Always Best Connected

1
Always Best Connected

• Johan Kristiansson
• johank_at_sm.luth.se

2
Overview

• Introduction
• Always Best Connected
• Mobility management
• Problems Concepts
• Example 1 - Mobile IP
• Example 2 - Resilient Mobile Socket
• Handover decision algorithms
• Example applications

3
The future

• What will computers look like in say 10 years?
• Computers Portable
• Network access Wireless
• People Mobile

4
The future

• How will wireless networks look like?
• A super wireless network?
• A combination of different types
  of networks is more likely
• Wireless overlay networks
• 4G

or
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Wireless Overlay Networks
Satellite Networks
Cellular Networks
Regional-Area
WLAN/Bluetooth
Wide-Area
Local-Area/Personal-Area
Ad-hoc Networks
6
An example Coverage map

GSM/GPRS
WLAN RadioSphere
WLAN Telia Homerun
UMTS
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Heterogeneity

• Coverage
• Regional to Personal Area
• Bandwidth
• GPRS 10 kb/s
• UMTS ?????
• WLAN 54 Mb/s
• UWB 480Mb/s
• Latency
• GPRS 2 seconds
• WLAN lt1 ms!!!

8
Heterogeneity (contd)

• Connection setup time
• Instantly to minutes
• Network services
• QoS, IP multicast
• Authentication
• Pin codes, password, certificates
• Price
• Flate-rate to complex billing schemes

9
Take advantage of all networks?

Imagine sitting on a bus and restarting your PDA
half the time, just to get it work!!!

• No way, why cant it just work?

10
Always Best Connected

• Challenges

• Make a Mobile Internet easy to use
• Create competition between providers
• Let access technologies complement
• each other

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Always Best Connected

• Ideally (the dream)
• Umlimited coverage
• Zero configuration
• Unlimited bandwidth or QoS support
• Unlimited battery power
• Flate-rate or no economical cost
• Always Best Connected (the best we can do)
• Use the best connection/network available
• No/minimal user interaction
• Resource adapatation
• Consider the economical cost

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Always Best Connected

• Some important research questions
• How can users transparently switch to another
  network?
• What is the best network and how can it be
  determined?
• When should a handover to another network take
  place?
• Referred as mobility management

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• Mobility management

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Mobility management Terminology

• Mobility
• Device portability
• The communication device moves with the user
• Micro-mobility
• Macro-mobility
• User mobility
• The same service is available att different
  places
• Remote desktop, VNC etc.

15
Mobility management - Terminology

• Handover
• Switch network or base station
• Vertical handover
• Switch access technology
• Horizontal handover
• Switch operator
• Re-active handover
• Pro-active handover
• Seamless handover
• Soft handover

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The need for mobility

• What is the problem?
• Coverage
• More than one base-station is required
• Space division multiplexing
• gtMust be able to switch base-station
• Micro-mobility management
• Networks
• Sub-networks
• Ownership Autonomous systems
• Operators
• gtMust be able to switch network
• Macro-mobility management

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Micro-mobility vs Macro-mobility

Network A
Network B
Macro-mobility
Micro-mobility
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Micro-mobility vs Macro-mobility

TCP/IP protocol stack
Application layer
Application layer
RMS
Transport layer
Transport layer
Network layer
Network layer
Mobile IP
Link layer
Link layer
WLAN UMTS GSM etc
Physical layer
Physical layer
Micro-mobility
Macro-mobility
Hide mobility from higher layers
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Problems caused by macro-mobility

• Routing issues
• The IP protocol was never designed for mobility
• IP routing decisions are based upon IP addresses
• A host must be located on the network indicated
  by its IP number in order to receive packets
• This means that hosts must change IP address when
  they move around

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Problems caused by macro-mobility

• Routing issues
• TCP connections can't survive an IP address
  change
• srcAddrdestAddrsrcPortdestPort
• Protocols apps assume that these four
  quantities remain constant during a TCP sessions

21
Problems caused by macro-mobility

• Application issues
• Applications are using IPport as an identifier
  in datastructures

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Mobile IP

• What is Mobile IP?
• The current IETF standard for macro-mobility
• A routing protocol
• Allows mobile users to keep thier IP addresses
  when roaming in a wireless landscape
• Two components
• Mobile Nodes
• Agents (Home agent and Foreign agent)

