Mô tả:
262001
Mobile & Wireless Networking
Lecture 9:
Mobile IP
[Schiller, Section 8.1]
Geert Heijenk
Mobile and Wireless Networking
2009 / 2010
Outline of Lecture 9
Mobile IP Basics
3 parts of Mobile IP:
Advertising Care-of Addresses
Registration
Tunneling
Mobile IPv6
Mobile IPv6 extensions
Hierarchical Mobile IPv6
Fast Handover for Mobile IPv6
Proxy Mobile IPv6
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Motivation for Mobile IP RFC 3344
Routing
Specific routes to end-systems?
based on IP destination address, network prefix (e.g. 129.13.42)
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
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, security problems
Changing the IP-address?
adjust the host IP address depending on the current location
almost impossible to find a mobile system, DNS updates take too
long time
TCP connections break, security problems
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Example network
HA
MN
(Home Agent)
(Mobile Node)
router
home network
Internet
(physical home network
for the MN)
FA
foreign
network
(Foreign Agent)
router
(current physical network
for the MN)
CN
(Correspondent
Node)
router
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Data transfer to the mobile system
HA
2
MN
home network
receiver
3
Internet
FA
1
CN
sender
foreign
network
1. Sender sends to the IP address of MN,
HA intercepts packet (proxy ARP)
2. HA tunnels packet to Care-of Address
(COA), here FA, by encapsulation
3. FA forwards the packet
to the MN
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Data transfer from the mobile system
HA
1
home network
MN
sender
Internet
FA
foreign
network
1. Sender sends to the IP address
of the receiver as usual,
FA works as default router
CN
receiver
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Types of Home Networks
Home agent as a separate system on
the home network
Internet
Home agent integrated with a router
on the home network
Internet
A virtual home network
Internet
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Co-located Care-of Address
HA
MN
home network
receiver
Internet
Tunneling
foreign
network
Standard
Router
CN
sender
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Outline of Lecture 9
Mobile IP Basics
3 parts of Mobile IP:
Advertising Care-of Addresses
Registration
Tunneling
Mobile IPv6
Mobile IPv6 extensions
Hierarchical Mobile IPv6
Fast Handover for Mobile IPv6
Proxy Mobile IPv6
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Agent advertisement
0
7 8
type
#addresses
15 16
23 24
checksum
lifetime
31
code
addr. size
router address 1
preference level 1
router address 2
preference level 2
...
type = 16
type = 16
length
sequence number
length = 6 + 4 * #COAs
R B H F M G r T reserved
registration lifetime
R: registration required
COA 1
B: busy, no more registrations
COA 2
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
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Home Network & Move Detection
Home Network is detected if:
Network Prefix IP Source Address advertisement = Network Prefix
Home Address
Move is detected if:
No advertisement has been received within Lifetime
Network Prefixes have changed
no advertisements --> use promiscuous mode
assistance from higher / lower layers
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Registration
Registration Request
Mobile
Node
Foreign
Agent
Home
Agent
Registration Reply
Registration Request
Mobile
Node
Home
Agent
Registration Reply
Registration Request
Home
Agent
Mobile
Node
Registration Reply
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Mobile IP registration request
0
7 8
type = 1
15 16
S B DM G r T x
home address
home agent
COA
23 24
lifetime
31
identification
extensions . . .
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
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Mobile IP registration reply
0
7 8
type = 3
15 16
code
home address
home agent
31
lifetime
identification
Example codes:
extensions . . .
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
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Simultaneous Bindings
A Mobile Node may register multiple bindings simultaneously
The Home Agent makes multiple copies of packets destined for
the mobile node, and tunnels a copy to each care-of address
Simultaneous bindings may be used to
facilitate seamless hand-off
avoid too frequent registrations
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Tunneling
Packet destined to the mobile node are routed to the home
network (normal IP operation)
Home Agent intercepts packets on the home network
Home Agent encapsulates packets, and tunnels them to the
care-of address
At the care-of address (either Foreign Agent or co-located), the
packet is decapsulated, and delivered to the mobile node
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Packet Interception by Home Agent
Advertise reachability of Mobile Node Home Address
Proxy and Gratuitous ARP:
Home Agent Replies to ARP requests for the Mobile Node (Proxy ARP)
The Home Agent (or Mobile node) broadcasts a not requested ARP after a
change has occurred (Mobile Node has roamed out (or in)) (Gratuitous ARP)
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Encapsulation
original IP header
new IP header
outer header
original data
new data
inner header
original data
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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
ver.
IHL
DS (TOS)
length
IP identification
flags
fragment offset
TTL
IP-in-IP
IP checksum
IP address of HA
Care-of address COA
ver. IHL
DS (TOS)
length
IP identification
flags
fragment offset
TTL
lay. 4 prot.
IP checksum
IP address of CN
IP address of MN
TCP/UDP/ ... payload
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Encapsulation II
Minimal encapsulation (optional) (RFC 2004)
avoids repetition of identical fields
e.g. TTL, IHL, version, DS (RFC 2474, old: TOS)
only applicable for unfragmented packets, no space left for
fragment identification
ver.
IHL
DS (TOS)
length
IP identification
flags
fragment offset
TTL
min. encap.
IP checksum
IP address of HA
care-of address COA
lay. 4 protoc. S reserved
IP checksum
IP address of MN
original sender IP address (if S=1)
TCP/UDP/ ... payload
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