RFC 8046
Host Mobility with the Host Identity Protocol
5. Processing Rules
This section describes rules for sending and receiving the LOCATOR_SET parameter, testing address reachability, and using CBA on UNVERIFIED locators.5.1. Locator Data Structure and Status
Each locator announced in a LOCATOR_SET parameter is represented by a piece of state that contains the following data: o the actual bit pattern representing the locator,
o the lifetime (seconds),
o the status (UNVERIFIED, ACTIVE, DEPRECATED),
o the Traffic Type scope of the locator, and
o whether the locator is preferred for any particular scope.
The status is used to track the reachability of the address embedded
within the LOCATOR_SET parameter:
UNVERIFIED: indicates that the reachability of the address has not
been verified yet,
ACTIVE: indicates that the reachability of the address has been
verified and the address has not been deprecated, and
DEPRECATED: indicates that the locator's lifetime has expired.
The following state changes are allowed:
UNVERIFIED to ACTIVE: The reachability procedure completes
successfully.
UNVERIFIED to DEPRECATED: The locator's lifetime expires while the
locator is UNVERIFIED.
ACTIVE to DEPRECATED: The locator's lifetime expires while the
locator is ACTIVE.
ACTIVE to UNVERIFIED: There has been no traffic on the address for
some time, and the local policy mandates that the address
reachability needs to be verified again before starting to use it
again.
DEPRECATED to UNVERIFIED: The host receives a new lifetime for the
locator.
A DEPRECATED address MUST NOT be changed to ACTIVE without first
verifying its reachability.
Note that the state of whether or not a locator is preferred is not
necessarily the same as the value of the preferred bit in the Locator
sub-parameter received from the peer. Peers may recommend certain
locators to be preferred, but the decision on whether to actually use
a locator as a preferred locator is a local decision, possibly
influenced by local policy.
In addition to state maintained about status and remaining lifetime for each locator learned from the peer, an implementation would typically maintain similar state about its own locators that have been offered to the peer. A locator lifetime that is unbounded (does not expire) can be signified by setting the value of the lifetime field to the maximum (unsigned) value. Finally, the locators used to establish the HIP association are by default assumed to be the initial preferred locators in ACTIVE state, with an unbounded lifetime.5.2. Sending the LOCATOR_SET
The decision of when to send the LOCATOR_SET is a local policy issue. However, it is RECOMMENDED that a host send a LOCATOR_SET whenever it recognizes a change of its IP addresses in use on an active HIP association and assumes that the change is going to last at least for a few seconds. Rapidly sending LOCATOR_SETs that force the peer to change the preferred address SHOULD be avoided. The sending of a new LOCATOR_SET parameter replaces the locator information from any previously sent LOCATOR_SET parameter; therefore, if a host sends a new LOCATOR_SET parameter, it needs to continue to include all active locators. Hosts MUST NOT announce broadcast or multicast addresses in LOCATOR_SETs. We now describe a few cases introduced in Section 3.2. We assume that the Traffic Type for each locator is set to "0" (other values for Traffic Type may be specified in documents that separate the HIP control plane from data-plane traffic). Other mobility cases are possible but are left for further study. 1. Host mobility with no multihoming and no rekeying. The mobile host creates a single UPDATE containing a single ESP_INFO with a single LOCATOR_SET parameter. The ESP_INFO contains the current value of the SPI in both the OLD SPI and NEW SPI fields. The LOCATOR_SET contains a single Locator with a Locator Type of "1"; the SPI MUST match that of the ESP_INFO. The preferred bit SHOULD be set and the "Locator Lifetime" is set according to local policy. The UPDATE also contains a SEQ parameter as usual. This packet is retransmitted as defined in the HIP specification [RFC7401]. The UPDATE should be sent to the peer's preferred IP address with an IP source address corresponding to the address in the LOCATOR_SET parameter.
2. Host mobility with no multihoming but with rekeying. The mobile
host creates a single UPDATE containing a single ESP_INFO with a
single LOCATOR_SET parameter (with a single address). The
ESP_INFO contains the current value of the SPI in the OLD SPI,
the new value of the SPI in the NEW SPI, and a KEYMAT Index as
selected by local policy. Optionally, the host may choose to
initiate a Diffie-Hellman rekey by including a DIFFIE_HELLMAN
parameter. The LOCATOR_SET contains a single Locator with a
Locator Type of "1"; the SPI MUST match that of the NEW SPI in
the ESP_INFO. Otherwise, the steps are identical to the case in
which no rekeying is initiated.
