Network Working Group J. Korhonen, Ed. Internet-Draft Nokia Siemens Networks Intended status: Standards Track S. Gundavelli Expires: April 10, 2010 Cisco H. Yokota KDDI Lab X. Cui Huawei October 7, 2009 Runtime LMA Assignment Support for Proxy Mobile IPv6 draft-korhonen-netext-redirect-04.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 April 10, 2010. 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 in effect on the date of publication of this document (http://trustee.ietf.org/license-info). Please review these documents carefully, as they describe your rights and restrictions with respect to this document. Korhonen, et al. Expires April 10, 2010 [Page 1] Internet-Draft LMA Redirect Support for PMIPv6 October 2009 Abstract This document describes a redirect functionality and corresponding mobility options for Proxy Mobile IPv6. The redirect functionality allows a dynamic runtime assignment of a Local Mobility Anchor and redirecting the mobility session to the assigned Local Mobility Anchor. Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 2. Requirements and Terminology . . . . . . . . . . . . . . . . . 5 2.1. Requirements . . . . . . . . . . . . . . . . . . . . . . . 5 2.2. Terminology . . . . . . . . . . . . . . . . . . . . . . . 5 3. Proxy Mobile IPv6 Domain Assumptions . . . . . . . . . . . . . 6 4. Mobility Options . . . . . . . . . . . . . . . . . . . . . . . 7 4.1. Redirect-Capability Mobility Option . . . . . . . . . . . 7 4.2. Redirect Mobility Option . . . . . . . . . . . . . . . . . 8 5. Runtime LMA Assignment Operation . . . . . . . . . . . . . . . 10 5.1. Common Mobile Access Gateway Operation . . . . . . . . . . 10 5.2. Common Local Mobility Anchor Operation . . . . . . . . . . 10 5.3. Mobility Session Created During the Redirection . . . . . 11 5.3.1. General Operation . . . . . . . . . . . . . . . . . . 11 5.3.2. Mobile Access Gateway Considerations . . . . . . . . . 12 5.3.3. Local Mobility Anchor Considerations . . . . . . . . . 13 5.4. Mobility Session Created After the Redirection . . . . . . 14 5.4.1. General Operation . . . . . . . . . . . . . . . . . . 14 5.4.2. Mobile Access Gateway Considerations . . . . . . . . . 14 5.4.3. Local Mobility Anchor Considerations . . . . . . . . . 15 5.5. Redirection Example . . . . . . . . . . . . . . . . . . . 15 5.5.1. Redirection During the Initial PBU/PBA Exchange . . . 16 5.5.2. Redirection During Mid-session PBU/PBA Exchange . . . 17 6. Multi-Homing Considerations . . . . . . . . . . . . . . . . . 18 7. Configuration Variables . . . . . . . . . . . . . . . . . . . 19 8. Security Considerations . . . . . . . . . . . . . . . . . . . 20 9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 21 10. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 22 11. References . . . . . . . . . . . . . . . . . . . . . . . . . . 23 11.1. Normative References . . . . . . . . . . . . . . . . . . . 23 11.2. Informative References . . . . . . . . . . . . . . . . . . 23 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 24 Korhonen, et al. Expires April 10, 2010 [Page 2] Internet-Draft LMA Redirect Support for PMIPv6 October 2009 1. Introduction This document describes the Redirect-Capability and the Redirect mobility options, and the corresponding functionality for a runtime assignment of the Local Mobility Anchor (LMA) for Proxy Mobile IPv6 (PMIPv6). Hereafter the terms 'runtime assignment' and 'redirection' are used interchangeably throughout this specification. The runtime assignment takes place during a Proxy Binding Update (PBU) and a Proxy Binding Acknowledgement (PBA) messages exchange between a Mobile Access Gateway (MAG) and a LMA. The runtime assignment functionality defined in this specification can be used, for example, for load balancing purposes during the initial PBU/PBA messages exchange. However, other use cases are also possible. In case of load balancing, the runtime assignment approach is just one implementation option. MAGs and LMAs can implement other solutions that are, for example, completely transparent at PMIPv6 protocol level and do not depend on the functionality defined in this specification. The runtime assignment functionality described in this specification does not depend on information provisioned to external entities, such as the Domain Name System (DNS) or the Authentication, Authorization and Accounting (AAA) infrastructure. The trust relationship and coordination management between LMAs within a PMIPv6 domain is deployment specific and not described in this specification. There are number of reasons, why the runtime assignment is an useful addition to the PMIPv6 protocol. The following list describes some identified ones: o LMAs with multiple IP addresses: a cluster of LMAs or a blade architecture LMA may appear to the routing system as multiple LMAs with separate unicast IP addresses. A MAG can initially select any of those