Mipshop Working Group Rajeev Koodli, Editor INTERNET DRAFT Nokia Research Center Category: Standards Track 3 March 2007 Updates: RFC 4068 Expires: September 3, 2007 Fast Handovers for Mobile IPv6 draft-ietf-mipshop-fmipv6-rfc4068bis-01.txt By submitting this Internet-Draft, each author represents that any applicable patent or other IPR claims of which he or she is aware have been or will be disclosed, and any of which he or she becomes aware will be disclosed, in accordance with Section 6 of 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 document is a submission of the IETF MIP6 WG. Comments should be directed to the MIP6 WG mailing list, mip6@ietf.org. Abstract Mobile IPv6 enables a Mobile Node to maintain its connectivity to the Internet when moving from an Access Router to another, a process referred to as handover. During this time, the Mobile Node is unable to send or receive packets due to both link switching delay and IP protocol operations. The "handover latency" resulting from standard Mobile IPv6 procedures, namely, movement detection, new Care of Address configuration and Binding Update, is often unacceptable to real-time traffic such as Voice over IP. Reducing the handover latency could be beneficial to non real-time, throughput-sensitive applications as well. This document specifies a protocol to improve handover latency due to Mobile IPv6 procedures. This document does not address improving the link switching latency. Koodli (Editor) Expires 3 September 2007 [Page i]
Internet Draft Fast Handovers 3 March 2007 Contents Abstract i 1. Introduction 2 2. Terminology 2 3. Protocol Overview 4 3.1. Addressing the Handover Latency . . . . . . . . . . . . . 4 3.2. Protocol Operation . . . . . . . . . . . . . . . . . . . 7 3.3. Protocol Operation during Network-initiated Handover . . 8 4. Protocol Details 9 5. Other Considerations 14 5.1. Handover Capability Exchange . . . . . . . . . . . . . . 14 5.2. Determining New Care of Address . . . . . . . . . . . . . 14 5.3. Packet Loss . . . . . . . . . . . . . . . . . . . . . . . 14 5.4. DAD Handling . . . . . . . . . . . . . . . . . . . . . . 15 5.5. Fast or Erroneous Movement . . . . . . . . . . . . . . . 16 6. Message Formats 17 6.1. New Neighborhood Discovery Messages . . . . . . . . . . . 18 6.1.1. Router Solicitation for Proxy Advertisement (RtSolPr) . . . . . . . . . . . . . . . . . . . . 18 6.1.2. Proxy Router Advertisement (PrRtAdv) . . . . . . 20 6.2. Inter-Access Router Messages . . . . . . . . . . . . . . 23 6.2.1. Handover Initiate (HI) . . . . . . . . . . . . . 23 6.2.2. Handover Acknowledge (HAck) . . . . . . . . . . . 25 6.3. New Mobility Header Messages . . . . . . . . . . . . . . 27 6.3.1. Fast Binding Update (FBU) . . . . . . . . . . . . 27 6.3.2. Fast Binding Acknowledgment (FBack) . . . . . . . 28 6.3.3. Unsolicited Neighbor Advertisement (UNA) . . . . 30 6.4. New Options . . . . . . . . . . . . . . . . . . . . . . . 30 6.4.1. IP Address Option . . . . . . . . . . . . . . . . 31 6.4.2. New Router Prefix Information Option . . . . . . 32 6.4.3. Link-layer Address (LLA) Option . . . . . . . . . 33 6.4.4. Mobility Header Link-layer Address (MH-LLA) Option 34 6.4.5. Binding Authorization Data for FMIPv6 (BADF) . . 35 6.4.6. Neighbor Advertisement Acknowledgment (NAACK) . . 36 7. Configurable Parameters 38 8. Security Considerations 38 Koodli (Editor) Expires 3 September 2007 [Page ii]
Internet Draft Fast Handovers 3 March 2007 9. IANA Considerations 39 10. Acknowledgments 40 11. Normative References 41 12. Author's Address 41 13. Contributors 42 A. Change Log 42 Intellectual Property Statement 43 Disclaimer of Validity 43 Copyright Statement 43 Acknowledgment 44 Koodli (Editor) Expires 3 September 2007 [Page 1]
Internet Draft Fast Handovers 3 March 2007 1. Introduction Mobile IPv6 [3] describes the protocol operations for a mobile node to maintain connectivity to the Internet during its handover from one access router to another. These operations involve movement detection, IP address configuration, and location update. The combined handover latency is often sufficient to affect real-time applications. Throughput-sensitive applications can also benefit from reducing this latency. This document describes a protocol to reduce the handover latency. This specification addresses the following problem: how to allow a mobile node to send packets as soon as it detects a new subnet link, and how to deliver packets to a mobile node as soon as its attachment is detected by the new access router. The protocol defines IP protocol messages necessary for its operation regardless of link technology. It does this without depending on specific link-layer features while allowing link-specific customizations. By definition, this specification considers handovers that interwork with Mobile IP: once attached to its new access router, a MN engages in Mobile IP operations including Return Routability [3]. There are no special requirements for a mobile node to behave differently with respect to its standard Mobile IP operations. 2. Terminology The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", "OPTIONAL", and "silently ignore" in this document are to be interpreted as described in RFC 2119 [1]. The following terminology and abbreviations are used in this document in addition to those defined in [3]. The reference handover scenario is illustrated in Figure 1. Mobile Node (MN) A Mobile IPv6 host Access Point (AP) A Layer 2 device connected to an IP subnet that offers wireless connectivity to a MN. An Access Point Identifier (AP-ID) refers the AP's L2 address. Sometimes, AP-ID is also referred to as a Basic Service Set IDentifier (BSSID). Access Router (AR) The MN's default router Koodli (Editor) Expires 3 September 2007 [Page 2]
Internet Draft Fast Handovers 3 March 2007 Previous Access Router (PAR) The MN's default router prior to its handover New Access Router (NAR) The MN's anticipated default router subsequent to its handover Previous CoA (PCoA) The MN's Care of Address valid on PAR's subnet New CoA (NCoA) The MN's Care of Address valid on NAR's subnet Handover A process of terminating existing connectivity and obtaining new IP connectivity. Router Solicitation for Proxy Advertisement (RtSolPr) A message from the MN to the PAR requesting information for a potential handover Proxy Router Advertisement (PrRtAdv) A message from the PAR to the MN that provides information about neighboring links facilitating expedited movement detection. The message can also act as a trigger for network-initiated handover. (AP-ID, AR-Info) tuple Contains an access router's L2 and IP addresses, and prefix valid on the interface to which the Access Point (identified by AP-ID) is attached. The triplet [Router's L2 address, Router's IP address and Prefix] is called "AR-Info". Assigned Addressing A particular type of NCoA configuration in which the NAR assigns an IPv6 address for the MN. The method by which NAR manages its address pool is not specified in this document. Fast Binding Update (FBU) A message from the MN instructing its PAR to redirect its traffic (towards NAR) Fast Binding Acknowledgment (FBack) A message from the PAR in response to FBU Unsolicited Neighbor Advertisement (UNA) The message in [8] with 'O' bit cleared Koodli (Editor) Expires 3 September 2007 [Page 3]
Internet Draft Fast Handovers 3 March 2007 Fast Neighbor Advertisement (FNA) This message from RFC4068 [7] is deprecated. The UNA message above is the preferred message in this specification. Handover Initiate (HI) A message from the PAR to the NAR regarding a MN's handover Handover Acknowledge (HAck) A message from the NAR to the PAR as a response to HI v +--------------+ +-+ | Previous | < | | ------------ | Access | ------- >-----\ +-+ | Router | < \ MN | (PAR) | \ | +--------------+ +---------------+ | ^ IP | Correspondent | | | Network | Node | V | +---------------+ v / v +--------------+ / +-+ | New | < / | | ------------ | Access | ------- >-----/ +-+ | Router | < MN | (NAR) | +--------------+ Figure 1: Reference Scenario for Handover 3. Protocol Overview 3.1. Addressing the Handover Latency The ability to immediately send packets from a new subnet link depends on the "IP connectivity" latency, which in turn depends on the movement detection latency and the new CoA configuration latency. Once a MN is IP-capable on the new subnet link, it can send a Binding Update to its Home Agent and one or more correspondents. Once its correspondents successfully process the Binding Update, which typically involves the Return Routability procedure, the MN can Koodli (Editor) Expires 3 September 2007 [Page 4]
