IPv4 to IPv6 Network Address Translation

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IPv4 to IPv6 Network Address Translation
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Introduction

• What is the current internet addressing scheme
  and what limitations does it face.
• A new addressing scheme that would resolve the
  limitations, and an interim path towards the new
  scheme.

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What we will cover during this presentation

• IPv4 Address structure
• The IPv4 address resource problem
• Network Address translation of private address to
  global addresses for IPv4 address conservation.
• IPv6 Specifications (rfc1883)
• IPv6 addressing structure (rfc1884)
• IPv4 to IPv6 transition and NAT considerations
• IPv6 to IPv4 address translation at the edge
  router and higher layer consideration.
• Need for port number translations in IPv4 to IPv6
  NAT(rfc2766)

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IPv4 Address Scheme

• IP Packet Format
• An IP packet contains several types of
  information, as illustrated.

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• Version---Indicates the version of IP currently
  used.
• IP Header Length (IHL)---Indicates the datagram
  header length in 32-bit words.
• Type-of-Service---Assigns datagrams various
  levels of importance.
• Total Length---Specifies the length, in bytes, of
  the entire IP packet.
• Identification---Contains an integer that
  identifies the current datagram.
• Flags---The two low-order (least-significant)
  bits control fragmentation. The low-order bit
  specifies whether the packet can be fragmented.
  The middle bit specifies whether the packet is
  the last fragment in a series of fragmented
  packets. The third or high-order bit is not used.
  
• Fragment Offset---Indicates the position of the
  fragment's data relative to the beginning of the
  data in the original datagram.
• Time-to-Live---Maintains a counter that gradually
  decrements down to zero, at which point the
  datagram is discarded. This keeps packets from
  looping endlessly.
• Protocol---Indicates which upper-layer protocol
  receives incoming packets after IP processing is
  complete.
• Header Checksum---Helps ensure IP header
  integrity.
• Source Address---Specifies the sending node.
• Destination Address---Specifies the receiving
  node.
• Options---Allows IP to support various options,
  such as security.
• Data---Contains upper-layer information.

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• IPv4 Addressing
• As with any other network-layer protocol, the IP
  addressing scheme is integral to the process of
  routing IP datagrams through an internetwork.
  Each IP address has specific components and
  follows a basic format. These IP addresses can be
  subdivided and used to create addresses for
  subnetworks, as discussed in more detail later.
• Each host on a TCP/IP network is assigned a
  unique 32-bit logical address that is divided
  into two main parts the network number and the
  host number. The network number identifies a
  network and must be assigned by the Internet
  Network Information Center (InterNIC) if the
  network is to be part of the Internet. An
  Internet Service Provider (ISP) can obtain blocks
  of network addresses from the InterNIC and can
  itself assign address space as necessary. The
  host number identifies a host on a network and is
  assigned by the local network administrator.
• The 32-bit IP address is grouped eight bits at a
  time, separated by dots, and represented in
  decimal format (known as dotted decimal
  notation). Each bit in the octet has a binary
  weight (128, 64, 32, 16, 8, 4, 2, 1). The minimum
  value for an octet is 0, and the maximum value
  for an octet is 255.The figure below illustrates
  the basic format of an IP address.

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Private addresses to assign within a network(Not
globally routable)

• 172.16.0.0/255.255.0.0
• 192.168.0.0/255.255.255.0
• 10.0.0.0/255.0.0.0
• So in order to resolve the shortage of IPv4
  addresses so far the solution has been Network
  Address Translation as follows. With the
  following scheme a network can have almost
  infinite IP addresses yet never contribute to
  the finite globally routable IP addresses
  shortage.
• In its simplest configuration, the Network
  Address Translator (NAT) operates on a router
  connecting two networks together one of these
  networks (designated as inside) is addressed with
  either private or obsolete addresses that need to
  be converted into legal addresses before packets
  are forwarded onto the other network (designated
  as outside). The translation operates in
  conjunction with routing, so that NAT can simply
  be enabled on an Internet access router when
  translation is desired.
• Use of a NAT device provides RFC 1631-style
  network address translation on the router
  platform. The goal of NAT is to provide
  functionality as if the private network had
  globally unique addresses and the NAT device was
  not present.

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• Schema diagram

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• The above method is useful yet lacks a viable
  solution to globally routable IP address problem.
• Since for every private IP address a globally
  routable IP address is needed for direct
  translation. Well in most cases it is not very
  profitable or at all possible to contain many IP
  addresses.
• Dynamic Network address translation
• One way to resolve this issue would be through
  Port Address Translation (PAT) as follows

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• PAT (Port Address Translation)
• PAT does not work with H.323 applications,
  multimedia applications, and caching nameservers.
  
