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Mobile IP
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IntroductionIn the last few years the number of notebook users has been increased tremendously, due
to the great improvement in this technology with respect to size, speed, and weight. In
addition, most organizations depend on sophisticated networks that link their employees
with their PCs and workstations. Besides, telecommuters, mobile salespersons, and
other highly mobile individuals, are becoming part of a mobile workforce. The previousreasons motivate the need for mobile computers to communicate with other computers,
fixed or mobile.
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The requirements which drove the design of Mobile IP
1. A mobile node must be able to communicate with other nodes after changing its
Link-layer point of attachment to the Internet.
2. A mobile node must be able to communicate using only its home (permanent) IP
address, regardless of its current Link-layer point of attachment to the Internet.
3. A mobile node must be able to communicate with other computers that do not
implement the Mobile IP mobility functions.
4. A mobile node must not be exposed to any new security threats over and above those
to which any fixed node on the Internet is exposed.
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Design goals for Mobile IP
1. In order to make Mobile IP suitable for use over a wide range of wireless links, the size
and frequency of network routing updates should be small. To reach this goal all of the
protocol messages defined by Mobile IP consists of a small, fixed-length portion
followed by one or more extensions.2. Mobile IP protocol should be as simple as possible to be implemented. This increases
the number of nodes which can potentially make use of Mobile IP, especially memory
and processing-constrained devices such as pagers, smart cellular telephones, and
personal organizers, in addition to fully functional notebook computers.
3. Avoid solutions which require mobile node to use multiple addresses, or which require
large pools of addresses to be made available for use by mobile nodes, unless
absolutely necessary. This assumption makes mobile IP suitable to be implemented
over IPv4which has a limited set of available addresses. To make the Mobile IP
suitable for wide range of communication technology the size, number and frequencyof network routing updates should be small.
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Assumptions made by Mobile IP
1. Unicast packets destined to a single recipient should be routed based only upon the
IP Destination Address and typically only the network prefix portion of that address.
2. The Internet should be capable of delivering packets between any pair of nodes in thenetwork.
3. All Mobile IP requires an infrastructure of routers and links that is capable of routing
packets to any node which is connected to its home link.
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Mobile IP Terminology1. Agent Advertisement - an ICMP advertisement message with one or more extensions.
2. Care of Address - a care of address is an IP address associated with a mobile node whilevisiting a particular foreign link.
3. Correspondent Node - A peer with which a mobile node is communicating. A
correspondent node may be either mobile or stationary.4. Foreign Network - Any network other than the mobile nodes Home Network.
5. Home Address - An IP address that is assigned for an extended period of time to amobile node.
6. Link - A facility or medium over which nodes can communicate at the Link layer.
7. Link layer Address - The address used to identify an endpoint of somecommunication over a physical link.
8. Mobility Agent - Either a home agent or a foreign agent.
9. Mobility Binding- The association of a home address with a care of address, alongwith the remaining lifetime of that association.
10. Tunnel - The path followed by a datagram while it is encapsulated.
11. Visited Network - A network other than a mobile nodes Home Network, to which themobile node is currently connected.
12. Visitor List - the list of mobile nodes visiting a foreign agent.
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New Architectural EntitiesMobile IP introduces the following new functional entities:
1. Mobile Node - a node which can change its point of attachment to the Internet fromone link to another while maintaining any ongoing communications and using onlyits (permanent) IP home address.
2. Home Agent - a router with an interface on the mobile nodes home link which:
a. the mobile keeps informed of its current location, as represented by its care ofaddress, as the mobile node moves from link to link.
b. advertises reachability to the network-prefix of the mobile nodes home address,thereby attracting IP packets that are destined to the mobile nodes home address.
c. intercepts packets destined to the mobile nodes home address and tunnels them tothe mobile nodes current location.
3. Foreign Agent - a router on a mobile nodes foreign link which:
a. Assists the mobile node in informing its home agent of its current care of address.
b. In some cases provides a care of address and de-tunnels packets for the mobilenode that have been tunneled by its home agent.
c. Serve as a default router for packets generated by the mobile node while its isconnected to this foreign link.
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X
X
Arbitrary Topology
of Routers andLinks
X
Mobile node
visiting a foreignLink
Foreign LinkHome
Agent
Home Link
Mobile node
at home
Mobile IP entities and relationships
Foreign Link
Foreign Agent
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Summary of How Mobile IP works
The purpose of this section is to illustrate Mobile IP at a very high level.
A. Mobile agents advertise their presence on any attached link by periodically
multicasting or broadcasting special Mobile IP messages called Agent
Advertisement. Home agents and foreign agents periodically broadcast AgentAdvertisements which are received by all nodes on the link.
