draft-ietf-opes-protocol-reqs-03.txt   rfc3836.txt 
Open Pluggable Edge Services A. Beck Network Working Group A. Beck
Internet-Draft M. Hofmann Request for Comments: 3836 M. Hofmann
Expires: June 12, 2003 Lucent Technologies Category: Informational Lucent Technologies
H. Orman H. Orman
Purple Streak Development Purple Streak Development
R. Penno R. Penno
Nortel Networks Nortel Networks
A. Terzis A. Terzis
Individual Consultant Johns Hopkins University
December 12, 2002 August 2004
Requirements for OPES Callout Protocols Requirements for Open Pluggable Edge Services (OPES)
draft-ietf-opes-protocol-reqs-03 Callout Protocols
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Copyright Notice Copyright Notice
Copyright (C) The Internet Society (2002). All Rights Reserved. Copyright (C) The Internet Society (2004).
Abstract Abstract
This document specifies the requirements that the OPES (Open This document specifies the requirements that the OPES (Open
Pluggable Edge Services) callout protocol must satisfy in order to Pluggable Edge Services) callout protocol must satisfy in order to
support the remote execution of OPES services. The requirements are support the remote execution of OPES services. The requirements are
intended to help evaluating possible protocol candidates as well as intended to help evaluate possible protocol candidates, as well as to
to guide the development of such protocols. guide the development of such protocols.
Table of Contents Table of Contents
1. Terminology . . . . . . . . . . . . . . . . . . . . . . . . 3 1. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 4 2. Introduction. . . . . . . . . . . . . . . . . . . . . . . . . 2
3. Functional Requirements . . . . . . . . . . . . . . . . . . 5 3. Functional Requirements . . . . . . . . . . . . . . . . . . . 3
3.1 Reliability . . . . . . . . . . . . . . . . . . . . . . . . 5 3.1. Reliability . . . . . . . . . . . . . . . . . . . . . . 3
3.2 Congestion Avoidance . . . . . . . . . . . . . . . . . . . . 5 3.2. Congestion Avoidance . . . . . . . . . . . . . . . . . 3
3.3 Callout Transactions . . . . . . . . . . . . . . . . . . . . 5 3.3. Callout Transactions . . . . . . . . . . . . . . . . . 3
3.4 Callout Connections . . . . . . . . . . . . . . . . . . . . 6 3.4. Callout Connections . . . . . . . . . . . . . . . . . . 4
3.5 Asynchronous Message Exchange . . . . . . . . . . . . . . . 6 3.5. Asynchronous Message Exchange . . . . . . . . . . . . . 5
3.6 Message Segmentation . . . . . . . . . . . . . . . . . . . . 7 3.6. Message Segmentation . . . . . . . . . . . . . . . . . 5
3.7 Support for Keep-Alive Mechanism . . . . . . . . . . . . . . 7 3.7. Support for Keep-Alive Mechanism . . . . . . . . . . . 6
3.8 Operation in NAT Environments . . . . . . . . . . . . . . . 8 3.8. Operation in NAT Environments . . . . . . . . . . . . . 6
3.9 Multiple Callout Servers . . . . . . . . . . . . . . . . . . 8 3.9. Multiple Callout Servers . . . . . . . . . . . . . . . 6
3.10 Multiple OPES Processors . . . . . . . . . . . . . . . . . . 8 3.10. Multiple OPES Processors . . . . . . . . . . . . . . . 6
3.11 Support for Different Application Protocols . . . . . . . . 8 3.11. Support for Different Application Protocols . . . . . . 7
3.12 Capability and Parameter Negotiations . . . . . . . . . . . 8 3.12. Capability and Parameter Negotiations . . . . . . . . . 7
3.13 Meta Data and Instructions . . . . . . . . . . . . . . . . . 9 3.13. Meta Data and Instructions . . . . . . . . . . . . . . 8
4. Performance Requirements . . . . . . . . . . . . . . . . . . 11 4. Performance Requirements . . . . . . . . . . . . . . . . . . 9
4.1 Protocol Efficiency . . . . . . . . . . . . . . . . . . . . 11 4.1. Protocol Efficiency . . . . . . . . . . . . . . . . . . 9
5. Security Requirements . . . . . . . . . . . . . . . . . . . 12 5. Security Requirements . . . . . . . . . . . . . . . . . . . . 9
5.1 Authentication, Confidentiality, and Integrity . . . . . . . 12 5.1. Authentication, Confidentiality, and Integrity . . . . 9
5.2 Hop-by-Hop Confidentiality . . . . . . . . . . . . . . . . . 12 5.2. Hop-by-Hop Confidentiality. . . . . . . . . . . . . . . 10
5.3 Operation Across Un-trusted Domains . . . . . . . . . . . . 12 5.3. Operation Across Untrusted Domains. . . . . . . . . . . 10
5.4 Privacy . . . . . . . . . . . . . . . . . . . . . . . . . . 13 5.4. Privacy . . . . . . . . . . . . . . . . . . . . . . . . 10
6. Security Considerations . . . . . . . . . . . . . . . . . . 14 6. Security Considerations . . . . . . . . . . . . . . . . . . . 10
Normative References . . . . . . . . . . . . . . . . . . . . 15 7. References. . . . . . . . . . . . . . . . . . . . . . . . . . 10
Informative References . . . . . . . . . . . . . . . . . . . 16 7.1. Normative References. . . . . . . . . . . . . . . . . . 10
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . 16 7.2. Informative References. . . . . . . . . . . . . . . . . 11
A. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . 18 8. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 11
B. Change Log . . . . . . . . . . . . . . . . . . . . . . . . . 19 9. Authors' Addresses. . . . . . . . . . . . . . . . . . . . . . 12
Intellectual Property and Copyright Statements . . . . . . . 21 10. Full Copyright Statement. . . . . . . . . . . . . . . . . . . 13
1. Terminology 1. Terminology
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in RFC 2119 [2]. document are to be interpreted as described in BCP 14, RFC 2119 [2].
