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Research Challenges in Mobile Networking and
Computing
Thomas F. La Porta
Professor, Department of Computer Science and Engineering
Penn State University
Outline• Overview of Mobile Networking and Computing• Mature Research
– Micro-mobility– System interworking
• Open Research Topics– Security proposal
• Summary
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Mobile Internet - Ubiquitous Communications and Computing
Wireless access to networks will soon be the most popular method
• Today: 850M phone lines, 700M wireless subscribers
• Wireless growth far exceeds wired growth
Internet is driving network growth• Internet users still doubling yearly
Ubiquitous wireless data has stalled…• low data rates
• limited terminals
• limited applications
…Mobile computing has not• lap tops are everywhere
• dial-up service is pervasive
Hindered by low performance, poor connectivity, and inconvenience
0
1
2
3
1958 1978 1998 2018
wirelesscablewireline
Global Access Lines (billion)3
2
1
0
WirelessCableWireline
1958 1978 2005
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Mobile Communications Today: Tale of 2 Networks
Cellular Telecommunications Network
• Network tailored for voice – very low bandwidth
• Devices not suitable for Internet and computing applications
Despite high penetration & coverage, Internet access has fizzled
The Internet – Wireless Enterprise Networks
• Network tailored for best-effort data traffic – high bandwidth, no controls
• Supports general computing and data networking applications
Gaining high density in hot-spots, but no ubiquitous coverage
RadioWireless
Controllers
TelephoneNetwork
Internet
WirelessGateways
RadioEdge
Router
TelephoneNetwork
InternetAccessRouter
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Evolution to Multiservice networks
Core InternetBackbone
AuthenticationAuthentication
PresencePresenceLocationLocation
AggregationRouter
AggregationRouter
AggregationRouter
AggregationRouter
AggregationRouter
AggregationRouter
AccessRouterAccessRouter
AccessRouterAccessRouter
3G CellularNetworks
RadioController
RadioController Access
RouterAccessRouter
UrbanNetworks
HomeNetworks
EnterpriseNetworks
4GRadios
Ad HocNetworks
4G AirInterface
4GRadios
• DSL/Cable• High Speed Internet Access
• Broadband Distribution Networks• High Speed Pico Cells• 802.11++
• Local Mobility• Packet Voice• High Data Rates
• Outdoor Areas• High Mobility
• Allow People to network• Self Configuring
• End-to-end Internet– common mobility management and control – common transport infrastructure– common services infrastructure
Unifies various technologies (wireless, wireline, mobility)
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Examples of Individual Multiservice Networks
Wireless Networks
• 1980’s – voice services
• 1990’s – voice services with very limited data capabilities (e.g., short messaging)
• 2000’s – 3G multimedia networks (voice, data, multimedia)
Internet
• Original use – best effort data (email, remote login, file transfers)
• 1990s – some multimedia (video and audio streaming, conferencing)
• 2000’s – merging of data, voice, and multimedia (Internet telephony in enterprises)
Next trend (already ongoing): merging individual networks
• Impacts:
– transport
– control protocols
– services infrastructure
– management
– security
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Merging of Networks
Many challenges due to diverse applications, legacy systems, and philosophies
• Voice (aka Public Switched Telephone Network) and Data (aka The Internet)
• Public and Private (corporate networks)
• Interworking is a big problem
– service definitions, protocols, profiles, …
End result: Telephone network will get dumber, the Internet will get smarter
Characteristic Classic Voice Classic Data Comments
Switching Circuit (all reserved)
Packet (queuing)
Classic, old problem
End Devices Dumb Smart Mixed with wireless
Intelligence Network-based Client/Host-based
Starting to change
Services For connections, billing
Applications Starting to change
Characteristic Public Private Comments
Management End-to-end Based on need Coordination Security Left to end
systems Used to be closed
Big problems, + wireless!
Performance Best effort Typically, good Need to share Billing None, simple Gaurantees?
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Where are we?
Seamless high-speed ubiquitous network access• new access technologies – many already exist
• mobility between networks – active research area ()
Internetworking• drive towards common control paradigm – controversial ()
• interworking between networks – islands exist ()
• performance – new demands on network controllers
Security• eCommerce, enterprise data, distributed computing – no one feels safe
• authorization and accounting – bringing order to chaos
Intelligence and Applications• distribution between network and end devices – solutions have been vertical
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Where are we?
