MOBILE IP WORKING GROUP Sebastian Thalanany Ajoy Singh Internet Draft Motorola Document:draft-thalanany-mobileip-qh-00.txt July 2000 Category:Standards Track Quick handoff scheme in a 3G Wireless Network Status of this Memo This document is an Internet-Draft and is in full conformance with all provisions of Section 10 of RFC2026. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF), its areas, and its working groups. Note that other groups may also distribute working documents as Internet- Drafts. Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use Internet- Drafts as reference material or to cite them other than as "work in progress." The list of current Internet-Drafts can be accessed at http://www.ietf.org/ietf/1id-abstracts.txt The list of Internet-Draft Shadow Directories can be accessed at http://www.ietf.org/shadow.html. 1. Abstract This draft proposes a scheme to for a quick handoff of a mobile station (MS) from a source packet data-serving node (PDSN) to a target PDSN. The scheme utilizes the information available from the air-interface signaling messages necessary for the hard handoff over the wireless link. 1.1 Problem Packets that are destined for the MS, via the source PDSN cannot reach the MS if the MS has changed its attachment point, from a source PDSN to a target PDSN, in the meantime. The Route optimization draft [3] addresses this problem using a network triggered smooth handoff mechanism. For a smooth handoff, the new foreign agent (PDSN) reliably notifies the previous foreign agent (PDSN) about the new mobility binding of the MS when a Registration Request message with the foreign agent notification extension is received from the MS. This information is used by the previous foreign agent (PDSN) to forward the datagrams destined for the MS from the correspondent node to the new foreign agent. The foreign agent extension of Registration request message contains the necessary information required to contact the old foreign agent. The route optimization scheme uses network layer trigger (Registration Request message) to initiate smooth hand over Thalanany,Singh Standard Track û Dec 2000 1 Mobile/IP Quick Handoff Scheme July 2000 process, so it has all the inherent latency problems of existing hand over mechanism which makes it not so suitable for wireless system where low hand over latency is desired. This draft describes a link layer assisted quick handoff process for a cdma2000 based cellular system. The proposed scheme may be generalized for any wireless system with low hand over latency requirement. 1.2 Proposed solution The quick handoff scheme proposed in this draft solves the problem of performance degradation resulting from packet losses and non- tolerable delay that occur during the handoff of the MS between a source PDSN and a target PDSN. This draft proposes a new interface between the source PDSN and the target PDSN. The quick handoff scheme utilizes the information available via the wireless link layer to assist the handoff of the MS between the source PDSN and the target PDSN at the network layer. The proposed scheme is different from the network layer based handoff schemes. 2. Conventions used in this document 2.1 Requirements keywords The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in RFC-2119 [1]. 2.2 Terminology HA Home Agent MSC Mobile Switching Center PCF Packet Control Function PDSN Packet Data Serving Node PDSNs Source PDSN PDSNt Target PDSN RNC Radio Network Controller RNN Radio Network Node RF Radio Frequency RP Interface between the PCF in the RNN and the PDSN STP Interface between the source and target PDSN 3. Introduction The high level architecture for the quick handoff scheme in a third generation cdma2000 network is shown in Figure 1. Thalanany,Singh Standard Track û Dec 2000 2 Mobile/IP Quick Handoff Scheme July 2000 +---------+ +----+ Air-interface +-------+ RP | | | MS |---------------| RNN |---------| PDSNs |---------+ +----+ +-------+ | | | +---------+ | | | | |MS | +------+ |migration |STP | HA | | | +------+ V | | +---------+ | +----+ Air-interface +-------+ RP | | | | MS |---------------| RNN |---------| PDSNt |---------+ +----+ +-------+ | | +---------+ Figure 1: Third Generation cdma2000 network with the STP interface In Figure 1, the traffic between the PDSN and the RNN are transported as GRE encapsulated packets over the RP interface. The RNN is responsible for handling the traffic to and from the MS over the air- interface. The RNN contains the RNC and the PCF entities. The packets that are destined for the MS from the PDSNs cannot reach the MS if the MS has changed its attachment from PDSNs to the PDSNt, before these packets have been conveyed to the MS via the RP interface and the air-interface. The objective of the proposed quick handoff scheme is to minimize the packet losses and delay as a result of a handoff. This objective is realized by acquiring and using the IP address of the PDSNs contained in the air-interface signaling necessary to facilitate the hard handoff of the wireless link between the RNN and the MS. 4. Quick handoff scheme In a cdma2000 third generation wireless network the PDSN performs the functions of an FA (Foreign Agent) to support the handoff of the MS based on Mobile IP [1]. This section describes the proposed scheme, new extensions and a new interface. 4.1 Acquisition of the PDSNs IP address The trigger for the hard handoff of the MS is obtained from the RNN to which the MS is currently attached. The signaling messages necessary to support a hard handoff are based on the IS-2000 standard. Thalanany,Singh Standard Track û Dec 2000 3 Mobile/IP Quick Handoff Scheme July 2000 When the RNN receives an RF signal strength report from the MS, the source RNN may recommend a hard handoff to a target RNN within the serving area of the same MSC (Mobile Switching Center), using the Handoff Required message. In the event of a hard handoff recommendation the source RNN sends the Handoff Required message to the governing MSC. The governing MSC processes the Handoff Required message, and sends the Handoff Request message to the selected target RNN in the vicinity of the migration path of the MS. The PDSNs IP address is transferred to the target RNN via the Handoff Required and the Handoff Request messages. The target RNN transfers the PDSNs IP address, via the RP interface, to the PDSNt using an extension to the RP signaling protocol. 