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Mobile IP

• What is a Mobile IP Agent?
• A router with an interface on the mobile node's
  home link
• The mobile nodes informs its current location,
  represented by its care-of address
• Intercepts packets destined to the
  Mobile Node's home address
• Tunnels packet to the Mobile Nodes current
  location, i.e its care-of address
• Home-agent and Foreign-agent

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Mobile IP

• What is a Mobile IP Node?
• Can handover to any IP-based network while
  keeping its home address
• Performs move detection
• Care-of-addresses
• Registers to a Foreign Agent
• Or, registers directly to a Home Agent (collected
  care-of address)

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Mobile IP

Foreign Agent 130.240.96.135
DST213.114.110.19 SRC130.240.64.30
Correspondent 213.114.110.19
Home Agent 130.240.64.116
Mobile Node routing table
Route Next default
130.240.64.1
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Mobile IP

Foreign Agent 130.240.96.135
DST130.240.64.30 SRC213.114.110.19
Correspondent 213.114.110.19
Home Agent 130.240.64.116
Mobile Node routing table
Route Next default
130.240.64.1
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Mobile IP

Foreign Agent 130.240.96.135
DST130.240.64.30 SRC213.114.110.19
Correspondent 213.114.110.19
Home Agent 130.240.64.116
Mobile Node routing table
Route Next default
130.240.64.1
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Mobile IP

Foreign Agent 130.240.96.135
1. Move detection 2. Agent discovery 3. Agent
registration 4. Tunnel setup
DST130.240.64.30 SRC213.114.110.19
Correspondent 213.114.110.19
Home Agent 130.240.64.116
Mobile Node routing table
Route Next default
130.240.64.1
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Mobile IP

Foreign Agent 130.240.96.135
DST130.240.64.30 SRC213.114.110.19
Correspondent 213.114.110.19
Home Agent 130.240.64.116
HA uses Proxy ARP HA Send gratuitous ARP
Home Agent routing table
Mobile Node routing table
Route Next 130.240.64.30
TUNNEL default 130.240.64.1
Route Next default
130.240.96.135
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Mobile IP

Foreign Agent 130.240.96.135
DST213.114.110.19 SRC130.240.64.30
DST130.240.64.30 SRC213.114.110.19
Correspondent 213.114.110.19
Home Agent 130.240.64.116
Home Agent routing table
Mobile Node routing table
Route Next 130.240.64.30
TUNNEL default 130.240.64.1
Route Next default
130.240.96.135
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Mobile IP

Foreign Agent 130.240.96.135
DST130.240.64.30 SRC213.114.110.19
Correspondent 213.114.110.19
Home Agent 130.240.64.116
MN deregister from HA MN sends gratuitous ARP
Mobile Node routing table
Route Next default
130.240.96.135
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Mobile IP

• Advantages
• Transparency
• Works on any IP based transport and application
  protocol
• Applications can be kept unmodified
• No need for a dedicated naming scheme
• Why is not Mobile IP used today?
• Too few wireless devices?
• Too few wireless networks?

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Mobile IP

• Disadvantages
• Scalability
• Requires support from the infrastructure
• Business model unclear
• Operators strives for monopolies
• Breaks the Internet routing model
• Triangular routing
• Inflexible
• Can not satisify all applications at the same
  time
• Naming
• Many applications are using their own naming
  scheme
• INS, JINI, DNS, SIP

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Mobile IP

• Besides, do we really want to keep our old
  applications unmodified!?
• Portable devices have limited interaction and
  power capabilities
• Old applications cant handle disconnections
• Consequently, all applications must be modified
• Why cant we just add macro-mobility support
  directly into applications?

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Break

• Questions?

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Resilient Mobile Socket

• Motivation
• Mobile applications must be modified
• Limited GUI
• Adaptvity
• Battery life time
• Bandwidth limitation
• Financial costs
• Why not add macro-mobility support directly into
  applications?

