R93922010 Sheng-kai Lin R93922025 Jun-Cheng Chen R93922044 Jun

Lin, Chen, and Xie@NTUCSIE 2005 1

Mobile SIP IntroductionR93922010 Sheng-kai LinR93922025 Jun-Cheng ChenR93922044 Jun-Wei Xie


References (I)

• E. Wedlund, H. Schulzrinne, “Mobility support using SIP”, 2nd ACM/IEEE International Conference on Wireless and Mobile Multimedia, Seattle, Washington, Aug. 1999– http://www.argreenhouse.com/sip-mobile/

• H. Schulzrinne, E. Wedlund, “Application layer mobility using SIP”,Mobile Computing and Communications Review, Volume 4, Number 3


References (II)

• Dimitra Vali, Sarantis Paskalis, AlexandrosKaloxylos, Lazaros Merakos, An Efficient Micro-Mobility Solution for SIP Networks, GLOBECOM 2003

• Dimitra Vali, Sarantis Paskalis, AlexandrosKaloxylos, Lazaros Merakos, A SIP-based Method for Intra-Domain Handoffs, Vehicular Technology Conference, 2003. VTC 2003-Fall


Outline

• Introduction• Mobile SIP• Micro-mobility Scheme for Mobile SIP • Comparison between Mobile IP and

Mobile SIP


Introduction

• Mobile SIP• Support IP mobility at application layer

• Only a few modifications are needed• SIP can intrinsically handle user mobility via

URI• Easy for widely deployment


Mobility Types

• Four types: terminal, service, personal, and session mobility.

• Terminal mobility – It enables an end user to access the network even

when the point of attachment of the terminal to the network changes.

– The objective is to enable the user to maintain any ongoing session (s), while roaming across networks.


Mobility Types

• Service mobility– It enables an end user to have undisrupted

access to services even when the user moves or changes network service providers.

• Personal mobility – It allows an end user to maintain contact and

to access subscriber services even with another terminal


Session Mobility

• Session mobility allows a user to maintain a media session even while changing terminals.


Outline


Mobile SIP


SIP Support for Terminal Mobility

• SIP-based mobility is less suitable for TCP-based applications

• Does not require to add capabilities to existing operation system nor the installation of home agents or dynamic DNS update in the user’s ISP.


Pre-Call Mobility

• The mobile host acquires a new address prior to receiving or making a call.

• The MH simply re-registers with its “home” registrar each time it obtains a new IP address.

• The only problem is the ability to detect when the IP address has changed.


Mid-Call Mobility (I)

• The moving MH sends another INVITE request to the correspondent host, without going through any intermediate SIP proxies.


Mid-Call Mobility (II)

• Fast hand-off:– MH advertise the address of the proxy or an

RTP translator affiliated with the proxy as the media destination

– The proxy rewrite the network address in the session description

– The RTP translator intercepts the media packets and directs them to the current location of the MH


Network Partition

• If the network partition lasts less than about 30 second, SIP will recover without further mechanisms.

• If the network partition lasts longer, each side should address the SIP INVITE request to the canonical address, the home proxy of the other side.


Hierarchical Registration


Service Mobility

• Service mobility allows users to maintain access to their services even while moving or changing device and network service providers.

• The architecture is predicated on having a “home” server, associated with the user’s address

• Only user’s end system can be used to propagate service information


Service Mobility (continued)

• Registration conveys tree pieces of information:– Current network address– Properties of the device– One or more user configuration elements

• User agent also upload its timestamped version of the configuration information


Personal mobility

• Personal mobility allows to address a single user located at different terminals by the same logical address.– URI


Session Mobility

• In the simplest approach, end system are configured by the primary end system, which then conveys their IP and ports to the other party using a new INVITE request.


Session Mobility –Third-party call control


Session Mobility –Call transfer

• Using REFER request, end system indicates the other end system to the correspondent host

• Correspondent host then negotiates a session with the new end system with regular INVITE request


Outline


Mobile SIP


Why the Micro-scheme ?

• The connection reestablishment after a hand-off results in long delay and signaling overhead.– The micro-mobility scheme is needed to

handle intra-domain handoffs.• QoS issue for Mobile IP and Mobile SIP

– The micro-mobility schemes can facilitate fast local establishment of reserved resource while preserving the backbone reservations.


