Internet Engineering Task Fore Mohammed Kassi-Lahlou INTERNET DRAFT France Telecom R&D January, 2001 Christian Jacquenet France Telecom R&D Dynamic Mobile IP (DMI) Status of this Memo This document is an Internet-Draft and is in full conformance with all provisions of Section 10 of RFC 2026. 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. Abstract This draft introduces a different mode for the mobility usage in IP networks. This mode does not modify the Mobile IP protocol specifications [2] but makes their use more dynamic according to the movements of the mobile node as far as its communications are concerned. The Mobile IP mechanisms will be used only for the ongoing communications while the mobile node is in motion. That is, the Mobile IP mechanisms will be used for the communications established from an IP sub-network and which continue when the mobile node moves to another IP sub-network. For all the communications that are opened and closed in the same IP sub-network there is no need to use Mobile IP mechanisms even if the mobile node is away from its home network. Kassi-Lahlou, Jacquenet [Page 1] INTERNET DRAFT January, 2001 Table of Contents 1. Introduction 3 2. Motivation 4 3. Terminology 5 4. Overview 5 5. Operation 6 5.1. Initial phase 6 5.2. Connection phase 6 5.3. Mobility phase 7 5.4. Input connections 8 6. Scalability Considerations 9 7. Security Considerations 11 8. References 11 Acknowledgements 11 Addresses 12 Kassi-Lahlou, Jacquenet [Page 2] INTERNET DRAFT January, 2001 1. Introduction This draft aims at defining a different mode for the mobility usage in IP networks. This mode does not modify the Mobile IP protocol specifications [2] but makes their use more dynamic according to the movements of the mobile node as far as its communications are concerned. Indeed, the purpose of this draft is to address the following issues: (1) When a mobile node is on a visited network, is it necessary to use the Mobile IP mechanisms to open a communication with a new correspondent node (CN)? (2) When a new correspondent node opens a communication with a mobile node which is outside its home network is it necessary to use the Mobile IP mechanisms? In case (1) it is certainly more effective to open the communication with the new correspondent node directly by using the Care-of-Address as a source address and classical IPv6 forwarding and routing mechanisms without using the Mobile IP mechanisms, thus avoiding exchanges of Binding Update/Binding Acknowledgement messages, and with no use of the Home Address and Routing Header options for exchanging data. In case (2) it is certainly more effective to indicate to the new correspondent node the Care-of-Address of the mobile node so that it can open the communication directly with this address using classical IPv6 forwarding and routing mechanisms without using the Mobile IP mechanisms, thus avoiding exchanges of Binding Update/Binding Acknowledgement messages, and with no use of the Home Address and Routing Header options for exchanging data. The Mobile IP mechanisms will be used only for the ongoing communications while the mobile node is in motion between different IP sub-networks. That is, the Mobile IP mechanisms will be used for the communications established from an IP sub-network and which continue when the mobile node moves to another IP sub-network. For all the communications that are opened and closed in the same IP sub-network there is no need to use Mobile IP mechanisms even if the mobile node is away from home. Within this specific context, it is expected that this proposal makes theconnection establishment time better, while the volume of control messages should be dramatically reduced, . This draft deals especially with Mobile IPv6 but the mode specified here is also applicable in the case of Mobile IPv4 [3]. Kassi-Lahlou, Jacquenet [Page 3] INTERNET DRAFT January, 2001 2. Motivation Within the context of a wide deployment of IP mobility services (telephony, videoconferencing, interactivity...) it is assumed that the majority of the communications will take place without mobility at the IP level (Fig. 1) i.e. without changing the IP sub-network when moving. It is also very likely that the majority of the communications open and close while the mobile node keeps being connected to the same IP sub-network. It does not mean that the mobile node does not move during its communications. The mobile node can move inside a zone of radio cells without connecting/re-connecting to different IP sub-networks and therefore, without changing the IP address. In such cases the mobile node does not need to use the Mobile IP mechanisms. The Mobile IP mechanisms will be used only for the communications established from an IP sub-network and which will be kept opened while the mobile node moves to