Internet addressing standards IPv6 versus Network Address Translation NAT

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Internet addressing standardsIPv6 versus
Network Address Translation (NAT)
Jos Vrancken, TU-Delft, josv_at_tbm.tudelft.nl Karst
Koymans, University of Amsterdam,
ckoymans_at_science.uva.nl sponsored by EU project
NO-REST
ICT, Faculty TPM, Delft University of Technology
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What's the problem?

• IPv4 address shortage
• 4 bytes only 4 109 addresses
• e.g. not even one address per human being
• Ambient Intelligence
• any object computerized
• address space needed 1014
• full worldwide connectivity
• mobile objects

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How to solve this problem?

• IPv6
• 128 bit address space (31038)
• optimized towards efficient address handling
• NAT network address translation

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Routing in a network

• Routing is the real problem, not identification
• In large networks hierarchy needed
• Internet currently only two levels
• interdomain routing (OSPF)
• introdomain routing (BGP)

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Pros and Cons of IPv6
Defined by IETF, around 1994, official
status Technically completely implemented --
Not two-way compatible pure IPv6 site not
visible from IPv4 sites - No improvement in
routing - Multi-homing remains unsolved - No
short term advantage for a single user no
gradual stepwise growth no gradual growth in
functionality ? Address space too large risk of
diversity in implementation
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Changing a standard in a network

• Easy in small subnets with high cohesion, low
  coupling (hclc)
• China, Japan
• extreme shortage of IPv4 address space
• hclc by language and cultural barriers
• gt many IPv6 networks
• Very difficult in large networks

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Network Address Translation
NAT router
LAN
Internet
packet header (IP origin, port origin, IP
dest., port dest.) NAT IP port origin
translated to IP router other port
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Problems with NAT

• Ports and protocols are linked globally
• 21 ftp
• 80 http
• 25 smtp
• Clients are fine
• Servers have a problem
• Drop the fixed relation between ports and
  protocols
• gtNAT becomes a real addressing system
• 65000 addresses per LAN
• 48 bit addressing enough for decades

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Advantages of NAT

• Also technically fully implemented
• Short term, local benefits
• Introduces an extra level in the hierarchy
  alleviates the routing problem
• Improved security NAT router is gateway to LAN
• Large, worldwide installed base
• Fully compatible with current Internet
• It can grow stepwise, user by user
• It can grow stepwise functionally

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Conditions for bottom-up adoption of a standard

• Sufficient long term benefits
• solve the real problem!
• Local, short term, per user benefits
• Compatibility with legacy systems
• Applied to the Internet
• No homogeneous addressing for decades