Internet Draft S. M. Shahrier Document: draft-shahrier-mobileip-mmp-00.txt InterDigital Expires: 2001 May 2001 A Low-Overhead Mobility Management Protocol in IP Layer Status of this Memo This document is an Internet-Draft and is in full conformance with all provisions of Section 10 of RFC2026. 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 obsolete 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. 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 RFC-2119 [1]. Abstract The Future Mobile Internet has to support many types of traffic flows, including both real-time and non real-time services. In addition, the network has to keep account of the location of each mobile node (MN) as it moves around the network. This draft proposes a novel protocol that combines mobility management with optimal routing for use over the mobile air interface. Its advantages is that it eliminates the need for IP-in- IP encapsulation from CN to MN, and still including the identity of the original CN in the IP datagram; eliminating any form of tunneling of packets to the MN by the CN, while the MN is away from its home. The elimination of these two overheads make it amenable for over the air interface communication in 3G Mobile IP networks. 1. Introduction The Mobile Internet of the future are expected to be capable of a high rate of data transmission. The traffic services Shahrier Standard Track - Expires July 2001 1 A Optimal Mobility Management Protocol May 2001 for 3G Wireless Internet supported include real-time such as video and voice and non real- time such as data. Each service will have different QoS require- ments, delay and throughput guarantees and bit-error rates (BER). In a mobile network, each mobile node (MN) is in communication with a single access point(AP). This situation represents a single point of attachment of the MN to the internet, This draft proposes a method of managing the mobility of a MN within multiple administrative domains. In the past, mobility management schemes within the IP-layer used a two-level hierarchical approach; Mobile IP [2] was generally used for managing mobility across different sub-networks; authors have proposed different solutions for managing micro-mobility within a single sub-network [3,4,5]. In this draft, we propose a scheme by which to manage the mobility of a MN across all administrative domains. The protocol also supports optimal routing using OSPF. 2. Improvements The new protocol proposes some improvements over existing mobility management protocols, in particular Mobile IP [1]. - It eliminates the need for Ip-in-IP encapsulation from CN to MN, and still including the identity of the original CN in the IP datagram. - Optimizes routing from sender to receiver, using OSPF, i.e. No need to tunnel via the HA as in Mobile IP. Although this protocol is proposed for both wireless and wireline networks, the elimination of these two overheads make it amenable for over the air interface communication in 3G Mobile IP networks. 3. Reference Architecture Fig. 1. depicts the architecture and topology of a typical mobile network. This architecture has been adapted from [2]. Associated with the diagram are terminology and definitions. Mobile Node (MN) An IP mobile terminal capable of changing its point of attachment to the internet. Access Point (AP) Access point offering a wireless air-interface connection to the MN. Access Router (AR) IP router connected to one or more AP's. Each AP represents a single IP address. Shahrier Standard Track - Expires July 2001 2 A Optimal Mobility Management Protocol May 2001 for 3G Wireless Internet Access Network Gateway (ANG) An IP gateway that connects the sub-networks to the internet backbone. A combination of ARs connected to the same ANG belong to the same sub-network. Conversely, ARs connected to different ANGÆs are part of different sub-networks. INTERNET BACKBONE | | --- --- --- | | | | | | | | | MN|-----| AP|-----------| AR|-- | --- --- --- | | | --- | --| | | --|ANG|-----| | --- | | | --- --- --- | | | | | | | |-- | | MN|+++++| AP|-----------| AR| | --- + --- --- | + | + | --- + | | |++ | | MN| | --- | | | | | --- --- --- --- | | | | | | | | | | | MN|+++++++| AP|----------| AR|-----|ANG|----| --- + --- --- --- | + | + | + | --- + | | |+++ | | MN| | --- | +++ air-interface connection. | --- wireline-link connection. | Fig. 1. Architecture of a Mobile IP Core Network. Shahrier Standard Track - Expires July 2001 3 A Optimal Mobility Management Protocol May 2001 for 3G Wireless Internet Each MN is pre-designated to a single sub-network called its ``home network''. Each home network is identified by an identifier called the home network identifier (HNI). Within its home network, the MN is connected to an access point called ``home APÆÆ, which in turn is connected to a router called ``home ARÆÆ. Every AR has a unique IP address, so that the link between a MN and its home AR represents a single connection point to the internet. Every MN in the network is assigned a fixed value called its host-name, and it does not change as the MN moves around the MCN. In particular, whenever any MN connected to the AR queries the DNS server with its pair, the DNS returns with the IP address of the home AR. Sending TCP/IP packets accomplishes the transmission of data packets from source to target. The DESTINATION IP ADDRESS in the IP header is used to route the packet to the target AR. The AR then broadcasts it to all the APÆs attached to it. The TCP ``destination port numberÆÆ field contains the host-name of the target MN. Each AP registers the host-names of the MNs that are currently attached to it. Thus, if it receives a packet whose port number (host-name) matches one of its registered host-names, then the packet is transmitted through the air-interface to that MN; otherwise the packet is silently discarded. 