Paolo Bellavista, Antonio Corradi,

Luca Foschini

SIPSIP--Based ProactiveBased ProactiveHandoff Management forHandoff Management forSession Continuity in the Session Continuity in the

Wireless InternetWireless Internet

July 4th, SIUMI’05

DEIS, University of Bologna,V.le Risorgimento n.2, 40136 Bologna, Italy

{pbellavista, acorradi, lfoschini}@deis.unibo.it

Lisboa — 04.07.2006 2/19

AgendaAgenda

Application scenario

Handoff management infrastructures– Multimedia service delivery in Wireless Internet

– Context-aware handoff management

– Proxy-based handoff middleware

MUM active middleware– SIP framework

– MUM SIP-based architecture

– MUM package for SIP context-aware events

Experimental evaluation

Conclusions and ongoing work

Lisboa — 04.07.2006 3/19

Application scenarioApplication scenario

Subnet1

Domaina Domainb

Subnet2Subnet1

Hotspot Wi-Fi Hotspot BT Hotspot Wi-Fi Hotspot Wi-Fi

Active Proxy Components

Internet

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Active ProxyActive Proxy--based Solutionsbased Solutions

Proxy-based solutions in fixed Internet– Web caching, re-directing, …

Distributed QoS and resource management– Active service paths including client, servers, and one or

more intermediate nodes, e.g., ReSerVation Protocol (RSVP)

Suitable design alternative for wireless Internet environments– Proxies can take over mobile client responsibilities and

overcome their limitations– Facilitate interaction between mobile clients and servers

Mobility, heterogeneity, …

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Next Generation of Mobile Next Generation of Mobile Multimedia ServicesMultimedia Services

Multimedia services– Session management– QoS management data flow continuity – Application-level data flow control

Connection-less protocols, e.g., RTP/UDP

Wireless Internet (WI) design constraints– Ubiquitous and continuous access

Mobile users willing for moving in WI-enabled environments during service provisioning

– High heterogeneity Mobile devices, hardware/software distribution, …

– Service provisioning exploits various wireless access technologies

SessionContinuity

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Various access technologies– Different static and dynamic properties

Unpredictable behavior of wireless medium– Sudden changes of network conditions: delay,

bandwidth, Received Signal Strength Indicator (RSSI), …

Need for ContextNeed for Context--AwarenessAwareness

Context awareness– Enables advanced session management operations

aimed to guarantee session continuity– Requires easy access to relevant low-level and

technology-dependent information

Lisboa — 04.07.2006 7/19

Need for ContextNeed for Context--AwareAwareHandoff ManagementHandoff Management

Handoff from one Access Point (AP) to another– Horizontal: within the same infrastructure– Vertical: between different infrastructures

Problems– Unpredictable delays and intermittent discontinuities

are critical for mobile multimedia streaming applications– Dynamic monitoring of the provisioning environments

and re-negotiation of session parameters

Effective handoff management can be achieved only with a tight relationship between

context awareness and handoff execution

Lisboa — 04.07.2006 8/19

ProxyProxy--based Middleware forbased Middleware forSession ContinuitySession Continuity

Application level middleware for context-aware handoff management of service session

– Service session information: data flows characteristics, user preferences, negotiated QoS levels, …

– Context information: access networks (Bluetooth, Wi-Fi,…), client device profiles, …

Proxy-based infrastructures– Suitable solution for WI era– Middleware glue extends client/server capabilities

Buffering during handoff, content adaptation, …– Able to proactively initiate handoff management execution

Device handoff prediction

Existing frameworks for session management: Session Initiation Protocol (SIP)

– Wide acceptance, mobility support, high flexibility

Lisboa — 04.07.2006 9/19

MUM Active MiddlewareMUM Active Middleware

Mobile agent-based Ubiquitous multimedia Middleware

Service session continuity– Session continuity maintenance– Handoff management

Active service paths– Server, one or more active proxies (one for each client)

and client

MUM SIP-based architecture– Context-aware extensions to SIP

To support proactive handoff management

– Interoperability with SIP framework

Lisboa — 04.07.2006 10/19

SIP FrameworkSIP Framework

Session Initiation Protocol (SIP)– IETF RFC 3261– Application level session

signalling protocol:INVITE, OK, ACK, …

– Proxy-based architecture

Main Entities– Session signalling: User Agent

Server (UAS), User Agent Client (UAC), Proxy

– Session signalling + data flow provisioning: Back to Back User Agent (B2BUA)