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Resilient Mobile Socket

• But, want applications be even more complexer
  then?
• All applications must be modified?
• Solution
• Build a layer or middleware that is inserted
  between the application and the protocol stack
• For example) A new socket

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Resilient Mobile Socket

• Resilient?
• Elastic mask failures
• Can recover from failures
• Robustness
• Mobile?
• Handover support
• Switch between unicast and multicast
• Socket?
• An abstraction
• An API used by applications to access TCP/UDP/IP
  stack.
• Send/receive packets or streams

Applications
Socket
Internet
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RMS - Architecturial overview
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Socket encapsulation

• The idea
• Encapsulates other sockets into a new socket
  abstraction
• Any internal socket can fail
• Use several internal socket simultaneously, i.e
  redundancy or soft handovers
• Integrate Mobile IP Agent functionality directly
  into applications
• Application is responsible for redirecting
  packets

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Using a datagram socket
In-comming packet
Out-going packets
In-comming packet
Out-going packets

SRC Adress
SRC Adress
Data
SRC Port
Data
SRC Port
DST Port
DST Port
Data
Data
DST Adress
DST Adress
Send
Receive
Send
Receive
Internet
Socket
Socket
TCP/IP
TCP/IP
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Problems caused by mobility

• What happens when a client moves to another
  network?
• Sender
• Packets are send to the wrong location
• DSTaddress DSTport are incorrect
• Receiver
• Packets are received from a new host
• SRCaddress SRCport are incorrect
• Remember IP addresses and ports are used as
  identifiers in higher layers
• Application is not aware that a host changed
  location

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RMS - The solution

• Packet translation
• Let each host maintain a translation table over
  all connected clients (end-points)
• Re-stamp out-going packets
• Will reach mobile host visting foreign networks
• Re-stamp in-comming packets
• Higher application will not notice that hosts
  have changed topological location
• Mobility is hided from applications

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Example

Two hosts has moved
1
2
Addr 2 -gt Addr 4
Addr 3 -gt Addr 1
1
2
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RMS - Packet translation

But how is the translation table maintained?
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RMS - In-band signaling

• Each RMS will send a special packet (RMSCP) in
  the same stream as user data packets
• The RMSCP contains the RMS identifier and the new
  topological location

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RMS - API
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RMS - API

• Hard handover (HHO)
• Reactively called when connecitivity is lost
• Soft handover (SHO)
• Proactively called when the user wants change
  network
• Redundancy
• Compare two connections
• Protection from temporaly failures
• Suspend
• Called when a RMS becomes disconnected

49
The testbed

• Java based prototype
• Integrated with Marratech Pro
• Study GSM audio

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RMS - Soft handovers
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RMS - Performance

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RMS - Performance

• Observations
• WLAN is not designed for out-door usage
• Soft handovers are good, but must be initated a
  given time before a connection is lost
• Must be able to detect disconnections in advanced

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• Handover decision algorithms

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Handover decisions

• What is the best network?
• Interactive real-time media
• Low-latency
• Packet losses
• Financial cost
• None-real time media
• High bandwidth
• Financial cost

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Handover decisions

• When should a handover take place?
• Minimizing financial cost
• Use WLAN when possible then UMTS
• Maximize performance or quality
• Switch to the network with less RTT
• Different media have different requirements
• File-transfer, use a WLAN networks as long as
  possible
• Real-time media, switch when latency becomes to
  high

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The traditional way

• Compare signal strengths
• Thresholds

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The traditional way

• Can the same technique be used for
  macro-mobility?
• Signal strength or SNR
• Only reflects the quality of the air interface
  and not the network
• Congestion?
• Routing problems?
• SNR is incommerciable in multiacces networks
• Jitter or delays are better choices
• However, we cant really compare two connections
  without injecting packets to the network

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An alternative - Pattern recognition

• Build an expert system
• Artificial intelligence
• Neural network
• Try to predict disconnections instead

Neural network
60 probability that connection is lost
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• Some example applications

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Example app Wireless VoIP

• A WLAN Mobile Phone
• A cheaper alternative than traditional cellular
  phones
• SIP interoperability with PSTN
• RMS to preserve communication

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Example app - Mobile E-meetings
Tomorrows communication tool!?
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Summary

• Always Best Connected
• Adaptive self-configurating applications
• Better operating system support
• Middlewares new APIs

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The end

• Questions?