Multimedia SIP Sessions in a Mobile Heterogeneous Access Environment
Ashutosh Dutta, Yibei Ling, Wai Chen, Jasmine ChennikaraTelcordia Technologies
Onur Altıntaş Toyota InfoTechnology Center, USA
Henning Schulzrinne Columbia University
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Outline
SIP based mobility Heterogeneous Access Architecture Issues related to SIP-based sessions SIP sessions for Heterogeneous Networks Experimental Setup and Results Conclusions
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Motivation (1)
Objective:
Analyze and experiment with a carrier-independent end-to-end Mobility Solution for scalable wireless Internet Roaming involving PAN, LAN and WAN
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Motivation (2)
Wireless Internet Roaming is becoming a norm rather than an exception
SIP is gaining momentum as a signaling mechanism for multimedia sessions
SIP provides an application layer multi-facet mobility solution Many drawbacks associated with Mobile IP are taken care of
– No dependence on HA based solution Multiple Access Technologies (Bluetooth, 802.11x, CDMA,
GPRS)– Provide an integration between PAN, LAN and WAN– Flexibility of selecting a particular interface based on type of
application Smooth transition between heterogeneous access networks by
providing a virtual soft-handover
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WLAN Network
AccessNetwork 2
AccessNetwork 3
CellularNetwork
S1
S2
S3
S4
AccessNetwork
AccessNetwork
AccessNetwork
CellularNetwork
InternetDomain1
Domain2
PDA
Webphone
Multi-mediaTerminal
AN
AccessNetwork 1
Wireless Internet Roaming in Heterogeneous Environment
SIP UA
SIP UA
SIP UA
PAN
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Media Transport
App
lica
tion
Dae
mon
Ker
nel
Phy
sica
lN
etw
ork
H.323 SIP RTSP RSVP RTCPRTP
TCP UDP
IPv4, IPv6, IP Multicast
PPP AAL3/4 AAL5 PPP
SONET ATM Ethernet CDMA 1XRTT/GPRS
Signaling media encap(H.261. MPEG)
ICMP IGMP
SAP
802.11b
DNSLDAP
MIP MIP-LR
CIP
SDP
MIPv6
MGCP
IDMP
IETF Multimedia Protocol Stack
DHCPP
Heterogeneous Access
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SIP Background
SIP allows two or more participants to establish a session including multiple media streams– audio, video, distributed games, shared applications, white boards,
or any other Internet-based communication mechanism Standardized by the IETF RFC 2543 Is being implemented by several vendors, primarily for Internet
telephony– e.g. Microsoft XP operating system includes SIP as part of its built-in
protocol stack Recently being extended to provide presence, instant
messaging and event notification Endpoints addressed by SIP URLs
– sip:[email protected]
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SIP Background: Components
SIP server Registrar
Proxy
LocationDatabase
Redirect
Proxy
SIP User Agent Client Host
SIP User Agent Client
SIP User Agent ServerHost
SIP User Agent Server
UDP/5060 (Signaling)
UDP/5060 (Signaling)
RAT
WB
VIC
CHAT
VNC
RAT
WB
VIC
CHAT
VNC
audio
video
white board
text
desktop sharing
RTP/UDP
RTCP
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Why SIP Mobility ?
