Transcript Link Layer Assisted Mobility Support Using SIP for Real

Link Layer Assisted Mobility Support
Using SIP for Real-time Multimedia
Communications
October 1, 2004
Wooseong Kim, Myungchul Kim, Kyounghee Lee
Chansu Yu
Ben Lee
Information and Communications Univ.
Cleveland State Univ.
Oregon State Univ.
{wskim, mckim, leekhe}@icu.ac.kr
[email protected]
[email protected]
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Contents

Introduction

Related Work

Problem Definition

Motivation

Proposed Scheme

Experiments

Conclusions & Future Work

References
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Introduction


Network layer mobility support
–
Mobile IP, Cellular IP, HAWAII, etc.
–
Transparent to upper layers, static home IP address
–
Packet encapsulation overhead, security problem due to tunneling
Application layer mobility support
–
Mobility Support using SIP [Wedlund 99]
–
Deployable without additional sub systems or modifications on the existing
network environment
–
Dynamic temporal address whenever a network is changed
–
Supports various types of mobility with a single protocol (e.g., personal
mobility and service mobility in SIP)
–
Generality for UDP based real-time applications
–
IP address allocation due to a handoff takes several seconds [Dutta 01]
inappropriate for real-time communications
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Related Work

Functions of SIP Terminal Mobility [Wedlund 99]
•
•
Pre-call mobility
Mid-call mobility
–
–
–
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Home location server manages current address of mobile host
INVITE (455 bytes) RINGING (233 bytes) OK (381 bytes) ACK (216 bytes)
messages [7]
Using home SIP redirect or proxy server
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Related Work (cont’d)

Functions of SIP Terminal Mobility (cont’d)
•
SIP terminal registration
–
–
–
•
Error recovery
–
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Fast registration to reduce disconnection in pre-call mobility
About 150ms to complete whole re-registration procedure
Regional mobility support by hierarchical registrars
To resolve simultaneous movements of both communication ends
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Problem Definition

Handoff delay of SIP mid-call
mobility [12]
MN
DHCP
RTP session disconnect
CN
T0
L2 Handoff
Finish
– Handoff Delay = Tn (n=0 to 5)
Link layer handoff delay (T0)
Movement Detection (T1)
DHCP transaction (T2)
Configuration time (T3)
re-INVITE (T4)
RTT/2 (T5)
DHCP [2]: T2 > 1 sec,
DRCP [8]: T2 = 100 ~ 180 ms [7,10]
Total handoff delay of SIP mid-call
mobility is not adoptable to real-time
applications
Discove
T1
ry
Offer
R e q u e st
ACK
T2
T3
RE-INV
ITE
RTP pa
ckets
OK
200
pa
RTP
Handoff Delay
–
–
–
–
–
–
–
–
–
L2 Handoff
Start
T4
ckets
T5
< SIP Mobility Handoff Flow >
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Problem Definition (cont’d)

MN
Simultaneous movement
Problem
L2 Handoff
Start
– Total registration delay = address
allocation time + SIP home registration
time + re-INVITE time
MN’s SIP
Server
CN
E
NVIT
RE-I
Move
Discove
ry
Offer
R e q u e st
ACK
Mo
ve
Error Recovery Delay
– Error recovery latency = several
hundred ms ~ a few seconds
DHCP
RE-INV
ITE
Registra
– INVITE retransmission takes much
time as far as home network is
tion
200 OK
ITE
INV
E
INVIT
200 OK
< SIP Mobility Error Recovery >
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Motivation

To improve SIP mid-call terminal mobility
•
•

Reduce handoff delay of mid-call mobility by removing address
allocation time (T2) and re-INVITE delay (T4)
Reduce error recovery latency due to simultaneous movement
problem
Proposal for enhancement
•
•
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Application layer uses link layer (L2) information to reduce the handoff
latency
Predictive Address Reservation with SIP (PAR-SIP) scheme to
perform the address allocation procedure and SIP session renewal
before a handoff
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Proposed scheme: PAR-SIP

Link layer assisted handoff prediction
•
•
Build link layer information by scanning neighbor access points (AP) at
wireless LAN [15, 16, 17]
Select predictive AP and start proactive handoff procedure at CPT
SNR
1
AP1
AP2
Cell Search
Threshold
Delta
Cell Prediction
Threshold
Cell Switch
Threshold
A
CPT
B
Mobile node
movement direction
< Handoff between AP1 and AP2 >
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Proposed scheme: PAR-SIP (cont’d)

