GB2412543A

GB2412543A - Method for mobility related riggering of SIP registration.

Info

Publication number: GB2412543A
Application number: GB0405779A
Authority: GB
Inventors: Ammad Akram; Makis Kasapidis; Nikolaos Prelorentzos
Original assignee: Matsushita Electric Industrial Co Ltd
Current assignee: Panasonic Holdings Corp
Priority date: 2004-03-15
Filing date: 2004-03-15
Publication date: 2005-09-28
Anticipated expiration: 2024-03-15
Also published as: GB2412543B; GB0405779D0

Abstract

In FMIP Handover from one network to another, a MN generates a signal to trigger SIP registration with the new network in response to the MN sending a mobility relates signal to the new network.

Description

1 2412543 Method for mobility related triggering of SIP registration This

invention relates to mobile communications and in particular it relates to using mobility protocol triggers from Mobile Internet Protocol (MIP) and Fast Mobile Internet Protocol (FMIP) to initiate registrations for the Session Initiation Protocol (SIP).

Introduction

Figure l shows a dual mode WLAN (Wireless Local Area Network) - UMTS (Universal Mobile Telecommunications System) mobile node (MN) wireless terminal with an ongoing session indicated by the solid line that has been established between a corresponding node (CN) in the caller's network via the Internet and WLAN networks. The media path between the CN and MN, established using the SIP (Session Initiation Protocol, International Engineering Task Force RFC 3261) signalling protocol, can, for example, be used to transport data packets related to Internet telephone calls (VoIP), multimedia distribution and multimedia conferences. Initially, the final leg of this media path is through the WLAN network and the MN is reachable through the Internet Protocol address denoted by IP1.

This IP address can be acquired through auto-configuration or with the assistance of a network element such as a DHCP (Dynamic Host Configuration Protocol) server. The MN needs to register a newly acquired IF address within the network of SIP servers to obtain SIP service. In the case of the WLAN network shown in Figure l, the MN registers the IP1 address with the local WLAN network SIP server where a binding is formed between the IP1 address and the MN unique SIP identity called the Uniform Resource Identifier (URI), e.g., sip:MN(home_network.com.

This binding is also transferred and maintained within the MN home network SIP server. Regular updates to this binding ensure optimised SIP performance through efficient routing of SIP messages and, subsequently, also direct IP routing of any negotiated media paths.

Now consider that for reasons of mobility or some other reason, e.g., deteriorating quality of the established media path through the WLAN network, the MN moves away from the WLAN network and instead enters the coverage of the UMTS network. A network layer mobility protocol is required to transparently maintain the ongoing SIP session in switching between the WLAN and UMTS networks. Mobile IPv4 [IETF RFC 3344] and MIPv6 [draft-ietf-mobileip-ipv6-24.txt] are two well-known examples of a suitable mobility protocol. However, the present invention focuses on an enhanced version of MIPv6 called Fast Mobile IP (FMIP) [draft-ietfmobileip-fast-mipv6-07.txt] that is being developed by the IETF MIPSHOP working group to handle handovers for real-time applications such as VoIP.

Mobile IP is based on the use of a static Home Address (HoA) that is associated with the MN home network. An entity known as the Home Agent (HA) entity in the MN's home network intercepts data packets addressed to the HoA in the absence of the MN and forwards them to the MN's new network upon notification of the MN's new IP address. The process of sending the MN's new IP address to the HA is called a binding update. Provision of network mobility modifies the SIP registration process. Instead of the actual newly acquired IP address being registered with the local SIP server as explained above, the MN instead registers its HoA. This leads to circuitous routing of SIP messages and encapsulated data routing in all cases where the MN is roaming outside of its home network.

WO02103951 seeks to mitigate such inefficiencies with the introduction of a new network element (access node) having both MIP and SIP functionality that the MN uses to connect to the core network. Another way of addressing the above inefficiencies without resorting to additional network elements is through the use of dynamic home agents whereby the MN discovers and uses the services of a HA in a visited network. The MN now registers its newly acquired IP address with the local SIP server in all cases enabling direct routing of SIP messages. Encapsulation of data traffic only occurs if the MN leaves the visited network to join another network.

The present invention seeks to provide an efficient method to trigger the SIP registration of the MN with the local SIP server.

With reference to Figure 1, once the MN joins the UMTS network and acquires a new IP address (IP2), it has to register this address with the local SIP server (in this case the SIP server of the UMTS network). This assumes that dynamic HAs will be used for providing network mobility.

With static HA, the MN simply registers its HoA. In either case, a local SIP registration is required for location management purposes, just the registered address is different in the two cases.