another IP sub-network. This mobility management mode reduces the connection establishment times and in many cases it reduces the number of control messages exchanged between the mobile node and its correspondent nodes. The Mobile IP mechanisms will be used only when they are necessary to maintain the communications opened between the mobile node and its correspondents while it moves between various IP sub-networks. ____________________________________________ / \ / \ / IP network \ \ / \ / \____________________________________________/ / \ / \ / \ _______/_________ _______\_________ / \ / \ / radio sub-network \ / radio sub-network \ \ / \ / \_________________/ \_________________/ <--------------------> movement at the radio link level <----------------------------> movement at the IP level - Fig. 1: mode of operation - Kassi-Lahlou, Jacquenet [Page 4] INTERNET DRAFT January, 2001 3. Terminology This document frequently uses the following terms in addition to those defined in the draft "Mobility support in IPv6" [2]: Permanent home sub-network: home link in the Mobile IP terminology. This is the IP sub-network on which a mobile node's permanent home address is defined. Permanent home address: home address in the Mobile IP terminology. This is the IP address that allows each correspondent node to contact the mobile node without having to know its current location. Permanent home agent: home agent in the Mobile IP terminology. This is the mobility agent on the permanent home sub-network. It acts as a home agent for the communications opened from the permanent home sub-network and which continue when the mobile node moves to another IP sub-network. Temporary home sub-network: a foreign link (in the Mobile IP terminology) from which a mobile node has opened a communication with an additional correspondent node. Temporary home address: a Care-of-Address (in the Mobile IP terminology) that is associated to a mobile on the temporary home sub-network. The mobile node uses this address as its source address to directly open a connection with an additional correspondent node without using Mobile IP mechanisms. Temporary home agent: a mobility agent on the foreign link from which the mobile node has opened connections with additional correspondent nodes. Temporary home agent acts as a home agent for these connections, until they close, when the mobile node moves to another IP sub-network. In this document, the key words "MAY", "MUST, "MUST NOT", "optional", "recommended", "SHOULD", and "SHOULD NOT", are to be interpreted as described in [1]. 4. Overview When a mobile node is connected to a given IP sub-network it establishes connections with additional correspondent nodes by using the IP address obtained in the IP sub-network to which it is attached. Two situations can occur: Kassi-Lahlou, Jacquenet [Page 5] INTERNET DRAFT January, 2001 - The communication ends while the mobile node is still connected to the same IP sub-network. In this case it does not have to use the Mobile IP mechanisms. - The communication continues while the mobile node moves and changes from the IP sub-network to another. In this case, to maintain the communication opened, it has to use the Mobile IP mechanisms. 5. Operation 5.1. Initial phase In this initial phase, the mobile node is connected to the permanent home sub-network, gets its permanent home address and the address of its permanent home agent. Note that the mobile node can just be configured with all the above-mentioned parameters without being connected to its permanent home sub-network. 5.2. Connection phase When the mobile node connects to a physical sub-network (wired or wireless), it can be on its permanent home sub-network or on a temporary home sub-network. 5.2.1. Connecting to the permanent sub-home network In this case the mobile node discovers that it is connected to its permanent home sub-network and it discovers its permanent home agent. As long as it remains connected to its permanent home sub-network and for all the communications that have been opened with additional correspondent nodes, it uses classical IPv6 forwarding and routing mechanisms without using the Mobile IP mechanisms. 