5.3. Handling Received LOCATOR_SETs
A host SHOULD be prepared to receive a single LOCATOR_SET parameter
in a HIP UPDATE packet. Reception of multiple LOCATOR_SET parameters
in a single packet, or in HIP packets other than UPDATE, is outside
of the scope of this specification.
Because a host sending the LOCATOR_SET may send the same parameter in
different UPDATE messages to different destination addresses,
including possibly the RVS of the host, the host receiving the
LOCATOR_SET MUST be prepared to handle the possibility of duplicate
LOCATOR_SETs sent to more than one of the host's addresses. As a
result, the host MUST detect and avoid reprocessing a LOCATOR_SET
parameter that is redundant with a LOCATOR_SET parameter that has
been recently received and processed.
This document describes sending both ESP_INFO and LOCATOR_SET
parameters in an UPDATE. The ESP_INFO parameter is included when
there is a need to rekey or key a new SPI, and is otherwise included
for the possible benefit of HIP-aware NATs and firewalls. The
LOCATOR_SET parameter contains a complete listing of the locators
that the host wishes to make or keep active for the HIP association.
In general, the processing of a LOCATOR_SET depends upon the packet
type in which it is included. Here, we describe only the case in
which ESP_INFO is present and a single LOCATOR_SET and ESP_INFO are
sent in an UPDATE message; other cases are for further study. The
steps below cover each of the cases described in Section 5.2.
The processing of ESP_INFO and LOCATOR_SET parameters is intended to
be modular and support future generalization to the inclusion of
multiple ESP_INFO and/or multiple LOCATOR_SET parameters. A host
SHOULD first process the ESP_INFO before the LOCATOR_SET, since the
ESP_INFO may contain a new SPI value mapped to an existing SPI, while
a Locator Type of "1" will only contain a reference to the new SPI.
When a host receives a validated HIP UPDATE with a LOCATOR_SET and
ESP_INFO parameter, it processes the ESP_INFO as follows. The
ESP_INFO parameter indicates whether an SA is being rekeyed, created,
deprecated, or just identified for the benefit of HIP-aware NATs and
firewalls. The host examines the OLD SPI and NEW SPI values in the
ESP_INFO parameter:
1. (no rekeying) If the OLD SPI is equal to the NEW SPI and both
correspond to an existing SPI, the ESP_INFO is gratuitous
(provided for HIP-aware NATs and firewalls) and no rekeying is
necessary.
2. (rekeying) If the OLD SPI indicates an existing SPI and the NEW
SPI is a different non-zero value, the existing SA is being
rekeyed and the host follows HIP ESP rekeying procedures by
creating a new outbound SA with an SPI corresponding to the NEW
SPI, with no addresses bound to this SPI. Note that locators in
the LOCATOR_SET parameter will reference this new SPI instead of
the old SPI.
3. (new SA) If the OLD SPI value is zero and the NEW SPI is a new
non-zero value, then a new SA is being requested by the peer.
This case is also treated like a rekeying event; the receiving
host MUST create a new SA and respond with an UPDATE ACK.
4. (deprecating the SA) If the OLD SPI indicates an existing SPI and
the NEW SPI is zero, the SA is being deprecated and all locators
uniquely bound to the SPI are put into the DEPRECATED state.
If none of the above cases apply, a protocol error has occurred and
the processing of the UPDATE is stopped.
Next, the locators in the LOCATOR_SET parameter are processed. For
each locator listed in the LOCATOR_SET parameter, check that the
address therein is a legal unicast or anycast address. That is, the
address MUST NOT be a broadcast or multicast address. Note that some
implementations MAY accept addresses that indicate the local host,
since it may be allowed that the host runs HIP with itself.
The below assumes that all Locators are of Type "1" with a Traffic
Type of "0"; other cases are for further study.
For each Type "1" address listed in the LOCATOR_SET parameter, the
host checks whether the address is already bound to the SPI
indicated. If the address is already bound, its lifetime is updated.