Internet Draft Fast Handovers 3 March 2007 receive packets at the new CoA. So, the ability to receive packets from correspondents directly at its new CoA depends on the Binding Update latency as well as the IP connectivity latency. The protocol enables a MN to quickly detect that it has moved to a new subnet by providing the new access point and the associated subnet prefix information when the MN is still connected to its current subnet (i.e., PAR in Figure 1). For instance, a MN may discover available access points using link-layer specific mechanisms (e.g., a "scan" in WLAN) and then request subnet information corresponding to one or more of those discovered access points. The MN may do this after performing router discovery. The MN may also do this at any time while connected to its current router. The result of resolving an identifier associated with an access point is a [AP-ID, AR-Info] tuple, which a MN can use in readily detecting movement: when attachment to an access point with AP-ID takes place, the MN knows the corresponding new router's co-ordinates including its prefix, IP address and L2 address. The "Router Solicitation for Proxy Advertisement (RtSolPr)" and "Proxy Router Advertisement (PrRtAdv)" messages 6.1 are used for aiding movement detection. Through the RtSolPr and PrRtAdv messages, the MN also formulates a prospective new CoA (NCoA), when it is still present on the PAR's link. Hence, the latency due to new prefix discovery subsequent to handover is eliminated. Furthermore, this prospective address can be used immediately after attaching to the new subnet link (i.e., NAR's link) when the MN has received a "Fast Binding Acknowledgment (FBack)" message prior to its movement. In the event it moves without receiving an FBack, the MN can still start using NCoA after announcing its attachment through an unsolicited Neighbor Advertisement message (with the 'O' bit set to zero) message [8]; NAR responds to to this UNA message in case the tentative address is already in use. In this way, NCoA configuration latency is reduced. In order to reduce the Binding Update latency, the protocol specifies a binding between the Previous CoA (PCoA) and NCoA. A MN sends a "Fast Binding Update" message to its Previous Access Router to establish this tunnel. When feasible, the MN SHOULD send FBU from PAR's link. Otherwise, it should send it immediately after detecting attachment to NAR. An FBU message MUST contain the Binding Authorization Data for FMIPv6 (BADF) option (see Section 6.4.5) in order to ensure that only a legitimate MN that owns the PCoA is able to establish a binding. Subsequent sections describe the protocol mechanics. In any case, the result is that PAR begins tunneling packets arriving for PCoA to NCoA. Such a tunnel remains active until the MN completes the Binding Update with its correspondents. In the opposite direction, the MN SHOULD reverse tunnel packets to PAR, again until it completes Binding Update. And, PAR SHOULD forward the inner packet in the tunnel to its destination (i.e., Koodli (Editor) Expires 3 September 2007 [Page 5]
Internet Draft Fast Handovers 3 March 2007 to the MN's correspondent). Such a reverse tunnel ensures that packets containing PCoA as source IP address are not dropped due to ingress filtering. Even though the MN is IP-capable on the new link, it cannot use NCoA directly with its correspondents without the correspondents first establishing a binding cache entry (for NCoA). Forwarding support for PCoA is provided through a reverse tunnel between the MN and the PAR. Setting up a tunnel alone does not ensure that the MN receives packets as soon as attaching to a new subnet link, unless NAR can detect the MN's presence. A neighbor discovery operation involving a neighbor's address resolution (i.e., Neighbor Solicitation and Neighbor Advertisement) typically results in considerable delay, sometimes lasting multiple seconds. For instance, when arriving packets trigger NAR to send Neighbor Solicitation before the MN attaches, subsequent re-transmissions of address resolution are separated by a default period of one second each. In order to circumvent this delay, a MN announces its attachment immediately with an UNA message that allows NAR to forward packets to the MN right away. As a response to UNA, the NAR creates an entry or updates an existing one (while taking any conflicts into account) in order to forward packets to the MN (see details below). Through tunnel establishment for PCoA and fast advertisement, the protocol provides expedited forwarding of packets to the MN. The protocol also provides the following important functionalities. The access routers can exchange messages to confirm that a proposed NCoA is acceptable. For instance, when a MN sends FBU from PAR's link, FBack can be delivered after NAR considers NCoA acceptable to use. This is especially useful when addresses are assigned by the access router. The NAR can also rely on its trust relationship with PAR before providing forwarding support for the MN. That is, it may create a forwarding entry for NCoA subject to "approval" from PAR which it trusts. In addition, buffering for handover traffic may be desirable. Even though the Neighbor Discovery protocol provides a small buffer (typically one or two packets) for packets awaiting address resolution, this buffer may be inadequate for traffic such as VoIP already in progress. The routers may also wish to maintain a separate buffer for servicing the handover traffic as well. Finally, the access routers could transfer network-resident contexts, such as access control, QoS, header compression, in conjunction with handover. For all these operations, the protocol provides "Handover Initiate (HI)" and "Handover Acknowledge (HAck)" messages. Both of these messages SHOULD be used. The access routers MUST have necessary security association established by means outside the scope of this document. Koodli (Editor) Expires 3 September 2007 [Page 6]
Internet Draft Fast Handovers 3 March 2007 3.2. Protocol Operation The protocol begins when a MN sends RtSolPr to its access router to resolve one or more Access Point Identifiers to subnet-specific information. In response, the access router (e.g., PAR in Figure 1) sends a PrRtAdv message which contains one or more [AP-ID, AR-Info] tuples. The MN may send RtSolPr at any convenient time, for instance as a response to some link-specific event (a ``trigger'') or simply after performing router discovery. However, the expectation is that prior to sending RtSolPr, the MN has discovered the available APs by link-specific methods. The RtSolPr and PrRtAdv messages do not establish any state at the access router, and their packet formats are defined in Section 6.1. With the information provided in the PrRtAdv message, the MN formulates a prospective NCoA and sends an FBU message. The purpose of FBU is to authorize PAR to bind PCoA to NCoA, so that arriving packets can be tunneled to the new location of the MN. The FBU should be sent from PAR's link whenever feasible. For instance, an internal link-specific trigger could enable FBU transmission from the previous link. When it is not feasible, FBU is sent from the new link. Care must be taken to ensure that NCoA used in FBU does not conflict with an address already in use by some other node on link. The format and semantics of FBU processing are specified in Section 6.3.1. The FBU message MUST contain the BADF option (see Section 6.4.5) to secure the message. Depending on whether an FBack is received or not on the previous link, which clearly depends on whether FBU was sent in the first place, there are two modes of operation. 1. The MN receives FBack on the previous link. This means that packet tunneling would already be in progress by the time the MN handovers to NAR. The MN SHOULD send UNA immediately after attaching to NAR, so that arriving as well as buffered packets can be forwarded to the MN right away. Before sending FBack to MN, PAR can determine whether NCoA is acceptable to NAR through the exchange of HI and HAck messages. When assigned addressing (i.e., addresses are assigned by the router) is used, the proposed NCoA in FBU is carried in HI, and NAR MAY assign the proposed NCoA. Such an assigned NCoA MUST be returned in HAck, and PAR MUST in turn provide the assigned NCoA in FBack. If there is an assigned NCoA returned in FBack, the MN MUST use the assigned address (and not the proposed address in FBU) upon attaching to NAR. Koodli (Editor) Expires 3 September 2007 [Page 7]
Internet Draft Fast Handovers 3 March 2007 2. The MN does not receive FBack on the previous link. One reason for this is that the MN has not sent the FBU. The other is that the MN has left the link after sending the FBU, which may be lost, but before receiving an FBack. Without receiving an FBack in the latter case, the MN cannot ascertain whether PAR has successfully processed the FBU. Hence, the MN (re)sends FBU immediately after sending the UNA message. If NAR detects that NCoA is in use when processing UNA, for instance while creating a neighbor entry, it sends a Router Advertisement with "Neighbor Advertisement Acknowledge (NAACK)" option in which NAR MAY include an alternate IP address for the MN to use. Detailed UNA processing rules are specified in Section 6.3.3. The scenario in which a MN sends FBU and receives FBack on PAR's link is illustrated in Figure 2. For convenience, this scenario is called "predictive" mode of operation. The scenario in which the MN sends FBU from NAR's link is illustrated in Figure 3. For convenience, this scenario is called "reactive" mode of operation. Note that the reactive mode also includes the case when FBU has been sent from PAR's link but FBack has not been received yet. The Figure is intended to illustrate that the FBU is forwarded through NAR, but it is processed only by the PAR. Finally, the PrRtAdv message may be sent unsolicited, i.e., without the MN first sending RtSolPr. This mode is described in Section 3.3. 3.3. Protocol Operation during Network-initiated Handover In some wireless technologies, the handover control may reside in the network even though the decision to undergo handover may be arrived at by cooperation between the MN and the network. In such networks, the PAR can send an unsolicited PrRtAdv containing the link layer address, IP address and subnet prefix of the NAR when the network decides that a handover is imminent. The MN MUST process this PrRtAdv to configure a new care of address on the new subnet, and MUST send an FBU to PAR prior to switching to the new link. After transmitting PrRtAdv, the PAR MUST continue to forward packets to the MN on its current link until the FBU is received. The rest of the operation is the same as that described in Section 3.2. The unsolicited PrRtAdv also allows the network to inform the MN about geographically adjacent subnets without the MN having to explicitly request that information. This can reduce the amount of wireless traffic required for the MN to obtain a neighborhood topology map of links and subnets. Such usage of PrRtAdv is decoupled from the actual handover. See Section 6.1.2. Koodli (Editor) Expires 3 September 2007 [Page 8]