Movement detection in MN and BS
•
•
•
•
MN’s Mobility Manager (MM) manages AP list of current subnet
(e.g.,shadow block)
MN sends reservation request if MAC address of predictive AP does
not exist in AP list (movement detection delay decreases)
BS’s MM manages neighbor BS information
BS replies corresponding AP list for subnet of a reserved address
Base station number
AP MAC address
Network ID
00:39:99:82:23:54
BS1
203.101.23.0/24
00:34:94:12:23:52
BS2
00:30:28:85:21:51
203.101.23.0/24
BS3
00:39:19:02:28:50
203.101.22.0/24
< Neighbor BS Information table>
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Proposed scheme: PAR-SIP (cont’d)

Address Reservation
•
•
•
MN requests address reservation to a new BS through a current BS
Address reservation is done before link layer handoff begins
Defined messages: RSVREQ, RSVACK, RSVNACK, L2HO and
TIMEOUT
DHCP
BS1
BS2
DHCP
2. DHCP Transaction
3.
1.
AP1
Re
se
r
Re
va
tio
n
se
r
Re
va
ti
on
Re
ply
quAP2
es
t
AP3
Mobile Node
< IP address reservation procedure >
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Proposed scheme: PAR-SIP (cont’d)

Advance re-INVITE to a peer
with a reserved IP address
•
•
•
•
Location
server
Send re-INVITE to a CN with a
reserved address before link layer
handoff starts
A CN sends packets to a current
address and a newly invited address
Solve simultaneous movement
problem by alerting new address
before handoff
Reduce packet loss during handoff
with bi-casting
Internet
CISCOSYSTEMS
CISCOSYSTEMS
1.SIP re-Invite
BS1
CN
2.OK
3.Traffic
BS2
MN
< Bi-casting from CN >
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Proposed scheme: PAR-SIP (cont’d)

Advance registration procedure
•
•
•
•
Reduce registration delay after handoff
Two addresses (current IP address
and reserved one) are temporarily
bound with single user.
Increase reachability of a MN in precall mobility because location server
always a valid contact address
Fast error recovery from advance
registration
Home
registrar
Internet
1.SIP registration
CISCO S YSTEMS
BS1
CISC O S YSTEMS
2.OK
BS2
Mobile
Node
< Advance registration >
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Proposed scheme: PAR-SIP (cont’d)
MN1

Handoff delay of PAR-SIP midcall mobility
Cell
Prediction
Threshold
cBS
nBS
MN2
RTP session
Address
Reserve
Discove
•
•
•
•
PAR-SIP handoff delay
= Tn ( n=0,1,3,5) < SIP handoff delay
DHCP transaction time(T2) and SIP reINVITE procedure time (T4) are
removed
Movement detection time (T1) is
diminished
T0,T3 and T5 is same as SIP terminal
mobility
ry
Offer
Request
ACK
s
Addres
Reply
Pre RE-INVIT
E
200 OK
RTP packets
kets
ac
RTP p
L2 Handoff
Start
RTP session disconnect
L2 Handoff
Finish
T1
T3
RTP pack
ets
T5
< PAR-SIP Mobility handoff flow >
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Handoff Delay
T0
Experiments

Implementation environment
•
•
•
•
•
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Base Station
– Pentium-350Mhz PC
– Access Point: Prism2 card with
HostAP driver [14]
Mobile Node
– Pentium-800Mhz Tablet
– Lucent WaveLAN card
– DHCP client 1.3.22 (ISC)
DHCP Server (in BS)
– DHCP 3.3a[18]
SIP Application
– Linphone 0.9.0 [20] in MN and
CN
Operating System
– Linux Redhat 7.2 (2.4.7-10)
CN
Testbed
Backbone
Base
station
Base
station
Network A
Network B
801.11b
AP1
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801.11b
AP2
MN
MN
801.11b
AP3
MN
< Testbed Diagram >
15
Experiments (cont’d)
Handoff Delay of Conventional SIP Mobility

•
•
SIP_Handoff_Delay =  Tn ( n=0 to 5) = 50 ms +5 ms + 1.35 sec + 10 ms + 10
ms + RTT/2  1.4 s.
Both nodes can not receive packets for 1.5 seconds. Rx delay of a MN is a little
longer than that of a CN due to re-INVITE delay
SIP_MN_RX
SIP_MN_TX
30
SIP_CN_RX
SIP_CN_TX
20
25
15
kbps
kbps
20
15
10
10
5
5
0
0
1
2
3
second
< MN transmission rate during Handoff >
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0
0
0.5
1
second
1.5
2
< CN transmission rate during Handoff >
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Experiments (cont’d)
Handoff Delay of PAR-SIP Mobility

PAR-SIP_Handoff_Delay =  Tn ( n=0,1,3,5) = T0+T1+T3+T5 = 50 ms +1 ms + 7
ms + RTT/2  60ms.
A MN transmission rate is a little shorter than a CN because a CN keeps bicasting for a MN during handoff
•
•
PARSIP_MN_RX
25
25
20
20
kbps
kbps
PARSIP_CN_RX
30
PARSIP_MN_TX
30
15
15
10
10
5
5
0
0
0
0.1
0.2
0.3
second
0.4
0.5
< MN transmission rate during Handoff >
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0.6
PARSIP_CN_TX
0
0.1
0.2
0.3
0.4
0.5
0.6
second
< CN transmission rate during Handoff >
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Experiments (cont’d)