SIP is an application layer signaling protocol:– it can keep mobility support independent of the underlying wireless
technology and network layer elements;
3GPP, 3GPP2, and MWIF have agreed upon SIP as the basis of the session management of the mobile Internet
SIP will eventually be part of the mobile Internet so why not use its inherently present mobility support functions
SIP can provide personal mobility, terminal mobility, session mobility and service mobility
No requirement to modify (or add) capabilities to existing terminal’s operating system
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SIP provides variety of mobility techniques
– Personal Mobility Allows users to be reachable in multiple locations using a unique URI
– Service Mobility Allows users to maintain access to their services while moving between
service providers– Session Mobility
Allows a user to maintain a media session while changing between terminals
– Mid-session (terminal) mobility Allows a user to maintain a session while moving (support for real-time
streaming applications for mobiles)
Types of SIP mobility
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SIP Mobility Basic Flows
CH MH MH (new location)
SIP Signaling
RTP Media stream
MH moves during session
Re-register
Re-INVITE with new Contact address
SIP signaling and RTP/UDP session remains intact
SIP server
Register
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Handoff Delay Analysis (SIP-Mobility)
CH MH (IP0)SIP Signaling
RTP Session
Base StationMH (IP1)
MH movesBeacon
DHCP/PPP Server
Discover/Request
Offer/IP address
Binds L2
L3
Configuration Time
Re-Invite
RTP SessionMedia
Redirection
Beacon Interval
Beacon
L2 = Layer 2
L3 = Layer 3
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Heterogeneous Access for Services in a LAN (SIP and Mobile IP approach)
CDMA 802.11x WaveLan
DHCPDHCP
Internet
Subnet S0 Subnet S1
IPS01 IPS02 IPS11 IPS12
CH/Media Server
SIPServer
SIPServer
SIPUA
SIPUA
PPPServer
PPPServer
Bluetooth CDMABluetooth
Visited Network A Visited Network B
Home Network
Intra-Net
HomeAgent
Router/Foreign agent
Router/Foreign Agent
SIPUA
Intra-Subnet MobilityIntra-Subnet Mobility
Inter -Subnet MobilityInter -Subnet Mobility
IPS03IPS13
802.11x
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Heterogeneous Access for SIP Sessions
CDMA/GPRS
CDMA/GPRS
MHCellularAccess
Network
WLANAccess
Network
CH
LocalSIPServer
DHCP/PPP
DHCP/PPP
DHCP
DHCP
IPA1
IPA2
IPB1
IPB2 LocalSIPServer
IPch
CoreNetwork
CoreNetwork
HomeSIPServer
CoreNetwork
802.11x
802.11x
Public Internet
Public SIPServer
RouterRouter
AAA
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Technical Issues (1)
Movement during session setup – With direct signaling
Retransmissions after timeout
– With proxy server Redirects to the right IP address
SIP sessions with NAT: IP address MH uses to invite CH will not reach MH (e.g. 3G network may be an Intranet)– Use of Application Layer Gateway
– STUN (Simple Traversal of UDP through NAT)
User Agent with Multiple IP addresses detection– SNR based
– Policy based
– can be application specific (e.g. audio use CDMA, video use WLAN)
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Technical Issues (2)
Multiple IP registrations– Register the active IP address
– Forking proxy
De-Register with the previous SIP server once the active interface changes– Public SIP servers can be used with proper security association
Proper Triggering Mechanism to change active interface– Channel change,
– QoS of traffic,
– server based,
– L3 router solicitation
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DNS
DHCP
DHCP
DHCP
“Outdoor”
sun90
sun80.21
Domain:SN1
Domain:SN2
Domain:SN3
cisco80
cisco90
CompanyIntranet
InternetIGW
HUB
Private Subnet 1
Private Subnet 2
Private Subnet 3
PPP Server/Wireless ISP
CDMACDPD
802.11b
802.11b
802.11b
Outer sphereCDMA/CDPD network
SIP Proxy
MH
DMZ Network
CH
SIP Proxy
Cisco’s NAT
CH
MHSIP Client
SIP Client
DMZ Network802.11
SIP based Heterogeneous Mobility (802.11b and CDMA1xRTT)
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Experimental Setup and Results
Operating System– Windows XP and Linux
Multimedia Tools– RAT (Robust Audio Tool) for Audio,VIC (for Video)
Access Technologies– CDPD, CDMA1XRTT, 802.11b
Access hardware– Sierra Wireless 555, Kyocera 2235 with serial cable
End-to-end delay– 450 msec using ping measurement over 1xRTT(16 hops) to Columbia Univ.– 50 msec via 802.11b to Columbia Univ.
Throughput:– 10-15 kbps on file transfer using TCP (Linux) - Indoor– 25 Kbps on file transfer using TCP - outdoor– 30 kbps video streaming using RTP (windows) - indoor, ~60 kbps outdoor
Handoff Latency including IP address acquisition– Switching from WLAN to CDMA (Linux ~ 10 sec (PPP overhead) (Windows ~ 20sec)– Switching from CDMA to WLAN (Linux ~ 5 sec (ARP on)) (Windows ~15 sec)
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Conclusions
SIP based mobility for Heterogeneous Access Network has been realized in a test-bed for both indoor and outdoor network
It provides an end-to-end mobility solution without anything in the middle of the network such as home agent or Foreign Agent
It avoids triangular routing reducing the handoff delay SIP based mobility is independent of L2 handoff and IP address
acquisition issues SIP mobility on Linux platform provides a faster handoff for real-
time traffic compared to Windows XP ( probably a 802.11b driver issue)
In case of simultaneous bindings active IP address detection can be policy based