Mobile IP
Introduction
In 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 PC’s and workstations. Besides, telecommuters, mobile salespersons, and
other highly mobile individuals, are becoming part of a mobile workforce. The previous
reasons motivate the need for mobile computers to communicate with other computers,
fixed or mobile.
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Mobile IP
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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Mobile IP
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 IPv4 which has a limited set of available addresses. To make the Mobile IP
suitable for wide range of communication technology the size, number and frequency
of network routing updates should be small.
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Mobile IP
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 the
network.
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
Mobile IP Terminology
1. 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 while
visiting 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 node’s Home Network.
5. Home Address - An IP address that is assigned for an extended period of time to a
mobile 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 some
communication 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, along
with 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 node’s Home Network, to which the
mobile node is currently connected.
12. Visitor List - the list of mobile nodes visiting a foreign agent.
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Mobile IP
New Architectural Entities
Mobile IP introduces the following new functional entities:
1. Mobile Node - a node which can change its point of attachment to the Internet from
one link to another while maintaining any ongoing communications and using only
its (permanent) IP home address.
2. Home Agent - a router with an interface on the mobile node’s home link which:
a.
the mobile keeps informed of its current location, as represented by its care of
address, as the mobile node moves from link to link.
b.
advertises reachability to the network-prefix of the mobile node’s home address,
thereby attracting IP packets that are destined to the mobile node’s home address.
c.
intercepts packets destined to the mobile node’s home address and tunnels them to
the mobile node’s current location.
3.
Foreign Agent - a router on a mobile node’s 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 mobile
node that have been tunneled by its home agent.
c.
Serve as a default router for packets generated by the mobile node while its is
connected to this foreign link.
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Mobile IP
Mobile node
visiting a foreign
Link
Mobile node
at home
Foreign Agent
X
Home
Agent
Foreign Link
Arbitrary Topology
of Routers and
Links
X
Home Link
X
Foreign Link
Mobile IP entities and relationships
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Mobile IP
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 Agent
Advertisements which are received by all nodes on the link.
Mobile
Node
Mobile Agent
Agent
Advertisement
X
Host
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Mobile IP
B. Mobile nodes listen to these Agent Advertisements and from the contents of this
message 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 = Agent’s Address
IPdst = Broadcast
IP protocol = ICMP
Agent Advertisement
FA Care of Address
Agent Advertisement
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Mobile IP
C. A Mobile node connected to a foreign link acquires a care of address. A foreign
agent care of address can be read from one of the fields within the foreign agent’s
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 Protocol’s IP Control Protocol (IPCP), or manual configuration.
Mobile nodes connected to a foreign link obtain a care of address from the Agent
Advertisement.
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Mobile IP
D. The mobile node registers the care of address acquired in step 3 with its home
agent 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.
Registration Request
1
2
X
Foreign Link
X
Arbitrary Topology of
Routers and Links
Foreign Agent
3
4
Home Link
Home Agent
Registration Reply
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Mobile IP
E. The home agent or some other router on the home link advertisers reachability to
the network prefix of the mobile node’s 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 which
still 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 Home
Agent. Home agent or other router advertisers reachability to mobile node’s Home
Address.
X
Routing Update
Router
X
X
Router
Home Agent
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I can reach all destinations
with network - prefix equal
to mobile node’s home
address.
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Mobile IP
F. The Home Agent will intercept any packets sent to the mobile node.
Host
X
Home Link
X
Home Agent
Router
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Mobile IP
G. The Home Agent tunnels the intercepted packets and send them to the Mobile
node care of address.
Mobile
Node
Foreign Agent
Home Agent
X
X
Foreign Agent removes original packets from the tunnel and delivers the original
packet to the mobile node over the foreign link.
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Mobile IP
H. If the mobile node wants to send packets, they will be sent directly to their
destination without the need for tunneling. The foreign Agent serves as a router
for all packets generated by a visiting mobile node.
