Network Working Group D. Liu Internet-Draft China Mobile Intended status: Informational J. Song Expires: September 8, 2011 W. Luo ZTE March 7, 2011 Distributed Mobility Management Signalling Analysis draft-liu-distributed-mobility-signalling-analysis-00 Abstract This document analysis the signalling overhead in distributed anchor scenario. Status of this Memo This Internet-Draft is submitted in full conformance with the provisions of BCP 78 and BCP 79. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF). Note that other groups may also distribute working documents as Internet-Drafts. The list of current Internet- Drafts is at http://datatracker.ietf.org/drafts/current/. 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." This Internet-Draft will expire on September 8, 2011. Copyright Notice Copyright (c) 2011 IETF Trust and the persons identified as the document authors. All rights reserved. This document is subject to BCP 78 and the IETF Trust's Legal Provisions Relating to IETF Documents (http://trustee.ietf.org/license-info) in effect on the date of publication of this document. Please review these documents carefully, as they describe your rights and restrictions with respect to this document. Code Components extracted from this document must include Simplified BSD License text as described in Section 4.e of the Trust Legal Provisions and are provided without warranty as described in the Simplified BSD License. Liu, et al. Expires September 8, 2011 [Page 1] Internet-Draft DMM Signalling Analysis March 2011 Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 2. Conventions used in this document . . . . . . . . . . . . . . . 3 3. Network based mobility management . . . . . . . . . . . . . . . 3 3.1. Signalling overhead . . . . . . . . . . . . . . . . . . . . 3 3.2. Conclusion . . . . . . . . . . . . . . . . . . . . . . . . 4 4. Client based mobility management . . . . . . . . . . . . . . . 4 4.1. Signalling overhead analysis . . . . . . . . . . . . . . . 4 4.2. Conclusion . . . . . . . . . . . . . . . . . . . . . . . . 5 5. Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . 5 6. Security Considerations . . . . . . . . . . . . . . . . . . . . 6 7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 6 8. Contributors . . . . . . . . . . . . . . . . . . . . . . . . . 6 9. References . . . . . . . . . . . . . . . . . . . . . . . . . . 6 9.1. Normative References . . . . . . . . . . . . . . . . . . . 6 9.2. Informative References . . . . . . . . . . . . . . . . . . 7 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 7 Liu, et al. Expires September 8, 2011 [Page 2] Internet-Draft DMM Signalling Analysis March 2011 1. Introduction When the core network gateways are deployed near to the access network for distributed purpose, the number of gateways will be increased in the same coverage area. Hence the user movement may lead to signalling cost caused by gateways relocation. This document analyzes the mobility management protocols of 3GPP 3G/LTE networks to present the detail effects of signalling cost in the case of distributed gateways. This signalling analysis includes two parts of mobility handling, one is the mobility management based on network, and the other is mobility management based on client. 2. Conventions used in this document 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 [RFC2119]. 3. Network based mobility management 3.1. Signalling overhead SGSN and GGSN are user plane gateways in 3GPP 3G network. SGSN also contains the functions of control plane, so it is not applicable to be distributed. Only the case of distributed GGSN is considered here. If the anchor GGSN is not changed, there is no difference compared to current centralized deployment even the GGSN is distributed. The signalling procedure is involved by user equipment because radio condition changes. If there is no change to radio access network deployment even the GGSN is distributed, both the radio signalling messages and core network signalling messages will not be increased. S-GW and P-GW are user plane gateways in 3GPP LTE network. P-GW is the anchor gateway and S-GW is the access gateway. The anchor gateway can not be changed when the user is moving, but the access gateway will be relocated from one to another. So the core network signalling cost is mainly increased by S-GW relocation. There is no radio signalling cost as 3G system described above. Table 1 indicates the detail signalling cost of different mobility management procedures. Liu, et al. Expires September 8, 2011 [Page 3] Internet-Draft DMM Signalling Analysis March 2011 +-------------------------------------------------------------+ |Assumptions | Scenario | Radio |Core network| Note | | | | signaling|signaling | | +-------------------------------------------------------------+ |Distributed |Idle TAU |no impact |4 signalling|S-GW numbers | |deployment | | |messages |increase lead| |of gateways | | |increase |to signalling| | | | | | increase | | |------------------------------------------------| | | | |4 signalling|X2 handover | | | X2 |no impact |messages |frequence | | |handover | |increase |increase | | |------------------------------------------------| | | S1 |no impact |6 or 14 |S1 handover | | | handover | |signalling |frequence | | | | | messages |increase | | | | |increase | | +-------------------------------------------------------------+ Figure 1: Centralized anchor model 3.2. Conclusion Impact to the radio interface:There is no extra signalling cost on radio interface when the gateways are distributed and the number of the gateways is increased. Impact to the core network:The gateway relocation will increase signalling cost, but the influence could be minimal. The possibility of gateways relocation will be increased when the gateways are distributed and the number of the gateways is increased. Hence the cost of extra signalling is little, and the influence on the core network equipment can be ignored. 