It is essential that the IP2 address is registered as soon as possible to ensure that new calls to the MN are handled efficiently. The present invention seeks to synchronise the SIP registration process with the handover process, with particular emphasis on FMIP handover.

An example of the invention will now be described with reference to the accompanying drawings in which like parts are designated like reference numerals and in which, Figure 1 schematically illustrates, first and second communication links between a mobile node and a corresponding node.

Figure 2 illustrates steps I to 10 of the signal flow diagram required to complete handover using FMIP and reroute data between the two

communication links according to prior art.

Figure 3 illustrates steps 8.1 to 8.2 of the signal flow diagram for the MN to trigger SIP registration on the new communications link.

The process of handing over the MN from WLAN to UMTS using FMIP occurs in a number of distinct steps whose timing is shown in Figure 2.

Each step is now described in detail.

Step 1 - data packets are initially being transferred between CN and MN through the ALAN network Step 2 - the MN sends the Router Solicitation for Proxy (RtSolPr) to the WEAN Access Router (AR) requesting information for the impending handover Step 3 - the WLAN AR sends the Handover Initiation (HI) message to the UMTS Serving GPRS (General Packet Radio Service) support node (SGSN) requesting the new care of address (nCoA) that will be assigned to MN on the UMTS network Step 4 - the nCoA is provided within the Handover Acknowledgement (HACK) message from the UMTS SGSN to the WLAN AR Step 5 - the nCoA is passed on to the MN within the Proxy Router Advertisement (PrRtAdv) message from the WLAN AR Step 6 - the Fast Binding Update (FBU) message is sent from the MN to notify the WLAN AR that it is about to move to the UMTS SGSN. The arrival of the FBU at the WLAN AR is the trigger to initiate tunnelling procedures between WLAN AR and UMTS SGSN Step 7 - the arrival of the Fast Binding Acknowledgement (FBAck) from the WLAN AR at the UMTS SGSN is the signal for the UMTS SGSN to start buffering tunnelled data Step 8 - the MN issues a Fast Neighbour Advertisement (FNA) to the UMTS SGSN upon arriving at the UMTS network to claim the nCoA and associated buffered data Step 9 - the MN issues a Binding Update (BU) via the UMTS SGSN to both its HA and CN to route the data directly via the UMTS network and tearing down the tunnel in the process Step 10 - data transfer between the CN and MN is now routed via the UMTS network This completes the FMIP handover and data re-routing steps. The present invention seeks to use the final steps of the FMIP handover process to trigger SIP registration of the nCoA being used by the MN on the new UMTS network. This process, triggered after the transmission of the FNA by the MN (step 8, Figurel), occurs in a number of distinct steps whose timing is shown in Figure 3. Each step is now described in detail.

Step 8.1 - an interrupt is generated within the MN upon transmission of the FNA by the MIP layer (In general terms, an interrupt is a variable set by one layer to a particular value that is detected by another layer leading to a specific action.) Step 8.2 - the interrupt is recognised by the MN SIP layer resulting in the triggering of the SIP registration of the MN with the SIP server in the UMTS network It is also possible that steps 8.1 to 8.2 could be triggered by an interrupt generated by the transmission of the BU message (step 9, Figure 2). The BU message is also part of the standard MTPv6 protocol, making the invention equally applicable in the case where MTPv6 is used for network mobility in preference to FMIP.

Claims

Claims 1. A method of initiating a mobile node (MN) SIP registration

following Mobile IP (MIP) related handover of the MN to a new network in which a signal to trigger the SIP registration is generated by the MN in response to the transmission of one or more mobility related signals from the MN.
2. A method as claimed in claim 1 in which the signal to trigger SIP registration is generated in response to the transmission of a mobility related signal from the MN to a node of the new network.
3. A method as claimed in claim 1 or 2 wherein the signal to trigger SIP registration is an interrupt generated by the MN at the mobility layer.
4. A method as claimed in claim 3 wherein the MN mobility layer interrupt is recognised by the MN SIP layer.
5. A method as claimed in claim 4 wherein the MN SIP layer initiates a SIP registration in response to the presence of the MN mobility layer interrupt.
6. A method as claimed in any preceding claim wherein the signal to trigger SIP registration is generated in response to the transmission of the MIPv4/v6 BU message from the MN.
7. A method as claimed in any of claims 1 to 5 wherein the signal to trigger SIP registration is generated in response to the transmission of the FMIP FNA message from the MN.
8. Any of the methods substantially as hereinbefore described with reference to figure 3 of the accompanying drawings.