Detecting Wireless Network Attachment

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Detecting Wireless Network Attachment

February 14, 2006

Author: Heikki MahkonenSupervisor: Professor Raimo KantolaInstructor: M.Sc. Tero Kauppinen

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Contents

Objectives and Research Methods IPv6 Information Configuration Mobility Protocols

– Mobility Management– Movement Detection

Detecting Wireless Network Attachment Simulation Environment Results and Conclusions


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Objectives and Research Methods

Objective was to evaluate different network attachment detection methods and how they are suited for wireless network environments.

Provide a simulation environment for further mobility protocol research for Ericsson Research, Finland (NomadicLab).

The first objective was conducted as a literature study. The simulation environment was implemented as a part of this

Master’s thesis. Different movement detection mechanisms were simulated and

their behavior compared and analyzed to produce results and conclusions.


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IPv6 Information Configuration IPv6 Neighbor Discovery (RFC 2461)

– Message exchange– Data structures

Router list Prefix list Neighbour cache Destination cache

Parameter Discovery– Router Advertisement– Router Solicitation

Stateless and stateful address autoconfiguration.– Stateless Address Autoconfiguration (SAA) (RFC 2462) – Dynamic Host Configuration Protocol for IPv6 (DHCPv6) (RFC 3315)

Duplicate Address Detection (DAD)– Neighbor Solicitation– Neighbor Advertisement

Neighbor Unreachability Detection (NUD)– Neighbor Solicitation– Neighbor Advertisement


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IPv6 Information Configuration Router Advertisement and Solicitation Messages

Type=134 Code=0 ChecksumCHL M O Res. Router Lifetime

Reachable TimeRetrans Timer

Options...

Type=134 Code=0 ChecksumReserved

Options...

Router Advertisement Router Solicitation

Prefix Information Option

Type=3 L ALength Prefix Len.Valid LifetimePreferred Lifetime

Prefix

Res.

Reserved2


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IPv6 Information ConfigurationMobile Host

IPv6 ND Access RouterMH Stateful AddressAutoconfiguration

MH Stateless AddressAutoconfiguration

1. Router Advertisement

* [forever]

RA retrans.timer (3-16 sec.)

2. Router Solicitation3. Router AdvertisementRS retrans.

timer (1 sec.)

4. RA received* [3 or if RA received]

5a. [M:=No] Configure Address

5b. [M:=Yes] Configure address

6a. Address

6b. Address

8. [O:=Yes] Configure IPv6 information

9. IPv6 Information

7a. Neighbour Solicitation (DAD)

7b. Neighbour Solicitation (DAD)

* [number of prefixes in RA]

10. Check reachability 11. Neighbour Solicitation12. Neighbour Advertisement

Parameter Discovery

Address Autoconfiguration

DuplicateAddressDetection

NeighbourUnreachableDetection

DAD timer

DAD timer

RA received

RA received

RA delaytimer (0 – 0.5 sec.)

RS delaytimer (0 - 1 sec.)


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Mobility Protocols Mobility protocols work on network and upper OSI

reference model layers. Different mobility protocols for different OSI reference

model layers.

Data-link layerPhysical layer

HIP Mobility

Sockets

Transport layer

Network layer

Session layer

Application layer SIP Mobility

Session LayerMobility

SCTP Mobility

MIPv6

TCP Mobility UDP Mobility

UpperLayers

LowerLayers


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Mobility Protocols Mobility protocols provide a mobile host a way to retain

Internet connectivity while changing attachment point to the Internet.

Mobility for a mobile host is achieved by providing distinction between location and identity of the mobile host.

Mobility protocol can be divided into three parts– location update– location management– movement detection


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Mobility Protocols

Internet AccessNetwork

MH

WLAN Foreign Link

WLAN Home Link

CH

HA

Router

Router

Data

Data BU BA

Location Update in MIPv6.


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Mobility Protocols

Internet AccessNetwork

MH

WLAN Foreign Link

WLAN Home Link

CH

BUBA

DataData

Router

HA

Location Management in MIPv6.

Data

Router


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Mobility Protocols Movement detection signals the attachment changes of the mobile host to the mobility protocol. Two movement detection mechanisms are defined to give comparison for the DNAv6 optimized movement detection mechanisms in the simulations. Basic Movement Detection

– Bases on the data structures provided by the IPv6 ND.– Uses the signaling provided by the IPv6 ND.

Link-layer Notification Enhanced Movement Detection– Uses the Link-layer notifications to trigger IPv6 information configuration.– Needs ”link up” and ”link down” notifications from network interface to work.


