77232345 cours-ip-mobile

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Mobilité IP

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Plan• Introduction

– Qu’est-ce que la mobilité IP ?• Architecture Mobile IP• Mécanismes de mobilité IP

– Découverte d’agent– Enregistrement– Tunnelage

• Fonctionnalités avancées• Micro-mobilité• Support de mobilité fourni par IPv6• Mobile IP & 3G• Conclusion

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Différents types de mobilité

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• Nomadisme (DHCP)

• Ordinateurs mobiles (Mobile IP, IEEE 802.11)

• Réseaux mobiles (réseaux Ad-hoc)

• Besoin de protocoles fournissant un service de localisation

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Mobilité IP ≠ LANs sans fil (WLAN)

• LANs sans fil aujourd’hui :

– IEEE 802.11, Bluetooth …

– AP IEEE 802.11 AP = pont entre

le réseau fixe et le réseau sans fil

• handoffs de niveau 2 supportés mais PAS la

mobilité IP (les handoffs sont supportés au sein d’un même sous-réseau IP)

• Mobilité IP ≠ Interface sans fil

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Mobilité IP ≠ LANs sans fil (WLAN)

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Différents types de mobilité•Terminal Mobility

- Wireless connection between a terminal and access point (base station) or between several terminals(ad hoc network)

- Keeps registration/call between customer and network while in motion- Enabling fonctions: handover, paging

•Personal Mobility- Enables a customer to be identifiable regardless of the terminal, the terminal type, the operator/provider domain, and the type of network he is currently registered with

- User profiles are available across terminal/network/operator boundaries

- Number portability

•Service Mobility - Enables usage of tailored and personalized services even if the customer is roaming to foreign networks

- Includes service portability

•Session Mobility - Allows to interrupt sessions and to resume them later, possibility from another terminal or another network

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Mobilité

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Introduction Mobile IP (1)

• Sillage des réseaux GSM– Mobilité = nécessité pour les utilisateurs

d’un système de communication– Tous les réseaux existants se donnent

pour mission de proposer ce service• Standard TCP/IP : réseau le + étendu au monde

– Principe Anywhere, Any Time, Network Access

– Réseau IP : l’une des principales sources d’information

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Introduction Mobile IP (2)

• Échelle planétaire :– Quasi-totalité des réseaux fournissent une entrée au réseau Internet– Avec mobilité : garantie d’un accès universel, simple d’emploi et pratique

• Groupe de travail de l’IETF : proposition IP Mobile

– Proposer une localisation planétaire par l’adresse IP (à l’instar du roaming du GSM)

• IP préexiste au concept nomade– GSM doté dès l’origine de telles fonctions– IP : « bricolage » de solutions pour ajouter la mobilité

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Cahier des charges pour l’architecture de mobilité IP

• Two major requirements arise when considering IP mobility:– Application transparency : Dealing with a mobile

configuration should not necessitate a mobile-aware application. This is needed in order to avoid application replacement on all Internet hosts!

– Seamless roaming : When a user goes out of his corporate network and roams around in the Internet, the requirement is to assure a seamless Internet communication

between this user and his correspondents whatever the access network used by the mobile roaming user

• Dealing with mobility at the IP layer provides a way to answer the above requirements

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Problématique de la mobilité dans IP

• Difficultés pour intégrer à IP de nouvelles fonctions devant offrir la mobilité

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Why isn’t IP mobility simple? (1)

• The complexity comes from the current use of IP addresses.• An IP address is used to – identify a particular end-system. In this respect, IP addresses are equivalent to FQDNs (Fully Qualified Domain Names) and the equivalence is maintained in a DNS, Domain Name Server – identify a particular TCP session in an IP host since a TCP socket consists of a (destination IP address, destination port number) couple – determine a route to a destination IP host.• The first two uses come into contradiction with the third usewhen mobility is considered

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IP mobility: routing

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• The first use supposes that a host’s IP address should never change since the DNS should always point to the same IP address• The second use supposes that a host’s IP address should never change during a TCP session otherwise the session would be lost• The third use supposes that when the host is roaming outside its home network (the network which has the prefix of the host’s IP address), it should change its address (and take an address with a prefix given by the visited network) in order to receive the datagrams destined to it

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• A possible answer to the third constraint would be to use a DHCP (Dynamic Host Configuration Protocol) server in order to obtain an address on the visited network

• This however poses a problem with the first two constraints

– First, the IP address of a host having changed, the DNS in the home network should be updated by the mobile host on the visited network. This may be very dangerous on a security standpoint! – Second, this solution can not provide a seamless continuous mobility capability since when the mobile host’s IP address is changed, all TCP sessions involving this host should be dropped and reinitialized with the new IP address

