HMIPv6

Mobile-IPv6• Modes for communications between the

mobile node and a correspondent node– Bidirectional tunneling

• Does not require Mobile IPv6 support from the correspondent node

– “Route Optimization“• Requires the mobile node to register its current

binding at the correspondent node. • Packets from the correspondent node can be routed

directly to the care-of address of the mobile node

Mobile Node

Access Router Access Router

Home Agent

“ ”

Corresponding Node

Internet or Intranet

Mobile-IPv6 using Reverse Tunneling

Mobile Node

Access Router Access Router

Home Agent

“ ”

Corresponding Node

Internet or Intranet

Mobile-IPv6 using Route Optimization

Mobile Node

Access Router Access Router

Home Agent

“ ”

Corresponding Node

Internet or Intranet

Mobile-IPv6 Binding Updates

xBindingUpdates

Link UP

Drawbacks of Mobile IPv6• Mobile IPv6

– Reacts after L2 movement– Introduces a period of service disruption after L2 movement

until signaling is completed– Performance depends on Mobile IP registration time and MH-

HA distance• Optimization Schemes

– Fast Handover for Mobile IPv6• Anticipates Mobile IP messaging (before L2 movement)

– Hierarchical Mobile IPv6• Reduces MN to HA round trip delay• Reduces the number of messages (ratio transmission

efficiency)

11.2 Hierarchical Mobile IPv6 (HMIPv6) –RFC4140

• HMIPv6 requires new entities called Mobility Anchor Points (MAPs) in the visiting network.

• MAP acts as a local home agent. • It is usually implemented on a router. • Mobile nodes have to perform binding updates to home

agents and correspondent nodes only when it firstly enters into a MAP domain.

• When mobile nodes move inside the MAP domain, they do not have to perform binding updates to home agent and correspondent nodes. Binding updates to the MAP are only needed.

• If HMIPv6 is not provided in a visited network, a mobile node performs normal MIPv6 protocol and gets connectivity to Internet.

Figure 11-1. Hierarchical Mobile IPv6.

Figure 11-1. Hierarchical Mobile IPv6.

Two types of care-of address are defined for HMIPv6

• on-link care-of address (LCoA) is a CoA used as a CoA in the binding update to MAP.

• regional care-of address (RCoA) is a CoA in the binding update to home agent and correspondent nodes in case of route optimization.

• Only RCoA is registered at the mobile node's home agent and correspondent nodes.

• MAPs keep binding between RCoA and LCoA• home agents keep binding between mobile node's home

address and the primary care-of address (RCoA)

• Movements within MAP are not informed to outer nodes of MAP.

• Only movements between MAPs are notified to home agent, which reduces mobile signaling message exchanges between inner MAP domain and outer network.

11.2.2 Terminology

• Access Router (AR): mobile node's default router.• On-link care-of address (LCoA): LCoA is an address obt

ained from the visited network via stateless address configuration mechanism. – Prefix information is learned from Router Advertisement messag

e from a default router, AR. – In original MIPv6, this address type is simply called care-of addr

ess.• Mobility Anchor Point (MAP): MAP is a special router loc

ated in a visited network by a mobile node. – MAP operates as a local home agent. – Multiple MAPs may exist in a visited network.

• MAP domain: MAP domain is determined by Router Advertisement messages from access routers, which contain MAP information.

• Regional care-of address (RCoA): RCoA is an address obtained from the visited network via stateless address configuration mechanism.– Prefix information is learned from MAP option of the R

outer Advertisement message. – Only this address type is known to domains outside of

MAP.• Local Binding Update: Local Binding is modified

by the Binding Update message to MAP. – Once MAP receives this message, it starts DAD for R

CoA because RCoA may be already occupied. – If there is no conflict, it updates Binding Cache Entry

(BCE) for the binding between RCoA and LCoA of the mobile node.

11.2.2 Terminology

11.2.3 Operation

• when a mobile node enters MAP domain

• When a mobile node moves withinMAP domain

when a mobile node enters MAP domain

Router Advertisement and address configuration

1. When a mobile node visits a network, the node will receive Router Advertisement messages from AR(s).– When HMIPv6 is supported in the visited network, the Advertisement m

essage will contain MAP option to allow the mobile to discover MAP address.

– Available MAP list is kept in the AR and periodically sent using Router Advertisement messages.

2. Once the mobile node receives Router Advertisement messages with the MAP option which contains prefix information for RCoA, it will configure two addresses, RCoA and LCoA by the stateless address configuration mechanism. – In detail, the mobile node learns a prefix for LCoA from Prefix Informatio

n option – a prefix for RCoA from MAP option in the Router Advertisement messag

e. – Then, the mobile node builds RCoA and LCoA by appending 64-bit prefi

x to 64-bit interface identifier.

MAP option - 11.2.5.2 Neighbor Discovery extension

• MAP option is contained in the Option field of Router Advertisement messages to allow mobile nodes to learn MAP address from ARs.

Figure 11-3. Router Advertisement message from access router at step 2 in Fig. 11-2.

Local Binding Update

Figure 11-4. Exchanged messages for MAP Registration at step 4 in Fig. 11-2.