Internet Draft Fast Handovers 3 March 2007 MN PAR NAR | | | |------RtSolPr------->| | |<-----PrRtAdv--------| | | | | |------FBU----------->|----------HI--------->| | |<--------HAck---------| | <--FBack---|--FBack---> | | | | disconnect forward | | packets ===============>| | | | | | | connect | | | | | |------------UNA --------------------------->| |<=================================== deliver packets | | Figure 2: "Predictive" Fast Handover 4. Protocol Details All description makes use of Figure 1 as the reference. After discovering one or more nearby access points, the MN sends RtSolPr in order to resolve access point identifiers to subnet router information. A convenient time to do this is after performing router discovery. However, the MN can send RtSolPr at any time, e.g., when one or more new access points are discovered. The MN can also send RtSolPr more than once during its attachment to PAR. The trigger for sending RtSolPr can originate from a link-specific event, such as the promise of a better signal strength from another access point coupled with fading signal quality with the current access point. Such events, often broadly referred to as "L2 triggers", are outside the scope of this document. Nevertheless, they serve as events that invoke this protocol. For instance, when a "link up" indication is obtained on the new link, protocol messages (e.g., UNA) can be immediately transmitted. Implementations SHOULD make use of such triggers whenever available. Koodli (Editor) Expires 3 September 2007 [Page 9]
Internet Draft Fast Handovers 3 March 2007 MN PAR NAR | | | |------RtSolPr------->| | |<-----PrRtAdv--------| | | | | disconnect | | | | | | | | connect | | |-------UNA-----------|--------------------->| |-------FBU-----------|---------------------)| | |<-------FBU----------)| | forward | | packets(including FBAck)=====>| | | | |<=================================== deliver packets | | Figure 3: "Reactive" Fast Handover The RtSolPr message contains one or more AP-IDs. A wildcard requests all available tuples. As a response to RtSolPr, PAR sends a PrRtAdv message which indicates one of the following possible conditions. 1. If the PAR does not have an entry corresponding to the new access point, it responds indicating that the new access point is unknown. The MN MUST stop fast handover protocol operations on the current link. The MN MAY send an FBU from its new link. 2. If the new access point is connected to the PAR's current interface (to which MN is attached), PAR responds with a Code value indicating that the new access point is connected to the current interface, but not send any prefix information. This scenario could arise, for example, when several wireless access points are bridged into a wired network. No further protocol action is necessary. 3. If the new access point is known and the PAR has information about it, then PAR responds indicating that the new access point is known and supply the [AP-ID, AR-Info] tuple. If the new Koodli (Editor) Expires 3 September 2007 [Page 10]
Internet Draft Fast Handovers 3 March 2007 access point is known, but does not support fast handover, the PAR MUST indicate this with Code 3 (See Section 6.1.2). 4. If a wildcard is supplied as an identifier for the new access point, the PAR SHOULD supply neighborhood [AP-ID, AR-Info] tuples subject to path MTU restrictions (i.e., provide any 'n' tuples without exceeding the link MTU). When further protocol action is necessary, some implementations may choose to provide buffering support at PAR to address the scenario in which a MN leaves without sending an FBU message from the PAR's link. While the protocol does not forbid such an implementation support, care must be taken to ensure that the PAR continues forwaring packets to the PCoA (i.e., uses a buffer and forward approach). The PAR should also stop buffering once it processes the FBU message. The method by which Access Routers exchange information about their neighbors and thereby allow construction of Proxy Router Advertisements with information about neighboring subnets is outside the scope of this document. The RtSolPr and PrRtAdv messages MUST be implemented by a MN and an access router that supports fast handovers. However, when the parameters necessary for the MN to send packets immediately upon attaching to the NAR are supplied by the link layer handover mechanism itself, use of above messages is optional on such links. After a PrRtAdv message is processed, the MN sends FBU and includes the proposed NCoA. The MN SHOULD send FBU from PAR's link whenever "anticipation" of handover is feasible. When anticipation is not feasible or when it has not received an FBack, the MN sends FBU immediately after attaching to NAR's link. In response to FBU, PAR establishes a binding between PCoA ("Home Address") and NCoA, and sends FBack to MN. Prior to establishing this binding, PAR SHOULD send a HI message to NAR, and receive HAck in response. In order to determine the NAR's address for the HI message, the PAR can perform longest prefix match of NCoA (in FBU) with the prefix list of neighboring access routers. When the source IP address of FBU is PCoA, i.e., the FBU is sent from the PAR's link, the HI message MUST have a Code value set to 0. See Section 6.2.1. When the source IP address of FBU is not PCoA, i.e., the FBU is sent from the NAR's link, the HI message MUST have a Code value of 1. See Section 6.2.1. The HI message contains the PCoA, link-layer address and the NCoA of the MN. In response to processing a HI message with Code 0, the NAR 1. determines whether NCoA supplied in the HI message is a valid address for use, and if it is, starts proxying [8] the address for PROXY_ND_LIFETIME during which the MN is expected to connect Koodli (Editor) Expires 3 September 2007 [Page 11]
Internet Draft Fast Handovers 3 March 2007 to NAR. In case there is already an NCoA present, NAR may verify if the LLA is the same as its own or that of the MN itself. If so, NAR may allow the use of NCoA. 2. allocates NCoA for the MN when assigned addressing is used, creates a proxy neighbor cache entry and begins defending it. The NAR MAY allocate the NCoA proposed in HI. 3. MAY create a host route entry for PCoA (on the interface to which the MN is attaching to) in case NCoA cannot be accepted or assigned. This host route entry SHOULD be implemented such that until the MN's presence is detected, either through explicit announcement by the MN or by other means, arriving packets do not invoke neighbor discovery. The NAR SHOULD also set up a reverse tunnel to PAR in this case. 4. provides the status of handover request in Handover Acknowledge (HAck) message. When the Code value in HI is 1, NAR MUST skip the above operations. However, it SHOULD be prepared to process any other options which may be defined in the future. Sending a HI message with Code 1 allows NAR to validate the neighbor cache entry it creates for the MN during UNA processing. That is, NAR can make use of the knowledge that its trusted peer (i.e., PAR) has a trust relationship with the MN. If HAck contains an assigned NCoA, it must be included in FBack, and the MN must use it. The PAR MAY send FBack to the previous link as well to facilitate faster reception in the event the MN be still present there. The result of FBU and FBack processing is that PAR begins tunneling MN's packets to NCoA. If the MN does not receive an FBack message even after re-transmitting FBU for FBU|RETRIES, it must assume that fast handover support is not available and stop the protocol operation. As soon as the MN establishes link connectivity with the NAR, it 1. sends a UNA message (see 6.3.3). If the MN has not received an FBack by the time UNA is being sent, it SHOULD send an FBU message following the UNA message. 2. joins the all-nodes multicast group and the solicited-node multicast group corresponding to the NCoA 3. starts a DAD probe for NCoA. See [9]. When a NAR receives a UNA message, it Koodli (Editor) Expires 3 September 2007 [Page 12]
Internet Draft Fast Handovers 3 March 2007 1. SHOULD create a neighbor cache entry for NCoA if none exists and set it to STALE. This allows it to forward any arriving packets while it probes bidirectional reachability. 2. updates an entry in INCOMPLETE state, if it exists, to STALE and forwards arriving and buffered packets. This would be the case if NAR had previously sent a Neighbor Solicitation which went unanswered perhaps because the MN had not yet attached to the link. 3. deletes its proxy neighbor cache entry, if any, updates the state to STALE, and forwards arriving and buffered packets. The buffer for handover traffic should be linked to this UNA processing. The exact mechanism is implementation dependent. The NAR may detect that NCoA is in use by another node when processing the UNA message, in which case it 1. MUST NOT update the existing entry. 2. MUST send a Router Advertisement with the NAACK option in which it MAY include an alternate NCoA for use. This message MUST be sent to the source IP address present in UNA using the same Layer 2 address present in UNA. If the MN receives an IP address in the NAACK option, it MUST use it and send an FBU using the new CoA. As a special case, the address supplied in NAACK could be PCoA itself, in which case the MN MUST NOT send any more FBUs. The Status codes for NAACK option are specified in Section 6.4.6. Once the MN has confirmed its NCoA (either through DAD or when provided for by the NAR), it SHOULD send a Neighbor Advertisement message with the 'O' bit set, to the all-nodes multicast address. This message allows MN's neighbors to update their neighbor cache entries. For data forwarding, the PAR tunnels packets using its global IP address valid on the interface to which the MN was attached. The MN reverse tunnels its packets to the same global address of PAR. The tunnel end-point addresses must be configured accordingly. When PAR receives a reverse tunneled packet, it must verify if a secure binding exists for the MN identified by PCoA in the tunneled packet, before forwarding the packet. Koodli (Editor) Expires 3 September 2007 [Page 13]