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Mobile IP standardization process

• The standardization of Mobile IP is being mainly carried out at the IETF (Internet Engineering Task Force)• The IP Routing for Wireless/Mobile Hosts (MobileIP) WorkingGroup is in charge of defining and specifying the Mobile IParchitecture and protocols• The major architecture components are already in the standardstrack (Request For Comments, RFCs 2002-2006)• Some very interesting enhanced functionalities are still considered as work in progress and specified in Internet Drafts• These documents and other related information may be found at the mobileip WG home page on the Web :http://www.ietf.org/html.charters/mobileip-charter.html

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PLAN

• Introduction– Qu’est-ce que la mobilité IP ?• Architecture Mobile IP• Mécanismes de mobilité IP– Découverte d’agent– Enregistrement– Tunnelage• Fonctionnalités avancées• Micro-mobilité• Support de mobilité fourni par IPv6• Mobile IP & 3G• Conclusion

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Overview of the IP mobility architecture

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Functional entities

• Mobile node : A host or a router that roams from onenetwork or subnetwork to another outside its home networkwithout changing its long term IP address (the home address)• Home agent : This is typically a router on a mobile node’shome network which delivers datagrams to departed mobilenodes, and maintains current location information for each• Foreign agent : This is typically a router on a mobile node’svisited network that collaborates with the Home agent tocomplete the delivery of datagrams to the mobile node whileit is away from home

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The Mobile IP basic concept

The Mobile IP basic concept The Mobile IP basic concept• The Mobile IP architecture resolves the above contradictionby using 2 IP addresses for a mobile host :– The Home address is a permanent address used toidentify uniquely the IP host on the Internet (answers thetwo first IP addresses constraints)– The Care-of address is a temporary address used toroute the datagrams destined to the mobile host to thecurrent attachment point of this host (answers the last IPaddresses constraint)

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Plan


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Main Functions• Agent Discovery :– Home Agents & Foreign Agents send advertisements on thelink. A mobile can ask for advertisements to be sent.• Registration :– When a mobile is away, it registers its temporary addresswith its home agent• Tunneling :– The packets for the mobile are intercepted by the HA andtunnelled to the mobile

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Mobile IP

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Protocol overview

1. Home Agent & Foreign Agent broadcast or multicastagent advertisements on their respective links.2. Mobile nodes listen to Agent Advertisements. Theyexamine the contents of these advertisements todetermine whether they are on the home or on avisited network3. A mobile node on a visited network acquires atemporary address (care of address)

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Protocol overview

4. The mobile registers its COA with its home agent5. The Home Agent sends ARP on the Home Network(IP@ <-> MAC@). The packets for the mobile areintercepted and sent to the current position of themobile6. The packets arrive to the COA and are decapsulated inorder to extract the original packet7. The packets from the mobile are sent directly to thecorrespondents

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IP mobility mechanisms

Agent discovery

Registration

Tunneling

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Agent Discovery

• Process by which the mobile detects where it is attached(home or visited network)• Allows the mobile to determine a COA when the mobile is on avisited network• Based on 2 types of messages:– Agent Advertisement : broadcast or multicast by the agents– Agent Solicitation : sent by a mobile which does not want towait for an AA• Message authentication

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Agent Solicitation Message

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Mobile Agent Discovery

• An extension, called the Mobility Agent extension, isappended to ICMP Router Advertisement to constitute theAgent Advertisement message• A Foreign Agent uses the Agent Advertisement message in orderto indicate the Care-of Address to a Mobile Node• A Home Agent uses the Agent Advertisement message so that aMobile Node knows when it has returned to its HomeNetwork• A Mobile Node is allowed to send ICMP Router Solicitationmessages in order to elicit a Mobility Agent Advertisement

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Mobile Agent DiscoveryGetting a COA

• A Care-of Address may be obtained from the Foreign Agent byan Agent Advertisement.– It may also be obtained from a RAS (Remote Access Server)implementing PPP or from a DHCP server on a foreign LAN.– In this case the Care-of Address is said to be collocatedsince it is directly assigned to the Mobile Node interface andnot to a Mobile Node through a Foreign Agent.• For a collocated Care-of Address, the tunnel terminates at theMobile Node interface

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Agent Advertisement Message

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Mobile Agent Discovery

• It is based upon an extension of the ICMP (InternetControl Message Protocol) Router Discovery protocol• A router periodically broadcasts ICMP RouterAdvertisement messages on the different directlyattached subnetworks• This allows the hosts on these subnets to discover therouter