If the status of the address is DEPRECATED, the status is changed to
UNVERIFIED. If the address is not already bound, the address is
added, and its status is set to UNVERIFIED. Mark all addresses corresponding to the SPI that were NOT listed in the LOCATOR_SET parameter as DEPRECATED. As a result, at the end of processing, the addresses listed in the LOCATOR_SET parameter have a state of either UNVERIFIED or ACTIVE, and any old addresses on the old SA not listed in the LOCATOR_SET parameter have a state of DEPRECATED. Once the host has processed the locators, if the LOCATOR_SET parameter contains a new preferred locator, the host SHOULD initiate a change of the preferred locator. This requires that the host first verify reachability of the associated address, and only then change the preferred locator; see Section 5.5. If a host receives a locator with an unsupported Locator Type, and when such a locator is also declared to be the preferred locator for the peer, the host SHOULD send a NOTIFY error with a Notify Message Type of LOCATOR_TYPE_UNSUPPORTED, with the Notification Data field containing the locator(s) that the receiver failed to process. Otherwise, a host MAY send a NOTIFY error if a (non-preferred) locator with an unsupported Locator Type is received in a LOCATOR_SET parameter. A host MAY add the source IP address of a received HIP packet as a candidate locator for the peer even if it is not listed in the peer's LOCATOR_SET, but it SHOULD prefer locators explicitly listed in the LOCATOR_SET.5.4. Verifying Address Reachability
A host MUST verify the reachability of an UNVERIFIED address. The status of a newly learned address MUST initially be set to UNVERIFIED unless the new address is advertised in an R1 packet as a new preferred locator. A host MAY also want to verify the reachability of an ACTIVE address again after some time, in which case it would set the status of the address to UNVERIFIED and reinitiate address verification. A typical verification that is protected by retransmission timers is to include an ECHO REQUEST within an UPDATE sent to the new address. A host typically starts the address-verification procedure by sending a nonce to the new address. A host MAY choose from different message exchanges or different nonce values so long as it establishes that the peer has received and replied to the nonce at the new address.
For example, when the host is changing its SPI and sending an ESP_INFO to the peer, the NEW SPI value SHOULD be random and the random value MAY be copied into an ECHO_REQUEST sent in the rekeying UPDATE. However, if the host is not changing its SPI, it MAY still use the ECHO_REQUEST parameter for verification but with some other random value. A host MAY also use other message exchanges as confirmation of the address reachability. In some cases, it MAY be sufficient to use the arrival of data on a newly advertised SA as implicit address reachability verification as depicted in Figure 7, instead of waiting for the confirmation via a HIP packet. In this case, a host advertising a new SPI as part of its address reachability check SHOULD be prepared to receive traffic on the new SA. Mobile Host Peer Host UPDATE(ESP_INFO, LOCATOR_SET, ...) ----------------------------------> prepare incoming SA UPDATE(ESP_INFO, ...) with new SPI <----------------------------------- switch to new outgoing SA data on new SA -----------------------------------> mark address ACTIVE UPDATE(ACK, ECHO_RESPONSE) later arrives -----------------------------------> Figure 7: Address Activation via Use of a New SA When address verification is in progress for a new preferred locator, the host SHOULD select a different locator listed as ACTIVE, if one such locator is available, to continue communications until address verification completes. Alternatively, the host MAY use the new preferred locator while in UNVERIFIED status to the extent CBA permits. CBA is explained in Section 5.6. Once address verification succeeds, the status of the new preferred locator changes to ACTIVE.
5.5. Changing the Preferred Locator
A host MAY want to change the preferred outgoing locator for different reasons, e.g., because traffic information or ICMP error messages indicate that the currently used preferred address may have become unreachable. Another reason may be due to receiving a LOCATOR_SET parameter that has the "P" bit set. To change the preferred locator, the host initiates the following procedure: 1. If the new preferred locator has an ACTIVE status, the preferred locator is changed and the procedure succeeds. 2. If the new preferred locator has an UNVERIFIED status, the host starts to verify its reachability. The host SHOULD use a different locator listed as ACTIVE until address verification completes if one such locator is available. Alternatively, the host MAY use the new preferred locator, even though in UNVERIFIED status, to the extent CBA permits. Once address verification succeeds, the status of the new preferred locator changes to ACTIVE, and its use is no longer governed by CBA. 3. If the peer host has not indicated a preference for any address, then the host picks one of the peer's ACTIVE addresses randomly or according to local policy. This case may arise if, for example, ICMP error messages that deprecate the preferred locator arrive, but the peer has not yet indicated a new preferred locator. 4. If the new preferred locator has a DEPRECATED status and there is at least one non-deprecated address, the host selects one of the non-deprecated addresses as a new preferred locator and continues. If the selected address is UNVERIFIED, the address verification procedure described above will apply.5.6. Credit-Based Authorization
To prevent redirection-based flooding attacks, the use of a CBA approach MUST be used when a host sends data to an UNVERIFIED locator. The following algorithm addresses the security considerations for prevention of amplification and time-shifting attacks. Other forms of credit aging, and other values for the CreditAgingFactor and CreditAgingInterval parameters in particular, are for further study, and so are the advanced CBA techniques specified in [CBA-MIPv6].
