Internet Draft Jun Kyun Choi Document: draft-choi-mobileip-ldpext-01.txt ICU Yoo Kyoung Lee ETRI Sun Hee Yang ETRI Tai Won Um ICU Myoung Hun Kim ICU February 2001 Extension of LDP for Mobile IP Service through the MPLS Network Status of this Memo This document is an Internet-Draft and is in full conformance with all provisions of Section 10 of RFC2026 [1]. 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 document discusses how to build the large-scale Mobile IP network through the MPLS network. One small-scale Mobile IP network could be connected to other networks through the MPLS backbone network. It proposes the MPLS network architecture to provide the large-scale Mobile IP network. Specifically, it proposes that the label distribution protocol (LDP) can be applied to set up the Label switched path (LSP) tunnels between the mobile agents (that is, Foreign Agents and Home Agents)[3]. It means that the IP-in-IP tunnels can be replaced by one or multiple Label Switched Paths (LSPs) on the MPLS network. Conventions Choi et al. Expires October 2001 [Page 1] Internet Draft Draft-choi-mobileip-ldpext-01.txt October 2001 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 [2]. Table of Contents 1. Introduction 2. The MPLS Network Architecture with Mobility Support 2.1. Assumptions and Requirements 2.2. Network Architecture and Service Scenarios 2.3. Routing considerations 2.4. Interworking of existing Mobile IP network 3. Description of the Protocol 3.1. General Assumptions 3.2. LSP Tunnels for Mobility Support 3.3. Agent Advertisement and Solicitation 3.4. Registration and LSP setup for Mobile Node 3.5. Handoff and LSP re-routing 4. Required Messages and TLVs 4.1 Required Messages and TLVs 5. IANA Considerations 6. Security Considerations 7. References 8. Author's Addresses 9. Full Copyright Statement Choi, et al. Expires October 2001 [Page 2] Internet Draft Draft-choi-mobileip-ldpext-01.txt October 2001 1. Introduction A mobile node of a Mobile IP network may be connected to Foreign Mobile IP networks with a distance. The MPLS network can provide the backbone solution for high speed IP forwarding. The relevant label switched paths on the MPLS network can support proper Quality-Of- Service (QoS) paths for differentiated Mobile IP services. This document proposes the Multiprotocol Label Switching (MPLS) network architecture and tunneling procedures to support the Mobile IP network. Similar concerns on the integration of MPLS network and Mobile IP network are also investigated in [8]. The MPLS backbone network can build the large-scale Mobile IP network. A Mobile IP network is connected to other Mobile IP network via the Label Edge Router (LER). To support Mobile IP services, The MPLS network have to accommodate Foreign Agent and Home Agent. The LER is capable of forwarding Mobile IP packets by encapsulating with relevant label header. The LER would be a Foreign Agent or its corresponding node. For mobility support, the LER will be a gateway router for the corresponding Mobile IP network. To support the hierarchical architecture, the Gateway foreign agent or Regional foreign agent could be defined on the MPLS network [4]. For the control procedure, the label distribution protocol (LDP) may be extended to set up the Label switched path (LSP) tunnel between the mobile agents (that is, foreign agents and home agents) through the MPLS network [3]. The IP-in-IP tunnels of Mobile IP Network can be provided by the one or multiple LSPs through the MPLS network. When a mobile node is moving to the foreign area, the existing LSPs may be extended without service interrupt. The short-cut LSPs between source and destination mobile nodes may be recalculated to avoid the long cascaded connections. The MPLS protocol can be applied on the Mobile IP network according to geographical area and routing path to forward packets from home agent to foreign agent. There may be three types of scenarios according to the functionality of Mobile IP protocol in the MPLS- based network. Scenario 1 applies basic Mobile IP protocol [5] to MPLS-based network. This scheme uses natural extension of the existing Mobile IP protocol through the MPLS network. Scenario 2 applies Mobile IP Route Optimization protocol [12] to MPLS-based network. In this scheme, an ingress LER must intercept the incoming IP packets to forward the destination foreign agent through the established LSP. Scenario 3 applies hierarchical Mobile IP protocol [4] to MPLS-based network. This scheme performs regional registration locally and LSP re-routing method in a visited domain. In the above schemes, The MPLS network provides the LSP tunnels replaced by the IP-in-IP tunnels. Scenario 1 (MPLS-based Mobile IP) is based on the existing scenario of Mobile IP service and the home agent and foreign agent should be located at the LER [5],[6]. In this scenario, the IP-in-IP tunnels Choi, et al. Expires October 2001 [Page 3] Internet Draft Draft-choi-mobileip-ldpext-01.txt October 2001 between home agent and foreign agent could be done with help of the LDP operation. There are no additional constraints on the existing protocols of Mobile IP. Scenario 2 (MPLS-based Mobile IP Route Optimization) applies Mobile IP Route Optimization [12] to MPLS-based network. A Mobile IP using Route Optimization defines Route Optimization messages and extensions to the base protocol to optimize datagram routing to a mobile node. using MPLS-based Mobile IP Route Optimization, Ingress LER may cache the binding of a mobile node, and then tunnel datagrams through the established LSP for the mobile node directly to the care-of address, bypassing the mobile node's home agent. This scenario are also provided to allow datagrams in flight when a mobile node moves, and datagrams sent based on an out-of-date cached binding, to be forwarded directly to the mobile node's new binding by using LSP extension method. In this scheme, the forwarding path should be pre- calculated by query process. The cache imposition or label binding operation may be done at the LER/FA. Scenario 3 (MPLS-based Hierarchical Mobile IP) applies Hierarchical Mobile IP [4] to MPLS-based network The Hierarchical Mobile IP scheme introduced in Mobile IP Regional Registration allows a mobile nodeto perform registrations locally with a Gateway Foreign Agent (GFA) in order to reduce the number of signaling messages to the home network. This achieves a reduction in the signaling delay when a mobile node moves between foreign agents and therefore improves the performance of such handoffs. In the MPLS-based Hierarchical Mobile IP scenario, when a mobile node migrates to the adjacent subnet, it performs regional registration and partial LSP re-establishment method. In the partial LSP re-establishment method, a LSP between anchor foreign agent and new foreign agent is established newly and existing LSP between home agent and foreign agent remains. So it should reduce LSP setup latency than conventional integration of Mobile IP and MPLS. To deliver the Mobile IP packets through the MPLS network, it requires the IP encapsulation [7]. Far from home location, the mobile node should be registered to the foreign LER with proper agent discovery process. The registration process should be also needed between the home agent and the corresponding foreign agent through the MPLS network. While a node tries to call the mobile node, data forwarding path with help of home agent should be established between the source LER and the destination LERs. The LSP by the LDP operation would enable to label the IP packets and forwards them at the destination mobile node via the MPLS network. 