HIP Working Group A. Keranen
Internet-Draft Ericsson
Intended status: Experimental March 8, 2010
Expires: September 9, 2010
Host Identity Protocol Signaling Message Transport Modes
draft-keranen-hip-over-hip-01
Abstract
This document specifies two transport modes for Host Identity
Protocol signaling messages that allow conveying them over encrypted
connections initiated with the Host Identity Protocol.
Status of this Memo
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . . 3
3. Protocol Extensions . . . . . . . . . . . . . . . . . . . . . . 3
3.1. Mode Negotiation in HIP Base Exchange . . . . . . . . . . . 3
3.2. Mode Negotiation After HIP Base Exchange . . . . . . . . . 4
3.3. HIP Messages on Encrypted Connections . . . . . . . . . . . 5
3.3.1. ESP mode . . . . . . . . . . . . . . . . . . . . . . . 5
3.3.2. ESP-TCP mode . . . . . . . . . . . . . . . . . . . . . 5
3.4. Recovering from Failed Encrypted Connections . . . . . . . 6
3.5. Simultaneous Host Mobility . . . . . . . . . . . . . . . . 6
4. Notify Packet Types . . . . . . . . . . . . . . . . . . . . . . 6
5. Security Considerations . . . . . . . . . . . . . . . . . . . . 7
6. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 7
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 7
8. References . . . . . . . . . . . . . . . . . . . . . . . . . . 7
8.1. Normative References . . . . . . . . . . . . . . . . . . . 7
8.2. Informational References . . . . . . . . . . . . . . . . . 8
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . . 8
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1. Introduction
Host Identity Protocol (HIP) [RFC5201] signaling messages can be
exchanged over plain IP using the protocol number reserved for this
purpose, or over UDP using the UDP port reserved for HIP NAT
traversal [I-D.ietf-hip-nat-traversal]. When two hosts perform a HIP
base exchange, they set up an encrypted connection between them for
data traffic, but continue to use plain IP or UDP for HIP signaling
messages.
This document defines how the encrypted connection can be used also
for HIP signaling messages. Two different modes are defined: HIP
over Encapsulating Security Payload (ESP) and HIP over TCP. The
benefit of sending HIP messages over ESP is that all signaling
traffic (including HIP headers) will be encrypted. If HIP messages
are sent over TCP (which in turn is transported over ESP), TCP can
handle also message fragmentation where needed.
2. Terminology
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in RFC 2119 [RFC2119].
3. Protocol Extensions
This section defines how support for different HIP signaling message
transport modes is negotiated and the normative behavior required by
the extension.
3.1. Mode Negotiation in HIP Base Exchange
A HIP host implementing this specification SHOULD indicate the modes
it supports, and is willing to use, in the base exchange. The HIP
signaling message transport mode negotiation is similar to HIP NAT
traversal mode negotiation: first the Responder lists the supported
modes in a HIP_TRANSPORT_MODE parameter (see Figure 1) in the R1
packet. If the Initiator supports, and is willing to use, any of the
modes proposed by the Responder, it selects one of the modes by
adding a HIP_TRANSPORT_MODE parameter containing the selected mode to
the I2 packet. Finally, if the Initiator selected one of the modes
and the base exchange succeeds, hosts use the selected mode for the
following HIP signaling messages sent between them.
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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 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Mode ID #1 | Mode ID #2 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Mode ID #n | Padding |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Type [ TBD by IANA; 990 ]
Length length in octets, excluding Type, Length, and padding
Mode ID defines the proposed or selected transport mode(s)
The following mode IDs are defined:
ID name Value
RESERVED 0
DEFAULT 1
ESP 2
ESP-TCP 3
Figure 1: Format of the HIP_TRANSPORT_MODE parameter
The mode DEFAULT indicates that the same transport mode (e.g., plain
IP or UDP) that was used for the base exchange should be used for
subsequent HIP signaling messages. In the ESP mode the messages are
sent as such on the encrypted ESP connection and in the ESP-TCP mode
TCP is used within the ESP tunnel.
