autoconf Working Group Jaehwoon Lee Internet-Draft Dongguk University Intended status: Informational Sanghynn Ahn Expires: August 27, 2010 University of Seoul Younghan Kim Soongsil University February 28, 2010 Address Autoconfiguration for MANET with Multiple MBRs draft-jaehwoon-autoconf-mmbr-02.txt Abstract In order to allow the subordinate MANET to be connected to the external network, the MANET border router (MBR) has been defined. For providing scalability and reliability to the subordinate MANET, multiple MBRs may be deployed. One of the issues on the subordinate MANET with multiple MBRs is which network prefixes are to be advertised by MBRs. In the case when MBRs advertise different network prefixes, if a MANET node changes its default MBR to a new one, the node may have to transmit packets via non-optimal paths to keep using the existing connection to the previous MBR, or change its address by using the network prefix information from the new MBR. In the former case, the MANET node may not communicate with the MBR due to MANET partitioning. In the latter case, on-going sessions can be terminated because of the address change. In this draft, we define a PMIPv6 based address autoconfiguration mechanism that enables MANET nodes to operate properly when all MBRs advertise the same network prefix in the subordinate MANET. Status of this Memo This Internet-Draft is submitted to IETF in full conformance with the provisions of BCP 78 and BCP 79. 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. Jaehwoon Lee, et al. Expires Aug. 27, 2010 [Page 1] Internet-Draft Address Autoconfiguration for multiple MBRs Feb. 28, 2010 The list of Internet-Draft Shadow Directories can be accessed at http://www.ietf.org/shadow.html. This Internet-Draft will expire on August 27, 2010. Copyright Notice Copyright (c) 2010 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 BSD License. Table of Contents 1. Introduction..................................................3 2. Terminology...................................................4 3. Message format................................................4 3.1 Registration Request message..............................4 3.2 Registration Confirmation message.........................4 4. Protocol operation............................................4 5. Security Considerations.......................................7 6. IANA Considerations...........................................7 References.......................................................7 Author's Addresses...............................................8 Jaehwoon Lee, et al. Expires Aug. 27, 2010 [Page 2] Internet-Draft Address Autoconfiguration for multiple MBRs Feb. 28, 2010 1. Introduction The mobile ad hoc network (MANET) enables mobile nodes to communicate via multiple wireless hops without the need of any wired infrastructure. In a MANET, two nodes not within transmission range have to deliver data to each other through other intermediate nodes. For forwarding packets destined to other nodes, each node must have the routing capability, i.e., the mechanism for establishing data delivery routes between any pair of source and destination nodes. The IETF MANET working group has defined route setup mechanisms for delivering data between MANET nodes. Especially for an ad hoc network such as the MANET, the mechanism that can allow nodes to configure their addresses autonomically is more desirable than the static address configuration mechanism since the former has less configuration and management overhead due to its omission of manual intervention. MANETs can be classified into the subordinate MANET or the autonomous MANET depending on whether it is connected to the external network or not [1]. The MANET border router (MBR) which is a gateway device connecting the MANET with the external network has been defined for the subordinate MANET. As the number of nodes in the MANET increases, the amount of traffic between the MANET and the Internet increases, so the MBR gets overloaded, resulting in the overall network performance degradation. To overcome this problem, multiple MBRs can be used for the Internet connectivity [2]. Mechanisms in which each MBR advertises a different network prefix have been proposed for the MANET with multiple MBRs [3-4]. However, in these mechanisms, if a node moves to another place, it sends packets via non-optimal paths to maintain its connection to the previous MBR, or it changes its address by using the network prefix delivered from the new MBR. An on-going session may get terminated because of MANET partitioning in the formal case or the address change in the latter case. In this draft, we define an address autoconfiguration mechanism for the subordinate MANET with multiple MBRs which advertise the same network prefix. In the proposed mechanism, since all MBRs advertise the same network prefix, even a node moves it can still use its preconfigured address. That means that