IP Mobility

Dr. Eng. Amr T. Abdel-Hamid

NETW 903

Winter 2010

Netw

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Services

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Mobility and Standard IP Routing

IP assumes end hosts are in fixed physical locations What happens if we move a host between networks?

IP addresses enable IP routing algorithms to get packets to the correct network Each IP address has network part and host part

This keeps host specific information out of routers DHCP is used to get packets to end hosts in networks

This still assumes a fixed end host What if a user wants to roam between networks?

Mobile users don’t want to know that they are moving between networks

Why can’t mobile users change IP when running an application?

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No mobility High mobility

mobile wireless user, using same access point

mobile user, passing through multiple access point while maintaining ongoing connections (like cell phone)

mobile user, connecting/ disconnecting from network using DHCP.

Moderate mobility

Mobility Classification Protocols

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Mobility

Micro Macro Global

Intra-subnet

Intra-domain Inter-domain

Cellular IP

(1998)

TMIP

(2001)

TeleMIP (2000)

Hierarchical MIP (1996)

Hawaii (1999)

Dynamic Mobility Agent (2000)

HMIPv6 (2001)

MIP

(1996)

MIPv6

(2001)

Time (evolutionary path)

Mobility Classification Protocols

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Wirelss access networks and mobile IP

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Mobile IP Mobile IP was developed as a means for transparently

dealing with problems of mobile users Enables hosts to stay connected to the Internet regardless of their

location Enables hosts to be tracked without needing to change their IP

address Requires no changes to software of non-mobile hosts/routers Requires addition of some infrastructure Has no geographical limitations Requires no modifications to IP addresses or IP address format Supports security

Could be even more important than physically connected routing

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Mobile IP Entities

Mobile Node (MN) The entity that may change its point of attachment from network

to network in the Internet Detects it has moved and registers with “best” FA

Assigned a permanent IP called its home address to which other hosts send packets regardless of MN’s location

Since this IP doesn’t change it can be used by long-lived applications as MN’s location changes

Home Agent (HA) This is router with additional functionality Located on home network of MN Does mobility binding of MN’s IP with its COA Forwards packets to appropriate network when MN is away

Does this through encapsulation

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Mobile IP Entities contd.

Foreign Agent (FA) Another router with enhanced functionality If MN is away from HA the it uses an FA to send/receive data

to/from HA Advertises itself periodically Forward’s MN’s registration request Decapsulates messages for delivery to MN

Care-of-address (COA) Address which identifies MN’s current location Sent by FA to HA when MN attaches Usually the IP address of the FA

Correspondent Node (CN) End host to which MN is corresponding (eg. a web server)

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22.10.2007

9

Mobile IP (MIPv4)

Internet

Home Agent

R

R

R

Home network A

Foreign Network B

Network C

Correspondent Node C

Foreign Agent

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Step1:Agent Discovery

RBHFMGV bits reserved

type = 16

type = 9 code = 0 = 9

checksum = 9

router address

standard ICMP fields

mobility agent advertisement

extension

length sequence #

registration lifetime

0 or more care-of-addresses

0 8 16 24

R bit: registration required

H,F bits: home or foreign agent

B bit: Busy

M, G bit: Minimal, Generic encapsulation

V bit: Van JacobHeader compression

Agent Advertisement

Agent Solicitation

Type=10 | code | checksum

reservedWith TTL=1

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Step 2: Registration

Internet

Home Agent

Mobile Node

R

R

R

Foreign Network B

Network C

Home Network A

CorrespondentNode C

Foreign Agent

Foreign agent sends Binding Update

Home Agent replies with Binding Acknowledgement

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Step 2: Registration (Example)

Home address Care-of address Lifetime (sec)

128.119.40.186 79.129.13.2 150

… … …

Mobility binding table at Home Agent

Home address Home agent address

Media address Lifetime

128.119.40.186 128.119.40.7 00-56-80-56-A1-E1 150

Visitor List at Foreign Agent

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Step 2: Registration (Example)

visited network: 79.129.13/24 home agent

HA: 128.119.40.7 foreign agent

COA: 79.129.13.2 COA: 79.129.13.2

….

