mobile ip, Mobile COmmunication Internet Protocol
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Transcript of mobile ip, Mobile COmmunication Internet Protocol
EPL476 Mobile Networks
Mobile Network Protocols
Instructor: Dr. Vasos Vassiliou
Slides adapted from Prof. Dr.-Ing. Jochen H. Schiller and W. Stallings
2
MOBILE NETWORK LAYER
Mobile IP
3
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
4
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
5
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
6
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
7
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
8
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”
9
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
10
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
11
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
12
CN
2. HA Discovery Request
3. HA Discovery Reply
4. HA Registration through FA
5. HA Registration Ack.
1. CoA Discovery
MN HA
1
2
3
-- MN is Registered with HA --
4
55
-- CoA and HA Discovery --
-- Registration Procedure --
-- CN starts communication with MN --6. Data Packet
7. IP-in-IP Encapsulation
8. Tunneled Data
-- Signals 6-10a as above --
8 77
6a. Data Packet
-- MN starts communication with CN --
8a Detunnelled Data
9. Binding Update
6a6a
-- Discovery and Registration as above --
FA
8a
66
1010. IP-in-IP tunneling
99
10a 10a. Detunnelled Data
CN
2. HA Discovery Request
3. HA Discovery Reply
4. HA Registration BU
5. HA Registration BU Ack.
1. CoA Discovery
MN HA
1
2
3
-- MN is Registered with HA --
4
55
-- CoA and HA Discovery --
-- Registration Procedure --
-- CN starts communication with MN --
6. Data Packet
7. IP-in-IP Encapsulation
8. Tunneled Data
-- Signals 6-10 as above --
8
77
6a. Data Packet
-- MN starts communication with CN --
9. Binding Update
6a6a
-- Discovery and Registration as above --
FA
66
1010. Binding Ack
99
MIPv4 MIPv6
Mobile IP in detail
13
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
14
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
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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?
16
Registration Illustration
17
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
18
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
19
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
20
Tunneling Illustration
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(current physical network for the MN)
home network
(physical home networkfor the MN)
Mobile IP (VII)
Example network
Internet
router
HAMN
router
FA foreign network
routerend-system
CN
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Mobile IP (VIII)
Data transfer to the mobile system
Internethome network
foreignnetwork
FA
HA
MN
receiver
1
2
3
sender
CN
1. Sender sends to the IP address of MN, HA intercepts packet2. HA tunnels packet to COA, here FA, by encapsulation3. FA forwards the packet to the MN
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foreignnetwork
home network
Mobile IP (IX)
Data transfer from the mobile system
Internet
HA
MN
sender
receiver
CN
1. Sender sends to the IP address of the receiver as usual, FA works as default router
FA
1
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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!
25
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
26
Mobile IP (XV)
Change of the foreign agent with the optimized mobile IP
CN HA FAold FAnew MN
t
requestupdate
ACKdata data
MN changeslocationregistration
updateACKdata
data datawarning
update
ACKdata
data
registration
27
Mobile IP (XVI) Reverse tunneling:
Internet
receiver
FA
HA
MN
home network
foreignnetwork
sender
3
2
1
1. MN sends to FA2. FA tunnels packets to HA by encapsulation3. HA forwards the packet to the receiver (standard case)
CN
28
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
29[modified from Ericsson Tech. Rep. 11/0362-FCB, Dec 2000 ]
Mobile IP in detail
type = 16
length = 6 + 4 * #COAs
R: registration required
B: busy, no more registrations
H: home agent
F: foreign agent
M: minimal encapsulation
G: GRE encapsulation
r: =0, ignored (former Van Jacobson compression)
T: FA supports reverse tunneling
reserved: =0, ignored
Agent advertisement
preference level 1router address 1#addressestype
addr. size lifetimechecksum
COA 1COA 2
type = 16 sequence numberlength
0 7 8 15 16 312423code
preference level 2router address 2
. . .
registration lifetime
. . .
R B H F M G r reservedT
Registration
t
MN HAregistrationrequest
registration
reply
t
MN FA HAregistrationrequestregistrationrequest
registration
reply
registration
reply
Mobile IP registration request
home agenthome addresstype = 1 lifetime0 7 8 15 16 312423
T x
identification
COA
extensions . . .