2. The MPLS Network Architecture with Mobility Support 2.1. Assumptions and Requirements In order to provide the backbone solution for Mobile IP network, it considers the following assumptions on the MPLS network. Choi, et al. Expires October 2001 [Page 4] Internet Draft Draft-choi-mobileip-ldpext-01.txt October 2001 - There are no additional requirements on the existing Mobile IP protocol such as agent discovery, registration, and routing. - All the regional Mobile IP networks should be connected at the LER which will be a external gateway router to communicate the external world. - In the MPLS backbone network, all the LERs are equipped with foreign agent to identify the visiting mobile nodes. In case that a number of foreign agents are in a Mobile IP network, the foreign agent attached to the LER has a responsibility to communicate to the external world. - The home agent should be located at the LER or the LSR. If a small-scale Mobile IP network already has a number of home agents to cover their own regional area, it should discriminate from the home agents interfaced to the MPLS network. The relevant registration procedure is required for the Mobile IP network on a number of home agents. A mobile node should register the home agent interfaced to the MPLS network while moving to external world. It can extend the registration procedure of Mobile IP service [5],[6]. - The forwarding process on the MPLS network should be taken on the datagram IP traffic (the UDP traffic) as well as the stream-like IP traffic (the TCP traffic). - We assume that the HAs and FAs support security associations Depending on the functionalities of Mobile IP protocols on the MPLS network, the following assumptions are required. - In Scenario 1 (MPLS-based Mobile IP), all the LERs have to operate the home agent. It means that a mobile node should be identified both from the home agent and the foreign agent at visiting area while moving to foreign area [5],[6]. - When a node sends the IP packets to the mobile node, the LER with home agent intercepts and forward them to the corresponding LER/FA on temporarily visiting area. - In Scenario 2 (MPLS-based Mobile IP Route Optimization), we assume that the data forwarding paths should be pre-calculated at the originating LER. - In Scenario 3 (MPLS-based Mobile IP Regional Registration), we assume that the foreign agents support Regional Registration and security associations have been established among a Gateway foreign Agent (GFA) and all the foreign agents beneath it in the hierarchy and that when a mobile node performs registration at its home network, registration keys are generated and distributed to the mobile node and to the GFA. The GFA may then in turn distribute the registration keys to the foreign agents beneath it in the hierarchy. - We assume several hierarchical levels of foreign agent in the visited domain. At the top level of the hierarchy, there is at least one GFA. A GFA must have publicly routable address. Beneath a GFA, there are one or more foreign agent. The regional foreign agent and their GFA must be compatible. HA, FA and GFA work LER, and RFA works LSR. They support both MPLS and Mobile IP using hierarchical foreign agent functionality. If home agent and GFA Choi, et al. Expires October 2001 [Page 5] Internet Draft Draft-choi-mobileip-ldpext-01.txt October 2001 are located in seperated MPLS network, then labeled packets from home agent to GFA must be tunneled through the public MPLS network. - We also assume on the mobile wireless IP networks that are divided into a number of cell regions according to geographical area. Each cell is covered by a Base Station (BS), which provides wireless IP access to the MN. The BS is connected to the LER to support mobility. 2.2. Network Architecture and Service Scenarios 2.2.1. MPLS-based Mobile IP Scenario In this section, we propose the MPLS network architecture and tunneling procedures to support the Mobile IP network. Similar concerns on the integration of MPLS network and Mobile IP network are also investigated in [8]. The MPLS network to support Mobile IP service doesn't use IP-in-IP encapsulation. The label switched path (LSP) tunnel provides a lower layer tunneling scheme independent on high layer applications. It notes that the IP-in-IP tunneling utilizes the layer 3 forwarding capability in IP routing. The ingress LER forwards IP packets all the way to the home agent to the egress LER to the foreign mobile node. The whole forwarding process is done at the MPLS layer. The home agent doesn't need to involve the IP layer forwarding to a mobile node. Since label header is much smaller than IP encapsulation header, the header overhead from home agent to foreign agent is also reduced. It can improve the scalability of Mobile IP protocol. Moreover, an LSP satisfying the quality-of-service (QoS) requirements and traffic engineering could be set up with Constraint-Based Label Distribution Protocol (CR-LDP) or RSVP-TE [9],[10]. Figure 1 shows the MPLS network architecture using Scenario 1 (MPLS- based Mobile IP). In this scenario, a home agent is located at the LER1 and has a capability to intercept IP packets for a mobile node. When a mobile node from the LER2/HA area is temporarily moving to the LER3 area, the registration is required to home agent via LER3/FA1. When a correspondent node at LER1 sends IP packets to a current mobile node, the LSP tunnels would be established from LER1 to LER2/HA and cascading from LER2/HA to LER3/FA1. The relevant LDP operations will be taken with associations of Forwarding Equivalence Class (FEC). When a mobile node is moving to the LER4/FA2 area during active service time, the LSP tunnel from LER1 to LER2 may be extended or re-configured to LER4 with update on HA, FA1 and FA2. The seamless LSP tunnel to LER4 may be required for the real-time applications. To encapsulate IP packets with a MPLS header, the destination address of the MPLS header is initially the LER3. The MPLS label stack operation may cut through the corresponding address of the tunnel's receive endpoint. If the ingress point of the LSP tunnel wishes to Choi, et al. Expires October 2001 [Page 6] Internet Draft Draft-choi-mobileip-ldpext-01.txt October 2001 put a labeled packet into the MPLS network, it should replace the label value at the top of the stack with a label value that was distributed to it by the tunnel's receive endpoint. Then it must push on the label which corresponds to the tunnel itself, as distributed to it by the next hop along the tunnel. To allow this, the tunnel endpoints should be explicit label distribution peers. +----+ +--+ +----+ | HA | |CN|-------+LER1+xxxxxxxxxxxxx+LER2| +--+ +----+ ++--++ x \ x \ x \ +---++ ++---+ |LSR1| |LSR2| ++--++ +---++ / x \ / x \ / x \ +----+ +----+ +--+-+ | FA1| | FA2| | FA3| |LER3| |LER4| |LER5| +-+--+ +-+--+ +----+ | | | | +--+ +--+ |MN| ----> |MN| +--+ +--+ xxx : Label Switched Path --- : Route using normal hop-by-hop packet forwarding LER: Label Edge Router LSR: Label Switching Router HA: Home Agent FA: Foreign Agent MN: Mobile Node CN: Correspondent Node Figure 1. The MPLS Network Architecture with Mobility Support (Scenario 1 : MPLS-based Mobile IP) In this scenario, the functions of mobile agents can be located in the LERs. The LSPs can be setup the same way as "tunnels" are setup between home agent and foreign agents. In addition it allows constrained based routing and the QoS path between the agents can be guaranteed. 