3.2. Mode Negotiation After HIP Base Exchange
If a HIP hosts wants to change to a different transport mode (or
start using a transport mode) some time after the base exchange, it
sends a HIP UPDATE packet with a HIP_TRANSPORT_MODE parameter
containing the mode(s) it would prefer to use. The host receiving
the UPDATE MUST respond with an UPDATE packet containing the mode
that is selected as in the negotiation during the base exchange. If
the receiving host does not support, or is not willing to use, any of
the listed modes, it MUST respond with a NO_VALID_HIP_TRANSPORT_MODE
NOTIFY packet (see Section 4) and continue using the same transport
mode.
Since the HIP_TRANSPORT_MODE parameter's type is not critical (as
defined in Section 5.2.1 of [RFC5201]), a host not supporting this
extension would simply acknowledge the UPDATE without responding with
an UPDATE containing a HIP_TRANSPORT_MODE parameter.
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3.3. HIP Messages on Encrypted Connections
This specification defines two different transport modes for sending
HIP packets over encrypted ESP connections. These modes require that
the ESP transport format [RFC5202] is negotiated to be used between
the hosts. If the ESP transport format is not used, these modes MUST
NOT be offered in the HIP_TRANSPORT_MODE parameter.
The ESP mode provides simple protection for all the signaling traffic
and can be used as a generic replacement for the DEFAULT mode in
cases where all signaling traffic should be encrypted. If the HIP
messages may become so large that they would need to be fragmented,
e.g., because of HIP certificates [I-D.ietf-hip-cert] or DATA
messages [I-D.ietf-hip-hiccups], it is RECOMMENDED to use the ESP-TCP
mode which can handle message fragmentation at TCP level instead of
relying on IP level fragmentation.
3.3.1. ESP mode
If the ESP mode is selected in the base exchange, both hosts MUST
listen for incoming HIP signaling messages and send outgoing messages
on the encrypted connection. The ESP header's next header value for
such messages MUST be set to HIP (139).
3.3.2. ESP-TCP mode
If the ESP-TCP mode is selected, the host with the larger HIT
(calculated as defined in Section 6.5 of [RFC5201]) MUST start to
listen for an incoming TCP connection on the port 10500 on the
encrypted connection and the other host MUST create a TCP connection
to that port. The host with the lower HIT SHOULD use port 10500 as
the source port for the TCP connection. Once the TCP connection is
established, both hosts MUST listen for incoming HIP signaling
messages and send the outgoing messages using the TCP connection.
The ESP next header value for messages sent using the ESP-TCP mode
connections MUST be set to TCP (6).
If the hosts are unable to create the TCP connection, the host that
initiated the mode negotiation MUST restart the negotiation with
UPDATE message and SHOULD NOT propose the ESP-TCP mode. If local
policy does not allow using any other mode than ESP-TCP, the HIP
association MUST be closed. The UPDATE or CLOSE message MUST be sent
using the same transport mode that was used for negotiating the use
of the ESP-TCP mode.
Since TCP provides reliable transport, the HIP messages sent over TCP
MUST NOT be retransmitted for the purpose of achieving reliable
transmission. Instead, a host simply waits for the same time that
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would be taken by the maximum amount of retransmissions with
unreliable transmission before concluding that there is no response.
3.4. Recovering from Failed Encrypted Connections
If the encrypted connection fails for some reason, it can no longer
be used for HIP signaling and the hosts SHOULD re-establish the
connection using HIP messages that are sent outside of the encrypted
connection. Hence, while listening for incoming HIP messages on the
encrypted connection, hosts MUST still accept incoming HIP messages
using the same transport method (e.g., UDP or plain IP) that was used
for the base exchange. When responding to a HIP message sent outside
of encrypted connection, the response MUST be sent using the same
transport method as the original message used.
