SIP-Based Proactive Handoff Management for Session Continuity in the Wireless Internet Paolo Bellavista, Antonio Corradi, Luca Foschini
July 4th, SIUMI’05
DEIS, University of Bologna, V.le Risorgimento n.2, 40136 Bologna, Italy {pbellavista, acorradi, lfoschini}@deis.unibo.it
Agenda
Application scenario Handoff management infrastructures – – –
MUM active middleware – – –
Multimedia service delivery in Wireless Internet Context-aware handoff management Proxy-based handoff middleware SIP framework MUM SIP-based architecture MUM package for SIP context-aware events
Experimental evaluation Conclusions and ongoing work
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Application scenario Active Proxy Components
Internet
Subnet1
Hotspot Wi-Fi
Subnet2
Hotspot BT
Hotspot Wi-Fi
Domaina
Subnet1
Hotspot Wi-Fi Domainb
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Active Proxy-based Solutions
Proxy-based solutions in fixed Internet –
Distributed QoS and resource management –
Web caching, re-directing, …
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 Multimedia Services
Multimedia services – – –
Session management QoS management Æ data flow continuity Application-level data flow control
Session Continuity
Connection-less protocols, e.g., RTP/UDP
Wireless Internet (WI) design constraints –
Ubiquitous and continuous access
–
High heterogeneity
–
Mobile users willing for moving in WI-enabled environments during service provisioning Mobile devices, hardware/software distribution, …
Service provisioning exploits various wireless access technologies
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Need for Context-Awareness
Various access technologies –
Unpredictable behavior of wireless medium –
Different static and dynamic properties Sudden changes of network conditions: delay, bandwidth, Received Signal Strength Indicator (RSSI), …
Context awareness – –
Enables advanced session management operations aimed to guarantee session continuity Requires easy access to relevant low-level and technology-dependent information
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Need for Context-Aware Handoff 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
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Proxy-based Middleware for Session 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 Æ extends client/server capabilities
–
Able to proactively initiate handoff management execution
Buffering during handoff, content adaptation, … Device handoff prediction
Existing frameworks for session management: Session Initiation Protocol (SIP) –
Wide acceptance, mobility support, high flexibility
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MUM Active Middleware
Mobile agent-based Ubiquitous multimedia Middleware
Service session continuity – –
Active service paths –
Session continuity maintenance Handoff management 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
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SIP Framework User Agent Server
SIP Signalling
Session Initiation Protocol (SIP) –
Data Flow (5
E VIT ) IN
– Stream Server
OK (6)
– DATA FLOW (9)(9) DATA FLOW
) (7
O
K
REDIRECT FI NA L
(1 )
RE IN SP VI O TE NS E
– B2BUA ITE NV I K ) O (3 Y (8) TIF NO ) 9 (
– User Agent Client
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INVITE, OK, ACK, …
Proxy-based architecture
Main Entities –
T VI N )I 4 (
E
PROXY
(2 )
IETF RFC 3261 Application level session signalling protocol:
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) 10/19
SIP Framework: Mobility Support UAS
Server
Mobility support –
SIP Proxy
SIP Proxy
Client
–
Very simple: RE-INVITE Various types: Session, personal, terminal, … Micro and macro
SIP Proxy
Proxy/ Re-direct
B2BUA
B2BUA UAC Re-direct UAS
Re-direct
UAC UAS
Proxy-based architecture Æ local reconfigurations
Non context-aware
RE-INVITE RE-INVITE
UAC
UAC
UAC
No visibility of executing context Wi-Fi cell BT cell Wi-Fi cell characteristics Subnet1 Subnet2 – No handoff Micro handoff: AP change Macro handoff: AP + IP change predictions –
(same subnet)
(different subnets)
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MUM SIP-based Vertical Macro Handoff Data flow from server HAA: Handoff Agent Activator 1. Handoff NOTIFY
Proxy Switch HA11 HA B2BUA C1
9.
4.
9’.
HA11 HA B2BUA C1
Re-direct2
Proxy BufferC1
Proxy BufferC1
Re-direct1
SIP Signalling Data flow MUM Signalling
3.
2.
HAA1
HAA2 6’., 7.
6.
8.
UAC C1 BT cell
Subnet1
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B2BUA Table
UAC C1 Subnet2
Wi-Fi cell 12/19
MUM Package for SIP Context-aware Events NOTIFY sip:
[email protected]:3111;transport=udp SIP/2.0 Call-ID: nist-sip-invite-callId 1 CSeq: 5 NOTIFY From: ;tag=7064 To: ;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
SIP Event Framework for Context Awareness XML schema Æ contextAwareness –
Subscribe/Notify SIP messages header –
Contact information
–
Package type: application/ contextAwareness
vertical high BT low WiFi high 00:0D:29:3A:5F:72
UAC, B2BUA
Handoff Notify message payload (step 1 previous slide) – –
–
Handoff type and probability Old and new wireless cell technology and coverage status AP MACs
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Handoff Prediction -30
Actual RSSI Filtered RSSI
-50 -60 -70 -80
RSSI (dB)
-40
u⎞ u ⎛ pr (i) = ⎜ r 1(1) − ⎟e −ak + a⎠ a ⎝
-90 0
10
20
30
40
50
60
time (s)
RSSI monitoring for all AP in visibility Grey Model for RSSI prediction/filtering RSSI obtained on client node Prediction algorothm execution on client node
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Two Level Proactive B2BUA Buffering 2. NACK(last frame) 1. Vertical Handoff Prediction
B2BUA
UAS
Nodo Server
W BTi-Fi ccttiioonn C Coonnnnee
Nodo Proxy
UAC
Nodo Client
Client buffer duration >= handoff duration Supported services: VoD, Live Streaming Normal conditions Æ avoid server-to-client locality retransmission due to packet losses
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Implementation Hints and Experimental Testbed
Multimedia library: Java Media Framework –
Low level API
– – –
Client e proxy RealTime Protocol H263 encoding
Other system libraries and tools – – –
Buffer management, easy-to-use and performant
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 AP BT: Mopogo BT doungle, class 1, version 1.1
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Vertical Handoff Performance ms 7500 7000 6500 6000 5500 5000 4500 4000 3500 3000 2500 2000 1500 1000 500 0 1
2
Data-link connection
DHCP discovery
4
SIP signaling
Data re-binding
Without proactive discovery of target access network –
3
Case 1: BT Æ Wi-Fi (~1200ms), case 2: Wi-Fi Æ BT (~7s)
With proactive discovery of the target network –
Case 3: BT Æ Wi-Fi (~500ms), case 4: Wi-Fi Æ BT (~1,5s)
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Vertical Handoff Scalability Response ms Delay 120 100 80 60 40 20 0
250 1
300 2 60 Clients
350 3 75 Clients
400 4
450 5
ms
Request Arrival Rate
90 Clients
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]
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Conclusions 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
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Further Experimental Results RE-INVITE Confronto reINVITE Optimizations
SIP Signalling Details
SIP Messages
Time (ms)
INVITE / ACK (to Redirect)
210
800 700 600 500
INVITE / ACK (to B2BUA)
154
DHCP Relay
256
200 100
RE-INVITE
443
0
ms 400 300
No proactive support Senza supporto proattivo support ConProactive supporto Proattivo (No DHCP Relay) support ConProactive supporto Proattivo DHCP Relay (con+DHCP Relay)
CPU usage overhead on client node – –
Passive mode (pull interactions): 5% Active mode (push interactions): 21%
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Related Publications and Project 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,
[email protected]
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