2.2.2. MPLS-based Mobile IP Route Optimization Scenario Choi, et al. Expires October 2001 [Page 7] Internet Draft Draft-choi-mobileip-ldpext-01.txt October 2001 The Route Optimization scheme introduced Route Optimization in Mobile IP [12] defines Route Optimization messages and extensions to the base protocol to optimize datagram routing to a mobile node. This section provides for a number of additions to Route Optimization in Mobile IP in terms of functionalities of the MPLS protocol. It is preferable of case that the forwarding path from ingress LER should be cut through the egress LER/FA, the care-of address of the mobile node. For all the cases, the ingress LER should find forwarding path with relevant query process. For this scenario, it requires the query process(or binding update) to find the destination tunnel endpoints on the MPLS network. The LER tries to look up their label table for incoming packets. When the relevant port entries and labels are found, it sends them to the output port with a label header. If no entry is returned, it sends packets using hop-by-hop packet forwarding method. Figure 2 shows the MPLS network architecture using Scenario 2 (MPLS- based Mobile IP Route Optimization). +----+ +--+ +----+ | HA | |CN|--------+LER1+-------+LER2| +--+ +--+-+ ++-+-+ x / \ x / \ x / \ ++--++ +----+ |LSR1| |LSR2| ++--++ +--+-+ / x \ / x \ / x \ +--+-+ +-+--+ +--+-+ | FA1| | FA2| | FA3| |LER3| |LER4| |LER5| +-+--+ +-+--+ +----+ | | | | +--+ +--+ |MN| ----> |MN| +--+ +--+ xxx : Label Switched Path --- : Route using normal hop-by-hop packet forwarding Figure 2. The MPLS Network Architecture with Mobility Support (Scenario 2 : MPLS-based Mobile IP Route Optimization) MPLS-based Mobile IP Route Optimization provides a means for any node to maintain a binding cache containing the care-of address of one or Choi, et al. Expires October 2001 [Page 8] Internet Draft Draft-choi-mobileip-ldpext-01.txt October 2001 more mobile nodes in the Ingress LER. When sending an IP datagram to a mobile node, if the Ingress LER has a binding cache entry for the destination mobile node, it may tunnel the datagram directly to the care-of address indicated in the cached mobility binding by using LDP. In the absence of any binding cache entry, datagrams destined for a mobile node will be routed to the mobile node's home network in the same way as any other IP datagrams, and then tunneled to the mobile node's current care-of address by the mobile node's home agent. The original sender of the datagram may be informed of the mobile node's current mobility binding, giving the sender an opportunity to cache the binding to optimize this indirect routing of a datagram to a mobile node. The Binding Update Message which is forwarded to the correspondent node is intercepted by Ingress LER. By using the Route Optimization in Mobile IP, The home agent should then send a Binding Update message to the Ingress LER of correspondent node, informing it of the mobile node's current mobility binding. Similarly, when any foreign agent receives a tunneled datagram, if it has a binding cache entry for the destination mobile node and thus has no visitor list entry for this mobile node, the receiving node should send a Binding Warning message to the mobile node's home agent, advising it to send a Binding Update message to the Ingress LER that tunneled this datagram. When sending an IP datagram, if Ingress LER of the sending node has a binding cache entry for the destination node, it should tunnel the datagram to the mobile node's care-of address through LSP. For the matters of QoS and traffic control, it should investigate whether the bandwidths between ingress LER and egress LER are available or not. With these concerns, the CR-LDP or RSVP-TE may be useful to take a relevant forwarding path. When a mobile node moves from Foreign IP Network FA1 to FA2, it sends a message to register the new FA. Signaling messages should be exchanged between old foreign agent and new foreign agent to extend the LSP tunnel. It extends the current LSP by establishing a LSP between current foreign agent and new foreign agent. During that time, old foreign agent buffers all the packets from and to the mobile node. Once the LSP is established, packets are sent along the new path to the mobile node. 2.2.3. MPLS-based Hierarchical Mobile IP network Scenario If we employ the MPLS-based Mobile IP, whenever it migrates to adjacent subnet, not only should the mobile node register at the home agent through the new foreign agent, but also should set LSP up one more time from the home agent to the foreign agent using a Label Distribution Protocol (LDP). Therefore the handover latency is increased, and the signaling traffic also becomes heavy. If a mobile node migrate high frequency rate, this scheme induces that signalling bandwidth for registration Choi, et al. Expires October 2001 [Page 9] Internet Draft Draft-choi-mobileip-ldpext-01.txt October 2001 and LSP setup is more increased, and packet loss increase during handover. The Hierarchical Mobile IPv4 scheme introduced in Mobile IP Regional Registration [4] allows a mobile node to perform registration locally in order to reduce the number of signaling message to the home network. This achieves a reduction in the signaling delay when a mobile node moves between Foreign Agents and therefore improves the performance of such handoffs. This section provides for a number of additions to Hierarchical Mobile IP in terms of functionalities of the MPLS protocol within the hierarchical domain. The integration of MPLS and Mobile-IP using Hierarchical foreign agent that we suggest is shown in Figure 3. +----+ +----+ | HA | | GFA| |LER1+xxxxxxxxxxx+LER2| +-+--+ +-++-+ x x \ x x \ x x \ +--+ +--+-+ +---++ +-+--+ |CN|------+LER3| |RFA1| |RFA2| +--+ +----+ |LSR1| |LSR2| ++--++ +--+-+ / x \ / x \ / x \ +--+-+ +-+--+ +-+--+ | FA1| | FA2| | FA3| |LER4| |LER5| |LER6| ++--++ +-+--+ +----+ / \ \ / \ \ +-++ ++-+ +-++ |MN| ---> |MN| --> |MN| +--+ +--+ +--+ xxx : Label Switched Path --- : Route using normal hop-by-hop packet forwarding Figure 3. The MPLS Network Architecture with Mobility Support (Scenario 3 : MPLS-based Hierarchical Mobile IP) The MPLS-based Hierarchical Mobile IP scheme consists of two major components: the "MPLS-based Hierarchical Mobile IP architecture" part which addresses the issues of enhancing MPLS for the support of terminal and service mobility and the "LSP re-routing schemes" part which is concerned with handoff. Choi, et al. Expires October 2001 [Page 10] Internet Draft Draft-choi-mobileip-ldpext-01.txt October 2001 MPLS-based Hierarchical Mobile IP architecture is constructed to be distributed the functionality of MPLS based mobility agents to allow frequent and seamless location management operations while maintaining ongoing sessions and maximizing data throughput. In this architecture, the foreign agents are organized into a hierarchy to handle local movements of mobile nodes within the domain. With a hierarchy of foreign agents, small changes of location can be handled by one of the foreign agents in the hierarchy within whose covering range the mobile node remains. Any correspondent node should be able to transparently communicate with mobile nodes while mobile nodes are in the visited networks, that is, without any requirements on the correspondent nodes. In the MPLS-based Hierarchical Mobile IP scheme, when a mobile node migrates to the adjacent subnet, it performs regional registration and LSP re-routing using partial LSP re-establishment method. In the partial LSP re-establishment method, LSP between anchor RFA and new FA is established newly and existing LSP between home agent and foreign agent remains, where anchor RFA located in upper Hierarchy of both old foreign agent and new foreign agent. So it should reduce LSP setup latency than LSP re-establishment method of MPLS-based Mobile IP scheme. 