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2. Mobile IP (I). Mobile IP adds mobility support to the Internet network layer protocol IP.The Internet started at a time when no-one had a concept of mobile computers.The Internet of today lacks mechanisms for the support of users traveling through the world.IP is the common base for thousands
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1. 1 MOBILE NETWORK LAYER Mobile IP
2. 2 Mobile IP (I) Mobile IP adds mobility support to the Internet network layer protocol IP.
The Internet started at a time when no-one had a concept of mobile computers.
The Internet of today lacks mechanisms for the support of users traveling through the world.
IP is the common base for thousands of applications and runs over dozens of different networks; this is the reason for supporting mobility at the IP layer.
Motivation for Mobile IP:
Routing
based on IP destination address, network prefix determines physical subnet
Change of physical subnet implies change of IP address to have a topological correct address (standard IP) or needs special entries in the routing tables
3. 3 Mobile IP (II) Create specific routes to end-systems – mobile nodes?
change of all routing table entries to forward packets to the right destination
does not scale with the number of mobile hosts and frequent changes in the location
Changing the IP address?
adjust the host IP address depending on the current location
almost impossible to find a mobile host, DNS has not been built for frequent updates
TCP connection break
4. 4 Mobile IP (III) Requirements to Mobile IP:
Transparency
mobile end-systems keep their IP address
continuation of communication after interruption of link possible
point of connection to the fixed network can be changed
Compatibility
support of the same layer 2 protocols as IP does
no changes to current end-systems and routers required
Mobile end-systems can communicate with fixed systems
5. 5 Mobile IP (IV) Security
authentication of all registration messages
Efficiency and scalability
only little additional messages to the mobile system required (connection typically via a low bandwidth radio link)
world-wide support of a large number of mobile systems in the whole Internet
6. 6 Real-life Solution Take up the analogy of you moving from one apartment to another. What do you do?
Leave a forwarding address with your old post-office
The old post-office forwards mail to your new post-office, which then delivers it to you
Same Principle as call forwarding!
Same Principle as call forwarding!
7. 7 Mobile IP - Definition “Mobile IP (MIP) is a modification to IP that allows nodes to continue to receive datagrams no matter where they happen to be attached to the Internet”
Same Principle as call forwarding!
Same Principle as call forwarding!
8. 8 Mobile IP (V) Terminology:
Mobile Node (MN)
system (node) that can change the point of connection to the network without changing its IP address
Home Agent (HA)
system in the home network of the MN, typically a router
registers the location of the MN, tunnels IP datagrams to the COA
Foreign Agent (FA)
system in the current foreign network of the MN, typically a router
forwards the tunneled datagrams to the MN, typically also the default router of the MN
9. 9 Mobile IP (VI) Care-of Address (COA)
address of the current tunnel end-point for the MN (at FA or MN)
actual location of the MN from an IP point of view
can be chosen, e.g., via DHCP
Correspondent Node (CN)
communication partner
10. 10 Mobile IP in detail … Combination of 3 separable mechanisms:
Discovering the care-of address
Registering the care-of address
Tunneling to the care-of address
Going back to the basic process we can have all the functions acting independently.Going back to the basic process we can have all the functions acting independently.
11. 11 Mobile IP in detail These diagrams show the different signaling messages needed to establish a mobile IP connection and communication.
The diagram on the left is for MIPv4 and the one on the right is for MIPv6
In MIPv4 we see that the HA is the one taking care of the triangular routing, whereas is MIPv6 this responsibility is delegated to the mobile node.
IPv6 and MIPv6 were designed from the beginning with mobility in mind and
support these functions in a more simple way
These diagrams show the different signaling messages needed to establish a mobile IP connection and communication.
The diagram on the left is for MIPv4 and the one on the right is for MIPv6
In MIPv4 we see that the HA is the one taking care of the triangular routing, whereas is MIPv6 this responsibility is delegated to the mobile node.
IPv6 and MIPv6 were designed from the beginning with mobility in mind and
support these functions in a more simple way
12. 12 Discovering the care-of address Discovery process built on top of an existing standard protocol: router advertisements
Router advertisements extended to carry available care-of addresses called: agent advertisements
Foreign agents (and home agents) send agent advertisements periodically
A mobile host can choose not to wait for an advertisement, and issue a solicitation message
13. 13 Agent advertisements Foreign agents send advertisements to advertise available care-of addresses
Home agents send advertisements to make themselves known
Mobile hosts can issue agent solicitations to actively seek information
If mobile host has not heard from a foreign agent its current care-of address belongs to, it seeks for another care-of address
14. 14 Registering the Care-of Address Once mobile host receives care-of address, it registers it with the home agent
A registration request is first sent to the home agent (through the foreign agent)
Home agent then approves the request and sends a registration reply back to the mobile host
Security?
