MIPSHOP Working Group M. Liebsch Internet-Draft NEC Intended status: Experimental A. Muhanna Expires: August 15, 2009 Nortel O. Blume Alcatel-Lucent Bell Labs February 11, 2009 Transient Binding for Proxy Mobile IPv6 draft-ietf-mipshop-transient-bce-pmipv6-01.txt Status of this Memo This Internet-Draft is submitted to IETF in full conformance with the provisions of BCP 78 and BCP 79. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF), its areas, and its working groups. Note that other groups may also distribute working documents as Internet- Drafts. Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use Internet-Drafts as reference material or to cite them other than as "work in progress." The list of current Internet-Drafts can be accessed at http://www.ietf.org/ietf/1id-abstracts.txt. The list of Internet-Draft Shadow Directories can be accessed at http://www.ietf.org/shadow.html. This Internet-Draft will expire on August 15, 2009. Copyright Notice Copyright (c) 2009 IETF Trust and the persons identified as the document authors. All rights reserved. This document is subject to BCP 78 and the IETF Trust's Legal Provisions Relating to IETF Documents (http://trustee.ietf.org/license-info) in effect on the date of publication of this document. Please review these documents carefully, as they describe your rights and restrictions with respect to this document. Liebsch, et al. Expires August 15, 2009 [Page 1] Internet-Draft Transient Binding for Proxy Mobile IPv6 February 2009 Abstract This document specifies a mechanism which enhances Proxy Mobile IPv6 protocol signaling to support the creation of a transient binding cache entry which is used for inter-MAG handover optimization. This mechanism is applicable to the mobile node's inter-MAG handover while using a single interface or different interfaces. The handover problem space using the Proxy Mobile IPv6 base protocol is analyzed and the use of transient binding cache entries at the local mobility anchor is described. The specified extension to the Proxy Mobile IPv6 protocol ensures optimized forwarding of downlink as well as uplink packets between mobile nodes and the network infrastructure and avoids superfluous packet forwarding delay or even packet loss. Liebsch, et al. Expires August 15, 2009 [Page 2] Internet-Draft Transient Binding for Proxy Mobile IPv6 February 2009 Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4 2. Conventions and Terminology . . . . . . . . . . . . . . . . . 5 2.1. Conventions used in this document . . . . . . . . . . . . 5 2.2. Terminology and Functional Components . . . . . . . . . . 5 3. Analysis of the Problem Space . . . . . . . . . . . . . . . . 6 3.1. Handover using a single interface . . . . . . . . . . . . 6 3.2. Handover between interfaces . . . . . . . . . . . . . . . 6 3.2.1. Issues with downlink traffic . . . . . . . . . . . . . 7 3.2.2. Issues with uplink traffic . . . . . . . . . . . . . . 9 3.3. Demand for a common solution . . . . . . . . . . . . . . . 10 4. Use of Transient Binding Cache Entries . . . . . . . . . . . . 11 4.1. General Approach . . . . . . . . . . . . . . . . . . . . . 11 4.2. Impact on Binding Management . . . . . . . . . . . . . . . 13 4.3. LMA Forwarding State Diagram . . . . . . . . . . . . . . . 13 4.4. MAG operation . . . . . . . . . . . . . . . . . . . . . . 17 4.5. LMA operation . . . . . . . . . . . . . . . . . . . . . . 18 4.5.1. Initiation of a transient BCE . . . . . . . . . . . . 18 4.5.2. Activation of a transient BCE . . . . . . . . . . . . 20 4.6. MN operation . . . . . . . . . . . . . . . . . . . . . . . 21 4.7. Status values . . . . . . . . . . . . . . . . . . . . . . 21 4.8. Protocol Stability . . . . . . . . . . . . . . . . . . . . 21 5. Message Format . . . . . . . . . . . . . . . . . . . . . . . . 23 5.1. Transient Binding option . . . . . . . . . . . . . . . . . 23 6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 25 7. Security Considerations . . . . . . . . . . . . . . . . . . . 26 8. Protocol Configuration Variables . . . . . . . . . . . . . . . 27 9. Contributors . . . . . . . . . . . . . . . . . . . . . . . . . 28 10. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 29 11. References . . . . . . . . . . . . . . . . . . . . . . . . . . 30 11.1. Normative References . . . . . . . . . . . . . . . . . . . 30 11.2. Informative References . . . . . . . . . . . . . . . . . . 30 Appendix A. Example Use Cases for Transient BCE . . . . . . . . . 31 A.1. Use case for Single Radio Handover . . . . . . . . . . . . 31 A.2. Use case for Dual Radio Handover . . . . . . . . . . . . . 33 Appendix B. Change Notes for version 1 . . . . . . . . . . . . . 36 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 37 Liebsch, et al. Expires August 15, 2009 [Page 3] Internet-Draft Transient Binding for Proxy Mobile IPv6 February 2009 1. Introduction The IETF specified Proxy Mobile IPv6 (PMIPv6) [RFC5213] as protocol for network-based localized mobility management, which takes basic operation for registration, tunnel management and deregistration into account. In order to eliminate the risk of lost packets, this document specifies an extension to PMIPv6 that utilizes a new mobility option in the Proxy Binding Update (PBU) and the Proxy Binding Acknowledgement (PBA) between nMAG and LMA. According to the PMIPv6 base specification, an LMA updates a mobile node's Binding Cache Entry (BCE) and switches the forwarding tunnel after receiving a Proxy Binding Update (PBU) message from the mobile node's new MAG (nMAG). At the same time the LMA disables the forwarding entry towards the mobile node's previous MAG (pMAG). In case of an inter-technology handover, the mobile node's handover target interface must be configured according to the Router Advertisement being sent by the nMAG. Address configuration as well as possible access technology specific radio bearer setup may delay the complete set up of the mobile node's new interface before it is ready to receive or send data packets. In case the LMA prematurely forwards packets towards the mobile node's new interface, some packets may get lost or experience major packet delay. The transient BCE extension, as specified in this document, avoids such loss for MNs, which have multiple network interfaces implemented while handing over from one interface to the other and for single radio MNs, which build on available radio layer forwarding mechanisms. Additionally, this document specifies an advanced binding cache management mechanism at the LMA according to well defined transient BCE states. This mechanism ensures that forwarding states at LMAs are inline with the different handover scenarios. During a transient state, a mobile node's BCE refers to two proxy-Care-of-Address (pCoA) entries, one from the mobile node's pMAG, an other from its nMAG. A transient binding on the LMA can be controlled remotely, such as from a MAG, or by local information, such as events. This document specifies advanced binding cache control by means of a Transient Binding option, which can be used with Proxy Mobile IPv6 (PMIPv6) signaling, to support transient BCEs. Furthermore, this document specifies forwarding characteristics according to the current state of a binding to switch the forwarding tunnel at the LMA from the pMAG to the nMAG during inter-MAG handover according to the handover conditions. As a result of transient binding support, handover performance can considerably be improved to smooth an MN's handover without introducing major complexity into the system. Liebsch, et al. Expires August 15, 2009 [Page 4] Internet-Draft Transient Binding for Proxy Mobile IPv6 February 2009 2. Conventions and Terminology 2.1. 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 [RFC2119]. 