Internet DRAFT - draft-moskowitz-hip-fast-mobility
draft-moskowitz-hip-fast-mobility
HIP R. Moskowitz
Internet-Draft HTT Consulting
Updates: 8046 (if approved) S. Card
Intended status: Standards Track A. Wiethuechter
Expires: 9 June 2024 AX Enterprize
7 December 2023
Fast HIP Host Mobility
draft-moskowitz-hip-fast-mobility-07
Abstract
This document describes mobility scenarios and how to aggressively
support them in HIP. The goal is minimum lag in the mobility event.
Status of This Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
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This Internet-Draft will expire on 9 June 2024.
Copyright Notice
Copyright (c) 2023 IETF Trust and the persons identified as the
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Terms and Definitions . . . . . . . . . . . . . . . . . . . . 3
2.1. Requirements Terminology . . . . . . . . . . . . . . . . 3
2.2. Definitions . . . . . . . . . . . . . . . . . . . . . . . 3
3. Problem Space . . . . . . . . . . . . . . . . . . . . . . . . 3
3.1. Time to complete move . . . . . . . . . . . . . . . . . . 3
3.2. Apriori move knowledge . . . . . . . . . . . . . . . . . 4
4. Enhanced availability of VIA_RVS . . . . . . . . . . . . . . 4
5. Single move mobility . . . . . . . . . . . . . . . . . . . . 5
5.1. Piggybacking impact on transport window size . . . . . . 5
5.2. Environment . . . . . . . . . . . . . . . . . . . . . . . 5
5.3. Scenario 1: Neither host has data to transmit . . . . . . 5
5.4. Scenario 2: Host A has data to transmit . . . . . . . . . 5
5.4.1. IPv6 datagram + HIP UPDATE > MTU . . . . . . . . . . 5
5.4.2. IPv6 datagram + HIP UPDATE <= MTU . . . . . . . . . . 6
5.5. Scenario 3: Host B has data to transmit . . . . . . . . . 6
5.5.1. IPv6 datagram + HIP UPDATE > MTU . . . . . . . . . . 6
5.5.2. IPv6 datagram + HIP UPDATE <= MTU . . . . . . . . . . 6
6. Double-Jump mobility . . . . . . . . . . . . . . . . . . . . 7
6.1. Environment . . . . . . . . . . . . . . . . . . . . . . . 7
6.2. Shotgunning UPDATEs . . . . . . . . . . . . . . . . . . . 7
6.3. Neither host has data to transmit . . . . . . . . . . . . 7
6.4. Either host has data to transmit . . . . . . . . . . . . 7
6.4.1. IPv6 datagram + HIP UPDATE > MTU . . . . . . . . . . 8
6.4.2. IPv6 datagram + HIP UPDATE <= MTU . . . . . . . . . . 8
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 8
8. Security Considerations . . . . . . . . . . . . . . . . . . . 8
9. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 8
10. References . . . . . . . . . . . . . . . . . . . . . . . . . 8
10.1. Normative References . . . . . . . . . . . . . . . . . . 8
10.2. Informative References . . . . . . . . . . . . . . . . . 9
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 9
1. Introduction
This document expands on HIP Host Mobility [RFC8046] to describe a
set of mobility scenarios that can be addressed by mechanisms that
accelerate the basic HIP mobility UPDATE exchange.
HIP Host Mobility [RFC8046] performs a return address validation to
ensure that the UPDATE address is reachable by the peer. Two reasons
are given for this approach: middleboxes blocking return reachability
and malicious peers providing false address updates to flood a
target.
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The approach here is to start using the new address while it is being
validated. Worst case is a few packets are lost or sent to a wrong
target. These are acceptable risks while gaining a fast address
update that works in most cases.
One mechanism used is to piggyback data using Next Header even while
the mobile peer address is flagged UNVERIFIED. This is practical as
the new peer address is authenticated by the HIP_MAC in UPDATE. The
UPDATE can neither be forged nor can it be replayed. The
verification is more to ensure reverse reachability particularly
across NATs and firewalls.
Another mechanism expands the use of the VIA_RVS parameter to
"shotgun" mobility UPDATEs. These and other optimizations will be
covered in detail.
2. Terms and Definitions
2.1. Requirements Terminology
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
"OPTIONAL" in this document are to be interpreted as described in BCP
14 [RFC2119] [RFC8174] when, and only when, they appear in all
capitals, as shown here.
2.2. Definitions
MTU
The Maximum Transmit Unit or maximum number of bytes in a datagram
that the Interface supports.
Rendezvous Server (RVS)
A HIP registrar providing rendezvous service.
SPI
The Security Parameter Index.
3. Problem Space
3.1. Time to complete move
Most mobility environments are built with a "break then make" model
for connectivity. Thus there is measurable time between the old
address being unusable and the new address being functional. Adding
mobility convergence times just further aggravates the delay which
negatively impacts the user experience.
