Mobile IPv4 Working Group Rajeev Koodli INTERNET DRAFT Charles E. Perkins Experimental Nokia Research Center 6 February 2007 Mobile IPv4 Fast Handovers draft-ietf-mip4-fmipv4-03.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 MIP4 WG. Comments should be directed to the MIP4 WG mailing list, mip4@ietf.org. Abstract This document adapts the Mobile IPv6 Fast Handovers [1] to improve delay and packet loss resulting from Mobile IPv4 handover operations. Specifically, this document addresses movement detection, IP address configuration and location update latencies during a handover. For reducing the IP address configuration latency, the document proposes that the new Care-of Address is always made to be the new access router's IP address. Additional mechanisms may be defined in the future versions of this document. Koodli, Perkins Expires 6 August 2007 [Page i]
Internet Draft Fast Handovers for Mobile IPv4 6 February 2007 Contents Abstract i 1. Introduction 2 2. Factors Affecting Handover 3 3. Protocol 4 3.1. Overview . . . . . . . . . . . . . . . . . 4 3.2. Operation . . . . . . . . . . . . . . . . . 5 4. Use of Previous FA Notification Extension 8 5. Message Formats 9 5.1. Fast Binding Update (FBU) . . . . . . . . . . . . 9 5.2. Fast Binding Acknowledgment (FBAck) . . . . . . . . . 11 5.3. Router Solicitation for Proxy Advertisement (RtSolPr) . 13 5.4. Proxy Router Advertisement (PrRtAdv) . . . . . . . . 15 5.5. Inter-Access Router Messages . . . . . . . . . . 17 5.5.1. Handover Initiate (HI) . . . . . . . . . 17 5.5.2. Handover Acknowledge (HAck) . . . . . . . . 19 6. Option formats 22 6.1. Link-Layer Address Option Format . . . . . . . . . 22 6.2. New IPv4 Address Option Format . . . . . . . . . . 23 6.3. New Router Prefix Information Option . . . . . . . . 24 7. Security Considerations 25 8. IANA Considerations 25 9. Acknowledgement 25 Intellectual Property Statement 27 Koodli, Perkins Expires 6 August 2007 [Page ii]
Internet Draft Fast Handovers for Mobile IPv4 6 February 2007 Disclaimer of Validity 27 Copyright Statement 28 Acknowledgment 28 Koodli, Perkins Expires 6 August 2007 [Page 1]
Internet Draft Fast Handovers for Mobile IPv4 6 February 2007 1. Introduction This document adapts the fast handover specification [1] to IPv4 networks. The fast handover protocol specified in this document is particularly interesting for operation over wireless links such as IEEE 802 wireless links. Fast handovers are not typically needed for wired media due to the relatively large delays attributable to establishing new connections in today's wired networks. Mobile IPv4 [2] registration messages are re-used (with new type numbers) to enable faster implementation using existing Mobile IPv4 software. This draft does not rely on link-layer triggers for protocol operation, but performance will typically be enhanced by using the appropriate triggers when they are available. This document assumes that the reader is familiar with the basic operation and terminology of Mobile IPv4 [1] and Fast Handovers for Mobile IPv6 [1]. The active agents that enable continued packet delivery to a mobile node (MN) are the access routers on the networks that the mobile node connects to. Handover means that the mobile node changes its network connection, and we consider the scenario in which this change means change in access routers. The mobile node utilizes the access routers as default routers in the normal sense, but also as partners in mobility management. Thus, when the mobile node moves to a new network, it processes handover-related signaling in order to identify and develop a relationship with a new access router. In this document, we call the previous access router PAR and the new access router NAR, consistent with the terminology in [1]. Unless otherwise mentioned, a PAR is also a Previous Foreign Agent (PFA) and a NAR is also a New Foreign Agent (NFA). On a particular network, a mobile node may obtain its IP address via DHCP [6] (i.e., Co-located Care-of Address) or use the Foreign Agent CoA. During a handover, the new CoA (NCoA) is always made to be that of NAR. This allows a mobile node to receive and send packets using its previous CoA (PCoA), so that delays resulting from IP configuration (such as DHCP address acquisition delay) Koodli, Perkins Expires 6 August 2007 [Page 2]
