Detecting Network Attachment in IPv6 Problem Statement
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Detecting Network Attachment in IPv6
Problem Statement
JinHyeock Choi, Samsung AIT
2003.11.11
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Contents
• Background/ Movement Detection• DNAv6 Overview• DNAv6 Process• DNAv6 Methods• DNAv6 Problems • DNAv6 Next Steps & Requirement
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A R 1 A R 3
A R 2
H A C N
R o u t e r 2
R o u t e r 1
A : :
A P 1
A P 2
A P 3
B : :
C : :
C e l l 1
H u b
C e l l 3
M N
C e l l 2
Background, Movement Detection
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Internet
AR1
AP1 AP2
AR2 AR3
AP3
Cell 1 Cell 2 Cell 3
There are 3 Wireless Cell for 3 APs.
Each AR advertises the different prefix.
A:: B:: C::
Background, Movement Detection
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Internet
AR1
AP1 AP2
AR2 AR3
AP3
There are only 2 links.
Link 1 Link 2
There are 3 Wireless Cell for 3 APs.
Each AR advertises the different prefix.
A:: B:: C::
Background, Movement Detection
* Link: a communication facility or medium over which nodes can communicate at the link layer
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Internet
AR1
AP1 AP2
AR2 AR3
AP3
1. MN is attached to AR1 via AP1
Cell 1 Cell 2 Cell 3
MN
A:: B:: C::
Background, Movement Detection
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Internet
AR1
AP1 AP2
AR2 AR3
AP3
1. MN is attached to AR1 via AP1
2. MN changes its attachment to AP2 and link change has occurred.
MN
Cell 1 Cell 2 Cell 3
A:: B:: C::
Background, Movement Detection
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Internet
AR1
AP1 AP2
AR2 AR3
AP3
1. MN is attached to AR1 via AP1
2. MN changes its attachment to AP2 and link change has occurred.
Cell 1 Cell 2 Cell 3
MN
A:: B:: C::
Background, Movement Detection
3. MN changes its attachment to AP3 but still remains at the same link.
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Internet
AR1
AP1 AP2
AR2 AR3
AP3
Cell 1 Cell 2 Cell 3
MN
A:: B:: C::
Background, Movement Detection
1. DNAv6 have to detect movement quickly when MN moves from Cell 1 to Cell2.
2. MN should not falsely assume movement when MN moves from Cell 2 to Cell 3.
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0. Node N is attached to AR1 via AP1.
DNAv6, rough sketch
Internet
AR1
N
AP1 AP2
AR2
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0. Node N is attached to AR1 via AP1.
2. N receives a hint that link change may have occurred.
3. N checks whether it still is at the same link.
- If so, it can still reach its current AR and don’t need to perform DNAv6 anymore.
4. If not, a node discovers a new AR with the prefix information.
DNAv6, rough sketch
- N receives a RA and checks the prefixes in it.
5. In case its IP address is no longer valid, N forms a new IP address.
Internet
AR1
N
AP1 AP2
AR2
1. N make an access to AR2 via AP2, a new link-layer connection has been established.
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DNAv6, rough sketch
Internet
AR1
N
AP1 AP2
AR2
0. Node N is attached to AR1 via AP1.
2. N receives a hint that link change may have occurred.
3. N checks whether it still is at the same link.
- If so, it can still reach its current AR and don’t need to perform DNAv6 anymore.
4. If not, a node discovers a new AR with the prefix information.
- N receives a RA and checks the prefixes in it.
5. In case its IP address is no longer valid, N forms a new IP address.
1. N make an access to AR2 via AP2, a new link-layer connection has been established.
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• Step1: Hint• Step2: Detecting the link change.
– Checking the reachability of current default router.
• Step3: Router Discovery with the prefix information.– Checking the validity of current IP address
DNAv6 Process
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• Step1: Hint– Link layer hint
– New RA message
– RA beaconing
• Step2: Checking the Link change.– Checking the reachability of current default router.
• NUD like (3 NSs)
• 1 NS and timeout
• RA beaconing
• Step3: Router Discovery with the prefix information.– RS/ RA exchange
DNAv6 Methods
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DNAv6 Problems
• No means to represent a link– In RA message, neither router address nor prefixes can do it.
– Link-layer hint can’t detect Link change by itself.
• The ambiguity of RA information – Link local scope of router address
– Prefix omission
• The delay to check the reachability of current AR– It’s difficult to detect something is NOT there.
– Roughly 3 secs for NUD
• Random Delay in RS/ RA exchange• No agreed way to do DNAv6
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DNAv6 Goals with Requirements
• Update a RA message format, which– can represent a link
– doesn’t have performance degrading ambiguities.
• Specify a operational procedure, which– can quickly detect link change
– can quickly receive a RA with the prefix information.
• Define a DNAv6 scheme such that– Fast: low time delay
– Precise/ Secure: Little error
– Efficient: limit signaling (NS/NA or RS/RA)
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Appendix: MD Pathologies
• Multi-link Subnet• Link local scope of Router Addr with Omission of Prefix
Information• ECS without L2 support• Current MD implementations (from ETSI
interoperability test)
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Multi-link Subnet
RouterInternet
Prefix A::
Prefix A::
AP1
AP2
MN
• Assume Router has two interface with two different link local addresses. To each interface, an AP is attached.
• Through each interface, the Router advertises the same Prefix A:: without setting L bit.
• When a MN moves from AP1 to AP2, it changes its default router address but can keep using its CoA.
• Should we design DNAv6 to accommodate this case or can we safely ignore this as a pathological exception?
Link local Addr, 1
Link local Addr, 2
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Link local scope of Router Addr & Omission of Prefix information
RouterInternet
Prefix A::
Prefix B::
AP1
AP2
MN
• Assume Router has two interface with the same link local addresses. To each interface, an AP is attached.
• Through each interface, the Router advertises two different prefixes, A:: & B:: without setting L bit.
• Assume a MN has moved from AP1 to AP2. • If a router omitted prefix from its RA, MN can’t detects movement with RA
messages.
Link local Addr, 1
Link local Addr, 1
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Internet
R1 R2
R1 advertisesOn-Link Prefix A::
• MN is implemented to send BU whenever hint occurs. • MN keeps sending BUs whenever a RA arrives.
R2 advertisesOn-Link Prefix B::
ECR without L2 support
AP1 MN
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Current MD implementations
• Investigation Result at the Brussel ETSI