Wolfgang EffelsbergUniversity of Mannheim1 IP Version 6 The Next-Generation IP Protocol Wolfgang Effelsberg University of Mannheim September 2001

Wolfgang Effelsberg University of Mannheim 1

IP Version 6The Next-Generation IP Protocol

Wolfgang EffelsbergUniversity of Mannheim

September 2001


Outline

1. Remember IP Version 4?

2. IP Version 6 Fundamentals

3. IPv6 Header Format and Protocol Functions

4. Transition from Version 4 to Version 6


1. Remember IP Version 4?

IP (Internet Protocol) – Layer 3 of the Internet

A datagram protocol (connectionless)

A host-to-host protocol

Handles the fragmentation of large packets

Does not do much else! No error control, no packet sequencing, no flow control, no congestion control


Format of IPv4 Datagrams (1)

0 4 8 1 6 1 9 2 4 3 1

V E R S L E N T Y P E O F S E R V I C E T O T A L L E N G T H

I D E N T F L A G S F R A G M E N T O F F S E T

T I M E P R O T O H E A D E R C H E C K S U M

S O U R C E I P A D D R E S S

D E S T I N A T I O N I P A D D R E S S

O P T I O N S P A D D I N G

D A T A

. . .


Format of IPv4 Datagrams (2)

VERS Protocol version

LEN Header length (in words)

TYPE OF SERVICE Something like priority

TOTAL LENGTH Length of the packet, including the data

IDENT Identity of the datagram

FLAGS Do not fragment / last fragment

FRAGMENT OFFSET Offset of this fragment

TIME Time to live

PROTO Type of the higher-level protocol carried

HEADER CHECKSUM EXOR of the header words

SOURCE ADDRESS IP address of the source host

DEST ADDRESS IP address of the destination host

OPTIONS Command code for network management packets

PADDING Fill up the packet to next word boundary

DATA User data field


Addressing in IPv4

The IP address is hierachical, with the two fields netid and hostid. There is also a format for multicast (class D)

For reasons hard to understand, four decimal numbers are used to describe an IP address:

10.0.0.0 for Arpanet

128.10.0.0 for a large Ethernet-LAN

192.5.48.0 for a small LAN

Class A

Class B

Class C

0

1

1 1

0

Netid

Netid

Netid

Hostid

Hostid

Hostid

0

0

1 1 1 0

1 8 16 24 31

Class D


2. IP Version 6: Fundamentals

MotivationIPv4 networks running out of addresses

No more Class B addresses available Hierarchical addressing wastes large chunks of the address

space CIDR (classless inter-domain routing) helpful but not a long-

term solutionRouting tables grow very large

More hierarchical levels desirableFix bugs in the IPv4 design

After many years of experience design flaws of IPv4 should be removed


History of IPv6

1992: IETF publishes the Call for Proposals for „IP next generation“ (Ipng)

1994: SIPP (Simple Internet Protocol Plus) proposed by some researchers to the IETF

1995: Internet Draft „Internet Protocol, Version 6 (IPv6)“ becomes a Proposed Standard“ (9/95) and then an RFC1883 (12/95). Early prototypes implemented.

1996: IP Version 6 Backbone (6Bone) between some research labs, early products in the market

1998: RFC 2460, Draft Standard

2001: Widely implemented, but not very widely used because of considerable transition overhead for ISPs


Properties of IPv6 (1)

New addresses

Address size 128 bits (one address for each bit in the universe!)

A deeper addressing hierarchy (Top Level Aggregator = address registration authority, Next Level Aggregator = large ISP, etc.). Leeds to smaller routing tables

Automatic address configuration integrated into IPDesign bugs fixed

Fragmentation no longer supported. Replaced by „MTU discovery“ (maximum transfer unit) (!)

Header checksum removed (!) All headers have a fixed size. Extension headers replace

header options. Hop limit replaces „time to live“


Properties of IPv6 (2)

Better support for Quality-of-Service

Flow Labels allow the marking of all packets belonging to the same flow at the IP level

Traffic Class for Differentiated ServicesFull integration of IP multicast

Predefined multicast group addresses for special multicast functions IGMP (Internet Group Management Protocol) fully integrated into

ICMP (Internet Control Message Protocol) All routers and end systems implement multicast IP. Tunnels will no

longer be required. Anycast also supported. Usage still a research issue.