LMA IP addresses as the LMA Address using e.g., DNS- and AAA-based solutions. However, MAG's initial selection may be suboptimal from the LMA point of view and immediate redirection to a "proper LMA" would be needed. The LMA could use [RFC5142] based approach but that would imply unnecessary setting up of a mobility session in a "wrong LMA" with associated backend support system interactions, involve additional signaling between the MAG and the LMA, and re-establishing mobility session to the new LMA again with associated signaling. o Bypassing a load balancer: a cluster of LMAs or a blade architecture LMA may have a load balancer in front of them or integrated in one of the LMAs. The load balancer would represent multiple LMAs during the LMA discovery phase and only its IP address would be exposed to the MAG hiding possible individual LMA Korhonen, et al. Expires April 10, 2010 [Page 3] Internet-Draft LMA Redirect Support for PMIPv6 October 2009 or LMA blade IP addresses from the MAG. However, if all traffic must always go through the load balancer it becomes quickly a bottleneck. Therefore, a PMIPv6 protocol level support for bypassing the load balancer after the initial PBU/PBA exchange would greatly help scalability. Also bypassing the load balancer as soon as possible allows implementing load balancers that do not maintain any MN specific state information. o Independence from DNS: DNS-based load balancing is a common practise. However, keeping MAGs up-to-date with LMA load status using DNS is hard e.g., due caching and unpredictable zone update delays. Generally, LMAs constantly updating [RFC2136] zone's master DNS server might not feasible in a large PMIPv6 domain due to increased load on the master DNS server and additional background signaling. Furthermore, MAGs may do (LMA) destination address selection decisions that are not in-line what the DNS administrator actually wanted [RFC3484]. o Independence from AAA: AAA-based solutions have basically the same arguments as DNS-based solutions above. It is also typical that AAA-based solutions offload the initial LMA selection to the DNS infrastructure. The AAA infrastructure does not return an IP address or a Fully Qualified domain Name (FQDN) to a single LMA, rather a FQDN representing a group of LMAs. o Support for IPv6 anycast addressing [RFC4291]: the current PMIPv6 specification does not specify how the PMIPv6 protocol should treat anycast addresses assigned to mobility agents. Although [RFC4291] now allows using anycast addresses as source addresses, it does not make much sense using anycast addresses for the MAG to the LMA communication after the initial PBU/PBA exchange. For example, a blade architecture LMA may appear to the routing system as multiple LMAs with separate unicast IP addresses and with one or more "grouping" anycast addresses. Korhonen, et al. Expires April 10, 2010 [Page 4] Internet-Draft LMA Redirect Support for PMIPv6 October 2009 2. Requirements and Terminology 2.1. Requirements 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 In addition to the terminology defined in [RFC5213], the following terminology is also used: rfLMA The LMA which receives the PBU from a MAG and decides to redirect the IP mobility session to the target LMA (r2LMA). r2LMA The LMA to which a MAG was redirected to. Redirection Domain A group of LMAs that consist of at least one rfLMA and one or more r2LMAs. A rfLMA is allowed to redirect mobility sessions only to r2LMAs that belong to the same redirection domain. Korhonen, et al. Expires April 10, 2010 [Page 5] Internet-Draft LMA Redirect Support for PMIPv6 October 2009 3. Proxy Mobile IPv6 Domain Assumptions The redirection functionality has several assumptions on the PMIPv6 domain. They are discussed here as they have impact on PMIPv6 deployment. Each functional LMA, whether that is a separate LMA in a cluster or an individual blade in a chassis, participating to the redirection MUST be reachable at an unicast IP address. The rfLMA and the r2LMA MUST have a prior agreement and an established trust relationship to perform the redirection. In this case, the rfLMA and the r2LMA are said to belong to the same 'redirection domain'. The rfLMA MUST NOT redirect the mobility session to a r2LMA that is not able to accept the redirected mobility session. That is, the redirection functionality is not enabled in the r2LMA, or the r2LMA does not belong to the same redirection domain as the rfLMA, or the r2LMA is down or otherwise unreachable. How the rfLMA learns and knows of other r2LMAs in the redirection domain, is not covered by this specification. Each LMA and MAG participating to the redirection is assumed to have required Security Associations (SA) already set up in advance. Dynamic negotiation of the SAs using e.g., IKEv2 [RFC4306] MAY be supported but is out of scope of this specification. However, it should be noted that