4. Client based mobility management 4.1. Signalling overhead analysis This section takes DSMIPv6 as an example to analyze the signalling effects to client based mobility management due to distributed deployment of gateways. When the intra non-3GPP handover with DSMIPv6 procedures are initiated as defined in 3GPP specification, on the assumption of no change to the radio infrastructures (e.g. based stations) deployment, distributing non-3GPP access gateways should not increase the total frequentness of handover when the client Liu, et al. Expires September 8, 2011 [Page 4] Internet-Draft DMM Signalling Analysis March 2011 moves, but should increase the rate of the handover of crossing the non-3GPP access gateway (normally the authenticator of the client access authentication). The relocation of non-3GPP access gateway of the client would cause the local IP address re-allocation, and trigger the client re-authentication as well as DSMIPv6 binding update procedures. These procedures would increase the signalling messages to both radio access network and core network. +-------------------------------------------------------------------+ |Assumptions|Scenario| Radio |Core network | Note | | | | signaling |signaling | | +-------------------------------------------------------------------+ |Distributed|Trusted |authentication|authentication|gateways numbers| |deployment |non-3gpp|IPsec,BU/BA |signalling/ |increase lead | |of gateways| | |IPsec/BU/BA |to signalling | | | | |signalling | increase | | | | |increase | | | |-------------------------------------------------------| | | | |authentication|gateways number | | |Non- |authentication| |increase lead | | |trusted |IPsec,BU/BA | |to signalling | | | | | |increase | +-------------------------------------------------------------------+ Figure 2: Centralized anchor model 4.2. Conclusion Air interface overhead: In the case of inter gateway handover, the signalling messages for radio access network are increased with the gateways distributed, and the exact number of signalling messages is related to the wireless technologies of the radio access network. Core network overhead: In the case of inter gateway handover, the re- authentication and other update procedures should introduce more signalling messages than those of intra gateways handover; With number increase, the distributing gateways will make the inter gateway handover procedure happen more frequently. Hence it causes large cost of sigalling to the core network. 5. Conclusion When the gateways are distributed, the frequentness of gateway Liu, et al. Expires September 8, 2011 [Page 5] Internet-Draft DMM Signalling Analysis March 2011 relocation will increase. It relates to the specific model of distributed gateways. For the mobility management based on network, there is no extra signalling cost to radio acces network and a few effects on core network in the procedure of gateway relocation. In a word, the extra signalling cost can be ignored when the gateways are distributed. For the mobility management based on client, there is some cost on both radio and core network signalling when the procedure of gateway relocation is initiated due to the handling of some procedures,such as re-authentication and IP address allocation. however the signalling cost may be reduced by some new optimization mechanisms. 6. Security Considerations TBD 7. IANA Considerations None 8. Contributors The following people contributed to this document (in no specific order): YiFeng Bi ZTE bi.yifeng@zte.com.cn Wang Jing ZTE wang.jing17@zte.com.cn Tu Yangwei ZTE tu.yangwei@zte.com.cn 9. References 9.1. Normative References [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997. Liu, et al. Expires September 8, 2011 [Page 6] Internet-Draft DMM Signalling Analysis March 2011 9.2. Informative References [I-D.chan-netext-distributed-lma] Chan, H., Xia, F., Xiang, J., and H. Ahmed, "Distributed Local Mobility Anchors", draft-chan-netext-distributed-lma-03 (work in progress), March 2010. [I-D.ietf-mext-flow-binding] Tsirtsis, G., Soliman, H., Montavont, N., Giaretta, G., and K. Kuladinithi, "Flow Bindings in Mobile IPv6 and NEMO Basic Support", draft-ietf-mext-flow-binding-11 (work in progress), October 2010. [I-D.kassi-mobileip-dmi] Kassi-Lahlou, M., "Dynamic Mobile IP (DMI)", draft-kassi-mobileip-dmi-01 (work in progress), January 2003. [I-D.seite-netext-dma] Seite, P. and P. Bertin, "Dynamic Mobility Anchoring", draft-seite-netext-dma-00 (work in progress), May 2010. [RFC3775] Johnson, D., Perkins, C., and J. Arkko, "Mobility Support in IPv6", RFC 3775, June 2004. [RFC5213] Gundavelli, S., Leung, K., Devarapalli, V., Chowdhury, K., and B. Patil, "Proxy Mobile IPv6", RFC 5213, August 2008. [RFC5648] Wakikawa, R., Devarapalli, V., Tsirtsis, G., Ernst, T., and K. Nagami, "Multiple Care-of Addresses Registration", RFC 5648, October 2009. Authors' Addresses Dapeng Liu China Mobile Unit2, 28 Xuanwumenxi Ave,Xuanwu District Beijing 100053 China Email: liudapeng@chinamobile.com Liu, et al. Expires September 8, 2011 [Page 7] Internet-Draft DMM Signalling Analysis March 2011 Jun Song ZTE No.68,Zijinghua Road, Yuhuatai District Nanjing 210012 China Email: song.jun@zte.com.cn Wen Luo ZTE No.68,Zijinghua Road, Yuhuatai District Nanjing 210012 China Email: luo.wen@zte.com.cn Liu, et al. Expires September 8, 2011 [Page 8]