5.6.1. Handling Payload Packets
A host maintains a "credit counter" for each of its peers. Whenever a packet arrives from a peer, the host SHOULD increase that peer's credit counter by the size of the received packet. When the host has a packet to be sent to the peer, and when the peer's preferred locator is listed as UNVERIFIED and no alternative locator with status ACTIVE is available, the host checks whether it can send the packet to the UNVERIFIED locator. The packet SHOULD be sent if the value of the credit counter is higher than the size of the outbound packet. If the credit counter is too low, the packet MUST be discarded or buffered until address verification succeeds. When a packet is sent to a peer at an UNVERIFIED locator, the peer's credit counter MUST be reduced by the size of the packet. The peer's credit counter is not affected by packets that the host sends to an ACTIVE locator of that peer. Figure 8 depicts the actions taken by the host when a packet is received. Figure 9 shows the decision chain in the event a packet is sent. Inbound Packet | | +----------------+ +---------------+ | | Increase | | Deliver | +-----> | credit counter |-------------> | packet to | | by packet size | | application | +----------------+ +---------------+ Figure 8: Receiving Packets with Credit-Based Authorization
Outbound Packet | _________________ | / \ +---------------+ | / Is the preferred \ No | Send packet | +-----> | destination address |-------------> | to preferred | \ UNVERIFIED? / | address | \_________________/ +---------------+ | | Yes | v _________________ / \ +---------------+ / Does an ACTIVE \ Yes | Send packet | | destination address |-------------> | to ACTIVE | \ exist? / | address | \_________________/ +---------------+ | | No | v _________________ / \ +---------------+ / Is credit counter \ No | | | >= |-------------> | Drop or | \ packet size? / | buffer packet | \_________________/ +---------------+ | | Yes | v +---------------+ +---------------+ | Reduce credit | | Send packet | | counter by |----------------> | to preferred | | packet size | | address | +---------------+ +---------------+ Figure 9: Sending Packets with Credit-Based Authorization
5.6.2. Credit Aging
A host ensures that the credit counters it maintains for its peers gradually decrease over time. Such "credit aging" prevents a malicious peer from building up credit at a very slow speed and using this, all at once, for a severe burst of redirected packets. Credit aging may be implemented by multiplying credit counters with a factor, CreditAgingFactor (a fractional value less than one), in fixed-time intervals of CreditAgingInterval length. Choosing appropriate values for CreditAgingFactor and CreditAgingInterval is important to ensure that a host can send packets to an address in state UNVERIFIED even when the peer sends at a lower rate than the host itself. When CreditAgingFactor or CreditAgingInterval are too small, the peer's credit counter might be too low to continue sending packets until address verification concludes. The parameter values proposed in this document are as follows: CreditAgingFactor 7/8 CreditAgingInterval 5 seconds These parameter values work well when the host transfers a file to the peer via a TCP connection, and the end-to-end round-trip time does not exceed 500 milliseconds. Alternative credit-aging algorithms may use other parameter values or different parameters, which may even be dynamically established.6. Security Considerations
The HIP mobility mechanism provides a secure means of updating a host's IP address via HIP UPDATE packets. Upon receipt, a HIP host cryptographically verifies the sender of an UPDATE, so forging or replaying a HIP UPDATE packet is very difficult (see [RFC7401]). Therefore, security issues reside in other attack domains. The two we consider are malicious redirection of legitimate connections as well as redirection-based flooding attacks using this protocol. This can be broken down into the following: 1) Impersonation attacks - direct conversation with the misled victim - man-in-the-middle (MitM) attack
2) Denial-of-service (DoS) attacks
- flooding attacks (== bandwidth-exhaustion attacks)
* tool 1: direct flooding
* tool 2: flooding by botnets
* tool 3: redirection-based flooding
- memory-exhaustion attacks
- computational-exhaustion attacks
3) Privacy concerns
We consider these in more detail in the following sections.
