IPv6Varsha RameshKumar,S6 CSE

IPv6

• Initial motivation: 32-bit address space soon to be completely allocated. – Increase IP address from 32 bits to 128

• Additional motivation:• header format helps speed processing

– Longer header but fewer fields (8 vs 12), so routers should have less processing

• header changes to facilitate QoS– Accommodate higher network speeds, mix of data streams

(graphics, video, audio)

• IPv6 datagram format: – fixed-length 40 byte header– no fragmentation allowed

Advantages

• Overcome IPv4 scaling problem – lack of address space.

• Flexible transition mechanism.• New routing capabilities.• Quality of service.• Security.• Ability to add features in the future.

IPv6 Background

• IP has been patched (subnets, supernets) but there is still the fundamental 32 bit address limitation

• IETF started effort to specify new version of IP in 1991– New version would require change of header– Include all modifications in one new protocol– Solicitation of suggestions from community– Result was IPng which became IPv6– First version completed in ’94

• Same architectural principles as v4 – only bigger

Features of IPv6

• Larger Address Space• Aggregation-based address hierarchy

– Efficient backbone routing• Efficient and Extensible IP datagram• Stateless Address Autoconfiguration• Security (IPsec mandatory)• Mobility• IPv6 can address 3.4×1038 nodes

IPv6 Packet header

7

IPv6 Header Fields

• VERS: 6 (IP version number)• Priority: will be used in congestion control• Flow Label: experimental - sender can

label a sequence of packets as being in the same flow.

• Payload Length: number of bytes in everything following the 40 byte header, or 0 for a Jumbogram.

8

IPv6 Header Fields

• Next Header is similar to the IPv4 “protocol” field - indicates what type of header follows the IPv6 header.

• Hop Limit is similar to the IPv4 TTL field (but now it really means hops, not time).

Address Space Allocation

• IPv6 addresses are also classless, but the

address space is still subdivided in various ways based on the leading bits.• The leading bits specify different uses of

the IPv6 address.

• A node may be assigned an IPv4-compatible IPv6 address by zero-extending a 32-bit IPv4 address to 128 bits.

• A node that is only capable of understanding IPv4 can be assigned an IPv4-mapped IPv6 address by prefixing the 32-bit IPv4 address with 2 bytes of all 1s and then zero-extending the result to 128 bits.

• These two special address types have uses in the IPv4-to-IPv6 transition

128-bit IPv6 Address3FFE:085B:1F1F:0000:0000:0000:00A9:1234

8 groups of 16-bit hexadecimal numbers separated by “:”

3FFE:85B:1F1F::A9:1234

:: = all zeros in one or more group of 16-bit hexadecimal numbers

Leading zeros can be removed

For example,The IPv4-mapped IPv6 address of a host whose IPv4 address was 128.96.33.81could be written as::FFFF:128.96.33.81

Global Unicast Addresses

• at the heart of IPv6 is the unicast address allocation plan that determines how unicast addresses will be assigned to

• service providers, • autonomous systems, • networks, • hosts, and • routers.

Network Layer 15

Address Complexity

• IPv6 actually has many kinds of addresses

– unicast, anycast, multicast, – link-local, site-local, loopback, IPv4-

embedded, care-of, manually-assigned, DHCP-assigned, self-assigned, solicited-node, and more…

• most of this complexity is also present in IPv4,just never written down in one place

– a result of 20 years of protocol evolution• one simplification: no broadcast addresses in IPv6!

– uses multicast to achieve same effects

Network Layer 16

IPv6 Addressing

• Classless addressing/routing (similar to CIDR)• Notation: x:x:x:x:x:x:x:x (x = 16-bit hex number)

– contiguous 0s are compressed: 47CD::A456:0124– IPv6 compatible IPv4 address: ::128.42.1.87

• Address assignment– provider-based (can’t change provider easily)– geographic

001 Registry ID Provider ID Subscriber ID Subnet ID Interface ID

n bits m bits o bits p bits (125-m-n-o-p) bits

40bytes

20bytes

IPv4

IPv6

0 15 16 31

vers hlen TOS total length

identification flags flag-offset

TTL protocol header checksum

source address

destination address

options and padding

vers traffic class flow-label

payload length next header hop limit

source address

destination address

Removed (6)• ID, flags, flag offset• TOS, hlen• header checksum

Changed (3)

Added (2)

Expanded

• total length => payload• protocol => next header• TTL => hop limit

• traffic class• flow label

• address 32 to 128 bits

Header comparison

Major Improvements of IPv6 Header

• No option field: Replaced by extension header. Result in a fixed length, 40-byte IP header.

• No header checksum: Result in fast processing.

• No fragmentation at intermediate nodes: Result in fast IP forwarding.

Extension Headers

• Routing – Extended routing, like IPv4 loose list of routers to visit

• Fragmentation – Fragmentation and reassembly

• Authentication – Integrity and authentication, security

• Encapsulation – Confidentiality• Hop-by-Hop Option – Special options that

require hop-by-hop processing• Destination Options – Optional information to

be examined by the destination node

Extension Header

THANK YOU!