ICMP agent adv. Mobile node

MA: 128.119.40.186

registration req.

COA: 79.129.13.2 HA: 128.119.40.7 MA: 128.119.40.186 Lifetime: 9999 identification:714

….

registration req.

COA: 79.129.13.2 HA: 128.119.40.7 MA: 128.119.40.186 Lifetime: 9999 identification: 714 encapsulation format

….

registration reply

HA: 128.119.40.7 MA: 128.119.40.186 Lifetime: 4999 Identification: 714 encapsulation format

….

registration reply

HA: 128.119.40.7 MA: 128.119.40.186 Lifetime: 4999 Identification: 714

….

time

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Reg. request format

Reg. reply format

Step 2: Registration

Minimal Encapsulation format

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Step 3: Indirect Routing via Tunneling

Permanent address: 128.119.40.186 Care-of address:

79.129.13.2dest: 128.119.40.186

packet sent by correspondent

dest: 79.129.13.2 dest: 128.119.40.186

packet sent by home agent to foreign agent: a packet within a packet (Tunnel)

dest: 128.119.40.186

foreign-agent-to-mobile packet

•Home agent broadcasts ARP request which causes all nodes in the Home network to update their ARP caches to map the mobile nodes IP address to the home agents link level address.

mobile replies directly to correspondent

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RO(Operation 1: Binding Cache)

Internet

homenetwork

visitednetwork

4

2

1

First Packet to mobile host

Binding update

CN

3

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Internet

homenetwork

visitednetwork

4

53

CN

Subsequent packets to the mobile host

RO (Operation 1: Binding Cache)

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RO(Operation 2: Smooth handoff)

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Internet

foreign network visited at session start

FA

2

New FA

1

5

CN

New Foreign network

homenetwork

Binding Update

4

RO (Operation 2: Smooth handoff)

Binding Update

Binding Warning

3

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If the FA and Mobile node share a security association, the FA can choose the new registration key

If the HA and the FA share a security association, the HA can choose the new registration key

If the FA has a Public key, the HA can supply a new registration key If the Mobile node includes its’ Public key in the registration request, the

FA can choose the new registration key The Mobile node and its’ FA can execute a D-H key exchange protocol

to get a new registration key

RO (Operation 3: Establishing Registration keys)

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RO(Operation 4: Special Tunnels)

Internet

FA1 rebooted

FA2

3

CN

New Foreign network

homenetwork

Binding Update

4

Special Tunnel

2

1

No visitor list or Binding cache

[(CN,FA1), (CN, MH),…]

[(FA1, MH), (CN, MH),…]

same

5

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Ingress Filtering

home agentcorrespondent host

Correspondent, home agent onsame network. Packet from mobile host is deemed "topologically incorrect"

• Routers which see packets coming from a direction from which they would not have routed the source address are dropped (external domain)

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Reverse Tunneling

InternetHA

FAMH

CN

COAHome

Network

Pro: Firewall and Ingress Filtering problems removed

Con: Lengthy Routing Path (double triangular), increase in congestion

MH cannot make a tunnel directly to CN

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Route Optimization Messages

Binding warning

Binding update

Binding request

Binding Acknowledgement

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Problems with MIPv4

Authentication with FA is difficult as it belongs to another organization Guaranteeing QoS to a flow of packets is difficult because of

triangulation and tunneling. Triangular routing and frequent handoffs cause significant end-to-end

delay (Micro-mobility helps a bit) High signaling load on HA if mobile node moves frequently. To support Global mobility, all routers should have FA and HA

functionality (solved with a reduced scope in Macro-mobility). For some applications, it may be important to track the location of

mobile nodes : causes huge power and signaling load. Paging (the maintenance of information when the node is idle) is not

supported by MIP. (Paging is a procedure that allows a wireless system to search for an idle mobile host when there is a message destined to it, such that the mobile user does not need to register its precise location to the system whenever it moves)

User perceptions of Internet reliability. If FQDN of the Mobile node has many IP addresses, which one to

choose?