15. 15 Registration Illustration
16. 16 Home agent discovery If the mobile host is unable to communicate with the home agent, a home agent discovery message is used
The message is sent as a broadcast to the home agents in the home network
17. 17 Tunneling to the Care-of address When home agent receives packets addressed to mobile host, it forwards packets to the care-of address
How does it forward it? - encapsulation
The default encapsulation mechanism that must be supported by all mobility agents using mobile IP is IP-within-IP
Using IP-within-IP, home agent inserts a new IP header in front of the IP header of any datagram
18. 18 Tunneling (contd.) Destination address set to the care-of address
Source address set to the home agent’s address
After stripping out the first header, IP processes the packet again
19. 19 Tunneling Illustration
20. 20 Mobile IP (VII) Example network
21. 21 Mobile IP (VIII) Data transfer to the mobile system
22. 22 Mobile IP (IX) Data transfer from the mobile system
23. 23 Mobile IP (XIII) Optimization of packet forwarding:
Triangular routing
sender sends all packets via HA to MN
higher latency and network load
Solutions – optimization
HA informs a sender about the location of MN
sender learns the current location of MN
direct tunneling to this location
big security problems!
24. 24 Mobile IP (XIV) Change of FA
Packets on-the-fly during the change can be lost
new FA informs old FA to avoid packet loss, old FA forwards remaining packets to new FA
this information also enables the old FA to release resources for the MN
25. 25 Mobile IP (XV) Change of the foreign agent with the optimized mobile IP
26. 26 Mobile IP (XVI)
27. 27 Mobile IP (XVII) Mobile IP with reverse tunneling
Router accept often only “topological correct“ addresses (firewall!)
a packet from the MN encapsulated by the FA is now topological correct
furthermore multicast and TTL problems solved (TTL in the home network correct, but MN is to far away from the receiver)
Reverse tunneling does not solve
problems with firewalls, the reverse tunnel can be abused to circumvent security mechanisms (tunnel hijacking)
optimization of data paths, i.e. packets will be forwarded through the tunnel via the HA to a sender (double triangular routing)
The standard is backwards compatible
the extensions can be implemented easily and cooperate with current implementations without these extensions
Agent Advertisements can carry requests for reverse tunneling
28. 28 Mobile IP in detail USE POINTER
Mobile IP (MIP) allows IP nodes to maintain connectivity while moving
A Mobile Node (MN) is assigned a Care-of Address (CoA) when it moves to a foreign sub-network
The COA can be an address obtained by the FA OR AN ADDRESS OBTAINED DYNAMICALLY
The Home Agent will intercept and tunnel all packets to the MNs CoA
A Foreign Agent (FA) or the MN will de-tunnel the packets and eventually set up a direct connection with the CH via an Optimal Route
USE POINTER
Mobile IP (MIP) allows IP nodes to maintain connectivity while moving
A Mobile Node (MN) is assigned a Care-of Address (CoA) when it moves to a foreign sub-network
The COA can be an address obtained by the FA OR AN ADDRESS OBTAINED DYNAMICALLY
The Home Agent will intercept and tunnel all packets to the MNs CoA
A Foreign Agent (FA) or the MN will de-tunnel the packets and eventually set up a direct connection with the CH via an Optimal Route
29. 29 Route Optimizations Enable direct notification of the corresponding host
Direct tunneling from the corresponding host to the mobile host
Binding cache maintained at corresponding host
30. 30 Route optimizations (contd.) 4 types of messages
Binding update
Binding request
Binding warning
Binding acknowledge
31. 31 Binding Update When a home agent receives a packet to be tunneled to a mobile host, it sends a binding update message to the corresponding host
When a home agent receives a binding request message, it replies with a binding update message
Also used in the the smooth-handoffs optimization
32. 32 Binding Update (Contd.) Corresponding host caches binding and uses it for tunneling subsequent packets
Lifetime of binding?
Corresponding host that perceives a near-expiry can choose to ask for a binding confirmation using the binding request message
Home agent can choose to ask for an acknowledgement to which a corresponding host has to reply with a binding ack message
33. 33 Binding warning When a foreign agent receives a tunneled message, but sees no visitor entry for the mobile host, it generates a binding warning message to the appropriate home agent
When a home agent receives a warning, it issues an update message to the corresponding host
What if the foreign agent does not have the home agent address (why?) ?
34. 34 Binding Update and Warning
35. 35 Mobile IP and IPv6 Mobile IP was developed for IPv4, but IPv6 simplifies the protocols
security is integrated and not an add-on, authentication of registration is included
COA can be assigned via auto-configuration (DHCPv6 is one candidate), every node has address autoconfiguration
no need for a separate FA, all routers perform router advertisement which can be used instead of the special agent advertisement; addresses are always co-located
MN can signal a sender directly the COA, sending via HA not needed in this case (automatic path optimization)
„soft“ hand-over, i.e. without packet loss, between two subnets is supported
MN sends the new COA to its old router
the old router encapsulates all incoming packets for the MN and forwards them to the new COA
authentication is always granted
36. 36 Problems with mobile IP Security
authentication with FA problematic, for the FA typically belongs to another organization
no protocol for key management and key distribution has been standardized in the Internet
patent and export restrictions
Firewalls
typically mobile IP cannot be used together with firewalls, special set-ups are needed (such as reverse tunneling)
QoS
many new reservations in case of RSVP
tunneling makes it hard to give a flow of packets a special treatment needed for the QoS
Security, firewalls, QoS etc. are topics of current research and discussions!