4. Protocol Description This section describes our proposed mobility management protocol for mobile nodes migrating around a mobile core network. This protocol is suitable for MNs moving within a single sub-network or across multiple sub-networks. The description of the protocol is as follows. Our protocol is fundamentally different from [2] in that instead of forwarding IP datagrams from one peer to another peer via a foreign agent (FA), the source is advised of the target's new location, everytime it moves to a new AR. If the mobile moves to a new AP, but it is still attached to the same BR, it means that the IP address of the attached BR has not changed. Conversely, if MH becomes attached to a different BR, the IP address had changed to indicate a new route. 4.1 Locating Target MN During the normal course of operation, mobile nodes may move throughout the mobile core network. Thus, to assist with locating the MN at any instant of time, each AR maintains a directory, called the ``Node Location Table'' (NLT). The NLT contains a listing of the node-names of all the MNs for which this AR is a home AR, and their current locations. If the MN is at its home AR, then the IP address is that of its home AR. However, if the mobile has moved away from its home AR, then the IP address is that of a foreign AR. Shahrier Standard Track - Expires July 2001 4 A Optimal Mobility Management Protocol May 2001 for 3G Wireless Internet --------------------------- | node-name-1 | ip-addr-1 | --------------------------- | node-name-2 | ip-addr-2 | --------------------------- | node-name-3 | ip-addr-3 | --------------------------- | àààààààà | àààààààà | --------------------------- Before IP datagrams can be sent to the target MN, a TCP connection has to be established between the AR of the corresponding node (CN) and the AR of the target. Before such an event, the source has to ascertain itself of the target mobile's current location. This can be accomplished by exchanging a pair of ICMP messages between the peers. 1. The CN indexes into the NLT using the node-name of the target, and retrieves its current ip-addr. This is the DESTINATION IP ADDRESS. 2. The CN constructs an ICMP node location query message, with the following field settings: TYPE = 20. Node location query. IDENTIFIER = node-name. Node-name of target MN. 3. The rest of the fields are filled in and the resulting ICMP message is placed in the DATA_AREA of the IP datagram frame. 4. In the IP header, SOURCE IP ADDRESS and DESTINATION IP ADDRESS are placed into their respective fields. 5. The resulting IP datagram is sent to the targetÆs home AR. 6. Target AR uses the node-name, indexes into the NLT, and retrieves MNÆs current IP address. 7. The AR constructs a new ICMP message and sends it back to the CN. This message is called a node query reply message. TYPE = 21. Node location query reply. OPTIONAL DATA = ip-addr. IP address of home/foreign AR. 8.The rest of the fields are filled in and the resulting ICMP message is placed in the DATA AREA of the IP datagram frame. 9.The SOURCE IP ADDRESS and DESTINATION IP ADDRESS fields are reversed, and placed into their respective fields. 10. The resulting IP datagram is sent to the CNÆs home AR. Shahrier Standard Track - Expires July 2001 5 A Optimal Mobility Management Protocol May 2001 for 3G Wireless Internet The message format of the ICMP header is as follows: 0 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |TYPE(20 or 21) | CODE | CHECKSUM | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | IDENTIFIER | SEQUENCE NUMBER | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | OPTIONAL DATA | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | | The exchange of control messages between the CN and the home BR, and the transmission of data from source to target are indicated in the following signaling diagram. SENDER RECEIVER | | | ICMP | |----------->| | | | ICMP | |<-----------| | | | IP | |----------->| | | | IP | |----------->| | | | IP | |----------->| | | The process initiated by the sender and receiver peers exchanging a pair of ICMP messages to determine the IP address of the AR associated with the MN. Once the IP address is known a TCP connection is established between the sender and receiver and the data transfer takes place. 4.2 Locating Target MN After Handoff Next, we consider what happens if a receiver MN handoffs to a new AP, while it is still communicating with the CN. The CN will have to be notified of the new location of the MN, so that it can still continue to receive data seamlessly. If, after the handover, the new AP is still connected to the same AR, i.e. the IP address hasnÆt changed; then the connection can continue to proceed as normal. If, on the other hand, the MN moves to a different AR, i.e. the IP address has changed; the CN will need to be notified Shahrier Standard Track - Expires July 2001 6 A Optimal Mobility Management Protocol May 2001 for 3G Wireless Internet of the new IP address. Thereafter, these aforementioned sources must re-direct their traffic flows. The MN sends the following UDP message back to the CN and the home BR. The home BR updates its HLR accordingly: 1. In the UDP header, the SOURCE PORT and the DESTINATION PORT fields are replaced by the host-name of the MN and the target respectively. 2. The new IP address is placed in the data section of the UDP header. The UDP MESSAGE LENGTH is set to 12 bytes because it is 3 words long. 3. The entire UDP packet is encapsulated into an IP datagram. The SOURCE IP ADDRESS and DESTINATION IP ADDRESS are placed into their respective fields in the IP header. These IP addresses are obtained from the DNS using the respective pairs. 4. The IP datagram is sent back to the target, either being the CN or the home BR. The format of the UDP packet is as follows: 0 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | SOURCE HOST-NAME | DESTINATION HOST-NAME | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | UDP MESSAGE LENGTH(12) | UDP CHECKSUM | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | TARGET IP ADDRESS | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | | 5. References [1] C. Perkins et. al.,öIP Mobility Supportö, FC 2002. [2] Design Team öProblem Statement: Reasons for Doing Context Transfers Between Mobile Nodes in IP Mobile Networksö, Internet-Draft. Author's Addresses Sharif M. Shahrier InterDigital 781 Third Ave. Phone: 1-610-337-4343 King of Prussia, PA. USA Email: sharif.shahrier@interdigital.com Shahrier Standard Track - Expires July 2001 7