Next Generation IP - IPv6

C O M P U T E R N E T W O R K S

IPv6 (IPng) Next Generation IP


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The main reason for migration from IPv4 to IPv6 is the small the small size of the address space in IPv4.

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An IPv6 address is 128 is 128 bits or or 16 16 bytes (octets) bytes (octets) long, four times the address length in IPv4.

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A computer normally stores the address in binary, but it is clear that 128 bits cannot easily be handled by humans. Several notations have been proposed to represent IPv6 addresses when they are handled by humans.

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The following shows two of these notations: binary and colon hexadecimal.

 Although an IPv6 address, even in hexadecimal hexadecimal format, is very long, many of the

digits are zeros. Abbreviation of the address is done by omitting the leading C O M P U T E R N E T W O R K S

zeros of a section.  For example, example, 0074 0074 can be written as 74, 74 , OOOF as F & F & 0000 0000 as 0. 0. Note that

3210 cannot be abbreviated. abbreviated .  Zero Compression can be applied to colon hex notation if there are consecutive

sections consisting of zeros only. We can remove all the zeros and replace them with a double semicolon.

 This type of abbreviation is allowed only once per address. If there is more than

one run of zero sections, only one of them can be compressed. Double Colon appears only once in the address.

 An alternate notation often used in a mixed environment environment of IPv4 and IPv6 nodes

is x:x:x:x:x:x:d.d.d.d, called as mixed notation. C O M P U T E R N E T W O R K S

 where the 'x's are the hexadecimal hexadecimal values of the six high-order 16-bit 16-bit pieces

of address and  the 'd's are the decimal values of the four low-order 8-bit pieces of the

address (IPv4 representation)

 IPv6 uses hierarchical addressing. For this reason, IPv6 allows slash or CIDR

notation. The following shows how we can define a prefix of 60 bits using CIDR.


Show Show the the unab unabbr brev evia iate ted d colo colon n hex hex nota notati tion on for for the the foll follow owing ing IPv6 addresses: a. An address with 64 0s followed by 64 1s. a. An b. An b. An address with 128 0s. c. An c. An address with 128 1s. d. An d. An address with 128 alternative 1s and 0s. Solution

a. 0000:0000:0000:0000:FFFF:FFFF:FFFF:FFFF a. b. 0000:0000:0000:0000:0000:0000:0000:0000 b. c. FFFF:FFFF:FFFF:FFFF:FFFF:FFFF:FFFF:FFFF c. d. AAAA:AAAA:AAAA:AAAA:AAAA:AAAA:AAAA:AAAA d.

Show abbreviations for the following addresses: C O M P U T E R N E T W O R K S

a. 0000:0000:FFFF:0000:0000:0000:0000:0000 a. b. 1234:2346:0000:0000:0000:0000:0000:1111 b. c. 0000:0001:0000:0000:0000:0000:1200:1000 c. d. 0000:0000:0000:0000:0000:FFFF:24.123.12.6 d.

a) 0:0:FFFF:: a) 0:0:FFFF:: b) 1234:2346::1111 1234:2346::1111 c) 0:1::1200:1000 c) 0:1::1200:1000 d) ::FFFF:24.123.12.6 ::FFFF:24.123.12.6


Deco Decomp mpre ress ss the the follo followin wing g addr addres esse ses s and and show show the the comp comple lete te unabbreviated IPv6 address: a. 1111::2222 b. :: c. 0:1:: d. AAAA:A:AA::1234 Solution

a. 1111:0000:0000:0000:0000 1111:0000:0000:0000:0000:0000:0000:2 :0000:0000:2222 222 b. 0000:0000:0000:0000:0000 0000:0000:0000:0000:0000:0000:0000:0 :0000:0000:0000 000 c. 0000:0001:0000:0000:000 0000:0001:0000:0000:0000:0000:0000: 0:0000:0000:0000 0000 d. AAAA:000A:00AA:0000:0000:0000:0000:1234 d.


The addr addres esss sp spac ace e of IPv6 IPv6 cont contai ainns 2128 addresse addresses. s. This This address space is 296 times the IPv4 address—definitely no address address depletion depletion—as shown, the size of the space is

To give some idea about the number of addresses, let us assume that the number of people on the planet earth is soon to be 2 34 (more than 16 billion). Each person can have 2 88 addresses to use. .

