Designing a DHCPv6 server and client on Linux

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Designing a DHCPv6 server and client on Linux

• Mehnaz Farooqui
• Nikhil U Moorthy
• Swaroop Krishnamurthy

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Presentation Overview

• Evolution of the protocol
• DHCPv4
• Transition to DHCPv6
• DHCPv6
• Current Implementation of DHCPv6
• Limitation and Future enhancements

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Evolution of DHCP

• Framework for passing configuration information
  to hosts on a TCP/IP network.
• Evolved from BOOTP and RARP (networks that had
  diskless nodes).
• Era of centralized computing.
• Proliferation of distributed computing (DC)
  required a protocol like DHCP.
• Addresses the resource boot strap needs of such a
  DC environment (requiring centralized resource
  management).

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RARP
Network 1
Network 2
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BOOTP
Network 1
Network 2
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Introduction to DHCPv4

• Framework for passing configuration information
  to hosts on an IPv4 network.
• Backward compatibility with BOOTP.
• Automatic allocation of reusable network
  addresses and additional configuration options.
• Reduces the cost of ownership by centralizing the
  management of network resources.
• 3 kinds of agents involved
• DHCP client
• DHCP server
• DHCP relay agent

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DHCPv4 BOOTP similarities

• Message format is the same
• Clients can co-exist.
• DHCP also captures the behavior of BOOTP relay
  agents.
• Clients use retransmission similar strategies.

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DHCPv4 BOOTP differences
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DHCPv4 Client/Server interaction
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DHCPv6 The Need

• IPv4 is the currently used version of the
  Internet Protocol.
• IPv4 has become a victim of its own popularity
  it is running out of addresses.
• IPv6 has been designed and being deployed to
  counter this and other issues.
• Need to extend the functionality of DHCP to IPv6
  based networks too. Hence DHCPv6 is being
  developed.

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DHCPv6

• Enables servers to pass configuration parameters
  to IPv6 nodes.
• Automatic allocation of reusable network
  addresses and additional configuration
  flexibility.
• Compatible with
• IPv6 stateless address auto configuration.
• Statically configured nodes.
• Non-participating nodes
• Existing protocol implementations.
• Superset of DHCPv4.
• Benefits from the additional features of IPv6.
• Freedom from the constraints of backward
  compatibility with BOOTP.

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DHCPv6 Extensibility

• Easily extensible in order to carry new
  configuration parameters through the addition of
  new DHCPv6 "options" defined to carry this
  information.

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DHCPv6 Terminology

• IA (Identity Association)
• DUID (DHCP Unique Identifier)
• Binding
• Lease

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DHCPv6 Security

• DHCP Threat Model
• Threat to DHCP clients
• Rogue server
• Denial of Service attack
• Accidentally configured server
• Threat to DHCP servers
• Theft of service
• Denial of Service attack
• Summary of DHCP authentication
• Authentication option
• Replay Detection method
• Delayed Authentication protocol

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DHCPv6 Implementation

• Both the server and client code have been written
  in C language.
• Compilation of the packages can be done using any
  C compiler like gcc.
• Linux was chosen as the platform for 2 reasons
• No implementation of DHCPv6 was present for this
  platform.
• The extensive documentation and open source
  nature of Linux.

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Software Design Issues

• Server
• Binding structure
• Allocation policy
• Persistence of bindings
• Periodic removal of expired nodes
• Client
• Selection of best server
• Binding structure
• Timer implementation A Threaded approach
• Lookup table of transaction id and thread wait
  conditions

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DHCPv6 Server Design
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DHCPv6 Client Design
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Limitations

• Relay agent has not been implemented.
• Security model of DHCPv6 has not been
  implemented.
• All the message types and option types mentioned
  in the draft have not been incorporated into the
  project.
• Server and client can be deployed only on Linux
  based platforms.
• Does not work on diskless nodes due to presence
  of configuration files.
• Dependency on other packages like ifconfig.

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Improvements

• Implement the relay agent so as to allow the
  server and client to run on separate subnets.
• Implementing the basic security features.
• Cover all the message types and option types in
  future versions.
• Implementing a DHCPv6 server in Java to counter
  deployment and portability issues.
• Eliminate dependencies on other packages.

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Thank You