Internet Draft L. Berger
Expiration: June 29, 1997 FORE Systems
File: draft-berger-rsvp-ext-06.txt T. O'Malley
BBN
RSVP Extensions for IPSEC Data Flows
January 29, 1997
Status of this Memo
This document is an Internet-Draft. 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.''
To learn the current status of any Internet-Draft, please check the
``1id-abstracts.txt'' listing contained in the Internet- Drafts
Shadow Directories on ftp.is.co.za (Africa), nic.nordu.net (Europe),
munnari.oz.au (Pacific Rim), ds.internic.net (US East Coast), or
ftp.isi.edu (US West Coast).
Abstract
This document presents extensions to Version 1 of RSVP. These
extensions permit support of individual data flows using RFC 1826 IP
Authentication Header (AH) or RFC 1827 IP Encapsulating Security
Payload (ESP). RSVP Version 1 as currently specified can support the
IPSEC protocols, but only on a per address, per protocol basis not on
a per flow basis. The presented extensions can be used with both
IPv4 and IPv6.
Berger, O'Malley Expires June 29, 1997 [Page 1]
Internet Draft RSVP Extensions for IPSEC Flows January 29, 1997
Table of Contents
1 Introduction 3
2 Overview of Extensions 3
3 Object Definition 5
3.1 SESSION Class 5
3.2 FILTER_SPEC Class 6
3.3 SENDER_TEMPLATE Class 6
4 Processing Rules 7
4.1 Required Changes 7
4.2 Merging Flowspecs 8
4.2.1 FF and SE Styles 8
4.2.2 WF Styles 8
5 Security Considerations 9
6 References 10
7 Acknowledgments and Authors' Information 10
7.1 Acknowledgments 10
7.2 Authors' Information 10
Berger, O'Malley Expires June 29, 1997 [Page 2]
Internet Draft RSVP Extensions for IPSEC Flows January 29, 1997
1 Introduction
Recently published Standards Track RFCs specify protocol mechanisms
to provide IP level security. These IP Security, or IPSEC, protocols
support packet level authentication, [RFC1826], and integrity and
confidentiality [RFC1827]. A number of interoperable implementations
already exist and several vendors have announced commercial products
that will use these mechanisms.
The IPSEC protocols provide service by adding a new header between a
packet's IP header and the transport (e.g. UDP) protocol header. The
two security headers are the Authentication Header (AH), for
authentication, and the Encapsulating Security Payload (ESP), for
integrity and confidentiality.
RSVP is being developed as a resource reservation (dynamic QoS setup)
protocol. RSVP as currently specified [RSVPspec96] is tailored
towards IP packets carrying protocols that have TCP or UDP-like
ports. Protocols that do not have such UDP/TCP-like ports, such as
the IPSEC protocols, can be supported, but only with limitations.
Specifically, for flows of IPSEC data packets, flow definition can
only be done on per IP address, per protocol basis.
This memo proposes extensions to RSVP so that data flows containing
IPSEC protocols can be controlled at a granularity similar to what is
already specified for UDP and TCP. The proposed extensions can be
used with both IPv4 and IPv6. Section 2 of this memo will provide an
overview of extensions. Section 3 contains a description of extended
protocol mechanisms. Section 4 presents extended protocol processing
rules. Section 5 defines the additional RSVP data objects.
2 Overview of Extensions
The basic notion is to extend RSVP to use the IPSEC Security
Parameter Index, or SPI, in place of the UDP/TCP-like ports. This
will require a new FILTER_SPEC object, which will contain the IPSEC
SPI, and a new SESSION object.
While SPIs are allocated based on destination address, they will
typically be associated with a particular sender. As a result, two
senders to the same unicast destination will usually have different
SPIs. In order to support the control of multiple independent flows
between source and destination IP addresses, the SPI will be included
as part of the FILTER_SPEC. When using WF, however, all flows to the
Berger, O'Malley Expires June 29, 1997 [Page 3]
Internet Draft RSVP Extensions for IPSEC Flows January 29, 1997
same IP destination address using the same protocol will share the
same reservation. (This limitation exists because the IPSEC
transport headers do not contain a destination demultiplexing value
like the UDP/TCP destination port.)