2.2. Terminology and Functional Components o IF - Interface. Any network interface, which offers a mobile node wireless or wired access to the network infrastructure. In case a mobile node has multiple interfaces implemented, they are numbered (IF1, IF2, ...) o Inter-RAT handover. Handover between different radio access technologies. o Transient Binding Cache Entry. A temporary state of the mobile node Binding Cache Entry which defines the forwarding characteristics of the mobile node forwarding tunnels to the nMAG and pMAG. This transient BCE state is created when the Transient Binding option is included in the PBU and PBA as specified in this document. The LMA forwards the mobile node traffic according to current transient BCE characteristics as specified in this document. The transient BCE state is transparent to the pMAG and the usage of the Transient Binding option is restricted to signaling between nMAG and LMA. o Activation of a Transient Binding Cache Entry. Initiates leaving the transient state of a Binding Cache Entry to become active. o Active Binding Cache Entry. A valid mobile node Binding Cache Entry according to [RFC5213], which is not in transient state. Liebsch, et al. Expires August 15, 2009 [Page 5] Internet-Draft Transient Binding for Proxy Mobile IPv6 February 2009 3. Analysis of the Problem Space This section summarizes the analysis of the handover problem space for inter-technology handover as well as intra-technology handover when using the PMIPv6 protocol as in [RFC5213]. 3.1. Handover using a single interface In some active handover scenarios, it is necessary to prepare the handover target MAG prior to the completion of the link layer handover procedures. Packets sent by the LMA to the target MAG before the completion of the link layer handover procedure will be lost or need to be buffered. In some systems, the target MAG will be the recipient of uplink traffic prior to the completion of the procedure that would result in the PBU/PBA handshake. These packets cannot be forwarded to the LMA. During an intra-technology handover, some of the MN's uplink traffic may still be in transit through the pMAG. Currently and as per PMIPv6 base protocol [RFC5213], the LMA forwards the MN's uplink traffic received from a tunnel only as long as the source IP address of the MN's uplink traffic matches the IP address of the mobile node's registered Proxy-CoA in the associated BCE. As a result, packets received at the LMA from the MN's pMAG after the LMA has already switched the tunnel to point to the nMAG will be dropped. 3.2. Handover between interfaces In client based mobility protocols the handover sequence is fully controlled by the MN and the MN updates its binding and associated routing information at its mobility anchor after IP connectivity has been established on the new link. On the contrary, PMIPv6 aims to relieve the MN from the IP mobility signaling, while the mobile node still controls link configuration during a handover. This introduces a problem during an MN's handover between interfaces. According to the PMIPv6 base protocol [RFC5213], the Access Authentication and the Proxy Binding Update (PBU) are triggered in the access network by the radio attach procedure, transparently for the MN. In addition, a delay for the MN's new interface's address configuration is not considered in the handover procedure. As a consequence, the immediate update of the MN's BCE after the PBU from the MN's nMAG has been received at the LMA has impact to the performance of the MN's downlink traffic as well as its uplink traffic. Performance aspects of downlink as well as uplink traffic during a handover between interfaces are analyzed in the subsequent subsections. Liebsch, et al. Expires August 15, 2009 [Page 6] Internet-Draft Transient Binding for Proxy Mobile IPv6 February 2009 3.2.1. Issues with downlink traffic Delay of availability of an MN's network interface can be caused by certain protocol operations that the MN needs to perform to configure its new interface and these operations can take time. In order to complete the address auto-configuration on its new interface, the MN needs to send a router solicitation and awaits a router advertisement. Upon receiving a router advertisement from the new MAG, the MN can complete its address configuration and perform Duplicate Address Detection (DAD) [RFC4862] on the new interface. Only then the MN's new interface is ready to receive packets. Address configuration can take more than a second to complete. If the LMA has already switched the mobile node tunnel to point to the nMAG and started forwarding data packets for the MN to the nMAG during this time, these data packets may get delayed or lost because the MN's new interface is not yet ready to receive data. However, delaying the PBU, which is sent from the new MAG to the LMA after the MN's new interface has attached to the network, is not possible, as the new MAG retrieves configuration data for the MN from the LMA in the PBA. With host-based mobility protocols, such as Mobile IPv6 [RFC3775], MNs can easily control when a binding is updated. This is different for network-based mobility management, where hosts are not involved in IP mobility management [RFC4831] The aforementioned problem is exemplarily illustrated in Figure 1, which assumes that the HNP will be assigned under control of the LMA. Hence, the HNP option in the PBU, which is sent by the new MAG to the LMA, is set to ALL_ZERO. An MN has attached to the network with interface (IF) IF1 and receives data on this interface. When the MN's new interface IF2 comes up and is detected by the new MAG, the new MAG sends a PBU and receives a PBA from the LMA. If the LMA decides to forward data packets for the MN via the new MAG, the new MAG has to buffer these packets until address configuration of the MN's new interface has completed and the MN's new interface is ready to receive packets. While setting up IF2, the MN may not reply to address resolution signaling [RFC4861], as sent by the new MAG [A]. If the MAG's buffer overflows or the MN cannot reply to address resolution signaling for too long, data packets for the MN are dropped and the MN can experience severe packet losses during an inter-technology handover [B] until IF2 is ready to receive and send data [C]. Liebsch, et al. Expires August 15, 2009 [Page 7] Internet-Draft Transient Binding for Proxy Mobile IPv6 February 2009 +------+ +----+ +----+ +---+ | MN | |pMAG| |nMAG| |LMA| +------+ +----+ +----+ +---+ IF2 IF1 | | | | | | | | | |- - - - - - - - - Attach | | | | |---------------PBU--------------->| | | |<--------------PBA----------------| | |--------RtSol------->| | | | |<-------RtAdv--------| | | | Addr. | | | | Conf. | | | | |<--------------------|==================data============|-- | | | | | |- - - - - - - - - - - - - - - - - Attach | | | | |----------PBU-------->| | | | |<---------PBA---------| | | | |<-====data============|-- [A]?|<-----------NSol---------------------|<-====data============|-- | | | [B] ?|<-====data============|-- | | | ?|<-====data============|-- |-----------RtSol-------------------->|<-====data============|-- |<----------RtAdv---------------------| : | Addr. | | | : | Conf. | | | : | |<-----------NSol---------------------| : | |------------NAdv------------------->[C] | !