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The "make then break" model for connectivity is supported via HIP
multihoming and is the subject of a separate recommendation.
HIP mobility relies on a 3 packet UPDATE exchange which in some cases
can be optimized to 2 packets. This can be further delayed in a
"double-jump" scenario with waiting for the direct connection to fail
before falling over to contacting the peer's Rendezvous Server (RVS).
These processes have resulted in other technologies to be preferred
over HIP as they have faster convergence even if they achieve this
while sacrificing security.
3.2. Apriori move knowledge
A HIP Host that has the potential to 'move' (acquire a new address
for an interface) during the lifetime of a HIP association SHOULD be
registered to an RVS. Such a HIP host SHOULD always inform its peer
of its RVS address, as it may experience a "Double-Jump" move as in
Section 6.
In an RVS assisted base exchange, the Responder ensures the Initiator
knows its RVS with the VIA_RVS parameter in the R1 as specified in
HIP Rendezvous Extension [RFC8004]. However, the Responder has no
mechanism to learn the Initiator's RVS address. Additionally, it is
possible for an Initiator to directly contact the Responder and thus
not learn about the Responder's RVS in the base exchange.
A host may not publish its RVS if it does not wish to be easily
discovered. It still should notify its peers of its RVS if it
expects to be found in some move scenarios.
The HIP base exchange needs to include more RVS information.
4. Enhanced availability of VIA_RVS
The VIA_RVS parameter is defined in HIP Rendezvous Extension
[RFC8004] for use in R1, but only identifies the Responder's RVS to
the Initiator when the I1 was routed through the RVS.
Firstly, a Responder SHOULD always provide its VIA_RVS information in
R1 even when the I1 came directly from the Initiator. Secondly, the
Initiator SHOULD always provide its VIA_RVS information in I2. The
VIA_RVS address is always maintained as part of the HIT to IP
addressing information. Through these two expansions in the
availability of VIA_RVS, the hosts are assured to possess their
peer's RVS address to "shotgun" UPDATEs and thus accelerate mobility.
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5. Single move mobility
Data traffic between host A and B may use ESP with HIP [RFC7402] or
any other tunneling protocol. In ESP the relationship of the tunnel
SAs with the HIP SA puts a high level of trust on the following fast
mobility.
5.1. Piggybacking impact on transport window size
The following sections define the operation of a HIP UPDATE payload
followed by some transport (e.g. TCP or UDP) payload in a single IP
datagram. This multicontent IP datagram works best with a smaller
window size for the higher layer. The normal operation is to compare
the size of the transport datagram plus HIP UPDATE payload and ensure
it is less than the MTU. An implementation may be able to adjust the
transport window size downward so that the higher layer could still
fill it and the whole piece then still fit within the MTU.
5.2. Environment
* Host A is mobile.
* Host B may be mobile, but not changing IP address at this time.
* Only Host A is moving in the network and changing its IP address.
* Host A and B share a HIP Security Association.
* Host A and B are registered to a RVS server, not necessarily the
same and each has the others RVS address.
5.3. Scenario 1: Neither host has data to transmit
Host A triggers a HIP mobility UPDATE with Locator to inform Host B
of new address. Host B, upon validating Host A HIP UPDATE, continues
with Address Verification.
5.4. Scenario 2: Host A has data to transmit
5.4.1. IPv6 datagram + HIP UPDATE > MTU
Host A triggers a HIP mobility UPDATE with Locator to inform Host B
of new address. As the UPDATE + datagram would exceed the MTU, the
datagram is sent separately after receipt of the HIP UPDATE from Host
B.
The HIP UPDATE packets vary in length as follows:
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Move notification: 302 bytes - UPDATE(ESP_INFO, LOCATOR, SEQ, HMAC,
HIP_SIGNATURE)
Move verification: 286 bytes - UPDATE(ESP_INFO, SEQ, ACK, HMAC,
HIP_SIGNATURE, ECHO_REQUEST_UNSIGNED)
Verification ack: 262 bytes - UPDATE(ESP_INFO, ACK, HMAC,
HIP_SIGNATURE, ECHO_RESPONSE_UNSIGNED)
5.4.2. IPv6 datagram + HIP UPDATE <= MTU
Host A sends HIP UPDATE with Locator to inform Host B of new address.
Datagram is appended to HIP UPDATE using Next Header. Host B, upon
validating Host A HIP UPDATE, sends next header to proper module and
continues with Address Verification. This datagram is processed even
though the address is UNVERIFIED.
The ESP anti-replay window managed by its envelope sequence number
can protect against replayed UPDATE+ESP packets prior to address
verification.
5.5. Scenario 3: Host B has data to transmit
After Host B receives a HIP mobility UPDATE from A it has data to
send to A. Or Host B may have been sending data to Host A while Host
A was moving. The old data may have been lost; for example the data
is over UDP with no keepalives during the move time. The old data
may be in a retransmission state; for example the data is over TCP.