Although the RESV message format will not change, RESV processing
will require modification. Processing of the new IPSEC FILTER_SPEC
will depend on the use of the new SESSION object and on the next
protocol field contained in the session definition. When the new
FILTER_SPEC object is used, the complete four bytes of the SPI will
need to be extracted from the FILTER_SPEC for use by the packet
classifier. The location of the SPI in the transport header of the
IPSEC packets is dependent on the next protocol field.
The extension will also require a change to PATH processing,
specifically in the usage of the port field in a session definition.
An RSVP session is defined by the triple: (DestAddress, ProtocolId,
DstPort). [RSVPspec96] includes the definition of one type of
SESSION object, it contains UDP/TCP destination ports, specifically
"a 16-bit quantity carried at the octet offset +2 in the transport
header" or zero for protocols that lack such a field. The IPSEC
protocols do not contain such a field, but there remains a
requirement for demultiplexing sessions beyond the IP destination
address. In order to satisfy this requirement, a virtual destination
port, or vDstPort, is introduced. The vDstPort value will be carried
in the new SESSION object but not in the IPSEC transport header.
This change will allow control of multiple IPSEC flows to a single
destination.
In PATH messages, the SENDER_TEMPLATE for IPSEC flows will have the
same format as the modified FILTER_SPEC. But, a new SESSION object
will be used to unambiguously distinguish the use of a virtual
destination port.
Traffic will be mapped (classified) to reservations based on SPIs in
FILTER_SPECs. This, of course, means that when WF is used all flows
to the same IP destination address and protocol ID will share the
same reservation.
The advantages to the described approach are that no changes to
RFC1826 and 1827 are required and that there is no additional per
data packet overhead. The approach does not take advantage of the
IPv6 Flow Label field, so greater efficiency may be possible for IPv6
flows. The details of IPv6 Flow Label usage is left for the future.
Berger, O'Malley Expires June 29, 1997 [Page 4]
Internet Draft RSVP Extensions for IPSEC Flows January 29, 1997
3 Object Definition
The FILTER_SPEC and SENDER_TEMPLATE used with IPSEC protocols will
contain a four byte field that will be used to carry the SPI. Rather
than label the modified field with an IPSEC specific label, SPI, the
label "Generalized Port Identifier", or GPI, will be so that these
object may be reused for non-IPSEC uses in the future. The name for
these objects are the IPv4/GPI FILTER_SPEC, IPv6/GPI FILTER_SPEC,
IPv4/GPI SENDER_TEMPLATE, and IPv6/GPI SENDER_TEMPLATE. Similarly,
the new SESSION objects will be the IPv4/GPI SESSION and the IPv6/GPI
SESSION. When referring to the new objects, IP version will not be
included unless a specific distinction between IPv4 and IPv6 is being
made.
3.1 SESSION Class
SESSION Class = 1.
o IPv4/GPI SESSION object: Class = 1, C-Type = 3
+-------------+-------------+-------------+-------------+
| IPv4 DestAddress (4 bytes) |
+-------------+-------------+-------------+-------------+
| Protocol Id | Flags | vDstPort |
+-------------+-------------+-------------+-------------+
o IPv6/GPI SESSION object: Class = 1, C-Type = 4
+-------------+-------------+-------------+-------------+
| |
+ +
| |
+ IPv6 DestAddress (16 bytes) +
| |
+ +
| |
+-------------+-------------+-------------+-------------+
| Protocol Id | Flags | vDstPort |
+-------------+-------------+-------------+-------------+
Berger, O'Malley Expires June 29, 1997 [Page 5]
Internet Draft RSVP Extensions for IPSEC Flows January 29, 1997
3.2 FILTER_SPEC Class
FILTER_SPEC class = 10.
o IPv4/GPI FILTER_SPEC object: Class = 10, C-Type = 4
+-------------+-------------+-------------+-------------+
| IPv4 SrcAddress (4 bytes) |
+-------------+-------------+-------------+-------------+
| Generalized Port Identifier (GPI) |
+-------------+-------------+-------------+-------------+
o IPv6/GPI FILTER_SPEC object: Class = 10, C-Type = 5
+-------------+-------------+-------------+-------------+
| |
+ +
| |
+ IPv6 SrcAddress (16 bytes) +
| |
+ +
| |
+-------------+-------------+-------------+-------------+
| Generalized Port Identifier (GPI) |
+-------------+-------------+-------------+-------------+
3.3 SENDER_TEMPLATE Class
SENDER_TEMPLATE class = 11.
o IPv4/GPI SENDER_TEMPLATE object: Class = 11, C-Type = 4
Definition same as IPv4/GPI FILTER_SPEC object.
o IPv6/GPI SENDER_TEMPLATE object: Class = 11, C-Type = 5
Definition same as IPv6/GPI FILTER_SPEC object.