|<------------------------------------|======data============|-- | | | | | | | | | | Figure 1: Issue with inter-RAT mobility. Another risk for a delay in forwarding data packets from a new MAG to the MN's IF2 can be some latency in setting up a particular access technology's radio bearer or access specific security associations after the new MAG received the MN's HNP from the LMA via the PBA signaling message. In case an access technology needs the MN's IP address or HNP to set up a radio bearer between an MN's IF2 and the network infrastructure, the responsible network component might have to wait until the nMAG has received the associated information from the LMA in the Proxy Binding Acknowledgment. Delay in forwarding packets from the nMAG to the MN's IF2 depends now on the latency in setting up the radio bearer. A similar problem can occur in case the set up of a required security Liebsch, et al. Expires August 15, 2009 [Page 8] Internet-Draft Transient Binding for Proxy Mobile IPv6 February 2009 association between the MN's IF2 and the network takes time and such set up can be performed only after the MN's IP address or HNP is available on the nMAG. 3.2.2. Issues with uplink traffic In case of an inter-technology handover between two interfaces the MN may be able to maintain connectivity on IF1 while it is completing address configuration on IF2. Such handover mechanism is called make-before-break and can avoid UL packet loss in client based Mobile IP. However, in a PMIPv6 domain the attachment of the MN on IF2 will cause the nMAG to send a PBU to the LMA which will cause the LMA to update the BCE for this mobility session of the MN. According to section 5.3.5 of the PMIPv6 base specification [RFC5213], the LMA will drop all subsequent packets being forwarded by the MN's pMAG due to the updated BCE, which refers now to the nMAG as Proxy-CoA. Thus make-before-break handover is currently not supported by PMIPv6. A further issue for uplink packets arises from differences in the time of travel between nMAG and LMA in comparison with the time of travel between pMAG and LMA. Even if the MN stops sending packets on IF1 before the PBU is sent (i.e. before it attaches IF2 to nMAG), uplink packets from pMAG may arrive at the LMA after the LMA has received the PBU from nMAG. Such situation can in particular occur when the MN's previous link has a high delay (e.g. a GSM link) and is slow compared to the handover target link. This characteristic is exemplarily illustrated in Figure 2. Liebsch, et al. Expires August 15, 2009 [Page 9] Internet-Draft Transient Binding for Proxy Mobile IPv6 February 2009 +------+ +----+ +---+ | MN | |nMAG| |LMA| +------+ +----+ +---+ IF2 IF1 | | | |\ | |BCE exists | | \ | | for pMAG |- -|- - - - \- - - - Attach | | | s\ |---------PBU----------->|BCE update | | l\ |<--------PBA------------| for nMAG | | o\ | | | | w\ | | | | l\ | | | | i\ | | | | n \ |packet dropped | | | k --->| as BCE has only | | | | entry for nMAG | | | | | | | | Figure 2: Uplink traffic issue with slow links. 3.3. Demand for a common solution To reduce the risk of packet loss, some settings on an MN could be chosen appropriately to speed up the process of network interface configuration. Also tuning some network parameters, such as increasing the buffer capacity on MAG components, could improve the handover performance. However, some network characteristics, such as access link delay or bearer setup latency, cannot be easily fine tuned to suit a particular handover scenario. Thus, a common solution which dynamically controls and enhances this handover complexity using a simple extension to the PMIPv6 base protocol is extremely preferred. This document specifies transient BCEs as an extension to the PMIPv6 protocol. Set up and configuration of a transient BCE can be performed by means of standard PMIPv6 signaling messages between the MAG and the LMA component using a new Transient Binding mobility option. The transient BCE mechanism supports three clearly distinguished sequences of transient states to suit various handover scenarios and to improve handover performance for both, inter- and intra-technology handover. As a result of using transient BCEs, excessive packet buffering at the target MAG during the MN's handover process is not necessary and packet losses and major jitter can be avoided. Liebsch, et al. Expires August 15, 2009 [Page 10] Internet-Draft Transient Binding for Proxy Mobile IPv6 February 2009 4. Use of Transient Binding Cache Entries 4.1. General Approach The use of transient BCE during an MN's handover (HO) enables greater control on the forwarding of uplink (Ul) and downlink (Dl) traffic to harmonize handover performance characteristics with the capabilities of the handover source and target access networks. Updating of an MN's BCE at an LMA is split into different phases before and after the radio setup and IP configuration being associated with the MN's handover from a pMAG to a nMAG. The use of a transient BCE during an MN's handover splits into an initiation phase and an activation phase. Figure 3 illustrates the procedure to enter and activate a transient BCE during an MN's handover. As a result of the MN's attachment at the nMAG, the first PBU from the MN's nMAG performs configuration of a transient BCE at the LMA and the nMAG by including a Transient Binding option. The LMA enters the nMAG as a further forwarding entry to the MN's BCE without deleting the existing forwarding entry and marks the BCE state as 'transient'. After receiving the PBA, the nMAG enters the MN's data, such as the assigned HNP, into its BUL and marks the MN's binding with the LMA as 'transient', which serves as an indication to the nMAG that the transient BCE needs activation. During the transient state, the LMA accepts uplink packets from both MAGs, the pMAG and the nMAG, for forwarding. To benefit from the still available downlink path from pMAG to MN, the LMA forwards downlink packets towards the pMAG until the transient BCE gets activated. Such downlink forwarding characteristic is denoted as 'Late path switch' (L). Decision about the classification of an MN's BCE as transient can be done either by the nMAG or the LMA. Detailed mechanisms how a nMAG or an LMA finds out to use a transient BCE procedure are out of scope of this document. A transient BCE can be activated by different means, such as a timeout at the LMA, a PBU from the nMAG, which has no Transient Binding option included or a deregistration PBU from the pMAG. As soon as the MN's BCE gets activated, the LMA switches the forwarding path for downlink packets from the pMAG to the nMAG. This specification considers an optional state during the activation (A) of a transient BCE with a late path switch, which keeps the pMAG for some more time as forwarding entry in the transient BCE, solely to ensure forwarding of delayed uplink packets from the pMAG. This optional activation state has a lifetime associated and termination does not need any signaling. Whether or not to enter this optional Liebsch, et al. Expires August 15, 2009 [Page 11] Internet-Draft Transient Binding for Proxy Mobile IPv6 February 2009 activation state when a transient BCE is activated is signaled by means of flags in the Transient Binding option. +-----+ +----+ +----+ +-----+ | MN | |pMAG| |nMAG| | LMA | +-----+ +----+ +----+ +-----+ | | | | | | | |[pMAG serves | | | | MN as pCoA] | | | | |<-----------------|===============data tunnel=====|--->data | | | | [Handoff | | | Start] | | | | | | | e|-----------------------[MN Attach] | x| | | | e| | |---PBU(transient)--->|[Add nMAG to c| | | | MN's BCE, u| | |<--PBA(transient)----| enter trans- t| | | | ient state] i| | | | o|<-----Dl+Ul-------|===============data tunnel=====|--->data n|--------Ul------------------|=====data tunnel=====|--->data | | | | [Handoff/ | | | Configuration | | | Completed] | [HO Complete] | | | |--------PBU--------->|[Activate | | | | MN's BCE, | | |<-------PBA ---------| update for- | | | | warding path | | | | to nMAG] | | | | |<---------------------------|=====data tunnel=====|--->data | | | | Figure 3: General mechanism and forwarding characteristics during handover with transient BCE. The flags in the Transient Binding option allow configuration of using one out of three sequences through the transient BCE states, which are illustrated and described in Section 4.3. Details about the Transient Binding option and its use are described in Section 4.4 and Section 4.5. Section 4.2 describes the required extension to an LMA's binding cache to support transient BCE operation. Liebsch, et al. Expires August 15, 2009 [Page 12] Internet-Draft Transient Binding for Proxy Mobile IPv6 February 2009 4.2. Impact on Binding Management The use of a transient BCE requires temporary maintenance of two forwarding entries in the MN's BCE at the LMA, one referring to the MN's pMAG, the other referring to its nMAG. Forwarding entries are represented according to [RFC5213] and comprise the interface identifier of the associated tunnel interface towards each MAG, as well as the associated access technology information. Each forwarding entry is assigned a forwarding rule to admit and control forwarding of uplink and downlink traffic to and from the associated MAG. Hence, according to this specification, a forwarding entry can have either a rule that allows only forwarding of uplink traffic from the associated MAG, or a rule that allows bidirectional forwarding from and to the associated MAG. At any time, only one of the two forwarding entries can have a bi-directional forwarding rule. The interface identifier and access technology type info can be taken from the PBU received at the LMA and linked to each forwarding entry accordingly. MAGs should maintain the status of an MN's binding and the lifetime associated with a transient BCE at the LMA in their binding update list. This is in particular important in case a new MAG needs to explicitly activate a binding after the associated MN's new interface has proven to be ready to handle IP traffic. 