if anycast addresses are used within the PMIPv6 domain to contact the rfLMA, then manual keying of the SAs may be required [RFC4303]. The redirection functionality negotiation during the PBU/PBA exchange is stateless. The LMA MUST NOT include the Redirect mobility option in the PBA and perform the redirection, unless the MAG indicated the redirection functionality support in the corresponding PBU using the Redirection-Capability mobility option. The LMA MUST NOT include the Redirect mobility option unsolicited even if the MAG had earlier indicated support for the redirection functionality. The MAG MUST NOT conclude LMA's redirection functionality support based on the absence of the Redirect mobility option in the PBA. Korhonen, et al. Expires April 10, 2010 [Page 6] Internet-Draft LMA Redirect Support for PMIPv6 October 2009 4. Mobility Options The Redirect mobility options allow a LMA to inform a MAG of a redirection to a new LMA during a PBU/PBA exchange. MAGs and LMAs that implement the Redirect mobility option MUST support the redirection functionality during the initial PBU/PBA exchange that creates a new mobility session. MAGs and LMAs that implement the Redirect mobility option MAY support the redirection of an established mobility session. 4.1. Redirect-Capability Mobility Option A PBU message MAY contain the Redirect-Capability mobility option as an indication to a LMA that a MAG supports the redirection functionality. When this option is included, the MAG may be redirected to another LMA, and the redirected to LMA may simultaneously create a Binding Cache Entry (BCE). Hence, the MAG including this option MUST be able to support both redirection, and redirection with BCE creation. The Redirect-Capability mobility option has the alignment requirement of 4n. There can zero or one Redirect-Capability mobility option in the PBU. The format of the Redirect-Capability mobility option is shown below: 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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Option Type | Option Length |F| Reserved | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Redirect-Capability Mobility Option o Option Type: 8-bit identifier set to TBD1. o Option Length: 8-bit unsigned integer, representing the length of the Redirect-Capability mobility option in octets, excluding the Option Type and Length fields. The Option Length MUST be set to 2. o 'F' flag: This bit is set to one (1) if the MAG supports IPv4 transport. Otherwise, the bit is set to zero (0). o Reserved: This field is reserved for future use. MUST be set to zero. Korhonen, et al. Expires April 10, 2010 [Page 7] Internet-Draft LMA Redirect Support for PMIPv6 October 2009 4.2. Redirect Mobility Option The LMA MAY include the Redirect mobility option in a PBA only if the MAG indicated support for the redirection functionality and the mobility session was redirected from a LMA to another. The Redirect mobility option in the PBA MUST contain an unicast IPv6 address of the r2LMA. The Redirect mobility option in the PBA MAY contain an IPv4 address of the r2LMA. There can zero or one Redirect mobility option in the PBA. The Redirect mobility option has the alignment requirement of 4n. The format of the Redirect mobility option is shown below: 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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Option Type | Option Length |D| Reserved | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | | | IPv6 r2LMA Address | | | | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Optional IPv4 r2LMA Address | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Redirect Mobility Option o Option Type: 8-bit identifier set to TBD2. o Option Length: 8-bit unsigned integer, representing the length of the Redirect mobility option in octets, excluding the Option Type and Length fields. If the IPv4 LMA Address is included in the option, the Option Length MUST be set to 22. Otherwise, the Option Length MUST be set to 18. o 'D' flag: This bit is set to one (1) if the mobility session (and the corresponding Binding Cache Entry) is already created in the r2LMA. Otherwise, the bit is set to zero (0). o Reserved: This field is reserved for future use. MUST be set to zero. o IPv6 r2LMA Address: the unicast IPv6 address of the r2LMA. Korhonen, et al. Expires April 10, 2010 [Page 8] Internet-Draft LMA Redirect Support for PMIPv6 October 2009 o Optional IPv4 r2LMA Address: the IPv4 address of the r2LMA. This value is present if the r2LMA IPv4 address is available. Korhonen, et al. Expires April 10, 2010 [Page 9] Internet-Draft LMA Redirect Support for PMIPv6 October 2009 5. Runtime LMA Assignment Operation 5.1. Common Mobile Access Gateway Operation The base PMIPv6 protocol [RFC5213] operation is such that a MAG sends a PBU to an LMA which results in a BCE being created at the LMA and a PBA sent back (from the