no address reconfiguration is needed in case of node movement, so the proposed mechanism has the advantage of keeping on maintaining its existing session(s). Furthermore, under node movement, a node can still find an optimized path without changing its address because it can choose the MBR that can be reached via the minimum number of hops. Jaehwoon Lee, et al. Expires Aug. 27, 2010 [Page 3] Internet-Draft Address Autoconfiguration for multiple MBRs Feb. 28, 2010 2. Terminology TBD. 3. Message Format 3.1 Registration Request (RR) Message TBD 3.2 Registration Confirmation (RC) Message TBD 4. Protocol Operation MN MBR1(MAG1) MBR2(MAG2) LMA (Internet) CN | | | | | |<----------| | | | ICMP SERA message | | | (Configure IPv6 address to MANET interface) | | |<--------->| | | | (DHCP with prefix delegation) | | | |---------->| | | | |RR message | | | | | |---------------------------------->| | | | PBU message (Create Binding Cache Entry) | | |<----------------------------------| | | | PBAck message | | |<----------| | | | |RC message | | | | |<--------->|<=================================>|<------------>| | Data packet transfer between MN and CN via MBR1 and LMA | (MN changes its default gateway from MBR1 to MBR2) | | |<---------------------------| | | | ICMP SERA message | | | |--------------------------->| | | | RR message | | | | | |----------------->| | | | | PBU message | | | | | (Update Binding Cache Entry | | | |<-----------------| | | | | PBAck message | | |<---------------------------| | | | RC message | | | |<-------------------------->|<================>|<------------>| | Data packet transfer between MN and CN via MBR2 and LMA | | | | | | Figure 1: Message exchange scenario Jaehwoon Lee, et al. Expires Aug. 27, 2010 [Page 4] Internet-Draft Address Autoconfiguration for multiple MBRs Feb. 28, 2010 The message exchange scenario considered in this draft is depicted in figure 1. The network is composed of the external network such as the global Internet, a PMIPv6 domain and a MANET. The operation of the PMIPv6 protocol is defined in [5]. In the PMIPv6 domain, a local mobility anchor (LMA) is located and acts as a kind of home agent (HA). The MANET can be connected to the PMIPv6 domain through a multiple number of mobility access gateways (MBRs) and an MBR operates as a mobility access gateway (MAG) in the PMIPv6 domain. One network prefix is assigned to the MANET, and each MBR periodically advertises scope-extended Router Advertisement (SERA) messages to the entire MANET [6]. The SERA message is defined to resolve the duplicate packet reception problem which can occur in a multi-hop wireless network such as the MANET. The network prefix assigned to the MANET and the address of the MBR originating the SERA message are included in the message. Even though the different MBR address information is included in the SERA message sent by different MBR, the network prefix that can be delived by subnet masking the MBR address with the prefix length is the same. In other words, the MBRs connecting the MANET and the global Internet advertise the same network prefix. When a MANET node (MN) connects to the MANET for the first time, it waits for a SERA message from a MBR. Assume that the SERA message from MBR1 arrives at the MN first. Then the MN configures the IPv6 address of its MANET interface by utilizing the stateless address autoconfiguration mechanism based on its MAC address and the network prefix obtained from the MBR1 address and the network prefix length [7]. After that, the MN sets the MBR1 address in the SERA message as the address of its default gateway, and stores the distance to MBR1 which can be calculated with '255 - the Cur Hop Limit in the scope-extended RA message + 1' in its routing table. In addition to that, the MN sets the value in the source IP address field of the IP packet having the received SERA message as the next-hop address to its default gateway and records this information in its routing table. Then, the MN decreases the Cur Hop Limit value in the received SERA message by 1 and broadcasts the modified SERA message. Also, the MN sends a Registration Request (RR) message to MBR1. Upon receiving the RR message, MBR1 sends a Proxy Binding Update (PBU) message with the MN address to the LMA. The LMA stores the binding information for the MN and MBR1 and sends a Proxy Binding Acknowledgement (PBAck) message to MBR1. After that, a tunnel between the LMA and MBR1 is established for the MN. After receiving the PBAck message from the LMA, MBR1 sends a Registration Confirmation (RC) message to the MN. Now, MBR1 becomes the default gateway for the node and the MN can communicate with any host in the global Internet. The MN uses the IP-in-IP encapsulation or routing header in order for the traffic sent from the MN to be delivered to the default gateway of the node. Jaehwoon Lee, et al. Expires Aug. 27, 2010 [Page 5] Internet-Draft Address Autoconfiguration for multiple MBRs Feb. 