as Destination Unreachable (1), Packet Too big (2), Hop Count Exceeded, Parameter Problem (4), etc..

(b) Information messages: 128 to 255 Such as Echo Request (128), Echo Reply (129), Group membership Query (130), Group Membership Reduction (132), Router Solicitation (133), Router Advertisement (134), Neighbor Solicitation (135), Neighbor Advertisement (136), Redirect Message (137), etc..



The field of ICMPv6 Header

(2) Code: The code varies according to message type.

(3) Checksum: It is used to detect data corruption in the ICMPv6 message and parts of the IPv6 header.

(4) Body of Message: This varies according to message type.



3. Neighbor Discovery3. Neighbor Discovery

Neighbor Discovery enables a node to identify other hosts and routers on its links.

• Address Resolution

• Router and Prefix Discovery

• Redirection

• Neighbor Unreachability Detection



(1) Address Resolution

To look for a target’s link layer address (MAC address) according to its IPv6 address.

Solicited node address for the target workstation is used to improve IPv4 ARP performance.

Every workstation must respond to its own solicited node address, others will simply ignore it.



Address Resolution

NeighborNeighbor

SolicitationSolicitation

MessageMessage

FormatFormat

Solicited

node

address

for the

target

workstation

6 Pri Flow Label

Payload=32 Next=58 Hops=255

Source Address FE80::0800:5A12:3456

Type=135 Code=0 Checksum

Reserved = 0

Destination Address FF02::1:5A12:3458

Target Address FE80::0800:5A12:3548

OptCode=1OptLen=1

Source Link Layer Address = 08005A123456



Address Resolution

NeighborNeighbor

AdvertisementAdvertisement

MessageMessage

FormatFormat

6 Pri Flow Label


Source Address FE80::0800:5A12:3458


Reserved = 0

Destination Address FF02::1:5A12:3456

Target Address FE80::0800:5A12:3548

OptCode=2OptLen=1

Target Link Layer Address = 08005A123458

R S O



Address Resolution

The flags in the Neighbor Advertisement Message

R: Router Flag. This bit is set if the sender of the advertisements is a router.

S: Solicited Flag. This bit is set if the advertisement is in response to a solicitation.

O: Override Flag. If the bit is set, it is to inform the receiving node to update an existing cached link layer entry in its neighbor cache



Neighbor Discovery

(2) Router and Prefix Discovery

The Router address is needed for the node to reach the rest of the world.

The Prefix is necessary for the nodes to define the range of IP addresses on the same link.

Routers use ICMP to convey this information to hosts by means of router advertisements.

A router constantly sends unsolicited advertisements at a frequency defined in the router configuration.



Router and Prefix Discovery

RouterRouter

AdvertisemenAdvertisementt

MessageMessage

FormatFormat

Multicast

Address

All nodes

link-local

6 Pri Flow Label


Source Address


Router Lifetime

Destination Address FF02::1

Reachable Time

Retransmission TimerOption 1/5/3

M O RsvdHop Limit




The fields in the Router Advertisement Message

(1) Destination address: Defines all system on the local link

(2) Type 134 (Router Advertisement).

(3) Hop Limit (An default value).

(4) M 1-bit Managed Address Configuration Flag.

(5) O 1-bit Other Stateful Configuration Flag.

(6) Router Lifetime: Defines how long the node should consider this router to be available.




The fields in the Router Advertisement Message

(7) Reachable Time: Defines how long the node should assume a neighbor is still reachable after having received a response to a neighbor solicitation.

(8) Retransmission Timer: The Time that nodes should allow between the retransmission of neighbor solicitation messages if no initial response is received.




RouterRouter

AdvertisemenAdvertisementt

MessageMessage

FormatFormat

Option PartsOption Parts

OptType=1OptLen=1 Source Link Address

Prefix

Source Link Address

L A RsvdPrefix Len

OptType=5OptLen=1 Reserved

MTU

OptType=3OptLen=4

Valid Lifetime

Preferred Lifetime




The Options of Advertisement Message

Option 1Option 1: : It offers the source link address (router), so allows a receiving node to respond directly to the router without having to do a neighbor solicitation.

Option 5Option 5: This defines the maximum transmission unit (MTU) size for the link.

Option 3Option 3: This defines the address prefix for the link.




Router Solicitation Message: The nodes can use this message to solicit the router advertisement message.

The fields of the Router Solicitation Message

Destination address: the special multicast address that defines all routers on the local link.

(FF02::2 All routers link-local)

Type 133 (Router Solicitation)

Option 1: This offers source link address (a router can response at once).



