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 Handover Frequentness Analysis draft-liu-distributed-mobility-handover-analysis-00 Abstract This document analysis the handover frequentness 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 Handover Analysis March 2011 Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 2. Conventions used in this document . . . . . . . . . . . . . . 3 3. Inter-GW Handover Frequentness Analysis . . . . . . . . . . . 3 3.1. The Trend of the Inter-GW Handover Frequentness . . . . . 4 4. The impact of non-optimized Routing . . . . . . . . . . . . . 4 4.1. Analysis model . . . . . . . . . . . . . . . . . . . . . . 5 4.2. Traffic load Analysis . . . . . . . . . . . . . . . . . . 7 4.3. Congestion Probability Analysis . . . . . . . . . . . . . 8 4.4. Delay Analysis . . . . . . . . . . . . . . . . . . . . . . 8 5. Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . 9 6. Security Considerations . . . . . . . . . . . . . . . . . . . 10 7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 10 8. Contributors . . . . . . . . . . . . . . . . . . . . . . . . . 10 9. References . . . . . . . . . . . . . . . . . . . . . . . . . . 10 9.1. Normative References . . . . . . . . . . . . . . . . . . . 10 9.2. Informative References . . . . . . . . . . . . . . . . . . 10 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 11 Liu, et al. Expires September 8, 2011 [Page 2] Internet-Draft DMM Handover Analysis March 2011 1. Introduction With the Gateway in the cellular telecom core network moving downwards towards the access network and being deployed distributively, the number of gateways is increasing. Consequently, an increasing the percentage of handovers will be of inter-gateway handovers among all the handovers is also rising. Due to the fixed anchor point used by the current mobility management, the route in the access network is not optimized, ; that means there is roundabout in the access network. Such roundabout problems will aggravate with the increase of inter-gateway handovers. 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. Inter-GW Handover Frequentness Analysis We use a real deployment case in a metro of China as an example for the analysis. There are seventeen RNC nodes covering the metro. If we presume the Gateways are moved downwards to the level of RNC, we can calculate the frequentness of inter-GW handover based on that of inter-RNC handover. The frequentness of inter-RNC handover: In certain time period of j, relocNj is the total numbers of inter- RNC handover: I relocNj = SUM(CS relocation number i + PS relocation number i) i=1 In certain time period of j, rabNj is the total number of PDP activation and call establishment in RNCs: I rabNj = SUM(CS call number i + PS call number i) i=1 Rj is the frequentness of handover in this time period: Rj = relocNj / rabNj R is the mean handover frequentness in all the time periods: J R = (SUM Rj)/ J *100% j=1 Notes: 1) The CS calls and PS calls are counted based on the successful RAB establishment Liu, et al. Expires September 8, 2011 [Page 3] Internet-Draft DMM Handover Analysis March 2011 2) Both CS relocation and PS relocation include types of UE involved and UE not involved for handover out 3) I is the number of RNC in the metro 4) J is the number of time period, which could be one hour or more. The statistics shows that the mean frequentness of inter-RNC handover in one hour is 12.32%, that is there are 12 times inter-RNC handover per 100 times of CS calls or PS PDP activation. The highest handover frequentness could reach 15.97%. If the gateways are moved to the level of RNC, then the frequentness of inter-GW handover should be equivalent to that of inter-RNC. 3.1. The Trend of the Inter-GW Handover Frequentness The statistics result above is based on the current deployed network. With the evolution of the mobile network, e.g. when the LTE is deployed, we can expect that inter-GW handover frequentness will increase, when comparied with current deployed network. a. With the increment of the traffic and the user amount, the requirement of the bandwidth goes up consequently. To meet this requirement, the density of the basestation shall increase. Meanwhile, with the consideration of the limited capacity and capability of the GWs, the density of the GWs should also increase. So, in a same coverage area, there will be more GWs. As a result, the inter-GW handover frequentness will increase. b. With the service evolution, the rate of the always online user will increase. Accordingly, the rate of the service which is started (e.g. PDP activation) and completed (e.g. PDP inactivation) under a same GW will drop. As a result, the inter-GW handover frequentness will increase. We expect that in the near future, the value of the inter-GW handover frequentness may be doubled or even tripled to the value of current frequentness. 