2. Introduction 2. Introduction
The Open Pluggable Edge Services (OPES) architecture [1] enables The Open Pluggable Edge Services (OPES) architecture [1] enables
cooperative application services (OPES services) between a data cooperative application services (OPES services) between a data
provider, a data consumer, and zero or more OPES processors. The provider, a data consumer, and zero or more OPES processors. The
application services under consideration analyze and possibly application services under consideration analyze, and possibly
transform application-level messages exchanged between the data transform, application-level messages exchanged between the data
provider and the data consumer. provider and the data consumer.
The execution of such services is governed by a set of rules The execution of such services is governed by a set of rules
installed on the OPES processor. The rules enforcement can trigger installed on the OPES processor. The enforcement of rules can
the execution of service applications local to the OPES processor. trigger the execution of service applications local to the OPES
Alternatively, the OPES processor can distribute the responsibility processor. Alternatively, the OPES processor can distribute the
of service execution by communicating and collaborating with one or responsibility of service execution by communicating and
more remote callout servers. As described in [1], an OPES processor collaborating with one or more remote callout servers. As described
communicates with and invokes services on a callout server by using a in [1], an OPES processor communicates with and invokes services on a
callout protocol. This document presents the requirements for such a callout server by using a callout protocol. This document presents
protocol. the requirements for such a protocol.
The requirements in this document are divided into three categories - The requirements in this document are divided into three categories -
functional requirements, performance requirements, and security functional requirements, performance requirements, and security
requirements. Each requirement is presented as one or more requirements. Each requirement is presented as one or more
statements, followed by brief explanatory material as appropriate. statements, followed by brief explanatory material as appropriate.
3. Functional Requirements 3. Functional Requirements
3.1 Reliability 3.1. Reliability
The OPES callout protocol MUST be able to provide ordered reliability The OPES callout protocol MUST be able to provide ordered reliability
for the communication between OPES processor and callout server. for the communication between an OPES processor and callout server.
Additionally, the callout protocol SHOULD be able to provide Additionally, the callout protocol SHOULD be able to provide
unordered reliability. unordered reliability.
In order to satisfy the reliability requirements, the callout In order to satisfy the reliability requirements, the callout
protocol SHOULD specify that it must be used with a transport protocol SHOULD specify that it must be used with a transport
protocol which provides ordered/unordered reliability at the protocol that provides ordered/unordered reliability at the
transport-layer, for example TCP [6] or SCTP [7]. transport-layer, for example TCP [6] or SCTP [7].
3.2 Congestion Avoidance 3.2. Congestion Avoidance
The OPES callout protocol MUST ensure that congestion avoidance that The OPES callout protocol MUST ensure that congestion avoidance
matches the standard of RFC 2914 [4] is applied on all communication matching the standard of RFC 2914 [4] is applied on all communication
between OPES processor and callout server. For this purpose, the between the OPES processor and callout server. For this purpose, the
callout protocol SHOULD use a congestion-controlled transport-layer callout protocol SHOULD use a congestion-controlled transport-layer
protocol, presumably either TCP [6] or SCTP [7]. protocol, presumably either TCP [6] or SCTP [7].
3.3 Callout Transactions 3.3. Callout Transactions
The OPES callout protocol MUST enable an OPES processor and a callout The OPES callout protocol MUST enable an OPES processor and a callout
server to perform callout transactions with the purpose of exchanging server to perform callout transactions with the purpose of exchanging
partial or complete application-level protocol messages (or partial or complete application-level protocol messages (or
modifications thereof). More specifically, the callout protocol MUST modifications thereof). More specifically, the callout protocol MUST
enable an OPES processor to forward a partial or complete application enable an OPES processor to forward a partial or complete application
message to a callout server so that one or more OPES services can message to a callout server so that one or more OPES services can
process the forwarded application message (or parts thereof). The process the forwarded application message (or parts thereof). The
result of the service operation may be a modified application result of the service operation may be a modified application
message. The callout protocol MUST therefore enable the callout message. The callout protocol MUST therefore enable the callout
server to return a modified application message or the modified parts server to return a modified application message or the modified parts
of an application message to the OPES processor. Additionally, the of an application message to the OPES processor. Additionally, the
callout protocol MUST enable a callout server to report back to the callout protocol MUST enable a callout server to report the result of
OPES processor the result of a callout transaction, e.g. in the form a callout transaction (e.g., in the form of a status code) back to
of a status code. the OPES processor.