Unicast Address  C O M P U T E R N E T W O R K S

A unica unicast st addre address ss define definess a single single interf interface ace (comp (compute uterr or route router). r). One-to One-to-on -one e delivery to a single interface.

Anycast Address address defines a group of computers computers that all share a single address. address. A  An any cast address packet with an anycast address is delivered to only one member of the group, the most reachable one.

Multicast Address 

A multicast address also defines defines a group of computers. In anycasting, anycasting, only one copy of the packet is sent to one of the members of the group; in multicasting each member of the group receives a copy.


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Like Like the address address space of IPv4, the address address space space of IPv6 is divided divided into into seve severa rall bloc blocks ks of vary varyin ing g size size and and each each bloc block k is allo alloca cate ted d for for spec specia iall purpose.

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The followin following g table table shows only the assigne assigned d blocks. blocks. In this this table, table, the last last colu column mn show shows s the the frac fractio tion n each each bloc block k occup occupie ies s in the the whole whole addr addres ess s space..

Global Unicast Addresses  The block in the address space that is used for unicast unicast (one-to-one) communication between


two hosts in the Internet is called the global the global unicast address block. block . CIDR for the block is 2000::/3, which means that the three leftmost bits are the same for all addresses in this block (001).  The size of of this block is 2125 bits, which is more than enough for Internet expansion for many years to come. An address in this block is divided into three parts: global routing prefix (n bits), subnet identifier (m bits), and interface interface identifier (q bits).

e t e s i t n e s f i n e D

Defines subnet

Defines interface

 The global routing prefix is used to route the packet through the Internet to the

organization site, such as the ISP that owns the block. Since the first three bits in this C O M P U T E R N E T W O R K S

part are fixed (001), the rest of the 45 bits can be defined for up to 245 sites.  The global router routerss in the Internet Internet route a packet packet to its destinatio destination n site based on the

value of n. The next m bits define a subnet in an organization. This means that an

organization can have up to 216 = 65,536 subnets, which is more than enough. identifier. The interface identifier is  The last q bits (64 bits) define the interface identifier. host ide identi ntifie fierr act actual ually ly def define iness the simil similar ar to host hostid id in IPv4 IPv4 addr addres essi sing, ng, but but the the host interface, not the host.

Unlike IPv4, IPv6 allows a relation relationship ship between the hostid (at the IP level) level) and link Unlike layer address (at the data-link layer).  Two Two common linklaye linklayerr addressing addressing schemes can be considere considered d for this purpose: the

64-bit extended unique identifier (EUI-64) defined by IEEE and the 48-bit link-layer address defined by Ethernet.

Mapping EUI-64  Extended Unique Unique Identifier Identifier (EUI), as per RFC2373, allows a host to assign itself a C O M P U T E R N E T W O R K S

unique 64-Bit IP Version 6 interface identifier (EUI-64).  This feature is a key benefit over IPv4 as it eliminates the need of manual

configuration or DHCP as in the world of IPv4  To map a 64-bit physical physical address, the global/local bit of this format needs needs to be

changed from 0 to 1 (local to global) to define an interface address.

Mapping Ethernet MAC Address format address address is obtained obtained through through the 48-bit 48-bit MAC address. address. The MAC  The IPv6 EUI-64 format C O M P U T E R N E T W O R K S

address is first separated into two 24-bits, with one being OUI (Organizationally Unique Identifier) and the other being NIC specific. The 16-bit 0xFFFE is then inserted between these two 24-bits for the 64-bit EUI address. 

The addi additi tion onal al 16 bits bits are are defi define ned d as 15 ones ones followed by one zero, or FFFE16.  Nex Next, the seventh bit from the left, or the universal/local (U/L) bit, needs to be inverted. This bit identi identifie fiess whethe whetherr this this interf interface ace ident identifi ifier er is universally or locally administered. administered. If 0, the address is loca locall lly y admi admini nist ster ered ed and and if 1, the the addr addres esss is globally unique.


