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Transcript of Lec6 Mobile IP - Wireless and Mobile Networking Laboratorywmnlab.ee.ntu.edu.tw/951cross/Lec6 Mobile...
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Network Layer (LayerNetwork Layer (Layer--3)3)• Routing
– Important issue in “mobile” network• IP-based network solution
– IP dominates the networking world!• Mobile network routing
– Mobility management protocols• Global mobility management protocols
– Mobile IP• Local mobility management protocols
– Cellular IP, HAWAII– Ad hoc network routing protocols
• AODV, DSR, OLSR, DSDV…etc
3
IPIP--based Mobilitybased Mobility• Mobile IP
– IETF (www.ietf.org) Internet Engineering Task Force • Mobile IP working group
– RFCs (Request for Comments)
– Mobile IPv4• RFC 3344
– Mobile IPv6• RFC 3775
4
What is Mobile IP?What is Mobile IP?• Basic Mobile IP protocol
– Advertisement– Registration– Tunneling datagrams
• Extensions– Route optimizations– Movement detection issues
• Support protocols– DHCP, AAA, micro-mobility
5
The IP Addressing ProblemThe IP Addressing Problem
• IP address address allocation and administration have historically assumed that there is a close relationship between a computer’s IP address and its physical location
6
IP Address StructureIP Address Structure• Routing prefix
– defines the network on which the address resides
– often determined the netmask– usually subnet prefix
• Host number– fits in the least significant remaining bits of
the IP address following the routing prefix
Routing prefix Host number
32 bits
7
IP Subnet Model vs. MobilityIP Subnet Model vs. Mobility
Router
132.4.16
…2 …3
Router128.8.128
128.8.128.Y132.4.16.Z
Internet
8
The Transport ProblemThe Transport Problem• TCP uses ports and the IP addresses of the
network endpoints to identify a communication channel used for data transfer
SHfloss.watson.ibm.com
MHtapti.cs.umd.edu
9
Problems with Dual use of IP AddressesProblems with Dual use of IP Addresses• Applications use IP addresses
– to identify routes by which datagrams my be exchanged between two network nodes
• Applications use IP addresses– to identify the endpoints themselves
• Dual usage – causes problems when trying to uses
applications (e.g., TCP) when changing the hosts point of attachment
10
SolutionSolution• We observe that
– Applications need an unchanging way to identify the network endpoints
– Routes between the endpoints must change as they move
• Mobile IP solves this issue– by maintaining two addresses; one for each of
the dual usage• Identification• Routing
– one IP address is used to “locate” the mobile host
– the other IP address for “identifying” a communications endpoint on the mobile host
11
““LocatingLocating”” and and ““IdentifyingIdentifying””: : twotwo--tier addressing for mobile nodestier addressing for mobile nodes
Router
132.4.16
…2 …3
Router 128.8.128
128.8.128.Y
132.4.16.Z
Internet
FOO
128.8.128.X
128 8 128 Y 132 4 16 ZFOO
Topologically Significant Address Static Address
12
Concept: home network and foreign Concept: home network and foreign networknetwork
• Home network– Home address: home network should have the
same prefix for mobile nodes’ home addresses• Foreign network
– A network that is not home network• Mobility agents
– Agents that handle IP-mobility• Home Agent• Foreign Agent
13
Mobility Management ModelMobility Management Model• Home network
– datagrams are routed toward the home address– source nodes is unaware of whether the destination is mobile
or not; it simply sends to the home address• Care-of-address (CoA)
– address used to locate the mobile host’s current position– if mobile host is away from home then packets can only be
delivered using Internet routing based on position in the infrastructure
– “readdressing” is the operation used to change the destination address (home address) to the care-of-address
14
Abstract ModelAbstract Model• Two mapping functions
– f(home address) (forwarding address)– g(forwarding address) (home address)
• Readdressing (f) at the home network– associating (in the location directory - LD) the home address and
the care-of-address of the mobile host and maintaining up to date values for this association