6 Pri Flow Label


Source Address


Destination Address FF02::2

Reserved =0


RouterRouter

SolicitationSolicitation

MessageMessage

FormatFormat

Target Address


Source Link Address



(3) Redirection

In the case that the default router in a node is not the most suitable router for the packets, ICMPv6 allows for redirection to a more efficient path for a particular destination.

Example :

Redirect the node X’s packets sent to node Y using the the router B.



Example :

Redirect the node X’s packets sent to node Y using the the router B.


NodeNodeXXRouter_ARouter_A

Router_BRouter_B

NodeNodeYY


6 Pri Flow Label

Payload Length Next=58 Hops=255

Source Address (Router A)


Destination Address (Node X)

Reserved =0

Redirection

RedirectRedirect

MessageMessage

FormatFormat

Target Address (Router B)

Destination Address (Node Y)



Redirection

The fields of the Redirect Message Format

(1) Type 137 (Redirect)

(2) Target Address: This is the address of the router that should be used.

(3) Destination Address: The address of the destination node for it the packets to be sent.

(4) Option 2: This offers link address of the router that should be used.

(5) Option 4: the first 576 bytes (or less) of the original packet.




Source Link Address (Router B)

Reserved = 0

Reserved =0

IP Header & Data

OptType=4 OptLen

Redirection

RedirectRedirect

MessageMessage

FormatFormat

OptionsOptions



(4) Neighbor Unreachability Detection

By issuing specific neighbor solicitations to check that the path to a target is still available.



4. Stateless Address Auto-configuration4. Stateless Address Auto-configuration

The size of the IPv6 address represents a potential problem to the network administrators.

Address autoconfiguration is needs for a node to obtain its IPv6 address.

Two types of autoconfiguration:

(1) Stateful address autoconfiguration

Using DHCP to obtain its IPv6 address

(2) Stateless address autoconfiguration



The steps of Stateless Address Autoconfiguration operation:

1. During the system startup, the node obtains its interface token (48-bit MAC address) from the interface hardware.

2. The node creates a tentative link-local unicast address by combining the well-known link-local prefix with the interface token.

3. The node verifies whether its tentative address is unique or not by issuing a neighbor solicitation message.

If no neighbor advertisement in response, the link- local unicast address become available.

If there is neighbor advertisement in response, the autoconfiguration process stops.



4. When the node has its link-local address, then it send router solicitations to all-routers multicast group for the router advertisements.

5. The router advertisements can tell the node how to proceed with the autoconfiguration.

(a) Use DHCP to obtain its IP address, if M/O flag is set.

(b) Use the prefix offered and add it to the interface token to form the global unicast IP address.

6. The working node continues to receive periodic router advertisements and take action according to the advertisement changes.



7. If no router advertisement is received, the node should attempt to use DHCP to obtain the configuration information.

8. If no DHCP server responds, the node can only use the link-level address and communicate with other nodes on the same link.


5. Multicast Listener Discovery (MLD)5. Multicast Listener Discovery (MLD)

Multicast Listener Discovery

The process used by a router to discover the members of a particular multicast.

MLD is a subset of ICMPv6 and provides the equivalent function of IGMP for IPv4.


6 Pri Flow Label

Payload Length Next=58 Hops=1

( Link Local ) Source Address

Type Code=0 Checksum

Destination Address

MLDMLD

MessageMessage

FormatFormat

IP Multicast Address

ReservedMax. Response Delay

5. Multicast Listener Discovery5. Multicast Listener Discovery



Three types of MLD message

130: Multicast Listener Query

General query: used to find which multicast addresses are being listened.

Multicast-address-specific query: used to find if any node are listening for a specific multicast address.

131: Multicast listener report: used by a node to report that it is listening to a multicast address.

132: Multicast listener done: used by a node to report that it is ceasing to listen a multicast address.

Code: Set to 0 by sender and ignored by receivers



Max Response Delay:

The maximum allowed delay before a responding report must be sent.

Increase this parameter can prevent sudden bursts of high traffic if there a lot of responders on a network.

Multicast Address:

Set to zero for a general query message for a general query.

Set to the specific IPv6 multicast address for a multicast-specific-query.



Operation of the Multicast Listener Discovery

1. A router periodically sends a General Query on each of links to all-nodes link-local address (FF02::1).

2. When a node listening for any multicast addresses receives the query it sets a delay timer for each multicast address for which is listening.

3. As each timer expires, the node send a multicast listener report message containing the appropriate multicast address.

4. If a node receives another node’s report for a multicast address while it has a timer still running for that address then it stops its timer and does not send a report for that address.