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Mobility ProtocolsMobile Host

IPv6 ND Access RouterMobile Host AddressAutoconfiguration

1. Router Advertisement(from a new router)

Mobile HostIPv6 ND NC

Mobile HostRAI Timer

5. Check reachability 6. Neighbour Solicitation7. Neighbour Advertisement

9. Check reachability 10. Neighbour Solicitation

4. Create NC elememt

NC timer

ND retrans timer

8. NC element reachable

25. NC element unreachable

3. Start RAI timer

RAI timer

23. Remove addresses

11. Purge IPv6information

13. Neighbour Solicitation14. Neighbour Advertisement15. Access router reachable

RAI timer 17. Neighbour Solicitation

ND retrans timer 21. Purge IPv6information

NC timer

12. RAI timer expired

16. RAI timer expired

2. Select default router

22. Purge IPv6 information

26. Stop RAI timer

19. Update address lifetimes

18. Router Advertisement(from the same router)

20. Restart RAI timer

24. Purge routerand prefix list


21. Update routerand prefix list timers


30. Neighbour Advertisement29. Neighbour Solicitation

31. Signal movement

Mobile HostMobility Protocol

Basic Movement Detection


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Mobility ProtocolsMobile Host

IPv6 ND Access RouterMobile Host AddressAutoconfiguration

4. Router Advertisement

12. Remove addresses



9. Update address lifetimes

8. Router Advertisement(from the same router)

13. Purge routerand prefix list


10. Update routerand prefix list timers

1. Link Up

3. Router Solicitation

6. Link Down



17. Neighbour Advertisement16. Neighbour Solicitation


18. Signal movement

RA delaytimer (0 – 0.5 sec.)

2. Neighbour Solicitation (DAD)

Link-layer Enhanced Detection


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Detecting Wireless Network Attachment IETF DNA (Detecting Network Attachment) Working

Group.“The purpose of the DNA working group is to define standards track and BCP documents that allow hosts to detect their IP layer configuration and connectivity status quickly, proposing some optimization to the current specifications that would allow a host to reconfigure its IPv6 layer faster than today.” (IETF DNA Working Group)

Contributions:– RFC 4135: Goals of Detecting Network Attachment in IPv6.– Draft: BCP for Hosts.– Draft: BCP for Routers.– Draft: Link-layer Event Notifications for DNA.– Draft: Fast Router Discovery with L2 Support.– Draft: DNA with unmodified routers: Prefixlist based approach.– Draft: Detecting Network Attachment in IPv6 Networks (DNAv6)


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Detecting Wireless Network Attachment DNAv6 Problems

– Link identification issues.– Delay Issues.– Issues with wireless network environments.

DNAv6 Goals– The DNA solution must detect whether the mobile host must configure the IPv6 information on a newly attached link.– The delay for identifying the link and possible IPv6 information configuration must be minimized.– The DNA solution must not falsely assume that the link change has occurred and initiate a re-configuration of the IPv6 information.– The DNA solution must keep the signaling needed for the detection process at minimum.– The DNA solution must reuse the existing signaling mechanisms.– The DNA solution must use the link-local signaling for the detection procedure and there must be no need for global IPv6 addresses for the detection process.– The DNA solution must also function on links where secure ND.– The security vulnerabilities in the IPv6 information configuration must not be increased by the DNA solution.– There must be appropriate backward compatibility with hosts and access routers using the DNA solution and with hosts and access routers not utilizing the DNA solutions.– The DNA solution must take into account the characteristics of the wireless network environments.


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Detecting Wireless Network Attachment Best Current Practices for Hosts and Routers

– Configuration instructions for hosts and routers.– Does not provide/demand any implementation add-ons to

existing protocols. Fast Router Discovery (FRD) with L2 Support

– Specifies a way to disscover access routers as fast as possible in the WLAN access networks.

– Uses a L2 support in the WLAN AP.– The ”link up” notifications sent to the access router or the

AP caches and proxies the RA messages to mobile hosts.


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Detecting Wireless Network Attachment DNAv6 specifies a optimal solutions for the link identification and fast

routter discovery. Satisfies all the goals specified in the RFC 4135. Defines three data structures.

– For router: ”DNARouterList” ”DNARouterPrefixList”

– For mobile host: ”DNAHostPrefixList”

Landmark prefix– The prefix which the mobile host is currently using.

Link identifier prefix– Access routers choose the numerically smallest prefix to be used as the

LinkID prefix.– At least this prefix must be added to every RA message.

