rfc3304.txt

RFC 的详细文档！

Network Working Group                                        R. P. Swale
Request for Comments: 3304                          BTexact Technologies
Category: Informational                                       P. A. Mart
                                                  Marconi Communications
                                                               P. Sijben
                                                     Lucent Technologies
                                                                 S. Brim
                                                                M. Shore
                                                           Cisco Systems
                                                             August 2002


        Middlebox Communications (midcom) Protocol Requirements

Status of this Memo

   This memo provides information for the Internet community.  It does
   not specify an Internet standard of any kind.  Distribution of this
   memo is unlimited.

Copyright Notice

   Copyright (C) The Internet Society (2002).  All Rights Reserved.

Abstract

   This document specifies the requirements that the Middlebox
   Communication (midcom) protocol must satisfy in order to meet the
   needs of applications wishing to influence the middlebox function.
   These requirements were developed with a specific focus on network
   address translation and firewall middleboxes.

1.  Introduction

   This document is one of two developed by the Middlebox Communication
   (midcom) working group to address the requirements and framework for
   a protocol between middleboxes and "midcom agents."  This document
   presents midcom requirements; [MCFW] presents the context and
   framework.  [MCFW] also presents terminology and definitions and
   should be read in tandem with this one.

   These requirements were developed by examining the midcom framework
   and extracting requirements, both explicit and implicit, that
   appeared there.







Swale, et al.                Informational                      [Page 1]

RFC 3304                  Midcom Requirements                August 2002


2.  Requirements

   Each requirement is presented as a statement, followed by brief
   explanatory material as appropriate.  Terminology is defined in
   [MCFW].  There may be overlap between requirements.

2.1.  Protocol machinery

2.1.1.

   The Midcom protocol must enable a Midcom agent requiring the services
   of a middlebox to establish an authorized association between itself
   and the middlebox.

   This states that the protocol must allow the middlebox to identify an
   agent requesting services and make a determination as to whether or
   not the agent will be permitted to do so.

2.1.2.

   The Midcom protocol must allow a Midcom agent to communicate with
   more than one middlebox simultaneously.

   In any but the most simple network, an agent is likely to want to
   influence the behavior of more than one middlebox.  The protocol
   design must not preclude the ability to do this.

2.1.3.

   The Midcom protocol must allow a middlebox to communicate with more
   than one Midcom agent simultaneously.

   There may be multiple instances of a single application or multiple
   applications desiring service from a single middlebox, and different
   agents may represent them.  The protocol design must not preclude the
   ability to do so.

2.1.4.

   Where a multiplicity of Midcom Agents are interacting with a given
   middlebox, the Midcom protocol must provide mechanisms ensuring that
   the overall behavior is deterministic.

   This states that the protocol must include mechanisms for avoiding
   race conditions or other situations in which the requests of one
   agent may influence the results of the requests of other agents in an
   unpredictable manner.




Swale, et al.                Informational                      [Page 2]

RFC 3304                  Midcom Requirements                August 2002


2.1.5.

   The Midcom protocol must enable the middlebox and any associated
   Midcom agents to establish a known and stable state.  This must
   include the case of power failure, or other failure, where the
   protocol must ensure that any resources used by a failed element can
   be released.

   This states that the protocol must provide clear identification for
   requests and results and that protocol operations must be atomic with
   respect to the midcom protocol.

2.1.6.

   The middlebox must be able to report its status to a Midcom agent
   with which it is associated.

2.1.7.

   The protocol must support unsolicited messages from middlebox to
   agent, for reporting conditions detected asynchronously at the
   middlebox.

   It may be the case that exceptional conditions or other events at the
   middlebox (resource shortages, intrusion mitigation) will cause the
   middlebox to close pinholes or release resources without consulting
   the associated Midcom agent.  In that event, the protocol must allow
   the middlebox to notify the agent.

2.1.8.

   The Midcom protocol must provide for the mutual authentication of
   Midcom agent and middlebox to one another.

   In addition for the more obvious need for the Midcom agent to
   authenticate itself to the middlebox, there are some attacks against
   the protocol which can be mitigated by having the middlebox
   authenticate to the agent.  See [MCFW].

2.1.9.

   The Midcom protocol must allow either the Midcom agent or the
   middlebox to terminate the Midcom session between a Midcom Agent and
   a middlebox.  This allows either entity to close the session for
   maintenance, security, or other reasons.






Swale, et al.                Informational                      [Page 3]

RFC 3304                  Midcom Requirements                August 2002


2.1.10.

   A Midcom agent must be able to determine whether or not a request was
   successful.

   This states that a middlebox must return a success or failure
   indication to a request made by an agent.

2.1.11.

   The Midcom protocol must contain version interworking capabilities to
   enable subsequent extensions to support different types of middlebox
   and future requirements of applications not considered at this stage.

   We assume that there will be later revisions of this protocol.  The
   initial version will focus on communication with firewalls and NATs,
   and it is possible that the protocol will need to be modified, as
   support for other middlebox types is added.  These version
   interworking capabilities may include (but are not limited to) a
   protocol version number.

2.1.12.

   It must be possible to deterministically predict the behavior of the
   middlebox in the presence of overlapping rules.

   The protocol must preclude nondeterministic behavior in the case of
   overlapping rulesets, e.g. by ensuring that some known precedence is
   imposed.

2.2.  Midcom Protocol Semantics

2.2.1.

   The syntax and semantics of the Midcom protocol must be extensible to
   allow the requirements of future applications to be adopted.

   This is related to, but different from, the requirement for
   versioning support.  As support for additional middlebox types is
   added there may be a need to add new message types.

2.2.2.

   The Midcom protocol must support the ability of an agent to install a
   ruleset that governs multiple types of middlebox actions (e.g.
   firewall and NAT).





Swale, et al.                Informational                      [Page 4]

RFC 3304                  Midcom Requirements                August 2002


   This states that a the protocol must support rules and actions for a
   variety of types of middleboxes.  A Midcom agent ought to be able to
   have a single Midcom session with a middlebox and use the Midcom
   interface on the middlebox to interface with different middlebox
   functions on the same middlebox interface.

2.2.3.

   The protocol must support the concept of a ruleset group comprising a
   multiple of individual rulesets to be treated as an aggregate.

   Applications using more than one data stream may find it more
   convenient and more efficient to be able to use single messages to
   tear down, extend, and manipulate all middlebox rulesets being used
   by one instance of the application.

2.2.4.

   The protocol must allow the midcom agent to extend the lifetime of an
   existing ruleset that otherwise would be deleted by the middlebox.

2.2.5.

   If a peer does not understand an option, it must be clear whether the