Detecting Network Attachment in IPv6

Problem Statement

JinHyeock Choi, Samsung AIT

jinchoe@samsung.com

2003.11.11

Contents

• Background/ Movement Detection• DNAv6 Overview• DNAv6 Process• DNAv6 Methods• DNAv6 Problems • DNAv6 Next Steps & Requirement

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

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

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

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

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

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.

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.

0. Node N is attached to AR1 via AP1.

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.

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 In case its IP address is no longer valid, N forms a new IP address.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.

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.

• 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

• 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

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

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

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

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

Current MD implementations

• Investigation Result at the Brussel ETSI