2.3. Routing Considerations The routing on the MPLS network is depending on locations of home agent and foreign agent. In MPLS network, through flow classification, each flow may be different in grades of service. A LSP should meet certain QoS requirements of differential flows using CR-LDP or RSVP- TE. The detail discussions on routing issues of the MPLS network with mobility support are further study. 2.4. Interworking of existing Mobile IP network It requires for further study. 3. Description of the Protocol 3.1. General Assumptions In this draft, the main issues of MPLS network architecture with mobility support are focused on the control procedure such as registration, LSP establishment and LSP Extension, etc. Agent advertisement and discovery procedure is unmodified in the existing Mobile IP protocol. It is required to program appropriate QoS support for the MN's packets in the intermediate network domains, so that the performance of QoS-sensitive applications running on the MN is maintained at Choi, et al. Expires October 2001 [Page 11] Internet Draft Draft-choi-mobileip-ldpext-01.txt October 2001 desired level. To achieve this, our model adopts QoS Object [4] to interoperate with CR-LDP/RSVP-TE. In these MPLS-based Mobile IP schemes, wireless IP communicators will be turned around the clock, ready to receive or initiate services. In fact, the vast majority of subscribers will not be actively communicating most of the time. Rather, wireless IP communicators will be switched on, ready for service, constantly reachable by the wireless Internet. The MN will be in an idle state but passively connected to the network infrastructure. Thus design principle is that only active data are supposed to traverse over QoS guaranteed LSP. This will prevent LSP abusing that can be caused by lots of control packets. If LSP is established for the datagram IP traffic (the UDP traffic), LSP setup and release repetition would occur because the traffic are generated sparsely. So our model considers only TCP traffic. There is no additional Message or TLV/Object on existing CR-LDP/RSVP- TE to setup QoS guaranteed LSP between CN's LER and MN's LER. The suggested model adopts data-driven LSP setup. 3.2. LSP Tunnels for Mobility Support There requires LSP tunnels in the each MPLS-based Mobile IP schemes The existing LDP specification is well described to establish LSP tunnels for mobility. The address of home agent and foreign agent for LSP tunnels will be given by the Registration and Agent Discovery Procedure within the Mobile IP protocol. While traditional traffic engineered MPLS are unidirectional, generalized MPLS [14] supports the establishment of bi-directional LSP. In our MPLS-based Mobile IP schemes, bi-directional LSP have the benefit of lower setup latency and lower number of messages required during setup. It takes only one initiator-eliminator round trip time. The LSP with QoS constraints is contained in the CR-LDP or RSVP-TE specification [9],[10]. 3.2.1. MPLS-based Mobile IP Scenario There are LSP tunnels in the MPLS-based Mobile IP network; - LSP tunnels between the ingress LER and home agent - LSP tunnels between home agent and egress LER/FA 3.2.2. MPLS-based Mobile IP Route Optimization There are LSP tunnels in the MPLS-based Mobile IP Route Optimization; - Direct LSP tunnels between ingress LER and egress LER/FA - LSP tunnel between old foreign agent and new foreign agent Choi, et al. Expires October 2001 [Page 12] Internet Draft Draft-choi-mobileip-ldpext-01.txt October 2001 The tunneling procedure of this model might be different from that of Scenario 1. When a correspondent node sends packets to a mobile node located in the foreign area, the ingress LER has to decide the relevant forwarding path depending on routing information. 3.2.3. MPLS-based Hierarchical Mobile IP Scenario There are LSP tunnels in the MPLS-based Hierarchical Mobile IP; - LSP tunnels between the ingress LER and home agent - LSP tunnels between home agent and GFA - LSP tunnels between GFA and RFA - LSP tunnels between RFA and egress LER/FA The address of GFA, RFA and egress LER/FA for LSP tunnels will be given by the Registration Procedure within the Mobile IP Regional Registration [4]. 3.3. Agent Advertisement and Solicitation Agent advertisement and discovery procedure is unmodified in the existing Mobile IP protocol. Mobile agents (i.e., foreign agents and home agents) advertise their presence via Agent Advertisement messages. A mobile node may optionally solicit an Agent Advertisement message from any locally attached mobility agents through an Agent Solicitation message. A mobile node receives these Agent Advertisements and determines whether it is on its home network or a foreign network. FA+HA MN | | |---------------------------------->| | Agent Advertisement Message | | | |<----------------------------------| | Agent Solicitation Message | | | Figure 4. Agent Discovery of Mobile Node at the MPLS Network If sent periodically, the nominal interval at which Agent Advertisements are sent should be 1/3 of the advertisement Lifetime given in the MPLS shim header. This allows a mobile node to miss three successive advertisements before deleting the agent from its list of valid agents. 3.4. Registration and LSP setup for Mobile Node 3.4.1. MPLS-based Mobile IP scheme Scenario Choi, et al. Expires October 2001 [Page 13] Internet Draft Draft-choi-mobileip-ldpext-01.txt October 2001 In the registration procedure, the mobile node determines whether it is at home or in a foreign network when it receives Agent Advertisement Messages broadcast by the mobility agents. If the mobile node determines that it is in a foreign network, the mobile node acquires a temporary care-of address from foreign agent and sends a Registration Request to foreign agent. Since foreign agent is an edge LER, it will analyze the incoming Registration Request Message and get the destination address of the request. Then, foreign agent updates its routing table with the value of mobile node home address. In addition, it sets the outgoing port value of this entry to be the incoming port number from which it received the registration request. Based on the IP routing table, foreign agent forwards the Registration Request Message toward home agent. MN FA1(LER2) HA | | | |---------------------------->| | | Broadcast Agent | | | Solicitation Message(ICMP) | | |<----------------------------| | | Broadcast Agent | | | Advertisement Message(ICMP) | | | | | |---------------------------->| | | MN Registration Request(UDP)|------------------------------->| | | MN Registration Request (UDP) | | | | | |<-------------------------------| |<----------------------------| MN Registration Reply (UDP) | | MN Registration Reply (UDP) | | | | | | ( LSP setup procedure in response to detect packet flow ) | | | | | | (no entry between HA and FA)| | |<-------------------------------| | | Label Request Message(LDP) | | | | | |------------------------------->| | | Label Mapping Message(LDP) | | | | Figure 5. Registration of mobile node at the MPLS-based Mobile IP network The Registration Request Message is forwarded to home agent using normal IP hop-by-hop routing. When home agent gets the Registration Request Message and learns the care-of address, it sends Registration Reply Message to the mobile node via foreign agent. In the home agent, if long lived message exists between same correspondent node and destination mobile node, then the home agent will send a Label Request Message