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Hierarchical Mobile IP (HMIP)

InternetLocalizing Registrations

HA

FA1

FA2FA3

FA4

FA5FA6

MH@FA1

MH@FA2

MH@FA4

MH@VL

Lineage <FA4, FA2, FA1>

<FA5 FA2, FA1>

<FA6, FA3, FA1>

MH@FA5

Common ancestor = FA2 (nearest)

Common ancestor = FA1

(nearest)

MH@FA3

MH@FA6

MH@VL

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Mobility using Session Initiation Protocol (SIP)

A Signaling Protocol Originally used for negotiating media sessions

between end systems Media may go through different networks Other uses: Conferencing, VoIP, Instant

Messaging etc. Elements (SIP user agent, Servers, and

Gateways) Addressing (URLs) e.g. name@domain and

supports both Internet and PSTN address

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SIP Session Setup Example

200 OK

ACK

INVITE sip:abc@uunet.com

host.wcom.com sip.uunet.com

SIPUser Agent

Client

SIPUser Agent

Server

BYE

200 OK

Media Stream

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SIP Proxy Server Example

server.aol.com

200 OK

BYE

200 OK

INVITE sip:abc@aol.com

host.aol.com

200 OK

ACK

INVITE sip:abc@uunet.com

sip.uunet.com

Media Stream

SIPUser Agent

Client

SIPUser

AgentServer

SIPProxyServer

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SIP Redirect Server Example

302 Moved sip:abc@uunet.com

ACK

Media Stream

INVITE sip:abc@aol.com

180 Ringing

ACK

INVITE sip:abc@uunet.com

REGISTER abc@uunet.com

host.aol.com

200 OK

server.aol.com

200 OK

SIPUser Agent

Client

SIPRedirectServer

SIPUser Agent

Server

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Mobility using SIP

SIP RedirectServer

SIP ProxyServerForeign

Network

MobileHost

HomeNetwork

CorrespondingHost

1 23

6

4

5

1 INVITE

2 302 moved temporarily

3, 4 INVITE

5, 6 OK

7 Data

Benefits: Global mobility, No tunneling, No change to routing

7

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Cellular IP

Cellular IP represents a new mobile host protocol

simple, and flexible protocol for highly mobile hosts

CIP supports local mobility & efficiently internet works with Mobile IP

CIP Gateway

Internet

BS

MN1

data/controlpacketsfrom MN 1

Mobile IP

BSBS

MN2

packets fromMN2 to MN 1

•A gateway (GW) acts as foreign agent for each domain (all MNs use GW address as COA)

• Within the domain: host-based routing

• routing cache entries using soft-state

• routing cache updated by upstream packets

• separate paging cache for in-active nodes

routers within domain have to be CIP aware

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Wireless Access network Model

MH

B

DInternet with

Mobile IP

R

R

A

CE

F

G

Home agent of MH

Gateway

Beacon signal

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Packets will be first routed to the host's home agent and then tunneled to

the gateway

The gateway "detunnels'' packets and forwards them toward base stations

Packets transmitted by mobile hosts are first routed to the gateway and

from there on to the Internet

MOBILE IP

CELLULAR IP

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Cellular IP Paging

Idle mobile hosts that receive a packet move from idle to active state, start their active-state-timer and immediately transmit a route-update packet.

This ensures that routing cache mappings are established quickly

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Mobile host state machine

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Efficient Location Management

Two parallel structures of mappings (PC &RC)

1 - idle MH keeps PC upto-date

2 - PC mappings used to find the loc of idle MH

3 - maintains RC mappings until actively connected

4 - routing of data packets to MH

X XX

PC RC

Service Area

Mobile Host1 2 3 4

PAGING &ROUTING

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Illustration of Paging

MHB

D

RA

CE

F

G

Internet withMobile IPGW X

Paging-update packets create mappings in PCs

X : from GX : from C

Paging-update

I don’thave a PC

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PCs updated for a moving host