4.3. LMA Forwarding State Diagram The current specification of transient BCEs covers three clearly defined transient BCE states at an LMA during an MN's handover. Each state implies a dedicated characteristic regarding forwarding entries, in which forwarding rules for uplink traffic are maintained separately from downlink traffic. This section explains how the forwarding state sequentially changes during the optimized handoff. To suit different handover scenarios, three different sequences through the forwarding states can be entered and signaled by means of flags in the Transient Binding option. Figure 4 depicts the possible cases, their sequence of forwarding states and the triggers for the transitions. Two example use cases are described in detail in Appendix A to illustrate which sequence through the forwarding states suits a particular handover. According to this specification, each BCE has a state associated, which can be either 'Active' or any of the specified transient states 'Transient-L', 'Transient-LA' or 'Transient-A'. In case a BCE is in state 'Active', the information in a BCE and associated forwarding conforms to [RFC5213]. Which sequence through the transient states should be entered will be signaled in the Transient Binding option by means of two flags (L- and A-Flag, see Section 5 for details). Liebsch, et al. Expires August 15, 2009 [Page 13] Internet-Draft Transient Binding for Proxy Mobile IPv6 February 2009 Any of the transient states implies that the transient BCE has two forwarding entries, which are denoted as pMAG and nMAG in the forwarding state diagram. The diagram includes information about the forwarding rule along with each forwarding entry. This rule indicates whether a forwarding entry is meant to perform forwarding only for Uplink (Ul) traffic or to perform bi-directional forwarding for Uplink (Ul) and Downlink (Dl) traffic. State transitions can be triggered as a result of processing a received PBU or by a local timeout event on the LMA. Presence of a Transient Binding option in a PBU is indicated by 'Topt' as argument to a PBU or PBA respectively. As a further argument to a PBU message, the source of the message is indicated, which can be either the MN's nMAG or its pMAG. The values of the Transient Binding option flags 'L' and 'A' are indicated in brackets as argument to the Topt. Figure 4 illustrates the three possible transitions between an active BCE and a transient BCE based on the assumption that the nMAG controls the use of a transient BCE during an MN's handover by means of including a Transient Binding option in the PBU message. The same diagram applies for the case that the LMA takes the decision to use any of the specified transient BCE handover sequences. The LMA indicates the use of a transient BCE by means of including the Transient Binding option in the PBA it sends back to the MN's nMAG. As the forwarding characteristics according to the transient BCE states are independent of whether a MAG or an LMA takes the decision to use a transient BCE during a handover, LMA-initiated use and indication of a transient BCE is not explicitly covered in the diagram. The diagram refers to two timeout events. TIMEOUT_1 is set according to the Lifetime value in a Transient Binding option (see Section 5 for the format of the Transient Binding option), whereas TIMEOUT_2 is set to ACTIVATIONDELAY (see Section 8 for the default value). The three possible sequences of a transient BCE handover are reflected in the diagram below. The first of these is going through state Transient-L to support a late path switch. The use of entering this sequence is signaled by having the L-Flag of the Transient Binding option set to 1 and the A-Flag set to 0. In this state, the LMA continues forwarding downlink packets to the pMAG, whereas uplink packets are accepted and forwarded from both, the pMAG and the nMAG. After the Transient-L state has been left either due to the reception of a PBU without Transient Binding option included from the nMAG, a TIMEOUT_1 event or the reception of a deregistration PBU from the pMAG, the BCE state changes to active. Liebsch, et al. Expires August 15, 2009 [Page 14] Internet-Draft Transient Binding for Proxy Mobile IPv6 February 2009 The second sequence implies entering the state Transient-LA when the LMA receives a PBU with a Transient Binding option having the L-Flag and the A-Flag set to 1. Forwarding characteristics in this state are the same as for the Transient-L state. After the Transient-LA state has been left due to the reception of a PBU without Transient Binding option included from the nMAG or a TIMEOUT_1 event, the BCE state changes to an activating state Transient-A. In the Transient-A state, the LMA performs a downlink forwarding path switch from the pMAG to the nMAG, whereas uplink packets are still accepted and forwarded from both, the pMAG and the nMAG. The Transient-A state is terminated by a TIMEOUT_2 event and results in turning the BCE state to active. In case the LMA receives a deregistration PBU from the pMAG while the associated MN's BCE is in state Transient-LA, the BCE is turned to active immediately without entering state Transient-A before. The third sequence does not imply a late path switch, but ensures acceptance and forwarding of uplink packets from both MAGs, the pMAG and the nMAG, during the transient binding phase. In case the LMA receives a PBU with a Transient Binding option having the L-Flag set to 0 and the A-Flag set to 1 for an active BCE, the LMA turns the BCE state to Transient-A. The BCE is turned to active when a TIMEOUT_2 event occurs or a deregistration PBU from the pMAG has been received before. Liebsch, et al. Expires August 15, 2009 [Page 15] Internet-Draft Transient Binding for Proxy Mobile IPv6 February 2009 +----------+ | No Entry | +----------+ | | PBU(pMAG) V +----------------+ PBU(nMAG) | Active | +------------------------------------| | | | pMAG [Dl,Ul] | | +----------------+ | PBU(nMAG, Topt[L=1,A=0]) | | | | +--------------------------+ | | | | | |PBU(nMAG, | | PBU(nMAG, Topt[L=1,A=1])| |Topt[L=0,A=1]) | V V | | +--------------+ +--------------+ | | | Transient-L | | Transient-LA | | | | | | | | | | pMAG [Dl,Ul] | +---| pMAG [Dl,Ul] | | | | nMAG [Ul] | | | nMAG [Ul] | | | +--------------+ | +--------------+ | | | | | | | | PBU(pMAG, | | | | | lifetime=0)| PBU(nMAG)|TIMEOUT_1 | | | | | | | | | V V | | | +--------------+ | | | | Transient-A | | PBU(nMAG)|TIMEOUT_1 | | | | | | | nMAG [Dl,Ul] | | |PBU(pMAG, | | pMAG [Ul] | | | lifetime=0) | +--------------+ | | | | | | | PBU(pMAG, | | | | lifetime=0) | TIMEOUT_2 | | | V | | | +--------------+ | | +--------->| Active | | +------------------------>| | +------------------------------------>| nMAG [Dl,Ul] | +--------------+ Figure 4: Possible transient forwarding states during a handover. Liebsch, et al. Expires August 15, 2009 [Page 16] Internet-Draft Transient Binding for Proxy Mobile IPv6 February 2009 4.4. MAG operation In case of a handover, the MN's nMAG may decide to control the MN's handover at the LMA according to any of the three possible sequences through the transient BCE forwarding states as described in this specification. In such case, the