Or the data reached the interface from the higher layer at the same
time that the HIP UPDATE with new locator was successfully processed.
5.5.1. IPv6 datagram + HIP UPDATE > MTU
Host B sends the HIP UPDATE validation followed by the IPv6 datagram.
Host B may place the address in ACTIVE state or wait from HIP UPDATE
confirmation from Host A.
5.5.2. IPv6 datagram + HIP UPDATE <= MTU
Host B sends the HIP UPDATE validation within the IPv6 datagram.
Host B may place the address in ACTIVE state or wait from HIP UPDATE
confirmation from Host A.
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6. Double-Jump mobility
The HIP mobility UPDATE will fail without the use of RVS. In fact
both RVS are needed for both UPDATEs to find its peer. This is why
the "shotgun" acceleration SHOULD always be used when the peer's RVS
is known.
6.1. Environment
* Both host A and B are mobile.
* Host A and B share a HIP Security Association.
* Both hosts move in the network and change their IP addresses.
Before either receives the others HIP mobility UPDATE.
* Host A and B are registered to a RVS server, not necessarily the
same and each has the others RVS address.
6.2. Shotgunning UPDATEs
Shotgunning is the process of sending the same UPDATE to more than
one LOCATOR. In particular it refers to sending the UPDATE to at
least the peer's last known IP address and to its RVS address learned
from the VIA_RVS for either the R1 or I2 packet.
A host MUST be prepared to receive and discard multiple HIP mobility
UPDATEs. The duplicates will be readily identified as having the
same SEQ (UPDATE sequence number).
Shotgunning SHOULD always be used when an RVS is known. A peer never
knows of a "double-jump" event until after it receives its peer's
UPDATE.
6.3. Neither host has data to transmit
Host A triggers a HIP mobility UPDATE with Locator to inform Host B
of new address. Host B, upon validating Host A HIP UPDATE, continues
with Address Verification.
No attempt should be made to piggyback the two UPDATE processes.
They may run simultaneously but not in the same IP datagrams.
6.4. Either host has data to transmit
The following acceleration advice presents a number of challenges.
The best rule of thumb is to send the data as soon as possible.
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6.4.1. IPv6 datagram + HIP UPDATE > MTU
Same process as Section 6.3
6.4.2. IPv6 datagram + HIP UPDATE <= MTU
Host A sends HIP UPDATE with Locator to inform Host B of new address.
Datagram is appended to HIP UPDATE using Next Header. Host B, may
have already sent a datagram with its original HIP UPDATE. If since
then a receipt of Host A's UPDATE it has more data to transmit, upon
validating Host A HIP UPDATE, sends next header to proper module and
continues with Address Verification. This datagram is processed even
though the address is UNVERIFIED.
7. IANA Considerations
This document does not have any IANA requirements.
8. Security Considerations
The approach here is to start using the new address while it is being
validated. One consequence is a few packets are lost or sent to a
wrong target. These are acceptable risks while gaining a fast
address update that works in most cases.
Another risk is there is a small window for malicious piggyback
packets received during this pre-validation interval. But since all
such packets should be ESP protected, the ESP process will catch
these.
Beyond these items, HIP fast mobility does not introduce any new
security considerations beyond that in HIP Host Mobility [RFC8046].
If anything its requirement to know and use the RVS for a peer
improve the frequency of a successful mobility notification.
9. Acknowledgments
The term "shotgun" for fast mobility comes from the InfraHIP project.
The HIP UPDATE lengths were supplied by Jeff Ahrenholz.
Sue Hares of Huawei and Jeff Ahrenholz of Tempered Networks
contributed to the clarity in this document.
10. References
10.1. Normative References
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[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997,
<https://www.rfc-editor.org/info/rfc2119>.
[RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
May 2017, <https://www.rfc-editor.org/info/rfc8174>.
10.2. Informative References
[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,
<https://www.rfc-editor.org/info/rfc7402>.
[RFC8004] Laganier, J. and L. Eggert, "Host Identity Protocol (HIP)
Rendezvous Extension", RFC 8004, DOI 10.17487/RFC8004,
October 2016, <https://www.rfc-editor.org/info/rfc8004>.
[RFC8046] Henderson, T., Ed., Vogt, C., and J. Arkko, "Host Mobility
with the Host Identity Protocol", RFC 8046,
DOI 10.17487/RFC8046, February 2017,
<https://www.rfc-editor.org/info/rfc8046>.
Authors' Addresses
Robert Moskowitz
HTT Consulting
Oak Park, MI 48237
United States of America
Email: rgm@labs.htt-consult.com
Stuart W. Card
AX Enterprize
4947 Commercial Drive
Yorkville, NY 13495
United States of America
Email: stu.card@axenterprize.com
Adam Wiethuechter
AX Enterprize
4947 Commercial Drive
Yorkville, NY 13495
United States of America
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Email: adam.wiethuechter@axenterprize.com
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