支援同步換手之強化SCTP

Enhancing SCTP for Simultaneous Handover

何明勳(Ming-Syun He)

指導教授 ： 江為國

國立中正大學/工學院/資訊工程學系/碩士(2013年)

摘要

Stream Control Transmission Protocol (SCTP)為傳輸層(transport layer)的點對點(End-to-End)通訊協定，SCTP標準並沒有提供位置管理(Location Management)或換手管理(Handover Management)的功能，因此行動節點(Mobile Node；MN)與通訊節點(Corresponding Node；CN)使用SCTP傳輸資料過程中，如果進行雙邊移動，MN與CN之間的連線將會中斷。我們提出兩個方法，SCTP-BAU和SCTP-UFB，都是在SCTP標準中，新增Serving Node的原件，利用Serving Node來提供Handover Management的功能，Serving Node為分散在各個子網路(subnet)中，MN在不同子網路，就會連到不同的Serving Node，也就是說Serving Node為分散式設計。MN與CN建立SCTP連線過程(four-way handshake)中，會互相提供對方的Serving Node位址(IP Address)資訊，當MN換手(handover)到不同的子網路，就會更換新的Serving Node，在SCTP-BAU中，MN會傳送SCTP ASCONF binding update給CN和CN的Serving Node，同時，MN會透過新的Serving Node，傳遞MN新的IP Address給MN舊的Serving Node，如果CN與MN同時換手時，MN傳送SCTP ASCONF聯結更新(binding update)訊息到CN舊的IP Address會訊息遺失，同時MN也會傳送SCTP ASCONF binding update訊息給CN舊的Serving Node時，CN舊的Serving Node已經知道CN新的IP Address，CN舊的Serving Node會將訊息轉送到CN新的IP Address，CN收到MN的binding update訊息後，CN回傳ASCONF-ACK給MN，MN的流程與CN相同，MN與CN收到ASCONF-ACK訊息後，MN與CN的SCTP連線就會回復。我們提出分散式Serving Node的作法，改善集中式由同一顆server處理很多使用者與Handover Management的問題，以及我們利用Handover Delay來分析我們的方法，其結果確實比較低。

關鍵字

Stream Control Transmission Protocol ； Dynamic Address Reconfiguration ； Address Configuration Change Chunk ； 換手延遲 ； 同步換手 ； 傳輸層

並列摘要

The Stream Control Transmission Protocol (SCTP) is an end-to-end transport layer protocol. The SCTP standard does not provide location management and handover management with simultaneous mobility. In this article, we propose two handover management mechanisms to facilitate SCTP simultaneous handover, that is, SCTP handover management Binding And Update (SCTP-BAU) and SCTP handover management Update and Forward Binding (SCTP-UFB). We enhance the SCTP with Serving Node that provides handover management in subnets. When MN locates in different subnets, MN will change Serving Node, that is, Serving Node is distributed design. MN and CN provide their corresponding Serving Node IP Address when the SCTP four-way handshake to set up an association. In SCTP-BAU, when MN performs handover to different subnets, MN will send SCTP ASCONF binding update to CN and CN’s Serving Node in SCTP-BAU handover mechanism. Also, MN will send MN’s new IP Address to MN’s old Serving Node through MN’s new Serving Node. When both of the communicating MNs change their IP Address simultaneously, they lose their corresponding SCTP ASCONF binding updates. At the same time, both of MN and CN send SCTP ASCONF binding update to their corresponding Serving Node. The corresponding Serving Nodes will forward SCTP ASCONF binding update to their MNs’ new IP Address. MN will send SCTP ASCONF-ACK to CN when MN receives SCTP ASCONF binding update from CN. After MN and CN receive SCTP ASCONF-ACK, they will recover the previous SCTP association. We propose two distributed Serving Node handover mechanisms that enhance the centralized mechanism. Analytical results present that both of our schemes can shorten the total handover delay.

並列關鍵字

Handover Delay ； Simultaneous Handover ； Address Configuration Change Chunk ； Dynamic Address Reconfiguration ； Stream Control Transmission Protocol ； Transport Layer

參考文獻

[3] Stewart R., (2007), “Stream Control Transmission Protocol,” IETF Network Working Group, RFC 4960.

[4] Ong L., Yoakum J., (2002), “An introduction to the stream control transmission protocol (SCTP),” IETF Network Working Group, RFC 3286.

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