Optimized Fast-handoff Scheme for Application Layer Mobility

ManagementAuthors: Ashutosh Dutta, Sunil Madhani, Wai Chen

Telcordia Technologies

Henning SchulzrinneColumbia University

Onur AltintasToyota InfoTechnology Center

[First author is also a student at Columbia University]

Outline• Motivation• Intra-domain Mobility Management• SIP based Mobility Management

– SIP and Mobile IP– Fast-handoff for SIP Mobility

• Test-bed Realization• Experimental results

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

Motivation• Objective: Design and evaluate optimized techniques

based on Application Layer Mobility Management Scheme– Several Network Layer Scheme provide optimized handoff

techniques for Intra-domain mobility– Application Layer Mobility Management Scheme rules out the

need for networking components such as Home Agent/Foreign Agent

– SIP based mobility is an application layer scheme supporting Real-Time traffic for Mobile Wireless Internet

– It is essential to reduce transient real-time traffic during frequent handoffs

Network Layer fast-handoff approaches

• Intra-domain Mobility Management Protocol– Use of Mobility Agent to limit the Intra-domain

updates to within a domain

• Hierarchical Mobile IPv4/v6 Fast Hand-offs

• Foreign Agent Assisted Handoffs

• Intra-domain Mobility with buffering Agents

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:onur@toyota-itc.com

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

• 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

SIP mobility Performance snapshot in 802.11 Environment

Byte Sizes of SIP signaling Timing for Signaling messages

• INVITE - 455 bytes 100 msec processing time between msgs (OS dependent)

• Ringing - 223 bytes 5 msec for Invite to traverse

• OK - 381 bytes 70 msec for Re-Invite to traverse (mostly queuing delays)

• ACK - 261 bytes 150 msec for complete re-registration

• Bye - 150 bytes 300-400 msec for address acquisition without (SIP,MIP)

• De-Register - 370 bytes 3-4 sec for address acquisition with ARP (SIP,MIP)

• Re-Invite - 450 bytes

• Re-register - 425 bytes

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

SIPMM-MIP BW and Latency experimental

evaluationSIP vs MIP Utilization Gain (Experiment)

0.2

0.3

0.4

0.5

0 100 200 300 400 500 600 700 800 900 1000 1100

Bytes per packet

SIP

B/W

Gai

n SIP B/W Gain

SIP vs. MIP Latency (Experiment)

5

10

15

20

25

30

35

40

0 100 200 300 400 500 600 700 800 90010001100

Packet Size in bytes

La

ten

cy

in

ms

ec

SIP

MIP

27 msec

16 msec

~50%latency improvement

Cellular IPHomeHomeAgentAgent

CorrespondentHost

Internet(with Mobile IP)

Gateway AGateway A

Cellular IPNode

Cellular IPNode

CIPNode

CIPNode

CIPNode

CIPNode

Gateway BGateway B

Cellular IPNode

Cellular IPNode

CIPNode

CIPNode

CIPNode

CIPNode

Domain A

Domain B

MIP registration

CIP update

Media

Hierarchical Foreign Agent

GFA 1

FA1 FA2

HA

1

2

5

6

IP-based network

3

4

GFA 2

FA3

FA4

IP-based network

GFA

FA1 FA2

HA

1

2

3

4

GFA 1

FA1 FA2

HA

1

2

5

6

IP-based network

3

4

GFA 2

FA3

FA4

IP-based network

GFA

FA1 FA2

HA

1

2

3

4

HAWAII

Internet

Domain Root Domain Root RouterRouter

Domain Root Domain Root RouterRouter

BSBS

R R

R R R

BS

R R

R R

Domain 1Domain 2

TeleMIP’s Architecture LayoutIDMP/TeleMIP Architecture

Initial Domain-Based Registration Procedure

Subsequent Intra-Domain Registration

Mobility Proxy

SIP fast-handoff mechanism -RTPtrans

R

SIPServer

RT1RT2RT3

MHMHMH

IP1IP2IP3

CH

IPR1IPR2IPR3

Mapping Database

Register

1

IP1:p1IP2:p1

2’

DelaySimulator

(Med

ia)

2 (R

e-in

vite

)

IP2 -> IPR1IP3 -> IPR2...

3

Intra- Domain fast-handoffDomain -D1

4

(Med

ia in

flig

ht)

(Transient media)

RT1,RT2,RT3 - RTP Translators

4’

SIP fast-handoff RTPtrans - Protocol flow

MH CHSIPServer

Media

RT1 RT2 RT3

IP1

IP2

Re-Invite (2)Re-register 2’

Forward traffic(IP1:p1 ---> IP2:p1)

New traffic

IP3

Re-InviteRe-register

Forward traffic(IP2:p1 ---> IP3:p1)

Transient Traffic during the move

Fast-handoff Flow diagram

(1)

SIP-CGI (3)

Transient Traffic during the move

First move

Second moveIP2

Router CHDelaySimulator

SIPUAC

SIP MA (B2B)

MHMHMH

Med

ia

Invite

Move

Invite

Re-

Invi

te

SIP fast-handoff with B2B SIP UA – approach 1

IP1(Initial position before move)IP2IP3

IPch

SIPUAS

SIPUAS

SIPUAC

Invite B2B SDP

Media

Med

ia

Med

ia

Media

Flow diagram B2B approach –1(Limits Re-invite to B2B UA within a domain)

B2BUA

UA1 UA2MHMH

IP0IP1

RTP1

Re-Invite

MediaTransl-ator

RTP1 after the move

Invite

CH

RTP2

Invite

RTP2

ok

ack

ok

ack

Router CHDelaySimulator

SIPUAC

SIP MA (B2B)

MHMHMH

Med

iaInvite no SDP

Move

Invite

Invi

te

SIP fast-handoff with B2B SIP UA – approach 2

IP1(Initial position before move)IP2IP3

IPch

SIPUAS

SIPUAS

SIPUAC

Invite MH SDP

Med

ia

Med

ia

Fast handoff with B2B UA – approach 2 – flow diagram Re-invite from MH activates the interceptor at B2BUA

B2BUA

UA1 UA2MH CHMH

IP0IP1

RTP

Re-Invite

RTP1

Invite (no SDP)

Invite MH SDP

OK (MH SDP)

ACK CH SDP

OK

ACK

(Interceptor)

B2BUA- fast-handoff – approach 3 multicast agent

SIP B2B UA

M1 - local scoped multicast address

CH

MHMH

MulticastAgent

Subnet 0Subnet 1

(duration limited multicast)

Internet/DelayBox

B2BUA

UA1 UA2MH CHMH

IP0IP1

RTP

Re-Invite

RTP1

Invite (no SDP)

Invite MH SDP

OK (MH SDP)

ACK CH SDP

OK

ACK

Re-Invite with Maddr

Transient data at M addrRTP

B2BUA- fast-handoff – approach 3 multicast agent -flow

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 Mobility in a Test-bed

Sample Packet Trace for Fast Handoff(see notes page)

Sample Packet Trace for Mobility Proxy-based Handoff (see notes page)

Issues• Duplicate Packets Detection• Aging of RTP translator• Scalability

– Number of subnets is large– Mobile is moving too rapidly between the

subnets

• Mechanism to remove the virtual Interface• Mapping of subnets and RTPtranslators

Conclusions

• Application Layer fast-handoff mechanism discussed

• Test-bed Realization presented• Results of the experiments analyzed• RTP aging, scalability, effect of mobility rate

are future• Comparison with other network layer

approaches is helpful.