S B DMGr
S: simultaneous bindings
B: broadcast datagrams
D: decapsulation by MN
M mininal encapsulation
G: GRE encapsulation
r: =0, ignored
T: reverse tunneling requested
x: =0, ignored
Mobile IP registration reply
home agenthome addresstype = 3 lifetime0 7 8 15 16 31
code
identification
extensions . . . Example codes:
registration successful
0 registration accepted
1 registration accepted, but simultaneous mobility bindings unsupported
registration denied by FA
65 administratively prohibited
66 insufficient resources
67 mobile node failed authentication
68 home agent failed authentication
69 requested Lifetime too long
registration denied by HA
129 administratively prohibited
131 mobile node failed authentication
133 registration Identification mismatch
135 too many simultaneous mobility bindings
Encapsulation
original IP header original data
new datanew IP header
outer header inner header original data
Encapsulation I Encapsulation of one packet into another as payload
e.g. IPv6 in IPv4 (6Bone), Multicast in Unicast (Mbone) here: e.g. IP-in-IP-encapsulation, minimal encapsulation or GRE (Generic
Record Encapsulation) IP-in-IP-encapsulation (mandatory, RFC 2003)
tunnel between HA and COA
Care-of address COAIP address of HATTLIP identification
IP-in-IP IP checksumflags fragment offsetlengthDS (TOS)ver. IHL
IP address of MNIP address of CNTTLIP identification
lay. 4 prot. IP checksumflags fragment offsetlengthDS (TOS)ver. IHL
TCP/UDP/ ... payload
Encapsulation II Minimal encapsulation (optional)
avoids repetition of identical fields e.g. TTL, IHL, version, DS (RFC 2474, old: TOS) only applicable for non fragmented packets, no space left for
fragment identification
care-of address COAIP address of HATTLIP identification
min. encap. IP checksumflags fragment offsetlengthDS (TOS)ver. IHL
IP address of MNoriginal sender IP address (if S=1)
Slay. 4 protoc. IP checksum
TCP/UDP/ ... payload
reserved
Generic Routing Encapsulation original
headeroriginal data
new datanew header
outer headerGRE header
original dataoriginalheader
Care-of address COAIP address of HATTLIP identification
GRE IP checksumflags fragment offsetlengthDS (TOS)ver. IHL
IP address of MNIP address of CNTTLIP identification
lay. 4 prot. IP checksumflags fragment offsetlengthDS (TOS)ver. IHL
TCP/UDP/ ... payload
routing (optional)sequence number (optional)key (optional)
offset (optional)checksum (optional)protocolrec. rsv. ver.CRK S s
RFC 1701
RFC 2784 (updated by 2890)
reserved1 (=0)checksum (optional)protocolreserved0 ver.C
38
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
39
Route optimizations (contd.)
4 types of messages Binding update Binding request Binding warning Binding acknowledge
40
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
41
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
42
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?) ?
43
Binding Update and Warning
Home Agent
Foreign AgentCorresponding Host
Mobile Host
BU BW
BW
BRBA
Optimization of packet forwarding Problem: Triangular Routing
sender sends all packets via HA to MN higher latency and network load
“Solutions” sender learns the current location of MN direct tunneling to this location HA informs a sender about the location of MN big security problems!
Change of FA packets on-the-fly during the change can be lost new FA informs old FA to avoid packet loss, old FA now
forwards remaining packets to new FA this information also enables the old FA to release
resources for the MN
Change of foreign agent CN HA FAold FAnew MN
MN changeslocation
t
Data Data DataUpdate
ACK
Data Data
RegistrationUpdate
ACKData
Data DataWarning
Request
Update
ACK
DataData
Reverse tunneling (RFC 3024, was: 2344)
Internet
receiver
FA
HA
MN
home network
foreignnetwork
sender
3
2
1
1. MN sends to FA
2. FA tunnels packets to HA
by encapsulation
3. HA forwards the packet to the
receiver (standard case)
CN
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
48
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
49
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!
50
Security in Mobile IP Security requirements (Security Architecture for the Internet
Protocol, RFC 1825) Integrity
any 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
not encrypted encrypted
IP security architecture I Two or more partners have to negotiate security
mechanisms to setup a security association typically, all partners choose the same parameters and
mechanisms Two headers have been defined for securing IP packets:
Authentication-Header• guarantees integrity and authenticity of IP packets• if asymmetric encryption schemes are used, non-repudiation
can also be guaranteed
Encapsulation Security Payload• protects confidentiality between communication partners
Authentification-HeaderIP-Header UDP/TCP-Paketauthentication headerIP header UDP/TCP data
ESP headerIP header encrypted data
Mobile Security Association for registrations parameters for the mobile host (MH), home agent (HA),
and foreign agent (FA) Extensions of the IP security architecture
extended authentication of registration
prevention of replays of registrations• time stamps: 32 bit time stamps + 32 bit random number• nonces: 32 bit random number (MH) + 32 bit random number
(HA)
registration reply
registration requestregistration request
IP security architecture II
MH FA HAregistration reply
MH-HA authenticationMH-FA authentication FA-HA authentication
Key distribution
Home agent distributes session keys
foreign agent has a security association with the home agent
mobile host registers a new binding at the home agent home agent answers with a new session key for foreign
agent and mobile node
FA MH
HA
response:
EHA-FA {session key}
EHA-MH {session key}
54
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