In Sections 6.1 and 6.2, we assume that all users are using HIP. In
Section 6.3, we consider the security ramifications when we have both
HIP and non-HIP hosts.
6.1. Impersonation Attacks
An attacker wishing to impersonate another host will try to mislead
its victim into directly communicating with them or carry out a MitM
attack between the victim and the victim's desired communication
peer. Without mobility support, such attacks are possible only if
the attacker resides on the routing path between its victim and the
victim's desired communication peer or if the attacker tricks its
victim into initiating the connection over an incorrect routing path
(e.g., by acting as a router or using spoofed DNS entries).
The HIP extensions defined in this specification change the situation
in that they introduce an ability to redirect a connection, both
before and after establishment. If no precautionary measures are
taken, an attacker could potentially misuse the redirection feature
to impersonate a victim's peer from any arbitrary location. However,
the authentication and authorization mechanisms of the HIP base
exchange [RFC7401] and the signatures in the UPDATE message prevent
this attack. Furthermore, ownership of a HIP association is securely
linked to a HIP HI/HIT. If an attacker somehow uses a bug in the
implementation to redirect a HIP connection, the original owner can
always reclaim their connection (they can always prove ownership of
the private key associated with their public HI).
MitM attacks are possible if an on-path attacker is present during the initial HIP base exchange and if the hosts do not authenticate each other's identities. However, once such an opportunistic base exchange has taken place, a MitM attacker that comes later to the path cannot steal the HIP connection because it is very difficult for an attacker to create an UPDATE packet (or any HIP packet) that will be accepted as a legitimate update. UPDATE packets use HMAC and are signed. Even when an attacker can snoop packets to obtain the SPI and HIT/HI, they still cannot forge an UPDATE packet without knowledge of the secret keys. Also, replay attacks on the UPDATE packet are prevented as described in [RFC7401].6.2. Denial-of-Service Attacks
6.2.1. Flooding Attacks
The purpose of a DoS attack is to exhaust some resource of the victim such that the victim ceases to operate correctly. A DoS attack can aim at the victim's network attachment (flooding attack), its memory, or its processing capacity. In a flooding attack, the attacker causes an excessive number of bogus or unwanted packets to be sent to the victim, which fills their available bandwidth. Note that the victim does not necessarily need to be a node; it can also be an entire network. The attack functions the same way in either case. An effective DoS strategy is distributed denial of service (DDoS). Here, the attacker conventionally distributes some viral software to as many nodes as possible. Under the control of the attacker, the infected nodes (e.g., nodes in a botnet) jointly send packets to the victim. With such an "army", an attacker can take down even very high bandwidth networks/victims. With the ability to redirect connections, an attacker could realize a DDoS attack without having to distribute viral code. Here, the attacker initiates a large download from a server and subsequently uses the HIP mobility mechanism to redirect this download to its victim. The attacker can repeat this with multiple servers. This threat is mitigated through reachability checks and CBA. When conducted using HIP, reachability checks can leverage the built-in authentication properties of HIP. They can also prevent redirection- based flooding attacks. However, the delay of such a check can have a noticeable impact on application performance. To reduce the impact of the delay, CBA can be used to send a limited number of packets to the new address while the validity of the IP address is still in question. Both strategies do not eliminate flooding attacks per se, but they preclude: (i) their use from a location off the path towards the flooded victim; and (ii) any amplification in the number and size
of the redirected packets. As a result, the combination of a reachability check and CBA lowers a HIP redirection-based flooding attack to the level of a direct flooding attack in which the attacker itself sends the flooding traffic to the victim.6.2.2. Memory/Computational-Exhaustion DoS Attacks
We now consider whether or not the proposed extensions to HIP add any new DoS attacks (consideration of DoS attacks using the base HIP exchange and updates is discussed in [RFC7401]). A simple attack is to send many UPDATE packets containing many IP addresses that are not flagged as preferred. The attacker continues to send such packets until the number of IP addresses associated with the attacker's HI crashes the system. Therefore, a HIP association SHOULD limit the number of IP addresses that can be associated with any HI. Other forms of memory/computationally exhausting attacks via the HIP UPDATE packet are handled in the base HIP document [RFC7401]. A central server that has to deal with a large number of mobile clients MAY consider increasing the SA lifetimes to try to slow down the rate of rekeying UPDATEs or increasing the cookie difficulty to slow down the rate of attack-oriented connections.6.3. Mixed Deployment Environment
We now assume an environment with hosts that are both HIP and non-HIP aware. Four cases exist: 1. A HIP host redirects its connection onto a non-HIP host. The non-HIP host will drop the reachability packet, so this is not a threat unless the HIP host is a MitM that could somehow respond successfully to the reachability check. 2. A non-HIP host attempts to redirect their connection onto a HIP host. This falls into IPv4 and IPv6 security concerns, which are outside the scope of this document. 3. A non-HIP host attempts to steal a HIP host's session (assume that Secure Neighbor Discovery is not active for the following). The non-HIP host contacts the service that a HIP host has a connection with and then attempts to change its IP address to steal the HIP host's connection. What will happen in this case is implementation dependent, but such a request should fail by being ignored or dropped. Even if the attack were successful, the HIP host could reclaim its connection via HIP.
