sFlow.org                                                 Chen Rozenbaum
https://sFlow.org/                                        Broadcom Corp.
info@sflow.org
                                                             Peter Phaal
                                                             InMon Corp.

                                                           December 2020


                     sFlow Transit Delay Structures



Copyright Notice

Copyright (C) sFlow.org (2020). All Rights Reserved.

Abstract

This memo describes an sFlow version 5 structure for exporting
information about packet transit delay.

Table of Contents

1. Overview ......................................................  1
2. sFlow Datagram Extension ......................................  1
3. References ....................................................  2
4. Author's Addresses ............................................  2

1. Overview

   This document describes additional structures that allow an sFlow
   agent to export information about transit delay that a sampled packet
   packet experiences as it traverses a switching device.  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 [1], it simply defines
   additional, optional, data structures that a network device can use
   to export packet transit delay information in sFlow.

2. sFlow Datagram Extension

   Transit delay is the time the sampled packet spent in the Network
   Device.  The extended_transit structure defined in this document can
   be added to a flow_sample [1] to report transit delay for the sampled
   packet.

   Queue depth is the number of bytes already in the selected output



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   queue when the sampled packet is enqueued.  For VOQ based
   architectures, queue depth is the number of bytes already in the
   selected VOQ when the sampled packet is enqueued. For chassis based
   systems, the value should be the sum of all VOQs directed to the
   output port. The extended_queue structure defined in this document
   can be added to a flow_sample to report queue depth encountered by
   the sampled packet.  An extended_egress_queue structure [2] must also
   be included to identify the selected output queue.

   The flow_sample input and output interface fields identify the path
   through the network device.

/* Delay for sampled packet traversing switch */
/* opaque = flow_data; enterprise = 0; format = 1039 */
struct extended_transit {
  unsigned int delay; /* transit delay in nanoseconds
                         0xffffffff indicates value >= 0xffffffff */
}

/* Queue depth for sampled packet traversing switch */
/* extended_egress_queue structure must be included */
/* opaque = flow_data; enterprise = 0; format = 1040 */
struct extended_queue {
  unsigned int depth;   /* queue depth in bytes */
}

3. References

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

[2]  Schimmel, A., Roulin, A. and Phaal, P., "sFlow Dropped Packet Noti-
     fication Structures", https://sflow.org/sflow_drops.txt, October
     2020

4. Author's Address

   Chen Rozenbaum
   Broadcom Corp.

   EMail: chen.rozenbaum@broadcom.com

   Peter Phaal
   InMon Corp.

   EMail: peter.phaal@inmon.com





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