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Wolfgang Effelsberg University of Mannheim 1
IP Version 6The Next-Generation IP Protocol
Wolfgang EffelsbergUniversity of Mannheim
September 2001
Wolfgang Effelsberg University of Mannheim 2
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
Wolfgang Effelsberg University of Mannheim 3
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
Wolfgang Effelsberg University of Mannheim 4
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
. . .
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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
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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
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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
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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
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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“
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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
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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
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IPv6 Header
Payload Length Next Header Hop LimitClassVers. Flow Label
Source Address
Destination Address
IPv6: 40 Bytes in 8 fields
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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
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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.
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Examples for Extension Headers
IPv6-Headernext header =
TCP
IPv6-Headernext header =
Routing
IPv6-Headernext header =
Routing
Routing-Headernext header =
TCP
Routing-Headernext header =
Fragment
Fragment-Header, next header = TCP
TCP-Header+ data
TCP-Header+ data
TCP-Header+ data
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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
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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
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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
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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.
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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)