Fast Router Advertisement– ”DNARouterList” has a router tokens (SHA-1 hash of the access router

address).– Source address in the RS message is hashed and compared to the router

tokens (XOR) to get the ”ranking” of the router.– Router with ranking zero will answer first.– RA delay is the ”rankin” multiplied by RASeparation (20) milliseconds.


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Detecting Wireless Network Attachment DNAv6 uses two flags in the RA message.

– D flag indicates DNAv6 compatibility.– C flag indicates that the RA message carries complete set of network prefixes.

DNAv6 specifies two new options to RS and RA messages.

Type=134 Code=0 ChecksumCHL M O Router Lifetime

Reachable TimeRetrans Timer

Options...

Router Advertisement

Landmark Prefix Option

Type Y NLength Prefix Len.Reserved

Landmark Prefix

Res.

D C R

Learned Prefix Option

Type Length Prefix L. 1

Prefix 1

Prefix L. 2... Prefix L. N Padding

Prefix 2

Prefix N

...


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Detecting Wireless Network Attachment DNAv6 operation for an access router.

Access Router Other AccessRouters on link Mobile Host

1. Bootstrap

Access RouterDNARouterList

Access RouterDNARouterPrefixList

1. Router Advertisement (D=0, C=0)2. Router Solicitation3. Router Advertisement (D=1, C=1)4. Store router

5. Store prefix

6. Router Advertisement (D=1, C=1)

8. Update prefix

7. Update router

9. Router Solicitation


11. Router Solicitation (without LMPO)


15. Get ranking

16. Ranking

13. Get learned prefixes

14. Learned prefix option

18. Router Solicitation (with LMPO)

27. Router Advertisement (D=1, C=1 &LMPO)

25. Get ranking

26. Ranking

19. Check landmark prefix

23. Get learned prefixes

24. Learned prefix option

Access RouterIPv6 ND

22. Result

21. Check landmark prefix

20. Result

RA delaytimer

RA delaytimer

RA delaytimer

RA delaytimer


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Detecting Wireless Network Attachment DNAv6 operation for a mobile host.

Mobile HostIPv6 ND Access RouterMobile Host Address

Autoconfiguration

5. Router Advertisement (D=1,C=1 & to unicast)


1. Link Up (establish)

4. Router Solicitation (with TSLLAO)


RA delaytimer

3. Neighbour Solicitation (DAD)

12. Router Advertisement(D=1,C=1, with LMPO & to unicast)

14. Identify the link

9. Link Up(re-establish)

11. Router Solicitation (with TSLLAO & LMPO)RA delaytimer

10. Addresses to”optimistic” state

15. Identify the link

Mobile HostDNAHostPrefixList

16. Check LMPO

17. Check prefixes in the IPv6 ND prefix list

2. Link-layer addressein ”optimistic” state

7. Link-layer addressin ”preferred” state

DAD timer6. Add prefixes

13. Add prefixes

18. Check prefixes

19. Result

20a. Addresses to”preferred” state

20b. Purge all IPv6 informationand reconfigure it

21b. Select default router

22. Select defaultrouter

23. Signal movement


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Simulation Environment Simulation environment was implemented into NS2

(Network Simulator 2).– IEEE 802.11 Management frames.

Beacon Frame Probe Request and Response Association Request and Response

– Basic IPv6 ND implementation. RS,RA,NS and NA message exchange. IPv6 ND NC for mobile host. Parameter discovery, SAA, NUD, DAD.

– MIPv6 implementation without route optimization.– Three different MD types (Basic, LL Enhanced and DNAv6).– Two DNAv6 solutions for routers (DNAv6 and the FRD).


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Simulation Environment

MH

HA Router

CH

MH

MHMH

1.

2.

3.

4.

Simulation environment includes:– Mobile host (MH), Home Agent (HA), Correspondent Host (CH) and foreign access router.– Home and foreign WLAN access networks.

Four handover scenarios were simulated.


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Results Simulation results from 4 handover scenarios.


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Results Simulation results from 4 handover scenarios when FRD is used.


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Results Simulation results from 4 handover scenarios.

Simulation results from 4 handover scenarios when FRD is used.


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Conclusions

The DNAv6 solutions performes best in every handover scenario.

The DNAv6 offers good base for standardized MD mechanism (access routers and mobile hosts).

The FRD is a good solution for WLAN networks.– Does not require implementation changes to the mobile

hosts.– Only for WLAN. Should be generalized for other wireless

network technologies as well. Further work:

– DNAv4 and DNAv6 interoperability.– Work on the simulation environment.


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Documents

Detecting Wireless Network Attachment