HMSIP

• Hierarchical Mobile SIP– “An Efficient Micro-Mobility Solution for

SIP Networks, GLOBECOM 2003”– Reduce the delay and minimize the overhead

of the intra-domain.– Combine other effort for QoS flow


HMSIP Overview

• Build on previously mentioned “SIP Hierarchical Registration”

• A border entity (Mobility Agent, MA) is responsible for intra-domain mobility


HMSIP (II)

• There’re two address to a MH– Local Address, LA– Global Domain Address, DA

• Global routable IP address

• The SIP MA enhanced with the functionality of a SIP Proxy/B2BUA and a SIP Registrar.


Registration

• Build on previously mentioned “SIP Hierarchical Registration”

• Power on in a visiting domain– Local address allocation– Regional registration– Domain Address Allocation– Home Registration


Registration (Conti.)

• Incoming SIP calls are directed to DA.• Encapsulation of respective SIP signaling

for incoming and outgoing SIP calls takes place inside the domain between the SIP MA and the current location (LA) of the MH


Intra-domain hand-off

• When handing off to a new AR, it compares the address of MA to decide if in the same domain.

• Updating the DA-LA mapping is required when intra-domain hand-off occurrs.


Inter Domain handoff

• A new LA is allocated by AR and a new DA by SIP MA.

• The session reestablishment takes place for on-going SIP sessions.

• CH is informed the new address of MA


QoS Flows (I)

• In QoS-enabled communication, reserved resources are often needed to maintain the QoSguarantees of the flows.

• In mobility situations, where the IP address of any of the endpoints changes, reservations need to be re-established end-to-end


HMSIP and Mobility of QoSFlows (II)

• HMSIP is similar in concept to other mirco-mobility protocols, it retains the benefit of a constant IP for movement inside the domain.– No modifications are required for RSVP-

enabled routers in the exterior network.


Outline

• Introduction• Mobile SIP• Micro-mobility Scheme for Mobile SIP• Comparison between Mobile IP and

Mobile SIP


Mobile IP (I)

• Mobile IP– Pros

• It makes mobility transparent to layers above IP and also enables the maintenance of active TCP connections.

– However, Mobile IP has some well-known limitations, especially when it comes to multimedia applications.


Mobile IP (II)

• Cons:– Triangle routing

• It increase the latency by 45% within a campus– Tunneling overhead

• An 20-byte IP header will be added to each packet

– Imperfections of route optimization– Mobile node needs a permanent home

address.


Home Agent (HA)

CorrespondentNode (CN)

Mobile Node (MN)

Packets to MN are picked up by the HAand tunneled to MN

Packets sent by MN godirectly to CN

• Triangle Routing in Mobile-IP


Home Agent (HA)

CorrespondentNode (CN)

Mobile Node (MN)

• Triangle Routing in Mobile-IP

C

A B

Triangular routing can be very inefficient, especially whenC << B+A, where A (as shown) is the shortest path fromCN to MN



Mobile SIP (I)• Pros

– Packet tunneling and modification of protocol stack in the MN are not required

– Improve the performance of real-time application

– The use of Mobile SIP could also compensate for the current lack of wide deployment of Mobile IP


Mobile SIP (II)

– Cons• TCP connection will break during handoff• SIP based IP mobility support requires some

modification on the kernel level to trigger location registration in the application layer protocol from detection of L2 handoff.


Mobile IP vs Mobile SIP


Mobile SIP with (Mobile) IP• Mobile SIP can be combined with IP or with

Mobile IP• Mobile SIP with IP

– Breaks TCP connections• Mobile SIP with Mobile IP

– TCP connections are OK, but is inefficient– Duplicated network functionality and stored user

data• Mobile SIP with IP and Mobile IP

– With IP for UDP communications and short-lived TCP connections

– With Mobile IP for long-lived TCP connections


Mobile IP vs Mobile SIP (I)

Optimized routing without tunneling

Triangular routing with tunneling

Routing

Logical address and contact address

Home address and care-of-address

AddressApplication layerNetwork layerLayerNon-transparentTransparentMove type

Mobile SIPMobile IP


Mobile IP vs Mobile SIP (II)

Application LayerModify TCP/IP Implementation difficulty

End-to-end and registration server

Through home agent

Address resolution

Mobile SIPMobile IP


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R93922010 Sheng-kai Lin R93922025 Jun-Cheng Chen R93922044 Jun