Q) Using the format we defined for Ethernet addresses, find the interface identifier if the Ethernet physical address is (F5-A9-23-14-7A-D2) 16

A) We only only need to change the seventh seventh bit of the first octet octet from 0 to 1, insert insert two octe octets ts FFFE FFFE16 16 and and chan change ge the the forma ormatt to colo colon n hex hex nota notati tion on.. The The resu result lt is

F7A9:23FF:FEI4:7AD2 in colon hex. Q) An orga organiz nizati ation on is assign assigned ed the the block block 2000 2000:14 :1456 56:24 :2474 74/48 /48.. What What is the IPv6 IPv6 address of an interface in the third sub net if the IEEE physical address of the computer is (F5·A9·23·14·7A.D2) 16 A) The interface identifier for this interface is F7A9:23FF:FEI4:7AD2. If we append this identifier to the global prefix and the subnet identifier, we get:

2000:1456:2474:0003:F7A9:23FF:FEI4:7 2000:1456:2474:0003:F7A9: 23FF:FEI4:7 AD2/128

Special Addresses  Addresses Addresses that use the prefix prefix (0000::/8) are reserved, but part of this block is used C O M P U T E R N E T W O R K S

to define some special addresses.

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C O M P U T E R

The unspecified address is a subblock containing only one address, which is used during bootstrap when a host does not know its own address and wants to send an inquiry to find it.

 Loopback addresses in IPv4 are represented by 127.0.0.1 to 127.255.255.255 series.

But in IPv6, only 0:0:0:0:0:0:0:1/128 represents the Loopback address. After loopback address, it can be represented represented as ::1/128. 

During the transition from from IPv4 to IPv6, hosts can can use their IPv4 addresses embedded in IPv6 addresses.

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A compatible address is an address of 96 bits of zero followed followed by 32 bits of IPv4 address. They are used dynamically to tunnel IPv6 packets over IPv4 networks. IPv6 nodes that use this technique are assigned special IPv6 unicast addresses which hold an IPv4 address in the low-order 32-bits. In IPv6-IPv4 decimal form

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::129.144.52.38 In IPv6-compressed form ::8190:3426 

A mapped address is used when a computer already migrated to version 6 wants to send an address to a computer still using version version 4.

Other Assigned Blocks  IPv6 IPv6 uses uses two two larg large e bloc blocks ks for priv privat ate e addr addres essi sing ng and and one one larg large e bloc block k for C O M P U T E R N E T W O R K S

multicasting.

subblock in a unique local unicast unicast block can be privately created and used by a site.  A subblock


This type of address has the identifier 1111 110, the next bit can be 0 or 1 to define how the address is selected (locally or by an authority). The next 40 bits are selected by the site using a randomly generated number of length 40 bits. This means that the total of 48 bits defines a subblock that looks like a global unicast address. The 40-bit

random number makes the probability of duplication of the address extremely small.

for private addresses, addresses, is the link local block . A sub block in  The second block, designed for this block can be used as a private address in a network. This type of address has the block identifier 1111111010. The next 54 bits are set to zero. The last 64 bits can be changed to define the interface for each computer.

C O M P U T E R

 IPv6 multicast communication communication is similar to IPv4 multicast multicast communication. communication. A IPv6 multicast

addres addresss identi identifie fiess multip multiple le interf interface aces. s. IPv6 IPv6 data datagr gram am pack packets addres addressed sed to an IPv6 IPv6 multicast address are delivered to all interfaces that are identified by the address. multicast addresses, the first eight eight bits are reserved as 1111 1111. Thus, the prefix  For IPv6 multicast

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of an IPv6 multicast address is ff00::/8. Similar to IPv6 Link Local addresses, it is easy to identify an IPv6 multicast multicast address, because they have left most hexadecimal hexadecimal digits as " FF“. 

The second field is a flag that that defines the group group address as either permanent permanent or transient. transient. A permanent group address is defined by the Internet authorities and can be accessed at all times. A transient group address, on the other hand, is used only temporarily.

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The third field defines the scope scope of the group address. address. The next 112 bits Group ID is used used to identify the multicast multicast group within the given scope (either permanent or transient).

interesting features features of IPv6 addressing is the autoconfigur autoconfiguration ation of hosts. In IPv6,  One of the interesting DHCP protocol can still be used to allocate an IPv6 address to a host, but a host can also configure itself. C O M P U T E R N E T W O R K S

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When a host in IPv6 joins a network, network, it can configure configure itself using the following following process: process:

1. The host first first creates creates a link local local address address for itself. itself. This is done by taking taking the 10-bit link local prefix (1111 1110 10), adding 54 zeros, and adding the 64-bit interface identifier, which any host knows how to generate from its interface card. The result is a 128-bit link local address. 2. The host then then tests tests to see if this link link local local address address is unique unique and not used used by other hosts. hosts. Since the 64-bit interface identifier is supposed to be unique, the link local address generated is unique with a high probability. to verify the uniqueness of the tentative linklocal address, a Neighbor Solicitation message is sent with the Target Target Address field that is set to the tentative link-local address. A Neighbor Advertisement message message is received, this indicates that another node on the local link is using the tentative link-local address and addre address ss autoc autoconf onfigu igura ratio tion n stops stops.. At this this point, point, manual manual confi configur gurat ation ion must must be performed on the node.

 If the uniqueness of the link local address address is passed, the host stores this address address


as its link local address, but it still needs a global unicast address. The host then sends a router solicitation message to a local router. If there is a router running on the network, the host receives a router advertisement message message that includes the global unicast prefix and the subnet prefix that the host needs to add to its interface identifier to generate its global unicast address. If the router cannot help help the the host host with with the the conf config igur urat atio ion, n, it inf informs orms the the hos host in the the route outerr advertisement message (by setting a flag). The host then needs to use other means for configuration.

C O M P U T E R

 To allow sites to change the service provider, renumbering of the address prefix

(n) was built into IPv6 addressing.  Each site is given it prefix by the service provider to which it is connected. If the

site changes the provider, the address prefix needs to be changed.  A router to which which the site is connected can advertise advertise a new prefix and let the

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site use the old prefix for a short time before disabling it.  In other words, words, during the transition transition period, a site has two prefixes.  The main problem in using the renumbering renumbering mechanism mechanism is the support of the

DNS, which needs to propagate the new addressing associated with a domain name.


The change of the IPv6 address size requires the change in the IPv4 packet format.

IPv4 & IPv6 Header Comparison IPv4 Header C O M P U T E R N E T W O R K S

Ver s i o n

IHL

Ty p e o f Ser v i c e

Id en t i f i c at i o n

Ti m e t o L i v e

IPv6 Header To t al L en g t h

Fl ag s

Pr o t o c o l

Fragment Offset

Head er Ch ec k s u m

Ver s i o n

Tr af f i c Cl as s

Payl o ad L en g t h

Fl o w L ab el

Nex t Head er

Ho p L i m i t

Source Address Add ress

Source Address Destination Destination Address Op t i o n s d n e g e L

Pad d i n g

- field field s name kept from IPv4 to IPv6 ’

- fields not kept kept in IPv6 IPv6 - Name Name & position changed in IPv6 IPv6 - New New field in IPv6 IPv6

Destination Destination Address

An IP IPv6 v6 addr addres esss is 4 time timess lar larger ger than than IP IPv4 v4,, but but surp surpri risi sing ngly ly,, the the  An header of an IPv6 address is only 2 times larger than that of IPv4. C O M P U T E R N E T W O R K S

IPv6 v6 head header erss have have one one Fix Fixed Head Header er and and zero ero or mor more Opti Option onal al  IP (Extension) Headers. All the necessary information that is essential for a router is kept in the Fixed Header. The Extension Header contains optional information that helps routers to understand how to handle a packet/flow. The IP IPv6 v6 main main head header er is requ requir ired ed for every every data datagr gram am.. It cont contain ainss  The addr address essin ing g and cont contro roll inf informat ormatio ion n that that are are used used to mana manage ge the the processing and routing of the datagram.

IPv6 fixed header is 40 bytes long and contains the following information. C O M P U T E R N E T W O R K S

Identifies the version of IP used to generate the datagram like in IPv4. Here, it carries the value 6 (0110 binary). This field replaces the Type Of Service (TOS) field in the IPv4 header. The 8-bit field is used to distinguish different payloads with different delivery requirements. This label is used to maintain the sequential flow of the packets belonging to a communication. The source labels the sequence to help the router router identify that a particular packet packet belongs to a specific flow of information. information. It is designed for streaming/real-time media. This his fiel field d is used sed to tell the the rout outers how how much much information a particular packet contains in its payload. Payload is composed of Extension Headers and Upper Layer data. With 16 bits, up to 65535 bytes can be indicated.

