Detecting Wireless Network Attachment
Author: Heikki Mahkonen
Supervisor: Professor Raimo Kantola
Instructor: M.Sc. Tero Kauppinen
February 14, 2006
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
Router Advertisement
Router Solicitation
Type=134 Code=0
Checksum
CHL
M O Res. Router Lifetime
Reachable Time
Retrans Timer
Type=134 Code=0
Checksum
Reserved
Options...
Options...
Prefix Information Option
Type=3 Length Prefix Len. L A Res.
Valid Lifetime
Preferred Lifetime
Reserved2
Prefix
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IPv6 Information Configuration
MH Stateful Address
Autoconfiguration
MH Stateless Address
Autoconfiguration
Mobile Host
IPv6 ND
Access Router
1. Router Advertisement
RA retrans.
timer (3-16 sec.)
RA received
RS delay
timer (0 - 1 sec.)
* [forever]
2. Router Solicitation
RS retrans.
timer (1 sec.)
3. Router Advertisement
RA delay
timer (0 – 0.5 sec.)
RA received
* [3 or if RA received]
4. RA received
Address Autoconfiguration
Parameter Discovery
5a. [M:=No] Configure Address
6a. Address
7a. Neighbour Solicitation (DAD)
DAD timer
* [number of prefixes in RA]
5b. [M:=Yes] Configure address
6b. Address
7b. Neighbour Solicitation (DAD)
DAD timer
8. [O:=Yes] Configure IPv6 information
9. IPv6 Information
10. Check reachability
Neighbour
Unreachable
Detection
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Duplicate
Address
Detection
11. Neighbour Solicitation
12. Neighbour Advertisement
2006-01-12
Mobility Protocols
 Mobility protocols work on network and upper OSI
reference model layers.
 Different mobility protocols for different OSI reference
model layers.
Upper
Layers
Application layer
Sockets
Session layer
Transport layer
SIP Mobility
Session Layer
Mobility
SCTP Mobility
TCP Mobility
UDP Mobility
HIP Mobility
Network layer
Lower
Layers
MIPv6
Data-link layer
Physical layer
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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
 Location Update in MIPv6.
MH
WLAN Home
Link
Data
HA
Internet
WLAN Foreign
Link
Data
Router
BU
Access
Network
BA
Router
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CH
Mobility Protocols
 Location Management in MIPv6.
MH
WLAN Home
Link
Data
HA
Internet
Data
Router
Access
Network
BU
WLAN Foreign
Link
BA
Router
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CH
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 Protocols

Basic Movement Detection
Mobile Host
Mobility Protocol
Mobile Host
RAI Timer
Mobile Host
IPv6 ND NC
Mobile Host Address
Autoconfiguration
Mobile Host
IPv6 ND
3. Start RAI timer
Access Router
1. Router Advertisement
(from a new router)
2. Select default router
4. Create NC elememt
NC timer
5. Check reachability
6. Neighbour Solicitation
8. NC element reachable
NC timer
9. Check reachability
RAI timer
10. Neighbour Solicitation
ND retrans timer
12. RAI timer expired
15. Access router reachable
RAI timer
7. Neighbour Advertisement
16. RAI timer expired
11. Purge IPv6
information
13. Neighbour Solicitation
14. Neighbour Advertisement
17. Neighbour Solicitation
ND retrans timer
21. Purge IPv6
information
18. Router Advertisement
(from the same router)
19. Update address lifetimes
20. Restart RAI timer
22. Purge IPv6 information
21. Update router
and prefix list timers
23. Remove addresses
25. NC element unreachable
24. Purge router
and prefix list
26. Stop RAI timer
27. Select default router
28. Select default router
29. Neighbour Solicitation
30. Neighbour Advertisement
31. Signal movement
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Mobility Protocols

Link-layer Enhanced Detection
Mobile Host
Mobility Protocol
Mobile Host Address
Autoconfiguration
Mobile Host
IPv6 ND
Access Router
1. Link Up
2. Neighbour Solicitation (DAD)
3. Router Solicitation
4. Router Advertisement
RA delay
timer (0 – 0.5 sec.)
5. Select default router
6. Link Down
7. Purge IPv6 information
8. Router Advertisement
(from the same router)
9. Update address lifetimes
11. Purge IPv6 information
10. Update router
and prefix list timers
12. Remove addresses
13. Purge router
and prefix list
14. Select default router
15. Select default router
16. Neighbour Solicitation
17. Neighbour Advertisement
18. Signal movement
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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.
–
–


Landmark prefix
–
The prefix which the mobile host is currently using.
Link identifier prefix
–
–

For router:
 ”DNARouterList”
 ”DNARouterPrefixList”
For mobile host:
 ”DNAHostPrefixList”
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.
Learned Prefix Option
Router Advertisement
Type
Type=134 Code=0
Checksum
CHL
M O D C R Router Lifetime
Reachable Time
Retrans Timer
Length Prefix L. 1 Prefix L. 2
...
Prefix L. N
Padding
Prefix 1
Options...
Prefix 2
Landmark Prefix Option
Type
...
Length Prefix Len. Y N Res.
Prefix N
Reserved
Landmark Prefix
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Detecting Wireless Network Attachment
 DNAv6 operation for an access router.
Access Router
IPv6 ND
Access Router
DNARouterPrefixList
Access Router
DNARouterList
Access Router
1. Bootstrap
Other Access
Routers on link
Mobile Host
1. Router Advertisement (D=0, C=0)
2. Router Solicitation
4. Store router
3. Router Advertisement (D=1, C=1)
RA delay
timer
5. Store prefix
6. Router Advertisement (D=1, C=1)
7. Update router
8. Update prefix
9. Router Solicitation
RA delay
timer
10. Router Advertisement (D=1, C=1)
11. Router Solicitation (without LMPO)
13. Get learned prefixes
14. Learned prefix option
15. Get ranking
16. Ranking
RA delay
timer
19. Check landmark prefix
17. Router Advertisement (D=1, C=1)
18. Router Solicitation (with LMPO)
20. Result
21. Check landmark prefix
22. Result
23. Get learned prefixes
24. Learned prefix option
25. Get ranking
26. Ranking
RA delay
timer
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27. Router Advertisement (D=1, C=1 &
LMPO)
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Detecting Wireless Network Attachment
 DNAv6 operation for a mobile host.
Mobile Host
Mobility Protocol
Mobile Host
DNAHostPrefixList
Mobile Host Address
Autoconfiguration
Mobile Host
IPv6 ND
Access Router
1. Link Up (establish)
2. Link-layer addresse
in ”optimistic” state
DAD timer
6. Add prefixes
3. Neighbour Solicitation (DAD)
4. Router Solicitation (with TSLLAO)
5. Router Advertisement (D=1,C=1 & to unicast)
RA delay
timer
7. Link-layer address
in ”preferred” state
8. Select default router
9. Link Up
(re-establish)
10. Addresses to
”optimistic” state
13. Add prefixes
11. Router Solicitation (with TSLLAO & LMPO)
12. Router Advertisement
(D=1,C=1, with LMPO & to unicast)
RA delay
timer
14. Identify the link
15. Identify the link
16. Check LMPO
17. Check prefixes in the IPv6 ND prefix list
18. Check prefixes
19. Result
20a. Addresses to
”preferred” state
20b. Purge all IPv6 information
and reconfigure it
21b. Select default router
22. Select default
router
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

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.
CH
HA
Router
4.
MH
MH
2.
1.
3.
MH
MH
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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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