Local Binding Update

3. As the mobile node builds RCoA, the mobile node sends Local Binding Update message to the MAP.– The A and M flags in the Local Binding Update message should

be set to differentiate from the original Binding Update message.– In the Local Binding Update message to MAP, RCoA is regarded

as the home address for the mobile node and contained in the Home Address option. Mobile node's LCoA is used as the source address.

4. Upon MAP receives Local Binding Update message, it binds mobile node's RCoA to its LCoA. Simultaneously, the MAP performs DAD for mobile node's RCoA.

5. The MAP will return a Binding Acknowledgement message to the mobile node, to indicate the result of the binding update to MAP.

6. The mobile node must silently discard any acknowledgement packet from MAP without Type 2 Routing Header, which contains mobile node's RCoA.

bidirectional tunnel

• Once the binding update to the MAP is successfully completed, a bidirectional tunnel between the mobile node and MAP is established.

• Any communication between the mobile node and correspondent nodes should go through the MAP.

• The MAP will perform encapsulation for packets from correspondent nodes or mobile node's home agent to the mobile node

• and also perform decapsulating packets from the mobile node to forward them to correspondent nodes.

binding update to HA and CN• Once the binding update to MAP is successfully completed, binding

updates to home agent and correspondent nodes should be followed.

• These binding updates are same as specified in MIPv6 standard except that RCoA is used as the care-of address.

• LCoA is unknown to outside of MAP domain.• Thus, when HA and CNs sends packets to the mobile node, the Des

tination Address field of packet should be set to the mobile node's RCoA.

• MAP intercepts them and fetches LCoA corresponding to RCoA by referring the binding cache table. – Then, it tunnels packets to the mobile node. – For the tunneling, the Destination Address field is filled with LCoA, and

Source Address field is filled with the address of MAP. – Any delivered packet without Type 2 Routing Header will be discarded i

n the mobile node.

Figure 11-5. Data packet exchange between a mobile node and correspondent node at step 7 in Fig. 11-2.

层次移动 IPv6 信令消息交互图

a mobile node moves withinMAP domain

• If the mobile node changes its physical location within MAP domain, only binding update to MAP is required.

• Thus, the old LCoA in BCE will be replaced by a new one.

• Binding updates to its home agent or correspondent nodes are not necessary.

• The MAP domain is determined by Router Advertisement messages from ARs.

• Since binding updates to home agent and correspondent nodes are not required, the binding update latency may be significantly reduced.

Figure 11-6. HMIPv6 example2: when a mobile node moves into new AR within the sameMAP domain.

Figure 11-7. HMIPv6 Example 3: when a mobile node moves into new MAP domain.Messages for home registration may not pass through MAP.

Hierarchical Mobile IPv6

Handoff Time

HMIPv6

• Motivation– Reduce the number of Bus when MNs move within a MAP

domain– Transparency of the MN’s mobility to CNs– Location Privacy

• HMIPv6– Mobility anchor point (MAP): Local HA– MN acquires two addresses

• On-link CoA: LCoA• Regional CoA: RCoA

– Reduce Mobile IPv6 signaling load– Improve Handoff delay

Extension of MIPv6– Minor extensions to MN operation– CN and HA operation will not be affected

The introduction of the MAP concept– Minimize the latency due to handoffs between AR– Diminish signaling (including wireless resource) costs

MN only perform one local BU to a MAP when changing its location within the MAP domain.

Local Location Transparency– On-Link Address : LCoA, Regional Care-of Address : RCoA– If the MN changes its LCoA within a local MAP domain, it only needs to register the new LCoA with the MAP.– RCoA registered with CNs and the HA does not change.– This makes the MN's mobility transparent to the CNs

Basic Operation of HMIPv6

HMIPv6 Operation

MAP

HACN

Internet

MAP

oldAR

newAR

MAP domain

MN

Local BU

(Home address, RCoA)

(RCoA, LCoA)

Home BU

HMIPv6 Operation

MAP

HACN

Internet

MAP

oldAR

newAR

MAP domain

MN

Local BU

(Home address, RCoA)

(RCoA, LCoA’)

HMIPv6 Operation

MAP

HACN

Internet

MAP

oldAR

newAR

MAP domain

Local BU

(Home address, RCoA’)

(RCoA’, LCoA’)

MN

Home BU

Basic Operation of HMIPv6

Basic Operation of HMIPv6

Basic Operation of HMIPv6

Basic Operation of HMIPv6

Procedure of Dynamic MAP Discoverypropagate the MAP option from the MAP to the MN through the hierarchy of routers.The routers receiving the MAP option propagate them on certain interfaces with Router Advertisement message

Dynamic MAP Discovery

•Furthest MAP– MN may choose to register with the furthest MAP to avoidfrequent re-registrations.– This is particularly important for fast MNs that will performfrequent handoffs.

•Nearest MAP– Network operators may choose a flat architecture in some caseswhere a MIP handoff may be considered a rare event.– In these scenarios, operators may choose to include the MAPfunction in the lowest ARs.– In this scenario, a MN may choose a MAP (in the AR) as ananchor point when performing a handoff.– This kind of dynamic hierarchy (or anchoring) is onlyrecommended for cases where inter-AR movement is not frequent.

MAP Selection in a distributed-MAPs Environment