1. Mobilité IP
1

2. 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
2

3. Différents types de mobilité
3

4. Différents types de mobilité
• Nomadisme (DHCP)
• Ordinateurs mobiles (Mobile IP, IEEE
802.11)
• Réseaux mobiles (réseaux Ad-hoc)
• Besoin de protocoles fournissant un service
de localisation
4

5. 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
5

6. Mobilité IP ≠ LANs sans fil
(WLAN)
6

7. 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
7

8. Différents types de mobilité
8

9. Mobilité
9

10. 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
10

11. 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
11

12. 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
12

13. Problématique de la mobilité
dans IP
• Difficultés pour intégrer à IP de nouvelles
fonctions devant offrir la mobilité
13

14. 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 use
when mobility is considered
14

15. IP mobility: routing
15

16. Why isn’t IP mobility simple? (2)
• 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
16

17. Why isn’t IP mobility simple? (3)
• 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
17

18. 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) Working
Group is in charge of defining and specifying the Mobile IP
architecture and protocols
• The major architecture components are already in the standards
track (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
18

19. 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
19

20. Overview of the IP mobility
architecture
20

21. Functional entities
• Mobile node : A host or a router that roams from one
network or subnetwork to another outside its home network
without changing its long term IP address (the home address)
• Home agent : This is typically a router on a mobile node’s
home network which delivers datagrams to departed mobile
nodes, and maintains current location information for each
• Foreign agent : This is typically a router on a mobile node’s
visited network that collaborates with the Home agent to
complete the delivery of datagrams to the mobile node while
it is away from home
21

22. The Mobile IP basic concept
The Mobile IP basic concept The Mobile IP basic concept
• The Mobile IP architecture resolves the above contradiction
by using 2 IP addresses for a mobile host :
– The Home address is a permanent address used to
identify uniquely the IP host on the Internet (answers the
two first IP addresses constraints)
– The Care-of address is a temporary address used to
route the datagrams destined to the mobile host to the
current attachment point of this host (answers the last IP
addresses constraint)
22

23. 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
23

24. Main Functions
• Agent Discovery :
– Home Agents & Foreign Agents send advertisements
on the
link. A mobile can ask for advertisements to be sent.
• Registration :
– When a mobile is away, it registers its temporary
address
with its home agent
• Tunneling :
– The packets for the mobile are intercepted by the HA
and
tunnelled to the mobile
24

25. Mobile IP
25

26. Protocol overview
1. Home Agent & Foreign Agent broadcast or multicast
agent advertisements on their respective links.
2. Mobile nodes listen to Agent Advertisements. They
examine the contents of these advertisements to
determine whether they are on the home or on a
visited network
3. A mobile node on a visited network acquires a
temporary address (care of address)
26

27. Protocol overview
4. The mobile registers its COA with its home agent
5. The Home Agent sends ARP on the Home Network
(IP@ <-> MAC@). The packets for the mobile are
intercepted and sent to the current position of the
mobile
6. The packets arrive to the COA and are decapsulated
in
order to extract the original packet
7. The packets from the mobile are sent directly to the
correspondents
27

28. IP mobility mechanisms
Agent discovery
Registration
Tunneling
28

29. 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 a
visited 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 to
wait for an AA
• Message authentication
29

30. Agent Solicitation Message
30

31. Mobile Agent Discovery
• An extension, called the Mobility Agent extension, is
appended to ICMP Router Advertisement to constitute the
Agent Advertisement message
• A Foreign Agent uses the Agent Advertisement message in order
to indicate the Care-of Address to a Mobile Node
• A Home Agent uses the Agent Advertisement message so that a
Mobile Node knows when it has returned to its Home
Network
• A Mobile Node is allowed to send ICMP Router Solicitation
messages in order to elicit a Mobility Agent Advertisement
31

32. Mobile Agent Discovery
Getting a COA
• A Care-of Address may be obtained from the Foreign Agent by
an 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 collocated
since it is directly assigned to the Mobile Node interface and
not to a Mobile Node through a Foreign Agent.
• For a collocated Care-of Address, the tunnel terminates at the
Mobile Node interface
32

33. Agent Advertisement Message
33

34. Mobile Agent Discovery
• It is based upon an extension of the ICMP
(Internet
Control Message Protocol) Router Discovery
protocol
• A router periodically broadcasts ICMP Router
Advertisement messages on the different
directly
attached subnetworks
• This allows the hosts on these subnets to
discover the
router
34

35. Mobile Agent Discovery
Mobility 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 number
of Care-of Addresses
• Lifetime specifies the duration of the Care-of Address support on the
Foreign 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
35