Correspondent
Node
Mobile
Node
Foreign Agent
Home Agent
X
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Mobile IP
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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Mobile IP
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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Mobile IP
Vers = 4
IHL
Type of Service
identification
Time to Live= 1
Total Length
Flags
Protocol= ICMP
Fragment offset
Header check sum
IP Header
(RFC791)
Source Address = Foreign Agent IP Address
Destination = 255.255.255.255 (broadcast) or 224.0.0.1 (multi)
Type = 9
Num addresses
code
check sum
Address entry size
Line time of this advert
Router Address (1)
Preference Level (1)
ICMP Router
Advertisement
(RFC1256)
Router Address (2)
Preference Level (2)
Type = 16
Length
Sequence #
Registration Lifetime R B H F M G V rsd
Care of address (1)
Mobility Agent
Advertisement
Extension
(RFC2002)
Care of address (2)
Type - 19
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Length
Prefix 1
Prefix 2
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IP10
Prefix-Length
Extension
(RFC2002)
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Mobile IP
Vers = 4
IHL
Type of Service
identification
Time to Live= 1
Total Length
Flags
Protocol= ICMP
Fragment offset
Header check sum
Source Address = mobile node’s home address
Destination = 255.255.255.255 (broadcast) or 224.0.0.1 (multi)
Type = 10
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code=0
IP Header
(RFC791)
check sum
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IP10
ICMP Router
Advertisement
(RFC1250)
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Mobile IP
Agent Advertisement = receive Agent Advertisement ( )
srcIP address = receive SrcIP address (agent Advertisement)
Network Prefix (SrcIP address = =
Network Prefix (Mobile Node Home
address)
NO (Node in
Foreign Link)
NO
YES (Node in Home
Link)
Has Mobile Node
moved?
Has Mobile Node
moved?
YES
NO
YES
Mobile Node Deregister with Home Agent ( )
COA = get COA (agent Advertisement)
Register Home Agent (COA, Mobile Node Home
Address)
Home Agent sends gratuitous ARPs to update
nodes caches on the Home Link
Mobile Node location detection
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Mobile IP
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 doesn’t move otherwise it is moved.
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Mobile IP
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
yes
Moved
moved
We did not
receive Agent
Advertisement
at Lifetime period
We receive Agent
Advertisement at
exactly Lifetime period
Send Agent
Solicitation
Not Moved
no
get Agent
solicitation
Foreign Agent
is broken
error
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Mobile IP
Recorded Net Prefix = get Sub-network Prefix (recorded Agent Advertisement
New Agent Advertisement = get Agent Advertisement ( )
New Net Prefix = get Sub-network Prefix (new Agent Advertisement)
Length (recorded Net Prefix) = =
length (new Net Prefix)
YES
i=0
NOT
MOVED
NO
NO
MOVED
YES
i < length (new
Net Prefix)
YES
Recorded Net Prefix [ i ] = =
new Net Prefix [ I ]
i=i+1
YES
NO
MOVED
Move Detection Using Network Prefixes
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Mobile IP
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 from
one 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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Mobile IP
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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Mobile IP
IHL
Type of Service
identification
Time to Live= 1
Total Length
Flags
Protocol= UDP
Fragment offset
Header check sum
IP Header
(RFC791)
Source Address
Destination address
Source Port
Destination Port = 434
Length
Type=1
Check sum
S B D M G Y res
Lifetime
Mobile Node’s Home Address
Home Agent Address
UDP Header
(RFC768
Fixed length portion
of Registration
Required
(RFC2002)
Care of Address
Optional Extension
Type = 32
Length
Security Parameter
Index (SPI)
Authentication (Default equal keyed MD5)
Mobile Home
Authentication
Extension
(RFC2002)
Mandatory
Registration Request Message
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Mobile IP
Type = 3
Code
Lifetime
Mobile Node’s Home Address
Home Agent Address
Fixed length
portion of
Registration
Reply (RFC2002)
Identification
Registration Reply
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Mobile IP
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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Mobile IP
Mobile
Node
1
Registration Request
Arbitrary Topology of
Routers and Links
X
Foreign Link
4
Foreign Agent
2
Home Link
X
3
Home Agent
Registration Reply
Link Layer
Header
IP
Header
UDP
Header
Registration
Request
Source Address = mobile mode’s 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
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 Node’s IP Home Address
Home Agent IP Address
Copied from a Foreign Agent Advertisement
Life Time
Fields of Registration Request as set by Mobile Node for
Foreign Agent care of Address
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Mobile IP
Registration Request
Home Link
Foreign Link
Arbitrary Topology of
Routers and Links
X
Home Agent
Registration Reply
Source Address = mobile node’s Link Layer Address
Link Layer
Header
IP
Header
Registration
Request
10/5/98
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