4. A HIP host attempts to steal a non-HIP host's session. A HIP
host could spoof the non-HIP host's IP address during the base
exchange or set the non-HIP host's IP address as its preferred
address via an UPDATE. Other possibilities exist, but a solution
is to prevent the local redirection of sessions that were
previously using an unverified address, but outside of the
existing HIP context, into the HIP SAs until the address change
can be verified.
6.4. Privacy Concerns
The exposure of a host's IP addresses through HIP mobility extensions
may raise privacy concerns. The administrator of a host may be
trying to hide its location in some context through the use of a VPN
or other virtual interfaces. Similar privacy issues also arise in
other frameworks such as WebRTC and are not specific to HIP.
Implementations SHOULD provide a mechanism to allow the host
administrator to block the exposure of selected addresses or address
ranges. While this issue may be more relevant in a host multihoming
scenario in which multiple IP addresses might be exposed [RFC8047],
it is worth noting also here that mobility events might cause an
implementation to try to inadvertently use a locator that the
administrator would rather avoid exposing to the peer host.
7. IANA Considerations
[RFC5206], obsoleted by this document, specified an allocation for a
LOCATOR parameter in the "Parameter Types" subregistry of the "Host
Identity Protocol (HIP) Parameters" registry, with a type value of
193. IANA has renamed the parameter to "LOCATOR_SET" and has updated
the reference from [RFC5206] to this specification.
[RFC5206], obsoleted by this document, specified an allocation for a
LOCATOR_TYPE_UNSUPPORTED type in the "Notify Message Types" registry,
with a type value of 46. IANA has updated the reference from
[RFC5206] to this specification.
8. Differences from RFC 5206
This section summarizes the technical changes made from [RFC5206].
This section is informational, intended to help implementors of the
previous protocol version. If any text in this section contradicts
text in other portions of this specification, the text found outside
of this section should be considered normative.
This document specifies extensions to the HIP Version 2 protocol, while [RFC5206] specifies extensions to the HIP Version 1 protocol. [RFC7401] documents the differences between these two protocol versions. [RFC5206] included procedures for both HIP host mobility and basic host multihoming. In this document, only host mobility procedures are included; host multihoming procedures are now specified in [RFC8047]. In particular, multihoming-related procedures related to the exposure of multiple locators in the base exchange packets; the transmission, reception, and processing of multiple locators in a single UPDATE packet; handovers across IP address families; and other multihoming-related specifications have been removed. The following additional changes have been made: o The LOCATOR parameter in [RFC5206] has been renamed to LOCATOR_SET. o Specification text regarding the handling of mobility when both hosts change IP addresses at nearly the same time (a "double-jump" mobility scenario) has been added. o Specification text regarding the mobility event in which the host briefly has an active new locator and old locator at the same time (a "make-before-break" mobility scenario) has been added. o Specification text has been added to note that a host may add the source IP address of a received HIP packet as a candidate locator for the peer even if it is not listed in the peer's LOCATOR_SET, but that it should prefer locators explicitly listed in the LOCATOR_SET. o This document clarifies that the HOST_ID parameter may be included in UPDATE messages containing LOCATOR_SET parameters, for the possible benefit of HIP-aware firewalls. o The previous specification mentioned that it may be possible to include multiple LOCATOR_SET and ESP_INFO parameters in an UPDATE. This document only specifies the case of a single LOCATOR_SET and ESP_INFO parameter in an UPDATE. o The previous specification mentioned that it may be possible to send LOCATOR_SET parameters in packets other than the UPDATE. This document only specifies the use of the UPDATE packet. o This document describes a simple heuristic for setting the credit value for CBA.
o This specification mandates that a host must be able to receive
and avoid reprocessing redundant LOCATOR_SET parameters that may
have been sent in parallel to multiple addresses of the host.