– Support: Redirect

Other extensions: “Specific Event Notification” (IETF RFC 3265)

REDIRECT

Stream Server

B2BUA

PROXY

(6) OK

(7) OK

(8) OK(3) IN

VITE

(4) I

NVITE

(5) INVITE

(9) DATA FLOW

(1) INVITE

(2) FINAL RESPONSE

User Agent Client

(9) NOTIFY

(9) DATA FLOW

User Agent Server

SIP Signalling

Data Flow

Lisboa — 04.07.2006 11/19

SIP Framework:SIP Framework:Mobility SupportMobility Support

SIP Proxy

Proxy/Re-direct

Server

ClientSIP Proxy

UAS

SIP Proxy

UAC

Subnet1

BT cell Wi-Fi cell

B2BUA UACUAS

Subnet2

Wi-Fi cell

B2BUAUACUAS

UAC

Re-direct Re-direct

Mobility support– Very simple:

RE-INVITE– Various types:

Session, personal, terminal, …Micro and macro

Proxy-based architecture localreconfigurations

Non context-aware– No visibility of

executing contextcharacteristics

– No handoff predictions

UAC

RE-INVITE

Micro handoff: AP change(same subnet)

RE-INVITE

Macro handoff: AP + IP change(different subnets)

Lisboa — 04.07.2006 12/19

MUM MUM SIPSIP--basedbasedVerticalVertical Macro Macro HandoffHandoff

Subnet1BT cell Subnet2 Wi-Fi cell

Re-direct1

ProxySwitch

Data flow from server

UAC

2.

Re-direct2B2BUA Table

1. HandoffNOTIFY

5.

8.

C1

HAA2HAA1

UAC

C1

6.6’., 7.

HA1HA1B2BUAC1

Proxy BufferC1

3.

HA1HA1B2BUAC1

Proxy BufferC1

4. 9’.

SIP SignallingData flowMUM Signalling

9.HAA: Handoff Agent Activator

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MUM Package MUM Package forfor SIPSIPContextContext--awareaware EventsEvents

NOTIFY sip:lucab2bua@192.168.3.20:3111;transport=udp SIP/2.0 Call-ID: nist-sip-invite-callId 1 CSeq: 5 NOTIFY From: <sip:luca@192.168.3.1:6102>;tag=7064 To: <sip:lucab2bua@192.168.3.20:3111>;tag=3945 Via: SIP/2.0/UDP 192.168.3.1:6102;branch=z9hG4bK9ad3c15d5... Max-Forwards: 70 Content-Type: application/contextAwarenessinfo+xml Subscription-State: active Event: contextAwareness Content-Length: 473 <?xml version="1.0"?> <!DOCTYPE contextAwareinfo SYSTEM "contextAwarenessinfo.dtd"> <clientinfo xmlns="urn:params:xml:ns:contextAwarenessinfo"> <prediction aor="sip:luca@192.168.3.1"> <type>vertical</type> <handoffProbability>high</handoffProbability> <oldAP> <type>BT</type> <coverageStatus>low</coverageStatus> </oldAP> <newAP> <type>WiFi</type> <coverageStatus>high</coverageStatus> </newAP> <newAPaddress>00:0D:29:3A:5F:72</newAPaddress> </prediction> </contextAwareinfo>

SIP Event Framework for Context Awareness

– XML schemacontextAwareness

Subscribe/Notify SIP messages header

– Contact informationUAC, B2BUA

– Package type: application/contextAwareness

Handoff Notify message payload (step 1 previous slide)

– Handoff type and probability

– Old and new wireless cell technology and coverage status

– AP MACs

Lisboa — 04.07.2006 14/19

Handoff PredictionHandoff Prediction

a

ue

a

uripr ak +⎟

⎠⎞

⎜⎝⎛ −= −)1()( 1

0 10 20 30 40 50 60

time (s)

-90

-80

-70

-60

-50

-40

-30

RS

SI (

dB

)

Actual RSSI

Filtered RSSI

RSSI monitoring for all AP in visibilityGrey Model for RSSI prediction/filteringRSSI obtained on client nodePrediction algorothm execution on client node