36. 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 of
attachement
• Use of the information obtained by agent discovery to determine
the
type of registration to be done
• Two registration procedures
– With the«ForeignAgent»
– With the temporary address of the mobile
36

37. Registration
• Once the Mobile Node receives a Care-
of Address, it should
register its (Home Address, Care-of
Address) binding at
his Home Agent
• This is done using 2 messages :
– Registration Request
– Registration Reply
• They both use a UDP/IP service
37

38. Registration
38

39. Registration
request
39

40. Registration
40

41. Registration
Registration 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 the
binding
• Identification is used to protect against replay attacks and allows to
correlate a Registration Request with a Registration Reply message
• The Mobile-Home authentication extension is used to authenticate
the Mobile Node at the Home Agent
41

42. 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 the
FA
• 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
42

43. Registration
Registration 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 is
related
• Home Agent identifies the Home Agent having registered the
binding
• Identification is used to protect against replay attacks and allows to
correlate 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
43

44. Registration Reply
• The FA receives a registration reply
– If the RR is invalid, the agent sends a Registration
Reply describing the reason
why 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 registration
procedure
– Otherwise the mobile updates its routing table
44

45. Registration
Reply
45

46. Registration
Reply
46

47. Registration
• Via le Foreign Agent :
47

48. 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
48

49. Exemple
49

50. Exemple
50

51. Exemple
Annuler l’enregistrement (au retour au
réseau home) :
51

52. Exemple
52

53. De-registration
53

54. Discovering the HA's address
• Manual configuration on the mobile
• Automatically
– By broadcasting a registration request
54

55. Learning the HA address
55

56. Learning the HA address
56

57. Learning the HA address
57

58. 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
58

59. 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 on
the 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
59

60. 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
60

61. Packet interception
by the HA
61

62. Home Network configurations
62

63. Proxy and Gratuitous ARP Proxy
• In the cases A and B above, the Home Agent should intercept the
datagrams intended to Mobile Nodes using a Proxy ARP
mechanism
• In the case C, all datagrams intended to Mobile nodes will be
naturally intercepted by the Home Agent. Here, all the hosts are
outside their Home Network which become a Virtual Network
• Gratuitous ARP should be used by the Home Agent in order to
change 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, Gratuitous
ARP should again be used by the Mobile Node itself to restore the
ARP cache entry
63

64. Security aspects (1)
• The security issue is fundamental for registration messages otherwise
impersonation 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 not
mandatory with IPv4
• An authentication extension is thus appended to each of the above
messages
• The default authentication algorithm is a keyed-MD5 in prefix + suffix
mode
• The result of the authentication is thus a 128 bit message digest
transmitted in the authentication extension
64

65. 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
authentication
extension
65

66. Firewalls and packet filtering
problems (1)
66

67. Firewalls and packet filtering
problems (2)
• Ingress filtering is often applied in the border gateway of a
corporate network playing the role of a firewall
• This prevents Mobile Node generated datagrams to reach the
Internet coming from the Visited Network
• Solutions
– Send datagrams with Source Address=Care-of Address this
is a loosing proposition because it runs counter to the
architecture
– Send datagrams encapsulated in an outer IP header with
Source Address=Care-of Address this is a better
proposition but the Correspondent Nodes are not required to
be able to do the decapsulation Encapsulated datagrams
may be sent to the Home Agent which sends them back to the
Correspondent Node this is a suboptimal solution on the
routing standpoint
67

68. Firewalls and packet filtering
problems (3)
• Correlated problem : the firewall on the Home Network
side 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 be
accepted
– Otherwise, a protocol between the Home Agent and the
Firewall may be necessary
– Finally, a solution may consist in tunneling all such datagrams
to the Home Agent which should play the role of a bastion
host and be attached to a DMZ for safety
68

69. Datagram Tunneling
• A Correspondent Node sends datagrams to a Mobile Node with
the 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 the
initial 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 the
Correspondent Node
69

70. Reminder : IPv4 header
format
70

71. IP-within-IP encapsulation
• The original IP header remains unchanged when transmitted in
the 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 IP
datagram level otherwise the fragments won’t transport the Mobile
Node’s Home Address used at the Foreign Agent to send the
decapsulated datagram on the right data link
71

72. Minimal encapsulation
• S indicates the presence of the Original Source Address field
• Minimal encapsulation limits the number of supplementary
bytes necessary for tunneling
• It prevents however from performing fragmentation
72

73. 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 each
established 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 the
Correspondent 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
73

74. 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
74

75. Enhanced functionnalities
• Optimisation du routage
• Smooth handoff
75

76. Routing optimisation
• Goal : Avoid triangle routing
• Idea:
– Tell the correspondents the current
position of the mobile
node
• Problem:
– Change the correspondent's IP stack
76