nMAG includes the Transient Binding option in the PBU message it sends to the MN's LMA. If the nMAG wants the LMA to perform a late path switch, it sets the L-flag of the Transient Binding option to 1. If the nMAG wants the LMA to enter a temporary activation state after the activation of a transient BCE has been initiated, the nMAG sets the A-flag along with the L-flag in the Transient Binding option to 1. Otherwise, the nMAG may set the L-flag to 1 and the A-flag to 0 to perform a handover without entering the activation state Transient-A. In case the nMAG does not control the LMA to perform a late path switch, but wants to ensure temporary forwarding of uplink traffic at the LMA from the pMAG and from the nMAG, it may set the L-flag to 0 and the A-flag to 1. The nMAG SHOULD NOT use the Transient Binding option with both flags set to 0. In any case where the nMAG includes the Transient Binding option in the PBU with the L-Flag set to 1, it MUST set the Lifetime field of the Transient Binding option to a value larger than 0 to propose a maximum lifetime of the transient BCE. The chosen lifetime value for the Transient Binding option SHOULD be smaller than the chosen lifetime value for the PBU registration. If the L-Flag of the Transient Binding option is set to 0, the timer SHALL be set to 0. Other fields and options of the PBU are used according to [RFC5213] In case the nMAG does not include a Transient Binding option but the LMA decides to perform a handover according to the transient BCE procedure, the nMAG may receive a Transient Binding option along with the PBA from the LMA as a result of the PBU it sent to the LMA. In case the nMAG receives a PBA with a Transient Binding option, it SHOULD link the information about the transient BCE sequence and the associated transient BCE lifetime with the MN's entry in the BUL. Only in case the L-flag of the Transient Binding option is set to 1, the nMAG MAY activate the MNs transient BCE before expiration of the transient BCE lifetime by means of sending an updating PBU to the LMA without including a Transient Binding option. All fields of the PBU MAY be set according to the procedure for binding lifetime extension described in section 5.3.3 of [RFC5213]. In case the lifetime of a transient BCE expires or the LMA approves the activation of a transient BCE as a result of a PBU sent by the nMAG, the nMAG MUST delete all information associated with a transient BCE from the MN's BUL entry. Liebsch, et al. Expires August 15, 2009 [Page 17] Internet-Draft Transient Binding for Proxy Mobile IPv6 February 2009 In case where the nMAG decides to include a Transient Binding option into the PBU, only one instance of the Transient Binding option per PBU is allowed. A MAG, which serves the MN current pCoA while the LMA already has an active binding for the MN pointing to this MAG, SHALL NOT include a Transient Binding option in any subsequent PBU being associated with the MN's registration. 4.5. LMA operation 4.5.1. Initiation of a transient BCE In case the LMA receives a handover PBU from a MN's nMAG which does not include a Transient Binding option and the associated MN's BCE is active and not in transient state, the LMA MAY take the decision to use a transient BCE and inform the nMAG about the transient BCE characteristics by including a Transient Binding option in the PBA. In such case, the LMA should know about the nMAG's capability to support the Transient Binding option and the associated procedure. The configuration of the MN's transient BCE is done according to the description in this section and the selected transient state. Otherwise, the LMA processes the PBU according to the PMIPv6 protocol [RFC5213] and performs normal update of the MN's BCE. In case the PBU from the nMAG has a Transient Binding option included, the LMA must identify the sequence of transient BCE states according to the L-flag and the A-flag settings received in the Transient Binding option. In case the LMA finds the L-flag set to 1, but the A-flag set to 0, the LMA configures the MN's transient BCE and the forwarding rules according to state Transient-L. As a result, the LMA performs a late path switch and forwards downlink packets for the MN towards the MN's pMAG, whereas uplink packets being forwarded from both Proxy-CoAs, the MN's pMAG as well as from its nMAG, will be routed by the LMA. The LMA sets the lifetime of the transient BCE according to the lifetime indicated by the nMAG in the Transient Binding option's lifetime field or may decide to reduce the lifetime according to its policy. If the lifetime value in the Transient Binding option exceeds the lifetime value associated with the PBU message, the LMA MUST reduce the lifetime of the transient BCE to a value smaller than the registration lifetime value in the PBU message. In case of a successful transient BCE registration, the LMA sends a PBA with a Transient Binding option back to the nMAG. The L-flag and the A-flag of the Transient Binding option included in the PBA are set according to the values received in the PBU, whereas the lifetime field is set to the value finally chosen by the LMA. In case the LMA finds the L-flag and the A-flag set to 1, the LMA Liebsch, et al. Expires August 15, 2009 [Page 18] Internet-Draft Transient Binding for Proxy Mobile IPv6 February 2009 configures the MN's transient BCE and the forwarding rules according to state Transient-LA. As a result, the LMA performs a late path switch and forwards downlink packets for the MN towards the MN's pMAG, whereas uplink packets being forwarded from both Proxy-CoAs, the MN's pMAG as well as from its nMAG, will be routed by the LMA. In addition, the LMA marks the transient BCE to enter a temporary activation phase in state Transient-A after the LMA received an indication to activate a transient BCE. The LMA sets the lifetime of the transient BCE according to the lifetime indicated by the nMAG in the Transient Binding option's lifetime field or may decide to reduce the lifetime. If the lifetime value in the Transient Binding option exceeds the lifetime value associated with the PBU message, the LMA MUST reduce the lifetime of the transient BCE to a value smaller than the registration lifetime value in the PBU message. In case of a successful transient BCE registration, the LMA sends a PBA with a Transient Binding option back to the nMAG. The L-flag and the A-flag of the Transient Binding option included in the PBA are set according to the values received in the PBU, whereas the lifetime field is set to the value finally chosen by the LMA. In case the LMA finds the L-flag of the received Transient Binding option set to 0 but the A-flag set to 1, the LMA configures the MN's transient BCE and the forwarding rules according to state Transient-A to support early path switching and enters state Transient-A. As a result, the LMA forwards downlink packets for the MN towards the MN's nMAG, whereas uplink packets being forwarded from both Proxy-CoAs, the MN's pMAG as well as from its nMAG, will be routed by the LMA. The LMA sends a PBA with a Transient Binding option included back to the nMAG. The L-flag and the A-flag of the Transient Binding option included in the PBA are set according to the values received in the PBU, whereas the lifetime field is set to 0 by the LMA. In any case where the LMA finds the L-flag of the received Transient Binding option set to 1, but the lifetime field of the Transient Binding option is set to 0, the LMA MUST ignore the Transient Binding option and process the PBU according to [RFC5213]. After the PBU has been processed successfully, the LMA sends back a PBA with the status field set to PBU_ACCEPTED_TB_IGNORED. In case the LMA finds the L-flag as well as the A-flag of the received Transient Binding option set to 0, the LMA MUST ignore the Transient Binding option and process the PBU according to the PMIPv6 base protocol [RFC5213]. After the PBU has been processed successfully, the LMA sends back a PBA with the status field set to PBU_ACCEPTED_TB_IGNORED. In case the LMA receives a PBU with a Transient Binding option included from a MAG which serves already as pCoA to the associated Liebsch, et al. Expires August 15, 2009 [Page 19] Internet-Draft Transient Binding for Proxy Mobile IPv6 February 2009 MN, the LMA MUST ignore the Transient Binding option and process the PBU according to [RFC5213]. After the PBU has been processed successfully, the LMA sends back a PBA with the status field set to PBU_ACCEPTED_TB_IGNORED. 