This field is used to indicate either the type of C O M P U T E R N E T W O R K S

Extension Header, Header, or if the Extension Header is not present then it indicates the Upper Layer PDU. The values for the type of Upper Layer PDU are same as IPv4’s. This his fiel field d is used used to stop pack packe et to loop loop in the the network infinitely. This is same as TTL in IPv4. The value of Hop Limit field is decremented by 1 as it passes a link (router/hop). When the field reaches 0 the packet is discarded. This field indicates the address of originator of the packet. This This fiel field d prov provid ides es the the addr addres esss of intended recipient of the packet.


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The payload payload in IPv6 IPv6 mea means ns a combin combinati ation on of zero zero or more more exten extensio sion n hea header derss (optio (options) ns) followed by the data from other protocols (UDP, TCP, and so on).

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The The pa payl yloa oad d can can ha have ve as ma many ny exte extens nsio ion n he head ader erss as requ requir ired ed by the the situ situat atio ion. n. Ea Each ch exten extensio sion n he heade aderr ha hass two mandat mandatory ory fields fields,, ne next xt hea header der an and d the length length,, follow followed ed by information related to the particular option.

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Each Each ne next xt he heade aderr field field value value (code) (code) define definess the type of the next hea header der (hop-by (hop-by-ho -hop p option option sourc sourcero erouti utingo ngopti ption, on, ); the last last next next he heade aderr field field define definess the protoc protocol ol (UDP (UDP

 To a router, router, a flow is is a sequence of packets that share the same characteristics,


such as traveling the same path, using the same resources, having the same kind of security, and so on.  A router router that supports the handling handling of flow labels has a flow label table. table. The table

has an entry for each active flow label; each entry defines the services required required by the corresponding flow label.  When When the router router recei receive vess a pack packet, et, it consu consults lts its flow flow label label table table to find the

corresponding entry for the flow label value defined in the packet. It then provides the packet with the services mentioned in the entry.  A flow label can be used to speed up the processing processing of a pack packet et by a rout router er.. It can

be used to support the transmission of real-time audio and video.  IPv6 datagram datagramss can be frag fragmen mented ted only by the sour source, ce, not by the routers; routers; the

reassembly takes place takes place at the destination.  The fragmentation fragmentation of packets packets at routers routers is not allowed to speed up the processing


The IPv4 header includes all options. Therefore, each intermediate router must chec check k for for thei theirr exis existe tenc nce e and and proc proces ess s them them when when pres presen ent. t. This This can can caus cause e performance degradation in the forwarding of IPv4 packets. 

With IPv6, delivery delivery and forwarding forwarding options are moved to extension headers. The only extension header that must be processed at each intermediate router is the Hop-by-Hop Options extension header. This increases IPv6 header processing speed and improves forwarding process performance.

RFC 2460 defines the following IPv6 extension headers that must be supported by all IPv6 nodes:

32

Hop-by-Hop Option C O M P U T E R N E T W O R K S

The hop-by-hop option is used when the source needs to pass information to all routers visited by the datagram. Only three hop-by-hop options have been defined: Pad 1 , PadN, and jumbo payload.  The Pad1 The Pad1 option (Option option (Option Type 0) is used to insert a single byte of padding. The PadN option (Option option (Option Type 1) is used to insert 2 or more bytes of padding.  The PadN The Jumbo Payload option (Option option (Option Type 194) is used to indicate a payload size that  The Jumbo is greater than 65,535 bytes. An IPv6 packet with a payload size greater than 65,535 bytes is named a jumbogram.

Destination Option Option The destination option is used when the source needs to pass information to the destination only. Intermediate routers are not permitted access to this information. This header is identified by the value of 60 60 in in the previous header’s Next Header field. The format of the destination option is the same as the hop-by-hop option. So far, only the Pad 1 and PadN options have been defined.

Source Routing C O M P U T E R N E T W O R K S

Similar to the loose source routing supported by IPv4, IPv6 source nodes can use the Rout Routin ing g exte extens nsio ion n head header er to spec specif ify y a loos loosee sour source ce rout route, e, a list list of inte interm rmed edia iate te destinations for the packet to travel to on its path to the final destination. The Routing header is identified by the value of 43 in the previous header’s Next Header field.