X
Mobile Agent
Host Host
Mobile
Node
Agent
Advertisement
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B. Mobile nodes listen to these Agent Advertisements and from the contents of thismessage it determines whether they are connected to their home link or a foreign
link. If it discovers that it is connected to the home link, then it acts as any
stationary node in this link, therefore, it does not use any mobile IP functionality.
Mobile nodes examine Agent Advertisements and determine whether they are
connected to this home or a foreign link.
IP Header
IPsrc = Agents Address
IPdst = Broadcast
IP protocol = ICMP
Agent Advertisement
FA Care of Address
Agent Advertisement
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C. A Mobile node connected to a foreign link acquires a care of address. A foreignagent care of address can be read from one of the fields within the foreign agents
Agent Advertisement. A collocated care of address must be acquired by some
assignment procedure, such as the Dynamic Host configuration Protocol (DHCP),
the Point to Point Protocols IP Control Protocol (IPCP), or manual configuration.
Mobile nodes connected to a foreign link obtain a care of address from the AgentAdvertisement.
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D. The mobile node registers the care of address acquired in step 3 with its homeagent using Registration Request. If the registration is granted by the Home
Agent it will send and Acceptance reply message to the Mobile Node, otherwise a
denial Reply message will be received by the Mobile Node from the Home Agent.
Mobile node registers its care of address with its Home Agent.
Home Link
Registration Reply
Arbitrary Topology of
Routers and LinksForeign Link
Foreign Agent Home Agent
Registration Request1
2
3
4
X X
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E. The home agent or some other router on the home link advertisers reachability tothe network prefix of the mobile nodes home address. The Home Agent will
send an ARP reply on behalf of the mobile node if it is attached to a Foreign Link
and it is receiving an ARP request from other nodes to identify its Data Link layer
Address. This type of ARP reply is called a proxy ARP. The Home Agent sends
a number of gratuitous ARPs to update the ARP caches for the other nodes whichstill have the original Data Link layer Address for the Mobile Node in their
caches. This Data Link layer Address will be substituted with the Data Link layer
Address of the Home Agent. When the Mobile node returns back to its Home link
it will send a number of gratuitous ARPs to update the ARP caches for other
nodes with its Data Link layer Address as opposed to the Data Link layer of HomeAgent. Home agent or other router advertisers reachability to mobile nodes Home
Address.
Router
Router
Home Agent
Routing Update
I can reach all destinationswith network - prefix equal
to mobile nodes home
address.X
X
X
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F. The Home Agent will intercept any packets sent to the mobile node.
Home Agent
Home LinkX
X
Host
Router
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G. The Home Agent tunnels the intercepted packets and send them to the Mobile
node care of address.
Foreign Agent removes original packets from the tunnel and delivers the original
packet to the mobile node over the foreign link.
XX
Mobile
Node Foreign Agent Home Agent
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H. If the mobile node wants to send packets, they will be sent directly to theirdestination without the need for tunneling. The foreign Agent serves as a router
for all packets generated by a visiting mobile node.
XX
Mobile
Node Foreign Agent Home Agent
Correspondent
Node
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What is agent discovery?
1. Determine Mobile Node if it is connected to foreign or home link.
2. Determine Mobile Node if it is moved from one link to another link.
3. Obtain a care of address if it is connected to foreign link.
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What Messages Comprise Agent Discovery?
Agent Advertisement
It is a message sent periodically as a multicast or broadcast message to each link
the Mobile Agent Node is configured to perform as Home Agent, Foreign Agent
or both. It is identical to ICMP router advertisement with IP time to live equal 1.
Agent Solicitation
When a Home Agent or Foreign Agent receives one, it should immediately
respond by transmitting an Agent Advertisement. Agent Solicitations are
identical to ICMP Router Solicitations, with IP time to live equal 1.
The IP header of an agent advertisement is used by the mobile node to
determine whether it is connected to its home link or a foreign link.