– delivering the datagram to the care-of-address• Inverting (g) the readdressing operation once the
datagram arrives at the care-of-address
f gInternetRouting
LD
Source Destination
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Remote Redirection IssuesRemote Redirection Issues• Updating LD raises a number of technical
challenges– the mobile host should drive this update– need security, authentication of control
messages to eliminate well known problems of malicious location updates
16
IETF Mobile IPIETF Mobile IP• The exact ways in which the f, g and LD
functions are located in various nodes and networks distinguishes the various approaches
Mobile Host 2Source
f
LDHome Agent
Mobile Host 1
g
g
Home Network
S
Foreign Agent
Mobile Host, Using DHCP
17
Basic Mobile IP Basic Mobile IP • Operations
– advertisement, registration, tunneling • Mobile host• Home agent
– is a router that tunnels datagarms to a mobile node when it is away from its home network and maintains current location information
• Foreign agent– is a router on the visited network that provides
routing services to the mobile node while registered. Detunnels datagrams
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Agent DiscoveryAgent Discovery• Agent discovery
– home agent and foreign agents may advertise their availability on each link for which they provide services
– a newly arrived mobile node can send a solicitation on the link to learn if any prospective agents are present
19
Mobile IPMobile IP
HA
Subnet C
FA C
Mobile Node
Subnet B
FA FA
HA
Global Internet
Subnet D
(Home agent for a virtual home network)
HA = home agent
FA = foreign agent
Mobile Nodes
20
Registration Registration • Registration
– when the mobile node is away from home, it registers its care of address with its home agent
– depending on its method of attachment, the mobile node will register either directly with its home agent or though a foreign agent, which forwards the registration to the home agent
21
Registration Registration
FA
FA
FA
FA
FA
MHMHrequestsservice
FA relaysstatus to MH
MH
HAFA relaysrequest to HA
HAHA acceptsor denies
FA = foreign agentMH = mobile hostHA = home agent
FAadvertisesservice
22
TunnelingTunneling• Tunneling datagrams
– in order for datagrams to be delivered to the mobile node when it is away from home, the home agent has to tunnel the datagram to the care-of-address
24
Getting a careGetting a care--ofof--address (COA)address (COA)• Two ways to acquire a care-of-address
(COA)– a foreign agent COA is a COA provided by the
foreign agent through its agent advertisement messages
• many modes can use a single FA COA– a colocated COA is a COA acquired by the
mobile node as a local IP address through some external means, which the mobile node then associates with its own network - the address may be dynamic, e.g., DHCP
• only a single mobile can use this address
25
Protocol Operations Protocol Operations • Mobility agent (foreign and home agents)
advertise their presence via agent advertisement messages
• A mobile may optionally solicit an agent advertisement message from any local mobility agent by using an agent solicitation message
• A mobile node receives an agent advertisement and determines whether it is on its home network or a foreign network
• When the mobile detects that it is located on its home network, it operates without mobility services.
26
Protocol OperationsProtocol Operations• If returning to its home network from being
registered elsewhere, the mobile node degregisters with its home agent through a variation of the normal registration process
• When MN detects that it has moved to a foreign network– MN obtains a care-of-address on the foreign network.
• The COA can either be a foreign agent COA• Or a co-located COA
• MN then registers its new COA with its home agent through the – exchange of registration request and registration reply
messages (might through FA or not)
27
Protocol OperationsProtocol Operations• Datagrams sent to the mobile node’s home
address are intercepted by its home agent, tunneled by the home agent to the mobile node’s COA, received at the tunnel endpoint (either at the foreign agent or at the mobile node itself) and finally delivered to the mobile node.