Fragmentation  The Fragment header is used for IPv6 fragmentation and reassembly services. This

header is identified by the value of 44 in the previous header’s Next Header field. Fragment header header includ includes es a Next Next Header Header field, field, a 13-bit 13-bit Fragment Fragment Offset Offset field, field, a  The Fragment More Fragments flag, and a 32-bit Identification field which work the same way as IPv4. This header cannot be used for f or jumbograms. submitted by the upper  In IPv6, only source nodes can fragment payloads. If the payload submitted layer protocol is larger than the link or path MTU, then IPv6 fragments the payload at the source and uses the Fragment Fr agment extension header to provide reassembly information. source uses uses Path MTU Discovery technique  A source Discovery technique to find the smallest MTU supported by

Authentication Authentic ation The Authenticati Authentication on header provides data authenticatio authentication n (verificati (verification on of the node that sent

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the packet), data integrity (verification that the data was not modified in transit), and antireplay protection protection (assurance (assurance that captured captured packets packets cannot cannot be retransmitt retransmitted ed and accepted as valid data) for the IPv6 packet. The Authenticat Authentication ion header is identified identified by the value of 51 in the previous previous

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header’s Next

Header field. The Authen Authentic ticati ation on extens extension ion header header does does not provid providee data data confid confident ential iality ity servic services es by

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encrypting the data. The Authentica Authentication tion header contains contains a Next Header field, a Payload Payload Length field, a Security Paramet Parameters ers Index (SPI) field that

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identifies a specific IP Security (IPsec) security association (SA), a Sequence Number field that provides anti-replay protection, and an Authentication Data field that contains an integrity check value (ICV). The ICV provides data authentication and integrity.

Encrypted Security Security Payload Payload •

The Encapsulating Encapsulating Security Security Payload Payload (ESP) header header and trailer provide data confidential confidentiality ity,, data authentication, and data integrity services to the encapsulated payload.

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The ESP header header and trailer are identified identified by the value value of 50 in the previous previous header’s Next

Int Interne rnet Con Control trol Me Mess ssag age e Prot Protoc ocol ol version ion 6 (ICMPv6) is the implem implemen enta tatio tion n of the Inter Internet net Contr Control ol Messag Message e Prot Protoc ocol ol (ICMP) (ICMP) for for Internet Protocol Protocol version 6 (IPv6).

IPv6 Main Header

Next Header

58

ICMPv6 Header

Data

The ICMPv6 packet consists of a header and the protocol payload. The header contains only three fields: type (8 bits), code (8 bits), and checksum (16 bits)

The The mess messag ages es in ICMP ICMPv6 v6 are are divid divided ed into into four four grou groups ps:: erro errorr-re repo port rtin ing g messag messages, es, inform informatio ational nal messag messages, es, neighb neighboror-dis discove covery ry messag messages, es, and group-membership messages.

Error-Reporting Messages Type 0

Meaning Destination Unreachable

Code 0

Meaning no rout routee to dest destin inat atio ion n

1

communication with destination administratively prohibited

2

beyond scope of source address

3 5

address unreachable port unreachable source address failed ingress/egress policy

6

reject route to destination

7

Error in Source Routing Header

4

2

Packet Too Big

0

3

Time Exceeded

0

hop hop limi limitt exce exceed eded ed in tran transi sitt

1

fragment reassembly time exceeded

0

erroneous header field encountered

1

unrecognized Next Header type encountered

4

Parameter Problem Message

Description A Desti estina nati tion on Unre Unreac acha habl blee messa essage ge (Typ (Typee 1) is generated in response to a packet that can not be delivered to its destination address for reasons other than congestion.

A Packet Too Big message is sent in response to a packet that it cannot cannot forward forward because because the packet is larger than the Maximum Transmission Unit (MTU) of the outgoing link. If a rout router er rece receiv ives es a pack packet et with with a hop hop limi limitt of zero zero,, or a router decrements a packet's hop limit to zero, it must discard the packet and send an ICMPv6 Time Exceeded message with Code 0 to the source of the packet. A Parameter Problem message is generated in response to an IPv6 packet with problem in its IPv6 header, or extension headers, such the node cannot

Informational Messages  The echo-request echo-request and echo-reply messages are designed to check whether whether two

devices in the Internet can communicate with each other.  A host host or rout router er can can send send an echo echo-r -req eque uest st mess messag age e to anot anothe herr host host;; the the

receiving computer or router can reply using the echo-reply message. Type

Meaning

Code

M eaning Me

Description

Echo Request Message 0 128 Ec

Used to check and troubleshoot connectivity using the IPv6 ping command.

