1

The Design and Implementation of Mobile Session Controller

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• Session Controller

• Network Mobility

• SIP & SIP Mobility

• NAT Traversal

• Our Enhancement on Session Controller to Support Mobility

• Future Work

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Session Controller

• Border

• Firewall

• NAT

• http://www.sessioncontrollerforum.org/

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Network Mobility

• http://www.ietf.org/html.charters/nemo-charter.html• Managing the mobility of an entire network • The mobile network includes one or more mobile ro

uters (MRs) which connect it tothe global Internet.– It could be multi-homed.– None of the nodes behind the MR will be aware of the net

work's mobility, thus the network's movement needsto be completely transparent to the nodes inside the mobile network.

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Network Mobility (2)

• A basic approach for network mobility support is for each Mobile Router to have a Home Agent, and use bidirectional tunneling between the MR and HA to preserve session continuity while the MR moves.

• The MR will acquire a Care-of-address from its attachment point much likewhat is done for Mobile Nodes using Mobile IP.

• In this paper, we propose to handle SIP-based sessions with SIP mobility instead of Mobile IP, which is a better choice for VoIP, because it removes the “triangular routing”.

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SIP & SIP Mobility

• Shiang-Ming will provide the viewgraph of pre-call mobility & mid-call mobility

• However, this seems to be redundant with the call flows below. Probably we only need to briefly introduce SIP in this section.

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AP

WiMAX

WiFi

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The MSC Architecture

External Ethernet Module

MIB

LogHandler

SNMPAgent

AuthenticationCenter

WGSN Node

OA&M

iSMSAS SIP

Redirect

RASServer

SIP-basedPush Center

GMMHandler

GrHandlerBilling

Handler

SS7Module

NetworkController

DHCP Server

Firewall

GPRSModule

HLR

GPRSNetwork

Wireless LAN

SS7Network

Internal Ethernet Module

ExternalPDN

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NAT Traversal on Session Controller

• Registration

• Call Setup– Call Origination– Call Termination

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NAT SIP ALG

mapping table

NAT Traversal for SC

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Registration

Session ControllerUA SIP Registrar

REGISTER

Contact: sip:ua@private_ip:5060

REGISTER

Contact: sip:ua@public_ip:12348

Allocate a port for UA

200 OK200 OK

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Call Origination

• Allocate public ports for UA.– The design of Mobile Session Controller should

adopt a port-restricted cone NAT.

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Call OriginationSession ControllerUA UA2

INVITE + SDP1

Reserve two contiguous ports for a media stream

INVITE + SDP1’

200 OK + SDP2

Add RTP ports to the ACL

200 OK + SDP2

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Call Termination

• Similar. Just draw another figure.

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Enhanced Session Controller to Support Mobility

• Pre-call Mobility

• Mid-Call Mobility

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Pre-Call MobilitySession ControllerUA SIP Registrar

SC detects IP address change and update the mapping table

200 OK

REGISTER

Contact: sip:ua@new_ip:12348

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Mid-Call MobilitySession ControllerUA UA2

INVITE (new Contact and Via) + SDP1” (new c=)

200 OK + SDP2

SC detects IP address change and update the mapping table

RTP

ACK

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Future Work