Comments on "draft-duffield-framework-papame-00"

["Sonia Panchen" <sonia_panchen@inmon.com>]

As I understand it "A Framework for Passive Packet Measurement" is a
starting point for network equipment vendors, software developers, and xSPs
to agree on a a set of capabilities that would be useful for providing the
network traffic monitoring and analysis required for operational network
management tasks.

As such it describes a number of interesting goals, philosophies,
specifically:

Provision of reliable, detailed, timely traffic measurements
Promotion of widespread embedded traffic measurement mechanisms by defining
simple and cost effective monitoring techniques.
Pervasive measurement technology with consistent and well defined interfaces
will encourage development of a broad spectrum of applications that make use
of this data.

As a network traffic monitoring and analysis software vendor, InMon Corp. is
very interested in promoting standard measurement functionality in switching
ASICs so that network hardware is capable of providing basic information in
a consistent format. Some of the techniques mentioned are consistent with a
technology (sFlow RFC 3176) that we have developed and successfully deployed
in large scale enterprise and xSP environments, specifically:

Selection of packets for measurement: random 1 in N count-based sampling
Measurement export mechanism: unreliable, stateless - each exported packet
is self contained
Content and format of exported data: eg Data export packet specification
which includes packet header, router state parameters, and sampling process
information for scaling.

For the applications that we have been interested in (operational control:
congestion contol, troubleshooting, security threat characterization,
accounting for capacity planning and billing etc., routing policy
optimization) we have not found a need for filtering and hashing for packet
selection and so cannot comment on these techniques. We have also found
that, for our applications, with a measurement and analysis system design
based on 1 in N random sampling with immediate forwarding of the data, an
unreliable data export mechanism is ideal. Such a system has many benefits.
For example it provides detailed, reliable, and timely information, is cost
effective for embedded implementation, and has low network overhead.

It seems that PSAMP could make a significant contribution by building
concensus on basic mechanisms that should be incorporated in ASICs (eg
sampling, filtering and hashing algorithms) and how they are specified and
parameterised.

The filtering, sampling and hashing functions are somewhat orthogonal to the
data export functions. You could export sampled, filtered, and hashed data
using any of the existing flow export protocols (e.g. IPFIX, NetFlow, LFAP,
RTFM, sFlow etc). There are many applications for sampled data and the
variety of export protocols reflects these different objectives.

Sonia Panchen
InMon Corp
sonia_panchen@inmon.com




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