Source Port = anything
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 Node’s IP Home Address
Home Agent IP Address
Collocated care of address
Life Time
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Mobile IP
deregistration request
X
Arbitrary Topology of
Routers and Links
Home Link
Home Agent
deregistration reply
Link Layer
Header
Src Address = mobile node Link Layer Address
IP
Header
Src Address = Mobile Node IP Address
Dst Address = ARP (Home Agent IP Address)
Dst Address = Home Agent IP Address
Registration
Request
Mobile Node Home IP Address
Home Agent IP Address
mobile node Home Address
Life Time = 0
Fields in Deregistration Request as set by Mobile Node
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Mobile IP
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 headers
containing 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 Mobile
Node 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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Mobile IP
reg Request = Read Registration Request From Mobile Node ( )
invalid
Authentication Field
valid
Registration Reply ( )
yes
Registration Reply ( )
Lifetime > maximum
no
Sufficient Resources
to handle
Mobile Node
yes
no
Registration Reply ( )
no
Type of Tunneling
is supported
Registration Reply ( )
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
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Mobile IP
Create a Binding
for the specified
care-of Address
leaving any existing
Binding unmodified
No
registration Req = get Registration Request ( )
Invalid
Authentication
valid
No
Sufficient Resources
No
LifeTime > 0
Yes
Care of Address
= = home Address
No
No
LifeTime = = 0
No
S==1
Replace all the mobile
node existing binding
with new binding
for the specified
care of address
Registration Reply ( )
big problem
Yes
S==0
Yes
Registration Reply ( )
Yes
Delete the mobile node binding for the
specified care of address leaving the
rest untouched
Delete all the
mobile node
Binding
Yes
Successful Registration Reply ( )
Send Gratuitous ARPs
How Does a Home Agent Process A Registration Request
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Mobile IP
registration Reply = get Registration Reply ( )
Link Layer
Header
Src Addr = Data Link for Foreign Agent )
Dst Addr = stored Data Link Address for Mobile Node
IP
Header
Src Addr = IP address for Foreign Agent
Dst Addr = stored IP address for Mobile Node
Src Port # = Any
Registration
Reply
Dst Port # = stored Port #
NO
Valid Reply
YES
update Reply code with the error
Payload = get Payload (registration Reply)
transmit Reply to Mobile Node
Update list of Visiting Mobile Node
transmit Reply to Mobile Node
How Does a Foreign Agent Process a Registration Reply
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Mobile IP
How Does a Foreign Agent Process a Registration Reply
When 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 homeagent-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 recorded
during registration Request.
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Mobile IP
IPsrc = Original Sender
IPdst = Ultimate Destination
original IP packet
Header
payload
IPsrc = Tunnel Entry-Point (Home Agent)
IPdst= Tunnel Exit-Point (care of address)
Header
Outer Header
payload
Encapsulating IP Packet
Mobile
Node
Foreign Agent
Home Agent
X
X
A tunnel from a
home agent to a
foreign agent
IP Tunneling
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Mobile IP
Correspondent Node
Foreign Link
Arbitrary Topology of
Routers and Links
Home Link
X
X
Foreign Agent
Home Agent
Mobile Node
How Packets are Routed when a Mobile Node is at Home
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Mobile IP
Correspondent Node
Mobile Node
Foreign Link
Arbitrary Topology 01
Home Link
Router and Links
X
X
Home Agent
Foreign Agent
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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Mobile IP
Correspondent Node
Mobile Node
Foreign Link
Arbitrary Topology of
Routers and Links
Home Agent
X
X
Home Agent
Foreign Agent
How Packets are Routed when a Mobile Node is at Foreign Link and Mobile
Node is sending Packets to Correspondent Node
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Mobile IP
Correspondent Node
Mobile Node
Using Routing Header
Foreign Link
Arbitrary Topology of
Routers and Links
X
Home Link
X
Home Agent
Foreign Agent
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
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Mobile 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 the
Src Addr
255.225.285.255
Data
Foreign Agent is formed as follows:
network prefix.111….
Home
Agent
Home Agent
IP
Mobile
Node IP
COA
When the Foreign Agent receives this packet it will remove, decapsulate a unicase packet
whose 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.
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Mobile IP
Mobile Nodes Receiving Broadcast messages
The 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 the
decapsulation by setting the process D bit. The encapsulated packet sent by the Home
Agent is formed as follows:
Src Addr
Home Agent
IP
10/5/98
255.255.255.255.
Data
COA
IP
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Mobile IP
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:
Src Addr
Mobile Node
Home Address
255.255.255.255
Data
Home Agent
address
The resulting packet will be routed to the Home Agent.