5.2.2 Connecting to a temporary home sub-network In this case the mobile node discovers that it is connected to a foreign sub-network and it discovers a mobility agent on this sub-network. The MN gets a Care-of-Address and sends a "Binding Update" message to its permanent home agent. To send Binding Update messages, it uses Mobile IP mechanisms. Kassi-Lahlou, Jacquenet [Page 6] INTERNET DRAFT January, 2001 As long as the MN remains connected to this foreign sub-network, it opens all the IP communications with additional correspondent nodes by using the Care-of-Address as its source address, and it uses classical IP forwarding and routing mechanisms without using the Mobile IP mechanisms. In this case, the foreign sub-network, the mobility agent on this sub-network and the Care-of- Address are respectively called temporary home sub-network, temporary home agent and temporary home address. In both previous cases (5.2.1, 5.2.2), the mobile node opens all the connections with additional correspondent nodes by using the address obtained in the sub-network it is attached to as the source address. For a given communication, two situations can occur: a) The communication ends while the mobile node remains connected to the same IP sub-network, then it does not need to use the Mobile IP mechanisms. b) The communication continues while the mobile node gets connected to a different IP sub-network, then it becomes necessary to use the Mobile IP mechanisms. 5.3. Mobility phase When a mobile node moves from a sub-network (home or foreign) towards another sub-network (home or foreign): 1) It discovers its movement and the change of the IP sub-network, 2) It discovers a home agent (new, permanent or the still active previous temporary one) of the IP sub-network it has just connected to, 3) It gets an address (new, permanent or the still active previous temporary one) with the prefix of the IP sub-network it has just connected to, 4) It exchanges Binding Update/Binding Acknowledgement messages with its permanent home agent. A) For a correspondent node with whom an ongoing communication has been established before the arrival on this IP sub-network, a mobile node uses Mobile IP mechanisms to maintain this communication opened. The use of Mobile IP consists among others in: Kassi-Lahlou, Jacquenet [Page 7] INTERNET DRAFT January, 2001 a) Exchanging Binding Update/Binding Acknowledgement messages with the temporary home agent of the IP sub-network from which this communication was opened (if it is different from the permanent home agent), b) Exchanging Binding Update/Binding Acknowledgement messages with a home agent on the link where the previous care-of-address is located so as to forward packets from the previous care-of address, in the case where the above-mentioned home agent it is different from the permanent home agent and the above temporary one, c) Exchanging Binding Update/Binding Acknowledgement messages with the correspondent node himself d) Using the Home Address and Routing Header options to exchange packets with this correspondent B) For the communications with new correspondents, a mobile node does not use the Mobile IP mechanisms: a) It establishes a communication with them by using the classical IP forwarding and routing mechanisms instead, b) It uses the address acquired in the IP sub-network it is attached to, as the source address. 5.4. Input connections When a correspondent node that has no information about the location of a mobile node opens a communication with this MN, it uses the permanent home address of the mobile node as the destination address. Therefore, packets are forwarded towards the permanent home network of the mobile node. Two cases can be considered: - The mobile node is indeed connected to its permanent home network: in this case, packets are directly forwarded towards the mobile node which in turn answers directly to the correspondent node. Obviously, the communication does not make use of Mobile IP mechanisms, but uses classical IP forwarding and routing mechanisms instead. - The mobile node is connected to a temporary home network: in this case packets are intercepted by the permanent home agent and tunnelled towards the mobile node location. When the mobile node receives such packets it sends Binding Update messages to the correspondent node so as to establish a direct communication with the CN, thanks to the use of the Mobile IP mechanisms. Kassi-Lahlou, Jacquenet [Page 8] INTERNET DRAFT January, 2001 For the second case, where the mobile node is connected to a temporary home sub-network, another way of managing these input calls can be proposed: - Upon reception of the first packet, the mobile node sends a message to the correspondent node to notify that it refuses the communication by using its permanent home address, and asks the correspondent node to communicate directly by using its temporary home address as the destination address, so as to avoid the use of the Mobile IP mechanisms. This notification is processed by the upper layers. The notification message is not directly sent to the correspondent node so as to avoid the use of Binding Update messages. The message is tunnelled back to the permanent home agent which transmits the tunnelled packet to the correspondent node. Furthermore, this procedure allows the mobile node to negotiate with the correspondent node a new security association which will be indexed on the temporary home address. 