Chapter: 07-Mobile Computing
4 G& Mobile IP
By: Mr. Abdul Haseeb Khan
Outline
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Description of wireless networks
Wireless network evolution
Wireless key technologies
Current researches
Goals Of Network Layer
Terminologies
M-IP Protocol (Discovery, Registration, Tunneling)
Routing
Inefficiencies
MIPv6
Wireless Networks
 Motivated by people-on-the-go
 PCs availability, Internet usage, Mobile life
 Aimed is to establish wide-area voice data communications
 Includes mobile systems (cellular telecommunication systems)
Forth Generation Wireless Networks
 Otherwise known as NextG, Beyond 3G, 4G, and more!
 Motivation
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Providing all available services to highly mobile people (anytime anywhere)
Use your wireless device anywhere for listening to music, shopping (m-commerce) , downloading (file
transfer), watching video (live streaming)
Multiple applications (talk and use Internet services at the same time)
 Objectives
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Total convergence of the wireless mobile and wireless access communications (developing a
broadband wireless network)
Ubiquitous wireless communications and services
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All-IP based wireless networks
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 Integration of multi-networks using IP technology
 Similar technology to the wired Internet where users are freed from their local networks
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Not just IP end-to-end but over-the-air packet switching
Supporting native wireless IP mode
Highly integrated
High bandwidth / high-speed wireless
Highly compatible with wired network infrastructures
 ATM, IP, ATM
4G Technology Challenges
 Supporting heterogeneous multitude of systems
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Includes multiple networks:
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Cellular telecommunication systems
Digital video broadband
Digital audio broadband
Wireless LAB, Bluetooth-based networks
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Open communication network: infrastructure independent which can access to any services and
applications (now and in the future!)
Complete compatibility between wireless and wired networks through gateways
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Latency, noisy environment, unpredictable discontinuities and loss, etc.
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High performance physical layer
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Scarce bandwidth availability
 Supporting statistical multiplexing of heterogeneous data over-the-air
 High-speed wireless transmission over the air
 20Mbps (2G: 28Kbps, 3G: 2Mbps)
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Efficient frequency spectrum utilization
Efficient hand off
Dynamic bandwidth allocation
Advanced digital transmission technology (modulation, low power devices, etc.)
4G Key Issues - Research Areas
 IP Addressing
 Mobile IPv6 protocol provides unbroken connectivity between mobile nodes
 Architecture
 Horizontal communications between different access technologies using
gateways
 Including local-area access technology (3G only covers wide-area packet switched
cellular technology)
 Hand off
 Fast hand off due to high-speed transmission
 High reliability
 QoS framework
 Interoperability between wireless and wired networks
 QoS classes: Conversational (most delay sensitive), streaming, interactive,
background (least delay sensitive)
 Fair bandwidth allocation
 Class-based QoS over the air
4G Key Issues - Research Areas
 Security and billing
 Essential in e-commerce
 More than just authentication and encryption (as in 3G)
 End-to-end security mechanisms between the Internet server (wired) and the mobile terminal
 No translation and decomposition of the data at the gateways
 Usage fee
 Volume based or time-based?
 TCP performance in wireless / mobile communications
 Research shows unmodified standard TCP is not well aligned with cellular boundaries
 New protocols have been developed: Snoop, Split connections, other end-to-end protocol
families
 Using Snoop agent the exchange of TCP packets and ACKs are monitored and performs local
retransmissions as needed (OBS-like!)
 Split-connections deals with wireless and wired network inconsistencies (gateways, translations,
etc.)
 Two separate connections between fixed and mobile hosts
 End-to-end protocols deal with retransmission timeout causing the TCP window to shrink too
often
Goal of Network Layer
 Goal of Routing Protocols
 decrease routing-related overhead
 find short routes
 find “stable” routes (despite mobility)
 Goal of Mobile IP
 Supporting end-system mobility while
scalability, efficiency and compatibility in all
with existing systems.
maintaining
respects
Mobile IP: Basics
 Proposed by IETF (Internet Engineering Task Force)
 Standards development body for the Internet
 Mobile IP allows a mobile host to move about without
changing its permanent IP address
 Each mobile host has a home agent on its home
network
 Mobile host establishes a care-of address when it's away
from home
Mobile IP: Basics-Terminology
 Mobile Node (MN) - is an end-system that can change the point of connection to
the network without changing its IP address.
 Home Network (HN) – is the subnet the MN belongs to with respect to its IP
address.
 Foreign Network (FA) – is the current subnet the MN visits.
 Home Agent (HA)
 Is a system (or router) located in the home network of the MN,
 registers the location of the MN, then tunnels IP datagrams to the COA
 Foreign Agent (FA)
 system in the current foreign network of the MN, typically a router
 typically the default router for the MN
Mobile IP -Mobility: Vocabulary
home network:
permanent
visited network:
“home” of mobile home agent: entity that
network in which mobile
(e.g., 128.119.40/24) will perform mobility
currently resides (e.g.,
functions on behalf of
79.129.13/24)
mobile, when mobile is
Permanent address:
remote
remains constant
(e.g., 128.119.40.186)
Permanent address:
address in home
network, can always be
used to reach mobile
e.g., 128.119.40.186
correspondent:
wants to
communicate with
mobile
wide area
network
Care-of-address:
address in visited
network.