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Vers = 4 IHL Type of Service Total Lengthidentification Flags Fragment offset
Time to Live= 1 Protocol= ICMP Header check sum
Source Address = Foreign Agent IP Address
Destination = 255.255.255.255 (broadcast) or 224.0.0.1 (multi)
Type = 9 code check sum
Num addresses Address entry size Line time of this advert
Router Address (1)
Preference Level (1)
Router Address (2)
Preference Level (2)
Type = 16 Length Sequence #
Registration Lifetime R B H F M G V rsd
Care of address (1)
Care of address (2)
Type - 19 Length Prefix 1 Prefix 2
IP Header
(RFC791)
ICMP Router
Advertisement
(RFC1256)
Mobility Agent
Advertisement
Extension
(RFC2002)
Prefix-Length
Extension
(RFC2002)
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Vers = 4 IHL Type of Service Total Length
identification Flags Fragment offset
Time to Live= 1 Protocol= ICMP Header check sum
Source Address = mobile nodes home address
Destination = 255.255.255.255 (broadcast) or 224.0.0.1 (multi)
Type = 10 code=0 check sum
IP Header
(RFC791)
ICMP Router
Advertisement
(RFC1250)
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Agent Advertisement = receive Agent Advertisement ( )
srcIP address = receive SrcIP address (agent Advertisement)
Has Mobile Node
moved?
COA = get COA (agent Advertisement)
Register Home Agent (COA, Mobile Node Home
Address)
Mobile Node Deregister with Home Agent ( )
Home Agent sends gratuitous ARPs to update
nodes caches on the Home Link
Mobile Node location detection
NO NO
YES (Node in Home
Link)
NO (Node in
Foreign Link)
YESYES
Has Mobile Node
moved?
Network Prefix (SrcIP address = =
Network Prefix (Mobile Node Homeaddress)
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How Does a Mobile Node Determine That It Has Moved
Move Detection Using Lifetime
The first method uses the Lifetime field within the ICMP router advertisement portion
if an Agent Advertisement. This field effectively tells the mobile node how soon it
should expect to hear another advertisement from the same agent. If a mobile node is
registered with a foreign agent, and fails to hear an advertisement from that agent
within the specified lifetime, then the Mobile node assumes that it has moved to a
different link or that its foreign agent is broken.
Move Detection Using Network Prefix
In this method we assume that the mobile node is registered with a foreign agent on
some link and has recorded the Agent Advertisement by which it discovered that
foreign agent. To determine whether two advertisements were received on the same
link, the mobile node computes the network prefix(es) of the respective
advertisements, and the recorded advertisement. If those network prefix(es) are
equal, so the node doesnt move otherwise it is moved.
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Lifetime = get Lifetime (Agent Advertisement)
wait for lifetime period
We receive Agent
Advertisement and
Lifetime for the
current Agent
Advertisement
not equal to the
old Lifetime for
the old Agent
Advertisement
We did not
receive Agent
Advertisement
at Lifetime period
We receive Agent
Advertisement at
exactly Lifetime period
Moved
Send AgentSolicitation
get Agent
solicitation
moved Foreign Agent
is broken
yes no
error
Not Moved
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Recorded Net Prefix = get Sub-network Prefix (recorded Agent Advertisement
New Agent Advertisement = get Agent Advertisement ( )
Move Detection Using Network Prefixes
NO
YES
New Net Prefix = get Sub-network Prefix (new Agent Advertisement)
Length (recorded Net Prefix) = =
length (new Net Prefix)
i = 0
i < length (newNet Prefix)
YES
YES
i = i + 1
Recorded Net Prefix [ i ] = =
new Net Prefix [ I ]
YES
NOTMOVED
NO
MOVEDNO
MOVED
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Mobile Node Registration
Mobile node registers with its Home Agent in the following situation:
a. whenever it detects that its point of attachment to the network has changed fromone link to another.
b. when its registration time has expired.
The Registration process includes the following tasks
1. Get a care of address from the Foreign Agent.
2. Inform its home agent of its current care of address.3. Renew a registration when it is about to expire.
4. Deregister when it returns to its home link.
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Message Comprise Registration
The registration process consists of the exchange of two messages: a Registration
Request and a Registration Reply. Registration messages are carried in a Data
Portion of a UDP packet.
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IHL Type of Service Total Length identification Flags Fragment offset
Time to Live= 1 Protocol= UDP Header check sum
Source Address
Destination address
Source Port Destination Port = 434
Length Check sum
Type=1 S B D M G Y res Lifetime
Mobile Nodes Home Address
Home Agent Address
Care of Address
Optional Extension
Type = 32 Length Security Parameter
Index (SPI)
Authentication (Default equal keyed MD5)
IP Header
(RFC791)
Registration Request Message
UDP Header
(RFC768
Fixed length portion
of Registration
Required
(RFC2002)
Mobile Home
Authentication
Extension
(RFC2002)Mandatory
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Registration Reply
Type = 3 Code Lifetime
Mobile Nodes Home Address
Home Agent Address
Identification
Fixed length
portion of
Registration
Reply (RFC2002)
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Registration Scenarios
The purpose of registration is for the mobile node to inform its Home Agent of its
current care of address(es), the address(es) to which the Home Agent will tunnel
packets forwarded to the mobile node. The Home Agent will construct a table of
binding entries, as a result of this registration process, each entry has a Mobile Node
Home address and care of address. There are three scenarios of registration process:
1. A mobile node registers on a foreign link using a Foreign Agent care of
address.2. A mobile node registers on a foreign link using a collocated care of address
(perhaps because no foreign agent is present on a Foreign Link).