The UPDATE messages used for re-establishing the encrypted connection
MUST contain a HIP_TRANSPORT_MODE parameter and the negotiation
proceeds as described in Section 3.2.
3.5. Simultaneous Host Mobility
If two hosts having a HIP association change addresses
simultaneously, they may not be able to send UPDATE messages to the
right address using the encrypted connection. This results in a
similar situation as if the encrypted connection had failed and the
hosts need to re-negotiate the new addresses using un-encrypted
UPDATE messages and possibly rendezvous [RFC5204] or HIP relay
[I-D.ietf-hip-nat-traversal] servers. Also these UPDATE messages
MUST contain the HIP_TRANSPORT_MODE parameter and perform the
transport mode negotiation.
4. Notify Packet Types
The new Notify Packet Types [RFC5201] defined in this document are
shown below. The Notification Data field for the error notifications
SHOULD contain the HIP header of the rejected packet.
NOTIFICATION PARAMETER - ERROR TYPES Value
------------------------------------ -----
NO_VALID_HIP_TRANSPORT_MODE 70
If a host sends UPDATE message that does not have any transport
mode the receiving host is willing to use, it sends back a NOTIFY
error packet with this type.
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5. Security Considerations
By exchanging the HIP messages over ESP connection, all HIP signaling
data (after the base exchange) will be encrypted, but only if NULL
encryption is not used. Thus, host requiring confidentiality for the
HIP signaling messages must check that encryption is negotiated to be
used on the ESP connection.
6. Acknowledgements
Thanks to Gonzalo Camarillo, Kristian Slavov, Tom Henderson, and
Miika Komu for comments on the draft.
7. IANA Considerations
This section is to be interpreted according to [RFC5226].
This document updates the IANA Registry for HIP Parameter Types
[RFC5201] by assigning new HIP Parameter Type value for the
HIP_TRANSPORT_MODE parameter (defined in Section 3.1).
The HIP_TRANSPORT_MODE parameter has 16-bit unsigned integer fields
for different modes, for which IANA is to create and maintain a new
sub-registry entitled "HIP Transport Modes" under the "Host Identity
Protocol (HIP) Parameters" registry. Initial values for the
transport mode registry are given in Section 3.1; future assignments
are to be made through IETF Review [RFC5226]. Assignments consist of
a transport mode identifier name and its associated value.
8. References
8.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC5201] Moskowitz, R., Nikander, P., Jokela, P., and T. Henderson,
"Host Identity Protocol", RFC 5201, April 2008.
[RFC5202] Jokela, P., Moskowitz, R., and P. Nikander, "Using the
Encapsulating Security Payload (ESP) Transport Format with
the Host Identity Protocol (HIP)", RFC 5202, April 2008.
[RFC5226] Narten, T. and H. Alvestrand, "Guidelines for Writing an
IANA Considerations Section in RFCs", BCP 26, RFC 5226,
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May 2008.
8.2. Informational References
[RFC5204] Laganier, J. and L. Eggert, "Host Identity Protocol (HIP)
Rendezvous Extension", RFC 5204, April 2008.
[I-D.ietf-hip-nat-traversal]
Komu, M., Henderson, T., Tschofenig, H., Melen, J., and A.
Keranen, "Basic HIP Extensions for Traversal of Network
Address Translators", draft-ietf-hip-nat-traversal-09
(work in progress), October 2009.
[I-D.ietf-hip-cert]
Heer, T. and S. Varjonen, "HIP Certificates",
draft-ietf-hip-cert-02 (work in progress), October 2009.
[I-D.ietf-hip-hiccups]
Camarillo, G. and J. Melen, "HIP (Host Identity Protocol)
Immediate Carriage and Conveyance of Upper- layer Protocol
Signaling (HICCUPS)", draft-ietf-hip-hiccups-02 (work in
progress), March 2010.
Author's Address
Ari Keranen
Ericsson
Hirsalantie 11
02420 Jorvas
Finland
Email: Ari.Keranen@ericsson.com
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