Internet Draft Fast Handovers for Mobile IPv4 6 February 2007 subsequent to attaching to the new link are disengaged from affecting the existing sessions. 2. Factors Affecting Handover Both the link-layer operations and IP layer procedures affect the perceived handover performance. However, the overall performance is also (always) a function of specific implementation of the technology as well as the system configuration. This document only specifies IP layer protocol operations. The purpose of this section is to provide an illustration of events that affect handover performance, but it is purely informative. The IP layer handover delay and packet loss are influenced by latencies due to movement detection, IP address configuration and Mobile IP registration procedure. Movement detection latency comes from the need to reliably detect movement to a new subnet. This is a function of frequency of router advertisements as well as default agent reachability. IP address configuration latency depends on the particular IP CoA being used. If co-located mode with DHCP is used, the latency is quite likely going to be higher and unacceptable for real-time applications such as Voice over IP. Finally, the Mobile IP registration procedure needs a round-trip of delay between the Mobile Node and its Home Agent over the Internet. This delay is incurred after the mobile node performs movement detection and IP configuration. Underlying the IP operations are link-layer procedures. These are clearly technology-specific. For instance in IEEE 802.11, the handover operation typically involves scanning access points over all available channels, selecting a suitable access point, and associating with it. It may also involve performing access control operations such as those specified in IEEE 802.1X [4]. These delays contribute to the handover performance. Optimizations are being proposed for standardization in IEEE, for instance see [5] and [3]. Together with appropriate implementation techniques, Koodli, Perkins Expires 6 August 2007 [Page 3]
Internet Draft Fast Handovers for Mobile IPv4 6 February 2007 these optimizations can provide the required level of delay support at the link-layer for real-time applications. 3. Protocol 3.1. Overview The design of the protocol is the same as for Mobile IPv6 [1]. Readers should consult [1] for details, and here we provide a summary. The protocol avoids the delay due to movement detection and IP configuration and disengage Mobile IP registration delay from the time-critical path. The protocol provides the surrounding network network neighborhood information so that a mobile node can determine whether it is moving to a new subnet even before the handover. The information provided and the signaling exchanged between the local mobility agents allows the mobile node to send and receive packets immediately after handover. In order to disengage the Mobile IP registration latency, the protocol provides routing support for the continued use of a mobile node's previous CoA. After a mobile node obtains its IPv4 care-of address, it builds a neighborhood access point and subnet map using the Router Solicitation for Proxy Advertisement (RtSolPr) and Proxy Router Advertisement (PrRtAdv) messages. The mobile node may scan for access points (APs) based on the configuration policy in operation for its wireless network interface. If a scan results in a new AP discovery, the mobile node resolves the corresponding AP Identifier to subnet information using the RtSolPr and PrRtAdv messages mentioned above. At some point, the mobile node decides to undergo handover. It sends an FBU message to PAR from the previous link or from the new link. FBU message enables creation of a binding between the mobile node's previous CoA and the new CoA. Koodli, Perkins Expires 6 August 2007 [Page 4]
Internet Draft Fast Handovers for Mobile IPv4 6 February 2007 The coordination between the access routers is done by way of the Handover Initiate (HI) and Handover Acknowledge (HAck) messages defined in [1]. After these signals have been exchanged between the previous and new access routers (PAR and NAR), data arriving at PAR will be tunneled to NAR for delivery to the newly arrived mobile node. The purpose of HI is to securely deliver the routing parameters for establishing this tunnel. The tunnel is created by the access routers in response to the delivery of the FBU from the mobile node. 3.2. Operation In response to a handover trigger or indication, the mobile node sends a Fast Binding Update message to Previous Access Router (PAR) (see Section 5.1). Depending on whether the Mobile IP mode of operation, the PCoA is either the Home Address (in FA CoA mode) or co-located CoA (in CCoA mode). The FBU message SHOULD be sent when the mobile node is still connected to PAR. When sent in this ``predictive'' mode, the fields in the FBU are used as follows: - ``Home Address'' field must be the PCoA (which can be either the Home Address or the co-located CoA) - Home Agent field, even though redundant, must be set to PAR's IP address - Care-of Address field must be the NAR's IP address discovered via PrRtAdv message - Destination IP address must be PAR's IP address - Source IP address must be the PCoA (which can be either the Home Address or the co-located CoA) As a result of processing the FBU, PAR creates a binding between PCoA and NAR's IP address in its routing table. The PAR sends an FBack message (see 5.2) as a response to the mobile node. Koodli, Perkins Expires 6 August 2007 [Page 5]