Average transmission rate variation during handoff
•
•
PAR-SIP Mobility shows better transmission rate due to handoff than existing SIP
mobility while receiving 2500 packets.
PAR-SIP only drops by 2 kbps during handoff
PARSIP_MN_RX
SIP_MN_RX
16
14
12
kbps
10
8
6
4
2
0
0
500
1000
1500
2000
2500
packets
< Average transmission rate during handoff >
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Experiments (cont’d)

Packet loss
•
•
Low latency handoff and bi-casting can reduce the number of lost packets
Packet loss of PAR-SIP mobility using all kinds of codecs shows about 1% of
total packets comparing to 5% in conventional SIP mobility (handoff :4 times/sec)
7
6
rate(%)
5
4
3
2
1
0
GSM
LPC10
MULAW
ALAW
PARSIP_MN_RX
codec
PARSIP_CN_RX
SIP_CN_RX
SIP_MN_RX
SPEEX
< Packet loss rate Comparison>
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Conclusion & Future Work

Conclusion
•
Conventional approach of SIP showed high handoff latency that is not proper to
real-time communication
•
PAR-SIP mobility reduces total handoff delay to about 60ms by reserving an IP
address and requesting re-INVITE in advance
PAR-SIP mobility also reduces packet loss
PAR-SIP mobility can solve simultaneous movement problem with advance reINVITE and registration
Real-time communication can be available using application mobility
•
•
•

Future work
•
Develop superior algorithm to predict precisely potential AP
•
Measure error recovery delay using PAR-SIP
Implement advance resource reservation using RSVP in MM of BS
•
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References
[1] H. Schulzrinne et al, "SIP: Session Initiation Protocol”, RFC 3261 IETF, June 2002.
[2] R. Droms., "Dynamic Host Configuration Protocol”, RFC 2131 IETF, Mar. 1997.
[3] C. Perkins., "IP mobility support," RFC 2002 IETF Oct. 1996.
[4] C. Perkins and D. Johnson., "Route optimization in mobile IP" Internet Draft, IETF, Feb. 1999.
[5] Elin Wedlund, H. Schulzrinne., "Mobility Support using SIP" IEEE/ACM Multimedia conference WOWMOM 1999.
[6] Faramak Vakil, A. Dutta, J.C Chen, S. Bava, Y.Sobatake, Henning Schulzrinne, "Mobility Requirements in SIP
environment”,Internet Draft, IETF Work in progress.
[7] Ashutosh Dutta et al, “Application Layer Mobility Management Scheme for Wireless Internet”
[8] A.Mcauley, S.Das, S.Baba et al, “Dynamic Registration and Configuration Protocol” draft-itsumo-drcp-01.txt, IETF July
2000
[9] Melody Moh, “Mobile IP Telephony”, IEEE 1999
[10] David Famolari, “Performance Evaluation of ITSUMO Mobility Protocol for RTP/UDP Multimedia Session Across
Subnet Boundaries”, ICC 2001
[11] Baba. S et al, “Implementing a testbed for mobile multimedia”, GLOBECOM 2001
[12] Ted. K et al, “Mobility Management for VoIP service: Mobile IP vs. SIP”, IEEE Wireless Communications, Oct. 2002
[13] O.Casals, et. al., "Performance evaluation of the post-registration method, a low latency handoff in MIPv4 ”, ICC '03.
IEEE International Conference on , Volume: 1 , pp.522 -526, 2003.
[14] Host AP Driver - http://hostap.epitest.fi/.
[15] ANSI/IEEE Std 802.11, 1999 Edition.
[16] Lucent Technologies Inc., “Roaming With WaveLAN/IEEE 802.11”, WaveLAN Technical Bulletin 021/A, Dec. 1998.
[17] Lucent Technologies Inc., “IEEE 802.11 Channel Selection Guidelines”, WaveLAN Technical Bulletin 003/A, Nov.
1998.
[18] DHCP server- dhcpd. http://www.isc.org/products/DHCP/.
[19] Prism dump - http://developer.axis.com/software/tools/
[20] Linphone - http://www.linphone.org/
[21] A. G. Valk, “Cellular IP: A new approach to internet host mobility”, ACM Computer Communication Review, Vol. 29,
pp. 50-65, Jan. 1999.
[22] R. Ramjee, et. al., “HAWAII: A domain-based approach for supporting mobility in wide-area wireless networks”, in
International Conference on Network Protocols(ICNP), Nov. 1999.
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Thank You!
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