Seamless high-speed ubiquitous network access
• new access technologies
• mobility between networks– real-time mobility – Handoffs– real-time location – Paging
Internetworking
Security
Intelligence and Applications
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Current Internet-Based Mobile Packet Networks: Mobile IP
• Handoffs always managed by Home Agent– high update overhead– slow handoffs
• 3G UMTS Network structure is similar– uses specially defined (non-Internet) protocols for mobility
IntranetMDHost
Regular routing
IP Tunneling
InternetRadioAccess
Networks
ForeignAgent
ForeignAgent
HomeAgent
Permanent IP AddressTemporary IP Address
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Real-Time Mobility: Domain-based Mobility
• Distributed control: Enhanced reliability, better scaling• Localized mobility management: Lower overhead, fast handoffs• Based on IP protocols: Independent of access network Mobility across access networks
DomainRouter
RR
R R R R
DomainRouter
RR
R R R R
Local mobility Local mobility
Internet
MD
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Real-Time Mobility: HAWAII for handoffs
• Distributed control: Enhanced reliability– recovery of lost state via Internet routing protocols
• Localized mobility management: Lower overhead, fast handoffs– updates only reach routers affected by a movement
• Minimized or Eliminated Tunneling: efficient routing, easy QoS– dynamic, public address assignment to mobile devices
Compatible with Mobile IP
DomainRouter
R R R R
DomainRouter
R R R R
Local mobility Local mobilityMobile IP
Internet
MD
RR RR
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HAWAII Overhead
Domain Router/HA
Router 1 ...
BS1 BS-20... BS1 BS20
TBLBL
M
DBDB
16
2
IP
16YTR
BDLRBL
TBLBLH
BDDB
M
DBDB
16
2
2
Hawaii
M-IP
Router 7
BD Base stations/domain router 140 RD 2nd level routers/DR 7 User density 39 Km2 v User velocity 112 Km/hr LB Base station perimeter 10.5 Km TR HAWAII refresh timer 30 s Y # of updates/message 25 TM Mobile IP lifetime 300 s % users outside home domain 0.1
Message HAWAII DR
Mobile IP HA
Msg/sec Msg/sec Hawaii Registration 127.8 0 Hawaii Updates 51.3 0 M-IP Registration 48.4 574 M-IP Updates 12.7 127.4 Total 240.2 701.4
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Real-Time Location: IP Paging
• Motivation
– dormant mode increases battery life considerably
– mobile device must be located (quickly) to deliver data
– currently each network type has unique paging protocols
• Challenges
– limit overhead (messages) while maintaining low latency
– do not impact fast-path packet forwarding
– devise scaleable solution in terms of network size and administrative domains
– support various paging algorithms
• Basic Solution
– compatible with and leveraging IP protocols
– distributed control for scale and scope
ServingRouter/Switch
HomeRouter/Switch
HostR
RR
NetworkMD
Determined by address
Determined byRegistration
Determined byPaging
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Unified Paging
Internet
Home Agent
ForeignAgent
ForeignAgent
ForeignAgent
R
R
R
DomainPagingArea
Mobile IPPaging Area
3 Options:• Home Agent Paging
– Home agent buffers packets and initiates page to all Foreign Agents– Can be controlled by corporate network– Does not scale
• Foreign Agent Paging– Last active Foreign agent buffers packets and initiate paging– Distributes load
• Domain Paging– Fully distributed, very scaleable and reliable
Uniform mobility management– wireless LANs, outdoor
Old FA initiates page
HA initiates page
Any router initiates page
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IP Paging: Domain Paging
• Basic Procedures– dormant MH does not send updates unless crossing Paging Area– packets sent to last known domain– any router in old path to Mobile Host may initiate paging
• Characteristics– more complex: changes to routers in access network– excellent scaling: load distributed among all routers– excellent scoping: only routers in a paging area need topology information– excellent reliability: failed routers are routed around (OSPF)
Internet
Any routerinitiates paging
IPPaging Area
DomainRouter
R
R
RRR
R
DomainRouter
R
R
RRR
R
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IP Paging: Latency Results
• Latency (from Stanford University Local Area traces)
– Foreign Agent and Domain Paging scale best: distributed load
– Domain paging slightly more scaleable (~10%): dynamic load balancing
• Messaging Overhead
– Domain Paging has lowest overhead: no paging related updates to Home Agent
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Where are we?
Seamless high-speed ubiquitous network access
Internetworking• drive towards common control paradigm
– Internet Control
• interworking between networks
– support for legacy systems (and stubborn operators!)