4.5.2. Activation of a transient BCE When the LMA receives a PBU from an MN's nMAG which has no Transient Binding option included, the LMA should check whether the MN's BCE is in any of the specified transient states. If the MN's BCE is not transient, the LMA processes the PBU and updates the MN's BCE according to the PMIPv6 protocol [RFC5213]. When the LMA receives a PBU from the MN's pMAG and the MN's BCE is not transient, the LMA performs protocol operation and an update of the MN's BCE according to the PMIPv6 base protocol [RFC5213]. When the LMA receives a PBU from the MN's nMAG which has no Transient Binding option included but the MN's BCE is in a transient state or the LMA receives a local event trigger due to expiration of MN's transient BCE, the LMA should check whether the forwarding rules for the associated MN are set to route the MN's downlink traffic to the MN's pMAG. If the forwarding entry for downlink packets refers to the MN's pMAG, the LMA must update the forwarding information to forward downlink packets towards the MN's nMAG. After the forwarding path has been switched, the LMA must update the MN's BCE accordingly. If the transient BCE indicates that the LMA must consider an activation phase after leaving a transient BCE has been initiated, the LMA must keep both forwarding entries for the pMAG and the nMAG for uplink packets and perform forwarding of packets it receives from both Proxy-CoAs. If the activation phase can be omitted, the LMA sets the state of the MN's BCE to active and deletes any forwarding entry referring to the MN's pMAG. The LMA must delete any scheduled timeout event for the MN which are associated with a transient BCE. When the LMA receives a deregistration PBU from the MN's pMAG, which has the registration lifetime set to 0 and the MN's BCE is in transient state, the LMA must update the forwarding rules for the MN and switch the downlink traffic path from the pMAG to the nMAG. Furthermore, the LMA sets the state of the MN's BCE to active and removes any forwarding entry towards the pMAG from the MN's BCE, irrespective whether or not the transient BCE was configured to enter a temporary activation state. When the LMA receives a local event trigger due to expiration of a timer which has been set to ACTIVATIONDELAY and scheduled to terminate the activation state of an MN's transient BCE, the LMA sets the state of the MN's BCE to active and removes any forwarding entry Liebsch, et al. Expires August 15, 2009 [Page 20] Internet-Draft Transient Binding for Proxy Mobile IPv6 February 2009 towards the pMAG from the MN's BCE. 4.6. MN operation Operation of MN to support handover and choosing appropriate settings for a transient BCE is out of scope of this specification. The same applies to mechanisms for the nMAG to detect the possibility to use transient BCEs, e.g. the simultaneous use of two interfaces during the handover. One solution is that the MN signals its intent for transient bindings to the MAG, either using radio layer protocols between MN and MAG or with dedicated IP-based signaling. This document focuses on extensions required in the MAG and in the LMA. Other documents address issues of the MN operation with PMIPv6, such as [I-D.premec-netlmm-intertech-handover] and [I-D.sarikaya-netlmm-itho]. It is further out of the scope of this document how the MN can perform address configuration of the same IP address for two simultaneously attached interfaces. 4.7. Status values This section specifies the following PBA status value for transient binding cache entry support. This status value must be smaller than 128 and adds to the set of status values specified in [RFC5213]. o PBU_ACCEPTED_TB_IGNORED: [IANA] The LMA has processed and accepted the PBU, but the attached Transient Binding option has been ignored. 4.8. Protocol Stability The specification and use of transient BCEs ensures that correct PMIPv6 operation according to [RFC5213] will not be broken in any case. Such cases include loss of signaling information and incompatibility between a nMAG and an LMA in case one or the other side does not support the transient BCE option. The following list summarizes such cases and describes how the PMIPv6 protocol operation resolves from incompatibility or loss of a signaling message. o LMA does not support transient BCEs: In case the nMAG sends a PBU with a Transient Binding option included to an LMA but the LMA does not support transient BCEs, the LMA ignores the unknown option [RFC3775] and processes the PBU according to [RFC5213]. o nMAG does not support transient BCEs: In case the LMA takes the decision to perform a handover according to any of the specified Liebsch, et al. Expires August 15, 2009 [Page 21] Internet-Draft Transient Binding for Proxy Mobile IPv6 February 2009 transient BCE sequences and includes a Transient Binding option in the PBA, the receiving nMAG ignores the unknown option [RFC3775] and processes the PBA according to [RFC5213]. As the LMA does not get any further indication or feedback about the incompatibility at the nMAG, the LMA enters the selected transient state, which will be terminated at the latest after (TIMEOUT_1 + ACTIVATIONDELAY) seconds. During this period, the nMAG performs according to the PMIPv6 specification [RFC5213], whereas the LMA will accept all uplink packets for the MN from the pMAG as well as from the nMAG according to the transient BCE specification. It is transparent to the nMAG if the LMA forwards downlink packets to the pMAG during the transient BCE phase, thus no protocol conflict occurs due to the different states on the nMAG and the LMA. o Loss of Transient Binding option: As the Transient Binding option is included in the PBU and PBA, recovery from signaling packet loss is according to the PMIPv6 protocol operation and associated re-transmission mechanisms [RFC5213]. o Missing PBU to activate a transient BCE: According to this specification, a lifetime for TIMEOUT_1 is signaled in the Transient Binding option and the activation of a transient state is initiated at the latest after the timer TIMEOUT_1 has elapsed. Thus it is not possible that due to the loss of signaling or due to a failure of the nMAG to activate a transient BCE the transient state may not get terminated, i.e. stable operation of the PMIPv6 protocol [RFC5213] has reliably recovered. Liebsch, et al. Expires August 15, 2009 [Page 22] Internet-Draft Transient Binding for Proxy Mobile IPv6 February 2009 5. Message Format 5.1. Transient Binding option This section describes the format of the Transient Binding option, which can be present in a Proxy Binding Update message and a Proxy Binding Acknowledge message. The use of this Mobility Header option is optional. The Transient Binding option can be included in a PBU message which is sent by a MN's nMAG as a result of a handover. In such case, the nMAG controls the transient BCE on the LMA by means of setting the L-flag and the A-flag accordingly. Alternatively, the LMA may attach the Transient Binding option in a PBA for two reasons. Either it replies to a received PBU with an attached Transient Binding option to approve or correct the transient BCE lifetime, or it notifies the nMAG about its decision to enter a transient BCE without having received a Transient Binding option from the nMAG in the associated PBU beforehand. The format of the Transient Binding option 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 | Length | Reserved |A|L| Lifetime | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Figure 5 Type: Identifies the Transient Binding option. To be assigned by IANA. Length: 8-bit unsigned integer indicating the length of the option