Internet Draft Fast Handovers 3 March 2007 5. Other Considerations 5.1. Handover Capability Exchange The MN expects a PrRtAdv in response to its RtSolPr message. If the MN does not receive a PrRtAdv message even after RTSOLPR|RETRIES, it must assume that PAR does not support the fast handover protocol and stop sending any more RtSolPr messages. Even if a MN's current access router is capable of providing fast handover support, the new access router may not be capable of providing such support. This is indicated to the MN during "runtime", through the PrRtAdv message with a Code value of 3 (see Section 6.1.2). 5.2. Determining New Care of Address Typically, the MN formulates its prospective NCoA using the information provided in a PrRtAdv message, and sends FBU. This NCoA can be provided to NAR in the HI message. NAR provides a disposition of HI, and hence the NCoA itself, in the HAck message indicating whether NCoA is acceptable. However, the MN itself does not have to wait on PAR's link for this exchange to take place. It can handover any time after sending the FBU message; sometimes it may be forced to handover without sending the FBU. In any case, it can still confirm using NCoA from NAR's link by sending the UNA message. If PrRtAdv message carries a NCoA, the MN MUST use it as its prospective NCoA. 5.3. Packet Loss Handover involves link switching, which may not be exactly co-ordinated with fast handover signaling. Furthermore, the arrival pattern of packets is dependent on many factors, including application characteristics, network queuing behaviors etc. Hence, packets may arrive at NAR before the MN is able to establish its link there. These packets will be lost unless they are buffered by the NAR. Similarly, if the MN attaches to NAR and then sends an FBU message, packets arriving at PAR until FBU is processed will be lost unless they are buffered. This protocol provides an option to indicate request for buffering at the NAR in the HI message. When the PAR requests this feature (for the MN), it SHOULD also provide its own support for buffering. Koodli (Editor) Expires 3 September 2007 [Page 14]
Internet Draft Fast Handovers 3 March 2007 5.4. DAD Handling Duplicate Address Detection (DAD) was defined in [9] to avoid address duplication on links when stateless address auto-configuration is used. The use of DAD to verify the uniqueness of an IPv6 address configured through stateless auto-configuration adds delays to a handover. The probability of an interface identifier duplication on the same subnet is very low, however it cannot be ignored. In this draft certain precautions are proposed to minimize the effects of a duplicate address occurrence as well as recovery actions in the event of a collision. In some cases the NAR may already have the knowledge required to assess whether the MN's address is a duplicate or not before the MN moves to the new subnet. For example, the NAR can have a list of all nodes on its subnet for access control, and by searching this list, it can confirm whether the MN's address is a duplicate or not. In some other deployments, the NAR may maintain a pool of duplicate-free addresses in a list for handover purposes. The result of NCoA disposition is sent back to the PAR in the HAck message. The NAR can also indicate this in the NAACK option as a response to the UNA message. When there is a duplicate, NAR can propose (in NAACK option) an alternative NCoA or support the PCoA using the host route forwarding. When no such support is available, the MN would have to follow the address configuration procedure according to [9] after attaching to the NAR. In deployments where NAR does not have means to assess and inform the uniqueness of NCoA or cannot provide a duplicate-free address using HI and HAck exchange, the following scenarios are possible, although highly improbable considering that the probability of a random address collision is very small. 1. The MN sends FBU from the previous link which results in packet forwarding to NCoA. These packets may arrive before the MN attaches to NAR, and hence the latter may invoke Neighbor Discovery. In the event that there is another node which already owns the NCoA, NAR (incorrectly) forwards those packets to such a node. When the MN arrives on the link, it immediately sends a UNA message, which allows NAR to detect a collision. NAR immediately sends a Router Advertisement with NAACK option, forcing the MN to either use another NCoA supplied in NAACK or reconfigure a new one. The MN must send an FBU immediately following the NCoA configuration. As a special case, the NCoA may be that of NAR itself, which allows the MN to send FBU that binds its PCoA to NAR's address. This recovers from temporary misdelivery of packets. Where this is a concern, the deployments Koodli (Editor) Expires 3 September 2007 [Page 15]
Internet Draft Fast Handovers 3 March 2007 SHOULD use HI and HAck exchange which mitigates the problem by allowing NAR to proxy the NCoA; such a proxying itself can detect a collision if an entry already exists in the neighbor cache entry. 2. The MN sends a UNA message followed by an FBU from the new link. When NAR processes the UNA message, either there is already an entry for NCoA or there is no entry. If there is an entry, it either belongs to the MN itself (e.g., in INCOMPLETE state) or the entry belongs to another node. These entries can be distinguished by the LLA; the entry with INCOMPLETE state has no LLA. If the entry belongs to another node, NAR immediately sends a Router Advertisement with NAACK option (as above) and the MN MUST immediately send a new FBU to PAR with a different NCoA. Hence, extent of any misdelivery is minimized. If there is no existing entry for NCoA but there is another node which owns NCoA, the scenario is more complicated. According to [8], the UNA message does not create any entry if there is none to begin with. However, NAR performs Neighbor Solicitation when packets arrive from PAR (due to FBU processing). Both the MN and the rightful owner respond with Neighbor Advertisement (NA), but the MN's Neighbor Advertisement will have the 'O' bit cleared. If the MN's NA arrives first, NAR starts forwarding to it, but redirects those packets once the NA from the rightful owner is processed. At the time of updating the neighbor cache entry, the NAR must send a Router Advertisement with NAACK option to the MN (as above), and the MN MUST immediately send a new FBU to the PAR. If the MN's NA arrives after the NA from the rightful owner, NAR similarly sends a Router Advertisement with NAACK option, and the MN sends a new FBU to the PAR. In both the cases, the extent of misdelivery can be controlled and recovery is possible. The scenario where NAR has no entry for NCoA at all when packets arrive is possible even when using HI and HAck messages. The available options in this case appear to be a) performing DAD for a set of addresses beforehand for handover purposes, and b) maintaining a table of IP addresses of all nodes on the link (similar to Mobile IPv4 visitor list). The NAR can then provide a conflict-free address in the HAck message or the NAACK option. 5.5. Fast or Erroneous Movement Although this specification is for fast handover, the protocol has its limits in terms of how fast a MN can move. A special case of fast movement is ping-pong, where a MN moves between the same two access points rapidly. Another instance of the same problem is Koodli (Editor) Expires 3 September 2007 [Page 16]
Internet Draft Fast Handovers 3 March 2007 erroneous movement i.e., the MN receives information prior to a handover that it is moving to a new access point but it either moves to a different one or aborts movement altogether. All of the above behaviors are usually the result of link layer idiosyncrasies and thus are often tackled at the link layer itself. IP layer mobility, however, introduces its own limits. IP layer handovers should occur at a rate suitable for the MN to update the binding of, at least, its Home Agent and preferably that of every CN with which it is in communication. A MN that moves faster than necessary for this signaling to complete, which may be of the order of few seconds, may start losing packets. The signaling overhead over the air and in the network may increase significantly, especially in the case of rapid movement between several access routers. To avoid the signaling overhead, the following measures are suggested. A MN returning to the PAR before updating the necessary bindings when present on NAR MUST send a Fast Binding Update with Home Address equal to the MN's PCoA and a lifetime of zero, to the PAR. The MN should have a security association with the PAR since it performed a fast handover to the NAR. The PAR, on receiving this Fast Binding Update, will check its set of outgoing (temporary fast handover) tunnels. If it finds a match it SHOULD terminate that tunnel; i.e., start delivering packets directly to the node instead. Temporary tunnels for the purposes of fast handovers should use short lifetimes (of the order of a small number of seconds or less). The lifetime of such tunnels should be enough to allow a MN to update all its active bindings. The default lifetime of the tunnel should be the same as the lifetime value in the FBU message. The effect of erroneous movement is typically limited to loss of packets since routing can change and the PAR may forward packets towards another router before the MN actually connects to that router. If the MN discovers itself on an unanticipated access router, it SHOULD send a new Fast Binding Update to the PAR. This FBU supercedes the existing binding at PAR and the packets will be redirected to the new confirmed location of the MN. 6. Message Formats All the ICMPv6 messages have a common Type specified in [4]. The messages are distinguished based on the Subtype field (see below). The values for the Subtypes are specified in Section 9. For all the ICMPv6 messages, the checksum is defined in [2]. Koodli (Editor) Expires 3 September 2007 [Page 17]