LMA) to the MAG, which in turn creates an entry in the Binding Update List (BUL). The semantics of the base protocol operation are extended with the redirection feature by having the rfLMA forward the PBU sent by a MAG to the r2LMA (which creates the BCE) and the PBA which is routed back to the sending MAG through rfLMA, causing the MAG to create a BUL which points to r2LMA. The semantics in the case where the rfLMA does not forward the PBU but instead returns a PBA to the MAG which includes the Redirect Mobility option which has the address of the r2LMA are also extended from the base protocol operation. Backwards compatibility is maintained in a deployment wherein some MAGs may have the ability to support redirection while others do not. This is accomplished by the use of the Redirect-Capability Mobility Option being included in the PBU sent by the MAG. An LMA which has the capability to redirect a MAG to a target r2LMA on receiving a PBU from a legacy MAG can only respond with a PBA which does not include any r2LMA address. When the redirection functionality is enabled, then the MAG MAY include the Redirect-Capability mobility option in any PBU. The Redirect-Capability mobility option in the PBU is also an indication to a LMA that the MAG supports the redirection functionality and is prepared to be redirected. The redirection concerns always one mobility session at time. If the MAG receives a PBA that contains the Redirect mobility option without first including the Redirect-Capability mobility option in the corresponding PBU, then the MAG MUST treat the PBA as if the binding update failed and log the event. 5.2. Common Local Mobility Anchor Operation The text in the following section refers to a 'LMA' when it means the combination of the rfLMA and the r2LMA i.e., the entity where redirection is possible. When the text points to a specific LMA role during the redirection, it uses either the 'rfLMA' or the 'r2LMA'. If the redirection functionality is enabled in the LMA but the redirection is not going to take place for a reason or other, and the rfLMA is not willing to serve (or capable of) as a normal RFC 5213 LMA for the MAG, then the rfLMA MUST reject the PBU and send back a Korhonen, et al. Expires April 10, 2010 [Page 10] Internet-Draft LMA Redirect Support for PMIPv6 October 2009 PBA with Status Value set to NOT_LMA_FOR_THIS_MAG error code. Otherwise, the rfLMA MUST act as a normal RFC 5213 defined LMA for the MAG. The rfLMA MUST only redirect the MAG to a new r2LMA that it knows the MAG has a SA with or the MAG and the r2LMA are able to create it dynamically. The rfLMA MUST NOT redirect the MAG to a r2LMA that the rfLMA and the r2LMA do not have a prior redirection agreement and an established trust relationship for the redirection. These SA related knowledge issues and trust relationships are deployment specific in a PMIPv6 domain and in a redirection domain, and out of scope of this specification. Possible context transfer and other coordination management between the rfLMA and the r2LMA, are again deployment specific for LMAs in a redirection domain. The rfLMA MUST NOT redirect a MAG using IPv6 transport to a new r2LMA using IPv4 transport, if the MAG does not indicate support for IPv4 in the Redirect-Capability mobility option, as there is no guarantee that the MAG supports switching from IPv6 transport to IPv4 transport. The same also applies for redirecting a MAG using IPv4 transport to a r2LMA supporting only IPv6 transport. As a result of a successful redirection, the PBA MUST contain the Redirect mobility option with a valid r2LMA Address, the 'D' flag reflecting the r2LMA status, and the PBA Status Value indicating either success or redirection. In general the r2LMA may be a normal RFC 5213 LMA without any redirection functionality. The r2LMA MAY also include rfLMA functionality in which case the consideration described in the following sections for the rfLMA apply. If the redirection functionality is implemented but not enabled in a LMA, then the LMA MUST ignore the Redirect-Capability mobility option received in PBUs and act as a LMA defined in RFC 5213. 5.3. Mobility Session Created During the Redirection 5.3.1. General Operation During the redirection the PBA is returned from the LMA Address where the PBU was sent to i.e., from the rfLMA. After the redirection all PMIPv6 communication continues directly between the MAG and the r2LMA. The overall redirection flow sequence is shown in Figure 1. Korhonen, et al. Expires April 10, 2010 [Page 11] Internet-Draft LMA Redirect Support for PMIPv6 October 2009 MAG rfLMA r2LMA | | | 1) |--PBU-->| ~ ~ ~ | (redirection takes place, BCE gets created in 2) |<--PBA--| ~ ~ ~ | r2LMA, PBA contains r2LMA information and | | | 'D' flag is set to 1 3) |<=====data======>| | | | 4) |-------PBU------>| (lifetime extension, 5) |<------PBA-------| de-registration, etc.) | | | Figure 