A callout transaction is defined as a message exchange between an A callout transaction is defined as a message exchange between an
OPES processor and a callout server consisting of a callout request OPES processor and a callout server consisting of a callout request
and a callout response. Both, the callout request as well as the and a callout response. Both, the callout request and the callout
callout response, MAY each consist of one or more callout protocol response MAY each consist of one or more callout protocol messages,
messages, i.e. a series of protocol messages. A callout request i.e. a series of protocol messages. A callout request MUST always
MUST always contain a partial or complete application message. A contain a partial or complete application message. A callout
callout response MUST always indicate the result of the callout response MUST always indicate the result of the callout transaction.
transaction. A callout response MAY contain a modified application A callout response MAY contain a modified application message.
message.
Callout transactions are always initiated by a callout request from Callout transactions are always initiated by a callout request from
an OPES processor and typically terminated by a callout response from an OPES processor and are typically terminated by a callout response
a callout server. The OPES callout protocol MUST, however, also from a callout server. The OPES callout protocol MUST, however, also
provide a mechanism that allows either endpoint of a callout provide a mechanism that allows either endpoint of a callout
transaction to terminate a callout transaction before a callout transaction to terminate a callout transaction before a callout
request or response has been completely received by the corresponding request or response has been completely received by the corresponding
callout endpoint. Such a mechanism MUST ensure that a premature callout endpoint. Such a mechanism MUST ensure that a premature
termination of a callout transaction does not result in the loss of termination of a callout transaction does not result in the loss of
application message data. application message data.
A premature termination of a callout transaction is required to A premature termination of a callout transaction is required to
support OPES services which may terminate even before they have support OPES services, which may terminate even before they have
processed the entire application message. Content analysis services, processed the entire application message. Content analysis services,
for example, may be able to classify a Web object after having for example, may be able to classify a Web object after having
processed just the first few bytes of a Web object. processed just the first few bytes of a Web object.
3.4 Callout Connections 3.4. Callout Connections
The OPES callout protocol MUST enable an OPES processor and a callout The OPES callout protocol MUST enable an OPES processor and a callout
server to perform multiple callout transactions over a callout server to perform multiple callout transactions over a callout
connection. Additionally, the callout protocol MUST provide a method connection. Additionally, the callout protocol MUST provide a method
to associate callout transactions with callout connections. A of associating callout transactions with callout connections. A
callout connection is defined as a logical connection at the callout connection is defined as a logical connection at the
application-layer between an OPES processor and a callout server. A application-layer between an OPES processor and a callout server. A
callout connection MAY have certain parameters associated with it, callout connection MAY have certain parameters associated with it,
for example parameters that control the fail-over behavior of for example parameters that control the fail-over behavior of
connection endpoints. Callout connection-specific parameters MAY be connection endpoints. Callout connection-specific parameters MAY be
negotiated between OPES processors and callout servers (see Section negotiated between OPES processors and callout servers (see Section
3.12). 3.12).
The OPES callout protocol MAY choose to multiplex multiple callout The OPES callout protocol MAY choose to multiplex multiple callout
connections over a single transport-layer connection so long as a connections over a single transport-layer connection if a flow
flow control mechanism is applied which guarantees fairness among control mechanism that guarantees fairness among multiplexed callout
multiplexed callout connections. connections is applied.
Callout connections MUST always be initiated by an OPES processor. A Callout connections MUST always be initiated by an OPES processor. A
callout connection MAY be closed by either endpoint of the connection callout connection MAY be closed by either endpoint of the
provided that doing so does not affect the normal operation of connection, provided that doing so does not affect the normal
on-going callout transactions associated with the callout connection. operation of on-going callout transactions associated with the
callout connection.
3.5 Asynchronous Message Exchange 3.5. Asynchronous Message Exchange
The OPES callout protocol MUST support an asynchronous message The OPES callout protocol MUST support an asynchronous message
exchange over callout connections. exchange over callout connections.
In order to allow asynchronous processing on the OPES processor and In order to allow asynchronous processing on the OPES processor and
callout server, it MUST be possible to separate request issuance from callout server, it MUST be possible to separate request issuance from
response processing. The protocol MUST therefore allow multiple response processing. The protocol MUST therefore allow multiple
outstanding callout requests and provide a method to correlate outstanding callout requests and provide a method of correlating
callout responses to callout requests. callout responses with callout requests.
Additionally, the callout protocol MUST enable a callout server to Additionally, the callout protocol MUST enable a callout server to
respond to a callout request before it has received the entire respond to a callout request before it has received the entire
request. request.