Internet Draft Fast Handovers 3 March 2007 6.1. New Neighborhood Discovery Messages 6.1.1. Router Solicitation for Proxy Advertisement (RtSolPr) Mobile Nodes send Router Solicitation for Proxy Advertisement in order to prompt routers for Proxy Router Advertisements. All the link-layer address options have the format defined in 6.4.3. 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 | Code | Checksum | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Subtype | Reserved | Identifier | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Options ... +-+-+-+-+-+-+-+-+-+-+-+- Figure 4: Router Solicitation for Proxy Advertisement (RtSolPr) Message IP Fields: Source Address An IP address assigned to the sending interface Destination Address The address of the Access Router or the all routers multicast address. Hop Limit 255. See RFC 2461. ICMP Fields: Type The Experimental Mobility Protocol Type. See [4]. Code 0 Checksum The ICMPv6 checksum. Subtype 2 Reserved MUST be set to zero by the sender and ignored by Koodli (Editor) Expires 3 September 2007 [Page 18]
Internet Draft Fast Handovers 3 March 2007 the receiver. Identifier MUST be set by the sender so that replies can be matched to this Solicitation. Valid Options: Source Link-layer Address When known, the link-layer address of the sender SHOULD be included using the Link-Layer Address option. See LLA option format below. New Access Point Link-layer Address The link-layer address or identification of the access point for which the MN requests routing advertisement information. It MUST be included in all RtSolPr messages. More than one such address or identifier can be present. This field can also be a wildcard address. See LLA Option below. Future versions of this protocol may define new option types. Receivers MUST silently ignore any options that they do not recognize and continue processing the rest of the message. Including the source LLA option allows the receiver to record the sender's L2 address so that neighbor discovery, when the receiver needs to send packets back to the sender (of RtSolPr message), can be avoided. When a wildcard is used for New Access Point LLA, no other New Access Point LLA options must be present. A Proxy Router Advertisement (PrRtAdv) message should be received by the MN as a response to RtSolPr. If such a message is not received in a short time period but no less than twice the typical round trip time (RTT) over the access link or 100 milliseconds if RTT is not known, it SHOULD resend RtSolPr message. Subsequent retransmissions can be up to RTSOLPR_RETRIES, but MUST use an exponential backoff in which the timeout period (i.e., 2xRTT or 100 milliseconds) is doubled prior to each instance of retransmission. If Proxy Router Advertisement is not received by the time the MN disconnects from the PAR, the MN SHOULD send FBU immediately after configuring a new CoA. When RtSolPr messages are sent more than once, they MUST be rate limited with MAX_RTSOLPR_RATE per second. During each use of RtSolPr, exponential backoff is used for retransmissions. Koodli (Editor) Expires 3 September 2007 [Page 19]
Internet Draft Fast Handovers 3 March 2007 6.1.2. Proxy Router Advertisement (PrRtAdv) Access routers send out Proxy Router Advertisement message gratuitously if the handover is network-initiated or as a response to RtSolPr message from a MN, providing the link-layer address, IP address and subnet prefixes of neighboring routers. All the link-layer address options have the format defined in 6.4.3. 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 | Code | Checksum | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Subtype | Reserved | Identifier | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Options ... +-+-+-+-+-+-+-+-+-+-+-+- Figure 5: Proxy Router Advertisement (PrRtAdv) Message IP Fields: Source Address MUST be the link-local address assigned to the interface from which this message is sent. Destination Address The Source Address of an invoking Router Solicitation for Proxy Advertisement or the address of the node the Access Router is instructing to handover. Hop Limit 255. See RFC 2461. ICMP Fields: Type The Experimental Mobility Protocol Type. See [4]. Code 0, 1, 2, 3 or 4. See below. Checksum The ICMPv6 checksum. Koodli (Editor) Expires 3 September 2007 [Page 20]
Internet Draft Fast Handovers 3 March 2007 Subtype 3 Reserved MUST be set to zero by the sender and ignored by the receiver. Identifier Copied from Router Solicitation for Proxy Advertisement or set to Zero if unsolicited. Valid Options in the following order: Source Link-layer Address When known, the link-layer address of the sender SHOULD be included using the Link-Layer Address option. See LLA option format below. New Access Point Link-layer Address The link-layer address or identification of the access point is copied from RtSolPr message. This option MUST be present. New Router's Link-layer Address The link-layer address of the Access Router for which this message is proxied for. This option MUST be included when Code is 0 or 1. New Router's IP Address The IP address of NAR. This option MUST be included when Code is 0 or 1. New Router Prefix Information Option. Specifies the prefix of the Access Router the message is proxied for and is used for address auto-configuration. This option MUST be included when Code is 0 or 1. However, when this prefix is the same as what is used in the New Router's IP Address option (above), the Prefix Information option need not be present. New CoA Option MAY be present when PrRtAdv is sent unsolicited. PAR MAY compute new CoA using NAR's prefix information and the MN's L2 address, or by any other means. Future versions of this protocol may define new option types. Receivers MUST silently ignore any options they do not recognize and continue processing the message. Koodli (Editor) Expires 3 September 2007 [Page 21]
Internet Draft Fast Handovers 3 March 2007 Currently, Code values 0, 1, 2, 3 and 4 are defined. A Proxy Router Advertisement with Code 0 means that the MN should use the [AP-ID, AR-Info] tuple (present in the options above) for movement detection and NCoA formulation. The Option-Code field in the New Access Point LLA option in this case is 1 reflecting the LLA of the access point for which the rest of the options are related. Multiple tuples may be present. A Proxy Router Advertisement with Code 1 means that the message is sent unsolicited. If a New CoA option is present following the New Router Prefix Information option, the MN SHOULD use the supplied NCoA and send FBU immediately or else stand to lose service. This message acts as a network-initiated handover trigger. See Section 3.3. The Option-Code field in the New Access Point LLA option (see below) in this case is 1 reflecting the LLA of the access point for which the rest of the options are related. A Proxy Router Advertisement with Code 2 means that no new router information is present. Each New Access Point LLA option contains an Option-Code value (described below) which indicates a specific outcome. - When the Option-Code field in the New Access Point LLA option is 5, handover to that access point does not require change of CoA. No other options are required in this case. - When the Option-Code field in the New Access Point LLA option is 6, PAR is not aware of the Prefix Information requested. The MN SHOULD attempt to send FBU as soon as it regains connectivity with the NAR. No other options are required in this case. - When the Option-Code field in the New Access Point LLA option is 7, it means that the NAR does not support fast handover. The MN MUST stop fast handover protocol operations. No other options are required in this case. A Proxy Router Advertisement with Code 3 means that new router information is present only for a subset of access points requested. The Option-Code field values (defined above including a value of 1) distinguish different outcomes for individual access points. A Proxy Router Advertisement with Code 4 means that the subnet information regarding neighboring access points is sent unsolicited, but the message is not a handover trigger, unlike when the message is sent with Code 1. Multiple tuples may be present. When a wildcard AP identifier is supplied in the RtSolPr message, the PrRtAdv message should include any 'n' [Access Point Identifier, Koodli (Editor) Expires 3 September 2007 [Page 22]
Internet Draft Fast Handovers 3 March 2007 Link-layer address option, Prefix Information Option] tuples corresponding to the PAR's neighborhood. 6.2. Inter-Access Router Messages 6.2.1. Handover Initiate (HI) The Handover Initiate (HI) is an ICMPv6 message sent by an Access Router (typically PAR) to another Access Router (typically NAR) to initiate the process of a MN's handover. 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 | Code | Checksum | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Subtype |S|U| Reserved | Identifier | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Options ... +-+-+-+-+-+-+-+-+-+-+-+- Figure 6: Handover Initiate (HI) Message IP Fields: Source Address The IP address of the PAR Destination Address The IP address of the NAR Hop Limit 255. See RFC 2461. ICMP Fields: Type The Experimental Mobility Protocol Type. See [4]. Code 0 or 1. See below Checksum The ICMPv6 checksum. Koodli (Editor) Expires 3 September 2007 [Page 23]