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Mobile IP
“Normal Registration Scenario - 1 (IPv4)”
Emad
RAS
MN
Firewall
Internet
Firewall
HA
DS
Russ
GTE.com
Nortel.com
Wi
re
P
PP
s
s
le
MN
FA
1 Agent Advertisement
2 Reg Req
3 Reg Req.
4 User profile lookup
5
Reg Reply
Reg Reply
6
7
n
o
sessi
Start
8
Not explicitly specified in MIP (RFC2002)
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Mobile IP
“Registration Scenario - 2 (IPv4) MN
does not rcv advertisement
DS
HA
FA
1
MN
Adv
Agent x
ent
2 Ag ation
it
Solic
Age
nt A
dv
4 Reg R
Reg Req.
Wait for agent
Adv.
3
eq
5
6
Reg Req.
Reg Req.
7
8
9
10
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IP10
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Mobile IP
“Registration Scenario - 3 (IPv4)”
MN does not rcv advertisement
MN does not rcv response for solicitation
HA
DS
DCHP
FA
tA
Age n
5
7
Reg Req.
x
Wait for agent adv
x
3 Wait for agent adv
Wait for rtrn adv.
c
t Soli
Age n
2
x
lic
o
S
t
n
Age
1
Query DH
MN
dv
CP
4 No response from
agent
DHCP resp
onses
HCP
dr from D
Req IP ad
6
Reply from
DHCP wit
h IP(COA
)
9
eq
8 Reg R
10
Reg Req.
Reg Req.
11
12
13
14
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IP10
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Mobile IP
“Registration Scenario - 4 (IPv4)”
HOME AGENT DISCOVERY
MN does not rcv adv.
MN does not rcv response for solicitation
HA-3
HA-2
HA-1
FA
DCHP
tA
Age n
dv
MN
c
t Soli
Age n 2
x
c
t Soli
Age n
3
1
x
CP
Query DH
4
DHCP resp
onses
5
HCP
dr from D
Req IP ad
6
Reply from
DHCP wit
h IP(CO
7
Reg Req (BC
T
AST, MCAS
A)
)
Reg Req rejecting reg RCP rej
10
Reg Rep.
9
eq
8 Reg R
12
Reg Req.
13
Reg Rep.
11
14
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IP10
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Mobile IP
“Data Routing Scenarios”
CN
Internet
Internet
MN
ISP
FA
Internet
ISP
HA
ISP
ISP
Internet
HA
CN
MN
FA
HA by -passed for optimization
Internet
ISP HA
Internet
ISP
FA
CN
MN
IPv6
HA, FA are by-passed
ISPs
CN
MN
10/5/98
Normal routing with FA, HA involvement
Mohamed Khalil
IP10
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MKIPM001
Mobile IP
•
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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IP10
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Mobile IP
Ottawa
ISDN
Dialup
Calgary
Nortel.com
HA
AOL ISP
MIP
Slip
Dialup
Internet
Leo
MPN
MPN
GGSN
IWF
IP
GSN/UMTS
France
NAC
Mexico
SGSN
Wireless
PPP
Russ
10/5/98
2G
3G
Mohamed Khalil
IP10
Emad
Wireless
PPP
Page 51
MKIPM001
Mobile IP
Interface Option-1
France
SGSN
HLRIVLR GGSN
1
2 Resolve user profile
MN
3G Reg. Req.
3 Create content
4
3G Loc update
Nortel
HA/HAD
IP Network
MPN
IP
5
IP Hdr
3G Loc update
DS
Convert to MIP
6
Tunnel
7
MN 3G Reg. Resp.
Tunnel 10
Current 3G Loc
8 up Response
9
3G Loc up Resp
-
2G system is similar; however, IWF replaces SGSN & GGSN
-
Calgary’s interface is already MIP compatible.
10/5/98
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IP10
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Mobile IP
- 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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IP10
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Mobile IP
MIP Signaling Issues
IP Network
HA
In MIP Registration
procedure is repeated
during handoff to inform
HA of new location
FA
X
Dropped in the network due to 2
congestion
X
-
-
Reg
Reg R
MN
Req
1
eq
3
Dropped due to congestion
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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IP10
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Mobile IP
ICMPv6 Router Discovery
ICMPv6 Router Discovery consists of two Messages:
a. Router Advertisement Message:
Routers Transmit router Advertisement Message on a periodic basis - or in response
to a host’s Router Solicitation on message. The source address is the address of the
senders interface and the destination is the source address of an invoking Router
Solicitation, or the all-nodes multicast address.
b. Router Solicitation Message:
The Router Solicitation Message is transmitted by a host to prompt routers to generate
Routers Advertisement massage quickly. The source address defines the sending
interface address and the destination is all-routes multicast address.