9. References
9.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997,
<http://www.rfc-editor.org/info/rfc2119>.
[RFC4291] Hinden, R. and S. Deering, "IP Version 6 Addressing
Architecture", RFC 4291, DOI 10.17487/RFC4291, February
2006, <http://www.rfc-editor.org/info/rfc4291>.
[RFC7401] Moskowitz, R., Ed., Heer, T., Jokela, P., and T.
Henderson, "Host Identity Protocol Version 2 (HIPv2)",
RFC 7401, DOI 10.17487/RFC7401, April 2015,
<http://www.rfc-editor.org/info/rfc7401>.
[RFC7402] Jokela, P., Moskowitz, R., and J. Melen, "Using the
Encapsulating Security Payload (ESP) Transport Format with
the Host Identity Protocol (HIP)", RFC 7402,
DOI 10.17487/RFC7402, April 2015,
<http://www.rfc-editor.org/info/rfc7402>.
[RFC8003] Laganier, J. and L. Eggert, "Host Identity Protocol (HIP)
Registration Extension", RFC 8003, DOI 10.17487/RFC8003,
October 2016, <http://www.rfc-editor.org/info/rfc8003>.
[RFC8004] Laganier, J. and L. Eggert, "Host Identity Protocol (HIP)
Rendezvous Extension", RFC 8004, DOI 10.17487/RFC8004,
October 2016, <http://www.rfc-editor.org/info/rfc8004>.
9.2. Informative References
[CBA-MIPv6]
Vogt, C. and J. Arkko, "Credit-Based Authorization for
Mobile IPv6 Early Binding Updates", Work in Progress,
draft-vogt-mobopts-credit-based-authorization-00, February
2005.
[RFC4225] Nikander, P., Arkko, J., Aura, T., Montenegro, G., and E.
Nordmark, "Mobile IP Version 6 Route Optimization Security
Design Background", RFC 4225, DOI 10.17487/RFC4225,
December 2005, <http://www.rfc-editor.org/info/rfc4225>.
[RFC5206] Nikander, P., Henderson, T., Ed., Vogt, C., and J. Arkko, "End-Host Mobility and Multihoming with the Host Identity Protocol", RFC 5206, DOI 10.17487/RFC5206, April 2008, <http://www.rfc-editor.org/info/rfc5206>. [RFC5207] Stiemerling, M., Quittek, J., and L. Eggert, "NAT and Firewall Traversal Issues of Host Identity Protocol (HIP) Communication", RFC 5207, DOI 10.17487/RFC5207, April 2008, <http://www.rfc-editor.org/info/rfc5207>. [RFC8047] Henderson, T., Ed., Vogt, C., and J. Arkko, "Host Multihoming with the Host Identity Protocol", RFC 8047, DOI 10.17487/RFC8047, February 2017, <http://www.rfc-editor.org/info/rfc8047>. [SIMPLE-CBA] Vogt, C. and J. Arkko, "Credit-Based Authorization for Concurrent Reachability Verification", Work in Progress, draft-vogt-mobopts-simple-cba-00, February 2006.Acknowledgments
Pekka Nikander and Jari Arkko originated this document; Christian Vogt and Thomas Henderson (editor) later joined as coauthors. Greg Perkins contributed the initial text of the security section. Petri Jokela was a coauthor of the initial individual submission. CBA was originally introduced in [SIMPLE-CBA], and portions of this document have been adopted from that earlier document. The authors thank Jeff Ahrenholz, Baris Boyvat, Rene Hummen, Miika Komu, Mika Kousa, Jan Melen, and Samu Varjonen for improvements to the document.
Authors' Addresses
Thomas R. Henderson (editor) University of Washington Campus Box 352500 Seattle, WA United States of America Email: tomhend@u.washington.edu Christian Vogt Independent 3473 North First Street San Jose, CA 95134 United States of America Email: mail@christianvogt.net Jari Arkko Ericsson Jorvas, FIN-02420 Finland Phone: +358 40 5079256 Email: jari.arkko@piuha.net