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Chapter 4 Internet Protocol- IPv6. The Role of IP. Chapter 4 Internet Protocol- IPv6. The Role of IP. IPv6 Header Format. +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |Version| Traffic Class | Flow Label |

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slide3

IPv6 Header Format

+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

|Version| Traffic Class | Flow Label |

+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

| Payload Length | Next Header | Hop Limit |

+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

| |

+ +

| |

+ Source Address +

| |

+ +

| |

+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

| |

+ +

| |

+ Destination Address +

| |

+ +

| |

+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

a comparison of two headers
Six fields were suppressed:

Header Length, Type of Service, Identification, Flags, Fragment Offset, Header Checksum.

Three fields were renamed:

Length (payload length), Protocol Type (next header), Time to Live (hop limit)

The option mechanism was entirely revised.

Two new fields were added:

Traffic Class and Flow Label (to handle the real-time traffic).

Three major simplifications

Assign a fixed format to all headers (40 bytes)

128-bit network addresses

Remove the header checksum

Remove the hop-by-hop segmentation procedure

Built-in security

Chapter 4 Internet Protocol- IPv6

A Comparison of Two Headers
slide6

Chapter 4 Internet Protocol- IPv6

Important Features-Summary

  • expanded addressing and routing capabilities
  • The IP address size is increased from 32 bits to 128 bits
  • providing support for a much greater number of addressable
  • nodes, more level of addressing hierarchy. Also support
  • multicast and anycast.
slide7

Chapter 4 Internet Protocol- IPv6

Important Features-Summary

  • simplified header format
  • Even though the IPv6 addresses are four time longer than the
  • IPv4 addresses, the IPv6 header is only twice the size of the
  • IPv4 header. It contains fewer fields (8 versus 12). Thus,
  • routers have less processing to do per header, which would
  • speed up routing.
slide8

Chapter 4 Internet Protocol- IPv6

Important Features-Summary

  • support for extension headers and options
  • IPv6 options are placed in separate headers that are located in
  • the packet between the IPv6 header and the transport-layer
  • header. Since most IPv6 option headers are not examined
  • or processed by any router along a packet’s delivery path, it
  • facilitates a major improvement in router performance.
slide9

Chapter 4 Internet Protocol- IPv6

Important Features-Summary

A key extensibility feature of IPv6 is the ability to encode, within the option, the action which a router or host should perform if the option is unknown (can not discard the packet) . This permits the incremental deployment of additional functionality into an operational network with a minimal danger of disruption.

slide10

Chapter 4 Internet Protocol- IPv6

Important Features-Summary

  • support for authentication and privacy
  • IPv6 includes the definition of an extension which provides
  • support for authentication and data integrity. This extension
  • is included as a basic element of IPv6 and support for it will
  • be required in all implementations.
  • IPv6 also includes the definition of an extension to support
  • confidentiality by means of encryption. Support for this
  • extension will be strongly encouraged in all implementations.
slide11

Chapter 4 Internet Protocol- IPv6

Important Features-Summary

  • quality of service capabilities
  • A new capability is added to enable the labeling of packets
  • belonging to particular traffic “flows” for which the sender
  • has requested special handling, such as non-default quality
  • of service or “real-time” service.
slide12

Chapter 4 Internet Protocol- IPv6

The IPv6 Header

Version: version of IP. All datagrams will have a value of 6.

Traffic Class

The 8-bit Traffic Class field in the IPv6 header is available for use by originating nodes and/or forwarding routers to identify and distinguish between different classes or priorities of IPv6 packets.

Detailed definitions of the syntax and semantics of all or some of the IPv6 Traffic Class bits, whether experimental or intended for eventual standardization, are to be provided in separate documents.

slide13

Chapter 4 Internet Protocol- IPv6

The IPv6 Header

  • The following general requirements apply to the Traffic Class field:
  • The service interface to the IPv6 service within a node must provide a means for an upper-layer protocol to supply the value of the Traffic Class bits in packets originated by that upper-layer protocol. The default value must be zero for all 8 bits.
slide14

Chapter 4 Internet Protocol- IPv6

The IPv6 Header

Traffic Flows

slide15

Chapter 4 Internet Protocol- IPv6

The IPv6 Header

Traffic Flows

All traffic for any particular flow should require the same handling by the network.

All datagrams on the same flow must have the same destination, and they must all contain the same options for routers along the path.