in octets, excluding the Type and the Length fields. This field MUST be set to 2. L-Flag: Indicates that the LMA applies late path switch according to the transient BCE state. If the L-flag is set to 1, the LMA continues to forward downlink packets towards the pMAG. In case the L-flag is set to 0, the LMA will switch the downlink path immediately to the nMAG after the PBU has been processed. A-Flag: Indicates that the LMA must enter the Transient-A state Liebsch, et al. Expires August 15, 2009 [Page 23] Internet-Draft Transient Binding for Proxy Mobile IPv6 February 2009 before entering Active state when set to 1. The LMA omits the Transient-A state during activation of a transient BCE state when set to 0. Lifetime: Lifetime of a Transient-L state in multiple of 100ms. In case the L-Flag of the Transient Binding option is set to 1, the Lifetime field MUST be set to a non-zero value. Liebsch, et al. Expires August 15, 2009 [Page 24] Internet-Draft Transient Binding for Proxy Mobile IPv6 February 2009 6. IANA Considerations This specification adds a new Mobility Header option, the Transient Binding option. The Transient Binding option is described in Section Section 5.1. The Type value for this option needs to be assigned from the same numbering space as allocated for the other mobility options, as defined in [RFC3775]. This specification also adds one status code value to the Proxy Binding Acknowledge message, the PBU_ACCEPTED_TB_IGNORED status code. The PBU_ACCEPTED_TB_IGNORED status code is described in section Section 4.7. Its value must be assigned from the same number space used for the Mobile IPv6 Binding Acknowledgement status values, as defined in [RFC3775], and must be smaller 128. Liebsch, et al. Expires August 15, 2009 [Page 25] Internet-Draft Transient Binding for Proxy Mobile IPv6 February 2009 7. Security Considerations Signaling between MAGs and LMAs as well as information carried by PBU and PBA messages is protected and authenticated according to the mechanisms described in [RFC5213]. In case MAGs or LMAs make use of a further protocol interface to an external component, such as for support of transient BCE control, the associated protocol must be protected and information must be authenticated. Liebsch, et al. Expires August 15, 2009 [Page 26] Internet-Draft Transient Binding for Proxy Mobile IPv6 February 2009 8. Protocol Configuration Variables LMA values: o 'ACTIVATIONDELAY' : This value is set by default to 2000 ms and can be administratively adjusted. Liebsch, et al. Expires August 15, 2009 [Page 27] Internet-Draft Transient Binding for Proxy Mobile IPv6 February 2009 9. Contributors Many thanks to Jun Awano, Suresh Krishnan, Long Le, Kent Leung, Basavaraj Patil and Rolf Sigle for contributing to this document. Liebsch, et al. Expires August 15, 2009 [Page 28] Internet-Draft Transient Binding for Proxy Mobile IPv6 February 2009 10. Acknowledgments The authors would like to thank Telemaco Melia, Vijay Devarapalli and Ryuji Wakikawa for their comments to improve this specification. Liebsch, et al. Expires August 15, 2009 [Page 29] Internet-Draft Transient Binding for Proxy Mobile IPv6 February 2009 11. References 11.1. Normative References [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997. [RFC3775] Johnson, D., Perkins, C., and J. Arkko, "Mobility Support in IPv6", RFC 3775, June 2004. [RFC4861] Narten, T., Nordmark, E., Simpson, W., and H. Soliman, "Neighbor Discovery for IP version 6 (IPv6)", RFC 4861, September 2007. [RFC4862] Thomson, S., Narten, T., and T. Jinmei, "IPv6 Stateless Address Autoconfiguration", RFC 4862, September 2007. [RFC5213] Gundavelli, S., Leung, K., Devarapalli, V., Chowdhury, K., and B. Patil, "Proxy Mobile IPv6", RFC 5213, August 2008. 11.2. Informative References [I-D.premec-netlmm-intertech-handover] Premec, D. and T. Savolainen, "Inter-technology handover in netlmm domain", draft-premec-netlmm-intertech-handover-00 (work in progress), April 2008. [I-D.sarikaya-netlmm-itho] Sarikaya, B. and F. Xia, "Proxy Mobile IPv6 Inter- Technology Handover Issue", draft-sarikaya-netlmm-itho-00 (work in progress), June 2008. [RFC4831] Kempf, J., "Goals for Network-Based Localized Mobility Management (NETLMM)", RFC 4831, April 2007. Liebsch, et al. Expires August 15, 2009 [Page 30] Internet-Draft Transient Binding for Proxy Mobile IPv6 February 2009 Appendix A. Example Use Cases for Transient BCE A.1. Use case for Single Radio Handover In some systems, PMIPv6 is supported for providing network based mobility between the Serving Gateway (i.e. MAG) and the Packet Data Network Gateway (i.e. LMA) and handover mechanisms are implemented in the access network to optimize handover for single radio mobile nodes. In such system, a well structured inter-MAG handover procedure has been developed and effectively used. In order to switch the data tunnel path between the LMA and the pMAG in a systematic way that reduces packet loss and delay, this inter-MAG handover sets up the uplink data path from the mobile node through the nMAG and to the LMA first. As soon as the uplink data path is setup, the mobile node is able to forward uplink data packets through the nMAG to the LMA. Since the downlink data path between the LMA and the nMAG is not setup at the same time of the uplink data path setup, the LMA must continue to forward downlink data packets to the pMAG. Additionally, this system utilizes a layer 2 forwarding mechanism which enables the delivery of the downlink data packets to the mobile node location while being attached to the nMAG. In order for the LMA to be able to forward the mobile node uplink data packets to the Internet, the transient BCE mechanism is used at the nMAG to send a PBU with the Transient Option to allow the LMA to create a transient BCE for the mobile node with uplink forwarding capabilities while maintaining uplink and downlink forwarding capabilities for the pCoA that is hosted at the pMAG. During the lifetime of the transient BCE, the LMA continues to accept uplink traffic from both previous and new MAG while forwarding downlink traffic to the pMAG only. While the MN is able to receive downlink traffic via the pMAG, the mechanism used in the pMAG's access network to forward downlink traffic to the current location of the mobile node in the nMAG's access network during an intra- technology handover is out of scope of this description. When the nMAG receives an indication that the inter-MAG handover process has completed, the nMAG sends another PBU without including a Transient Binding option to update the mobile node's transient BCE to a regular PMIPv6 BCE with bi-directional capabilities. This mechanism is used by the LMA as an indication to switch the tunnel to point to the nMAG, which results in a smoother handover for the MN. An example of using a transient BCE for intra-technology handover is Liebsch, et al. Expires August 15, 2009 [Page 31] Internet-Draft Transient Binding for Proxy Mobile IPv6 February 2009 illustrated in Figure 6. When the nMAG receives the indication that the MN is moving from the pMAG's access network to the nMAG's area, the nMAG sends a PBU on behalf of the MN to the MN's LMA. In this PBU, the nMAG includes the MN-ID, the HNP, and the interface ID as per PMIPv6 base protocol [RFC5213]. Furthermore, the nMAG indicates an intra-technology handover by means of the HI option and includes the Transient Binding option to indicate to the LMA that this registration should result in a transient BCE. The nMAG sets the value of the transient BCE lifetime to a value that is dependent on the deployment and operator specific [D]. After the nMAG receives an indication that the MN has completed the handover process and the data path is ready to move the tunnel completely from the pMAG to the nMAG, the nMAG SHOULD send a PBU to allow the LMA to activate the MN's transient BCE to a regular BCE and to switch the data path completely to be delivered through the new Proxy-CoA. In this case, the nMAG sends a PBU with the MN-ID, Interface ID, HNP and at the same time indicates an intra-technology handover