(e.g., 79,129.13.2)
Foreign agent: entity in visited
network that performs
mobility functions on behalf of
mobile.
Mobile IP: Basics-Example:2
Network B
Foreign Agent
Home
network A
Internet
Home Agent
Network C
Mobile Node
slide by Konidala M. Divyan [3]
Corresp.
Node C
Mobile IP: Basics, Cont.….
 Correspondent Node (CN) – is a fixed or Mobile Node act as
partner for communication with MN.
 Correspondent host is a host that wants to send packets to the
mobile host
 Correspondent host sends packets to the mobile host’s IP
permanent address
 These packets are routed to the mobile host’s home network
 Home agent forwards IP packets for mobile host to current care-of
address
 Mobile host sends packets directly to correspondent, using
permanent home IP as source IP
Mobile IP: Care-of Addresses
 The Home agent uses a registry table to find the care-of address of
the mobile host.
 address of the current tunnel end-point for the MN (at FA )
 actual location of the MN from an IP point of view
 can be chosen, e.g., via DHCP
 Whenever a mobile host connects to a remote network, two choices:
 care-of can be the address of a foreign agent on the remote network
 foreign agent delivers packets forwarded from home agent to
mobile host
 care-of can be a temporary, foreign IP address obtained through, e.g.,
DHCP
 home agent tunnels packets directly to the temporary IP address
 Regardless, care-of address must be registered with home agent
Mobile Node registers at its Home Agent
Network B
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Network A
Foreign Agent

Internet
Home Agent
 Mobile Node sends Binding Update
 Home Agent replies with Binding Acknowledgement
slide by Konidala M. Divyan [3]
Mobile Node
Network C
Corresp.
Node C
Protocol
 In order to support mobility, Mobile IP includes three
capabilities:
1. Discovery
2. Registration
3. Tunneling
Discovery
 Mobile Agents send ICMP router advertisements with
mobility agent advertisement extension periodically
informing mobile nodes of its presence.
 Mobile node is responsible for the discovery process.
 In order to receive an advertisement, the mobile node may
optionally request one from an agent or simply wait for the
next advertisement.
Registration
 Mobile node recognizes that it is on a foreign network, acquires a Care-ofAddress and requests its home agent to forward its data packets to the
foreign agent.
 The process of registration requires 4 steps:
1.
2.
3.
4.
Mobile node request forwarding service by
sending registration request to the foreign
agent.
Foreign agent relays this request to the
home agent.
Home agent accepts or denies the request and sends registration
reply
to
the
foreign agent.
Foreign agent relays this reply to Mobile node.
Tunneling
 After registration, an IP tunnel is set up between the home
agent and care-of-address of the mobile node.
 Home agent broadcasts gratuitous ARP request which
causes all nodes in the subnet to update their ARP caches to
map the mobile nodes IP address to the home agents link
level address.
 Thus home agent receives packets destined to the mobile
node, and forwards the packets to the foreign agent
through the IP tunnel.
Tunneling
 In the foreign network, decapsulation is done by the
foreign agent or by the mobile node itself.
 A correspondent node assumes that the reply from
the mobile node is coming from its home network
and continues to send the packet to the home agent.
Issues in Mobile IP
1. Handoff:
 When mobile node changes its point of attachment, a
handoff sequence is initiated.
 During or immediately after the handoff , packet losses may
occur due to delayed propagation of new location
information which degrades the quality of service.
 Solved by introducing access point probing functionality in
the mobile node to identify the current access point it is
attached with.
Issues in Mobile IP
2. Replay attacks:
 A Bad Guy could obtain a copy of a valid Registration
Request, store it, and then “replay” it at a later time, thereby
registering a bogus care-of address for the mobile node
 To prevent that the Identification field is generated is a such
a way as to allow the home agent to determine what the
next value should be
 In this way, the Bad Guy is thwarted because the
Identification field in his stored Registration Request will be
recognized as being out of date by the home agent
(timestamps or nonce are used for Identification field)
Mobile IP: Security Issues [4]
Issues in Mobile IP
3. Redundancy:
What if the home agent doesn't answer a registration request?
 Registration request to broadcast address
 Rejection carries new home agent ID
4. "Ingress" filtering
 Routers which see packets coming from a direction from
which they would not have routed the source address
are dropped
Mobile IPv6 Roaming
Network B
Network D
Network A
Internet

Home Agent
 Mobile Node sends Binding Updates to Home Agent and
all Corresp. Nodes, which already received a previous
Binding Update from this Mobile Node
slide by Konidala M. Divyan [3]
Network C
Corresp.
Node C