Berger, O'Malley Expires June 29, 1997 [Page 6]
Internet Draft RSVP Extensions for IPSEC Flows January 29, 1997
4 Processing Rules
This section presents additions to the Processing Rules presented in
[RSVPproc96]. These additions are required in order to properly
process the GPI SESSION and FILTER_SPEC objects. Values for
referenced error codes can be found in [RSVPspec96]. As in with the
other RSVP documents, values for internally reported (API) errors are
not defined.
4.1 Required Changes
Both RESV and PATH processing will need to be changed to support the
new objects. The changes ensure consistency and extend port
processing.
The following PATH message processing changes are required:
o When a session is defined using the GPI SESSION object, only
the GPI SENDER_TEMPLATE may be used. When this condition is
violated, end-stations should report a "Conflicting C-Type" API
error to the application.
o For PATH messages that contain the GPI SESSION object,
end-stations must verify that the ProtocolId corresponds to a
protocol known to use the GPI SESSION object. Values 51 (AH)
or 50 (ESP) must be supported by implementations supporting
the described IPSEC extensions. If an unknown ProtocolId is used,
then the API should report an "API Error" to the application.
o For such messages, the vDstPort value should be recorded.
The vDstPort value forms part of the recorded state and is used
to match Resv messages, but it is not passed to traffic control.
Non-zero values of vDstPort are required. This requirement
ensures that a non-GPI SESSION object will never merge with a
GPI SESSION object. Violation of this condition causes an
"Invalid Destination Port" API error.
The changes to RESV message processing are:
o When a RESV message contains a GPI FILTER_SPEC, the session
must be defined using the GPI SESSION object. Otherwise, this is a
message formatting error.
o The GPI contained in the FILTER_SPEC must match the GPI
contained in the SENDER_TEMPLATE. Otherwise, a "No sender
Berger, O'Malley Expires June 29, 1997 [Page 7]
Internet Draft RSVP Extensions for IPSEC Flows January 29, 1997
information for this Resv message" error is generated.
o When the GPI FILTER_SPEC is used, each node must create
a data classifier for the flow described by the quadruple:
(DestAddress, ProtocolId, SrcAddress, GPI). The data classifier
will need to look for the four byte GPI at transport header
offset +4 for AH, and at transport header offset +0 for ESP.
4.2 Merging Flowspecs
When using this extension for IPSEC data flows, RSVP sessions are
defined by the triple: (DestAddress, ProtocolId, vDstPort).
Similarly, a sender is defined by the tuple: (SrcAddress, GPI), where
the GPI field will be a four byte representation of a generalized
source port. These extensions have some ramifications depending upon
the reservation style.
4.2.1 FF and SE Styles
In the FF and SE Styles, the FILTER_SPEC object contains the
(SrcAddress, GPI) pair. This allows the receiver to uniquely
identify senders based on both elements of the pair. When merging
explicit sender descriptors, the senders may only be considered
identical when both elements are identical.
4.2.2 WF Styles
These extensions provide very limited service when used with WF style
reservations. As described, the SENDER_TEMPLATE and FILTER_SPEC each
contain the GPI. In a WF style reservation, the RESV message does
NOT contain a FILTER_SPEC (after all, it is a wildcard filter), and
the SENDER_TEMPLATE is ignored (again, because any sender is
allowed). As a result, classifiers may match all packets which
contain both the session's destination IP address and next protocol
ID to such WF reservations.
Although a solution for this limitation is not proposed, this issue
is not seen as significant since IPSEC applications are less likely
to use WF style reservations.
Berger, O'Malley Expires June 29, 1997 [Page 8]
Internet Draft RSVP Extensions for IPSEC Flows January 29, 1997
5 Security Considerations
The same considerations stated in [RSVPspec96], [RFC1826], and
[RFC1827] apply to the extensions described in this note. There is
one additional issue related to these extensions.