X : from GX : from C

B

D

RA

CE

F

G

Internet withMobile IPGW X

X : from F

X : from F,G

G times out

MH

No change in PC at A

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B

D

RA

CE

F

G

Internet withMobile IPGW

MHX

Paging packets are routed to the mobile host by PCs

X

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Handoff

X : from D

X : from D, E

X : from E

X : from C

E

B

D

RA

C

F

G

Internet withMobile IPGW X

X : from F

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Paging & Routing caches

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Handoff

Cellular IP handoffHard handoffSemi-soft handoff

Hard handoffDuring the Handoff Latency the downlink packets are

lost. Semi-soft handoff

Improvement over Hard Handoff

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Hard-Handoff

2.MN send Route Update Packet to GW

3.BSs are refresh RS

4.GW send data packets to MN

1.MN From Old BS toNew BS

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Semi soft-Handoff

Improvement over Hard Handoff ; NO packet loss & smooth handoff.

Need for buffering at the cross over point :For smooth handoff

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Compare Mobile IP & Cellular IP

Location management Mobile IP: Care-of-address Cellular IP: paging update packet

Routing Mobile IP: registration Cellular IP: routing cache

Handoff Mobile IP: encapsulation, triangle routing Cellular IP: routing cache

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22.10.2007

Handoff-Aware Wireless Access Internet Infrastructure (HAWAII)

Internet

Home domain root router

IP tunnel

Foreign domain root router

CN

AP

AP

MHRouter at Level1

Router at Level1

DHCP Server

1

Co-located COA

2

Registering with HA

3

45

New AP answers reg. req

AP Updates routers

IP Routing

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What is HIP?

HIP = Host Identity Protocol A proposal to separate identifier from locator at the network

layer of the TCP/IP stack A new name space of public keys A protocol for discovering and authenticating bindings between

public keys and IP addresses

Secured using signatures and keyed hashes

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A new Name Space of Host Identifiers (HI) Public crypto keys! Presented as 128-bit long

hash values, Host ID Tags (HIT)

Sockets bound to HIs, not to IP addresses

HIs translated to IP addresses in the kernel

The Idea

IP addr

ProcessProcessProcessProcess

TransportTransportTransportTransport

IP layerIP layerIP layerIP layer

Link layerLink layerLink layerLink layer

IP address

< , port>

Host Host IdentityIdentityHost Host

IdentityIdentityHost ID

Host ID

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IP layerIP layerIP layerIP layer

FragmentationFragmentation

More detailed layering

Link LayerLink LayerLink LayerLink Layer

ForwardingForwardingForwardingForwarding

IPsecIPsec

Transport LayerTransport LayerTransport LayerTransport LayerEnd-to-end, HITs

Hop-by-hop, IP addresses

HIPHIP

MobilityMobilityMobilityMobility

Multi-Multi-hominghomingMulti-Multi-hominghoming

v4/v6 bridgev4/v6 bridgev4/v6 bridgev4/v6 bridge

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Protocol overview

Initiator Responder

I1: HITI, HIT

R

R1: HITI, [HIT

R, puzzle, DH

R, HI

R]sig

I2: [HITI, HIT

R, solution, DH

I, {HI

I}]

sigR2: [HIT

I, HIT

R, authenticator]

sigUser data messagesUser data messages

Con

trol

Con

trol

Dat

aD

ata

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How applications work today(when IPsec is used)

IKE IKEIKE

Server appServer app

socket APIsocket API socket APIsocket API

IPsecSADIPsecSAD

IPsecSPDIPsecSPD

IPsecSPDIPsecSPD

IPsecSADIPsecSAD

connect(IPS

)

TCP SYN to IP

S

DNS query

ESP protected TCP SYNto IPaddr

S

TCP SYN from IP

C

DNS serverDNS serverDNS reply

Client appClient appIP

DNS libraryDNS library

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Using HIP with ESP

HIP daemon HIP daemonHIP daemon

Server appServer app

socket APIsocket API socket APIsocket API

IPsecSADIPsecSAD

IPsecSPDIPsecSPD

IPsecSPDIPsecSPD

IPsecSADIPsecSAD

TCP SYN to HIT

S

DNS query

ESP protected TCP SYNto IPaddr

S

convert HITs to IP addresses convert IP addresses to HITs

TCP SYN from HIT

C

DNS serverDNS serverDNS reply

Client appClient appHIT

DNS libraryDNS library

HIT ----- >  {IP addresses}connect(HIT

S)