1: Runtime LMA assignment from rfLMA to r2LMA and setting up a mobility session in the r2LMA within a redirection domain The assumption in the signaling flow step 1) shown in Figure 1 is that the mobility session gets created in the r2LMA, although the rfLMA is responsible for interfacing with the MAG. The interaction between the rfLMA and the r2LMA in the redirection domain is not defined in this specification. There are several possible solutions for the rfLMA and the r2LMA interaction depending on e.g. the collocation properties of the rfLMA and the r2LMA, and whether the rfLMA and the r2LMA implement an interface that is interoperable among multiple LMA vendors. One potential example solution is discussed in Section 5.5. 5.3.2. Mobile Access Gateway Considerations In addition to MAG operations described in Section 5.1, the following considerations has to taken into account during the redirection. If the MAG receives a PBA that contains the Redirect mobility option with the 'D' flag set to one (1) and the MAG had included the Redirect-Capability mobility option in the corresponding PBU, then the MAG MUST perform the following steps in addition to the normal RFC 5213 PBA processing: o Check if there is a SA between the MAG and the r2LMA. If this check fails, then the MAG MUST treat the PBA as if the binding update failed and log the event. This situation should not happen and is an indication of incorrectly configured or malfunctioning redirection domain. o If there was no SA between the MAG and the r2LMA and the above bullet described PBA handling was done, then the MAG MAY still resend the PBU to the same rfLMA without including the Redirect- Capability mobility option. However, the MAG SHOULD choose another rfLMA to contact, if just possible. Korhonen, et al. Expires April 10, 2010 [Page 12] Internet-Draft LMA Redirect Support for PMIPv6 October 2009 If the redirection was successful, the MAG updates the BUL to correspond the r2LMA Address included in the received Redirect mobility option. There is no need to resend any PBUs to the r2LMA after a successful redirection. The mobility session has already been established in the r2LMA as indicated by the 'D' flag with value one (1) in the Redirection mobility option. The MAG MUST send subsequent binding refreshing PBUs and user traffic to the new r2LMA Address. If the MAG includes the Redirect-Capability mobility option in subsequent PBUs, the LMA MAY redirect the MAG again. For the subsequent mid-session redirections it is assumed that the r2LMA also has the rfLMA functionality. [ED: discuss the setting of the Handoff Indicator option value in this case and what happens if the HNP/ IPv4-HoA changes.] 5.3.3. Local Mobility Anchor Considerations If the redirection functionality is enabled in the LMA and the received PBU contains the Redirect-Capability mobility option, then the rfLMA MAY redirect the MAG to a new r2LMA. In the case of redirection, the PBA returned to the MAG MUST always include the unicast IPv6 address of the r2LMA in the Redirect mobility option with the 'D' flag set to one (1) and the Status Value set to a value indicating success. If the r2LMA has IPv4 support enabled, then the PBA returned to the MAG SHOULD include the IPv4 address of the r2LMA in the Redirect mobility option. If the rfLMA did not redirect the MAG to a new r2LMA or the redirection failed, then the PBA MUST NOT contain the Redirect mobility option. If the redirection was successful, the mobility session MUST be established in the r2LMA. The actual PBU processing that creates the mobility session and the corresponding BCE takes place in the r2LMA. However, depending on the LMA's implementation of the PMIPv6 security framework, the security processing (such as IPsec) of the PBU may take place in the rfLMA before the PBU is transferred from the rfLMA to the r2LMA. Whenever the redirection processing has involved the r2LMA, the PBA sent by the rfLMA to the MAG MUST reflect the information the r2LMA would include in its PBA (such as mobility options, Status Value and so on). The only exceptions are possible security related options that the rfLMA MAY need to modify or remove. The rfLMA is always allowed to add more mobility options to the PBA. During the redirection process, the rfLMA MAY need to maintain a temporary MAG-rfLMA-r2LMA state and may even act as a "proxy MAG" to the r2LMA. This, however, depends on the collocation properties of the rfLMA and the r2LMA, and how the rfLMA interact with the r2LMA. The interaction may happen as a PBU/PBA packet forwarding in a conventional sense or as an inter-blade communication using some LMA architecture specific communication method. Once the redirection has Korhonen, et al. Expires April 10, 2010 [Page 13] Internet-Draft LMA Redirect Support for PMIPv6 October 2009 completed successfully from the rfLMA point of view and it has sent the PBA to the MAG, the rfLMA can remove all state information regarding the recent redirection. 