Routers can consult a table to process the packets from the same flows. (Thus, save packets processing time.)

slide16

Chapter 4 Internet Protocol- IPv6

The IPv6 Header

Flow Label

Since the combination of flow label and source address uniquely defines a flow, the source system must choose the label to achieve this uniqueness. To help routers optimize any route caches, the IPv6 standard further requires the choice to be (pseudo)-random and uniform, ranging from 1 to 0xFFFFF.

slide17

Chapter 4 Internet Protocol- IPv6

The IPv6 Header

Flow Label

When routers choose to use flow labels in this manner (routing based on flow label only), they cannot keep information for any flow label longer than a maximum lifetime (6 seconds) specified in state-establishment mechanism. After the maximum life time, the router must forget a cache entry, perhaps relearning it when the next packet for the flow appears.

This time limit is needed in case a host resets and begins reusing its flow label values.

slide18

Chapter 4 Internet Protocol- IPv6

The IPv6 Header

  • Flow Label:reserve amount of resources
    • This is a special service, then the six-second time limit may not be appropriate (may use RSVP to establish the flow connection).
    • Flow’s time limit exceeds six seconds, a host must refrain from using flow labels for more than six seconds
slide19

Chapter 4 Internet Protocol- IPv6

The IPv6 Header

Payload Length

The payload length field (16 bits) indicates the total length of the IP datagram in bytes, less the IP basic header itself.

It normally limits IP datagrams to 65535 bytes.

slide20

Chapter 4 Internet Protocol- IPv6

The IPv6 Header

Next Header

The next header field identifies which header follows the basic IP header in the datagram.

IP Next Header Values

0 Hop-by-Hop Options Header 46 Resource Reservation Protocol

4 Internet Protocol 50 Encapsulating Security Payload

6 Transmission Control Protocol 51 Authentication Header

17 User Datagram Protocol 58 Internet Control Message Protocol

43 Routing Header 59 No Next Header

44 Fragment Header 60 Destination Options Header

45 Interdomain Routing Protocol

slide21

Chapter 4 Internet Protocol- IPv6

The IPv6 Header

Next Header

IPv6 Header

Next Header=TCP

TCP Header

IPv6 Header

Next Header=

Routing

Routing Header

Next Header=

TCP

TCP Header

IPv6 Header

Next Header=

Routing

Routing Header

Next Header=

Fragment

Fragment Header

Next Header=

TCP

TCP Header

slide22

Chapter 4 Internet Protocol- IPv6

The IPv6 Header

Hop Limit

The hop limit field determines how far a datagram will travel. When a host creates a datagram, it sets the hop limit to some initial value. Then as the datagram travels through routers on the network, each router decrements this field by one. If the datagram’s hop limit becomes zero before it reaches its destination, the datagram is discarded.

slide23

Chapter 4 Internet Protocol- IPv6

The IPv6 Header

Hop Limit

The hop limit serves two purposes. First, it breaks routing loops.

Router A thinks (incorrectly) that Laptop is connected to router B.

slide24

Chapter 4 Internet Protocol- IPv6

The IPv6 Header

Hop Limit

Hop limit lets a host perform an expanding search across the network.

slide25

Chapter 4 Internet Protocol- IPv6

The IPv6 Header

Source Address 128-bit address of the originator of the

packet.

Destination Address 128-bit address of the intended recipient

of the packet (possibly not the ultimate

recipient, if a Routing header is present).

slide26

Chapter 4 Internet Protocol- IPv6

IP Extension Headers

IP extension header provides a simple mechanism to convey extra information to the destination or to intermediate systems along the path.

IP Next Header Values

0 Hop-by-Hop Options Header 46 Resource Reservation Protocol

4 Internet Protocol 50 Encapsulating Security Payload

6 Transmission Control Protocol 51 Authentication Header

17 User Datagram Protocol 58 Internet Control Message Protocol

43 Routing Header59 No Next Header

44 Fragment Header60 Destination Options Header

45 Interdomain Routing Protocol

slide27

Chapter 4 Internet Protocol- IPv6

IP Extension Headers

The structure allows IP to string multiple extension headers together. The final extension header uses its next header field to identify the upper-level protocol.

slide28

Chapter 4 Internet Protocol- IPv6

Header Order

The contents and semantics of each extension header determine whether or not to proceed to the next header.