3.6 Message Segmentation 3.6. Message Segmentation
The OPES callout protocol MUST allow an OPES processor to forward an The OPES callout protocol MUST allow an OPES processor to forward an
application message to a callout server in a series of smaller application message to a callout server in a series of smaller
message fragments. The callout protocol MUST further enable the message fragments. The callout protocol MUST further enable the
receiving callout server to re-assemble the fragmented application receiving callout server to re-assemble the fragmented application
message. message.
Likewise, the callout protocol MUST enable a callout server to return Likewise, the callout protocol MUST enable a callout server to return
an application message to an OPES processor in a series of smaller an application message to an OPES processor in a series of smaller
message fragments. The callout protocol MUST enable the receiving message fragments. The callout protocol MUST enable the receiving
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fragments or chunks of an application message to a callout server as fragments or chunks of an application message to a callout server as
it receives them from the data provider or consumer. Likewise, the it receives them from the data provider or consumer. Likewise, the
callout server MUST be able to process and return application message callout server MUST be able to process and return application message
fragments as it receives them from the OPES processor. fragments as it receives them from the OPES processor.
Application message segmentation is also required if the OPES callout Application message segmentation is also required if the OPES callout
protocol provides a flow control mechanism in order to multiplex protocol provides a flow control mechanism in order to multiplex
multiple callout connections over a single transport-layer connection multiple callout connections over a single transport-layer connection
(see Section 3.4). (see Section 3.4).
3.7 Support for Keep-Alive Mechanism 3.7. Support for Keep-Alive Mechanism
The OPES callout protocol MUST provide a keep-alive mechanism which, The OPES callout protocol MUST provide a keep-alive mechanism which,
if used, would allow both endpoints of a callout connection to detect if used, would allow both endpoints of a callout connection to detect
a failure of the other endpoint even in the absence of callout a failure of the other endpoint, even in the absence of callout
transactions. The callout protocol MAY specify that keep-alive transactions. The callout protocol MAY specify that keep-alive
messages be exchanged over existing callout connections or a separate messages be exchanged over existing callout connections or a separate
connection between OPES processor and callout server. The callout connection between OPES processor and callout server. The callout
protocol MAY also specify that the use of the keep-alive mechanism is protocol MAY also specify that the use of the keep-alive mechanism is
optional. optional.
The detection of a callout server failure may enable an OPES The detection of a callout server failure may enable an OPES
processor to establish a callout connection with a stand-by callout processor to establish a callout connection with a stand-by callout
server so that future callout transactions do not result in the loss server so that future callout transactions do not result in the loss
of application message data. The detection of the failure of an OPES of application message data. The detection of the failure of an OPES
processor may enable a callout server to release resources which processor may enable a callout server to release resources which
would otherwise not be available for callout transactions with other would otherwise not be available for callout transactions with other
OPES processors. OPES processors.
3.8 Operation in NAT Environments 3.8. Operation in NAT Environments
The OPES protocol SHOULD be NAT-friendly, i.e. its operation should The OPES protocol SHOULD be NAT-friendly, i.e., its operation should
not be compromised by the presence of one or more NAT devices in the not be compromised by the presence of one or more NAT devices in the
path between an OPES processor and a callout server. path between an OPES processor and a callout server.
3.9 Multiple Callout Servers 3.9. Multiple Callout Servers
The OPES callout protocol MUST allow an OPES processor to The OPES callout protocol MUST allow an OPES processor to
simultaneously communicate with more than one callout server. simultaneously communicate with more than one callout server.
In larger networks, OPES services are likely to be hosted by In larger networks, OPES services are likely to be hosted by
different callout servers. Therefore, an OPES processor will likely different callout servers. Therefore, an OPES processor will likely
have to communicate with multiple callout servers. The protocol have to communicate with multiple callout servers. The protocol
design MUST enable an OPES processor to do so. design MUST enable an OPES processor to do so.
3.10 Multiple OPES Processors 3.10. Multiple OPES Processors
The OPES callout protocol MUST allow a callout server to The OPES callout protocol MUST allow a callout server to
simultaneously communicate with more than one OPES processor. simultaneously communicate with more than one OPES processor.
The protocol design MUST support a scenario in which multiple OPES The protocol design MUST support a scenario in which multiple OPES
processors use the services of a single callout server. processors use the services of a single callout server.
3.11 Support for Different Application Protocols 3.11. Support for Different Application Protocols
The OPES callout protocol SHOULD be application protocol-agnostic, The OPES callout protocol SHOULD be application protocol-agnostic,
i.e. it SHOULD not make any assumptions about the characteristics of i.e., it SHOULD not make any assumptions about the characteristics of
the application-layer protocol used on the data path between data the application-layer protocol used on the data path between the data
provider and data consumer. At a minimum, the callout protocol MUST provider and data consumer. At a minimum, the callout protocol MUST
be compatible with HTTP [5]. be compatible with HTTP [5].