using LDP to foreign agent with the care-of address Choi, et al. Expires October 2001 [Page 14] Internet Draft Draft-choi-mobileip-ldpext-01.txt October 2001 as FEC. A foreign agent replies with an LDP Label Mapping Message to the home agent. When this Label Mapping Message arrives at home agent, the LSP would have been established. After that, home agent changes its label table that uses the mobile node home address as FEC. It sets the outgoing port entries of the LSP from home agent to foreign agent. In this way, home agent can relay the packets destined to mobile node home address to its current location in the foreign network. When foreign agent receives packets on the LSP, it records the incoming port number, label value and IP address of the correspondent node of the packet. Therefore, the foreign agent should send user packets through the established bi-directional LSP from the mobile node to the correspondent node because it should know that for which mobile node the LSP is established. Packets from a correspondent node to the mobile node are addressed to the mobile node home address. If the mobile node is located in a foreign network, packets are intercepted by the home agent. The home agent uses the incoming label value as an index to look up its label table. It inserts the label value in the label table into packet and sends it out through the port indicated in the table. If a mobile node is still in the home network, then outgoing port entries are empty. The packet will be sent to the IP layer and sent out from the port indicated in the corresponding routing table entry. If a mobile node is in foreign network and a LSP is established from the home agent to the foreign agent, then the home agent must send user packets to the foreign agent by using label swapping method. 3.4.2. MPLS-based Mobile IP Route Optimization Scenario MPLS-based Mobile IP Route Optimization scheme uses the same Registration and Advertisement procedure with MPLS-based Mobile IP. The Registration Request Message is forwarded to home agent using normal IP hop-by-hop routing. When home agent gets the Registration Request Message and learns the care-of address, it sends Registration Reply Message to the mobile node via foreign agent. MN FA1(LER2) HA Ingress LER CN | | | | | |--------------->| | | | | Agent | | | | | Solicitation | | | | |<---------------| | | | | Agent | | | | | Advertisement | | | | | | | | | |--------------->| | | | | Registration |---------------->| | | | Request | Registration | | | | | Request | | | | |<----------------| | | Choi, et al. Expires October 2001 [Page 15] Internet Draft Draft-choi-mobileip-ldpext-01.txt October 2001 |<---------------| Registration | | | | Registration | Response | | | | Response | | | | | | | | | | ( Binding Update Procedure of Ingress LER ) | | | | | | | | | (no label entry) | | | | |<-------------| | | | | User Packets | | | |<---------------| | | | | User Packets | | | |<----------------| | | | | User Packets |--------------->| | |<---------------| | Binding Update | | | User Packets | | | | | |<---------------------------------| | | | Label Request Message | | | | | | | | |--------------------------------->| | | | Label Mapping Message | | | | | |<-------------| | | | | User Packets | | |<---------------------------------| | | | User Packets (through the LSP) | | |<---------------| | | | | User Packets | | | | | | | | | Figure 6. Registration and Binding Update at the MPLS-based Mobile IP Route Optimization When a mobile node's home agent intercepts a datagram from the home network and tunnels it to the mobile node, the home agent should then send a Binding Update Message to the Ingress LER of correspondent node, informing it of the mobile node's current mobility binding. For a Binding Update to be authenticated by the Ingress LER of original correspondent node, the Ingress LER and the home agent must have established a mobility security association. When any foreign agent receives a tunneled datagram, if it has a binding cache entry for the destination mobile node and thus has no visitor list entry for this mobile node, the node receiving this tunneled datagram may deduce that the tunneling node has an out-of- date binding cache entry for this mobile node. In this case, the receiving node should send a Binding Warning Message to the mobile node's home agent, advising it to send a Binding Update message to the Ingress LER that tunneled this datagram. As in the case of a Binding Update sent by the mobile node's home agent, Ingress LER may maintain a binding cache to optimize mobile node's communication with mobile nodes. An Ingress LER may create or update a binding cache entry for a mobile node only when it has received and authenticated the mobile node's mobility binding. As before, each Choi, et al. Expires October 2001 [Page 16] Internet Draft Draft-choi-mobileip-ldpext-01.txt October 2001 binding in the binding cache also has an associated lifetime, specified in the Binding Update Message in which the node obtained the binding. After the expiration of this time period, the binding is deleted from the cache. For the matters of QoS and traffic control, it should investigate whether the bandwidths between ingress LER and egress LER are available or not. With these concerns, the CR-LDP or RSVP-TE may be useful to take a relevant forwarding path. The detail discussions on MPLS-based Mobile IP Route Optimization scenario require for further study. In the absence of any binding cache entry, datagrams destined for a mobile node will be routed to the mobile node's home network in the same way as any other IP datagram, and then tunneled to the mobile node's current care-of address by the mobile node's home agent. With Binding information received from home agent, Ingress LER initiates the label binding process to the egress LER/FA to a mobile node. After that, Ingress LER updates the row in its label table that uses the care-of address of a mobile node as FEC. It sets a label value and outgoing port entries. When a correspondent node sends IP packets to Ingress LER, the Ingress LER searches for forwarding label entries to the destination mobile node. If a label entry found, it sends IP packets to the care- of address of a mobile node through the LSP. If not found, Ingress LER should send IP packet using normal IP hop-by-hop routing to the mobile node via home agent. 3.4.3. MPLS-based Hierarchical Mobile IP scheme Scenario A foreign agent advertises addresses of hierarchical foreign agent in order between its own address (first) and the GFA address (last) in the Agent Advertisement. If the mobile node determines that it is in a foreign network, the mobile node sends a Registration Request, with the care-of address set to the GFA address announced in the Agent Advertisement. When the foreign agent closest the mobile node receives the Regional Registration, because the foreign agent is a LER, it will analyze the incoming Registration Request message and relays the Registration Request to the next RFA in the hierarchy toward the GFA. The next RFA that is a LSR receives the Registration Request. For each pending or current registration, an RFA maintains a visitor list entry. RFA stores mobile node entry its mobile node table, and insert its own address to the registration packet. This procedure is repeated to the GFA. When the GFA receives the Registration Request, it cashes information about the next lower-level RFA in the hierarchy. It then relays the Registration Request to the home agent. For each pending or current registration, the GFA maintains a visitor list entry. The request message