3. A mobile node deregisters upon returning to its home link.
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MKIPM001
IP
Header
UDP
Header
Link Layer
HeaderSource Address = mobile modes Link Layer Address
Destination Address = copied from Foreign Agent Advertisement
Source Address = Home Address IP
Destination Address = Foreign Agent IP
Source Port = anything
Destination Port = 434
Registration
Request
B = 1 if mobile mode want a copy of broadcast OM Home Link
D = o, tell the HA that the Foreign Agent is doing encapsulation
Mobile Nodes IP Home Address
Home Agent IP Address
Copied from a Foreign Agent Advertisement
Life Time
Registration Reply
Registration Request
Foreign LinkForeign Agent Home Agent
1 2
34
MobileNode Home Link
Fields of Registration Request as set by Mobile Node forForeign Agent care of Address
Arbitrary Topology of
Routers and LinksX X
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Link Layer
Header
IP
Header
Source Address = mobile nodes Link Layer Address
Router Address = Select Router in Foreign Link without FA ( )
Destination Address = ARP (COA, Router Address)
Source Address = cane of Address
Dst Address = Home Agent IP Address
Registration
Request
Dst Port = 434
B = 1 if a mobile node want a copy of broadcast on Home Agent
D=1 Tell the Home Agt. that the mobile node is doing decapsulation
Mobile Nodes IP Home Address
Home Agent IP AddressCollocated care of address
Source Port = anything
Life Time
Foreign LinkHome Agent
Registration Request
Registration Reply
Home LinkArbitrary Topology of
Routers and Links
X
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Link Layer
HeaderSrc Address = mobile node Link Layer Address
Dst Address = ARP (Home Agent IP Address)
Src Address = Mobile Node IP AddressIP
Header Dst Address = Home Agent IP Address
Mobile Node Home IP AddressRegistration
Request Home Agent IP Address
mobile node Home Address
Life Time = 0
Fields in Deregistration Request as set by Mobile Node
Home LinkHome Agent
deregistration request
deregistration reply
Arbitrary Topology of
Routers and Links
X
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How Does a Foreign Agent Process a Registration Request
We assume that we are registering through the Foreign Agent. When the foreign
agent receives the Registration Request it applies a sequence of validity checks. If
any of them fails it send a Registration Reply with the cause of the failure.
Otherwise, it consumes the IP and UDP header, constructs new IP and UDP headerscontaining the original Registration Request, and sends it to the home agent.
How Does a Home Agent Process a Registration Request
When a Home Agent receives a Registration request, it applies a set of validity
checks. If it is invalid, the Home Agent sends a Registration Reply to the MobileNode with error code defining the problem. If it is a valid Registration Request then
the Home Agent updates the binding entry according to the specified care of address,
Mobile node Home Address, Lifetime, and S field.
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reg Request = Read Registration Request From Mobile Node ( )
Authentication Field Registration Reply ( )
invalid
Lifetime > maximum
validyes
Sufficient Resourcesto handle
Mobile Node
no
Registration Reply ( )
no
Type of Tunnelingis supported Registration Reply ( )
yesno
Payload = get Pay Load (reg Request)
Src Address = Foreign Agent IP address
Dst Address = Home Agent Field of Registration Request
Construct Packet (Src Address,Dst Address, payload)
Send Packet
How Foreign Agent Process a Registration Request
Registration Reply ( )
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big problem
registration Req = get Registration Request ( )
AuthenticationInvalid
Registration Reply ( )
Sufficient Resources Registration Reply ( )
validNoCreate a Binding
for the specified
care-of Address
leaving any existingBinding unmodified
Care of Address= = home Address
LifeTime > 0S = = 0
No
Replace all the mobile
node existing bindingwith new binding
for the specified
care of address
YesS = = 1 Delete all the
mobile node
Binding
LifeTime = = 0
Delete the mobile node binding for the
specified care of address leaving the
rest untouched
Yes
No
Successful Registration Reply ( )Send Gratuitous ARPs
Yes
Yes
No
Yes
No
No
How Does a Home Agent Process A Registration Request
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registration Reply = get Registration Reply ( )
Src Addr = Data Link for Foreign Agent )
Dst Addr = stored Data Link Address for Mobile Node
Src Addr = IP address for Foreign Agent
Dst Addr = stored IP address for Mobile Node
Src Port # = Any
Dst Port # = stored Port #
Valid Reply
How Does a Foreign Agent Process a Registration Reply
NO YES
update Reply code with the error
transmit Reply to Mobile Node
Payload = get Payload (registration Reply)
Update list of Visiting Mobile Node
transmit Reply to Mobile Node
Link Layer
Header
IP
Header
Registration
Reply
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How Does a Foreign Agent Process a Registration ReplyWhen the foreign agent receives the reply, it applies a validity check for the reply. If
the reply is invalid because it contains an unrecognized extension, or fails home-
agent-to foreign-agent authentication then the foreign agent forms another reply with
the proper error code and relays the new reply to the Mobile Node. If it is valid then
it relays the reply to the Mobile Node using some of the fields which has recordedduring registration Request.