The OPES entities on the data path may use different The OPES entities on the data path may use different application-
application-layer protocols, including, but not limited to, HTTP [5] layer protocols, including, but not limited to, HTTP [5] and RTP [8].
and RTP [8]. It would be desirable to be able to use the same OPES It would be desirable to be able to use the same OPES callout
callout protocol for any such application-layer protocol. protocol for any such application-layer protocol.
3.12 Capability and Parameter Negotiations 3.12. Capability and Parameter Negotiations
The OPES callout protocol MUST support the negotiation of The OPES callout protocol MUST support the negotiation of
capabilities and callout connection parameters between an OPES capabilities and callout connection parameters between an OPES
processor and a callout server. This implies that the OPES processor processor and a callout server. This implies that the OPES processor
and the callout server MUST be able to exchange their capabilities and the callout server MUST be able to exchange their capabilities
and preferences and engage into a deterministic negotiation process and preferences. Then they MUST be able to engage in a deterministic
at the end of which the two endpoints have either agreed on the negotiation process that terminates either with the two endpoints
capabilities and parameters to be used for future callout agreeing on the capabilities and parameters to be used for future
connections/transactions or determined that their capabilities are callout connections/transactions or with a determination that their
incompatible. capabilities are incompatible.
Capabilities and parameters that could be negotiated between an OPES Capabilities and parameters that could be negotiated between an OPES
processor and a callout server include (but are not limited to): processor and a callout server include (but are not limited to):
callout protocol version, fail-over behavior, heartbeat rate for callout protocol version, fail-over behavior, heartbeat rate for
keep-alive messages, security-related parameters etc. keep-alive messages, security-related parameters, etc.
The callout protocol MUST NOT negotiate the transport protocol to be The callout protocol MUST NOT use negotiation to determine the
used for callout connections. The callout protocol MAY, however, transport protocol to be used for callout connections. The callout
specify that a certain application message protocol (e.g. HTTP [5], protocol MAY, however, specify that a certain application message
RTP [8]) requires the use of a certain transport protocol (e.g. TCP protocol (e.g., HTTP [5], RTP [8]) requires the use of a certain
[6], SCTP [7]). transport protocol (e.g., TCP [6], SCTP [7]).
Callout connection parameters may also pertain to the characteristics Callout connection parameters may also pertain to the characteristics
of OPES callout services if, for example, callout connections are of OPES callout services if, for example, callout connections are
associated with one or more specific OPES services. An OPES associated with one or more specific OPES services. An OPES
service-specific parameter may, for example, specify which parts of service-specific parameter may, for example, specify which parts of
an application message an OPES service requires for its operation. an application message an OPES service requires for its operation.
Callout connection parameters MUST be negotiated on a per-callout Callout connection parameters MUST be negotiated on a per-callout
connection basis and before any callout transactions are performed connection basis and before any callout transactions are performed
over the corresponding callout connection. Other parameters and over the corresponding callout connection. Other parameters and
capabilities, such as the fail-over behavior, MAY be negotiated capabilities, such as the fail-over behavior, MAY be negotiated
between the two endpoints independently of callout connections. between the two endpoints independently of callout connections.
The parties to a callout protocol MAY use callout connections to The parties to a callout protocol MAY use callout connections to
negotiate all or some of their capabilities and parameters. negotiate all or some of their capabilities and parameters.
Alternatively, a separate control connection MAY be used for this Alternatively, a separate control connection MAY be used for this
purpose. purpose.
3.13 Meta Data and Instructions 3.13. Meta Data and Instructions
The OPES callout protocol MUST provide a mechanism for the endpoints The OPES callout protocol MUST provide a mechanism for the endpoints
of a particular callout transaction to include in callout requests of a particular callout transaction to include metadata and
and responses meta data and instructions for the OPES processor or instructions for the OPES processor or callout server in callout
callout server. requests and responses.
Specifically, the callout protocol MUST enable an OPES processor to Specifically, the callout protocol MUST enable an OPES processor to
include information about the forwarded application message in a include information about the forwarded application message in a
callout request, e.g. in order to specify the type of the forwarded callout request, e.g. in order to specify the type of forwarded
application message or to specify what part(s) of the application application message or to specify what part(s) of the application
message are forwarded to the callout server. Likewise, the callout message are forwarded to the callout server. Likewise, the callout
server MUST be able to include information about the returned server MUST be able to include information about the returned
application message. application message.
The OPES processor MUST further be able to include an ordered list of The OPES processor MUST further be able to include an ordered list of
one or more uniquely specified OPES services which are to be one or more uniquely specified OPES services which are to be
performed on the forwarded application message in the specified performed on the forwarded application message in the specified
order. However, as the callout protocol MAY also choose to associate order. However, as the callout protocol MAY also choose to associate
callout connections with specific OPES services, there may not be a callout connections with specific OPES services, there may not be a
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Additionally, the OPES callout protocol MUST allow the callout server Additionally, the OPES callout protocol MUST allow the callout server
to indicate to the OPES processor the cacheability of callout to indicate to the OPES processor the cacheability of callout
responses. This implies that callout responses may have to carry responses. This implies that callout responses may have to carry
cache-control instructions for the OPES processor. cache-control instructions for the OPES processor.