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Mobile Agent DiscoveryMobility Agent Advertisement Extension

• Flags:– R=Registration required at the Foreign Agent– B=Busy– H=Home Agent– F=Foreign Agent– M,G,V indicate the encapsulation type• Type identifies the Mobility Agent Advertisement extension• Length is the total length of this extension which depends on the numberof Care-of Addresses• Lifetime specifies the duration of the Care-of Address support on theForeign Agent• For a Home Agent, Zero Care-of Address is advertised• For a Foreign Agent, typically one Care-of Address is advertised• Sequence Number is incremented at each Advertisement

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Registration

• Functionnalities– Ask for routing functionnalities of the FA– Tell the HA the new location of the mobile– Update a binding which is about to expire– De-register the mobile when it is back on its home network• Triggered as soon as the mobile detects it changed its point ofattachement• Use of the information obtained by agent discovery to determine thetype of registration to be done• Two registration procedures– With the«ForeignAgent»– With the temporary address of the mobile

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Registration

• Once the Mobile Node receives a Care-of Address, it shouldregister its (Home Address, Care-of Address) binding athis Home Agent• This is done using 2 messages :– Registration Request– Registration Reply• They both use a UDP/IP service

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Registration

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Registrationrequest

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Registration

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RegistrationRegistration Request

• Flags :– S=Simultaneous Registrations (multiple Care-of Adresses)

– B=Broadcast– D=Care-of Address collocated with the Mobile Node

– M,G,V indicate the encapsulation type• Type identifies the Registration message

• Lifetime specifies the duration of the mobility addresses binding• Home Address is bound to the Care-of Address

• Home Agent identifies the Home Agent that should register thebinding

• Identification is used to protect against replay attacks and allows tocorrelate a Registration Request with a Registration Reply message• The Mobile-Home authentication extension is used to authenticate

the Mobile Node at the Home Agent

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Registration Reply

• Registering with the FA– The FA receives the message and may reject it:

• Invalid authentication• The lifetime value exceeds what may be accepted by the FA

• The mobile wishes to use a tunneling type not supported by theFA

• The FA has not enough resources– Otherwise, it forwards the request to the HA

• Registering with the HA– The HA also checks the registration should be accepted (same

conditions)– If it is accepted, the HA• Updates its binding table

• Sends a proxy ARP message on the local link

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RegistrationRegistration Reply

• Type identifies the Registration message• Lifetime specifies the duration of the mobility addresses binding

• Home Address identifies the Mobile Node to which this message isrelated

• Home Agent identifies the Home Agent having registered thebinding

• Identification is used to protect against replay attacks and allows tocorrelate a Registration Request with a Registration Reply message• The Mobile-Home authentication extension is used to authenticate

the Home Agent at the Mobile Node• Code gives the result of the registration

– 0 : registration accepted– 66, 69, 70... : registration denied by the Foreign Agent

– 130, 131, 133... : registration denied by the Home Agent

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Registration Reply

• The FA receives a registration reply– If the RR is invalid, the agent sends a Registration

Reply describing the reasonwhy the registration was rejected

– Otherwise, theagent• Updates its binding table

• Forwards the message to the mobile• Starts to handle the messages for the mobile

• Reception of the RR by the mobile– If the registration was rejected, the mobile tries to

change its registrationprocedure

– Otherwise the mobile updates its routing table

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Registration Reply

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Registration Reply

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Registration

• Via le Foreign Agent :

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Exemple

• Adresse home du mobile node =129.34.78.5

• HA du mobile node = 129.34.78.254

• FA address = 137.0.0.11

• FA care of address = 9.2.20.11

• Home node source port = 434

• Mobile node source port = 1094

• FA source port = 1105

• Care-of-address registration lifetime = 60000 s

• HA granted lifetime = 35000 s

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Exemple

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Exemple

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Exemple

Annuler l’enregistrement (au retour au réseau home) :

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Exemple

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De-registration

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Discovering the HA's address

• Manual configuration on the mobile

• Automatically

– By broadcasting a registration request

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Learning the HA address

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Movement detection

• Using the lifetime field

– If the lifetimeexpires, the mobile supposes it has attached

to a new link or the agent has failed. It waits for an Agent

Advertisement or sends an Agent Sollicitation

• Detection using the network prefix

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Routing

• To the home network– The packets for a mobile are always sent to its home

network– No specific routing –conventional routing

– If the mobile sends data, it behaves as any other node onthe Internet

• To a visitednetwork– A router on the local link broadcasts an ARP request to

inform the packets for the mobile should be sent to it.– The packets are intercepted by the HA and tunnelled to

the mobile's COA(s)– At the end of the tunnel, they are decapsulated and

delivered to the mobile

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Interception by the HA

• 2 possibilities

– Accessibility advertisement :

only on HA routers with several interfaces

– Using the proxy ARP

Mobile's IP@ <-> HA's MAC@

Updated by the HA and by the mobile node when it returns on its

home network

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Packet interceptionby the HA

