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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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HAWAII Handoff Delay: Packet Loss

Audio (160B/20msec)

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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!!!