5.4. Mobility Session Created After the Redirection 5.4.1. General Operation During the redirection the PBA is returned from the LMA Address where the PBU was sent to i.e., from the rfLMA. After the redirection, the MAG has to initiate another PBU/PBA exchange with the r2LMA and after that all PMIPv6 communication continues between the MAG and the r2LMA. The overall redirection flow sequence is shown in Figure 2. MAG rfLMA r2LMA | | | 1) |--PBU-->| | (redirection takes place, PBA contains r2LMA 2) |<--PBA--| | information, 'D' flag is set to 0 ) | | | 3) |-------PBU------>| (BCE gets created in r2LMA) 4) |<------PBA-------| | | | 5) |<=====data======>| | | | 6) |-------PBU------>| (lifetime extension, 7) |<------PBA-------| de-registration, etc.) | | | Figure 2: Runtime LMA assignment from rfLMA to r2LMA within a redirection domain The assumption in the signaling flow steps 1) and 2) shown in Figure 2 is that the MAG is only redirected to the r2LMA. The mobility session creation with the r2LMA requires a new PBU/PBA exchange with the r2LMA using the normal RFC 5213 procedures. 5.4.2. Mobile Access Gateway Considerations The MAG operation is exactly the same as described in Section 5.1 and Section 5.3.2 except for three aspects: o The 'D' flag in the received Redirection mobility option is set to zero (0). This indicates to the MAG that there is no mobility session (i.e. BCE) created in the r2LMA and not in the rfLMA either. The Status Value in the received PBA MUST have been set to the value TBD. The MAG was only assigned with a new r2LMA Address information. Korhonen, et al. Expires April 10, 2010 [Page 14] Internet-Draft LMA Redirect Support for PMIPv6 October 2009 o Check if there is a SA between the MAG and the r2LMA. If this check fails, then the MAG MUST either treat the PBA as if the binding update failed and log the event, or initiate dynamic creation of the SA between the MAG and the r2LMA (note that the dynamic creation of the SA is outside of the scope of this specification). o The MAG MUST initiate a new PBU/PBA exchange with the r2LMA in order to establish a mobility session. Only after a successful PBU/PBA exchange with the r2LMA, the redirection has completed. The initial PBU sent to the r2LMA SHOULD NOT contain the Redirect- Capability mobility option in order to avoid possible immediate new redirection. 5.4.3. Local Mobility Anchor Considerations If the redirection functionality is enabled in the LMA and the received PBU contains the Redirect-Capability mobility option, then the rfLMA MAY redirect the MAG to a new r2LMA. In the case of redirection, the PBA returned to the MAG MUST always include the unicast IPv6 address of the r2LMA in the Redirect mobility option with the 'D' flag set to zero (0) and the Status Value MUST be set to the value TBD. If the r2LMA has IPv4 support enabled, then the PBA returned to the MAG SHOULD include the IPv4 address of the r2LMA in the Redirect mobility option. If the rfLMA did not redirect the MAG to a new r2LMA or the redirection failed, then the PBA MUST NOT contain the Redirect mobility option. 5.5. Redirection Example This section gives a high level example of one possible "Mobility Session Created During the Redirection" solution discussed in Section 5.3. The example shows how the complete procedure for a LMA redirection takes place in a PMIPv6 domain and eventually ends up to a creation of a mobility session between a MAG and a r2LMA. Note that this section is only for example purposes, not for specifying the rfLMA to the r2LMA interaction. During the redirection PBU/PBA exchange, the mobility session and the corresponding BCE gets created in the r2LMA before the rfLMA sends the PBA back to the MAG (see the dotted lines between the rfLMA and the r2LMA in steps 1) and 2) in Figure 1). The mobility session can only be created in the r2LMA that belongs to the same redirection domain as the rfLMA. The example solution described here has the assumption that the rfLMA also has limited MAG functionality, and the rfLMA and r2LMAs have required SAs established, if needed. Korhonen, et al. Expires April 10, 2010 [Page 15] Internet-Draft LMA Redirect Support for PMIPv6 October 2009 5.5.1. Redirection During the Initial PBU/PBA Exchange Here we describe the redirection during the initial PBU/PBA exchange. Error cases are excluded for the brevity. o A MAG discovers a LMA Address in a PMIPv6 domain using some mechanism and that LMA happens to be a rfLMA in some redirection domain. o The MAG creates and sends a PBU to the rfLMA as defined in Section 5.3.2 of this specification. o The rfLMA receives the PBU from a MAG. The PBU contains relevant mobility options to enable redirection such as the Redirect- Capability mobility option. o The rfLMA does the security processing on the PBU as described