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Home Network configurations

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Proxy and Gratuitous ARP Proxy

• In the cases A and B above, the Home Agent should intercept thedatagrams intended to Mobile Nodes using a Proxy ARP

mechanism• In the case C, all datagrams intended to Mobile nodes will benaturally intercepted by the Home Agent. Here, all the hosts areoutside their Home Network which become a Virtual Network

• Gratuitous ARP should be used by the Home Agent in order tochange the ARP cache entry for a roaming Mobile node’s Home

Address on the Home Network• When the Mobile Node gets back to its Home Network, GratuitousARP should again be used by the Mobile Node itself to restore the

ARP cache entry

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Security aspects (1)

• The security issue is fundamental for registration messages otherwiseimpersonation and session hijacking attacks would be trivial

• Authentication should be applied to these messages• The Mobile IP architecture specifies its own security mechanisms for use

with IPv4 since IPsec, the new standardized security architecture, is notmandatory with IPv4

• An authentication extension is thus appended to each of the abovemessages

• The default authentication algorithm is a keyed-MD5 in prefix + suffixmode

• The result of the authentication is thus a 128 bit message digesttransmitted in the authentication extension

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Security aspects (2)

• Type identifies the authentication extension (Mobile-Home, Home Agent-Foreign Agent,...)• SPI specifies the authentication context (algorithm, mode, key...)• The Authenticator is calculated over the entire message + this authenticationextension

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Firewalls and packet filtering problems (1)

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• Ingress filtering is often applied in the border gateway of acorporate network playing the role of a firewall

• This prevents Mobile Node generated datagrams to reach theInternet coming from the Visited Network

• Solutions– Send datagrams with Source Address=Care-of Address this

is a loosing proposition because it runs counter to thearchitecture

– Send datagrams encapsulated in an outer IP header withSource Address=Care-of Address this is a better

proposition but the Correspondent Nodes are not required tobe able to do the decapsulation Encapsulated datagrams

may be sent to the Home Agent which sends them back to theCorrespondent Node this is a suboptimal solution on the

routing standpoint

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• Correlated problem : the firewall on the Home Networkside should also filter all datagrams coming from the Internet

with a Source Address corresponding to an inner address(with the same prefix as the Home Network)

• Solutions :– If the Home Agent is collocated with the Gateway/Firewall,

the firewall will know when such datagrams should beaccepted

– Otherwise, a protocol between the Home Agent and theFirewall may be necessary

– Finally, a solution may consist in tunneling all such datagramsto the Home Agent which should play the role of a bastion

host and be attached to a DMZ for safety

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Datagram Tunneling

• A Correspondent Node sends datagrams to a Mobile Node withthe Destination Address field containing the Mobile Node’s Home

Address• Based on the destination address, these datagrams reach the

Home Network• There, the Home Agent intercepts the datagrams and

encapsulates them into an outer IP header that tunnels theinitial datagrams to the Foreign Agent or directly to the Mobile

Node (in the case of a collocated Care-of Address)• Multiple encapsulation schemes may be used including :

– IP-within-IP encapsulation– Minimal encapsulation

• The datagrams sent by the Mobile Node reach directly theCorrespondent Node

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Reminder : IPv4 header format

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IP-within-IP encapsulation

• The original IP header remains unchanged when transmitted inthe tunnel (the TTL field is decremented)– Source Address : Correspondent Node Address– Destination Address : Mobile Node’s Home Address• The new IP header has :– Source Address : Home Agent Address– Destination Address : Care-of Address• When fragmentation is needed, it should be done at the inner IPdatagram level otherwise the fragments won’t transport the MobileNode’s Home Address used at the Foreign Agent to send thedecapsulated datagram on the right data link

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Minimal encapsulation

• S indicates the presence of the Original Source Address field• Minimal encapsulation limits the number of supplementarybytes necessary for tunneling• It prevents however from performing fragmentation

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Soft Tunnel State

• It is interesting to maintain at the Home Agent level (the entry point

of the tunnel) a number of parameters on the state of eachestablished tunnel.