• In the reverse direction, datagram sent by the mobile node may be delivered to their destination using standard IP routing mechanisms, without the necessarily passing through the home agent
28
Protocol ExtensionsProtocol Extensions• Mobile IP defines a set of new control
messages sent with UDP (using well-known port number 434)– registration request – registration reply
• For agent discovery, Mobile IP modifies the existing “router advertisement” and “router solicitation” messages defined for ICMP (Internet Control Message Protocol)
30
AdvertisementAdvertisement• Agent discovery is the method by which a mobile
host– determines whether it is currently connected to its
home network or a foreign network; and– detects when it has moved from one network to
another• Agent solicitation and discovery mechanisms• Router discovery protocol• Agent advertisement• Agent solicitation• Agent discovery by mobile nodes
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Router Discovery ProtocolRouter Discovery Protocol• Router discovery
– provides the means by which IP hosts can determine automatically the local router’s IP address and monitor their continued presence
• This is done by using two simple ICMP messages– one transmitted by the routers and another that may
be transmitted by the hosts themselves• Historical choice of using this protocol for agent
discovery that may have been a poor choice with hindsight
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Router DiscoveryRouter Discovery• Router advertisements
– are periodically multicast or broadcast to those links that the router is connected with which it wishes to offer routing services to
• Hosts listen to the advertisements and select a router address
• The speed at which a host can select a default router is determined by the advertisement period
33
Router Advertisement MessageRouter Advertisement Message
0 1 2 30 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2
type code checksum
num addrs addr entry size lifetime
preference level (1)
router address (1)
34
Router Solicitation (MH initiated)Router Solicitation (MH initiated)• When an IP host needs timely information
about local default routers, it can multicast or broadcast a router solicitation message– Any router in the vicinity will respond with a
unicast router advertisement sent directly to the soliciting host
– After receiving the advertisement the host then responds just as if the advertisement were unsolicited
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Router Solicitation MessageRouter Solicitation Message
0 1 2 30 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2
type code checksum
reserved
36
Agent AdvertisementAgent Advertisement• An agent advertisement is an ICMP router
advertisement that has been extended to also carry mobility advertisements extensions– A mobility agent transmits agent
advertisements to advertise its service on a link
– Mobile hosts use these advertisements to determine their current point of attachment to the Internet
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Agent AdvertisementAgent Advertisement• Within an agent advertisement, ICMP
router advertisement include the following link-layer, IP and ICMP header information
• Link-layer – destination address
• IP fields– TTL, destination address
• ICMP fields– type (9), code (0 and 16), lifetime, router
addresses, number of addresses
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Agent Advertisement ExtensionAgent Advertisement Extension
0 1 2 30 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2
type length sequence number
registration lifetime R B H F M G V reservedzero or more care-of address
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Important FieldsImportant Fields• R (registration required)
– registration with the FA is required rather than collocated care-of address
• B (busy)– if this bit is set the FA will not accept any
registrations from additional mobile hosts• H (home agent)
– if this bit is set the agent offers home agent services on the link which the advertisement is sent
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Important FieldsImportant Fields• F (foreign agent)
– this agent offers service as a foreign agent on the link on which the advertisement if sent
• M (minimal encapsulation)• G (generic record encapsulation)• V (VJ header compression)• care-of addresses (COA)
– the advertised FA care-of address provided by the FA. Must include at least one COA if the F bit is set. More than one COA can be advertised
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Agent SolicitationAgent Solicitation• The format of the agent solicitation is the same
as the ICMP router solicitation. Agent solicitation do, however, always set the TTL to one.
• Advertisements only need to be sent when the site policy requires registration with the agent (R-bit is set) or as a response to a specific agent solicitation
0 1 2 30 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2
type code checksum
reserved
42
Mobile Agent OperationsMobile Agent Operations• A mobility agent should limit the rate of sending
agent advertisements. – recommended maximal rate = 1/second.
• A FA must accept router solicitations even when the IP source address appears to reside on a different subnet
• A mobility agent “may” be configured to send agent advertisements only in response to an agent solicitation
43
Agent Discovery by Mobile NodesAgent Discovery by Mobile Nodes• Agent solicitations should only be sent in the
absence of agent advertisements and when the care-of address can not be determined through a link-layer protocol or other means
• Operational differences to the router solicitation– mobile nodes may solicit more often than once every
three – mobile node that is currently not connected to any FA
may solicit more times than currently configured.
