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IP Futures

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Title: IP Futures


1
IP Futures
  • There are problems with IP which are a result of
    the phenomenal growth of the Internet over the
    past few years
  • as of 1994, over half of the class B addresses
    have been allocated
  • 32-bit IP addresses are inadequate
  • the current routing structure is basically flat,
    making routing tables too large
  • Scalability is the problem!!

2
Classless Addressing
  • The IP addressing space has been running out
  • Subnet addressing (early 1980s) helped to
    conserve the IP address space
  • Unnumbered networks and transparent routers
    followed
  • In 1993 work began on developing a new version of
    IP
  • In the meantime something needs to be done
  • Classless addressing, supernet addressing, or
    supernetting is the technique currently being used

3
The Basic Idea
  • Classless addressing take a complementary
    approach to subnet addressing
  • Instead of a single IP network prefix for an
    organization, addresses assigned to a single
    organization are allowed to span multiple classed
    prefixes

4
Why?
  • The IP addressing scheme does not divide network
    addresses evenly
  • 17,000 class B addresses and 2 million class C
    address
  • The Goldilocks problem caused most organization
    to request class B addresses

5
PTT Inc.
  • PTT Inc needs to register to get an IP address
  • Class C is clearly too small, plus I want to
    subnet, so I want a class B
  • Instead of a single class B address, I get a
    contiguous block of class C addresses

6
ISPs
  • Classless addressing was also meant to be used in
    a broader context
  • The ISP assigns numbers to its clients

7
Routing
  • Clearly classless addressing affects the way that
    routing is done
  • At first glance it appears that routing tables
    will need to grow
  • CIDR takes care of this
  • RFC 1519
  • Contiguous class C addresses are represented by a
    single entry
  • ( network address, count)

8
Routing Tables
  • So the entry
  • ( 192.5.48.0, 3 )
  • Specifies the network addresses 192.5.48.0,
    192.5.49.0, and 192.5.50.0
  • If ISPs make up the core of the internet
  • Routing tables become much smaller
  • An ISPs routing table has entries for all of its
    customers, but only one entry for any other ISP

9
Class C Allocation Rules
Start End Location
194.0.0.0 195.255.255.255 Europe
198.0.0.0 199.255.255.255 North America
200.0.0.0 201.255.255.255 Central and South America
202.0.0.0 203.255.255.255 Asia and the Pacific
10
CIDR In Practice
  • CIDR uses a bit mask to identify the size of the
    block
  • For a block of 2048 addresses starting at
    128.211.168.0
  • The mask would be FF FF F8 00
  • New shorthand
  • 128.211.168.0/21
  • 255.0.0.0/8
  • 255.255.0.0/16
  • 255.255.255.0/24

11
New IP Versions
  • Four proposals have been made for a new version
    of IP
  • SIP, the Simple Internet Protocol. Proposes a
    minimal set of changes to IP that uses 64-bit
    addresses and a different header format
  • PIP, larger, variable length, hierarchical
    addresses with a different header format
  • TUBA (RFC1347), TCP and UDP with bigger addresses
  • TP/IX (RFC1475), 64-bit addresses, changes TCP/UDP

12
References
  • The May 1993 issue of IEEE Network (volume 7,
    number 3) contains overviews of the first three
    proposals, along with an article on CIDR.
  • RFC1454 also compares the first three proposals

13
What is IPv6?
  • IPv6, also called IPng (next generation) is the
    new version of Internet Protocol
  • Currently we are using IPv4, which IPv6 was
    designed to be a successor to
  • Designed not to take a radical step away from
    IPv4, but improve upon it

14
Why IPv6?
  • IPv4 has been designed early in the 70s
  • Many things have been added
  • MobileIP
  • QoS
  • Security (IPsec)
  • Others
  • These were not designed in IPv4 from the start.

15
Design Criteria
  • Number of addresses
  • Efficiency in routers low and very high bandwidth
    (100G/ bytes)
  • Security
  • Mobility
  • Automatic configuration
  • Seamless transition
  • No need to change hardware

16
Features
  • Expanded addressing capabilities
  • Header format simplification
  • Increased support for modular options
  • Multicast routing capabilities
  • Security capabilities
  • Expanded QoS capabilities

17
Address Space
  • IPv4
  • 32 bit addresses
  • addresses assigned to nodes
  • little unassigned address space
  • relatively small address space
  • IPv6
  • 128 bit addresses
  • addresses assigned to interfaces
  • approximately 82 of address space unassigned
  • huge address space

18
How Huge?
  • Every human on the planet has enough addresses to
    create a network the size of the current internet
  • Or
  • Earths surface is about 5.1 x 108 square
    kilometers
  • This means there are about 1024 addresses per
    square meter of the Earths surface
  • Or
  • If you assign addresses at the rate of one
    million every microsecond, it would take more
    than 1020 years to exhaust the addressing space.

19
Or
  • Imagine Bill Gates fortune is 85 billion
    (8.5x1010) Take 1 trillion Bill Gateses
  • Convert their fortune to pennies
  • Assign 1x1012 addresses to each penny
  • Takes 8.5x1036 addresses
  • Youve just assigned 2.5 of the entire IPv6
    address space

20
Address Notation
  • 128 bit address are too big to write in the
    dotted-decimal-octet format (i.e. 129.21.3.103)
  • New notation is hexadecimal digits separated by
    colons every 16 bits.
  • 5f1bdf00ce3ee200002008002078e3e3
  • Can append decimal octet for easier IPv4
    mapping/compatibility
  • FFFF206.62.226.33
  • Can abbreviate filler 0 bits with

21
IPv6 Address Types
  • Three types of addresses
  • Unicast
  • Destination is a single computer
  • Multicast
  • The destination is a set of computers, the
    datagram is delivered to each member of the group
  • Anycast