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IPsrc = Original SenderIPdst = Ultimate Destination
original IP packet Header payload
Header payloadOuter Header
IPsrc = Tunnel Entry-Point (Home Agent)
IPdst= Tunnel Exit-Point (care of address)
Encapsulating IP Packet
IP Tunneling
A tunnel from a
home agent to aforeign agent
Home Agent
XX
Mobile
Node Foreign Agent
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X X
Foreign Link
Arbitrary Topology of
Routers and Links
Foreign Agent
Mobile Node
Home Agent
Home Link
Correspondent Node
How Packets are Routed when a Mobile Node is at Home
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X X
Mobile Node
Correspondent Node
Foreign Link Home Link
Foreign Agent Home Agent
Arbitrary Topology 01
Router and Links
How Packets are Routed when a Mobile Node is at Foreign Link and Correspondent
Node is sending Packets to Mobile Node
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X X
Mobile Node
Foreign Agent
Foreign Link Home Agent
Home Agent
Correspondent Node
Arbitrary Topology of
Routers and Links
How Packets are Routed when a Mobile Node is at Foreign Link and Mobile
Node is sending Packets to Correspondent Node
bil
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X X
Mobile Node
Foreign Link Home Link
Foreign Agent Home Agent
Correspondent Node
Arbitrary Topology of
Routers and Links
How Packets are Routed when a Mobile Node is at Foreign Link and Correspondent Node is
sending Packets to Mobile Node in case of collocated Care of Address
Using Routing Header
M bil IP
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Src Addr 255.225.285.255 Data
network prefix.111.
Home Agent COA
IP
Receiving a Broadcast Message with a Foreign Agent Care of Address
The Mobile node should instruct the Home Agent to deliver a copy of all broadcast
messages by setting the B=1. Also, it instructs the Home Agent that the foreign Agent
will do the de-capsulation process. The Home Agent will use nested encapsulation to
deliver broadcast packets to mobile node. The encapsulated packet forwarded to theForeign Agent is formed as follows:
When the Foreign Agent receives this packet it will remove, decapsulate a unicase packetwhose destination address is the Mobile Node Home address. The resulting Unicast
message will be decapsulated again and the Routing Algorithm will send the resulting
broadcast packet to the Mobile Node.
Home
Agent
Mobile
Node IP
M bil IP
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Src Addr 255.255.255.255. Data
Home Agent COA
IP IP
Mobile Nodes Receiving Broadcast messagesThe destination address for the broadcast message is in the form of network-prefix
.11.11 (prefix-specific broadcast or 255.255.255.255) (link specific broadcast).
The delivery mechanism depends upon whether the mobile node is using Foreign Agent
care of address or collocated care of address.
Receiving a Broadcast Message with a Collocated care of address
The Mobile Node should instruct the Home Agent to deliver a copy of all broadcast
messages by setting the B-1. Also, it should instruct the Home Agent that it will do thedecapsulation by setting the process D bit. The encapsulated packet sent by the Home
Agent is formed as follows:
M bil IP
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Src Addr 255.255.255.255 Data
Mobile Node Home Agent
Home Address address
The resulting packet will be routed to the Home Agent.