Internet Draft Fast Handovers for Mobile IPv4 6 February 2007 The timeline for the predictive mode of operation (adapted from [1]) is shown in Figure 1. MN PAR NAR | | | |------RtSolPr------->| | |<-----PrRtAdv--------| | | | | |------FBU----------->|--------HI--------->| | |<------HAck---------| | <--FBack---|--FBack---> | | | | disconnect forward | | packets===============>| | | | | | | connect | | | | | |--------- FBU --------------------------->| |<=================================== deliver packets | |<-----FBU-----------| Figure 1: Predictive Fast Handover The mobile node sends the FBU regardless of its previous transmission when attachment to a new link is detected. This minimally allows NAR to detect mobile node's attachment, but also the retransmission of FBU when an FBack has not been received yet. When sent in this ``reactive'' mode, the following fields in FBU are set differently compared to the predictive mode: Koodli, Perkins Expires 6 August 2007 [Page 6]
Internet Draft Fast Handovers for Mobile IPv4 6 February 2007 - Destination IP address must be NAR's IP address - Source IP address must be PCoA (either the Home Address or the co-located CoA) When NAR receives FBU, it may already have processed the HI message and created a host route entry for the PCoA. In that case, NAR should immediately forward arriving and buffered packets including the FBAck message. In any case, NAR MUST forward the contents of this message, starting from the Type field, to PAR, which means the Source and Destination IP addresses now contain the IP addresses of NAR and PAR respectively. The reactive mode of operation (adapted from [1]) is illustrated in Figure 2. The Handover Initiate (HI) and Handover Acknowledge (HAck) messages serve to establish a bidirectional tunnel between the routers to support packet forwarding for PCoA. The tunnel itself is established as a response to the FBU message. The PAR sends HI message with Code = 0 when it receives FBU with source IP address set to PCoA. The PAR sends HI with Code = 1 when it receives FBU with source IP address not set to PCoA (i.e., when received from NAR). This allows NAR to disambiguate HI message processing sent as a response to predictive and reactive modes of operation. If NAR receives a HI message with Code = 1, and it has already set up a host route entry and a reverse tunnel for PCoA, it should silently discard the HI message. The protocol provides an option for NAR to return NCoA for use by the mobile node. When NAR can provide an NCoA for exclusive use of the mobile node, the address is supplied in the HAck message. The PAR includes this NCoA in FBack. Even though the mobile node can obtain this NCoA from the NAR, it is unaware of the address at the time it sends an FBU. Hence, it binds PCoA to NAR's IP address as before. Koodli, Perkins Expires 6 August 2007 [Page 7]
Internet Draft Fast Handovers for Mobile IPv4 6 February 2007 MN PAR NAR | | | |------RtSolPr------->| | |<-----PrRtAdv--------| | | | | disconnect | | | | | | | | connect | | |-----------FBU-------|------------------->| | |<-----FBU-----------| | |------FBack-------->| | forward | | packets===============>| | | | |<=================================== deliver packets | | Figure 2: Reactive Fast Handover 4. Use of Previous FA Notification Extension Sending FBU from the new link (i.e., reactive mode) is similar to using the extension defined in [2]. However, with the neighborhood information gathered using the proxy router messages (see Section 5.3, Section 5.4), movement detection and router discovery delays are avoided even in the reactive case. The FBU and FBAck messages defined in this document can be naturally used even when no neighborhood information is available. Koodli, Perkins Expires 6 August 2007 [Page 8]
Internet Draft Fast Handovers for Mobile IPv4 6 February 2007 5. Message Formats 5.1. Fast Binding Update (FBU) The FBU format is bitwise identical to the Registration Request format in RFC 3344. The same destination port number, 434, is used, but the FBU and FBAck messages in this specification have new message type numbers. 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 |x|x|D|M|G|r|T|x| reserved | Lifetime | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Home Address | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Home Agent | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Care-of Address | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | | + Identification + | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Extensions ... +-+-+-+-+-+-+-+- Figure 3: Fast Binding Update (FBU) Message Koodli, Perkins Expires 6 August 2007 [Page 9]