Therefore, extension headers must be processed strictly in the order they appear in the packet; a receiver must not, for example, scan through a packet looking for a particular kind of extension header and process that header prior to processing all preceding ones.

slide29

Chapter 4 Internet Protocol- IPv6

IP Extension Headers

The exception referred to in the preceding paragraph is the Hop-by-Hop Options header, which carries information that must be examined and processed by every node along a packet's delivery path, including the source and destination nodes. The Hop-by-Hop Options header, when present, must immediately follow the IPv6 header. Its presence is indicated by the value zero in the Next Header field of the IPv6 header.

slide30

Chapter 4 Internet Protocol- IPv6

IP Extension Headers

If, as a result of processing a header, a node is required to proceed to the next header but the Next Header value in the current header is unrecognized by the node, it should discard the packet and send an ICMP Parameter Problem message to the source of the packet, with an ICMP Code value of 1 ("unrecognized Next Header type encountered") and the ICMP Pointer field containing the offset of the unrecognized value within the original packet. The same action should be taken if a node encounters a Next Header value of zero in any header other than an IPv6 header.

slide31

Chapter 4 Internet Protocol- IPv6

IP Extension Headers

Each extension header is an integer multiple of 8 octets long, in

order to retain 8-octet alignment for subsequent headers. Multi-

octet fields within each extension header are aligned on their

natural boundaries, i.e., fields of width n octets are placed at an

integer multiple of n octets from the start of the header, for n = 1,

2, 4, or 8.

slide32

Chapter 4 Internet Protocol- IPv6

Header Order

A full implementation of IPv6 includes implementation of the

following extension headers:

Hop-by-Hop Options

Routing (Type 0)

Fragment

Destination Options

Authentication

Encapsulating Security Payload

slide33

Chapter 4 Internet Protocol- IPv6

IP Extension Headers

When more than one extension header is used in the same packet, it is recommended that those headers appear in the following order: (Destination Options Header may appear twice)

IPv6 header

Hop-by-Hop Options header

Destination Options header (for intermediate nodes)

Routing header

Fragment header

Authentication header

Encapsulating Security Payload header

Destination Options header (by final destination only)

upper-layer header

slide34

Chapter 4 Internet Protocol- IPv6

IP Extension Headers

Each extension header should occur at most once, except for the

Destination Options header which should occur at most twice (once before a Routing header and once before the upper-layer header).

If the upper-layer header is another IPv6 header (in the case of IPv6 being tunneled over or encapsulated in IPv6), it may be followed by its own extension headers, which are separately subject to the same ordering recommendations.

slide35

Chapter 4 Internet Protocol- IPv6

Options

Two of the currently-defined extension headers -- the Hop-by-Hop Options header and the Destination Options header -- carry a variable number of type-length-value (TLV) encoded "options", of the following format:

+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+- - - - - - - - -

| Option Type | Opt Data Len | Option Data

+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+- - - - - - - - -

Option Type 8-bit identifier of the type of option.

Opt Data Len 8-bit unsigned integer. Length of the

Option Data field of this option, in octets.

Option Data Variable-length field. Option-Type-specific

data.

slide36

Chapter 4 Internet Protocol- IPv6

Hop-by-Hop Options

The hop-by-hop options header contains IP options for every system on the datagram’s route. Every router in the path must examine and process the hop-by-hop options header.

Including type and length (2 bytes)

… (options)

Type

Length

# of bytes

194 Jumbo Payload Length 2_4 bytes 4n+2

slide37

Chapter 4 Internet Protocol- IPv6

Hop-by-Hop Options

Alignment: xn+y states that the option type must begin at an integer number of x bytes from the start of the header, plus y bytes.

For efficient processing of IP datagrams by a processor

slide38

Chapter 4 Internet Protocol- IPv6

Hop-by-Hop Options

The value of option type also tells routers how to handle the option when they encounter it. In particular, the two most significant bits tell a router what to do with an option type that it does not recognize.

slide39

Chapter 4 Internet Protocol- IPv6

Hop-by-Hop Options

The third most significant bit identifies those options that may change their value as the datagram traverses the network.

slide40

Chapter 4 Internet Protocol- IPv6

Hop-by-Hop Options

Pad1 Option

This option serves to shift other options’ positions in the header. Most frequently, it places those other options so that they satisfy their alignment requirements.

If a field fails to fall in the right place, one or more Pad1 options can be inserted ahead of it to shift the field to the correct position.

slide41

Chapter 4 Internet Protocol- IPv6

Hop-by-Hop Options

PadN Option

The PadN option serves the same purpose as the Pad1 option. However, the PadN option adds an arbitrary shift. The smallest shift possible is two bytes, corresponding to an option length of zero.

This one adds five bytes of padding.

slide42

Chapter 4 Internet Protocol- IPv6

Routing Header (Source Route Option)

Normally, the source of an IP datagram leaves it to the network to deliver that datagram to its destination. Sometimes, though, the source desires more control over the datagram’s route.