• performance
– efficiency
Security
Intelligence and Applications
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Internet Control and Interworking: Unified Mobility Manager
• Integrate 3 key functions of HLR & IP (VoIP) servers
– mobility management
– security
– profile management
• Support multiple interfaces
– Wireless: ANSI 41, GSM / UMTS MAP
– Internet: VoIP (SIP, H.323), AAA (RADIUS)
CurrentIntegrateHLR/VoIP server
functions
MAP / SS7
IntegratedUser
Profile Database
Securitymanager
Pro
toco
lG
atew
ays
User locationmanager
CellularCellular
InternetInternetVoIP / IPAAA / IP
Internet (VoIP)Internet (VoIP)VoIP server
IP security server
CellularCellular
HLR
User/mobile location managementUser/mobile location management
Security control (authentication Security control (authentication center, IP security server)center, IP security server)
Service profile DB managementService profile DB management
CellularCellular
ANSI41 / SS7
Provide Home Location Register and Internet functionality
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Unified Mobility Manager: Architecture
Core servers
- Common functions across protocols
- Interface via abstraction of basic services
- Multiple server instances on a cluster of processors for system scalability
- Interworking function between protocols: O(n) versus O(n2) complexity
Protocol gateways
- Perform protocol specific controls
- Facilitate new protocol introduction
Integrated user profile DB
- Common database for a ‘user’
CDMA 2000
VoIP Servers
GSM/UMTS
Wireless Data
Integrateduser
profile
PG
Core Operations
CoreServers
PG
PG
PG
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UMM – Location Management Performance
• 2 Basic Scenarios Considered: UMTS Network with HLR or UMM
• 2 call scenarios – goal: calls travel over IP network– call from PSTN to UMTS phone (PSTN to cellular)– call from SIP phone to UMTS phone (Internet to cellular)
UMM
Internet ServingSwitch
BSMGW
GWSwitch
PSTNServingSwitch
BS
PSTN call
SIP Call
GWSwitch
SIP
PSTNServingSwitch
BSMGW
HLR
Internet
HLR & UMM are the same
SIP-UMM• uses packet for transport• efficient
HLR/UMM
SIP-HLR• uses PSTN for transport• inefficient
UMM
Internet ServingSwitch
BSSIP-UMM (SIP e2e)• most efficient
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UMM Analytical Results
• Migration to packet– short term: performance degradation from circuit/packet translation– long term: packet end-to-end improves performance
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Research Topics: Intelligence For Network Transport
Balance between simple networks and functional networks
Ad Hoc Networks
– self-configuration
– very dynamic routing
– Challenges: security, performance, relay networks to enhance cellular telecom
Sensor Networks
– power-aware component to most functions (routing, etc.)
– nodes participate in processing information
– Challenges: placement, distribution of functions
Traditional Networks
– multiclass admission control & charging algorithms
– IP Services platforms (firewalls, web redirection, …)
– Challenges: heterogeneous networks, network architecture
Heterogeneous Networks
– real-time mobility between networks
– Challenge: vastly different network characteristics
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Research Topics: Intelligence for Services
Support for creativity, rapid deployment, and wide accessibility
Network architectures
– separation of transport and service control
– re-use across network types
– Challenges: scalability, performance, reliability
Protocols
– interworking across systems
– legacy systems
– Challenges: correct semantics, functionality mapping, software
Heterogeneous networks
– access from different networks
– access via different protocols
– Challenges: security, flexibility, performance
Transport
Services
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Research Topics: Security
Performance/Security Tradeoff
Traditional Wireless
• 3G data services require network-based enhancements
• Challenges – limiting performance impact, or improving performance
Ad hoc wireless, sensor networks
• existing solutions are not scalable
• Challenges – trade-offs of security and performance
General
• end-to-end security solutions, including network, devices, OS, …
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Performance Focused Security
Goal: Allow network-based performance enhancements in a secure environment
• Specific Problem: Data performance in wireless networks is poor
– network-based solutions have been proposed for 3G
– caching has been proposed for ad hoc and relay networks
– proposed solutions contradict security models for mobile VPNs
• Sketch of solution
– allow at least one intermediate “router”, positioned at the edge of the network, to view and process a portion of a secure packet
– trade-off level of security for performance
• Benefits
– higher performance data services
– access to network-based value added services with limited security trade-off
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Security Solution for 3G: Mobile Multi-layered IPSec
• Define multiple zones in a packet (as in ML-IPsec by Zhang and Singh)– each zone has an associated security association (keys, etc.)– each zone may be terminated in one or more places inside the network
• Research: Initialization, Mobility, Performance– distribution of keys and initialization– maintenance of security during mobility– performance impact– implementation issues
Client WirelessRouter Network Firewall HostCorporate
Network
End-to-end encryption for payload
Concatenated encryption for control information
} Example
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Ubiquitous Mobile Computing - Summary
The potential still remains…
…Hard work required -
– networking: end-to-end systems issues with access and core
– intelligence: distribution between device and network (dynamic & flexible)
– applications and support services: retain generality
– new network architectures
… with Imagination -
– new ways to use mobile capabilities
– perhaps extension of wireline network paradigms is wrong!!!