Internet Draft Fast Handovers 3 March 2007 Subtype 4 S Assigned address configuration flag. When set, this message requests a new CoA to be returned by the destination. May be set when Code = 0. MUST be 0 when Code = 1. U Buffer flag. When set, the destination SHOULD buffer any packets towards the node indicated in the options of this message. Used when Code = 0, SHOULD be set to 0 when Code = 1. Reserved MUST be set to zero by the sender and ignored by the receiver. Identifier MUST be set by the sender so replies can be matched to this message. Valid Options: Link-layer address of MN The link-layer address of the MN that is undergoing handover to the destination (i.e., NAR). This option MUST be included so that the destination can recognize the MN. Previous Care of Address The IP address used by the MN while attached to the originating router. This option SHOULD be included so that host route can be established in case necessary. New Care of Address The IP address the MN wishes to use when connected to the destination. When the `S' bit is set, NAR MAY assign this address. The PAR uses a Code value of 0 when it processes an FBU with PCoA as source IP address. The PAR uses a Code value of 1 when it processes an FBU whose source IP address is not PCoA. If Handover Acknowledge (HAck) message is not received as a response in a short time period but no less than twice the typical round trip time (RTT) between source and destination, or 100 milliseconds if RTT is not known, the Handover Initiate SHOULD be re-sent. Subsequent retransmissions can be up to HI_RETRIES, but MUST use exponential backoff in which the timeout period (i.e., 2xRTT or 100 milliseconds) is doubled during each instance of retransmission. Koodli (Editor) Expires 3 September 2007 [Page 24]
Internet Draft Fast Handovers 3 March 2007 6.2.2. Handover Acknowledge (HAck) The Handover Acknowledgment message is a new ICMPv6 message that MUST be sent (typically by NAR to PAR) as a reply to the Handover Initiate message. 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 | Code | Checksum | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Subtype | Reserved | Identifier | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Options ... +-+-+-+-+-+-+-+-+-+-+-+- Figure 7: Handover Acknowledge (HAck) Message IP Fields: Source Address Copied from the destination address of the Handover Initiate Message to which this message is a response. Destination Address Copied from the source address of the Handover Initiate Message to which this message is a response. Hop Limit 255. See RFC 2461. ICMP Fields: Type The Experimental Mobility Protocol Type. See [4]. Code 0: Handover Accepted, NCoA valid 1: Handover Accepted, NCoA not valid 2: Handover Accepted, NCoA in use 3: Handover Accepted, NCoA assigned (used in Assigned addressing) Koodli (Editor) Expires 3 September 2007 [Page 25]
Internet Draft Fast Handovers 3 March 2007 4: Handover Accepted, NCoA not assigned (used in Assigned addressing) 5: Handover Accepted, use PCoA 128: Handover Not Accepted, reason unspecified 129: Administratively prohibited 130: Insufficient resources Checksum The ICMPv6 checksum. Subtype 5 Reserved MUST be set to zero by the sender and ignored by the receiver. Identifier Copied from the corresponding field in the Handover Initiate message this message is in response to. Valid Options: New Care of Address If the S flag in the Handover Initiate message is set, this option MUST be used to provide NCoA the MN should use when connected to this router. This option MAY be included even when `S' bit is not set, e.g., Code 2 above. Upon receiving a HI message, the NAR MUST respond with a Handover Acknowledge message. If the `S' flag is set in the HI message, the NAR SHOULD include the New Care of Address option and a Code 3. The NAR MAY provide support for PCoA (instead of accepting or assigning NCoA), using a host route entry to forward packets to the PCoA, and using a tunnel to the PAR to forward packets from the MN (sent with PCoA as source IP address). This host route entry SHOULD be used to forward packets once the NAR detects that the particular MN is attached to its link. The NAR indicates forwarding support for PCoA using Code value 5 in the HAck message. Subsequently, PAR establishes a tunnel to NAR in order to forward packets arriving for PCoA. When responding to a HI message containing a Code value 1, the Code values 1, 2, and 4 in the HAck message are not relevant. Finally, the new access router can always refuse handover, in which case it should indicate the reason in one of the available Code values. Koodli (Editor) Expires 3 September 2007 [Page 26]
Internet Draft Fast Handovers 3 March 2007 6.3. New Mobility Header Messages Mobile IPv6 uses a new IPv6 header type called Mobility Header [3]. The Fast Binding Update, Fast Binding Acknowledgment and Fast Neighbor Advertisement messages use the Mobility Header. 6.3.1. Fast Binding Update (FBU) The Fast Binding Update message is identical to the Mobile IPv6 Binding Update (BU) message. However, the processing rules are slightly different. +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Sequence # | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |A|H|L|K| Reserved | Lifetime | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | | . . . Mobility options . . . | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Figure 8: Fast Binding Update (FBU) Message IP fields: Source address The PCoA or NCoA Destination Address The IP address of the Previous Access Router `A' flag MUST be set to one to request PAR to send a Fast Binding Acknowledgment message. `H' flag MUST be set to one. See [3]. `L' flag See [3]. `K' flag See [3]. Koodli (Editor) Expires 3 September 2007 [Page 27]
Internet Draft Fast Handovers 3 March 2007 Reserved This field is unused. MUST be set zero. Sequence Number See [3]. Lifetime The requested time in seconds for which the sender wishes to have a binding. Mobility Options MUST contain alternate CoA option set to NCoA IP address when FBU is sent from PAR's link. MUST contain the Binding Authorization Data for FMIP (BADF) option. See 6.4.5. The MN sends FBU message any time after receiving a PrRtAdv message. If the MN moves prior to receiving a PrRtAdv message, it SHOULD send a FBU to the PAR after configuring NCoA on the NAR according to Neighbor Discovery and IPv6 Address Configuration protocols. The source IP address is PCoA when FBU is sent from PAR's link, and the source IP address is NCoA when sent from NAR's link. The FBU MUST also include the Home Address Option and the Home Address is PCoA. A FBU message MUST be protected so that PAR is able to determine that the FBU message is sent by a genuine MN. 6.3.2. Fast Binding Acknowledgment (FBack) The Fast Binding Acknowledgment message is sent by the PAR to acknowledge receipt of a Fast Binding Update message in which the `A' bit is set. If PAR sends a HI message to the NAR after processing an FBU, the FBack message SHOULD NOT be sent to the MN before the PAR receives a HAck message from the NAR. The PAR MAY send the FBack immediately in the reactive mode however. The Fast Binding Acknowledgment MAY also be sent to the MN on the old link. IP fields: Source address The IP address of the Previous Access Router Destination Address The NCoA Status 8-bit unsigned integer indicating the disposition of the Fast Binding Update. Values of the Status field less than 128 indicate that the Binding Update was accepted by the receiving Koodli (Editor) Expires 3 September 2007 [Page 28]
Internet Draft Fast Handovers 3 March 2007 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Status |K| Reserved | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Sequence # | Lifetime | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | | . . . Mobility options . . . | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Figure 9: Fast Binding Acknowledgment (FBack) Message node. The following such Status values are currently defined: 0 Fast Binding Update accepted 1 Fast Binding Update accepted but NCoA is invalid. Use NCoA supplied in ``alternate'' CoA Values of the Status field greater than or equal to 128 indicate that the Binding Update was rejected by the receiving node. The following such Status values are currently defined: 128 Reason unspecified 129 Administratively prohibited 130 Insufficient resources 131 Incorrect interface identifier length `K' flag See [3]. Reserved An unused field. MUST be set to zero. Sequence Number Copied from FBU message for use by the MN in matching this acknowledgment with an outstanding FBU. Koodli (Editor) Expires 3 September 2007 [Page 29]
Internet Draft Fast Handovers 3 March 2007 Lifetime The granted lifetime in seconds for which the sender of this message will retain a binding for traffic redirection. Mobility Options MUST contain ``alternate'' CoA if Status is 1. MUST contain the Binding Authorization Data for FMIP (BADF) option. See 6.4.5. 6.3.3. Unsolicited Neighbor Advertisement (UNA) This is the same message as in [8] with the requirement that the 'O' bit is always set to zero. Since this is an unsolicited message, the 'S' bit is zero, and since this is sent by a MN, the 'R' bit is also zero. The Source Address must be the NCoA. The Destination Address is typically the all-nodes multicast address. The Target Address must include the NCoA, and Target link-layer address must include the MN's LLA. The MN sends a UNA message to the NAR, as soon as it regains connectivity on the new link. Arriving or buffered packets can be immediately forwarded. If NAR is proxying NCoA, it creates a neighbor cache entry in STALE state but forwards packets as it determines bidirectional reachability. If there is an entry in INCOMPLETE state without a link-layer address, it sets it to STALE. If there is no entry at all, creating an entry in STALE state is recommended since forwarding can immediately begin when packets arrive without first invoking Neighbor Solicitation and Advertisement (which may involve retransmission delay in the event of messages being lost). During the process of creating a neighbor cache entry, NAR can also detect if NCoA is in use, and immediately sends a Router Advertisement with NAACK option in the event of collision (see Section 5.4 for more details). The combination of NCoA (present in source IP address) and the Link-Layer Address (present as a Target LLA) SHOULD be used to distinguish the MN from other nodes. 6.4. New Options All the options are of the form shown in Figure 10. The Type values are defined from the Neighbor Discovery options space. The Length field is in units of 8 octets, except for the Koodli (Editor) Expires 3 September 2007 [Page 30]