44
Limiting Signaling OverheadLimiting Signaling Overhead• MN should limit the rate at which its sends
solicitations. – 3 initial solicitations at the max rate(1/second) while
searching for an agent.– Subsequent solicitations are required to be sent using
a binary exponential backoff mechanism up to a maximal interval (one minute).
• While searching for an agent the mobile node is not allowed to increase the rate at which it sends solicitations unless it knows it has moved to a new link
45
Agent DiscoveryAgent Discovery• Mobile nodes process agent advertisements to
discover a care-of address and FA. This is to for the registration phase
• Foreign networks can enforce visiting policy. – E.g Set R bit in agent advertisements
• Force mobile nodes to register with FA( when when the mobile might be able to acquire its own COA.)
• Detect returning to home network– MN receives an agent advertisement from its own home
agent
46
DrawbacksDrawbacks• Piggybacking the agent discovery scheme on the
existing route advertisement method is restrictive– E.g. suppose a mobile node makes a cell switch. To
detect the movement at the network layer the mobile node has to hear a mobility agent advertisement
– If the mobile node has to wait three seconds to discover that its previous FA is out of reach and unacceptable response time is observed
• Worse performance can be experienced if multiple advertisements are lost before initiating handoff
49
Mobile IP RegistrationMobile IP Registration
Mobile Host
FAMH = mobile host
HA = home agent
FA = foreign agent
Mobile Host
FA
FA
FA
FA
MH requests service
FA relays status to
MH
HA
HA Tim
e
FA advertises
service
HA accepts or denies
MH requests service
50
OperationsOperations• Request forwarding services when visiting a
foreign network• Inform their home agent of their current
care-of address• Renew a binding that is due to expire• Deregister when they return home
51
RegistrationRegistration• Registration messages exchange the mobile
node’s current binding information among a mobile node (possibly a FA) and its home network
• Registration creates or modifies a mobility binding at the home agent, associating the mobile node’s home address with its COA for a certain length of time called the registration lifetime
52
Movement DetectionMovement Detection• Important issue for handoff performance• How does the mobile device know its moved to a
new cell?– Handoff initiation (criteria and procedures)
• When the mobile node determines that it has moved it should register with a suitable care-of address (COA) on the new foreign network
• Limitations: can’t register more that once per-second on average– Mobile IP is designed to support mobility with handoff
rate less than once per second• Mobile IP supports three types of movement
detection schemes– Room for improvement research in fast handoff
53
Lazy Cell SwitchingLazy Cell Switching• Lazy Cell Switching
– MH waits to hear new agent advertisement based on the lifetime timeout. If it receives one then it knows its still taking to the current BS
– If advertisements are missed then it attempts to register with a possibly new cell using agent solicitation.
– MHs typically try to receive two or more advertisements before expiring any advertisement before attempting to find a new foreign agent (FA)
54
Prefix MatchingPrefix Matching• MH uses the “prefix extension” to
determine whether a newly received agent advertisement is from the same subnet– If the prefix is different it knows its
connected to a new cell and registers
• Downside: the prefix-extension in agent advertisements is optional
55
Eagar Cell SwitchingEagar Cell Switching• Based on the mobile host hearing beacons
from multiple FAs simultaneously. Also make some assumptions about mobility patterns which may not hold – traveling in a straight line.– Maintains list of FAs and their COAs; and the
current FA/COA– Once the current FA is no longer available (e.g.,
because the mobile has moved) then it selects a new one form this list
• Faster than Lazy Cell Switching but makes a number of assumptions
56
Movement Detection without FAsMovement Detection without FAs• All the schemes depend on FA
advertisements – what happens when there are no FAs?– The collocated COA is invalid once a mobile
host has moved• No good solution
– try to detect a lack of traffic but that may not indicate movement to a new cell
57
UDP Registration MessagingUDP Registration Messaging• Mobile IP registration messages use UDP.