77. Triangle Routing
77

78. Route optimization (1)
• The basic Mobile IP mechanisms create a Triangle Routing
between 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 Mobile
Node
• 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 the
Mobile Node
• For security purposes, it is the responsibility of the Home
Agent to send the mobility binding to the Correspondent
Nodes that need them
78

79. Route optimization (2)
Correspondent Node
79

80. Route optimization (3)
• 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
but
supposes that the Correspondent Nodes are able to
implement the route optimization protocol
• This may be the main reason why this mechanism has
not yet
been definitively adopted as an RFC
80

81. Foreign Agent - Smooth
Handoff
• When a mobile moves, it registers with a new FA
• Goal: Tell the old FA the current position so that the
packets 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 the
packets to the new location of the mobile
81

82. Smooth Handoff
(1)
Correspondent Node
82

83. Smooth Handoff
(2)
• During the handoff, it is important that the datagrams intended to the
Mobile 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 Mobile
Node allowing it to relay the datagrams to the new Foreign Agent
• This is best achieved if it remains a local mechanism between the
Mobile 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 security
association be established between the Mobile Node and the Foreign
Agents
83

84. Smooth Handoff
(3)
Correspondent Node
84

85. Smooth Handoff
(4)
• If the previous Foreign Agent does not hold the new mobility binding
for 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 trace
of the Mobile Node and the Mobile Node is not connected elsewhere
• The Foreign Agent should re-encapsulate the decapsulated
datagram into a Special Tunnel getting it back to the Home Agent
with the Care-of Address as the source address of the outer header
• This allows the Home Agent to compare the current registration with
the returned Care-of Address and decide whether it should tunnel the
datagram or not thus avoiding routing loops
85

86. 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
86

87. Micro mobility: Différents
types de mobilité
87

88. 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
88

89. Micro mobility IP
• Fonctionnement en mode paquet
– Différence par rapport aux autres réseaux cellulaires publics
– GSM, UMTS, CDMA 2000 : interfaces radio majoritairement en
mode 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 réseau
d'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'utilisateur
mobile
89

90. Micro mobility
90

91. Macro / Micro mobility
91

92. Solutions de micro mobilité
• Enregistrements régionaux
HMIP
• Cellular IP
• Hawaii
92

93. Regionalized registration (1)
93

94. Regionalized registration (2)
• Regionalized registration is a solution to the reduction of the
registration traffic between a Home and a Visited Network over the
Internet 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 registration
should 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 registration
should be sent to FA1 (and not to the Home Agent) and the tunnels would
be replaced accordingly
94

95. Solutions de micro mobilité
• Enregistrements régionaux
• HMIP
• Cellular IP
• Hawaii
95

96. HMIP: Hierarchical Mobile IP
• Problem: a mobile
registers with its HA
every time it moves
• Goal: reduce
registration time by
using regional
registrations
96

97. HMIP: Registration(1)
97

98. HMIP: Registration(2)
98

99. HMIP: Routing
99

100. HMIP: Ericsson(1)
• Several levels in the
hierarchy
• FA sends advertisements
@FA7,@FA3,@FA1@GF
A (pour FA7)
@FA6,@FA4,@FA2,@GF
A (pour FA6)
• The MN registers the
GFA@
with its HA
• IP tunnels are set up
between the FAs
100

101. HMIP: Ericsson(2)
• When it moves, the mobile
checks the routes to
determine if it is in the
same hierarchy
@FA7,@FA3,@FA1@GFA
(for FA7)
@FA6,@FA4,@FA2,@GFA (for
FA6)
• Fast handoffs : a mobile
may register with several
FAs
• The packets are bicasted by
the GFA
101

102. Solutions de micro mobilité
• Enregistrements régionaux
HMIP
• Cellular IP
• Hawaii
102

103. 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
103

104. Cellular IP:principes
• Caches distribués
– Position des mobiles
– Information de routage
104

105. 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
are
identified with their home address
105

106. Architecture IP cellulaire
106

107. Architecture IP cellulaire
• Réseau d'accès contient des stations de base
– Couverture de microcellules (id GSM)
– Couverture de picocellules, desservies par de petites
antennes dans des espaces privatifs
• Souplesse de fonctionnement grâce à IP
– Méthode de transmission sur l'interface radio indépendante
des 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
107

108. Architecture IP cellulaire
108

109. Opérations dans le réseau
• 3 opérations principales
– Paging
• Localisation d'un utilisateur lors de l'arrivée de paquets à
destination
– Routage
• Acheminement des paquets vers l'utilisateurs à travers les
principaux 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
109