The OPES callout protocol MUST further enable the OPES processor to The OPES callout protocol MUST further enable the OPES processor to
indicate to the callout server if it has kept a local copy of the indicate to the callout server if it has kept a local copy of the
forwarded application message (or parts thereof). This information forwarded application message (or parts thereof). This information
enables the callout server to determine whether the forwarded enables the callout server to determine whether the forwarded
application message must be returned to the OPES processor even it application message must be returned to the OPES processor, even if
has not been modified by an OPES service. it has not been modified by an OPES service.
The OPES callout protocol MUST also allow OPES processors to comply The OPES callout protocol MUST also allow OPES processors to comply
with the tracing requirements of the OPES architecture as laid out in with the tracing requirements of the OPES architecture as laid out in
[1] and [3]. This implies that the callout protocol MUST enable a [1] and [3]. This implies that the callout protocol MUST enable a
callout server to convey to the OPES processor information about the callout server to convey to the OPES processor information about the
OPES service operations performed on the forwarded application OPES service operations performed on the forwarded application
message. message.
4. Performance Requirements 4. Performance Requirements
4.1 Protocol Efficiency 4.1. Protocol Efficiency
The OPES callout protocol SHOULD be efficient in that it minimizes The OPES callout protocol SHOULD have minimal latency. For example,
the additionally introduced latency, for example by minimizing the the size and complexity of its headers could be minimized.
protocol overhead.
As OPES callout transactions introduce additional latency to Because OPES callout transactions add latency to application protocol
application protocol transactions on the data path, callout protocol transactions on the data path, callout protocol efficiency is crucial
efficiency is crucial. to overall performance.
5. Security Requirements 5. Security Requirements
In the absence of any security mechanisms, sensitive information In the absence of any security mechanisms, sensitive information
might be communicated between the OPES processor and the callout might be communicated between the OPES processor and the callout
server in violation of either endpoint's security and privacy policy server in violation of either endpoint's security and privacy policy,
through misconfiguration or a deliberate insider attack. By using through misconfiguration or deliberate insider attack. By using
strong authentication, message encryption, and integrity checks, this strong authentication, message encryption, and integrity checks, this
threat can be minimized to a smaller set of insiders and/or operator threat can be minimized to a smaller set of insiders and/or operator
configuration errors. configuration errors.
The OPES processor and the callout servers SHOULD have enforceable The OPES processor and the callout servers SHOULD have enforceable
policies that limit the parties they communicate with, that determine policies that limit the parties they communicate with and that
the protections to use based on identities of the endpoints and other determine the protections to use based on identities of the endpoints
data (such as enduser policies). In order to enforce the policies, and other data (such as enduser policies). In order to enforce the
they MUST be able to authenticate the callout protocol endpoints policies, they MUST be able to authenticate the callout protocol
using cryptographic methods. endpoints using cryptographic methods.
5.1 Authentication, Confidentiality, and Integrity 5.1. Authentication, Confidentiality, and Integrity
The parties to the callout protocol MUST have a sound basis for The parties to the callout protocol MUST have a sound basis for
binding authenticated identities to the protocol endpoints, and they binding authenticated identities to the protocol endpoints, and they
MUST verify that these identities are consistent with their security MUST verify that these identities are consistent with their security
policies. policies.
The OPES callout protocol MUST provide for message authentication, The OPES callout protocol MUST provide for message authentication,
confidentiality, and integrity between the OPES processor and the confidentiality, and integrity between the OPES processor and the
callout server. It MUST provide mutual authentication. For this callout server. It MUST provide mutual authentication. For this
purpose, the callout protocol SHOULD use existing security purpose, the callout protocol SHOULD use existing security
mechanisms. The callout protocol specification is not required to mechanisms. The callout protocol specification is not required to
specify the security mechanisms, but it MAY instead refer to a specify the security mechanisms, but it MAY instead refer to a
lower-level security protocol and discuss how its mechanisms are to lower-level security protocol and discuss how its mechanisms are to
be used with the callout protocol. be used with the callout protocol.
5.2 Hop-by-Hop Confidentiality 5.2. Hop-by-Hop Confidentiality
If end-to-end encryption is a requirement for the content path, then If hop-by-hop encryption is a requirement for the content path, then
this confidentiality MUST be extended to the communication between this confidentiality MUST be extended to the communication between
the OPES processor and the callout server. While it is recommended the OPES processor and the callout server. While it is recommended
that the communication between OPES processor and callout server that the communication between the OPES processor and callout server
always be encrypted, encryption MAY be optional if both the OPES always be encrypted, encryption MAY be optional if both the OPES
processor and the callout server are co-located with each other in a processor and the callout server are co-located together in a single
single administrative domain with strong confidentiality guarantees. administrative domain with strong confidentiality guarantees.