• PAT works with DNS, FTP and passive FTP, HTTP,
  mail, RPC, rshell, Telnet, URL filtering, and
  outbound traceroute.
• Finally when we have completely exhausted all
  available IPv4 resources we need to explore the
  new version of Ipng

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• NAT Enroute to translate
• Host-A NAT router
  Host-X
• ------ -----------
  ------
• ltOuter IP header, with
• srcAddr-A, DestAddr-Xgt,
• embedding
• ltEnd-to-end packet, with
• srcAddr-k, DestAddr-Xgt
• -----------------------------gt
• ltOuter IP header, with
• srcAddr-k, DestAddr-Xgt,
• embedding
• ltEnd-to-end packet, with
• srcAddr-k, DestAddr-Xgt
• --------------------------
  -gt

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• NAPT router enroute to translate
• Host-A NAPT router
  Host-X
• ------ -----------
  ------
• ltOuter TCP/UDP packet, with
• srcAddr-A, Src PortT-Na,
• DestAddr-Xgt,
• embedding
• ltEnd-to-end packet, with
• srcAddr-Nx, Src PortT-Nx, DestAddr-Xgt
• -----------------------------gt
• ltOuter TCP/UDP packet,
  with
• srcAddr-Nx, Src
  PortT-Nxa,
• DestAddr-Xgt,
• embedding

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• IPv6 Specification (rfc1883)
• IP version 6 (IPv6) is a new version of the
  Internet Protocol, designed as a successor to IP
  version 4 (IPv4) RFC-791. The changes from IPv4
  to IPv6 fall primarily into the following
  categories
• Expanded Addressing Capabilities IPv6 increases
  the IP address size from 32 bits to 128 bits, to
  support more levels of addressing hierarchy, a
  much greater number of addressable nodes, and
  simpler auto-configuration of addresses.
• The scalability of multicast routing is improved
  by adding a "scope" field to multicast addresses.
• And a new type of address called an "anycast
  address" is defined, used to send a packet to any
  one of a group of nodes.
• Header Format Simplification Some IPv4 header
  fields have been dropped or made optional, to
  reduce the common-case processing cost of packet
  handling and to limit the bandwidth cost of the
  IPv6 header.
• Improved Support for Extensions and Options
  Changes in the way IP header options are encoded
  allows for more efficient forwarding, less
  stringent limits on the length of options, and
  greater flexibility for introducing new options
  in the future.
• Flow Labeling Capability A new capability is
  added to enable the labeling of packets belonging
  to particular traffic "flows" for which the
  sender requests special handling, such as
  non-default quality of service or "real-time"
  service.
• Authentication and Privacy Capabilities
  Extensions to support authentication, data
  integrity, and (optional) data confidentiality
  are specified for IPv6.

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• IPv6 Addressing scheme overview
• IPv6 addresses are 128-bit identifiers for
  interfaces and sets of
• interfaces. There are three types of
  addresses
• Unicast An identifier for a single interface.
  A packet sent
• to a unicast address is delivered
  to the interface
• identified by that address.
• Anycast An identifier for a set of interfaces
  (typically
• belonging to different nodes).
  A packet sent to an
• anycast address is delivered to
  one of the interfaces
• identified by that address (the
  "nearest" one,
• according to the routing
  protocols' measure of
• distance).
• Multicast An identifier for a set of interfaces
  (typically
• belonging to different nodes).
  A packet sent to a

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• An example of a Unicast address format which will
  likely be common on
• LANs and other environments where IEEE 802 MAC
  addresses are
• available is
• n bits 80-n bits
  48 bits
• -------------------------------------------
  --------------------
• subscriber prefix subnet ID
  interface ID
• -------------------------------------------
  --------------------
• Where the 48-bit Interface ID is an IEEE-802
  MAC address. The use of
• IEEE 802 MAC addresses as a interface ID is
  expected to be very
• common in environments where nodes have an
  IEEE 802 MAC address. In

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• Traditional-NAT-PT Operation (V6 to V4)
• NAT-PT offers a straight forward solution
  based on transparent
• routing NAT-TERM and address/protocol
  translation, allowing a large
• number of applications in V6 and V4 realms to
  inter-operate without
• requiring any changes to these applications.
• In the following paragraphs we describe the
  operation of
• traditional-NAT-PT and the way that
  connections can be initiated from
• a host in IPv6 domain to a host in IPv4 domain
  through a
• traditional-NAT-PT
• Basic-NAT-PT Operation
• IPv6-B-
• 
  

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• The V4 addresses in the address pool could be
  allocated one-to-one to
• the V6 addresses of the V6 end nodes in which
  case one needs as many
• V4 addresses as V6 end points. In this
  document we assume that the V6
• network has less V4 addresses than V6 end
  nodes and thus dynamic
• address allocation is required for at least
  some of them.
• Say the IPv6 Node A wants to communicate with
  the IPv4 Node C. Node
• A creates a packet with
• Source Address, SAFEDCBA9876543210 and
  Destination
• Address, DA PREFIX132.146.243.30
• NOTE The prefix PREFIX/96 is advertised in
  the stub domain by the
• NAT-PT, and packets addressed to this PREFIX
  will be routed to the
• NAT-PT. The pre-configured PREFIX only needs
  to be routable within
• the IPv6 stub domain and as such it can be any
  routable prefix that
• the network administrator chooses.
• The packet is routed via the NAT-PT gateway,
  where it is translated

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Close

• Even with 20 years of TCP networks UUCP still
  exists
• IPv6 to IPv4 NAT is just an iterim solution, will
  not work with all protocols.
• Yet as a knowledgeable network professional we
  need to know about IPv6 issues.