– Mobile IP reg. does not need TCP (no need for congestion control and flow control)
IP header fields UDP header Mobile IP message header Extensions …
58
AuthenticationAuthentication• Each mobile node, FA and HA is required to be
able to support a mobility security association for mobile entities indexed by their security parameter index (SPI)
• Registration messages between a mobile node and its HA are required to be authenticated with the “mobile-home” authentication extension
• Replay protection is accomplished by using different values in each registration message to stop malicious users snooping the registration process and effectively replaying authenticated registration
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RegistrationRegistration• Registration messages exchange the mobile
node’s current binding information among a mobile node (possibly a FA) and its home network
• Registration creates or modifies a mobility binding at the home agent, associating the mobile node’s home address with its COA for a certain length of time called the registration lifetime
60
Registration RequestRegistration Request
0 1 2 30 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
home address
care-of address
home agent
type S B D MG V rsv lifetime
identification
extensions …
61
Registration Request FieldsRegistration Request Fields• IP fields
– source address interface address– destination FA or HA
• UDP fields– source and destination ports
• Mobile IP fields– S simultaneous bindings.
• By setting the S-bit, the mobile node is requesting that the home agent retain its prior mobility bindings
62
Registration Request FieldsRegistration Request Fields• B broadcast datagram.
– By setting the B bit the mobile node is requesting that the home agent tunnel any packets broadcast on the home network
• D decapsulation. – By setting the D bit, the mobile node informs
the home agent that it will decapsulate datagrams that are sent to the COA. In this case the mobile node is using a collocated C OA
63
Registration Request FieldsRegistration Request Fields• Lifetime
– the number of seconds remaining before the registration is considered expired
• Home address• Home agent• COA
• The IP address for the end of the tunnel• Identification
– 64 bits used to match reg. Request and replay pairs and to solve the playback problem
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Registration ReplyRegistration Reply• The HA can update some of the information
in the registration request• The FA is not allowed to modify the
lifetime selected by the mobile node in the registration request because the lifetime is covered by the “mobile-home”authentication extension
• Home agent can reduce the lifetime value
65
Registration ReplyRegistration Reply
0 1 2 30 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
home address
care-of address
home agent
type code lifetime
identification
extensions …
66
Registration Reply FieldsRegistration Reply Fields• IP Fields
– source address • typically copied from the destination address of the
registration request to which the agent is replying– destination address
• source address of the registration request• UDP Fields
– source port – destination port copied from the source port
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Registration Reply FieldsRegistration Reply Fields• Type 3 (registration reply)• Code value indicating the result of reg. Request• Lifetime duration for which the binding is valid• Home address• Home agent• Identification
68
Return CodeReturn Code• Registration OK
– accepted– accepted but simultaneous binding not
supported• Registration denied by FA
– reasons unspecified– insufficient resources– mobile node failed authentication– requested encapsulation failed– home network unavailable
69
Registration Denied by the HARegistration Denied by the HA• Insufficient resources• mobile node failed authentication• FA failed authentication• Registration ID mismatch• Too many simultaneous bindings
70
Registration ExtensionsRegistration Extensions• There are three registration extensions
defined for Mobile IP all of which are associated with security to be applied to the registration process– Mobile-home authentication extension– Mobile-foreign authentication extension– Foreign-home authentication extension
