sFlow.org                                                    Peter Phaal
http://www.sFlow.org/                                        InMon Corp.
info@sflow.org
                                                               Ben Pfaff
                                                            Nicira, Inc.


                                                            January 2010


                       sFlow OpenFlow Structures



Copyright Notice

Copyright (C) sFlow.org (2010). All Rights Reserved.

Abstract

This memo describes sFlow version 5 structures for exporting OpenFlow
related data.

Table of Contents

1. Overview ......................................................  1
2. Discussion ....................................................  1
3. sFlow Datagram Extensions .....................................  2
4. References ....................................................  3
5. Author's Addresses ............................................  3

1. Overview
   This document describes additional structures that allow an sFlow
   agent to export additional information when packet forwarding
   decisions are based on the OpenFlow [1] protocol.  sFlow version 5 is
   an extensible protocol that allows the addition of new data
   structures without impacting existing collectors. This document does
   not change the sFlow version 5 protocol [2], it simply defines
   additional, optional, data structures that an sFlow agent can use to
   report forwarding decisions.

2. Discussion

   The OpenFlow protocol allows a central traffic controller to manage
   forwarding decisions in network switches. This architecture
   complements the sFlow architecture in which a central sFlow analyzer
   monitors forwarding decisions and traffic from the switches in the
   network. Extending sFlow to report on OpenFlow specific forwarding



DRAFT                           sFlow.org                       [Page 1]

Version 0.1             sFlow OpenFlow Structures           January 2010


   decisions will aid in the troubleshooting and performance monitoring
   of OpenFlow networks.

   An additional goal of this extension is to facilitate close
   coordination between the sFlow analyzer and the OpenFlow controller.
   The combination of sFlow's real-time traffic monitoring and
   OpenFlow's real-time traffic control capabilities offer the
   possiblity of integrated, closed-loop control systems that automate
   network provisioning and capacity management.

   Version 1.0 of the OpenFlow protocol adds the concept of a "flow
   cookie". The OpenFlow controller can send the cookie to the switch
   when it configures a forwarding path. Exporting the cookie as part of
   the sFlow record associated with a forwarded packet "closes the
   loop", allowing traffic measurements to be associated with OpenFlow
   controller forwarding policies.

3. sFlow Datagram Extensions

   The following structures are defined to report on OpenFlow
   forwarding:

/* OpenFlow 1.0 Data */

/* Data structure for exporting OpenFlow 1.0 forwarding state
   See http://www.openflowswitch.org/ for field definitions
   Note: Bit definitions must be consistent with the OpenFlow
         version 1.0 specification. If later versions of
         OpenFlow define additional bits, then these additional
         bits may be included. However, if future versions of
         the OpenFlow protocol alter the meaning or order of
         existing bits then the information must be translated into
         a semantically equivalent 1.0 structure before exporting
         (possibly resulting in some loss of information).
         If major structural changes to the OpenFlow protocol
         invalidate the 1.0 structures, then the agent must not
         export the openflow_v1 structure. */

/* A bit array describing the fields in the packet header
   that are used to form the flow key. See ofp_match for
   the definition of wildcards. */

typedef unsigned int wildcards;

/* A bit array describing fields that may have been altered
   by the flow action. The ofp_action_type enum is used to
   determine the bit positions, with OFPAT_OUTPUT assigned
   to the least significant bit. The bit is set if an action



DRAFT                           sFlow.org                       [Page 2]

Version 0.1             sFlow OpenFlow Structures           January 2010


   of the corresponding type has been specified.
   Note: OFPAT_VENDOR is encoded using the most significant bit */

typedef unsigned int actions;

/* Extended OpenFlow 1.0 Data */
/* opaque = flow_data; enterprise = 0; format = 1017 */
struct extended_openflow_v1 {
  unsigned hyper flow_cookie;
  wildcards flow_match;
  actions flow_actions;
}

4. References

[1]  "OpenFlow Switch Specification, Version 1.0.0 (Wire Protocol
     0x01)", http://www.openflowswitch.org/documents/openflow-spec-
     v1.0.0.pdf, December 31, 2009


[2]  Phaal, P. and Lavine, M., "sFlow Version 5",
     http://www.sflow.org/sflow_version_5.txt, July 2006

5. Author's Address

   Peter Phaal
   InMon Corp.
   580 California Street, 5th Floor
   San Francisco, CA 94104

   Phone: (415) 283-3263
   EMail: peter.phaal@inmon.com

   Ben Pfaff
   Nicira, Inc.
   3600 W. Bayshore Road, Suite 205
   Palo Alto, CA 94303

   Phone: (650) 473-9777
   EMail: blp@nicira.com











DRAFT                           sFlow.org                       [Page 3]