In order to minimize data exposure, the callout protocol MUST use a In order to minimize data exposure, the callout protocol MUST use a
different encryption key for each encrypted content stream. different encryption key for each encrypted content stream.
5.3 Operation Across Un-trusted Domains 5.3. Operation Across Untrusted Domains
The OPES callout protocol MUST operate securely across un-trusted
The OPES callout protocol MUST operate securely across untrusted
domains between the OPES processor and the callout server. domains between the OPES processor and the callout server.
If the communication channels between the OPES processor and callout If the communication channels between the OPES processor and callout
server cross outside of the organization taking responsibility for server cross outside of the organization which is responsible for the
the OPES services, then endpoint authentication and message OPES services, then endpoint authentication and message protection
protection (confidentiality and integrity) MUST be used. (confidentiality and integrity) MUST be used.
5.4 Privacy 5.4. Privacy
Any communication carrying information relevant to privacy policies Any communication carrying information relevant to privacy policies
MUST protect the data using encryption. MUST protect the data using encryption.
6. Security Considerations 6. Security Considerations
The security requirements for the OPES callout protocol are discussed The security requirements for the OPES callout protocol are discussed
in Section 5. in Section 5.
Normative References 7. References
[1] Barbir, A., "An Architecture for Open Pluggable Edge Services 7.1. Normative References
(OPES)", draft-ietf-opes-architecture-04 (work in progress),
December 2002. [1] Barbir, A., Penno, R., Chen, R., Hofmann, M., and H. Orman, "An
Architecture for Open Pluggable Edge Services (OPES)", RFC 3835,
August 2004.
[2] Bradner, S., "Key words for use in RFCs to Indicate Requirement [2] Bradner, S., "Key words for use in RFCs to Indicate Requirement
Levels", RFC 2119, March 1997. Levels", BCP 14, RFC 2119, March 1997.
[3] Floyd, S. and L. Daigle, "IAB Architectural and Policy [3] Floyd, S. and L. Daigle, "IAB Architectural and Policy
Considerations for Open Pluggable Edge Services", RFC 3238, Considerations for Open Pluggable Edge Services", RFC 3238,
January 2002. January 2002.
[4] Floyd, S., "Congestion Control Principles", BCP 41, RFC 2914, [4] Floyd, S. and L. Daigle, "IAB Architectural and Policy
September 2000. Considerations for Open Pluggable Edge Services", RFC 3238,
January 2002.
[5] Fielding, R., Gettys, J., Mogul, J., Nielsen, H., Masinter, L., [5] Fielding, R., Gettys, J., Mogul, J., Frystyk, H., Masinter, L.,
Leach, P. and T. Berners-Lee, "Hypertext Transfer Protocol -- Leach, P., and T. Berners-Lee, "Hypertext Transfer Protocol --
HTTP/1.1", RFC 2616, June 1999. HTTP/1.1", RFC 2616, June 1999.
Informative References 7.2. Informative References
[6] Postel, J., "Transmission Control Protocol", STD 7, RFC 793, [6] Postel, J., "Transmission Control Protocol", STD 7, RFC 793,
September 1981. September 1981.
[7] Stewart, R., Xie, Q., Morneault, K., Sharp, C., Schwarzbauer, [7] Stewart, R., Xie, Q., Morneault, K., Sharp, C., Schwarzbauer,
H., Taylor, T., Rytina, I., Kalla, M., Zhang, L. and V. Paxson, H., Taylor, T., Rytina, I., Kalla, M., Zhang, L., and V. Paxson,
"Stream Control Transmission Protocol", RFC 2960, October 2000. "Stream Control Transmission Protocol", RFC 2960, October 2000.
[8] Schulzrinne, H., Casner, S., Frederick, R. and V. Jacobson, [8] Schulzrinne, H., Casner, S., Frederick, R., and V. Jacobson,
"RTP: A Transport Protocol for Real-Time Applications", RFC "RTP: A Transport Protocol for Real-Time Applications", RFC
1889, January 1996. 3550, July 2003.
Authors' Addresses 8. Acknowledgments
Parts of this document are based on previous work by Anca Dracinschi
Sailer, Volker Hilt, and Rama R. Menon.
The authors would like to thank the participants of the OPES WG for
their comments on this document.