Operation of the Multicast Listener Discovery

5. When a node has finished listening to a multicast address, if it was the last one on a link to send a report to the router (its timer delay was not interrupted by the receipt of another node’s report), then it send s a multicast listener done message to the router.


Domain Name Services (DNS)Domain Name Services (DNS) in IPv6in IPv6


DNS in IPv6DNS in IPv6

The Format of IPv6 Resource Records

AAAA resource record – proposed data format (RFC 1886)

Domain nameIPv6 address P

IPv6 address 128-bit address (contains only the lower bits of the address) ;

P Prefix length (0~128)

Domain Name The domain name of the prefix

The IPv6 addressing system has been designed to allow for multiple addresses on a single interface and to facilitate address renumbering.



Example: Prefix numbering

TOP1 TOP2

PROV1 PROV2

X

Top-level provider

Second-level provider

11-11 (TLA) 11-122(TLA)

00AB(NLA) 00BC(NLA)

00A1 (subscriber identifier)

00B1 (subscriber identifier)

10005A123456

TEST.COM

ND1.TEST.COM

PROV2.COMPROV1.COM

TOP2.COMTOP1.COM

00CD (NLA)



The node, ND1, is configured with two IP address:

11-11:00AB:00A1::1000:5A12:3456

11-122:00BC:00B1::1000:5A12:3456

The node can be represented by the following entries in the DNS:

ND1.TEST.COM AAAA ::1000: 5A12:3456 (48bits) 80 (Prefix length)

TP6.TEST.COM

IP6.TEST.COM AAAA 0:0:00A1:: (48bits) 32 1P6.PROV1.COM

IP6.TEST.COM AAAA 0:0:00B1:: (48bits) 32 1P6.PROV2.COM

1P6.PROV1.COM AAAA 0:00AB:: (32bits) 16 IP6.TOP1.COM

1P6.PROV2.COM AAAA 0:00BC:: (32bits) 16 IP6.TOP2.COM

IP6.TOP1.COM AAAA 11-11::

IP6.TOP2.COM AAAA 11-122::



If the site X decides to stop using links from providers PROV1 and PROV2. and invests in a connection direct from the top-level service provider TOP1, the only change necessary in the DNS would be for the two IP6.TEST.COM entries to be replaced with a single entry:

IP6.TEST.COM AAAA 0:00CD:: (32bits) 16 (Prefix length) IP6.TOP1.COM


DHCP in IPv6DHCP in IPv6


DHCP in IPv6

DHCP in IPv6:

DHCP provides a means for passing additional configuration options to nodes once they have obtained their addresses.


DHCP in IPv6

1. Differences between DHCPv6 and DHCPv4Differences between DHCPv6 and DHCPv4

Principal differences (advantage):

(a) As soon as a client boots, it has a link-local IP address,which can use to communicate with DHCP server or a relay agent;

(b) The client uses multicast addresses to contact the server, rather than broadcasts.

(c) DHCPv6 can provide more than one address when requested.

(d) Some DHCP options, which are now unnecessary, can be obtained by using IPv6 neighbor discovery.

(e) There is no requirement for BOOTP compatibility.

(f) There is a new reconfiguration messages. Clients must listen for reconfiguration messages once they have received their initial configuration.


DHCP in IPv62. DHCPv6 MessagesDHCPv6 Messages (a) DHCP Solicit (multicast message): The DHCP client forwards

the message to FF02::1:2, the well-known multicast address for all DHCP agents/servers. The relay agent forward the message to FF05::1:3, the well-known address for all DHCP servers.

(b) DHCP Advertise (unicast message): be sent by a DHCP server in response to a DHCP Solicit to the soliciting client or the relay agent.

(c) DHCP Request (unicast message): be sent by a DHCP client to the DHCP server allocated/relay agent for requesting an address and/or configuration parameters.

(d) DHCP Reply (unicast message): be sent by a DHCP server in response to a DHCP Request.

(e) DHCP Release (unicast message): be sent by a DHCP client to the server, informing it of resource that are being released.

(f) DHCP Reconfigure (unicast or multicast message ): be sent by the server to one more clients , to informing them that there is new configuration information available.


Internet Transition:Internet Transition:Migrating from IPv4 to IPv6Migrating from IPv4 to IPv6


Migrating from IPv4 to IPv61. The Transition TechniquesThe Transition Techniques Dual-stack IP implementations: for hosts and routers

that can/must interoperate between IPv4 and IPv6. Embedding of IPv4 addresses in IPv6 addresses: IPv6

hosts will be assigned addresses that are interoperable with IPv4, and IPv4 host addresses will be mapped to IPv6.