Changes in SPI values for a given flow will affect RSVP flows and
reservations. Changes will happen whenever that flow changes its
Security Association. Such changes will occur when a flow is rekeyed
(i.e. to use a new key). Rekeying intervals are typically set based
on traffic levels, key size, threat environment, and crypto algorithm
in use. When an SPI change occurs it will, in most cases, be
necessary to update (send) the corresponding SENDER_TEMPLATEs and
FILTER_SPECs. IPSEC implementations, RSVP applications, and RSVP
end-station implementations will need to take the possibility of
changes of SPI into account to ensure proper reservation behavior.
This issue is likely to be a tolerable, since rekeying intervals are
under the control of local administrators.
Many, if not most, RSVP sessions will not need to deal with this
rekeying issue. For those applications that do need to deal with
changes of SPIs during a session, the impact of sending new PATH and
RESV messages will vary based on the reservation style being used.
Builders of such applications may want to select reservation style
based on interaction with SPI changes.
The least impact of an SPI change will be to WF style reservations.
For such reservations, a new SENDER_TEMPLATE will need to be sent,
but no new RESV is required. For SE style reservations, both a new
SENDER_TEMPLATE and a new RESV will need to be sent. This will
result in changes to state, but should not affect data packet
delivery or actual resource allocation in any way. The FF style will
be impacted the most. Like with SE, both PATH and RESV messages will
need to be sent. But, since FF style reservations result in sender
receiving its own resource allocation, resources will be allocated
twice for a period of time. Or, even worse, there won't be enough
resources to support the new flow without first freeing the old flow.
A way around this FF/SPI-change problem does exist. Applications
that want FF style reservations can use multiple SE reservations.
Each real sender would have a separate SESSION (vDstPort) definition.
When it came time to switch SPIs, a shared reservation could be made
for the new SPI while the old SPI was still active. Once the new SPI
was in use, the old reservation could be torn down. This is less
than optimal, but will provide uninterrupted service for a set of
Berger, O'Malley Expires June 29, 1997 [Page 9]
Internet Draft RSVP Extensions for IPSEC Flows January 29, 1997
applications.
6 References
[RSVPspec96] Braden, R., Ed., Zhang, L., Estrin, D., Herzog, S., and
S. Jamin, "Resource ReSerVation Protocol (RSVP) --
Version 1 Functional Specification. Internet Draft
draft-ietf-rsvp-spec-014.ps, November 1996.
[RSVPproc96] Braden, R., Ed., Zhang, "Resource ReSerVation
Protocol (RSVP) -- Version 1 Message Processing Rules",
Internet Draft draft-ietf-rsvp-procrules-00.txt,
November 1996.
[RFC1825] Atkinson, R., "Security Architecture for the Internet
Protocol", RFC 1825, NRL, August 1995.
[RFC1826] Atkinson, R., "IP Authentication Header", RFC 1826, NRL,
August 1995.
[RFC1827] Atkinson, R., "IP Encapsulating Security Payload", RFC
1827, NRL, August 1995.
7 Acknowledgments and Authors' Information
7.1 Acknowledgments
This note includes ideas originated and reviewed by a number of
individuals who did not participate in this note's writing. The
authors would like to acknowledge their contribution. We thank Ran
Atkinson <rja@cisco.com>, Fred Baker <fred@cisco.com>, Greg Troxel
<gdt@bbn.com>, John Krawczyk <jkrawczyk@BayNetworks.com> for much
appreciated input and feedback. Special appreciation goes to Bob
Braden <braden@isi.edu> for his detailed editorial and technical
comments. We also thank Buz Owen, Claudio Topolcic, Andy Veitch, and
Luis Sanchez for their help in coming up with the proposed approach.
If any brain-damage exists in this note, it originated solely from
the authors.
7.2 Authors' Information
Lou Berger Tim O'Malley
FORE Systems BBN Corporation
Berger, O'Malley Expires June 29, 1997 [Page 10]
Internet Draft RSVP Extensions for IPSEC Flows January 29, 1997
6905 Rockledge Drive 10 Moulton Street
Suite 800 Cambridge, MA 02138
Bethesda, MD 20817
Phone: 301-571-2534 Phone: 617-873-3076
EMail: lberger@fore.com EMail: timo@bbn.com
Berger, O'Malley Expires June 29, 1997 [Page 11]