4. The impact of non-optimized Routing When fixed anchor point is used, the problems of roundabout will worsen with the movement of the user. Especially, when service is deployed far from the anchor point and near the location where the user is moving to. When the anchor point locates at a different city, the impacts of roundabout become more serious, that will inevitably affect the customer experience. In the following Liu, et al. Expires September 8, 2011 [Page 4] Internet-Draft DMM Handover Analysis March 2011 chapters, the impacts are appraised with a traffic model from the aspects of traffic volume, congestion and time delay, etc. 4.1. Analysis model We use the following model for the handover analysis. In this model, the anchor is distributed in the network edge. The communication peer may be located in the backbone or in the metro network. +----------------------+ | Backbone | |+-------+ +-------+ | +-----+ ||RouterB|-|RouterB|---|---| Peer| |+-------+ +-------+ | +-----+ +----------------------+ | | | | | | | +---------------+ /-------+ | +-----+ | +-------|------------|-------+ +-------|-------------|------+ | | | | | | | | | +-------+ +-------+ | | +-------+ +-------+ | | |RouterA|----|RouterA| | | |RouterA|------|RouterA| | | +-------+ +-------+ | | +-------+ +-------+ | | \ / | | \ / | | ,-'' -------+ | | ,-'' -------+ | | / \ | | / \ | | / Metro \ | | / Metro \ +-----+ | | | | | | |-----|Peer | | \ Network A ,' | | \ Network B ,' +-----+ | `. _, | | `. _, | | / `-..____,,' \ | | / `-..____,,' \ | | / \ | | / \ | | +------+ +------+ | | +------+ +------+ | | |P-GW1 | | P-GW2| | | | P-GW | | P-GW | | | |S-GW1 | | S-GW2| | | | S-GW | | S-GW | | | +------+ +------+ | | +------+ +------+ | | | | | +----------------------------+ +----------------------------+ Figure 1: Distributed anchor handover analysis model When the UE attaches to the network through S-GW2, the forwarding path is illustrated in the following figures. Liu, et al. Expires September 8, 2011 [Page 5] Internet-Draft DMM Handover Analysis March 2011 For the case that the communication peer is located in backbone, the forwarding path is illustrated as the following figure. +----+ +-----+ +------+ +-------+ +-----------------+ |UE |-->|P-GW2| | | | | | | | | |S-GW2|-->|Metro |-->|RouterA|-->|Metro to Backbone| +----+ +-----+ +------+ +-------+ +-----------------+ | +-------+ +-------+ | Peer |<--|RouterB| +-------+ +-------+ Figure 2: Forwarding path when peer is located in backbone network For the case that the peer is located in metro network, the forwarding path is illustrated as following figure. +----+ +-----+ +------+ +-------+ |UE |-->|S-GW2|-->|Metro |-->| Peer | | | |P-GW2| | | | | +----+ +-----+ +------+ +-------+ Figure 3: Forwarding path when peer is located in metro network Whe the UE moves to S-GW1's serving area and handover to S-GW1 from S-GW2, the data forwarding path is illustrated as the following figures. In this scenario, if we use current mobility solution, the anchoring point should be still at P-GW2. For the case that the peer is located in backbone network, the forwarding path is illustrated as following figure. +----+ +-----+ +------+ +-------+ +------ + | UE |-->|S-GW1|----->|Metro |----->| P-GW2 |------->|Metro | +----+ +-----+ +------+ +-------+ +-------+ | +----+ +-------+ +------------------+ +-------+ |Peer|<--|RouterB|<--| Metro to backbone|<--|RouterA| +----+ +-------+ +------------------+ +-------+ Liu, et al. Expires September 8, 2011 [Page 6] Internet-Draft DMM Handover Analysis March 2011 Figure 4: Forwarding path when peer is located in backbone network after handove For the case that the peer is located in metro network, the forwarding path is illustrated as following figure. +----+ +-----+ +------+ +------+ +------+ +----+ |UE |->|S-GW1|->|Metro |->| P-GW2|->|Metro |->|Peer| | | | | | | | | | | | | +----+ +-----+ +------+ +------+ +------+ +----+ Figure 5: Forwarding path when peer is located in metro network It is assumed that the traffic to the backbone network is 60% of the total traffic and the traffic to metro network is 40% of the total traffic. 