Subject: [IPFIX] WGLC: draft-ietf-bmwg-ipflow-meth-00

From: Al Morton <[email-masked]>
Date: Sun, 13 Feb 2011 10:06:54 -0500

BMWG,
CC: IPFIX WG,

This message begins the first WG Last call on the draft:

IP Flow Information Accounting and Export Benchmarking Methodology
draft-ietf-bmwg-ipflow-meth-00.txt

A URL for this draft is:
http://tools.ietf.org/html/draft-ietf-bmwg-ipflow-meth-00

The Last Call will end on March 14, 2011.

Although this is the first WGLC, we have discussed this draft
in the working group for over two years, and made many suggestions.
We have also benefited from review by folks from IPFIX WG.
I now ask folks to consider items where they commented earlier,
and make sure that the resolutions are satisfactory.

And it's not too late to read the draft for the first time,
and provide comments based on your review.

Please weigh-in on whether or not this Internet-Draft
should be given to the Area Directors and IESG for consideration and
publication as an Informational RFC.  Send your comments
to this list and/or [email-masked].

Al
bmwg chair

---

From: Peter Phaal <[email-masked]>
Date: Sun, 13 Feb 2011 14:04:22 -0800

Hi all,

I would like to comment on the references to sFlow in the IP Flow Information Accounting and Export Benchmarking Methodology document.

The Abstract states, "The metric is only applicable to the devices compliant with the Architecture for IP Flow Information Export [RFC5470]." The sFlow architecture differs significantly from RFC5470 and the benchmarking methodology described in the document is not applicable sFlow.

Confusion can arise because the sFlow specification (http://www.sflow.org/sflow_version_5.txt) does use the term Packet Flow. However, sFlow's definition of a packet flow is:

o Packet Flow: A Packet Flow is defined as the path or trajectory
     that a packet takes through a Network Device (i.e. the path that a
     packet takes as it is received on one interface, is subject to a
     switching/routing decision and is then sent on another interface.

Note that the definition refers to a single packet. The sFlow architecture is stateless, an sFlow agent does not examine packet attributes or aggregate data in a flow cache. Sampled packet headers are immediately exported to a central sFlow collector which decodes, classifies, scales and aggregates the data.

o Packet Flow Record: A Packet Flow Record describes the attributes
     of a Packet Flow. There are two types of information in a flow
     record:

      1   Information on the packet itself, typically a packet header,
          packet length and packet encapsulation.

      2   Information about the path the packet took through the device,
          including information relating to the selection of the
          forwarding path.

The second measurement technique used by sFlow, Counter Sampling, also differs significantly from RFC5470:

o Counter Sampling: Periodic sampling or polling of counters
     associated with a Data Source.  

The following example demonstrates the general lack of applicability of this document to sFlow benchmarking. Paragraph 5, in the Introduction states:

   The most significant parameter in terms of performance, is the rate
    at which IP flows are created and expired in the network devices
    memory and exported to a collector. 

Since sFlow agents are stateless, the rate of IP flows is not a factor that influences performance.

To avoid confusion, the following references to sFlow should be removed from the benchmark document:

1. Figure 1, page 7. sFlow does not export flows and is not part of the flow monitoring plane.
2. Page 30, sFlow should be removed from the Flow Export Protocol list since it does not export flow records.

Cheers,
Peter
 
On Feb 13, 2011, at 7:06 AM, Al Morton wrote:

> _______________________________________________
> IPFIX mailing list
> [email-masked]
> https://www.ietf.org/mailman/listinfo/ipfix

---

From: "Jan Novak (janovak)" <[email-masked]>
Date: Mon, 14 Feb 2011 16:50:18 +0100

Hi,

Thank you - quite valuable point.

Jan

The climate of Edinburgh is such that the weak succumb young .... 
and the strong envy them.
                                 Dr. Johnson

-----Original Message-----
From: [email-masked] [mailto:[email-masked]] On Behalf Of
Peter Phaal
Sent: 13 February 2011 22:04
To: Al Morton
Cc: [email-masked]; [email-masked]
Subject: Re: [bmwg] [IPFIX] WGLC: draft-ietf-bmwg-ipflow-meth-00

Hi all,

I would like to comment on the references to sFlow in the IP Flow
Information Accounting and Export Benchmarking Methodology document.

The Abstract states, "The metric is only applicable to the devices
compliant with the Architecture for IP Flow Information Export
[RFC5470]." The sFlow architecture differs significantly from RFC5470
and the benchmarking methodology described in the document is not
applicable sFlow.

Confusion can arise because the sFlow specification
(http://www.sflow.org/sflow_version_5.txt) does use the term Packet
Flow. However, sFlow's definition of a packet flow is:

Note that the definition refers to a single packet. The sFlow
architecture is stateless, an sFlow agent does not examine packet
attributes or aggregate data in a flow cache. Sampled packet headers are
immediately exported to a central sFlow collector which decodes,
classifies, scales and aggregates the data.

The second measurement technique used by sFlow, Counter Sampling, also
differs significantly from RFC5470:

The following example demonstrates the general lack of applicability of
this document to sFlow benchmarking. Paragraph 5, in the Introduction
states:

Since sFlow agents are stateless, the rate of IP flows is not a factor
that influences performance.

To avoid confusion, the following references to sFlow should be removed
from the benchmark document:

1. Figure 1, page 7. sFlow does not export flows and is not part of the
flow monitoring plane.
2. Page 30, sFlow should be removed from the Flow Export Protocol list
since it does not export flow records.

Cheers,
Peter

_______________________________________________
bmwg mailing list
[email-masked]
https://www.ietf.org/mailman/listinfo/bmwg