Mobile IP, or TCP/IP on tour
Distribuerade
system, VT2000
Jerry.Eriksson@cs.umu.se
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Outline
Why Mobility?
IP routing, very short
The need for Mobile
IP.
Mobile IP - Overview
The Gory Details
Tunneling
Future: Mobility for
IPV6
Open Issues
TCP performance
(RSVP and Real-Time
Traffic)
Service Location
Summary and future
for Mobile IP
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Mobile IP: A standard for mobile
computing and networking
Computers doesn’t
stay put.
Change location
without restart its
application or
terminating any
ongoing
communication
Example 1: Un-plug
at campus, and plug
it back at home
Example 2: Un-plug
from office, let the
wireless network take
over
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IP Networking
Protocol layer
Network Layer
Transport Layer
What does IP do
moving packets from
source to destination
No ’end-to-end’
guarantees
IP addresses
Network-prefix
Host portion
IP Routing
Packet Header
Network-prefix
Every node on the
same link has the
same network-prefix
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The Need for Mobile IP
Fig 3.1
host Specific Routes (too costly)
Node’s IP address (TCP fails)
Link layer (Too many standards)
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Mobile IP Solves the following
problems
If a node moves from
one link to another
without chnging its IP
address, it will be
unable to receive
packets at the new
link; and
If a node changes its
IP address when it
moves, it will have to
terminate and restart
any on-going
communications each
time it moves
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Mobile IP Overview
Proposed as a
Standard in
November 1996
Solution for Internet
Scalable, robust,
secure, maintain
communication
Use their permanent
IP address
Routing protocol
Route packets to
nodes that could
potentially change
location very rapidly
Layer 4-7, outside
Mobile IP, but will be
of major interest
(TCP, for example)
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Reqiurements for Mobile IP; A
node must be able to
Communicate wtih
other nodes after
changing its linkLayer attachment to
the internet.
Communicate using
only its home IP
address.
Communicate with
other computers not
using Mobile IP.
Handle security
threats efficiently
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Design goals
Size and and the frequency as small as possible
Simple to implement.
Aviod solutions that uses multilpe IP adresses
(Running out of IPv4 adresses
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4.7: Mobile IP Entities and
Relationships (Fig. 4-1)
Mobile Node (mobilen)
Home Agent (Hemagent)
Foreign agent (fjärragent)
Home link (hemmalänk)
Foreign Link (fjärrlänk)
care-of-addresses (c/o, besöksadress)
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Home agent
A router with an interface on the mobile node’
home link
Node keep the Home agent informed of its current
location (care-of-addresses)
Advertises reachability to the network-prefix of the
mobile node’s home adress (Attracting IP adresses)
intercepts packets destined to the mobile node’s home
adress and tunnels them to (c/o)
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Foreign Agent
A router on a mobile node’s foreign link
which
assists the mobile node in informaing its
home agent of its current (c/o)
provides (c/o) adress and de-tunnels packets
(sent from the home agent)
default router generated by the mobile node.
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Tunneling
An encapsulating IP packet including a path
and an original IP packet
Figure 4-2
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Definitions on ’Home’
Home Adress - IP adress permanently assigned
to a mobile node (Does not change)
Home Link - network-prefix of the mobile node’s
home address define its home link
Home agent - A router that has at least one
interface on the mbile node’s home link
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Definitions on c/o
A c/o is specific to the foreign link currently being
visited by a mobile node.
A node’s c/o changes every time the mobile node
moves from one foreign link to another
Packets desitnated to a c/o can be delivered using
existing Internet routing mechanisms
A c/o is used as an exit pont of a tunnel from the
home agent toward the mobile node
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4.8: A high Level desription
(Fig. 4-3)
Home agents and foreign agents advertise their
presence by periodically multicasting (broadcasting)
Agent advertisements
Mobile node’s listens to Agent advertisements (I am
a home or away)
A mobile node connected to a foreign link acquires
a c/o adress
Mobile node registers its c/o address with its home
agent
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4.8: A high Level desription
(Fig. 4-3) Cont:
Home agent adverties reachibility to the netwrokprefix of the mobile node’s home link (Attracting
packets sent to the mobiles home adress.
Intercept these messages and tunnels them to the C/O
At C/O, the original packet is extracted from the
tunnel and then delivered to the mobile node
In reverse odirection, packets sent from the mobile
node are routed directly to thier destination,
without need for tunneling (FA only router)
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5: The gory details
Agent Discovery
Determines whether it is currently connected to its
home link or a foreign link.
Detects whether it has moved from one link to
another
obtains a care-of adress when connected to a foreign
link
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5.2.1: Messages
Agent advertisements; Used by agents to
announce their capabilities to mobile nodes
Agent advertisements are continuously transmitted
(multicast/broadcoast) on a specific link
Allow the mobiles to determine whether any agent is
present (gets identities)
Agent solicitations; are sent by mobile that do
not have the patience to wait for an Agent
advertisment
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5.2.2 How does a mobile node
detrmine that is has moved?
Using Lifetime: Tells the mobile how soon it
should expect to hear another Agent
Advertisment.
AA three times faster than Lifetime
Multiple foreign agents
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5.3 What is registration
 A mobile node
register whenever it detects that it has chnged link from
one network to another.
Reregisters when it has not moved, but when it existing
registration due to expire.
 Mobile IP registration is the process by which a mobile node:
requests routing services from a foreign agent or foreign
link
informs its home agent of its current care-of-address.
Renews a registration due to expire
deregisters when it returns to its home link
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5.3.1 Registration scenarios
A registration consists of an exchange of a
Registration request and a Registration Reply
between a mobile node and its home agent.
Three common scenarios:
Using foreign agent c/o
Using collocated c/o
deregisters upon returning home
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5.3.2 How do nodes Process
registrations
Se summary
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5.3.3 How can a Mobile learn
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5.3.4. How Does
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5.4: How are the Packets
routed
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5.4.6 Why the triangle routing
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5.5 Summary
Agent Discovery
Registration
Routing
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Tunneling: 6.1 IP
Encapsulation
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Future Topics;
12: IPv6 vs IPv4
Work in progress
Size adresses: 128 bits vs 32 bits
No real chance of running out of adresses
A single newtowrk-prefix route
Autoconfigure using very simple mechanisms
Less frequently used fields in IPv4 moved
into optional
IPv6 more rigorously defined (more useful)
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12.2 Relevant to Mobile IP V6
Larger adresses - No need for Foreign agents
Collocated C/O is the only one needed, snice there are
sufficient IP adresses
New routing Header help
Security attack (less options)
Very fast forward desicion- not all routers need to read
by every router, Router Discovery
Static Address Autoconfiguration -
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12.1.1 Headers
Base: Priority fields, Flow label (Real-time traffic)
Extension headers: Form a chain of headers
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12.4 How Does it work
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12.5 How does a Mobile ...
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12.6 How Does
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12.8: IP V6 summary
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13: Open Issues. 13.1: TCP
Performance and Mobility
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13.1.1: What is TCP
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13.1.2: How does TCP works
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13.1.3: Are TCP’s ..
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13.1.4: How can TCP
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13.2 RSVP and Real-Time
Traffic
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13.3 Service Location
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14: Summary
Background
Terminology
Applying Mobile IP
Open Issues
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14: The future of Mobile IP
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