6. Scalability Considerations One identified issue when using this mechanism is that the mobile node should maintain information concerning the temporary home agent of the network from which an ongoing communication was established. We assume that this additional information does not dramatically increase the amount of information being maintained by the mobile node concerning its communications. Indeed, for every correspondent node with whom a communication is in progress while the mobile node is moving, an entry is maintained by the MN in its mobility cache. On the other hand, the number of entries in the mobility cache will decrease because only those correspondent nodes with whom the communications will be kept opened while the mobile node is moving between various IP sub-networks, have one entry in this cache. For example, when a mobile node leaves its permanent home network and connects to a temporary network, and it has established no communication before it connects to the temporary network. It opens a communication with a new correspondent node, and this communication ends before the mobile node connects to another point of attachment in the IP sub-network. For this communication: If the mobile node uses the Mobile IP mechanisms it implies: Kassi-Lahlou, Jacquenet [Page 9] INTERNET DRAFT January, 2001 - The creation of an entry in the mobile node mobility cache as well as in the correspondent node mobility cache, - The exchange of Binding Update/Binding Acknowledgement messages and - The use of the Home Address and Routing Header options for the exchanges of packets. If the mobile node has established the communication without using Mobile IP mechanisms and by using its temporary home address as source address, the procedures are dramatically simplified. Example: For the mobile services being deployed over large wireless networks, the interest of this mobility management facility is going to depend: - On the range of the wireless areas that actually correspond to an IP sub-network - On the duration of the communication when the mobile node is in motion ____________________________________________ / \ / \ / IP network \ \ / \ / \____________________________________________/ / \ / \ IP sub-network (1) / \ IP sub-network (2) _______/_________ _______\_________ / \ / \ / wireless area (1) \ / wireless area (2) \ \ / \ / \_________________/ \_________________/ <-------------------> no IP mobility <----------------------------> IP mobility - Fig. 2: using the mobility management facility within a large wireless network. - Kassi-Lahlou, Jacquenet [Page 10] INTERNET DRAFT January, 2001 This mode consists in using the Mobile IP mechanisms only for the communications which continue after a change of the point of attachment in the IP network, and it is more efficient for the IP mobility management in the case of large networks, especially when the number of the communications that comprise a change of the point of attachment in the IP network remains relatively low, compared to the global number of communications which are opened and closed inside a single IP sub-network. 7. Security Considerations This mode does not introduce any additional security issue compared to the current Mobile IP specifications. When the mobile node uses Mobile IP mechanisms, the security requirements are the same as for mobile IP specifications and when it does not use these mechanisms the security requirements are the same as for classical IP forwarding and routing specifications. 8. References [1] S. Bradner, "Key words for use in RFCs to Indicate Requirement Levels", Request for Comments (Best Current Practice) 2119, Internet Engineering Task Force, March 1997. [2] David B. Johnson, Charles Perkins, "Mobility Support in IPv6", draft- ietf-mobileip-ipv6-13.txt, Work in Progress, November 2000. [3] C. Perkins, "IP Mobility Support for IPv4", draft-ietf- mobileip-rfc2002-bis-03.txt, Work in Progress September 2000. Kassi-Lahlou, Jacquenet [Page 11] INTERNET DRAFT January, 2001 Addresses Mohammed Kassi-Lahlou France Telecom R&D 42, rue des Coutures 14066 Caen France Phone: 33 2 31 75 94 03 Fax: 33 2 31 73 56 26 E-mail: mohamed.kassilahlou@francetelecom.com Christian Jacquenet France Telecom R&D 42, rue des Coutures 14066 Caen France Phone: 33 2 31 75 94 28 Fax: 33 2 31 73 56 26 E-mail: christian.jacquenet@francetelecom.com Copyright (c) The Internet Society (2000). 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, or as required to translate it into languages other than English. The limited permissions granted above are perpetual and will not be revoked by the Internet Society or its successors or assigns. This document and the information contained herein is provided on an "AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE. Kassi-Lahlou, Jacquenet [Page 12]