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IPsec Definations

Security policy database (SPD) Security association database (SAD) Encapsulating security payload (ESP)

54/55

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HIP as the new waist of TCP/IP

v4 app

TCPv4

IPv4

Link layer

TCPv6

IPv6

v6 app v4 app

TCPv4

IPv4

Link layer

TCPv6

IPv6

v6 app

Host identity Host identity

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Introduction to IP based mobility and multi-homing Mobility implemented at “lP layer” IP addresses are assigned according to topology

Allows for routing prefix aggregation Mobile hosts change their topological location Multi-homed hosts present at many locations In an IP based m&m solution

Transport & apps do not see address changes or multiple addresses

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Mobility and multi-homing become duals of each other Mobile host has many addresses over time Multi-homed host has many addresses at the same time

Leads to a Virtual Interface Model A host may have real and virtual interfaces Merges the “Home Agent”

HIP Mobility & Multi-homing

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ESP from MN to CNESP from MN to CNESP from MN to CNESP from MN to CN

Mobility protocol

Mobile Corresponding

UPDATE: HITs, new locator(s), sig

UPDATE: HITs, RR challenge, sig

ESP on both directionsESP on both directionsESP on both directionsESP on both directions

UPDATE: HITs, RR response, sig

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Multicast and IP-Mobility Common issues in both paradigms

Location independent communication/addressing Location discovery/management Packet forwarding

Location Independent Addressing

• IP-Multicast– Single ‘logical’ multicast group

D-class address– Senders do not know receivers– Receivers do not know senders

• Mobile-IP– Permanent home address– Temp care-of-address(es)– Address mapping done

through the home agent

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Location Management

IP-Multicast Membership location Done thru IGMP & routing Meet through the multicast tree

Mobile-IP Mobile node location Done thru home agent Meet thru registration of

new address

Packet Forwarding

• IP-Multicast– Multicast forwarding– Tunnel through the multicast

tree (e.g., RP)

• Mobile-IP– Unicast forwarding– Tunnel through home agent

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Multicast for Mobility? Instead of obtaining a new COA and registering with the new

foreign agent (and subsequently with the home agent) and de-registering the old address

Use the same logical multicast group address and join/leave the group as you move

Potential Advantages• Avoiding ‘triangle routing’ problem

• Avoiding the need for home/foreign agents to continuously tunnel packets to the MN

• Smooth hand-off using standard join/prune

• Using shortest path (source-specific trees)

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CN

Wireless link

Mobile Node

CN

CN

CN

(a) (b) (c) (d)

(a) All locations visited by the mobile are part of the distribution tree (at some point)

(b) When a mobile moves to a certain location, only that location becomes part of the tree (shown by bold lines)

- When the mobile moves to a new location, as in (c) and (d) the distribution tree changes to deliver packets to the new location.

Multicast-based Mobility (M&M): Architectural Concept

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Distribution tree dynamics while roaming

CNCN: Correspondent node (sender)

Wireless link

Mobile Node

Multicast-based Mobility (M&M): Architectural Concept

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Join/Prune dynamics to modify distribution

CNCN: Correspondent node (sender)

Wireless link

Mobile Node

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Smooth Hand-off

BS1 BS2

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Obtaining MN’s multicast address

A corresponding node (CN) obtains the multicast address of the MN through: DNS lookup

similar to getting the unicast (home) address of the MN

requires update of DNS after allocation of multicast addresses to MNs

Startup phase

CN sends packets to home addressHome agent encapsulates packets in multicast

packets sent to the MNMN decapsulates these packets and sends a binding

update to the CN with its multicast address

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multicast

Startup scenario

Correspondent NodeMobile Node

• On first move, the mobile node (MN) sends a binding update to the CN

Mobile Node

JoinHome Agent (HA)

Home Network

Join

Binding Update (MN’s multicast address)