Internet Draft Fast Handovers 3 March 2007 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 | Option-Code | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ~ ... ~ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Figure 10: Option Format Mobility Header Link-Layer Address option, whose Length field is in units of octets in accordance with [3], Section 6.2. And, Option-Code provides additional information for each of the options (See individual options below). 6.4.1. IP Address Option This option is sent in the Proxy Router Advertisement, the Handover Initiate, and Handover Acknowledge messages. 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 | Option-Code | Prefix Length | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Reserved | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | | + + | | + IPv6 Address + | | + + | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Figure 11: IPv6 Address Option Koodli (Editor) Expires 3 September 2007 [Page 31]
Internet Draft Fast Handovers 3 March 2007 Type To be assigned by IANA Length The size of this option in 8 octets including the Type, Option-Code and Length fields. Option-Code 1 Old Care-of Address 2 New Care-of Address 3 NAR's IP address Prefix Length The Length of the IPv6 Address Prefix. Reserved MUST be set to zero by the sender and MUST be ignored by the receiver. IPv6 address The IP address defined by the Option-Code field. 6.4.2. New Router Prefix Information Option This option is sent in the PrRtAdv message in order to provide the prefix information valid on the NAR. Type To be assigned by IANA Length The size of this option in 8 octets including the Type, Option-Code and Length fields. Option-Code 0 Prefix Length 8-bit unsigned integer. The number of leading bits in the Prefix that are valid. The value ranges from 0 to 128. Reserved MUST be set to zero by the sender and MUST be ignored by the receiver. Koodli (Editor) Expires 3 September 2007 [Page 32]
Internet Draft Fast Handovers 3 March 2007 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 | Option-Code | Prefix Length | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Reserved | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | | + + | | + Prefix + | | + + | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Figure 12: New Router Prefix Information Option Prefix An IP address or a prefix of an IP address. The Prefix Length field contains the number of valid leading bits in the prefix. The bits in the prefix after the prefix length are reserved and MUST be initialized to zero by the sender and ignored by the receiver. 6.4.3. Link-layer Address (LLA) Option 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 | Option-Code | LLA... +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Figure 13: Link-Layer Address Option Type To be assigned by IANA Koodli (Editor) Expires 3 September 2007 [Page 33]
Internet Draft Fast Handovers 3 March 2007 Length The size of this option in 8 octets including the Type, Option-Code and Length fields. Option-Code 0 wildcard requesting resolution for all nearby access points 1 Link-layer Address of the New Access Point 2 Link-layer Address of the MN 3 Link-layer Address of the NAR (i.e., Proxied Originator) 4 Link-layer Address of the source of RtSolPr or PrRtAdv message 5 The access point identified by the LLA belongs to the current interface of the router 6 No prefix information available for the access point identified by the LLA 7 No fast handovers support available for the access point identified by the LLA LLA The variable length link-layer address. The LLA Option does not have a length field for the LLA itself. The implementations must consult the specific link layer over which the protocol is run in order to determine the content and length of the LLA. Depending on the size of individual LLA option, appropriate padding MUST be used to ensure that the entire option size is a multiple of 8 octects. The New Access Point Link Layer address contains the link-layer address of the access point for which handover is about to be attempted. This is used in the Router Solicitation for Proxy Advertisement message. The MN Link-Layer address option contains the link-layer address of a MN. It is used in the Handover Initiate message. The NAR (i.e., Proxied Originator) Link-Layer address option contains the Link Layer address of the Access Router for which the Proxy Router Solicitation message refers to. 6.4.4. Mobility Header Link-layer Address (MH-LLA) Option This option is identical to the LLA option, but is carried in the Mobility Header messages, e.g., FBU. In the future, other Mobility Header messages may also make use of this option. The format of the Koodli (Editor) Expires 3 September 2007 [Page 34]
Internet Draft Fast Handovers 3 March 2007 option is shown in Figure 14. There are no alignment requirements for this option. 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 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Option-Code | LLA .... +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Figure 14: Mobility Header Link-Layer Address Option Type To be assigned by IANA Length The size of this option in octets not including the Type and Length fields. Option-Code 2 Link-layer Address of the MN LLA The variable length link-layer address. 6.4.5. Binding Authorization Data for FMIPv6 (BADF) This option MUST be present in FBU and FBack messages. The security association between the MN and the PAR is established by companion protocols [5]. This option specifies how to compute and verify a MAC using the established security association. The format of this option is shown in Figure 15. Type To be assigned by IANA Option Length The length of the Authenticator in bytes Koodli (Editor) Expires 3 September 2007 [Page 35]
Internet Draft Fast Handovers 3 March 2007 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 | Option Length | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | SPI | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | | + + | Authenticator | + + | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Figure 15: Binding Authorization Data for FMIPv6 (BADF) Option SPI Security Parameter Index. SPI = 0 is reserved for the Authenticator computed using SEND-based handover keys. Authenticator Same as in RFC 3775, with "correspondent" replaced by PAR's IP address, and Kbm replaced by the shared key between the MN and the PAR. The default MAC calculation is done using HMAC|SHA1 with the first 96 bits used for the MAC. Since there is an Option Length field, implementations can use other algorithms such as HMAC|SHA256 for instance. This option MUST be the last Mobility Option present. 6.4.6. Neighbor Advertisement Acknowledgment (NAACK) Type To be assigned by IANA. Length 8-bit unsigned integer. Length of the option, in 8 Koodli (Editor) Expires 3 September 2007 [Page 36]
Internet Draft Fast Handovers 3 March 2007 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 | Option-Code | Status | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Reserved | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Figure 16: Neighbor Advertisement Acknowledgment Option octets. The length is 1 when a new CoA is not supplied. The length is 3 when a new CoA is present (immediately following the Reserved field) Option-Code 0 Status 8-bit unsigned integer indicating the disposition of the Fast Neighbor Advertisement message. The following Status values are currently defined: 1 The New CoA is invalid 2 The New CoA is invalid, use the supplied CoA. The New CoA (in the form of an IP Address Option) MUST be present following the Reserved field. 3 The New CoA is invalid, use NAR's IP address as NCoA in FBU 4 PCoA supplied, do not send FBU 128 Link Layer Address unrecognized Reserved MUST be set to zero by the sender and MUST be ignored by the receiver. The NAR responds to UNA with the NAACK option to notify the MN to use a different NCoA if there is address collision. If the NCoA is invalid, the Router Advertisement MUST use the NCoA as the destination address but use the L2 address present in UNA. The MN SHOULD use the NCoA if it is supplied with the NAACK option. If the NAACK indicates that the Link Layer Address is unrecognized the MN MUST NOT use the NCoA or the PCoA and SHOULD start immediately the process of acquiring different NCoA at the NAR. Koodli (Editor) Expires 3 September 2007 [Page 37]
