Detecting Network Attachment
in IPv6
Problem Statement
JinHyeock Choi, Samsung AIT
jinchoe@samsung.com
2003.11.11
Contents
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Background/ Movement Detection
DNAv6 Overview
DNAv6 Process
DNAv6 Methods
DNAv6 Problems
DNAv6 Next Steps & Requirement
Background, Movement Detection
Background, Movement Detection
Each AR advertises the different
prefix.
Internet
AR1
A::
There are 3 Wireless Cell for 3
APs.
AR2
B::
AP1
AP2
Cell 1
Cell 2
AR3
C::
AP3
Cell 3
Background, Movement Detection
Each AR advertises the different
prefix.
Internet
AR1
A::
AP1
Link 1
There are 3 Wireless Cell for 3
APs.
AR2
There are only 2 links.
AR3
B::
C::
AP2
AP3
Link 2
* Link:
a communication facility
or medium over which
nodes can communicate
at the link layer
Background, Movement Detection
1. MN is attached to AR1 via AP1
Internet
AR1
AR2
A::
B::
AP1
AP2
Cell 1
Cell 2
MN
AR3
C::
AP3
Cell 3
Background, Movement Detection
1. MN is attached to AR1 via AP1
2. MN changes its attachment to
AP2 and link change has
occurred.
Internet
AR1
A::
AR2
AR3
B::
AP1
AP2
Cell 1
Cell 2
C::
AP3
Cell 3
MN
Background, Movement Detection
1. MN is attached to AR1 via AP1
2. MN changes its attachment to
AP2 and link change has
occurred.
Internet
AR1
A::
AR2
B::
AP1
AP2
Cell 1
Cell 2
3. MN changes its attachment to
AP3 but still remains at the
same link.
AR3
C::
AP3
Cell 3
MN
Background, Movement Detection
1. DNAv6 have to detect
movement quickly when MN
moves from Cell 1 to Cell2.
Internet
AR1
A::
AR2
B::
AP1
AP2
Cell 1
Cell 2
2. MN should not falsely assume
movement when MN moves
from Cell 2 to Cell 3.
AR3
C::
AP3
Cell 3
MN
DNAv6, rough sketch
0. Node N is attached to AR1 via AP1.
Internet
AR1
AR2
AP1
AP2
N
DNAv6, rough sketch
0. Node N is attached to AR1 via AP1.
1. N make an access to AR2 via AP2, a
new link-layer connection has been
established.
Internet
AR1
AP1
N
AR2
2. N receives a hint that link change
may have occurred.
AP2
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 In case its IP address is no longer
valid, N forms a new IP address.
DNAv6, rough sketch
0. Node N is attached to AR1 via AP1.
1. N make an access to AR2 via AP2, a
new link-layer connection has been
established.
Internet
AR1
AP1
N
AR2
2. N receives a hint that link change
may have occurred.
AP2
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.
DNAv6 Process
• 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 Methods
• 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 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
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)
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)
Multi-link Subnet
Link local
Addr, 2
Internet
Router
AP2
Prefix A::
Link local
Addr, 1
Prefix A::
AP1
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 scope of Router Addr & Omission of Prefix information
Link local
Addr, 1
Internet
Router
AP2
Prefix B::
Link local
Addr, 1
Prefix A::
AP1
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.
ECR without L2 support
Internet
R1
R2
R1 advertises
On-Link Prefix A::
R2 advertises
On-Link Prefix B::
AP1
MN
• MN is implemented to send BU whenever hint occurs.
• MN keeps sending BUs whenever a RA arrives.
Current MD implementations
• Investigation Result at the Brussel ETSI