Internet Draft Fast Handovers for Mobile IPv4 6 February 2007 IP fields: Source address The interface address from which the message is sent. Either PCoA (co-located or Home Address), or NAR's IP address (when forwarded from NAR to PAR). Destination Address The IP address of the Previous Access Router or the New Access Router. Source Port variable Destination port 434 Type To be assigned by IANA Flags See RFC 3344 reserved Sent as zero, ignored on input Lifetime The number of seconds remaining before binding expires. MUST NOT exceed 10 seconds. Home Address MUST be PCoA (i.e., either co-located CoA or Home Address) Home Agent The Previous Access Router's global IP address Care-of Address The New Access Router's global IP address Identification See RFC 3344 Extensions MUST contain the MN - PAR Authentication Extension Koodli, Perkins Expires 6 August 2007 [Page 10]
Internet Draft Fast Handovers for Mobile IPv4 6 February 2007 5.2. Fast Binding Acknowledgment (FBAck) The FBAck format is bitwise identical to the Registration Reply format in [2]. 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 | reserved | Lifetime | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Home Address | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Home Agent | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | | + Identification + | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Extensions ... +-+-+-+-+-+-+-+- Figure 4: Fast Binding Acknowledgment (FBAck) Message Koodli, Perkins Expires 6 August 2007 [Page 11]
Internet Draft Fast Handovers for Mobile IPv4 6 February 2007 IP fields: Source address Typically copied from the destination address of the FBU message Destination Address Copied from the Source IP address in FBU message Source Port variable Destination port copied from the source port in FBU message Type To be assigned by IANA Code Indicates the result of processing FBU message. Code = 0 means Fast Binding Update accepted. Code = 1 means Fast Binding Update accepted but NCoA is supplied as an extension. reserved Sent as zero, ignored on input Lifetime The number of seconds remaining before binding expires. MUST NOT exceed 10 seconds. Home Address PCoA (i.e., either co-located CoA or Home Address) Home Agent The Previous Access Router's global IP address Identification a 64-bit number used for matching FBU. See RFC 3344. Koodli, Perkins Expires 6 August 2007 [Page 12]
Internet Draft Fast Handovers for Mobile IPv4 6 February 2007 Extensions The PAR - MN Authentication extension MUST be present. In addition, an NCoA option MUST be present when NAR supplies the NCoA. If the FBAck message indicates that the new care-of address is a Foreign Agent care-of address [2], then the mobile node MUST set the 'D' bit in its Registration Request message that it uses to register the NCoA with its home agent. 5.3. 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 6.1. The message format and processing rules are identical to those defined in [1]. We only provide the format here for convenience. 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: Router Solicitation for Proxy (RtSolPr) Message IP Fields: Koodli, Perkins Expires 6 August 2007 [Page 13]
Internet Draft Fast Handovers for Mobile IPv4 6 February 2007 Source Address An IP address assigned to the sending interface Destination Address The address of the Access Router or the all routers multicast address. Time-to-Live At least 1. See RFC 1256. ICMP Fields: Type To be assigned by IANA Code 0 Checksum The 16-bit one's complement of the one's complement sum of the ICMP message, start- ing with the ICMP Type. For computing the checksum, the Checksum and the Reserved fields are set to 0. See RFC 1256. Subtype To be assigned by IANA Reserved MUST be set to zero by the sender and ignored by the receiver. Identifier MUST be set by the sender so that replies can be matched to this Solicitation. Valid Options: 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 Koodli, Perkins Expires 6 August 2007 [Page 14]
Internet Draft Fast Handovers for Mobile IPv4 6 February 2007 be a wildcard address with all bits set to zero. 5.4. 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 mobile node, providing the link-layer address, IP address and subnet prefixes of neighboring routers. All the link-layer address options have the format defined in 6.1. The message format and processing rules are identical to those defined in [1]. We only provide the format here for convenience. 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 6: Proxy Router Advertisement (PrRtAdv) Message IP Fields: Source Address An IP address assigned to the sending interface Koodli, Perkins Expires 6 August 2007 [Page 15]