is forwarded to home agent hop-by-hop using normal IP routing. Choi, et al. Expires October 2001 [Page 17] Internet Draft Draft-choi-mobileip-ldpext-01.txt October 2001 When home agent gets the Registration Request message and learns the care-of address of GFA within the packet, the home agent sends a Registration Reply to the GFA. When GFA receives the Registration Reply message, GFA can recognize what the Registration Reply is come from the specific mobile node that is registered. GFA can know the lower-level RFA of a registered mobile node by reading the information of the mobile node entry corresponding to a received Registration Reply packet. And then GFA sends a Registration Reply to the RFA. This procedure is repeated in every FA in the hierarchy, until the Registration Reply message reaches the FA closest to the mobile node. When the lowest-level FA receives Registration Reply, it should checks its cached information and relays the Registration Reply to the mobile node. MN FA RFA GFA HA | | | | | |------------->| | | | | Registration | | | | | Request |------------>| | | | | Registration| | | | | Request |------------->| | | | | Registration | | | | | Request |------------->| | | | | Registration | | | | | Request | | | | |<-------------| | | | | Registration | | | |<-------------| Reply | | | | Registration | | | |<------------| Reply | | | | Registration| | | |<-------------| Reply | (User packets arrive) | Registration | | |<-------------| | Reply | | | Label Request| | | | |------------->| | | | | Label Mapping| | | |<-------------| | | | | Label Request| | | | |------------->| | | | | Label Mapping| | | |<------------| | | | |Label Request| | | | |------------>| | | | |Label Mapping| | | | | | | | Figure 7. Registration and label establishment procedure When home agent gets user packets to the mobile node, it will send a Label Request Message using LDP to GFA with the care-of address as FEC. GFA replies with an LDP label mapping message to home agent. GFA Choi, et al. Expires October 2001 [Page 18] Internet Draft Draft-choi-mobileip-ldpext-01.txt October 2001 should assign labels and keep the Home address of a mobile node and binding table of a specific label about being registered mobile nodes. When this Label Mapping Message arrives at home agent, the LSP would have been established. Figure 7 shows the registration and LSP establishment procedure. After that, a home agent changes the row in its label table that uses the mobile node home address as FEC. It sets the empty out label and outgoing port entries to the values of out label and outgoing port. In this way, home agent can relay the packets destined to mobile node home address to its GFA in the foreign network. Finally, home agent sends user packets to GFA along the LSP from home agent to GFA. When GFA receives the labeled user packets, GFA can recognize what the Registration Reply is come from the specific mobile node that is registered after the operation of label pop. GFA writes the label value attached to user packets on an incoming value of corresponding mobile node. GFA can know the lower-level RFA of a registered mobile node by reading the information of the mobile node entry corresponding to a received user packets. GFA will send a label request using LDP to next RFA with the care-of address as FEC. RFA replies with an LDP Label Mapping Message to the home agent. RFA should keep the information of binding table and the Home address by assigning a Label about the registered whole mobile nodes. When this Label Mapping Message arrives at GFA, the LSP would have been established. After that, GFA changes the row in its label table that uses the mobile node home address as FEC. It sets the empty out label and outgoing port entries to the values of out label and outgoing port. In this way, GFA can relay the packets destined to mobile node home address from home agent to RFA. Finally, GFA sends user packets to RFA through the LSP. This procedure is repeated in every FA in the hierarchy, until the user packets reach the FA closest to the mobile node. When the lowest-level FA receives user packets, it should remove its labels and checks its cached information and relay the user packets to the mobile node. If the packet is arrived at ingress LER from a CH, the ingress LER certifies the destination IP address and find the mapped label in a label information base (LIB). If a mapped Label is found, the ingress LER attatchs the label and transmits to downstream LSR. But If the mapped Label is not found, the ingress LER should set LSP up using LDP before transmitting packets. The ingress LER transmites the Label Request Message about host address FEC using Downstream-on-demand mode to destination IP address of the packet. The home agent, which receives the Label Request Message about a mobile node by using Proxy ARP or gratuitous ARP, transmits the Label Mapping message about home IP address of a mobile node to a upstream LSR instead of the mobile node. At this time home agent should be able to recognize the home IP address of corresponding mobile node using label value that is received from a upstream LSR by the Choi, et al. Expires October 2001 [Page 19] Internet Draft Draft-choi-mobileip-ldpext-01.txt October 2001 recorded tabel that is consist of home IP addresses and mapped label. A home agent records the label about a GFA and a mobile node in label table, which consists of the upstream LSRs and incoming labels that are mapped into outgoing labels. The table is composed to be transmitted to a GFA by swapping the packet about conveyed a mobile node from ingress LERs through intermediate LSRs. The ingress LER that receives a packet from a correspondent node recognizes the destination IP address of the packet and transmits a labeled packet through corresponding LSP. In the case of the destination IP address is mobile node, labelled packet is transmitted to a home agent through a LSP. In the MPLS Network, the limited label number can make the limitation of a label distribution. In the case of global network, the limitation of label number can be fatal. But applying the piggybacking to the routing protocol to distribute a label about address prefix can solve the problem. In this case, the FEC in the network may transmit to an egress LER located on the border. If a home agent performs as egress LER, the packet can be transmitted to a home agent, by the reason of merged stream, the home agent can recognize the mobile node after watching the destination IP address, that is in the each IP header from FEC. So the delay is larger than that of using the layer 2 swapping only to transmit to the foreign agent. Therefore the label distribution method using Host address prefix is preferred in the MPLS-based Mobile-IP network. In our MPLS-based Hierarchical Mobile IP scheme, the whole forwarding process is done at the MPLS layer and home agent and foreign agents doesn't need to involve the IP layer in forwarding the packet to a mobile node. 3.5. Handoff and LSP re-routing 3.5.1. MPLS-based Mobile IP scheme Scenario In the MPLS-based Mobile IP scheme, when mobile node moves from one foreign agent to another, the registration procedure is repeated once between the home agent and new foreign agent. The existing LSP should be changed to the new foreign agent. The following issues are further considered on the MPLS network. - LSP rerouting - LSP extension - Label binding for the LSP from correspondent node to new foreign agent 3.5.2. MPLS-based Mobile IP Route Optimization Scenario IP datagrams intercepted by the home agent after the new registration are tunneled to the