IP Security

Authentication and encryption are available at the IP layer


Version Total LengthHdr LenPrece-dence ToS

Fragment OffsetIdentification Flags

Header ChecksumProtocolTime To Live

Source Address

Destination Address

3. IPv6 Header Format and Protocol Functions

Red: removed

Green: Moved to the extension header

Yellow: renamed precedence class total length payload length time to live hop limit protocol next header

IPv4: 20 Bytes in 13 fields


IPv6 Header

Payload Length Next Header Hop LimitClassVers. Flow Label

Source Address

Destination Address

IPv6: 40 Bytes in 8 fields


Aggregatable Global Unicast Address

The most important of many possible IPv6 address formats

Top Level Aggregation (TLA)

Internet Naming Authority or very large ISPs with transit networks to which other ISPs are

Next Level Aggregation (NLA)

Organisation on a lower level of the hierarchy Multiple NLA levels possible

Site Level Aggregation (SLA)

A single organisation, such as a large company

001 TLA ID NLA ID SLA IDInterface ID

3 13 24 16Public topology Site topology

res.8


Extension Headers

Concatenation of extension headers

A small minimal header of fixed size, easy to process in routers Flexible extensions for special purposes (such as source routing) Eases the introduction of future extensions

Last header in the chain specifies the type of the content encapsulated in IP (e.g., TCP, UDP).

Thus the PROTOCOL TYPE field of IPv4 is no longer needed.


Examples for Extension Headers

IPv6-Headernext header =

TCP


Routing


Routing

Routing-Headernext header =

TCP

Routing-Headernext header =

Fragment

Fragment-Header, next header = TCP

TCP-Header+ data

TCP-Header+ data

TCP-Header+ data


Stateless Automatic Address Configuration

The router broadcasts parameters periodically to the multicast group of all hosts (router advertisement).

Each host sends a router solicitation to the multicast group of all routers, a direct answer of the router follows.

3A01:203:405:1::1FE80::C:D:13A01:203:405:1::C:D:1

3A01:203:405:1::/64,3A01:203:405:1::1


4. Transition from Version 4 to Version 6

Duplicate protocol stacks UDP/IPv4 and UDP/IPv6 TCP/IPv4 and TCP/IPv6

All IPv6 systems must also have an IPv4 protocol stack during the transition phase.

application

socket interface

UDP for IPv4

layer 2 link

TCP for IPv4 UDP for IPv6 TCP for IPv6

IPv6


IPv4-Compatible Address

Allows IPv6 implementations to work with old v4 addresses

Can be used by IPv6 systems to communicate with other IPv6 systems by TUNNELS

IPv4 address0 ... 0

0 ... 0


Tunneling

IPv4-Router

hand-configurated tunnel(HostRouter or RouterRouter)

Automatically config. tunnel (Router Host, Host Host)

Tunneling means the encapsulation of an IP packet into another IP packet which will have a new, different IP destination address. At the end of the tunnel the inner IP packet is removed from the „envelope“. In this way an IP packet can be transmitted over pieces of the network which it could otherwise not cross.


References

C. Huitema: IPv6 - The New Internet Protocol, second edition, Prentice Hall, 1998

W. Stallings: IPv6: The New Internet Protocol, IEEE Communications, Vol. 34, No. 7, S. 96-108

R. Fink: IPv6 - What and Where it is, Cisco Internet Protocol Journal, März 1999

W. Stallings: IP Security, Cisco Internet Protocol Journal, März 2000

T. Braun: Internet Protocols for Multimedia Communications, Part I, IEEE Multimedia, Vol. 31, No. 9, S. 85-90

T. Braun: IPng: Neue Internet-Dienste und Virtuelle Netze, dpunkt 1999 (in German)

Documents

Wolfgang EffelsbergUniversity of Mannheim1 IP Version 6 The Next-Generation IP Protocol Wolfgang Effelsberg University of Mannheim September 2001