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IP10
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Mobile IP
Mobile Node Home Address
Care of Address
Max sequence #
Lifetime Value
Binding Cache (maintained by each IPv6 node)
IP address for node
Lifetime
Care of Address
Binding Update List (maintained by each mobile node)
Lifetime
Home Agent IP Address
Home Agent List
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IP10
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Mobile IP
Vers = 6
prio=ls
payload length
Flow Label
next header=58
Hop limits
Source address-router or home agent’s address
IPMv6
Header
(RFC 1883)
Destination address=mobile node’s address or All-Nodes Multicast Address
Type=134
code=0
current Hop Limit
M
O
check sum
reserve
IPv6 Router
Advertisement
(Fixed Portion)
RFC 1970
Router lifetime
Reachable Time
Retransmission Times
Type=3
Length=4
Prefix Length
valid lifetime
preferred lifetime
Reserved
Prefix
information
option
RFC1970
Reserves 2
Network Prefix
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IP10
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Mobile IP
Vers = 6
prio=l5
payload length=8 (_______)
Flow Label
next header=58
Source address= the Mobile Node’s unicast address
Hop limits
IPv6 Header
(RFC 1883)
Destination address=the All-router Multicast Address
Type=133
code=0
check sum
reserved
ICMPv6 Router
solicitation (RFC
1970)
ICMPv6 Router Solicitation
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IP10
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Mobile IP
Location Detection
The mobile node examines the network prefix contained in the received advertisement
against its home address network prefix. If there is a match then the mobile node is
connected to its Home Link, otherwise it is connected to a foreign link.
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IP10
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Mobile IP
Router Advertisement=get Router Advertisement ( )
Network Prefix = get Network Prefixes (router Advertisement)
i=o
i< length
(network
Prefixes)
i = i+1
NO
NO
(connected to
foreign Link)
YES
Moved
Network Prefixes [i]= = network
Prefix [mobile Node Home
Address]
YES
Coa=get Care Of Address ( )
YES
YES
Deregister ( )
NO
Register with Home Agent ( )
Moved
NO
Location Detection Algorithm
10/5/98
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IP10
Page 60
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Mobile IP
Old Network Prefixes=get Network Prefixes (old Router Advertisement
New Router Advertisement=get Router Advertisement ( )
New Network Prefixes=get Network Prefixes (new Router Advertisement
size of (new Network Prefixes) = =
size of (old Network Prefixes)
NO
Moved
i=0
i < size of (new
Network Prefix)
YES
Not
Moved
NO
New Network Prefixes [i]= =
old Network Prefixes [i]
YES
i=i+1
NO
Moved
Motion Detection Algorithm
10/5/98
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IP10
Page 61
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Mobile IP
Movement Detection:
The mobile node checks the most recent set of network Prefixes with those set of network
prefixes 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 one
of two methods. The M=1 in the Router Advertisement message informs the Mobile Node
that it will use Stateful Address Auto configuration method otherwise it will use Stateless
Address Auto. An example for stateful address assignment is the dynamic Host
configuration Protocol (DHCP) for IPv6 which is similar to Dynamic Host Configuration
Protocol in IPv4.
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IP10
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Mobile IP
The stateless Address Auto configuration is a method to acquire care of address
automatically 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 network
interface. For example the network interface address for Ethernet is 98 bits.
2. Get the Network Prefix for the current link from the prefix Information Option
contained in the Router Advertisement.
3. Concatenate the interface token with the network prefix to form a care of address. In
order to proof the uniquenin of a generated address a Neighbor Solicitation message is
transmitted with the generated address as the target address. If another node is using
this address a Neighbor Advertisement Message will be returned. In this event, auto
configuration stops and some manual intervention is required.