Internet Draft Fast Handovers for Mobile IPv4 6 February 2007 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. Time-to-Live At least 1. See RFC 1256. ICMP Fields: Type To be assigned by IANA Code 0, 1, 2, 3 or 4. See below. Checksum The 16-bit one's complement of the one's complement sum of the ICMP message, start- ing with the ICMP Type. For computing the checksum, the Checksum and the Reserved fields are set to 0. See RFC 1256. Subtype To be assigned by IANA. 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: 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 Koodli, Perkins Expires 6 August 2007 [Page 16]
Internet Draft Fast Handovers for Mobile IPv4 6 February 2007 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 The number of leading bits that define the network number of the corresponding Router's IP Address option (see above). 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. 5.5. Inter-Access Router Messages 5.5.1. Handover Initiate (HI) The Handover Initiate (HI) is an ICMP message sent by an Access Router (typically PAR) to another Access Router (typically NAR) to initiate the process of a mobile node's handover. The message format and processing rules are identical to those defined in [1]. We only provide the format here for convenience. IP Fields: Source Address The IP address of the PAR Destination Address The IP address of the NAR Koodli, Perkins Expires 6 August 2007 [Page 17]
Internet Draft Fast Handovers for Mobile IPv4 6 February 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 | Code | Checksum | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Subtype |S|U| Reserved | Identifier | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Options ... +-+-+-+-+-+-+-+-+-+-+-+- Figure 7: Handover Initiate (HI) Message Time-to-Live At least 1. See RFC 1256. ICMP Fields: Type To be assigned by IANA Code 0 or 1. See below Checksum The 16-bit one's complement of the one's complement sum of the ICMP message, start- ing with the ICMP Type. For computing the checksum, the Checksum and the Reserved fields are set to 0. See RFC 1256. Subtype To be assigned by IANA 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. Koodli, Perkins Expires 6 August 2007 [Page 18]
Internet Draft Fast Handovers for Mobile IPv4 6 February 2007 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. 5.5.2. Handover Acknowledge (HAck) The Handover Acknowledgment message is a new ICMP message that MUST be sent (typically by NAR to PAR) as a reply to the Handover Initiate (HI) (see section 5.5.1) message. Koodli, Perkins Expires 6 August 2007 [Page 19]
Internet Draft Fast Handovers for Mobile IPv4 6 February 2007 The message format and processing rules are identical to those defined in [1]. We only provide the format here for convenience. 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 8: 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. Time-to-Live At least 1. See RFC 1256. ICMP Fields: Koodli, Perkins Expires 6 August 2007 [Page 20]
Internet Draft Fast Handovers for Mobile IPv4 6 February 2007 Type To be assigned by IANA 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) 4: Handover Accepted, NCoA not assigned (used in Assigned addressing) 128: Handover Not Accepted, reason unspecified 129: Administratively prohibited 130: Insufficient resources Checksum The 16-bit one's complement of the one's complement sum of the ICMP message, start- ing with the ICMP Type. For computing the checksum, the Checksum and the Reserved fields are set to 0. See RFC 1256. Subtype To be assigned by IANA. 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. Koodli, Perkins Expires 6 August 2007 [Page 21]
Internet Draft Fast Handovers for Mobile IPv4 6 February 2007 6. Option formats The options in this section are specified as optional extensions for the HI and HAck messages, as well as for the Router Proxy Solicitation and Router Proxy Advertisement messages.. 6.1. Link-Layer Address Option Format 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 | Link-Layer Address ... +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Figure 9: Link-Layer Address Option Format Fields: Type 1 Mobile Node Link-layer Address 2 New Access Point Link-layer Address 3 NAR Link-layer Address Length The length of the option (including the type and length fields) in units of octets. For example, the length for IEEE 802 addresses is 1 [IPv6- ETHER]. Link-Layer Address The variable length link-layer address. Koodli, Perkins Expires 6 August 2007 [Page 22]