in RFC 5213. The rfLMA selects an appropriate r2LMA for the mobility session under the conditions described in Section 5.3.3 of this specification and creates a temporary MAG-rfLMA-r2LMA state. The rfLMA has to maintain this state until the redirection process completes from its point of view. o The rfLMA overwrites the source address of the PBU with its own address and also overwrites the destination address of the PBU with the r2LMA Address. Furthermore, the rfLMA includes the Alternate Care-of Address mobility option containing the MAG Address into the PBU (if it was not already present) and also removes the Redirect-Capability mobility option from the PBU. After this, the rfLMA forwards the PBU to the r2LMA. o The r2LMA receives the PBU, processes it and creates the mobility session with the MAG as defined in RFC 5213. After successfully processing the PBU the r2LMA forwards a PBA to the rfLMA as defined in RFC 5213. o The rfLMA receives the PBA from the r2LMA and processes it according to the information it has concerning the temporary MAG- rfLMA-r2LMA state. This step involves the rfLMA overwriting the source and destination addresses of the PBA according to the temporary state information (the source address of the PBA will be the rfLMA Address and the destination address of the PBA will be the MAG Address). The rfLMA includes the Redirect mobility option with the appropriate r2LMA address information and 'D' flag set to 1 into the PBA. After this the rfLMA sends the PBA to the MAG. o The MAG receives the PBA from the rfLMA and processes it as defined in RFC 5213 and additionally in Section 5.3.2 of this Korhonen, et al. Expires April 10, 2010 [Page 16] Internet-Draft LMA Redirect Support for PMIPv6 October 2009 specification. In addition to the above steps, the rfLMA and the r2LMAs, and a group of r2LMAs may e.g. exchange additional status, context and load information between each other. How this information exchange is done, is out of scope of this example and the specification. Furthermore, how and based on what criteria the rfLMA selects an appropriate r2LMA is also out of scope of this example and the specification. 5.5.2. Redirection During Mid-session PBU/PBA Exchange Here we briefly discuss the mid-session redirection during a re- registration or a handover triggered PBU/PBA exchange. From the MAG point of view the actual procedural steps for mid-session redirection are the same as described in Section 5.5.1. There are few notable differences on the LMA side though. o The previous r2LMA cannot redirect the mobility session to a new r2LMA during the re-registration or the handover PBU/PBA exchange unless it also implements rfLMA functionality. The lack of rfLMA functionality in the r2LMA implicitly prohibits mid-session redirection using the solution defined in this specification. o The previous r2LMA cannot redirect the mobility session to a new r2LMA during the re-registration or the handover PBU/PBA exchange unless the previous r2LMA is able to transfer the "mobility session context" to the new r2LMA. Otherwise, the new r2LMA would receive a PBU with Handoff Indicator set to other than "Attachment over a new interface" and there would not be a matching BCE. This is an undefined situation and would most likely result the mobility session to be terminated. [ED: add more details here]. Note that a possible context transfer between LMAs is out of scope of this specification. Korhonen, et al. Expires April 10, 2010 [Page 17] Internet-Draft LMA Redirect Support for PMIPv6 October 2009 6. Multi-Homing Considerations A MN can be multi-homed. A single LMA entity should have the control over all possible multi-homed mobility sessions the MN has. All mobility sessions a multi-homed MN may have SHOULD be anchored in the single LMA entity. Therefore, once the MN has established one mobility session with one LMA, the subsequent mobility sessions of the same MN SHOULD be anchored to the LMA that was initially assigned. One possible solution already supported by this specification is applying the redirection only for the very first initial attach a multi-homed MN does towards a PMIPv6 domain. After the initial attach, the assigned r2LMA Address has been stored in the policy profile. For the subsequent mobility sessions of the multi-homed MN, the same assigned r2LMA Address would be used and there is no need to contact the rfLMA. MAGs have a control over selectively enabling and disabling the redirection of the LMA. If the multi-homed MN is attached to a PMIPv6 domain via multiple MAGs, the assigned r2LMA Address should be stored in the remote policy store and downloaded as a part of the policy profile download to a MAG. Alternatively, MAGs can share policy profile information using other means. In both cases, the actual implementation of the policy profile information sharing is specific to a PMIPv6 deployment and out of