• These parameters constitute the Soft Tunnel State and include :– The Path MTU on this tunnel for fragmentation purposes

– The state of the tunnel (broken or not)– The Correspondent Node using the tunnel

• The Home Agent may then relay ICMP error messages to theCorrespondent Node source of the tunneled datagrams

• Typically, ICMP host unreachable messages are sent back to the

Correspondent Node when the datagrams are not delivered through

the tunnel

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Plan


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Enhanced functionnalities

• Optimisation du routage

• Smooth handoff

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Routing optimisation

• Goal : Avoid triangle routing

• Idea:

– Tell the correspondents the current position of the mobile

node

• Problem:

– Change the correspondent's IP stack

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Triangle Routing

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Route optimization (1)

• The basic Mobile IP mechanisms create a Triangle Routingbetween the Correspondent Node, the Home Agent and the

Mobile Node.• This Triangle Routing is far from being optimal especially in

the case of a Correspondent Node very close to the MobileNode

• Route optimization consists of eliminating this problem• This is done by updating the Correspondent Node giving it the

mobility binding (Home Address, Care-of Address) of theMobile Node

• For security purposes, it is the responsibility of the HomeAgent to send the mobility binding to the Correspondent

Nodes that need them

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Correspondent Node

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• Binding updates are authenticated by a route optimization

authentication extension (same as for the Mobile-Home

authentication extension)• Route optimization offers an efficient routing technique

butsupposes that the Correspondent Nodes are able to

implement the route optimization protocol• This may be the main reason why this mechanism has

not yetbeen definitively adopted as an RFC

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Foreign Agent - Smooth Handoff

• When a mobile moves, it registers with a new FA• Goal: Tell the old FA the current position so that thepackets in transit are redirected to the mobile (avoid

losses and retransmissions)• Protocol:

– The mobile registers with the new FA and tells the address of its

old FA– The new FA sends a BU to the old FA so that it

forwards thepackets to the new location of the mobile

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Smooth Handoff(1)

Correspondent Node

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Smooth Handoff(2)

• During the handoff, it is important that the datagrams intended to theMobile Node and received by the previous Foreign Agent not be lost• A smooth handoff may be obtained if the previous Foreign Agent

receives a binding update with the new Care-of Address of the MobileNode allowing it to relay the datagrams to the new Foreign Agent

• This is best achieved if it remains a local mechanism between theMobile Node and both the current and previous Foreign Agents (the

Home Agent is too far to perform this binding update)• This poses however a security problem since it is highly improbable,in the current state of Internet security, that an authentication securityassociation be established between the Mobile Node and the Foreign

Agents

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Smooth Handoff(3)

Correspondent Node

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Smooth Handoff(4)

• If the previous Foreign Agent does not hold the new mobility bindingfor the Mobile Node, it may send back the decapsulated datagram

to the Home Agent.• This may create routing loops if the Foreign Agent has lost the traceof the Mobile Node and the Mobile Node is not connected elsewhere

• The Foreign Agent should re-encapsulate the decapsulateddatagram into a Special Tunnel getting it back to the Home Agentwith the Care-of Address as the source address of the outer header

• This allows the Home Agent to compare the current registration withthe returned Care-of Address and decide whether it should tunnel the

datagram or not thus avoiding routing loops

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Plan

• Introduction– Qu’est-ce que la mobilité IP ?

• Architecture Mobile IP• Mécanismes de mobilité IP

– Découverte d’agent– Enregistrement

– Tunnelage• Fonctionnalités avancées

• Micro-mobilité• Support de mobilité fourni par IPv6

• Mobile IP & 3G• Conclusion

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Micro mobility: Différents types de mobilité

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Micro mobility

• A mobile has to register with its HA every

time it moves

– Macro mobility (Mobile IP)

– Micro Mobility (Hawaii, Cellular IP …)

• Smaller cells + more mobiles => need to ditinguish

micro/macro mobility

• The mobile registers with the HA when it

moves to a new mciro mobility domain

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Micro mobility IP

• Fonctionnement en mode paquet– Différence par rapport aux autres réseaux cellulaires publics

– GSM, UMTS, CDMA 2000 : interfaces radio majoritairement enmode circuit

• Universalité du protocole IP– Infrastructures répandues dans le monde entier

• Micromobilité : va devenir une donnée primordiale des réseaux• Protocole de micro mobilité = complémentaire d'IP mobile

– Macromobilité : possibilité pour un utilisateur de quitter son réseaud'abonnement pour se rendre dans un autre domaine du réseau IP