Sending Broadcast Message by Mobile Node
There are three types of broadcast message which are sent by the Mobile Node
a. If the destination broadcast address is a link-specific broadcast (255.255.255.255)
intended for the Foreign Link, then Mobile node will use the data link broadcast
Address to deliver this packet to all nodes in the Foreign Link.
b. if the destination broadcast address is a link-specific broadcast (255.255.255.255)
intended for the Home Link, then the Mobile Node should encapsulate this broadcast
message as follows:
Mobile IP
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MKIPM001
Internet
Normal Registration Scenario - 1 (IPv4)
GTE.comNortel.com
RAS
EmadRuss
Firewall Firewall Wireless
PPP
Not explicitly specified in MIP (RFC2002)
MN DS MNHA FA1Agent Advertisement
4 User profile lookup3Reg Req.
5
2 Reg Req
Reg ReplyReg Reply
8
76
Startses
sion
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DS MNHA FA1Age
ntAdv
2Agent
Solicitatio
n
AgentAdv
Wait for agent
Adv.
RegReq. 4RegR
eq
3
5
7
6
8 9
10
RegReq. RegReq.
Registration Scenario - 2 (IPv4) MNdoes not rcv advertisement
x
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Registration Scenario - 3 (IPv4)
MN does not rcv advertisementMN does not rcv response for solicitation
MNDS FADCHPHA
RegReq. 8RegReq
10
12
11
13
14
RegReq. RegReq.
Wait for agent adv
Wait for agent advWait for rtrn adv.
No response from
agent
xAgentAd
v
5
4
3
21
7
6
x
x
AgentSolic
AgentSoli
c
QueryDHCP
ReqIPaddrfromD
HCP
DHCPresponses
ReplyfromDHCPwithIP(COA)
9
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Registration Scenario - 4 (IPv4)
HOME AGENT DISCOVERYMN does not rcv adv.
MN does not rcv response for solicitationMNFADCHPHA-1
5
4
3
21
7
6
x
x
AgentSo
licAgen
tSolic
QueryDHCP
ReqIPaddrfromD
HCP
DHCPresponses
ReplyfromDHCPwithIP(COA)
RegRep.8Reg
Req10
12
1113
14
RegRep. RegReq.
AgentAdv
HA-2HA-3
RegReq(BCAST,MCA
ST)
RegReqrejectingregRCPrej
9
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ISPISP
FA
InternetInternet
InternetInternet
InternetISP
HA
Data Routing Scenarios
ISP
FA
MNCN
CN
Internet
HAMN
MN
HA by -passed for optimization
CN
ISPs
ISP FA
HA, FA are by-passed
Normal routing with FA, HA involvement
ISP HA
MNCN
IPv6
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Russ, Emad, Al and Leo must have a video conference.
Russ mobile registers in France.
- How does the VLR fetch Russ profile?
- How does GGSN interface to the Internet?
- What address should Russ use to conference others?
Emad has the same issues in Mexico.
Leo is Calgary in his hotel room and would have similar issues as Russ and Emad.
Al dials up using ISDN from home.
How would Russ, Emad, Al and Leo have a real-time video conference?
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SGSN
MPNMPN
GSN/UMTS
France
GGSN
Russ
Internet
Nortel.com
AOL ISP MIP
Slip
Dialup
NAC
MexicoIWF
IP
Wireless
PPP
3G 2GWireless
PPP
Emad
Calgary
Ottawa
ISDN
Dialup
HA
Leo
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Interface Option-1
- 2G system is similar; however, IWF replaces SGSN & GGSN
- Calgarys interface is already MIP compatible.
SGSN HLRIVLR GGSN MPN HA/HAD DS
France IP Network Nortel
MN
MN 1 2
3
4
6
7
10 9
5
8
Current 3G Loc
up Response3G Reg. Resp.
3G Reg. Req.
3G Loc up Resp
3G Loc update IP Hdr 3G Loc update
IPResolve user profile
Create content
Tunnel
Tunnel
Convert to MIP
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- 3G & 2.5G
Place MIP elements such as FA, HA at SGSN, GGSN & IWF
Adv.
- Eliminate the MPN passthrough function- Eliminate the protocol conversion at the HA/HAD
- Unify network mobility across different platforms
Dis.
- All infrastructures have to incorporate MIP components.
- MIP is not mature for real time commercial systems.
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MIP Signaling Issues
IP Network
HA FA
In MIP Registration
procedure is repeated
during handoff to inform
HA of new location
MN
1
3
2Dropped in the network due to
congestion
X
XDropped due to congestion
RegReq
RegReq
- Today IP network does not provide any preference for MIP/signaling messages?
- congestion can cause latency
- normal conditions also may cause latency
- Therefore, unpredicted impact on handoff latency.