mobile node's new care-of address, but datagrams in flight that had already been intercepted by the home agent and tunneled to the old care-of address when the mobile node moved are likely to be lost. Choi, et al. Expires October 2001 [Page 20] Internet Draft Draft-choi-mobileip-ldpext-01.txt October 2001 Route Optimization provides a means for the mobile node's previous foreign agent to be reliably notified of the mobile node's new mobility binding, allowing datagrams in flight to the mobile node's previous foreign agent to be forwarded to its new care-of address. When old foreign agent received Binding Update Message from the new foreign agent to notify the mobile node's new location, it looks up its forwarding information base (FIB) to find a label of mobile node. If forwarding information base has a label of that mobile node, old foreign agent set up label switched path with existing traffic parameters for the mobile node to the new foreign agent. Therefore existing label switched path from a LER to a foreign agent should be extended to the new foreign agent. After signaling messages should be exchanged between old foreign agent and new foreign agent to extend the LSP tunnel. It extends the current LSP by establishing a LSP between current foreign agent and new foreign agent by using above LSP extension method. During that time, old foreign agent buffers all the packets from and to the mobile node. Once the LSP is established, packets are sent along the new path to the mobile node. Any tunneled datagrams for the mobile node that arrive at its previous foreign agent after the extended LSP has been created can then be re-tunneled to the mobile node's new care-of address through the extended LSP. If there isn't any label to the destination mobile node at the old foreign agent, the old foreign agent should send user packets which are received from correspondent node to the new foreign agent by using IP-in-IP tunneling method. The MPLS Network with Mobility Support Existing LSP +---------+ +----+ | |Home | | HA | +------+ +------+ V +----+ +------+ |Mobile IP+-+LER1+--+ LSR1 +--+ LSR2 +-----+ FA1+----+Old MN| |Network | +--+-+ +-+----+ +------+ |LER2| +------+ +---------+ \ | +----+ | \ | Extended| |Handoff \ | LSP | | \ | | V +-+-+--+ +----+ +------+ | LER3 | | FA2+----+New MN| +---+--+ |LER4| +------+ | +----+ +-+--+ | CN | +----+ Choi, et al. Expires October 2001 [Page 21] Internet Draft Draft-choi-mobileip-ldpext-01.txt October 2001 Figure 8. LSP Extension for Mobile IP Whenever a mobile node migrates to a adjacent subnet, existing LSP from the ingress LER to the old foreign agent is extended to the new foreign agent. When an ingress LER receives a Binding Update Message in response to a Binding Warning Message or Binding Request Message, the ingress LER should recognize that a destination mobile node migrate the new foreign agent. However, whenever a destination mobile node migrates, the ingress LER shouldn't set up new LSP to the new foreign agent. When the QoS of LSP tunnel is temporarily degraded, LSP re- establishment is triggered by the ingress LER. After LSP re- establishment, the route between ingress LER and new foreign agent can be optimized. Old path is torn down and new path is set up. MN New FA Old FA HA ... CN | | | | | |-------------->| | | | | Reg. Request +| | | | | Binding Update|------------------------------>| | | | Registration Request | | | |-------------->| | | | | Binding Update| | | | |<--------------| | | | | Binding Ack. | | | |<--------------| | | | | Binding Ack. |<--------------| | | | | Label Request | | | | |-------------->| | | | | Label Mapping | | | | | | | | | |<------------------------------| | | | Registration Reply | | |<--------------| | | | | Reg. Reply | | | | Figure 9. Message Sequence for LSP Extension The LSP extension procedures in Figure 9 are as follows. - A mobile node moves to a new foreign agent and sends a Registration Request and Binding Update message to new foreign agent. - New foreign agent sends a Registration Request message to home agent and sends a Binding Update Message to the old foreign agent. - When the old foreign agent received Binding Update Message, it responses with Binding Acknowledgement Message to the mobile node via the new foreign agent. And old foreign agent may send Label Request Message to the new foreign agent Choi, et al. Expires October 2001 [Page 22] Internet Draft Draft-choi-mobileip-ldpext-01.txt October 2001 - A LSP is established between old foreign agent and new foreign agent when old foreign agent receives Label Mapping message. - Then, a home agent sends Registration Reply message in response to the Registration Request. 3.5.3. MPLS-based Hierarchical Mobile IP Scenario In a Mobile IP Regional Registration [4], when a handover occurs, mobile node compares the new vector of care-of address with the old one. It chooses the lowest-level foreign agent that appears in both vectors, and sends a Regional Registration Request to that anchor foreign agent. Any higher-level agent need not be informed of this movement since the other end of its forwarding LSP tunnel still points to the current location of the mobile node. A Registration Request is forwarded to the GFA by way of one or more intermediate RFA. When the Registration Request message arrives at the first FA, the foreign agent checks its visitor list to see if this mobile node is already registered with it. If it is not, the foreign agent checks which next higher-level RFA to relay the Registration Request to. The next RFA checks its visitor list to see if the mobile node is already registered with it. If it is not, the RFA relays the message to the next higher-level RFA in the hierarchy toward the GFA. This process is repeated in each RFA in the hierarchy, until an RFA recognizes the mobile node as already registered. This RFA may be the GFA, or any RFA beneath it in the hierarchy. If the mobile node is already registered with this RFA, it will transmit the Registration Reply toward the lower-level RFA. When the lower-level RFA receives the Registration Reply, the RFA is able to point out the received Registration Reply so that the packet is associated with which mobile node. The RFA reads the information about mobile node entry equivalent to received Registration Reply, and recognizes the mobile node as the registered lower-level one. RFA will send Registration Reply message to the lower RFA. Above sequence is repeated up to the new FA of network that mobile node is moved to. If there is an established LSP about the mobile node to the anchor RFA, it will send a Label Request Message using LDP to the next lower-level RFA in the hierarchy. The lower-level RFA replies with an LDP Label Mapping Message to the upper-level. The foreign agents should keep the binding table information of a label and home address of a mobile node about registered whole mobile nodes by assigning Label. On the all mobile nodes registered to foreign agent, it is necessary to assign label, and to maintain the binding table of home address and label of mobile node. When a Label Mapping Message from lower-level RFA arrives at upper- level RFA, the LSP would have been established. After RFA received the label from the lower-level one, it is necessary to modify the label mapping entry on the associated mobile node in the label table. The incoming label value of label mapping entry is unchanged as the Choi, et al. Expires October 2001 [Page 23] Internet Draft Draft-choi-mobileip-ldpext-01.txt October 2001 received label value form the upper-level RFA, and outgoing label value is changed into new acquired label