• Adresse temporaire dans le nouveau domaine• Enregistrement auprès de l'agent local de sa zone

d'abonnement• Génération d'un temps de latence

– Échange de nombreux messages de signalisation– Micro mobilité : mobilité locale

• Transparente pour le réseau d'abonnement de l'utilisateurmobile

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Micro mobility

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Macro / Micro mobility

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Solutions de micro mobilité

• Enregistrements régionaux

HMIP

• Cellular IP

• Hawaii

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Regionalized registration (1)

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Regionalized registration (2)

• Regionalized registration is a solution to the reduction of theregistration traffic between a Home and a Visited Network over theInternet in order to update the mobility binding of the Mobile Nodes• The idea is to construct a hierarchy of Foreign Agents, each FA

registering a Care-of Address for the Mobile Node at its father FA level• Multiple successive tunnels are thus constructed to reach the Mobile

Node from the Home Agent• When a Mobile Node moves from the region of FA7 to FA8, a registrationshould only be sent to FA4 and the tunnel FA4FA7 would be replaced by

a tunnel FA4FA8• When a Mobile Node moves from the region of FA7 to FA9, a registrationshould be sent to FA1 (and not to the Home Agent) and the tunnels would

be replaced accordingly

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• HMIP

• Cellular IP

• Hawaii

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HMIP: Hierarchical Mobile IP

• Problem: a mobile

registers with its HA

every time it moves

• Goal: reduce

registration time by

using regional

registrations

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HMIP: Registration(1)

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HMIP: Registration(2)

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HMIP: Routing

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HMIP: Ericsson(1)• Several levels in the

hierarchy• FA sends advertisements@FA7,@FA3,@FA1@GFA

(pour FA7)@FA6,@FA4,@FA2,@GF

A (pour FA6)• The MN registers the

GFA@with its HA

• IP tunnels are set upbetween the FAs

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HMIP: Ericsson(2)• When it moves, the mobile

checks the routes todetermine if it is in the

same hierarchy@FA7,@FA3,@FA1@GFA

(for FA7)@FA6,@FA4,@FA2,@GFA (for FA6)

• Fast handoffs : a mobilemay register with several

FAs• The packets are bicasted by

the GFA

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HMIP

• Cellular IP

• Hawaii

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IP cellulaire:Couplage IP Mobile / IP cellulaire

• IP cellulaire n'intervient que sur le réseau d'accès– Aucun routeur du réseau de cœur n'a conscience de l'existence d'IP

cellulaire– Système peu coûteux à l'installation car pas de modification pour

les routeurs• Fonctionnement simple

– Définition d'une passerelle ou GW (Gateway)• Accès au réseau Internet

• Située à la racine du domaine : joue le rôle d'agent étranger• Possède une adresse IP qui sert de COA (Care-Of Address) à

tous les visiteurs du domaine• À la réception de paquets encapsulées, la GW ôte l'en-tête

additionnel• IP cellulaire met en œuvre des techniques qui lui sont propres

pour transférer le paquet vers le mobile adéquat– Grâce aux adresses IP permanentes

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Cellular IP:principes

• Caches distribués

– Position des mobiles

– Information de routage

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IP cellulaire

• Base Stations– Wireless Access Points

– IP routing replaced by Cellular IP routing• Gateways

– Mobile IP support– Mobile Nodes use the GW@ as COA

• Mobile Node– Inside the Cellular IP network, mobile nodes

areidentified with their home address

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Architecture IP cellulaire

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• Réseau d'accès contient des stations de base– Couverture de microcellules (id GSM)

– Couverture de picocellules, desservies par de petitesantennes dans des espaces privatifs

• Souplesse de fonctionnement grâce à IP– Méthode de transmission sur l'interface radio indépendantedes opérations liées au routage et à la gestion de la mobilité

• Détection du passage d'une cellule à une autre– Diffusion périodique d'une signature de chaque station de

base : voie balise– Signal pilote servant à mesurer la puissance du signal radio

émis par chaque station de base• Stations de base câblées de manière hiérarchique

– Sommet = racine du domaine = passerelle

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Opérations dans le réseau

Opérations dans le réseau

• 3 opérations principales– Paging

• Localisation d'un utilisateur lors de l'arrivée de paquets àdestination– Routage

• Acheminement des paquets vers l'utilisateurs à travers lesprincipaux éléments du réseau d'accès

