Requirements for Separation of IP Control and Forwarding
RFC 3654

• Status
• IESG evaluation record
• IESG writeups
• Email expansions
• History

• Versions
• 10

Network Working Group                                   H. Khosravi, Ed.
Request for Comments: 3654                              T. Anderson, Ed.
Category: Informational                                            Intel
                                                           November 2003

       Requirements for Separation of IP Control and Forwarding

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 (2003).  All Rights Reserved.

Abstract

   This document introduces the Forwarding and Control Element
   Separation (ForCES) architecture and defines a set of associated
   terminology.  This document also defines a set of architectural,
   modeling, and protocol requirements to logically separate the control
   and data forwarding planes of an IP (IPv4, IPv6, etc.) networking
   device.

Table of Contents

   1.  Introduction. . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Definitions . . . . . . . . . . . . . . . . . . . . . . . . .   2
   3.  Architecture. . . . . . . . . . . . . . . . . . . . . . . . .   4
   4.  Architectural Requirements. . . . . . . . . . . . . . . . . .   5
   5.  FE Model Requirements . . . . . . . . . . . . . . . . . . . .   7
       5.1.  Types of Logical Functions. . . . . . . . . . . . . . .   8
       5.2.  Variations of Logical Functions . . . . . . . . . . . .   8
       5.3.  Ordering of Logical Functions . . . . . . . . . . . . .   8
       5.4.  Flexibility . . . . . . . . . . . . . . . . . . . . . .   8
       5.5   Minimal Set of Logical Functions. . . . . . . . . . . .   9
   6.  ForCES Protocol Requirements. . . . . . . . . . . . . . . . .  10
   7.  References. . . . . . . . . . . . . . . . . . . . . . . . . .  14
       7.1.  Normative References. . . . . . . . . . . . . . . . . .  14
       7.2.  Informative References. . . . . . . . . . . . . . . . .  15
   8.  Security Considerations . . . . . . . . . . . . . . . . . . .  15
   9.  Authors' Addresses & Acknowledgments. . . . . . . . . . . . .  15
   10. Editors' Contact Information. . . . . . . . . . . . . . . . .  17
   11. Full Copyright Statement. . . . . . . . . . . . . . . . . . .  18

Khosravi & Anderson          Informational                      [Page 1]
RFC 3654                  ForCES Requirements              November 2003

1. Introduction

   An IP network element is composed of numerous logically separate
   entities that cooperate to provide a given functionality (such as a
   routing or IP switching) and yet appear as a normal integrated
   network element to external entities.  Two primary types of network
   element components exist: control-plane components and forwarding-
   plane components.  In general, forwarding-plane components are ASIC,
   network-processor, or general-purpose processor-based devices that
   handle all data path operations.  Conversely, control-plane
   components are typically based on general-purpose processors that
   provide control functionality such as the processing of routing or
   signaling protocols.  A standard set of mechanisms for connecting
   these components provides increased scalability and allows the
   control and forwarding planes to evolve independently, thus promoting
   faster innovation.

   For the purpose of illustration, let us consider the architecture of
   a router to illustrate the concept of separate control and forwarding
   planes.  The architecture of a router is composed of two main parts.
   These components, while inter-related, perform functions that are
   largely independent of each other.  At the bottom is the forwarding
   path that operates in the data-forwarding plane and is responsible
   for per-packet processing and forwarding.  Above the forwarding plane
   is the network operating system that is responsible for operations in
   the control plane.  In the case of a router or switch, the network
   operating system runs routing, signaling and control protocols (e.g.,
   RIP, OSPF and RSVP) and dictates the forwarding behavior by
   manipulating forwarding tables, per-flow QoS tables and access
   control lists.  Typically, the architecture of these devices combines
   all of this functionality into a single functional whole with respect
   to external entities.

2. Definitions

   Addressable Entity (AE) - A physical device that is directly
   addressable given some interconnect technology.  For example, on IP
   networks, it is a device to which we can communicate using an IP
   address; and on a switch fabric, it is a device to which we can
   communicate using a switch fabric port number.

   Physical Forwarding Element (PFE) - An AE that includes hardware used
   to provide per-packet processing and handling.  This hardware may
   consist of (but is not limited to) network processors, ASIC's, line
   cards with multiple chips or stand alone box with general-purpose