E cho Reply Message 129 Ec

This message is generated in response to an echo request message.

0

Neighbor Discovery Messages In IPv6, two new protocols are defined: the Neighbor-Discovery (ND) protocol and the InverseNeighbor-Discovery Neighbor-Disc overy (IND) (IND) protocol. protocol. These two protocols are used by nodes (hosts or routers) on the same link (network) for three main purposes: 1. Hosts use the ND protocol protocol to find routers routers in the neighborhood that will will forward packets packets for them. 2. Nodes use the ND protocol protocol to find the link-layer link-layer addresses of neighbors neighbors (nodes attached to to the same network). 3. Nodes use the IND protocol protocol to to find the IPv6 addresses addresses of neighbors. neighbors. Type 133

Meaning Router Solicitation Message

Code 0

134

Router Advertisement Message

0

135

Neigh ighbor Solic licitation Message

0

136

Neigh ighbor Advertis tisement Message

0

137

Redirect Message

0

Meaning

Description Hosts send router solicitations messages in order to prompt routers to generate router advertisements advertisements messages quickly. Routers send out router advertisement message periodically, periodically, or in response to a router solicitation. Nodes send neighbor solicitat tations to request the linklayer address of a target node while also providing their own link-layer address to the target. A node sends neighbor advertisements in res response to neighbor solicitations and sends unsolicited neighbor advertisements in order to propagate new information quickly (which is unreliable) Routers send redirect packets to inform a host of a

Group Membership Messages 

In IPv6, the responsibility of multicast multicast delivery is given to the Multicast Listener Listener Delivery protocol.

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MLD1 is the counterpart to IGMPv2; MLDv2 is the counterpart to IGMPv3.

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Like Like IGMPv3 IGMPv3,, MLDv2 MLDv2 has two types types of messag messages: es: member membershi ship-q p-quer uery y messag message e and membership-report membership-report message.

can be divided into three subtypes: general, general, group-specific, group-specific, and group-and The first type can source specific. •

Membership-Query Message: Message: A membership-quer membership-query y message is sent by a router to find active group members in the network.

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Membership-Reportt Message: The format of the membership report Membership-Repor report in MLDv2 is exactly the same as the one in IGMPv3 except that the sizes of the fields are changed because of the address size

TRANSITION FROM IPv4 TO IPv6  Although

we have a new version of the IP protocol, how can we make the

transition to stop using IPv4 and start using IPv6?  It

will take a considerable amount of time before every system in the

Internet can move from IPv4 to IPv6.  The

transition must be smooth to prevent any problems between IPv4

and IPv6 systems.

Three hree stra strate tegi gies es hav have been been devi devise sed d for for tran transi sittion ion: dual dual st stac ack, k, tunneling,, and header translation tunneling translation.. One or all of these three strategies can be implemented during the transition period..

Dual Stack  All hosts before migrating migrating completely completely to version version 6 are recommended recommended have a dual

stack of protocols during the transition. In other words, a station must run IPv4 and IPv6 simultaneously until all the Internet uses IPv6.  To determi determine ne which version version to use when sending a packet packet to a destina destination, tion, the source host queries the DNS. If the DNS returns an IPv4 address, the source host sends an IPv4 packet or an IPv6 packet.

Tunneling strategy computers using IPv6 want to communicate with  Tunneling is a strategy used when two computers each other and the packet must pass through a region that uses IPv4. have an IPv4 address. So the IPv6 packet is  To pass through this region, the packet must have encapsulated encapsulated in an IPv4 packet when it enters the region, and it leaves its capsule when it exits the region. It seems as if the IPv6 packet enters a tunnel at one end and emerges at the other end.  To make it clear clear that the IPv4 packet packet is carrying carrying an IPv6 packet packet as data, data, the protocol protocol

value is set to 41.

Header translation strategy  Header translation translation is necessary when the majority of the Internet Internet has moved

to IPv6 but some systems still use IPv4. The sender wants to use IPv6, but the receiver does not understand IPv6.  Tunnelin unneling g does not work in this situation situation because because the packet packet must be in the

IPv4 format to be understood by the receiver. In this case, the header format must be totally changed through header translation. The header of the IPv6 packet is converted to an IPv4 header.

Next Generation IP - IPv6

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