IPv6-over-IPv4 tunneling mechanisms: for carrying IPv6

packets across IPv4 router networks. IPv4/IPv6 header translation: it is intended for use when

implementation of IPv6 is well advanced and only a few IPv4-only system remains.


Migrating from IPv4 to IPv62. Dual-stack IP implementationsDual-stack IP implementations

An IPv4/IPv6 node can send and receive either IPv6 packets or IPv4 datagrams, depending on the type of system with which it is communicating.

A node has both a 128-bit IPv6 address and a 32-bit IPv4 address, which do not necessarily need to be related.

Conceptually, the dual-stack model envisages a doubling up of the protocol only in the inter-network layer. However, related changes are needed in all transport-layer in order to operate using either stack and possible in applications as well.


App

Migrating from IPv4 to IPv6

IPv6/IPv4 dual stack systemIPv6/IPv4 dual stack system

TCP/UDP

IPv4

Ethernet

App

TCP/UDP

IPv6

Ethernet

App

TCP/UDP

Ipv4 IPv6

Ethernet

IPv4 Host IPv6 HostIPv6/IPv4Host


Migrating from IPv4 to IPv63. TunnelingTunneling

When IPv6 or IPv6/IPv4 systems are separated by IPv4 networks and they wish to communicate with, then IPv6 packets must be tunneled through an IPv4 network.

The IPv6 packets is encapsulated in an IPv4 datagram: a complete IPv4 header is added to the IPv6 packet (the protocol value in the IPv4 header is 41).

Two kinds of tunneling:Automatic Tunneling.Configured Tunneling.



(a) (a) The Automatic TunnelingThe Automatic Tunneling

Automatic tunneling relies on IPv4-compatible addresses.

The decision on when to tunnel is made by an IPv6/IPv4 host that has a packet to send across an IPv4-routed network area.



The Rules of the Automatic TunnelingThe Rules of the Automatic Tunneling. If the destination is an IPv4 or an IPv4-mapped address, send the packet using IPv4 because the recipient is not IPv6-capable.. If the destination is on the same subnet, send it using IPv6 because the recipient is IPv6-capable. . If the destination is not on the same subnet but there is at least one default router on the subnet that is IPv6-capable, or there is a route configured to an IPv6 router for that destination, then send it to that router using IPv6. . If the address is an IPv4-compatible address, send the packet using automatic IPv6-over-IPv4 tunneling.



Router-to-host automatic tunnelingRouter-to-host automatic tunneling.

R1R1 R2R2IPv4IPv4NetworNetworkk

IPv4IPv4NetworNetworkk

Ethernet Ethernet

IPv6/IPv4 Host A

IPv6/IPv4 Host BIPv6/IPv4 Router IPv6/IPv4 Router

6 4 Flow lablep. len. next hops

Src: A(IPv4-compatible)

Dst: B(IPv4-compatible)

payload




payload

Dst:B (IPv4)Src:A (IPv4)Nxt:41

IPv4 Header 4




payload


4



Host-to-host automatic tunnelingHost-to-host automatic tunneling.



Ethernet Ethernet

IPv6/IPv4 Host A

IPv6/IPv4 Host BIPv4 Router IPv6/IPv4 Router




payload


4




payload


4




payload


4



(b) (b) The Configured TunnelingThe Configured Tunneling

Configured Tunneling is used for host-router or router-router tunneling of IPv6-over-Ipv4.

The IPv6 source and destination address do not need to be IPv4-compatible addresses.



Router-to-Router automatic tunnelingRouter-to-Router automatic tunneling.



Ethernet Ethernet

IPv6 Host

IPv6/IPv4 HostIPv6/IPv4 Router IPv6/IPv4 Router


Src: A(not IPv4-compatible)

Dst: B(not IPv4-compatible)

payload




payload

Dst:R2 (IPv4)Src:R1 (IPv4)Nxt:41

IPv4 Header 4




payload



4. Header Translation4. Header Translation

When the migration of networks to IPv6 reaches an advanced stage, it is likely that new systems being installed will be IPv6 only. Header Translation is required in order for IPv6-only nodes to interoperate with IPv4-only nodes. Header Translation is performed by IPv6/IPv4 routers on the boundaries between IPv6 routed areas and IPv4 routed areas.The translating router strips the header completely from IPv6 packets and replaces it with an equivalent IPv4 header (or the reverse).

Documents

2001 Copyright SCUT DT&P Labs 1 IP Version 6. 2001 Copyright SCUT DT&P Labs 2 IPv6 Overview & The IPv6 Header Format