37. 37 Security in Mobile IP Security requirements (Security Architecture for the Internet Protocol, RFC 1825)
Integrityany changes to data between sender and receiver can be detected by the receiver
Authenticationsender address is really the address of the sender and all data received is really data sent by this sender
Confidentialityonly sender and receiver can read the data
Non-Repudiationsender cannot deny sending of data
Traffic Analysiscreation of traffic and user profiles should not be possible
Replay Protectionreceivers can detect replay of messages
38. 38 IP Micro-mobility support Micro-mobility support:
Efficient local handover inside a foreign domainwithout involving a home agent
Reduces control traffic on backbone
Especially needed in case of route optimization
Example approaches:
Cellular IP
HAWAII
Hierarchical Mobile IP (HMIP)
Important criteria: Security Efficiency, Scalability, Transparency, Manageability
39. 39 Cellular IP Operation:
„CIP Nodes“ maintain routing entries (soft state) for MNs
Multiple entries possible
Routing entries updated based on packets sent by MN
CIP Gateway:
Mobile IP tunnel endpoint
Initial registration processing
Security provisions:
all CIP Nodes share„network key“
MN key: MD5(net key, IP addr)
MN gets key upon registration
40. 40 Cellular IP: Security Advantages:
Initial registration involves authentication of MNsand is processed centrally by CIP Gateway
All control messages by MNs are authenticated
Replay-protection (using timestamps)
Potential problems:
MNs can directly influence routing entries
Network key known to many entities(increases risk of compromise)
No re-keying mechanisms for network key
No choice of algorithm (always MD5, prefix+suffix mode)
Proprietary mechanisms (not, e.g., IPSec AH)
41. 41 Cellular IP: Other issues Advantages:
Simple and elegant architecture
Mostly self-configuring (little management needed)
Integration with firewalls / private address support possible
Potential problems:
Not transparent to MNs (additional control messages)
Public-key encryption of MN keys may be a problemfor resource-constrained MNs
Multiple-path forwarding may cause inefficient use of available bandwidth
42. 42 HAWAII Operation:
MN obtains co-located COAand registers with HA
Handover: MN keeps COA,new BS answers Reg. Requestand updates routers
MN views BS as foreign agent
Security provisions:
MN-FA authentication mandatory
Challenge/Response Extensions mandatory
43. 43 HAWAII: Security Advantages:
Mutual authentication and C/R extensions mandatory
Only infrastructure components can influence routing entries
Potential problems:
Co-located COA raises DHCP security issues(DHCP has no strong authentication)
Decentralized security-critical functionality(Mobile IP registration processing during handover)in base stations
Authentication of HAWAII protocol messages unspecified(potential attackers: stationary nodes in foreign network)
MN authentication requires PKI or AAA infrastructure
44. 44 HAWAII: Other issues Advantages:
Mostly transparent to MNs(MN sends/receives standard Mobile IP messages)
Explicit support for dynamically assigned home addresses
Potential problems:
Mixture of co-located COA and FA concepts may not besupported by some MN implementations
No private address support possiblebecause of co-located COA
45. 45 Hierarchical Mobile IPv6 (HMIPv6) Operation:
Network contains mobility anchor point (MAP)
mapping of regional COA (RCOA) to link COA (LCOA)
Upon handover, MN informsMAP only
gets new LCOA, keeps RCOA
HA is only contacted if MAPchanges
Security provisions:
no HMIP-specificsecurity provisions
binding updates should be authenticated
46. 46 Hierarchical MIP
47. 47 Hierarchical Mobile IP: Security Advantages:
Local COAs can be hidden,which provides some location privacy
Direct routing between CNs sharing the same link is possible (but might be dangerous)
Potential problems:
Decentralized security-critical functionality(handover processing) in mobility anchor points
MNs can (must!) directly influence routing entries via binding updates (authentication necessary)
48. 48 Hierarchical Mobile IP: Other issues Advantages:
Handover requires minimum numberof overall changes to routing tables
Integration with firewalls / private address support possible
Potential problems:
Not transparent to MNs
Handover efficiency in wireless mobile scenarios:
Complex MN operations
All routing reconfiguration messages sent over wireless link
49. 49 Smooth Hand-offs When a mobile host moves from one foreign agent to another …
Packets in flight to the old FA are lost and are expected to be recovered through higher layer protocols (e.g. TCP)
How can these packets be saved?
50. 50 Smooth Hand-offs Make previous FA forward packets to the new FA
Send binding updates to the old FA through the new FA
Such forwarding will be done for a pre-specified amount of time (registration lifetime)
Update can also help old FA free any reserved resources immediately
Why better?
51. 51 Recap Host mobility and Internet addresses
Post-office analogy
Home agent, foreign agent, care-of address, home address
Registration and Tunneling
Mobile IP problems
Mobile IP Optimizations
Other options