scope of this specification. Korhonen, et al. Expires April 10, 2010 [Page 18] Internet-Draft LMA Redirect Support for PMIPv6 October 2009 7. Configuration Variables This specification defines three configuration variables that control the redirection functionality within a PMIPv6 domain. EnableLMARedirectFunction This configuration variable is available in both a MAG and in a rfLMA. When set to 1 (i.e., enabled), the PMIPv6 node enables the redirection functionality. The default value is 0 (i.e., disabled). EnableLMARedirectAcceptFunction This configuration variable is available in a r2LMA. When set to 1 (i.e., enabled), the r2LMA is able to accept redirected mobility sessions from a rfLMA. The default value is 0 (i.e., disabled). Korhonen, et al. Expires April 10, 2010 [Page 19] Internet-Draft LMA Redirect Support for PMIPv6 October 2009 8. Security Considerations The security considerations of PMIPv6 signaling described in RFC 5213 apply to this document. An incorrectly configured LMA may cause unwanted redirection attempts to non-existing LMAs or to other LMAs that do not have and will not have a SA with the redirected MAG. At the same time, a falsely redirected MAG will experience failed binding updates or creation of mobility sessions. An incorrectly configured LMA may also cause biased load distribution within a PMIPv6 domain. This document also assumes that the LMAs that participate to redirection have adequate prior agreement and trust relationship between each other. If the SAs between MAGs and LMAs are manually keyed (as it might be needed by the 'direct redirection answer' scenario), then the anti- replay service of ESP protected PMIPv6 traffic cannot typically be provided. This is, however, deployment specific for a PMIPv6 domain. If a PMIPv6 domain deployment with a redirection requires that a rfLMA has to modify a received PBU in any way e.g., by changing the destination IP address field of the outer IP header, then the security mechanism (such as possible authentication options) used to protect the PBU must not cover the outer IP header on those parts that might get modified. Alternatively, the rfLMA can do all required security mechanism processing on the received PBU and remove those security related options from the PBU that would cause the security check to fail on the r2LMA. Korhonen, et al. Expires April 10, 2010 [Page 20] Internet-Draft LMA Redirect Support for PMIPv6 October 2009 9. IANA Considerations Two new mobility options for the use with PMIPv6 are defined in the [RFC3775] "Mobility Options" registry. The mobility options are defined in Section 4: Redirect-Capability Mobility Option is set to TBD1 Redirect Mobility Option is set to TBD2 This document defines the following new Status value for use in PBA messages. The value is to be allocated from the same number space, as defined in Section 6.1.8 of [RFC3775]. The allocated value MUST be greater than 128 indicating that the PBU was rejected by the LMA: NOT_LMA_FOR_THIS_MAG is set to TBD3 Korhonen, et al. Expires April 10, 2010 [Page 21] Internet-Draft LMA Redirect Support for PMIPv6 October 2009 10. Acknowledgements The author would like to thank Basavaraj Patil and Domagoj Premec for their reviews and comments on the initial versions of this document. The authors also thank Yungui Wang and Qin Wu for their comments and discussion on this document. Korhonen, et al. Expires April 10, 2010 [Page 22] Internet-Draft LMA Redirect Support for PMIPv6 October 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. [RFC5213] Gundavelli, S., Leung, K., Devarapalli, V., Chowdhury, K., and B. Patil, "Proxy Mobile IPv6", RFC 5213, August 2008. 11.2. Informative References [RFC2136] Vixie, P., Thomson, S., Rekhter, Y., and J. Bound, "Dynamic Updates in the Domain Name System (DNS UPDATE)", RFC 2136, April 1997. [RFC3484] Draves, R., "Default Address Selection for Internet Protocol version 6 (IPv6)", RFC 3484, February 2003. [RFC4291] Hinden, R. and S. Deering, "IP Version 6 Addressing Architecture", RFC 4291, February 2006. [RFC4303] Kent, S., "IP Encapsulating Security Payload (ESP)", RFC 4303, December 2005. [RFC4306] Kaufman, C., "Internet Key Exchange (IKEv2) Protocol", RFC 4306, December 2005. [RFC5142] Haley, B., Devarapalli, V., Deng, H., and J. Kempf, "Mobility Header Home Agent Switch Message", RFC 5142, January 2008. Korhonen, et al. Expires April 10, 2010 [Page 23] Internet-Draft LMA Redirect Support for PMIPv6 October 2009 Authors' Addresses Jouni Korhonen (editor) Nokia Siemens Networks Linnoitustie 6 FI-02600 Espoo FINLAND Email: jouni.nospam@gmail.com Sri Gundavelli Cisco 170 West Tasman Drive San Jose, CA 95134 USA Email: sri.gundavelli@cisco.com Hidetoshi Yokota KDDI Lab 2-1-15 Ohara, Fujimino Saitama, 356-8502 Japan Email: yokota@kddilabs.jp Xiangsong Cui Huawei Email: Xiangsong.Cui@huawei.com Korhonen, et al. Expires April 10, 2010 [Page 24]