The source may wish to give the network hints as to the best path for the datagram, or it may wish to control the path to make sure the datagram does not travel through inappropriate routers.

The routing header gives the source this control.

slide43

Chapter 4 Internet Protocol- IPv6

Routing Header

Want to avoid this path sometimes

slide44

Chapter 4 Internet Protocol- IPv6

Routing Header

The Type 0 Routing header has the following format:

+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

| Next Header | Hdr Ext Len | Routing Type=0| Segments Left |

+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

| Reserved | Strict/Loose Bit Mask |

+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

| |

+ +

| |

+ Address[1] +

| |

+ +

| |

+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

slide45

Chapter 4 Internet Protocol- IPv6

Routing Header

When the datagram first leaves the source host, the basic IP header’s destination address indicates the first hop on the desired path. The list in the routing header identifies subsequent hops along that path.

As the datagram arrives at each hop, that system takes the next hop from the list and swaps it with the destination address.

EX: Fig. 4.15

slide46

Chapter 4 Internet Protocol- IPv6

Routing Header

Multicast addresses must not appear in a Routing header of Type 0

A Routing header is not examined or processed until it reaches the node identified in the Destination Address field of the IPv6 header. In that node, dispatching on the Next Header field of the immediately preceding header causes the Routing header module to be invoked.

slide47

Chapter 4 Internet Protocol- IPv6

Routing Header

As an example, consider the case of a source node S sending a packet to destination node D, using a Routing header to cause the packet to be routed via intermediate nodes I1, I2, and I3. The values of the relevant IPv6 header and Routing header fields on each segment of the delivery path would be as follows:

As the packet travels from S to I1:

Source Address = S Hdr Ext Len = 6

Destination Address = I1 Segments Left = 3

Address[1] = I2

Address[2] = I3

Address[3] = D

slide48

Chapter 4 Internet Protocol- IPv6

Routing Header

As the packet travels from I1 to I2:

Source Address = S Hdr Ext Len = 6

Destination Address = I2 Segments Left = 2

Address[1] = I1

Address[2] = I3

Address[3] = D

slide49

Chapter 4 Internet Protocol- IPv6

Routing Header

As the packet travels from I2 to I3:

Source Address = S Hdr Ext Len = 6

Destination Address = I3 Segments Left = 1

Address[1] = I1

Address[2] = I2

Address[3] = D

slide50

Chapter 4 Internet Protocol- IPv6

Routing Header

As the packet travels from I3 to D:

Source Address = S Hdr Ext Len = 6

Destination Address = D Segments Left = 0

Address[1] = I1

Address[2] = I2

Address[3] = I3

slide51

Chapter 4 Internet Protocol- IPv6

Routing Header

If, after processing a Routing header of a received packet, an

intermediate node determines that the packet is to be forwarded onto a link whose link MTU is less than the size of the packet, the node must discard the packet and send an ICMP Packet Too Big message to the packet's Source Address.

slide52

Chapter 4 Internet Protocol- IPv6

Fragment Header

The fragment header lets a host divide a large datagram into several smaller pieces and send those pieces through the network. The receiving host puts them back together.

8

8

13

2

Fragment Offset is a unit of 8 bytes  IP must break all fragment (except the last) into pieces whose size is an integer multiple of 8 bytes

slide53

Chapter 4 Internet Protocol- IPv6

Fragment Header

To be transmitted by Ethernet

2902 bytes of data

slide54

Chapter 4 Internet Protocol- IPv6

Fragment Header

4 bytes

First fragment:

4 bytes

16 bytes

1500-48=1452

8*181=1448

48

bytes

16 bytes

8 (fragment header length)

+1448=1456

4 bytes

4 bytes

1448 bytes

slide55

Chapter 4 Internet Protocol- IPv6

Fragment Header

Second fragment:

1448 bytes

slide56

Chapter 4 Internet Protocol- IPv6

Fragment Header

Third fragment:

6 bytes

slide57

Chapter 4 Internet Protocol- IPv6

Fragment Header (Reassembly)

If insufficient fragments are received to complete reassembly of a packet within 60 seconds of the reception of the first-arriving

fragment of that packet, reassembly of that packet must be

abandoned and all the fragments that have been received for that

packet must be discarded. If the first fragment (i.e., the one

with a Fragment Offset of zero) has been received, an ICMP Time Exceeded -- Fragment Reassembly Time Exceeded message should be sent to the source of that fragment.