9. Authors' Addresses
Andre Beck Andre Beck
Lucent Technologies Lucent Technologies
101 Crawfords Corner Road 101 Crawfords Corner Road
Holmdel, NJ 07733 Holmdel, NJ 07733
US US
EMail: abeck@bell-labs.com EMail: abeck@bell-labs.com
Markus Hofmann Markus Hofmann
skipping to change at page 17, line 4 skipping to change at page 12, line 30
US US
Phone: +1 732 332 5983 Phone: +1 732 332 5983
EMail: hofmann@bell-labs.com EMail: hofmann@bell-labs.com
Hilarie Orman Hilarie Orman
Purple Streak Development Purple Streak Development
EMail: ho@alum.mit.edu EMail: ho@alum.mit.edu
URI: http://www.purplestreak.com URI: http://www.purplestreak.com
Reinaldo Penno Reinaldo Penno
Nortel Networks Nortel Networks
2305 Mission College Boulevard 600 Technology Park Drive
San Jose, CA 95134 Billerica, MA 01821
US US
EMail: rpenno@nortelnetworks.com EMail: rpenno@nortelnetworks.com
Andreas Terzis Andreas Terzis
Individual Consultant Computer Science Department
150 Golf Course Dr. Johns Hopkins University
Rohnert Park, CA 94928 3400 North Charles Street, 224 NEB
US Baltimore, MD 21218
Phone: +1 707 586 8864
EMail: aterzis@sbcglobal.net
Appendix A. Acknowledgments
This document is based in parts on previous work by Anca Dracinschi
Sailer, Volker Hilt, and Rama R. Menon.
The authors would like to thank the participants of the OPES WG for
their comments on this draft.
Appendix B. Change Log
Changes from draft-ietf-opes-protocol-reqs-02.txt
o Re-ordered some sections in the functional requirements part of
the draft
o Clarified in Section 3.3 what callout requests and responses must/
may contain
o Removed reference to explicit and implicit mechanism of
terminating a callout transaction prematurely in Section 3.3
o Added reference to RFC 2914 in congestion avoidance requirement in
Section 3.2
o Added language that states that existing solutions should be used
to achieve congestion avoidance and ordered/unordered reliability
in Section 3.2 and Section 3.1
o Clarified concept of callout connections (previously referred to
as "callout channels") in Section 3.4
o Added statement about the possibility of multiplexing multiple
callout connections over a transport connection to Section 3.4
o Clarified in Section 3.7 that use of a keep-alive mechanism is
optional
o Replaced "MUST" with "SHOULD" in OCP requirement to be application
protocol-agnostic in Section 3.11, added explicit requirement to
support HTTP
o Removed "transport protocol" from list of callout parameters which
may be negotiated, added suggestion to pick transport protocol
depending on the application protocol in Section 3.12.
o Explained that application message segementation is also necessary
for multiplexing callout connections over transport connections in
Section 3.6
o Added statement to Section 5.2 that encryption between OPES
processor and callout server may be optional if they are
co-located with each other in a single administrative domain
Changes from draft-ietf-opes-protocol-reqs-01.txt
o Reworded and clarified several statements of the draft
Changes from draft-ietf-opes-protocol-reqs-00.txt Phone: +1 410 516 5847
EMail: terzis@cs.jhu.edu
o Aligned terminology with [1] 10. Full Copyright Statement
o Clarified in Section 3.13 that OCP requests not only have to Copyright (C) The Internet Society (2004). This document is subject
identify one or more OPES services, but also the order in which to the rights, licenses and restrictions contained in BCP 78, and
the services are to be executed except as set forth therein, the authors retain all their rights.
o Removed requirement from Section 4.1 that OCP must satisfy This document and the information contained herein are provided on an
performance requirements of the application-layer protocol used "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS
between data consumer and provider OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY AND THE INTERNET
ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS OR IMPLIED,
INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE
INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED
WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.
Intellectual Property Statement Intellectual Property
The IETF takes no position regarding the validity or scope of any The IETF takes no position regarding the validity or scope of any
intellectual property or other rights that might be claimed to Intellectual Property Rights or other rights that might be claimed to
pertain to the implementation or use of the technology described in pertain to the implementation or use of the technology described in
this document or the extent to which any license under such rights this document or the extent to which any license under such rights
might or might not be available; neither does it represent that it might or might not be available; nor does it represent that it has
has made any effort to identify any such rights. Information on the made any independent effort to identify any such rights. Information
IETF's procedures with respect to rights in standards-track and on the procedures with respect to rights in RFC documents can be
standards-related documentation can be found in BCP-11. Copies of found in BCP 78 and BCP 79.
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The IETF invites any interested party to bring to its attention any The IETF invites any interested party to bring to its attention any
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Full Copyright Statement
Copyright (C) The Internet Society (2002). All Rights Reserved.
This document and translations of it may be copied and furnished to
others, and derivative works that comment on or otherwise explain it
or assist in its implementation may be prepared, copied, published
and distributed, in whole or in part, without restriction of any
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included on all such copies and derivative works. However, this
document itself may not be modified in any way, such as by removing
the copyright notice or references to the Internet Society or other
Internet organizations, except as needed for the purpose of
developing Internet standards in which case the procedures for
copyrights defined in the Internet Standards process must be
followed, or as required to translate it into languages other than
English.
The limited permissions granted above are perpetual and will not be
revoked by the Internet Society or its successors or assignees.
This document and the information contained herein is provided on an
"AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING
TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING
BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION
HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF
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Acknowledgement Acknowledgement
Funding for the RFC Editor function is currently provided by the Funding for the RFC Editor function is currently provided by the
Internet Society. Internet Society.
 End of changes. 

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