110. Objectifs de Cellular IP
• Migration facile
• Bonne connectivité
• Support du soft handoff
• Passage à l’échelle avec une complexité
minimale
110

111. Cellular IP
• Réseau distribué
• Les noeuds ne connaissent pas la
topologie
• Pas de base de données centralisée
• Bon passage à l’échelle
111

112. 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
112

113. Mappings
• Paging cache/Routing Cache
113

114. 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 étant
inactif
– 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
114

115. 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 le
terminal 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
cas
d'activité
• Cache de routage ou RC (Routing Cache)
– Emploi de paging en cas d'oisiveté
• Cache de paging ou PC (Paging Cache)
115

116. Caches de paging
• Liberté de mouvement pour les utilisateurs
– Ne facilite pas leur localisation
– Il faut retrouver un mobile oisif pour lui transmettre un
paquet
• 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
116

117. Identification d'un terminal
oisif
117

118. Caches de paging
118

119. Cache de routage
• Permet d'acheminer le flux de paquets vers
l'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 nœuds
intermédiaires 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 la
racine
• Sinon, effacement sur temporisation
119

120. Routage
120

121. 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
121

122. 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
122

123. 123

124. Handoff
• Initiated by the mobile
• When a mobile gets close to a new
BS, it redirects its
packets to the new BS
• The first packet redirected configures a
new route
• The packets are send to the old and new
BS during a
certain time
124

125. 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
125

126. Solutions de micro mobilité
• Enregistrements régionaux
HMIP
• Cellular IP
• Hawaii
126

127. Hawaii
127

128. Hawaii
128

129. Routing Update ( 1)
129

130. Routing Update ( 2)
130

131. Hawaii
131

132. 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
132

133. IPv4 vs IPv6
133

134. 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)
134

135. Main functionnalities in IPv6
• The correspondents must
– Have a binding in their binding cache
– Learn the location of the mobile by handling
Binding Updates
– Route the packets directly to the mobile (Routing
Header)
• TheHA must
– Be a router on the mobile's home network
– Intercept the packets on the home network
– Tunnel (IPv6 encapsulation) these packets directly
to the mobile
135

136. 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
Neighbor
Discovery procedures
• Multi-homing
136

137. 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 network
and not the visited network
Uses 144 bits in the header of every packet
137

138. 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 to
which it sent a BU
• The temporary address sent to the HA is
called the
principal COA
138

139. The IETF model
139

140. BU format
140

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
141

142. Binding Request & Home
address
• Allows the correspondents to update
their bindings
• Store the principal address of the mobile
142

143. IPv6 Nodes
Handling IPv6 mobility forces the nodes to
implement some
functionnalities:
• 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
143

144. IPv6 routers
At least one router on the mobile's home
network may act
as 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
144

145. 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
145

146. 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 for
Foreign Agents which disappear from the architecture
– Second, IPsec implementation is mandatory to IPv6 compliant
systems. This resolves security pitfalls by providing a
widely available and standardized security architecture
• Particularly, mobility bindings are now done by the Mobile
Nodes themselves
– Third, the destination options IPv6 header extension provides
means to sending mobility bindings updates from the
Mobile Nodes directly to Correspondent Nodes very efficiently
• This simplifies the smooth handoff procedure
146

147. IPv6 and mobility (2)
Correspondent Node
147

148. Data mobility perspectives
• The Mobile IP architecture is being finalized at the IETF
with 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 both
computer/Internet industries on the one hand and mobile
telephony on the other hand
• Some work still has to be done however to integrate both
approaches by having a single network infrastructure for
both Mobile IP and other mobility approaches such as the
third generation of Mobile Cellular Networks (UMTS)
• This conforms to the global “service integration over a
consolidated network infrastructure” trend for public
networks
148

149. 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
149

150. 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
150

151. HMIPv6
IPv6MobHA
IPv6MobCOA 151

152. 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
152

153. MIP-UMTS standardized
architecture
153

154. MIP-UMTS other solutions
(1/2)
154

155. MIP-UMTS other solutions
(2/2)
155

156. 3GPP Network Reference
Architecture – R5
156

157. Mobile IP in UMTS
157

158. Data mobility perspectives
• The Mobile IP architecture is being finalized at the IETF
with 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 both
computer/Internet industries on the one hand and mobile
telephony on the other hand
• Some work still has to be done however to integrate both
approaches by having a single network infrastructure for
both Mobile IP and other mobility approaches such as the
third generation of Mobile Cellular Networks (UMTS)
• This conforms to the global “service integration over a
consolidated network infrastructure” trend for public
networks
158