Network Working Group A. Barbir
Internet-Draft Nortel Networks
Expires: December 10, 2003 June 11, 2003
OPES processor and end points communications
draft-ietf-opes-end-comm-00
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Copyright (C) The Internet Society (2003). All Rights Reserved.
Abstract
This memo documents tracing requirements for Open Pluggable Edge
Services (OPES).
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
2. OPES Tracing . . . . . . . . . . . . . . . . . . . . . . . . 4
2.1 What is traceable in an OPES Flow? . . . . . . . . . . . . . 4
2.2 Requirements for Information Related to Traceable
Entities? . . . . . . . . . . . . . . . . . . . . . . . . . 5
3. Requirements for OPES systems . . . . . . . . . . . . . . . 6
4. Requirements for OPES processors . . . . . . . . . . . . . . 7
5. Requirements for callout servers . . . . . . . . . . . . . . 8
6. Privacy considerations . . . . . . . . . . . . . . . . . . . 9
6.1 Tracing and Trust Domains . . . . . . . . . . . . . . . . . 9
7. How to Support Tracing . . . . . . . . . . . . . . . . . . . 10
7.1 Tracing and OPES System Granularity . . . . . . . . . . . . 10
7.2 Requirements for In-Band Tracing . . . . . . . . . . . . . . 11
7.2.1 Tracing Information Granularity and Persistence levels
Requirements . . . . . . . . . . . . . . . . . . . . . . . . 11
7.3 Protocol Binding . . . . . . . . . . . . . . . . . . . . . . 12
7.4 Tracing scenarios and examples . . . . . . . . . . . . . . . 12
8. IAB considerations . . . . . . . . . . . . . . . . . . . . . 13
8.1 Notification Concerns . . . . . . . . . . . . . . . . . . . 13
8.1.1 Addressing IAB Consideration 3.1 . . . . . . . . . . . . . . 14
8.1.2 Addressing IAB Consideration 3.2 . . . . . . . . . . . . . . 15
9. Security considerations . . . . . . . . . . . . . . . . . . 17
10. IANA Considerations . . . . . . . . . . . . . . . . . . . . 18
Normative References . . . . . . . . . . . . . . . . . . . . 19
Informative References . . . . . . . . . . . . . . . . . . . 20
Author's Address . . . . . . . . . . . . . . . . . . . . . . 20
A. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 21
Intellectual Property and Copyright Statements . . . . . . . 22
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1. Introduction
The Open Pluggable Edge Services (OPES) architecture [8] enables
cooperative application services (OPES services) between a data
provider, a data consumer, and zero or more OPES processors. The
application services under consideration analyze and possibly
transform application-level messages exchanged between the data
provider and the data consumer.
The execution of such services is governed by a set of rules
installed on the OPES processor. The rules enforcement can trigger
the execution of service applications local to the OPES processor.
Alternatively, the OPES processor can distribute the responsibility
of service execution by communicating and collaborating with one or
more remote callout servers. As described in [8], an OPES processor
communicates with and invokes services on a callout server by using a
callout protocol.
The work specify the requirements for providing tracing functionality
for the OPES architecture [8]. This document specifies tracing
mechanisms that the OPES architecture could provide that enable data
provider application to detect inappropriate clinet centric actions
by OPES entities. The work focus on developing tracing requirements
that can be used to fulfil the notification and Non-Blocking
requirements [2].
In the OPES architecture document [8], there is a requirement of
relaying tracing information in-band. This work investigates this
possibility and discusses possible methods that could be used to
detect faulty OPES processors or callout servers by end points in an
OPES flow.
The document is organized as follows: .......
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2. OPES Tracing
Before discussing what is traceable in an OPES flow, it is beneficial
to define what tracing means. Tracing is defined as the inclusion of
necessary information within a message in an OPES flow that could be
used to identify the set of transformations or adpatations that have
been performed on its content before its delivery to an end point
(the data consumer application).
o OPES trace: application message information about OPES entities
that adapted that message
o OPES tracing: the process of including, manipulating, and
interpreting an OPES trace
To emphasize, the above definition means that OPES tracing SHOULD be
performed on per message basis. Trace format is dependent on the
application protocol being adapted by OPES. Data consumer application
can use OPES trace to infer the actions that have been performed by
OPES system(s). The architecture document requires [8] that tracing
be supported in-band.