4.2. Traffic load Analysis Based on the above handover model, the un-optimized routing is summaried in the following table. +------------------------------------------------------------------+ |Traffic | peer in Backbone | peer in Metro | average | |------------------------------------------------------------------| |Before | | | | |handover|1 volume within |1 volume within |1 volume within | | |metro. |metro. |metro. | | |1 volume between |0 volume between |0.6 volume between | | |metro and backbone|metro and backbone|metro and backbone | | |1 volume within |0 volume within |0.6 volume within | | |backbone |backbone |backbone | |------------------------------------------------------------------+ |After |2 volume within |2 volume within |2 volume within | |handover|Metro. |metro. |metro | | |1 volume between |0 volume between |0.6 volume between | | |metro and backbone|metro and backbone|metro and backbone | | |1 volume within |0 volume within |0.6 volume within | | |backbone |backbone |backbone | +------------------------------------------------------------------+ Liu, et al. Expires September 8, 2011 [Page 7] Internet-Draft DMM Handover Analysis March 2011 Figure 6: Traffic Analysis result for non-optimized routing From this analysis result, it can be concluded that the non-optimized routing will result in 100% traffic load increase in metro network. 4.3. Congestion Probability Analysis We assume that the congestion probability in metro network is X, the congestion probability between metro network and backbone is Y, based on the above analysis model, we have the following result. +-------------------------------------------------------------+ |congestion |peer in | | | |probability|backbone |peer in metro| average | |-------------------------------------------------------------| |Before | | |0.6*[1-(1-X)*(1-Y)]+0.4*| |handover |1-(1-X)* | X |X | | | (1-Y) | | | | | | | | |-----------+----------+-------------+------------------------+ |After | | |0.6*[1-(1-X)(1-X)*(1-Y)]| |handover |1-(1-X)* | | | | |(1-X)*(1-Y)|1-(1-X)(1-X)|+0.4*[1-(1-X)*(1-X)] | +-------------------------------------------------------------+ Figure 7: Congestion Probability Analysis result for non-optimized routing From the above result,we can conclude that the congestion probability will increase after handover. If X=3%, Y=3%, the congestion probability after handover will increase 2.86%. 4.4. Delay Analysis The delay from UE to peer consists of three parts:delay within metro network: T1, the delay between metro to backbone:T2, the delay within backbone:T3. Based on the above model, we have the following analysis result. Liu, et al. Expires September 8, 2011 [Page 8] Internet-Draft DMM Handover Analysis March 2011 +--------------------------------------------------------------+ | | | | | | Delay | Peer in Backbone| peer in Metro |Average | |--------------------------------------------------------------| |Before | | | | |handover | T1+T2+T3 | T1 |T1+0.6(T2+T3) | |--------------------------------------------------------------+ |After | | |2T1+0.6(T2+T3)| |handover | 2*T1+T2+T3 | 2*T1 | | +--------------------------------------------------------------+ Figure 8: Delay Analysis result for non-optimized routing From the analysis result, we can conclude that the delay within metro will increase 100% due to the non-optimized routing after handover. 5. Conclusion According to the inter-gateway handover frequentness calculation model and based on the data gathered from the deployed network, an average of 12% of service sessions perform inter-gateway handover (e.g. handover from S-GW2 to S-GW1) in every survey cycle. The inter-gateway handover leads to non-optimal routing and brings some impactions as following: Traffic load: referring to figure 6, a lot of wasted volume deliveres in the metro network. The operator's valuable bearer resource is wasted. According to the Global Mobile Data Traffic Forecast by CSISO, in 2015 the global mobile data traffic will be 6.3EB. That means the wasted volume will be 0.75EB in 2015. Congestion: Many mobile users will suffer from a higher congestion probability than the average. The increased congestion probability is X*(1-X)*(1-0.6X), in which the X is the average congestion probability in metro network and the Y is the average congestion probability between the metro network and backbone network. For example, when X is 10%, Y is 10%, then the average congestion probability is 15.4%. Then these mobile users have to bear the congestion probability of 23.86%. Delay: Many users will suffer from much more traffic delay. The increased traffic delay is one time of the average delay in the metro network. Liu, et al. Expires September 8, 2011 [Page 9] Internet-Draft DMM Handover Analysis March 2011 6. Security Considerations TBD 7. IANA Considerations None 8. Contributors The following people contributed to this document (in no specific order): Hong Jiang ZTE Jiang.Hong3@zte.com.cn ZhiHai Wang ZTE Wang.Zhihai@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. 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), Liu, et al. Expires September 8, 2011 [Page 10] Internet-Draft DMM Handover Analysis March 2011 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 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 11]