slide58

Chapter 4 Internet Protocol- IPv6

Fragment Header

If the length of a fragment, as derived from the fragment packet's

Payload Length field, is not a multiple of 8 octets and the M flag of that fragment is 1 (must be multiple of 8 if not the last fragment), then that fragment must be discarded and an

ICMP Parameter Problem, Code 0, message should be sent to the

source of the fragment, pointing to the Payload Length field of

the fragment packet.

slide59

Chapter 4 Internet Protocol- IPv6

Fragment Header

If the length and offset of a fragment are such that the Payload

Length of the packet reassembled from that fragment would exceed 65,535 octets, then that fragment must be discarded and an ICMP Parameter Problem, Code 0, message should be sent to the source of the fragment, pointing to the Fragment Offset field of the fragment packet.

slide60

Chapter 4 Internet Protocol- IPv6

Destination Header

The destination options header contains IP options for the datagram’s destination. If the datagram includes a routing header, the header can also precede that header. In that case, its options will be processed by each intermediate hop included in the routing header’s list.

So far, only two options have been defined for the destination options header, Pad1 and PadN.

slide61

Chapter 4 Internet Protocol- IPv6

Transition Mechanism

The key to a successful IPv6 transition is compatibility with the large installed base of IPv4 hosts and routers. Maintaining compatibility with IPv4 while deploying IPv6 will streamline the task of transitioning the Internet to IPv6.

slide62

Chapter 4 Internet Protocol- IPv6

Transition Mechanism

Two mechanisms:

  • Dual IP layer. Providing complete support for both IPv4 and
  • IPv6 in hosts and routers.
  • IPv6 over IPv4 tunneling. Encapsulating IPv6 packets within
  • IPv4 headers to carry them over IPv4 routing infrastructures.
slide63

Chapter 4 Internet Protocol- IPv6

Transition Mechanism

Type of Nodes:

IPv4-only node:

A host or router that implements only IPv4. An

IPv4-only node does not understand IPv6. The installed

base of IPv4 hosts and routers existing before the

transition begins are IPv4-only nodes.

slide64

Chapter 4 Internet Protocol- IPv6

Transition Mechanism

Type of Nodes:

IPv6/IPv4 node:

A host or router that implements both IPv4 and IPv6.

IPv6-only node:

A host or router that implements IPv6, and does not

implement IPv4.

slide65

Chapter 4 Internet Protocol- IPv6

Transition Mechanism

IPv6-over-IPv4 Tunneling

In most deployment scenarios, the IPv6 routing infrastructure

will be built up over time. While the IPv6 infrastructure is

being deployed, the existing IPv4 routing infrastructure can

remain functional, and can be used to carry IPv6 traffic.

Tunneling provides a way to utilize an existing IPv4 routing

infrastructure to carry IPv6 traffic.

slide66

Chapter 4 Internet Protocol- IPv6

Transition Mechanism

IPv6-over-IPv4 Tunneling

The entry node of the tunnel (the encapsulating node) creates an

encapsulating IPv4 header and transmits the encapsulated packet.

The exit node of the tunnel (the decapsulating node) receives

the encapsulated packet, removes the IPv4 header, updates the

IPv6 header, and processes the received IPv6 packet.

slide67

Chapter 4 Internet Protocol- IPv6

Transition Mechanism

IPv6-over-IPv4 Tunneling

Entry

Router

IPv4

Infrastructure

Leaving

Router

IPv4

header

Protocol

number=41

IPv6

packet

IPv6

packet

IPv6

packet

slide68

Chapter 4 Internet Protocol- IPv6

Transition Mechanism

IPv6-over-IPv4 Tunneling

IPv6-over-IPv4 tunnels are modeled as "single-hop".

That is, the IPv6 hop limit is decremented by 1 when

an IPv6 packet traverses the tunnel. The single-hop

model serves to hide the existence of a tunnel.

The tunnel is opaque to users of the network, and is not

detectable by network diagnostic tools such as traceroute.

slide69

Chapter 4 Internet Protocol- IPv6

Conclusions

A new Internet Protocol, IPv6, has been defined to support

the new requirements in security, routing flexibility, traffic

support, and extended addressing capability.

The most important thing in the design is a smooth transition

plan because IPv4 and IPv6 may coexist for several decades

to come.

slide70

Chapter 4 Internet Protocol- IPv6

Conclusions

Other protocols also need to be modified to adapt to IPv6,

for example, routing protocols, Domain Name System,

Internet Control Message Protocol, etc.

To keep up to date on the latest development, visit the

IPng working group at:

http://playground.sun.com/ipng/

And the IPv6 Forum at www.ipv6forum.com