2.1 What is traceable in an OPES Flow?
o The data consumer application end point MUST be able to identify
the OPES processors that have acted on an application message.
o The data consumer application end point SHOULD be able to identify
OPES services (including callout services) that were performed on
request/responses that are part of an application message.
o TBD
o TBD
For a given trace, an OPES entity involved in handling the
corresponding application message is "traceable" or "traced" if
information about it appears in that trace. OPES entities have
different levels of traceability requirements. Specifically,
o An OPES system MUST be traceable
o An OPES processor SHOULD be traceable
o An OPES service MAY be traceable
o Editor Note: Need to define an OPES System properly
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2.2 Requirements for Information Related to Traceable Entities?
The requirements for information as related to entities that are
terceable in an OPES flow are:
o The privacy policy at the time it dealt with the message
o Identification of the party responsible for setting and enforcing
that policy
o Information pointing to a technical contact
o Information that identifies, to the technical contact, the OPES
processors involved in processing the messag
o TBD
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3. Requirements for OPES systems
Editor Note: Need to define OPES System and state requirements
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4. Requirements for OPES processors
TBD
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5. Requirements for callout servers
If it is the task of an OPES processor to add trace records to
application messages, then callout servers that uses the OCP protocol
are not affected by tracing requirements.In order for an OCP protocol
to be tracing neutral, the OPES server SHOULD be able to meet the
following requirements:
o Callout services adapt payload regardless of the application
protocol in use and leave header adjustment to OPES processor.
o OPES processor SHOULD be able to trace its own invocation and
service(s) execution because OPES processor understand the
application protocol.
o Callout servers MAY be able to add their own OPES trace records
to application level messages.
o TBD
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6. Privacy considerations
6.1 Tracing and Trust Domains
A trust domain may include several OPES systems and entities. Within
a trust domain, there MUST be at least support for one trace entry
per system. Entities outside of that system may or may not see any
traces, depending on domain policies or configuration. For example,
if an OPES system is on the content provider "side", end-users are
not guaranteed any traces. If an OPES system is working inside
end-user domain, the origin server is not guaranteed any traces
related to user requests.
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7. How to Support Tracing
In order to support tracing, the following aspects must be addressed:
o There MUST be a System Identifier that identify a domain that is
employing an OPES system.
o An OPES processor MUST be able to be uniquely identified (MUST
have an Identifier) within a system.
o An OPES processor MUST add its identification to the trace.
o An OPES processor SHOULD add to the trace identification of every
callout service that received the application message.
o An OPES processor MUST add to the trace identification of the
"system/entity" it belongs to. "System" ID MUST make it possible
to access "system" privacy policy.
o An OPES processor MAY group the above information for sequential
trace entries having the same "system/entity" ID. In other words,
trace entries produced within the same "system/entity" MAY be
merged/aggregated into a single less detailed trace entry.
o An OPES processor MAY delegate trace management to a callout
service within the same "system/entity".
TBD
7.1 Tracing and OPES System Granularity
There are two distinct uses of traces. First, is to SHOULD enable the
"end (content producer or consumer) to detect OPES processor presence
within end's trust domain. Such "end" should be able to see a trace
entry, but does not need to be able to interpret it beyond
identification of the trust domain(s).
Second, the domain administrator SHOULD be able to take a trace entry
(possibly supplied by an "end? as an opaque string) and interpret it.
The administrator must be able to identify OPES processor(s) involved
and may be able to identify applied adaptation services along with
other message-specific information. That information SHOULD help to
explain what OPES agent(s) were involved and what they did. It may be
impractical to provide all the required information in all cases.
This document view a trace record as a hint, as opposed to an
exhaustive audit.
Since the administrators of various trust domains can have various
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ways of looking into tracing, they MAY require the choice of freedom
in what to put in trace records and how to format them. Trace records
should be easy to extend beyond basic OPES requirements. Trace
management algorithms should treat trace records as opaque data to
the extent possible.
It is not expected that entities in one trust domain to be able to
get all OPES-related feedback from entities in other trust domains.
For example, if an end-user suspects that a served is corrupted by a
callout service, there is no guarantee that the use will be able to
identify that service, contact its owner, or debug it _unless_ the
service is within my trust domain. This is no different from the
current situation where it is impossible, in general, to know the
contact person for an application on an origin server that generates
corrupted HTML; and even if the person is known, one should not
expect that person to respond to end-user queries.