• Each extension includes the SPI that indicates the mobility association that contains the secret and other information needed to compute the authenticator
71
Mobile Node Registration StateMobile Node Registration State• State maintained for each pending
registration– link layer address of the FA to which the
registration request was sent– IP destination address of the registration
request– COA used in registration– Original lifetime– Remaining lifetime of the pending registration
72
FA Registration StateFA Registration State• Link layer source address of the mobile
node• IP source address (the mobile node’s home
address)• IP destination address• UDP source port• Home agent address• Identification field• Request registration lifetime• Remaining lifetime of the pending or
current registration
73
HA Registration StateHA Registration State• The home agent is required to be
configured with the home address and mobility security association of each of its authorized mobile nodes
• When a registration request is accepted the HA creates or modifies the entry for the mobile in its mobility binding list– mobile nodes COA– Identification field from the registration reply– remaining lifetime of the registration
• The HA also maintains security associations with various FAs
74
Registering SecurelyRegistering Securely• HA and mobile nodes are required to be
able to perform authentication – Default algorithm: 128-bit MD5– The tunneling feature could be significantly
vulnerable if the registration were not authenticated
– Key management– Replay protection for registration requests
75
Example ScenariosExample Scenarios• Configuration
– mobile nodes home address 129.34.78.5– mobile node’s home agent 129.34.78.254– FA wireless address 137.0.0.11– FA COA 9.2.20.11– DHCP COA 9.2.43.94– mobile node’s source port 1094– FA source port 1105– COA reg. Lifetime 60,000 secs– HA granted lifetime 35,000 secs
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Registration via a FARegistration via a FAIP header fields ICMP header Router Adv. fields Mobile Service Extension
Agent Advertisement
S = 137.0.0.11 type = 9 …… lifetime = 60,000D = 255.255.255.255 code = 16 COA = 9.2.20.11TTl = 1
IP header fields UDP header Mobile IP message fields Authentication ExtensionMobile Foreign
S = 129.34.78.5 S = 1094 type = 1 SPI = 302D = 137.0.0.11 D = 434 lifetime = 60,000TTL = 1 COA = 9.2.20.11
HA = 129.34.78.254MA = 129.34.78.5
IP header fields UDP header Mobile IP message fields Authentication ExtensionForeign Home
S = 9.2.20.11 S = 1105 type = 1 SPI = 302D = 129.34.78.254 D = 434 lifetime = 60,000TTL = 64 COA = 9.2.20.11
HA = 129.34.78.254MA = 129.34.78.5
IP header fields UDP header Mobile IP message fields Authentication ExtensionHome Foreign
S = 129.34.78.254 S = 434 type = 3 SPI = 303D = 9.2.20.11 D = 1105 lifetime = 35,000TTL = 64 HA = 129.34.78.254
MA = 129.34.78.5
IP header fields UDP header Mobile IP message fields Authentication ExtensionForeign Mobile
S = 137.0.0.11 S = 434 type = 3 SPI = 303D = 120.34.78.5 D = 1094 lifetime = 35,000TTL = 1 HA = 129.34.78.254
MA = 129.34.78.5
77
Registering with a Collocated Registering with a Collocated COACOA
IP header fields UDP header Mobile IP message fields Authentication Extension
Home Mobile Registration Reply
S = 129.34.78.254 S = 434 type = 3 SPI = 303D = 129.34.78.5 D = 1094 lifetime = 35,000TTL = 64 COA = 9.2.43.94
HA = 129.34.78.254MA = 129.34.78.5
IP header fields UDP header Mobile IP message fields Authentication Extension
Mobile Home Registration Request
S = 129.34.78.5 S = 1094 type = 1 SPI = 302D = 129.34.78.254 D = 434 lifetime = 665,535TTL = 64 COA = 9.2.43.94
HA = 129.34.78.254MA = 129.34.78.5D, M, G, B = 1, 1, 1, 1
78
Deregistering at the Home NetDeregistering at the Home Net
IP header fields UDP header Mobile IP message fields Authentication Extension
Mobile Home
S = 129.34.78.5 S = 1094 type = 1 SPI = 302D = 129.34.78.254 D = 434 lifetime = 0TTL = 1 COA = 129.34.78.5
HA = 129.34.78.254MA = 129.34.78.5
IP header fields UDP header Mobile IP message fields Authentication Extension
Home Mobile
S = 129.34.78.254 S = 434 type = 3 SPI = 303D = 129.34.78.5 D = 1094 lifetime = 0TTL = 1 COA = 129.34.78.5