value from the new lower- level RFA through the Regional Registration method. And then, RFA will send a Label Request Message using LDP to next RFA with the care-of address as FEC. When this Label Mapping Message arrives at RFA, the LSP would have been established. Above sequence is repeated up to the new foreign agent of network that mobile node is moved to. In this way, the LSP is newly established from anchor foreign agent to new foreign agent. In this LSP partial re-establishment method, since the LSP is maintained from home agent to anchor foreign agent and a new LSP is established from anchor foreign agent to new foreign agent, the LSP setup time is reduced compared with the MPLS-based Mobile IP scheme. Packet is delivered from home agent to new foreign agent along the LSP by label swapping. New foreign agent receives the packet and looks up its label table. Since it is the egress of the LSP from home agent to new foreign agent, home agent strips off the label and sends the packet to the IP layer. Finally new foreign agent forwards the packet to mobile node based on the information in the newly added host specific row of routing table. A mobile node receives the packet sent by correspondent node. Figure 10 shows a Regional Registration procedure and a label distribution process from a mobile node to a RFA. MN FA RFA GFA HA | | | | | |------------->| | | | | Registration | | | | | Request |------------>| | | | | Registration| | | | | Request | | | | |<------------| | | | | Registration| | | |<-------------| Request | | | | Registration | | | | | Request | | | | | |<------------| | | | |Label Request| | | | |------------>| | | | |Label Mapping| | | | | | | | Figure 10. Regional registration and label distribution In MPLS-based Hierarchical Mobile IP network, additionally, it is necessary to clear the registration information on the old foreign agent and the upper-level RFA, and to release the LSP. If old locations are not deregistered, it is possible that tunnels are not correctly redirected when a mobile node moves back to a previous foreign agent. Choi, et al. Expires October 2001 [Page 24] Internet Draft Draft-choi-mobileip-ldpext-01.txt October 2001 The anchor RFA should send a Binding Update with a zero lifetime and Label Release Message to the previous care-of address it had registered for the mobile node. Each foreign agent receiving the Binding Update removes the mobile node from its visitor lists. And the LSP that is assigned between Upper-level foreign agents is released. The Binding Update and Label Release Message is relayed down to the care-of address of the mobile node known to that foreign agent, and each foreign agent in the hierarchy receiving this notification removes the mobile node from its visitor list. A LSP that is established to old foreign agent is released by receiving binding update and Label Release Messages. 4. Required Messages and TLVs There is no additional Message or TLV/Object on existing CR- LDP/RSVP-TE to setup QoS guaranteed LSP between CN's LER and MN's LER. 4.1 Required Messages and TLVs Any Messages, TLVs, and procedures not defined explicitly in this document are defined in the LDP Specification [3] and IP Mobility Support [4]. It can use Constraint-Based LSP Setup using LDP [2] as an informational document related to CR-LDP. 4.1.1. LDP PDUs Each LDP PDU is an LDP header followed by one or more LDP messages. The LDP header is: 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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Version | PDU Length | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | LDP Identifier | + +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Version Two octet unsigned integer containing version number PDU Length Two octet integer specifying the total length of this PDU in octets LDP Identifier Six octet field that uniquely identifies the label space of the sending LSR Choi, et al. Expires October 2001 [Page 25] Internet Draft Draft-choi-mobileip-ldpext-01.txt October 2001 4.1.2. Type-Length-Value Encoding LDP uses a Type-Length-Value (TLV) encoding scheme to encode much of the information carried in LDP messages. An LDP TLV is encoded as a 2 octet field that uses 14 bits to specify a Type and 2 bits to specify behavior when an LSR doesn't recognize the Type, followed by a 2 octet Length Field, followed by a variable length Value field. 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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |U|F| Type | Length | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | | | Value | ~ ~ | | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ U bit Unknown TLV bit. As defined in [3] F bit Forward unknown TLV bit. As defined in [3] Type Encodes how the Value field is to be interpreted. Length Specifies the length of the Value field in octets. Value Octet string of Length octets that encodes information to be interpreted as specified by the Type field. 4.1.3. Message Format and Protocol Extensibility This draft defines a general Extension mechanism to allow optional information to be carried by LDP messages to support mobility. Each of these Extensions is encoded in the TLV format. Extensions allow variable amounts of information to be carried within each LDP Message. It requires for further study. 5. IANA Considerations Choi, et al. Expires October 2001 [Page 26] Internet Draft Draft-choi-mobileip-ldpext-01.txt October 2001 This draft does not create any new number spaces for IANA administration. 6. Security Considerations This document does not have any security concerns. The security requirements using this document are described in the referenced documents. 7. References [1] Bradner, S., "The Internet Standards Process -- Revision 3", BCP 9, RFC 2026, October 1996. [2] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997 [3] Andersson L., et. al, "LDP Specification", , Auguest 2000. [4] Gustafsson E., et al., "Mobile IP Regional Registration", , 13 July 2000. [7] Perkins C., "Minimal Encapsulation within IP", RFC 2004, October 1996. [8] Ren Z., et al., "Integration of Mobile IP and MPLS" , July 2000. [9] Jamoussi B., et al., "Constraint-based LSP Setup using LDP", , July 2000. [10] Awduche D. O., et al., "REVP-TE: Extensions to RSVP for LSP Tunnels", , July 2000. [11] Deering S., Editor, "ICMP Router Discovery Messages", RFC 1256, September 1991. [12] Charles Perkins, et al. "Route Optimization in Mobile IP" work in progress, , November 2000 [13] Rivest R., "The MD5 Message-Digest Algorithm", RFC 1321 April 1992. [14] Ashwood, P. "Generalized MPLS Signaling Functional Description", , October, 2000. Choi, et al. Expires October 2001 [Page 27] 8. Author's Addresses Jun Kyun Choi Information and Communications University (ICU) 58-4 Hwa Ahm Dong, Yusong, Taejon Korea 305-732 Phone: +82-42-866-6122 Email: jkchoi@icu.ac.kr Yoo Kyoung Lee Electronics and Telecommunication Research Institute (ETRI) 161 Kajung Dong Yusong, Taejon Korea 305-305 Phone: +82-42-860-6120 Email: leeyk@etri.re.kr Sun Hee Yang Electronics and Telecommunication Research Institute (ETRI) 161 Kajung Dong Yusong, Taejon Korea 305-305 Phone: +82-42-860-5231 Email: shyang@etri.re.kr Tai Won Um Information and Communications University (ICU) 58-4 Hwa Ahm Dong, Yusong, Taejon Korea 305-732 Phone: +82-42-866-6198 Email: twum@icu.ac.kr Myoung Hun Kim Information and Communications University (ICU) 58-4 Hwa Ahm Dong, Yusong, Taejon Korea 305-732 Phone: +82-42-866-6198 Email: fiaa@icu.ac.kr 9. Full Copyright Statement "Copyright (C) The Internet Society (date). All Rights Reserved. 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