– Handoff• Gestion des déplacements de l'utilisateur via le réseau d'accès

• IP cellulaire se comporte comme un système sans fil– Les terminaux choisissent toujours la station de base qui diffuse le

signal pilote le plus puissant– Handoff : changement de station de base

– Mise à jour de tous les RC lorsque la route est nouvelle

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Objectifs de Cellular IP

• Migration facile

• Bonne connectivité

• Support du soft handoff

• Passage à l’échelle avec une complexité minimale

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Cellular IP

• Réseau distribué

• Les noeuds ne connaissent pas la topologie

• Pas de base de données centralisée

• Bon passage à l’échelle

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Cellular IP

• Cellular IP nodes do not know the exact location of a

mobile

• Hop by hop routing

• IP addresses are mapped to ports on Cellular IP

nodes

• Soft state mappings

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Mappings

• Paging cache/Routing Cache

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État de l'utilisateur

• État actif– Utilisateur en train d'envoyer ou de recevoir des paquets

– Initialisé à la suite d'un paging ou d'une demande d'émission– Position du terminal déterminée à la cellule près

• État oisif (ou idle)– Permet de réduire la signalisation sur le lien radio

– L'utilisateur peut rester attaché au réseau d'accès tout en étantinactif

– Localisé dans un groupement de cellules• Permet d'accueillir un grand nombre de visiteurs dans un

même domaine• Pas d'enregistrement à chaque passage dans chaque cellule– Si un utilisateur oisif reçoit des paquets, on s'appuie sur un

paging• À l'initiative du nœud cherchant à localiser l'utilisateur

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Localisation d’un utilisateur

• 2 exigences pour la réussite d'une localisation– Laisser toute la liberté à un terminal oisif

• Ne pas le contraindre à se signaler– Mettre en œuvre un mécanisme optimal pour

atteindre leterminal oisif à un coût moindre lorsqu'il devient actif

• 2 procédures employées pour répondre à ces besoins– Enregistrement de la localisation de temps à autre en

casd'activité

• Cache de routage ou RC (Routing Cache)– Emploi de paging en cas d'oisiveté

• Cache de paging ou PC (Paging Cache)

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Caches de paging

• Liberté de mouvement pour les utilisateurs– Ne facilite pas leur localisation

– Il faut retrouver un mobile oisif pour lui transmettre unpaquet

• Surplus de signalisation• Caches installés dans certains nœuds ou stations de

base– Connaissance partielle de la localisation des mobiles

– Complétée par le paging• Mise à jour des Paging Caches

– Par l'envoi vers la racine d'un paquet vide : paging-update– Paging-update transmis de manière périodique

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Identification d'un terminal oisif

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Caches de paging

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Cache de routage

• Permet d'acheminer le flux de paquets versl'utilisateur

– Routage saut par saut (hop by hop)– Enregistrement du chemin à l'initiative de l'utilisateur

• Lorsqu'il envoie un paquet vers la racine, tous les nœudsintermédiaires retiennent le chemin pour l'utiliser en sens

inverse• Si l'utilisateur cesse son activité réseau– Possibilité de se maintenir dans les RC

• Transmission de paquets vides : route-update, vers laracine

• Sinon, effacement sur temporisation

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Routage

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Route discovery

– When the mobile receives PP, it sends a Route-Update Packet to the base station F which forwards it towards GW– All the RCs on the route are updated

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Downlink routing

• If there is no PC on the GW:

– GW buffers the packet

– GW sends a Paging Packet with the mobile's id

– If the nodes have paging caches, hop by hop routing,

otherwise, the packet is broadcast

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Handoff

• Initiated by the mobile• When a mobile gets close to a new BS,

it redirects itspackets to the new BS

• The first packet redirected configures a new route

• The packets are send to the old and new BS during acertain time

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Summary

• Use of the home address

• No temporary address

• No encapsulation

• The mobile sends the gateway address to the HA

• GW@ is learnt by the BS

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HMIP

• Cellular IP

• Hawaii

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Hawaii

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Hawaii

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Routing Update ( 1)

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Routing Update ( 2)

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Hawaii

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Plan







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IPv4 vs IPv6

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Mobile IPv6

• IPv6 mobility relies on:– New functionnalities in IPv6– A native support of mobility

• A global and unique IPv6 address is assigned to each

mobile node: the Home Address– This address identifies the mobile

• A mobile is able to communicate directly with mobile

nodes (no triangle routing)

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Main functionnalities in IPv6

• The correspondents must– Have a binding in their binding cache

– Learn the location of the mobile by handlingBinding Updates

– Route the packets directly to the mobile (RoutingHeader)

• TheHA must– Be a router on the mobile's home network– Intercept the packets on the home network

– Tunnel (IPv6 encapsulation) these packets directlyto the mobile

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Reaching the mobile

• A mobile can always be reached via its HA• A mobile on a visited network always has a COA