4.2 Acquisition of packets destined for the MS from the PDSNs The PDSNt uses the PDSNs IP address to register with the PDSNs, via the STP interface using a signaling scheme based on the RP signaling protocol. The registration reply from the PDSNs is used to transfer any packets buffered at the PDSNs to the PDSNt. 4.3 Hard handoff signaling extension The RNC in the target RNN sends the PDSNs IP address extension as a part of the A9 Setup A8 signaling message defined in the IOS4.0 [2]. 0 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Type | Length | Reserved | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | PDSNs IP Address | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Figure 2: Hard handoff signaling extension 4.4 RP signaling protocol extension The target RNN sends the PDSNs IP address extension as a part of the Registration Request defined in the RP signaling protocol defined in the IOS4.0 [2]. 0 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Type | Length | Reserved | Reserved | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | PDSNs IP Address | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Figure 3: RP signaling protocol extension Thalanany,Singh Standard Track û Dec 2000 4 Mobile/IP Quick Handoff Scheme July 2000 Type TBD (To be assigned by IANA). Length Length in bytes of this extension, not including the Type and Length bytes. Reserved This field is set to 0. Reserved for future enhancements. 4.5 STP interface This interface exists between the PDSNs and the PDSNt so that the PDSNt can acquire any packets that were buffered at the PDSNs. This interface is based on the RP signaling interface. 4.6 Signaling message sequence The signaling message sequence for the quick handoff scheme is shown in Figure 4. RNNsource MSC RNNtarget PCFtarget PDSNtarget | | | | | | | | | | | | | | | |Handoff | | | | |Required | | | | |----------->| | | | | |Handoff | | | | |Request | | | | |----------->| | | | | | | | | | | A9 Setup A8 | | | | |------------->| | | | | | | | | | | A11 Registration | | | | | Request | | | | |----------------->| Figure 4: Quick handoff signaling message sequence The reference for the messages shown in Figure 4, are indicated in this section. Handoff Required û This message contains the PDSNs IP address and is defined in [2]. Handoff Request - This message contains the PDSNs IP address and is defined in [2]. A9 Setup A8 - This message is defined in [2], and contains the PDSNs IP address extension described in section 4.3. A11 Registration Request û This message is defined in [2], and contains the PDSNs IP address extension described in section 4.4. Thalanany,Singh Standard Track û Dec 2000 5 Mobile/IP Quick Handoff Scheme July 2000 5. Security Considerations The PDSNs IP address extension proposed in this draft is based on the RP signaling protocol. The security measures defined in the RP signaling protocol are applicable. 6. IANA Considerations This draft proposes one new extension to the RP signaling protocol. The PDSNs IP address extension specified in section 4.4 MUST be assigned the Type value TBD. 7. References [1] C. Perkins. IP Mobility Support. Request for Comments (Proposed Standard) 2002, Internet Engineering Task Force, October 1996. [2] Inter-operability Specification (IOS) for CDMA 2000 Access Network Interfaces (PN-4545), version 4.0, June 2000. [3] C. Perkins and D. Johnson, "Route Optimization in Mobile IP", draft-ietf-mobileip-optim-09.txt (work in progress), February 2000. 8. Acknowledgments The authors of this draft would like to thank the contributors to the information contained in: Inter-operability Specification (IOS) for CDMA 2000 Access Network Interfaces (PN-4545), version 4.0, June 2000. We would like to thank Phil Roberts for encouraging us to make this contribution. 9. Addresses The working group can be contacted via the current chairs: Basavaraj Patil Phil Roberts Nokia Corporation Motorola M/S M8-540 Thalanany,Singh Standard Track û Dec 2000 6 Mobile/IP Quick Handoff Scheme July 2000 6000 Connection Drive 1501 West Shure Drive Irving, TX 75039 Arlington Heights, IL 60004 USA USA Phone: +1 972-894-6709 Phone: +1 847-632-3148 EMail: Raj.Patil@nokia.com EMail: QA3445@email.mot.com Fax : +1 972-894-5349 Questions about this memo can be directed to: Sebastian Thalanany Motorola 1475 West Shure Drive Arlington Heights, IL - 60004 Phone: (847)435-9296 Email: sthalan1@email.mot.com Ajoy Singh Motorola 1501 West Shure Drive Arlington Heights, IL û 60004 Phone: (847)632-6941 Email: asingh1@email.mot.com Thalanany,Singh Standard Track û Dec 2000 7 Mobile/IP Quick Handoff Scheme July 2000 Full Copyright Statement "Copyright (C) The Internet Society (date). All Rights Reserved. This document and translations of it may be copied and furnished to others, and derivative works that comment on or otherwise explain it or assist in its implementation may be prepared, copied, published and distributed, in whole or in part, without restriction of any kind, provided that the above copyright notice and this paragraph are included on all such copies and derivative works. However, this document itself may not be modified in any way, such as by removing the copyright notice or references to the Internet Society or other Internet organizations, except as needed for the purpose of developing Internet standards in which case the procedures for copyrights defined in the Internet Standards process must be followed. Thalanany,Singh Standard Track û Dec 2000 8