7.2 Requirements for In-Band Tracing
The OPES architecture [8] states that traces must be in-band. The
support of this design specification is dependent on the specifics of
the message application level protocol that is being used in an OPES
flow. In-band tracing limits the type of application protocols that
OPES can support. The details of what a trace record can convey is
also dependent on the choice of the application level protocol.
For these reasons, the work will document requirements for
application protocols that need to support OPES traces. However, the
architecture does not prevent implementers of developing out-of-band
protocols and techniques to address the above limitation.
7.2.1 Tracing Information Granularity and Persistence levels
Requirements
In order to be able to trace entities that have acted on an
application message in an OPES flow, there may be requirements to
keep information that is related to the following:
o Message-related informatio: All data that describes specific
actions performed on the message SHOULD be provided with that
message, as there is no other way to find message level details
later.
o Session related information: Session level data MUST be preserved
for the duration of the session. OPES processor is responsible for
inserting notifications if session-level information changes.
o End-point related data: What profile is activated? Where to get
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profile details? Where to set preferences?
o TBD
7.3 Protocol Binding
How tracing is added is application protocol-specific and will be
documented in separate drafts. This work documents what tracing
information is required and some common tracing elements.
7.4 Tracing scenarios and examples
TBD
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8. IAB considerations
This section examines IAB [2] considerations (3.1) and (3.2)
regarding notification in an OPES architecture. The IAB
considerations are reiterated here for ease of reference.
Notification propagates in opposite direction of tracing and cannot
be attached to application messages that it notifies about.
Notification can be done out-band and may require the development of
a new protocol. The direction of data flow for tracing and
notification are deoicted in Figure 1.
Notification
+-----------------------------------------------
| |
| V
+---------------+ +-------+ +---------------+
| | | | | Data Provider |
| Data Consumer | Tracing | OPES |<----->| Application |
| Application |<-----------| | +---------------+
+---------------+ +-------+
^
|OCP
|
V
+---------+
| Callout |
| Server |
+---------+
Figure 1: Notification Flow
8.1 Notification Concerns
Notifications for every HTTP request can burden some content
providers. Therefore, it might be preferable to consider mechanisms
that allow for the explicit request of notification. Hence, a
mechanism for explicit request of notification May be required.
Furthermore, end point privacy is a concern. An end user may consider
information about OPES services applied on their behalf as private.
For example, if translation for braille device has been applied, it
can be concluded that the user is having eyesight problems; such
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information may be misused if the user is applying for a job online.
Similarly, a content provider may consider information about its OPES
services private. For example, use of a specific OPES intermediary by
a high traffic volume site may indicate business alliances that have
not been publicly announced yet. Another example of privacy, include
situations where a user may not want to reveal to any content
provider all the OPES services that have been applied on their
behalf. For example, why should every content provider know what
exact virus scanner a user is using?
Security is also a concern. An attacker may benefit from knowledge
of internal OPES services layout, execution order, software versions
and other information that are likely to be present in automated
notifications.
The level of available details in notifications versus content
provider interest in supporting notification is a concern.
Experience shows that content providers often require very detailed
information about user actions to be interested in notifications at
all. For example, Hit Metering protocol [11] has been designed to
supply content providers with proxy cache hit counts, in an effort to
reduce cache busting behavior which was caused by content providers
desire to get accurate site "access counts". However, the Hit
Metering protocol is currently not widely deployed. This is because
the protocol does not supply content providers with information such
as client IP addresses, browser versions, or cookies.
The Hit Metering experience is relevant because Hit Metering
protocol was designed to do for HTTP caching intermediaries what
OPES notifications are meant to do for OPES intermediaries. Thus, it
is important to have the right balance when specifying the
notofication requirements for OPES.
In this document, IAB choice of "Notification" label is interpreted
as "Notification assistance" (i.e. making notifications meaningful)
and is not be interpreted as a "Notification protocol". Therefore,
the work treats IAB considerations (3.1 and 3.2) as informative (not
normative).
8.1.1 Addressing IAB Consideration 3.1
The consideration is restated below for ease of reference.
(3.1) Notification: The overall OPES framework needs to assist
content providers in detecting and responding to client-centric
actions by OPES intermediaries that are deemed inappropriate by the
content provider.