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IP10
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Mobile IP
YES
NO
M=1
Coa=get COA from DHCP ( )
Interface Address=get Interface Address ( )
Network prefix=get link Network Prefix ( )
Coa=merge (interface Address, Network Prefix)
Transmit Neighbor Solicitation (COA)
Not Received
Wait for Neighbor Advertisement
Address is unique
Received
Address is not unique, Manual
Intervention is required
Done
Done
Acquiring Care of Address
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IP10
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Mobile IP
Registration
In IPv4 the mobile node informs its Home Agent about its care of address through
Registration Request and Registration Reply message. These Registration Request and
Reply 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 Destination
Options. When the Mobile node obtains its care of address it informs it Home Agent about
this care of address. The Home Agent will use this care of address as an exit point of the
tunnel to get back to the mobile agent. The mobile node also informs a set of correspondent
nodes 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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IP10
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Mobile IP
1. Binding Update - this message is sent to the Home Agent or the correspondent nodes to
inform them about its care of address. The A bit is set by the mobile node to inform the
receiver of the option should send Binding Acknowledgement. The H bit is set by the
mobile 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 its
globally routable home address but also to its link local Home Address.
2. Binding Acknowledgement - a binding acknowledgement message is sent by the Home
Agent or correspondent node to indicate that it has successfully received the Mobile
Node Binding Update.
3. Binding Request - a binding request is sent to a mobile node by a correspondent node to
request that the mobile node sent Binding Updates. This is useful when Lifetime in an
original Binding Update is near expiration and the correspondent node has reason to
believe that it will continue to send packets to the mobile node.
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IP10
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Mobile IP
Ver=6
payload length
prio
Flow label
next header=51
Hop Limit
Source Address=mobile node’s globally routable home address
Destination Address=Home Agent or correspondent node
next header=60
length=9
RESERVED
Security Parameters Index (SPI)
Authentication Data
next header
Hdr Ext len
option type=16
option length
A H L
Reserved
Lifetime
Identification
Mobile Node’s Home Address
care of Address
Mobile Node’s Link Local Home Address
(only present if L bit equal 1)
IPv6 Payload (if this Binding Update is being piggy backed)
IPv6 Header
(RFC 1883)
Authentication
Header for IVv4 and
IPv6 (RFC 1820)
Destination option
header RFC 1883
containing IPv6
Binding Update
Option
Binding Update
10/5/98
Mohamed Khalil
IP10
Page 67
MKIPM001
Mobile IP
Ver=6
payload length
prio
Flow label
next header=51
Hop Limit
Source Address=home Agent or Correspondent node
Destination Address=mobile node’s home address (or care of address)
next header=60
length=9
RESERVED
Security Parameters Index (SPI)
Authentication Data
next header
Hdr Ext len
option type=193
option length
Status
Refresh
Lifetime
Identification
Mobile Node’s Home Address
IPv6 Payload (if this Binding Acknowledgement is being piggy backed)
IVv6 Header
(RFC 1883)
Authentication Header
for IPv4 and IPv6 (RFC
1826)
Destination option header
RFC 1883 containing the
Mobile IPv6 Binding
Acknowledgement Option
Binding Acknowledgement
10/5/98
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IP10
Page 68
MKIPM001
Mobile IP
Vers=6
Prio
payload length
next header=60
Flow label
IPv6 Header
(RFC 1883)
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
Destination Option Header
(RFC 1883) containing the
Mobile IPv6 Binding
Request Option
Binding Request
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IP10
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Mobile IP
Binding Update
Mobile Node
Home Link
X
Foreign Link
Home Agent
Binding Acknowledgement
1.
A mobile node connects to the Foreign Link and informs its home agent of its new care of address
Binding Update
Binding Acknowledgement
X
Home Link
Foreign Link
2.
Home Agent
A mobile node connects to a Foreign link and informs a correspondent node of its new care of address
10/5/98
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IP10
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Mobile IP
Binding Update
X
Home Link
Home 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
Binding Request
Mobile Node
Correspondent
Node
Binding Update
Foreign Link
4.
Home Link
X
Home Agent
The correspondent node requesting an update for the Mobile Node care of address when the Lifetime is an
original Binding Update near expiration.
10/5/98
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IP10
Page 71
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Mobile IP
Mobile IP address
Care of Address
Data Link layer address
Port #
Lifetime
Visiting list kept by Foreign Agent
Mobile IP address
Care of Address
Lifetime
Binding list kept by Home Agent
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IP10
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Mobile IP
Vers=6
prui
Flow label
payload length
next header=43
Hop limit
IPv6 Header
(RFC 1883)
Source Address=correspondent Node Address
Destination Address=mobile node’s care of address
next header=6
Hdr Ext Len=2
Routing type=0
Reserved
strict/loose bit map=all 0’s
segments left=1
IPv6 Type 0
Routing Header
(RFC 1883)
Address [i] = mobile node’s home address
tcp header and user date
Source-Routed Packet from Correspondent Node to Mobile Node
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IP10
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