Lisboa — 04.07.2006 15/19

TwoTwo LevelLevel ProactiveProactiveB2BUA B2BUA BufferingBuffering

Wi-Fi

ConnectionBT

Connection

Client buffer duration >= handoff duration

Supported services: VoD, Live Streaming

Normal conditions avoid server-to-client locality retransmission due to packet losses

1. Vertical Handoff Prediction

B2BUA

Nodo Proxy Nodo Client

UAS UAC

Nodo Server

2. NACK(last frame)

Lisboa — 04.07.2006 16/19

Implementation Hints and Implementation Hints and Experimental Experimental TestbedTestbed

Multimedia library: Java Media Framework– Low level API

Buffer management, easy-to-use and performant– Client e proxy– RealTime Protocol– H263 encoding

Other system libraries and tools– NIST JainSIP– JDHCP 1.0.1– iwconfig, hcitool

Experimental testbed– Client: Asus laptops connected by an IEEE 802.11b Cisco card and a

Mopogo BT doungle, class 1, version 1.1– Proxy and Server: Dell PC, 3GHz, 512MB RAM, Linux Gentoo– Wireless infrastructures

Wi-Fi: Cisco Aironet 1100 APBT: Mopogo BT doungle, class 1, version 1.1

Lisboa — 04.07.2006 17/19

Vertical Handoff Performance Vertical Handoff Performance

Without proactive discovery of target access network– Case 1: BT Wi-Fi (~1200ms), case 2: Wi-Fi BT (~7s)

With proactive discovery of the target network– Case 3: BT Wi-Fi (~500ms), case 4: Wi-Fi BT (~1,5s)

0500

10001500200025003000350040004500500055006000650070007500

1 2 3 4

Data-link connection DHCP discovery SIP signaling Data re-binding

ms

Lisboa — 04.07.2006 18/19

VerticalVertical HandoffHandoff ScalabilityScalability

0

20

40

60

80

100

120

1 2 3 4 5

60 Clients 75 Clients 90 Clients

ms

250 300 350 400 450 ms

Delay between NOTIFY (sent by UAC) and OK (sent by B2BUA) at new AP

– Request arrival-rate: Poisson distribution with inter-arrival time varying in the interval [250ms, 450ms]

RequestArrivalRate

ResponseDelay

Lisboa — 04.07.2006 19/19

Conclusions and Ongoing WorkConclusions and Ongoing Work

Conclusions– SIP-based application-layer solutions are suitable

in mobile WI scenarios– MUM handoff prediction and context-aware

notifications reduce handoff delays and guarantee session continuity

Ongoing work– Soft-handoff management techniques (BT and

Wi-Fi)– Other optimizations: DHCP-Relaying techniques

to further reduce IP address discovery time

Lisboa — 04.07.2006 20/19

Further Experimental ResultsFurther Experimental Results

443RE-INVITE

256 DHCP Relay

154INVITE / ACK (to B2BUA)

210INVITE / ACK (to Redirect)

Time (ms)SIP Messages

CPU usage overhead on client node– Passive mode (pull interactions): 5%– Active mode (push interactions): 21%

0

100

200

300

400

500

600

700

800

ms

Confronto reINVITE

Senza supporto proattivo

Con supporto Proattivo(No DHCP Relay)

Con supporto Proattivo(con DHCP Relay)

RE-INVITE Optimizations

No proactive support

Proactive support

Proactive support + DHCP Relay

SIP Signalling Details

Lisboa — 04.07.2006 21/19

RelatedRelated PublicationsPublications and and Project Home PageProject Home Page

Articles:– P.Bellavista, A.Corradi, L.Foschini, “MUM: a Middleware for the

Provisioning of Continuous Services to Mobile Users”, IEEE ISCC, 2004

– P.Bellavista, A.Corradi, L.Foschini, “MUMOC: an Active Infrastructure for Open Video Caching”, IEEE DFMA, 2005

– P.Bellavista, A.Corradi, L.Foschini, “Java-based Proactive Buffering for Multimedia Streaming Continuity in the Wireless Internet”, IEEE WoWMoM, 2005

Prototype code: http://lia.deis.unibo.it/Research/MUM

Contacts: Luca Foschini, lfoschini@deis.unibo.it