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IAB consideration (3.1) suggests that the overall OPES framework
needs to assist content providers in detecting and responding to
client-centric actions by OPES intermediaries that are deemed
inappropriate by the content provider.
It is important to note that most client-centric actions happen after
the application message has left the content provider(s). Thus,
notifications cannot be piggy-backed to application messages and have
to travel in the opposite direction of traces, see Figure 1. To
address this requirement directly, one would have to develop an out
of band protocol to support notification.
At this stage, there is no need to develop an out of band protocol to
support notification, since requiring the OPES architecture to having
a tracing facility can fulfil the objectives of notification. In
this regard, it is recommended that tracing MUST be always-on, just
like HTTP Via headers. This should eliminate notification as a
separate requirement.
8.1.2 Addressing IAB Consideration 3.2
The consideration is restated below for ease of reference.
(3.2) Notification: The overall OPES framework should assist end
users in detecting the behavior of OPES intermediaries, potentially
allowing them to identify imperfect or compromised intermediaries.
TBD
If the OPES end points cooperate then notification can be supported
by tracing. Content providers that suspect or experience difficulties
can do any of the following:
o Check whether requests they receive pass through OPES
intermediaries. Presence of OPES tracing info will determine that.
This check is only possible for request/response protocols. For
other protocols (e.g., broadcast or push), the provider would have
to assume that OPES intermediaries are involved until proven
otherwise.
o If OPES intermediaries are suspected, request OPES traces from
potentially affected user(s). The trace will be a part of the
application message received by the user software. If users
cooperate, the provider(s) have all the information they need. If
users do not cooperate, the provider(s) cannot do much about it
(they might be able to deny service to uncooperative users in
some cases).
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o Some traces may indicate that more information is available by
accessing certain resources on the specified OPES intermediary or
elsewhere. Content providers may query for more information in
that case.
o If everything else fails, providers can enforce no-adaptation
policy using appropriate OPES bypass mechanisms and/or end-to-end
mechanisms.
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9. Security considerations
TBD
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10. IANA Considerations
The proposed work will evaluate current protocols for OCP. If the
work determines that a new protocol need to be developed, then there
may be a need to request new numbers from IANA.
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Normative References
[1] McHenry, S., et. al, "OPES Scenarios and Use Cases",
Internet-Draft TBD, May 2002.
[2] Floyd, S. and L. Daigle, "IAB Architectural and Policy
Considerations for Open Pluggable Edge Services", RFC 3238,
January 2002.
[3] Fielding, R., Gettys, J., Mogul, J., Nielsen, H., Masinter, L.,
Leach, P. and T. Berners-Lee, "Hypertext Transfer Protocol --
HTTP/1.1", RFC 2616, June 1999.
[4] OPES working group, "OPES Service Authorization and Enforcement
Requirements", Internet-Draft TBD, May 2002.
[5] OPES working group, "OPES Ruleset Schema", Internet-Draft TBD,
May 2002.
[6] A. Beck et al., "Requirements for OPES Callout Protocols",
Internet-Draft http://www.ietf.org/internet-drafts/
draft-ietf-opes-protocol-reqs-03.txt, December 2002.
[7] A. Barbir et al., "Security Threats and Risks for Open Pluggable
Edge Services", Internet-Draft http://www.ietf.org/
internet-drafts/draft-ietf-opes-threats-00.txt, October 2002.
[8] A. Barbir et al., "An Architecture for Open Pluggable Edge
Services (OPES)", Internet-Draft http://www.ietf.org/
internet-drafts/draft-ietf-opes-architecture-04, December 2002.
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Informative References
[9] Westerinen, A., Schnizlein, J., Strassner, J., Scherling, M.,
Quinn, B., Herzog, S., Huynh, A., Carlson, M., Perry, J. and S.
Waldbusser, "Terminology for Policy-Based Management", RFC
3198, November 2001.
[10] L. Cranor, et. al, "The Platform for Privacy Preferences 1.0
(P3P1.0) Specification", W3C Recommendation 16 http://
www.w3.org/TR/2002/REC-P3P-20020416/ , April 2002.
[11] "Hit Metering", RFC .
Author's Address
Abbie Barbir
Nortel Networks
3500 Carling Avenue
Nepean, Ontario K2H 8E9
Canada
Phone: +1 613 763 5229
EMail: abbieb@nortelnetworks.com
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Appendix A. Acknowledgements
TBD
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