Internet Draft Fast Handovers 3 March 2007 In the future, new option types may be defined. 7. Configurable Parameters Parameter Name Default Value Definition ------------------- ---------------------- ------- RTSOLPR_RETRIES 3 Section6.1.1 MAX_RTSOLPR_RATE 3 Section6.1.1 FBU_RETRIES 3 Section 4 PROXY_ND_LIFETIME 1.5 seconds Section 6.2.2 HI_RETRIES 3 Section 6.2.1 8. Security Considerations The following security vulnerabilities are identified, and suggested solutions mentioned. 1. Insecure FBU: in this case, packets meant for one address could be stolen, or redirected to some unsuspecting node. This concern is the same as that in a MN and Home Agent relationship. Hence, the PAR MUST ensure that the FBU packet arrived from a node that legitimately owns the PCoA. The access router and its hosts may use any available mechanism to establish a security association which MUST be used to secure FBU. The current version of this protocol relies on a companion protocol [5] to establish such a security association. Using the shared handover key from [5], the Authenticator in BADF option (see 6.4.5) MUST be computed, and the BADF option included in FBU and FBack messages. If an access router can ensure that the source IP address in an arriving packet could only have originated from the node whose link-layer address is in the router's neighbor cache, then a bogus node cannot use a victim's IP address for malicious redirection of traffic. Such an operation is recommended at least on neighbor discovery messages including the RtSolPr message. 2. Secure FBU, malicious or inadvertent redirection: in this case, the FBU is secured, but the target of binding happens to be an unsuspecting node either due to inadvertent operation or due to malicious intent. This vulnerability can lead to a MN with genuine security association with its access router redirecting traffic to an incorrect address. Koodli (Editor) Expires 3 September 2007 [Page 38]
Internet Draft Fast Handovers 3 March 2007 However, the target of malicious traffic redirection is limited to an interface on an access router with which the PAR has a security association. The PAR MUST verify that the NCoA to which PCoA is being bound actually belongs to NAR's prefix. In order to do this, HI and HAck message exchanges are to be used. When NAR accepts NCoA in HI (with Code = 0), it proxies NCoA so that any arriving packets are not sent on the link until the MN attaches and announces itself through UNA. So, any inadvertent or malicious redirection to a host is avoided. It is still possible to jam NAR's buffer with redirected traffic. However, since NAR's handover state corresponding to NCoA has a finite (and short) lifetime corresponding to a small multiple of anticipated handover latency, the extent of this vulnerability is arguably small. 3. Sending FBU from NAR's link: a malicious node may send FBU from NAR's link providing an unsuspecting node's address as NCoA. This is similar to base Mobile IP where the MN can provide some other's node as its CoA to its Home Agent. As discussed in Section 5.4, the extent of such a misdelivery can be controlled and recovery is possible. In addition, it is possible to isolate the MN if it continues to misbehave. 9. IANA Considerations This document defines four new experimental ICMPv6 messages which use the Experimental Mobility Protocol ICMPv6 format [4]. These require four new Subtype value assignments out of the Experimental Mobility Protocol Subtype Registry [4] as follows: Subtype Description Reference ------- ----------- --------- 2 RtSolPr Section 6.1.1 3 PrRtAdv Section 6.1.2 4 HI Section 6.2.1 5 HAck Section 6.2.2 The document defines four new Neighbor Discovery [8] options which need Type assignment from IANA. Koodli (Editor) Expires 3 September 2007 [Page 39]
Internet Draft Fast Handovers 3 March 2007 Option-Type Description Reference ----------- ----------- --------- TBD IP Address Option Section 6.4.1 TBD New Router Prefix Information Option Section 6.4.2 TBD Link-layer Address Option Section 6.4.3 TBD Neighbor Advertisement Acknowledgment Option Section 6.4.6 The document defines three new Mobility Header messages which need type allocation from the Mobility Header Types registry at http://www.iana.org/assignments/mobility-parameters: 1. Fast Binding Update, described in Section 6.3.1 2. Fast Binding Acknowledgment, described in Section 6.3.2, and The document defines two new Mobility Options which need type assignment from the Mobility Options Type registry at http://www.iana.org/assignments/mobility-parameters: 1. Mobility Header Link-Layer Address option, described in Section 6.4.4. 2. Binding Authorization Data for FMIPv6 (BADF) option, described in Section 6.4.5. 10. Acknowledgments The editor would like to thank all those who have provided feedback on this specification, and acknowledges the following people: Vijay Devarapalli, Youn-Hee Han, Emil Ivov, Syam Madanapalli, Suvidh Mathur, Andre Martin, Javier Martin, Koshiro Mitsuya, Gabriel Montenegro, Takeshi Ogawa, Sun Peng, YC Peng, Alex Petrescu, Domagoj Premec, Subba Reddy, K. Raghav, Ranjit Wable and Jonathan Wood. The editor would like to acknowledge the contribution from James Kempf to improve this specification. The editor would also like to thank [mipshop] working group chair Gabriel Montenegro and the erstwhile [mobile ip] working group chairs Basavaraj Patil and Phil Roberts for providing much support for this work. Koodli (Editor) Expires 3 September 2007 [Page 40]
Internet Draft Fast Handovers 3 March 2007 11. Normative References [1] S. Bradner, ``Key words for use in RFCs to Indicate Requirement Levels,'' Request for Comments (Best Current Practice) 2119, Internet Engineering Task Force, March 1997. [2] A. Conta and S. Deering, ``Internet Control Message Protocol (ICMPv6) for the Internet Protocol Version 6 (IPv6) Specification'', Request for Comments (Draft Standard) 2463, Internet Engineering Task Force, December 1998. [3] D. Johnson, C. E. Perkins, and J. Arkko, ``Mobility Support in IPv6'', Request for Comments (Proposed Standard) 3775, Internet Engineering Task Force, June 2004. [4] J. Kempf, ``Instructions for Seamoby and Experimental Mobility Protocol IANA Allocations," RFC 4065, Internet Engineering Task Force, June 2004. [5] J. Kempf and R. Koodli, "Distributing a Symmetric FMIPv6 Handover Key using SEND," draft-ietf-mipshop-handover-key-00.txt (work in progress), February 2007. [6] S. Kent and R. Atkinson, ``IP Authentication Header'', Request for Comments (Draft Standard) 2402, Internet Engineering Task Force, November 1998. [7] R. Koodli (Editor), "Fast Handovers for Mobile IPv6," Request For Comments 4068, Internet Engineering Task Force, July 2005. [8] T. Narten, E. Nordmark, and W. Simpson, ``Neighbor Discovery for IP Version 6 (IPv6)'', Request for Comments (Draft Standard) 2461, Internet Engineering Task Force, December 1998. [9] S. Thomson and T. Narten, ``IPv6 Stateless Address Autoconfiguration'', Request for Comments (Draft Standard) 2462, Internet Engineering Task Force, December 1998. 12. Author's Address Rajeev Koodli, Editor Nokia Research Center 313 Fairchild Drive Mountain View, CA 94043 USA E-Mail: Rajeev.Koodli@nokia.com Koodli (Editor) Expires 3 September 2007 [Page 41]
Internet Draft Fast Handovers 3 March 2007 13. Contributors This document has its origins in the fast handover design team in the erstwhile [mobile ip] working group. The members of this design team in alphabetical order were; Gopal Dommety, Karim El-Malki, Mohammed Khalil, Charles Perkins, Hesham Soliman, George Tsirtsis and Alper Yegin. A. Change Log - RFC4068bis: all the issues in the tracker since the publication of RFC 4068. (http://www.mip4.org/issues/tracker/mipshop) The following changes pre-date RFC 4068 publication. - Added IPSec AH reference. - Changed options format to make use of RFC 2461 options Type space. Revised IANA Considerations section accordingly. - Added exponential backoff for retransmissions. Added rate limiting for RtSolPr message. - Replaced ``attachment point'' with ``access point'' for consistency. - Clarified [AP-ID, AR-Info] in Section 2. Clarified use of Prefix Information Option in Section 6.1.2. - Separated MH-LLA from LLA to future-proof LLA option. The following changes refer up to version 02 (under mipshop). The Section numbers refer to version 06 (under mobile ip). - New ICMPv6 format incorporated. ID Nits conformance. - Last Call comments incorporated - Revised the security considerations section in v07 - Refined and added a section on network-initiated handover v07 - Section 3 format change - Section 4 format change (i.e., no subsections). Koodli (Editor) Expires 3 September 2007 [Page 42]
Internet Draft Fast Handovers 3 March 2007 - Description in Section 4.4 merged with ``Fast or Erroneous Movement'' - Section 4.5 deprecated - Section 4.6 deprecated - Revision of some message formats in Section 6 Intellectual Property Statement The IETF takes no position regarding the validity or scope of any Intellectual Property Rights or other rights that might be claimed to pertain to the implementation or use of the technology described in this document or the extent to which any license under such rights might or might not be available; nor does it represent that it has made any independent effort to identify any such rights. Information on the procedures with respect to rights in RFC documents can be found in BCP 78 and BCP 79. Copies of IPR disclosures made to the IETF Secretariat and any assurances of licenses to be made available, or the result of an attempt made to obtain a general license or permission for the use of such proprietary rights by implementers or users of this specification can be obtained from the IETF on-line IPR repository at http://www.ietf.org/ipr. The IETF invites any interested party to bring to its attention any copyrights, patents or patent applications, or other proprietary rights that may cover technology that may be required to implement this standard. Please address the information to the IETF at ietf-ipr@ietf.org. Disclaimer of Validity This document and the information contained herein are provided on an "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY, THE IETF TRUST AND THE INTERNET ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE. Copyright Statement Copyright (C) The IETF Trust (2007). Koodli (Editor) Expires 3 September 2007 [Page 43]
Internet Draft Fast Handovers 3 March 2007 This document is subject to the rights, licenses and restrictions contained in BCP 78, and except as set forth therein, the authors retain all their rights. Acknowledgment Funding for the RFC Editor function is currently provided by the Internet Society. Koodli (Editor) Expires 3 September 2007 [Page 44]