28, 2010 If MBR1 receives a packet from the MN, it transmits the packet to the LMA via the established tunnel which, in turn, forwards it to the destination host in the global Internet. Since SERA messages are periodically advertised by each MBR, a node can receive multiple SERA messages advertised by other MBRs even after it has configured an IPv6 address of is interface. The operation of a MN receiving a SERA message is as follow. Once a MN receives a SERA message broadcasted by the neighbor node which is set as the next-hop node to its default gateway, the MN updates its corresponding routing table entry using the information in the received SERA message. That is, the MN determines the distance to its default gateway based on the Cur Hop Limit value in the SERA message. If the MBR address (i.e., MBR2) in the SERA message is different from its current default gateway, the MN sends a RR message to MBR2 and broadcasts the SERA message throught the MANET. If the MN receives a RC message from MBR2, it updates its routing table entry related to the default gateway information. If the MN receives a SERA message from another neighbor node which is not the next-hop node to the default gateway, the MN compares the distance to the MBR having sent the SERA message (which can be computed from the CUR Hop Limit valued in the SERA message) and that to its default gateway. If the fomer one is larger than or equal to the latter, it discards the received SERA message. Otherwise, after broadcasting the SERA message, it updates its corresponding routing table entry based on the information in the received SERA mesage as follows. At first, the MN checks the MBR address in the SERA message. If the MBR address in the SERA message is the same as its current default gateway, the MN changes the distance to the default gateway to the distance value obtained from the SERA message and sets the node sending the SERA message as the next-hop node to the default gateway. If the MBR address (i.e., MBR2) in the SERA message is different from the address of its default gateway, the MN sends a RR message to MBR2. If the MN receives a RC message for MBR2, it updates its routing table entry related to the default gateway information. In this case, even when the default gateway is changed, the network prefix for the MANET is kept the same, so the MN can keep on maintaining its on-going session(s) because it can still use its IPv6 address configured on its MANET interface. Furthermore, even if the MN changes its default gateway, the IPv6 address configured on its MANET interface is kept the same. Thus, if the packets from a host in the Internet arrive at the MBR chosen as its previous default gateway before the registration process is completed, they can be delivered to the MN via the previous default gateway, so no packet loss due to address changes will happen. Jaehwoon Lee, et al. Expires Aug. 27, 2010 [Page 6] Internet-Draft Address Autoconfiguration for multiple MBRs Feb. 28, 2010 If the MN does not receive a SERA message from its next-hop node to the default gateway for some time duration or it determines that the next-hop node is no more its neighbor node, the MN deletes the default gateway related entry from its routing table. 5. Security Consideration TBD. 6. IANA Considerations TBD. References [1] E. Baccelli et al., "Address Autoconfiguration for MANET: Terminology and Problem Statement", draft-ietf-autoconf- statement-04, Work in progress, Feb. 2008. [2] S. Ruffino, P. Stupar and T. Clausen, "Autoconfiguration in a MANET: connectivity scenarios and technical issues", draft- ruffino-manet-autoconf-scenarios-00, work in progress, Oct. 2004. [3] S. Ruffino and P. Stupar, "Automatic configuration of IPv6 addresses for MANET with multiple gateways (AMG)", draft-ruffino-manet-autoconf-multigw-03, work in progress, June 2006. [4] C. Jelger, T. Noel and A. Frey, "Gateway and address autoconfiguration for IPv6 adhoc networks", draft-jelger-manet- gateway-autoconf-v6-02, work in progress, apr. 2004. [5] S. Gundavelli, K. Leung, V. Devarapalli, K. Chowdhury and B. Patil, "Proxy Mobile IPv6", RFC 5213, Aug. 2008. [6] J. H. Lee, S. Ahn, Y. Kim, Y. Kim and S. Kim, "Scope-Extended Router Advertisement for Connected MANETs", draft-jaehwoon- autoconf-sera-00, Work in progress, July 2008. [7] S. Thomson and T. Narten, "IPv6 Stateless Address A utoconfiguration", RFC 2462, Dec. 1998. Jaehwoon Lee, et al. Expires Aug. 27, 2010 [Page 7] Internet-Draft Address Autoconfiguration for multiple MBRs Feb. 28, 2010 Author's Addresses Jaehwoon Lee Dongguk University 26, 3-ga Pil-dong, Chung-gu Seoul 100-715, KOREA Email: jaehwoon@dongguk.edu Sanghyun Ahn University of Seoul 90, Cheonnong-dong, Tongdaemun-gu Seoul 130-743, KOREA Email: ahn@uos.ac.kr Younghan Kim Soongsil University 11F Hyungnam Engineering Bldg. 317, Sangdo-Dong, Dongjak-Gu, Seoul 156-743 Korea E-main: yhkim@dcn.ssu.ac.kr Jaehwoon Lee, et al. Expires Aug. 27, 2010 [Page 8]