22
Anycast
  • An anycast address is one that is assigned to
    more than one interface (typically belonging to
    different nodes)"
  • A packet sent to an anycast address is routed to
    the "nearest" interface having that address,
    according to the routing protocol
  • Allocated from the unicast address space
  • Not to be used as the source address
  • Assigned to routers only - not hosts

23
Anycast Example
  • Your ISP has two upstream connections with two
    different service providers
  • Service provider X uses anycast address A to
    identify all of its routers
  • If you want your packets to go through X, you can
    do a source route to A
  • This will go to the "nearest" router in A, so
    even if the network topology changes, your
    packets will still go through X

24
Important Addresses
  • Localhost - 127.0.0.1 - 1
  • The unspecified address - 0.0.0.0 - or 00
  • Multicast
  • all nodes on link ff021
  • all routers on link ff022
  • all hosts on link ff023

25
Format of Global Unicast Address
  • Format prefix (001)
  • TLA ID (top-level aggregation identifier)
  • NLA ID (next-level aggregation identifier)
  • SLA ID (site-level agg. id. - e.g. Subnet ID)
  • interface identifier - based on MAC address

26
Format of Multicast Addresses
  • Flags is a set of 4 flags.
  • The high order 3 flags are reserved.
  • The low order flag indicates whether the address
    is a permanently assigned or transient multicast
    address.
  • Scope indicates multicast scope e.g.
  • 1 node-local
  • 2 link-local
  • 5 site-local

27
IPv6 Packet Format
Optional
Base Header
Ext Header 1
Ext Header N

DATA!!
40 Octets
28
IPv6 Packet Header
Vers
Traffic Type
Flow Label
Payload Length
Next Header
Hop Limit
Source Address
Destination Address
29
IPv6 Packet Header
  • Followed by optional header extensions and data
    payload
  • Addresses are 64-bit aligned - for speed
  • Note the lack of a header checksum
  • For speed

30
Traffic Class
  • 8-bit field
  • A way to identify and distinguish between
    different classes or priorities of packets
  • Used to make more intelligent routing decisions
  • Can be set or changed by forwarding routers
  • Currently experimental

31
Flow Label
  • 20-bit field
  • A flow is a sequence of packets
  • Distinguished by
  • Source
  • Destination
  • Flow Number
  • Used by a source to request special handling by
    routers for all packets in a flow

32
Payload Length
  • 16-bit unsigned integer
  • Length of the rest of the packet in bytes
  • Includes header extensions and data block

33
Next Header
  • 8-bit selector
  • For header extensions
  • If header extensions are present, this field
    indicates the type of the first one following the
    current header

34
Hop Limit
  • Limit on the number of times a packet can be
    forwarded on the network
  • Set by source
  • Decremented by routers when packet is forwarded
  • If zero after decrement, packet is dropped,
    ICMPv6 Echo Timeout sent to source
  • Analagous to TTL in IPv4

35
Extension Headers
  • Hop-by-Hop options
  • Source Routing
  • Fragmentation
  • Authentication
  • Encapsulating Security Payload
  • Destination options
  • Upper-layer headers
  • Optional Components
  • Used to provide more information to routers or
    destination
  • Seven types of extensions defined

36
Options Headers
  • Two types
  • Hop-by-hop examined by every router
  • Destination examined by the receiving node only
  • Contains further information to be known to the
    appropriate machines.
  • Format specified, but options themselves
    currently unspecified (as far as I can tell)

37
Fragmentation
  • Fragmentation is an option header as it is the
    exception, not the rule
  • Unlike IPv4, fragmentation must happen at the
    source, not at intermediate routers - for speed
  • This means source must have the ability to
    perform Path MTU Discovery
  • IPv6 requires that every link on the internet
    have an MTU of 1280 bytes or greater

38
Upper-Layer Checksums
  • The transport layer in IPv6 places a
    pseudo-header into the header extensions.
  • This includes source and (ultimate) destination
    addresses.
  • Upper-layer checksums must include this
    pseudo-header in their calculation so the
    destination can validate these fields.
  • TCP, UDP and ICMPv6 all use these pseudo-headers

39
Transition
  • Allows for incremental updates
  • e.,g. one subnet can upgrade at a time
  • Easy addressing for IPv4 compatibility/mapping
  • Encapsulation of packets
  • IPv6 in IPv4 (i.e. 6Bone)
  • IPv4 in IPv6
  • Can have both IPv4 and IPv6 on same network
  • Will take years to complete

40
IPv4 Compatibility
  • Transition Mechanism includes a technique for
    dynamically tunneling IPv6 over IPv4
    infrastructure.
  • IPv6 nodes that utilize this technique are
    assigned special IPv6 unicast addresses that
    carry an IPv4 address in the low-order 32 bits.
  • This is an "IPv4-Compatible IPv6 address"
  • ltIPv4 addressgt
  • e.g. 129.12.3.103

41
IPv4 Mapping
  • Used to represent the address of IPv4-only nodes
    (those that do not support IPv6) as IPv6
    addresses
  • Called an "IPv4-mapped IPv6 address"
  • FFFFltIPv4 addressgt
  • e.g FFFF129.21.3.103

42
Routing
  • Nearly identical to IPv4 routing
  • Fixes class A/B/C routing problems
  • All of IPv4's routing algorithms will work with
    minor extensions
  • Some new functionality
  • Provider selection
  • Host mobility (route to current location)
  • Auto-readdressing (route to new address)

43
References
  • RFCs
  • 2460 Internet Protocol, Version 6 Specification
  • 2373 IPv6 Addressing Architecture
  • 1933 Transition Mechanisms for IPv6 Hosts and
    Routers
  • www.ipv6.org
  • www.6bone.net
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