(selfconfiguration)• The Router Advertisement indicates the subnetwork’s

prefix• Combination of this prefix with the MAC address• Movement detection is also accomplished with

NeighborDiscovery procedures

• Multi-homing

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IPv6 Destination options

• Binding Update :– To inform the HA or the correspondents of the new COA

• Binding request– Ask for a BU. Used when a correspondent thinks its binding will

soon expire• Binding Acknowledgement

– Sent by the HA. Acknowledges a BU containing the COA• Home Address

– Included in every IPv6 packet from the mobile to its correspondent

The packet is supposed to be originated from the home networkand not the visited network

Uses 144 bits in the header of every packet

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Cache association management

• Every time a mobile moves it sends a Binding Update (BU):

• The BU includes a lifetime• The mobile keeps a list of the

correspondents towhich it sent a BU

• The temporary address sent to the HA is called the

principal COA

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The IETF model

140

BU format

141

Binding Acknowledge message

• ACK message based on a destination header extension

• Sent if the A bit is set in the BU sent by the mobile• Also includes an authentication header

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Binding Request & Home address

• Allows the correspondents to update their bindings

• Store the principal address of the mobile

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IPv6 Nodes

Handling IPv6 mobility forces the nodes to implement somefunctionnalities:

• Be able to receive and handle BUs• SendBAs

• Use RoutingHeader• Maintain a Binding Cache

An IPv6 node must be able to• Do IPv6 decapsulation

• Send BUs and receive BAs• Maintain a list of BUs sent

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IPv6 routersAt least one router on the mobile's home

network may actas a HA

A HA must:– Maintain a Binding table

– Intercept packets in the mobile's home network

– Encapsulate these packets and send them to the mobile's COA

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HA discovery

• Modification of the Routing Advertisement (RA) message of Neighbor

Discovery• Add an option to the RA message

• Modify the minimal time (3 seconds) between two RAs (1

message/sec)• Send a BU (with the H bit set) to the anycast

address of the HAs

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IPv6 and mobility (1)• IPv6 represents an almost perfect protocol basis for mobile

networking– First, the attendant address configuration protocols allow each

Mobile Node to obtain a Care-of Address without the need forForeign Agents which disappear from the architecture

– Second, IPsec implementation is mandatory to IPv6 compliantsystems. This resolves security pitfalls by providing awidely available and standardized security architecture

• Particularly, mobility bindings are now done by the MobileNodes themselves

– Third, the destination options IPv6 header extension providesmeans to sending mobility bindings updates from the

Mobile Nodes directly to Correspondent Nodes very efficiently• This simplifies the smooth handoff procedure

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IPv6 and mobility (2)

Correspondent Node

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Data mobility perspectives

• The Mobile IP architecture is being finalized at the IETFwith its basic mechanisms already terminated and some

enhanced functionalities being added progressively• The market opportunities for this architecture are huge

and should follow the explosive growth of bothcomputer/Internet industries on the one hand and mobile

telephony on the other hand• Some work still has to be done however to integrate bothapproaches by having a single network infrastructure forboth Mobile IP and other mobility approaches such as the

third generation of Mobile Cellular Networks (UMTS)• This conforms to the global “service integration over aconsolidated network infrastructure” trend for public

networks

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HMIPv6

• MAP (Mobility Anchor Point)

– Minimizes interruptions due to handoffs

• The mobiles use the MAP's IP@ as COA

• MAP receives the packets and delivers them

to the mobile

• The access routers send the

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HMIPv6

• The access routers send the MAP's IPv6@ in RAs

• The mobile may roam and

keep the same MAP

• If the mobile changes its

MAP, it sends a new BU to

its HA and correspondents

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HMIPv6

IPv6MobHAIPv6MobCOA

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Plan







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MIP-UMTS standardized architecture

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MIP-UMTS other solutions (1/2)

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MIP-UMTS other solutions (2/2)

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3GPP Network Reference Architecture – R5

157

Mobile IP in UMTS

158

Data mobility perspectives

• The Mobile IP architecture is being finalized at the IETFwith its basic mechanisms already terminated and some

enhanced functionalities being added progressively• The market opportunities for this architecture are huge

and should follow the explosive growth of bothcomputer/Internet industries on the one hand and mobile

telephony on the other hand• Some work still has to be done however to integrate bothapproaches by having a single network infrastructure forboth Mobile IP and other mobility approaches such as the

third generation of Mobile Cellular Networks (UMTS)• This conforms to the global “service integration over aconsolidated network infrastructure” trend for public

networks

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