HA = 129.34.78.254MA = 129.34.78.5
IP header fields ICMP header Router Adv. fields Mobile Service Extension
Agent Advertisement
S = 129.34.78.254 type = 9 …… … no COAs …D = 255.255.255.255 code = 16 lifetime = 35,000H = 1
81
Encapsulation ProcessEncapsulation Process• The original IP header is modified
– protocol field in IP header is replaced by the number 55 for min encapsulation protocol
– the dest. Address field in the IP header is replaced by the IP address of the exit point of the tunnel
– if the encapsulator is not the original source of the datagram, the source address field in the IP header is replaced by the IP address of the encapsulator
82
Encapsulation Process ContEncapsulation Process Cont’’dd• The original IP header is modified
– the total length field in the IP header is incremented by the size of the minimal forwarding header added to the datagram
– the header checksum field in the IP header is recomputed or updated to account for the change in the IP header
83
IPIP--inin--IPIP
Original IP header Inner IP header Original IP Payload
Other Headers (Optional)
Original IP header Original IP Payload
Tunnel Endpoints
84
Minimal EncapsulationMinimal Encapsulation
Original IP header Original IP Payload
Original IP header Original IP Payload
Tunnel Endpoints Destination IP
Address
Minimal encapsulated header
85
Minimal Encapsulation Minimal Encapsulation Header FormatHeader Format
original destination address
(if present) original source address
protocol S reserved header checksum
0 1 2 30 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
(optional) S-bit=1 if “original source address” is presented
86
Generic EncapsulationGeneric Encapsulation
key (optional)
rsv Protocol type
0 1 2 30 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
RKC S s recur ver
Checksum (optional) offset (optional)
sequence number (optional)
routing (optional)
Delivery Header GRE Header Packet Payload
87
Routing FailureRouting Failure• Common
– Destination unreachable– Source quench– Redirect– Time exceeded
88
Tunnel ManagementTunnel Management• Tunnel soft state
– MTU size– TTL– Ability to reach the end of the tunnel
• ICMP errors– datagram too big– time exceeded– destination unreachable– source quench
89
Broadcast DatagramsBroadcast Datagrams• Colocated COA
• FA COA
IP Destination = Care-of Address Broadcast IP Datagram
Broadcast IP DatagramIP Destination = Care-of Address IP Destination = Mobile Host
90
ARPARP• Address Resolution Protocol• ARP protocol maps IP address to link-layer
address– Request/Reply
91
Gratuitous ARP by Home AgentGratuitous ARP by Home Agent
ARP Reply : Z_IP Z_MAC
HomeAgent X Y
Router
Z
ARP Reply : Z_IP HA_MAC
HomeAgent X Y
Router
(a)
(b) Gratuitous ARP to update X,Y’s ARP cache
Proxy ARP to reply ARP request
92
ARP operation: MN leaves homeARP operation: MN leaves home1. MN is away from home and decides to register
with FA– Movement detection
2. Before MN transmits registration request, MN disables its ARP processing
3. MN transmits registration request4. After HA receives and accept registration
request– HA performs gratuitous ARP on behalf of MN– Afterwards, HA uses proxy ARP to relay ARP
requests (which requesting MN’s link address)
93
ARP operation: MN returns homeARP operation: MN returns home1. MN decides to deregister its CoA2. Before MN transmits registration request, MN
enables its future ARP processing3. MN performs gratuitous ARP4. MN transmits registration request5. After HA receives and accept registration
request• HA performs gratuitous ARP on behalf of MN
• Both MN and HA perform gratuitous ARP to make sure that wireless nodes receive the message
• HA stops proxy ARP operation
95
IETF Mobile IPIETF Mobile IP• The exact ways in which the f, g and LD
functions are located in various nodes and networks distinguishes the various approaches
Mobile Host 2Source
f
LDHome Agent
Mobile Host 1
g
g
Home Network
S
Foreign Agent
Mobile Host, Using DHCP
96
Mobile IP with Route OptimizationMobile IP with Route Optimization
Mobile Host 2Source
f
LDHome Agent
Mobile Host 1
g
g
Home Network
S
Foreign Agent
Mobile Host, Using DHCP
f
Cache
97
Mobile IPv6Mobile IPv6
Mobile Host
Source
f
LDHome Agent
Home Network
S f
Cache
encapsulation
When LD cache entry is not available