Internet Draft Fast Handovers for Mobile IPv4 6 February 2007 The content and format of this field (including byte and bit ordering) depends on the specific link-layer in use. 6.2. New IPv4 Address Option Format This option is used to provide the new router's IPv4 address in PrRtAdv. When it is also used to provide NCoA, it MUST appear after the new router's IPv4 address to distinguish the two addresses. 0 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Type | Length | Reserved | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | New IPv4 Address | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Figure 10: New IPv4 Address Option Format Fields: Type To be assigned by IANA Length The length of the option (including the type and length fields) in units of octets. Reserved Set to zero. Koodli, Perkins Expires 6 August 2007 [Page 23]
Internet Draft Fast Handovers for Mobile IPv4 6 February 2007 New IPv4 Address NAR's IPv4 address or the NCoA assigned by NAR. 6.3. New Router Prefix Information Option This option is the same as the ``Prefix-Lengths Extension'' in RFC 3344 (Section 2.1.2). 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 | Prefix-Length | Reserved | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Figure 11: New Router Prefix Information Option Format Fields: Type To be assigned by IANA Length 1 Prefix-Length The number of leading bits that define the network number of the corresponding Router's IP Address option. Koodli, Perkins Expires 6 August 2007 [Page 24]
Internet Draft Fast Handovers for Mobile IPv4 6 February 2007 Reserved Set to zero. 7. Security Considerations The FBU and FBack messages MUST be protected using a security association shared between a mobile node and its access router. In particular, the MN - PAR Authentication Extension MUST be present in each of these messages. Failure to include this extension can lead to a bogus node claiming a genuine mobile node's address and binding it to an arbitrary address. When the NCoA is NAR's address, there is no risk of a genuine mobile node misdirecting traffic, either inadvertently or intentionally, to an unsuspecting node on NAR's subnet. When NCoA is other than NAR's address, NAR MUST ensure that the proposed NCoA in HI is conflict-free, and MUST indicate the disposition in the HAck message. If there is a conflict, PAR MUST NOT tunnel packets to the address in question. Instead, PAR SHOULD tunnel packets to the address specified in HAck, if any is provided. 8. IANA Considerations All the messages and the option formats specified in this document require Type assignment from IANA. 9. Acknowledgement Thanks to all those who expressed interest in having a Fast Handovers for Mobile IPv4 protocol along the lines of [1]. Thanks to Vijay Devarapalli, Keng Leung, Alex Petrescu for their review and input. Koodli, Perkins Expires 6 August 2007 [Page 25]
Internet Draft Fast Handovers for Mobile IPv4 6 February 2007 Normative References [1] R. (Editor) Koodli. Fast Handovers for Mobile IPv6. Request for Comments 4068, Internet Engineering Task Force, July 2005. [2] C. Perkins (Editor). IP Mobility Support for IPv4. Request for Comments (Proposed Standard) 3344, Internet Engineering Task Force, August 2002. Informative References [3] The IEEE 802.21 group. http://www.ieee802.org/21. Technical report, IEEE. [4] IEEE Standard for Local and Metropolitan Area Networks: Port-Based Network Access Control. Technical report, IEEE. [5] IEEE Standard forLocal and Metropolitan Area Networks: Fast Roaming/Fast BSS Transition, the IEEE Task Group TGr. Technical report, IEEE. [6] R. Droms. Dynamic Host Configuration Protocol. Request for Comments (Draft Standard) 2131, Internet Engineering Task Force, March 1997. [7] C. Perkins and D. Johnson. Route Optimization in Mobile IP (work in progress). Internet Draft, Internet Engineering Task Force. draft-ietf-mobileip-optim-09.txt, February 2000. Questions about this memo can be directed to the authors: Rajeev Koodli Charles E. Perkins Nokia Research Center Nokia Research Center 975 Page Mill Road, 200 975 Page Mill Road, 200 Palo Alto, California 94304 Palo Alto, California 94304 USA USA Phone: +1-650 625-2359 Phone: +1-650 625-2986 EMail: rajeev.koodli@nokia.com EMail: charliep@iprg.nokia.com Fax: +1 650 625-2502 Fax: +1 650 625-2502 Koodli, Perkins Expires 6 August 2007 [Page 26]
Internet Draft Fast Handovers for Mobile IPv4 6 February 2007 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. Koodli, Perkins Expires 6 August 2007 [Page 27]
Internet Draft Fast Handovers for Mobile IPv4 6 February 2007 Copyright Statement Copyright (C) The IETF Trust (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, Perkins Expires 6 August 2007 [Page 28]