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ICMPv6 Router Discovery
ICMPv6Router Discovery consists of two Messages:
a. Router Advertisement Message:
Routers Transmit router Advertisement Message on a periodic basis - or in responseto a hosts Router Solicitation on message. The source address is the address of thesenders interface and the destination is the source address of an invoking RouterSolicitation, or the all-nodes multicast address.
b. Router Solicitation Message:
The Router Solicitation Message is transmitted by a host to prompt routers to generateRouters Advertisement massage quickly. The source address defines the sendinginterface address and the destination is all-routes multicast address.
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Home Agent List
Binding Update List (maintained by each mobile node)
Binding Cache (maintained by each IPv6node)
Lifetime
Lifetime
Home Agent IP Address
Care of Address
Care of Address Lifetime Value
IP address for node
Mobile Node Home Address Max sequence #
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Vers = 6 prio=ls Flow Label
payload length next header=58 Hop limits
Source address-router or home agents address
Destination address=mobile nodes address or All-Nodes Multicast Address
Type=134 code=0 check sum
current Hop Limit M O reserve Router lifetime
Reachable Time
Retransmission Times
Type=3 Length=4 Prefix Length Reserved
valid lifetime
preferred lifetime
Reserves 2
Network Prefix
IPMv6Header
(RFC 1883)
IPv6Router
Advertisement
(Fixed Portion)
RFC 1970
Prefix
information
option
RFC1970
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Vers = 6 prio=l5 Flow Label
payload length=8 (_______) next header=58 Hop limits
Source address= the Mobile Nodes unicast address
Destination address=the All-router Multicast Address
Type=133 code=0 check sum
reserved
IPv6Header
(RFC 1883)
ICMPv6Router
solicitation (RFC
1970)
ICMPv6Router Solicitation
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Location Detection
The mobile node examines the network prefix contained in the received advertisementagainst its home address network prefix. If there is a match then the mobile node isconnected to its Home Link, otherwise it is connected to a foreign link.
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Router Advertisement=get Router Advertisement ( )
Network Prefix = get Network Prefixes (router Advertisement)
i = o
Location Detection Algorithm
Moved
Moved
i< length
(network
Prefixes)
Network Prefixes [i]= = network
Prefix [mobile Node Home
Address]
i = i+1
Deregister ( )
Coa=get Care Of Address ( )
Register with Home Agent ( )YES
YES
YES
YES
NO
NO
NO
NO
(connected to
foreign Link)
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Motion Detection Algorithm
Old Network Prefixes=get Network Prefixes (old Router Advertisement
New Router Advertisement=get Router Advertisement ( )
Moved
Moved
New Network Prefixes=get Network Prefixes (new Router Advertisement
size of (new Network Prefixes) = =
size of (old Network Prefixes)
i=0
i < size of (new
Network Prefix)
i=i+1Not
MovedNew Network Prefixes [i]= =
old Network Prefixes [i]NO
NO
NO
YES
YES
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Movement Detection:
The mobile node checks the most recent set of network Prefixes with those set of networkprefixes belongs to previous Router Advertisements.
How Does a Mobile Node Obtain A Care of Address
One the Mobile node detected that it has moved, it will acquire a new care of address by oneof two methods. The M=1 in the Router Advertisement message informs the Mobile Nodethat it will use Stateful Address Auto configuration method otherwise it will use StatelessAddress Auto. An example for stateful address assignment is the dynamic Hostconfiguration Protocol (DHCP) for IPv6which is similar to Dynamic Host Configuration
Protocol in IPv4.
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The stateless Address Auto configuration is a method to acquire care of addressautomatically or without server. There is no functionality similar to this functionality in IPv4.
This method works as follows:
1. Acquire the interface token which is similar to data link layer address for the networkinterface. For example the network interface address for Ethernet is 98 bits.
2. Get the Network Prefix for the current link from the prefix Information Optioncontained in the Router Advertisement.
3. Concatenate the interface token with the network prefix to form a care of address. Inorder to proof the uniquenin of a generated address a Neighbor Solicitation message istransmitted with the generated address as the target address. If another node is usingthis address a Neighbor Advertisement Message will be returned. In this event, autoconfiguration stops and some manual intervention is required.