by means of the HI option. In this PBU, the nMAG MUST NOT include the Transient Binding option, as shown in Figure 6 [E]. In the event that the nMAG receives downlink traffic destined to the MN from the LMA after sending a PBU with Transient Binding option included, the nMAG MUST deliver the downlink traffic to the MN. In this case, the nMAG SHOULD send a PBU to ensure that the transient BCE has been activated. Liebsch, et al. Expires August 15, 2009 [Page 32] Internet-Draft Transient Binding for Proxy Mobile IPv6 February 2009 +-----+ +----+ +----+ +-----+ | MN | |pMAG| |nMAG| | LMA | +-----+ +----+ +----+ +-----+ | | | bi-directional | | |<<<<<<<<======================>>>>>>>>|<--> | | | | | | | | [Handoff Event] | | | | [MN HO Event] | | | | [HO Event Acquire] | | | | | [LL Attach to | | | nMAG] | |-----PBU(transient)----->| | | | [D] | | |<-----PBA(transient)-----| | | | | | | bi-directional | | |<<<<<<<<======================>>>>>>>>|<--> | | | | | | | uplink only | | | |>>>>>>===========>>>>>>>>|--> | | | | | | [HO Complete] | | | |----------PBU----------->| | | | [E] | | |<---------PBA -----------| | |` | | | | |<<<<<<<<=========>>>>>>>>|<--> | | | | Figure 6: Transient BCE support for an intra-technology handover A.2. Use case for Dual Radio Handover During an inter-technology handover, the LMA shall on the one hand be able to accept uplink packets of the MN as soon as the MN has finalized address configuration at the new IF2 and may start using the new interface for data traffic, i.e. the PBU for the uplink shall be done before the radio setup procedure is finalized. But, to allow the MN to keep sending its data traffic on IF1 during the handover, uplink packets with the previously existing binding on IF1 shall still be accepted by the LMA until the MN detaches from pMAG with IF1 and the pMAG has deregistered the MN's attachment at the LMA by means of sending a PBU with lifetime 0. This is of particular importance as sending the registration PBU from the nMAG is transparent to the mobile node, i.e. the MN does not know when the PBU has been sent. On the other hand, switching the downlink path from the pMAG to the nMAG shall be performed at the LMA only after completion of the IP Liebsch, et al. Expires August 15, 2009 [Page 33] Internet-Draft Transient Binding for Proxy Mobile IPv6 February 2009 configuration at the MN's IF2 and after a complete setup of the access link between the MN and the nMAG. How long this takes depends on some interface specific settings on the MN as well as on the duration of the target system's radio layer protocols, which is transparent to the LMA but may be known to MAGs. Similar to the use case for single radio handover, a transient BCE can be utilized for MNs with dual radio capability. Such MNs are still able to send and receive data on the previous interface during the new address configuration. Forwarding between nMAG and pMAG is not required, but it has to be avoided that the LMA immediately starts forwarding downlink data packets to the nMAG. This is enabled by a PBU which has the Transient Binding option included, so that it is not necessary that MN and LMA synchronize the point in time for switching interfaces and activating the BCE. When the handover is finalized, the nMAG sends a second PBU without including the Transient Binding option and the LMA activates the MN's BCE. This PBU may overtake packets-on-the-fly from MN to LMA via pMAG (e.g. if the previous interface was of type GSM or UMTS with up to 150 milliseconds uplink delay). The LMA has to drop all these packets from the pMAG due to the activation of the MN's BCE. This can be avoided by entering another transient BCE state (Transient-A) during the activation phase and is characteristic for this use case. Entering the Transient-A state during activation is configured by the PBU from nMAG and terminated by the preconfigured lifetime ACTIVATIONDELAY. The use of a transient BCE for an inter-technology handover is exemplarily illustrated in Figure 7. The MN attaches to the PMIPv6 network with IF1 according to the procedure described in [RFC5213]. The MN starts receiving data packets on IF1. When the MN activates IF2 to prepare an inter-technology handover, the nMAG receives an attach indication and sends the PBU to the LMA to update the MN's point of attachment and to retrieve configuration information for the MN (e.g. HNP). The LMA is able to identify an inter-technology handover by means of processing the HI option coming along with the PBU sent by the nMAG. As in this example the nMAG includes the Transient Binding option in the PBU to control the transient BCE at the LMA, the LMA updates the MN's BCE according to the transient BCE specification described in this document and marks the state of the BCE as 'transient' [F]. As a result of the transient BCE, the LMA keeps using the previous forwarding information towards the pMAG binding as forwarding information until the transient BCE gets activated. The LMA acknowledges the PBU by means of sending a PBA to the nMAG. The nMAG has now relevant information available, such as the MN's HNP, to set Liebsch, et al. Expires August 15, 2009 [Page 34] Internet-Draft Transient Binding for Proxy Mobile IPv6 February 2009 up a radio bearer and send a Router Advertisement to the MN. While the MN's BCE at the LMA has transient characteristic, the LMA forwards uplink packets from the MN's pMAG as well as from its nMAG. The nMAG may recognize when the MN's IF2 is able to send and receive data packets and sends a new PBU to the LMA without including the Transient Binding option to activate the MN's transient BCE [G]. As a result of successful activation of the MN's transient BCE, downlink packets will be forwarded towards the MN's IF2 via the nMAG [H]. +------+ +----+ +----+ +---+ | MN | |pMAG| |nMAG| |LMA| +------+ +----+ +----+ +---+ IF2 IF1 | | | | | | | | | |- - - - - - - - - Attach | | | | |---------------PBU--------------->| | | |<--------------PBA----------------| | |--------RtSol------->| | | | |<-------RtAdv--------| | | | Addr. | | | | Conf. | | | | |<------------------->|==================data============|<---> | | | | | |- - - - - - - - - - - - - - - - - Attach | | | | |----PBU(transient)--->| | | | |<---PBA(transient)---[F] |------RAT Configuration--------------| | | |<--------------------|==================data============|<--- |-------RtSol-(optional)------------->| | |<-----------RtAdv--------------------| | Addr. | | | | Conf | | | | |------------NSol-------------------->|---------PBU-------->[G] | | | |<--------PBA----------| |<------------------------------------|========data=========[H]<--> | | | | | | | | | | | | | | | Figure 7: Late path switch with PMIPv6 transient BCEs. Liebsch, et al. Expires August 15, 2009 [Page 35] Internet-Draft Transient Binding for Proxy Mobile IPv6 February 2009 Appendix B. Change Notes for version 1 o Moved description of use cases to Appendix o Removed references to exemplary use cases in technical core part o Moved section 'Impact on Binding Management' (now 4.2) after the General Approach section (4.1) o Provide more details (originally in use cases sections) in General Approach section (4.1) to compensate the gap from shifting the use case section to the appendix o More clarifying details in the LMA Forwarding diagram section (now 4.3) o Added section 4.8 about Protocol Stability/Reliability o Added Acknowledgements section o Small editorial improvements Liebsch, et al. Expires August 15, 2009 [Page 36] Internet-Draft Transient Binding for Proxy Mobile IPv6 February 2009 Authors' Addresses Marco Liebsch NEC Laboratories Europe NEC Europe Ltd. Kurfuersten-Anlage 36 69115 Heidelberg, Germany Phone: +49 6221 4342146 Email: marco.liebsch@nw.neclab.eu Ahmad Muhanna Nortel Networks 2221 Lakeside Blvd. Richardson, TX 75082, USA Phone: +1 (972) 685-1416 Email: amuhanna@nortel.com Oliver Blume Alcatel-Lucent Deutschland AG Bell Labs Lorenzstr. 10 70435 Stuttgart, Germany Phone: +49 711 821-47177 Email: oliver.blume@alcatel-lucent.de Liebsch, et al. Expires August 15, 2009 [Page 37]