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Acquiring Care of Address
M=1YES NO
Done
Done
Coa=get COA from DHCP ( )
Address is unique
Interface Address=get Interface Address ( )
Network prefix=get link Network Prefix ( )
Transmit Neighbor Solicitation (COA)
Coa=merge (interface Address, Network Prefix)
Wait for Neighbor Advertisement
Address is not unique, Manual
Intervention is required
Not Received
Received
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Registration
In IPv4the mobile node informs its Home Agent about its care of address throughRegistration Request and Registration Reply message. These Registration Request andReply are carried in the payload of UDP/IP packet. In IPv6 the Mobile Node informs the
Home Agents and various other nodes about its care of address using the DestinationOptions. When the Mobile node obtains its care of address it informs it Home Agent aboutthis care of address. The Home Agent will use this care of address as an exit point of thetunnel to get back to the mobile agent. The mobile node also informs a set of correspondentnodes of its current care of address, which will be used by the correspondent nodes to route
packets directly to mobile nodes. Messages which are involved in Registration are:
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1. Binding Update - this message is sent to the Home Agent or the correspondent nodes toinform them about its care of address. The A bit is set by the mobile node to inform thereceiver of the option should send Binding Acknowledgement. The H bit is set by themobile node to inform the recipient that the mobile node wishes it to serve as a Home
Agent. The L bit is set by the mobile node to receive packets destined not only to itsglobally routable home address but also to its link local Home Address.
2. Binding Acknowledgement - a binding acknowledgement message is sent by the HomeAgent or correspondent node to indicate that it has successfully received the MobileNode Binding Update.
3. Binding Request - a binding request is sent to a mobile node by a correspondent node torequest that the mobile node sent Binding Updates. This is useful when Lifetime in anoriginal Binding Update is near expiration and the correspondent node has reason tobelieve that it will continue to send packets to the mobile node.
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Ver=6 prio Flow label
payload length next header=51 Hop Limit
Source Address=mobile nodes globally routable home address
Destination Address=Home Agent or correspondent node
next header=60 length=9 RESERVEDSecurity Parameters Index (SPI)
Authentication Data
next header Hdr Ext len option type=16 option length
A H L Reserved Lifetime
Identification
Mobile Nodes Home Address
care of Address
Mobile Nodes Link Local Home Address
(only present if L bit equal 1)
IPv6Payload (if this Binding Update is being piggy backed)
Binding Update
IPv6Header
(RFC 1883)
Authentication
Header for IVv4 and
IPv6(RFC 1820)
Destination option
header RFC 1883
containing IPv6
Binding UpdateOption
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Binding Acknowledgement
Ver=6 prio Flow label
payload length next header=51 Hop Limit
Source Address=home Agent or Correspondent node
Destination Address=mobile nodes home address (or care of address)
next header=60 length=9 RESERVEDSecurity Parameters Index (SPI)
Authentication Data
next header Hdr Ext len option type=193 option length
Status Refresh Lifetime
Identification
Mobile Nodes Home Address
IPv6 Payload (if this Binding Acknowledgement is being piggy backed)
IVv6 Header
(RFC 1883)
Authentication Headerfor IPv4 and IPv6 (RFC
1826)
Destination option header
RFC 1883 containing the
Mobile IPv6 Binding
Acknowledgement Option
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Vers=6 Prio Flow label
payload length next header=60 Hop Limit
Source Address=home agent or correspondent node
Destination Address=mobile node home address (or care of address)
next header Hdr Ext Len Option Type=199 Option length=0
IPv6 Payload (if this Binding Request is being piggy backed
Binding Request
IPv6 Header
(RFC 1883)
Destination Option Header
(RFC 1883) containing the
Mobile IPv6 Binding
Request Option
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Binding Update
1. A mobile node connects to the Foreign Link and informs its home agent of its new care of address
2. A mobile node connects to a Foreign link and informs a correspondent node of its new care of address
Foreign LinkHome Agent
X
Home Link
Mobile Node
Binding Acknowledgement
X
Home Link
Home AgentForeign Link
Binding Acknowledgement
Binding Update
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Binding Update
X
Home LinkHome Agent
Binding Acknowledgement
3. A mobile node returns to its home link and informs its home agent that it is no longer attached to a foreign
link
Correspondent
Node
X
Home Agent
Home Link
Foreign Link
Mobile Node
4. The correspondent node requesting an update for the Mobile Node care of address when the Lifetime is an
original Binding Update near expiration.
Binding Request
Binding Update
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Visiting list kept by Foreign Agent
Binding list kept by Home Agent
Mobile IP address
Mobile IP address
Care of Address
Care of Address
Lifetime
LifetimeData Link layer address Port #
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Vers=6 prui Flow label
payload length next header=43 Hop limit
Source Address=correspondent Node Address
Destination Address=mobile nodes care of address
next header=6 Hdr Ext Len=2 Routing type=0 segments left=1
Reserved strict/loose bit map=all 0s
Address [i] = mobile nodes home address
tcp header and user date
Source-Routed Packet from Correspondent Node to Mobile Node
IPv6Header
(RFC 1883)
IPv6Type 0
Routing Header
(RFC 1883)