Subject: [Gen-art] Re: LC Review Assignment: RAQMON

From: "Joel M. Halpern" <[email-masked]>
Date: Sat, 04 Feb 2006 19:56:19 -0500

I was selected as General Area Review Team reviewer for this specification
(for background on Gen-ART, please see
http://www.alvestrand.no/ietf/gen/art/gen-art-FAQ.html).

Framework:
http://www.ietf.org/internet-drafts/draft-ietf-rmonmib-raqmon-framework-14.txt
This document is nearly ready for publication as a proposed standard.
(If I am confused about the congestion section, then it is ready for 
publication.)

Moderate:  Congestion...
Has the congestion safety section been reviewed by a transport area 
congestion expert?
It seems to me that the description in section 3, bullet 1, of the 
use of a constant Transmission rate ought to indicate that the rate 
needs to be related to the expected peak number of devices.  (After 
all, the earlier text did talk about the fan in problem.)  Based on 
routing protocol experience, it may also want to indicate that the 
timer for the constant rate needs to be randomly jittered.
The title of section 3, bullet 2 (retransmission timers with back 
offs) seems misleading.  If I am reading the text right, the actual 
technique is to send one message, and wait for a response before 
sending another.  What one might call "single outstanding 
request."  There is nothing in the text about retransmissions and 
back-offs.  (Although, such a technique does require retransmissions, 
and such retransmissions must be backed off.  That is secondary to 
the core of the technique, but ought to be mentioned.)
Section 3, bullet 3 is about avoiding fragmentation.  While that is a 
useful technique, it does not seem to me that it is a congestion 
avoidance technique.

Minor: In section 2.1.3, in describing how configuration parameters 
can be accessed, it lists several ideas as if they were implementable 
approaches.  If we are going to call out DHCP usage, don't we need to 
identify the DHCP option and structure to use?  If we are going to 
suggest using DNS, don't we need to indicate how such configuration 
information would appear in DNS?  For LDAP, we would need a schema...
     Having said that, I believe that the right answer is to reword 
this list to indicate that Manual config is the only defined method, 
a state that the remaining items are ideas for future exploration. 
(Unless you have a file format, a schema, a DHCP option, and a DNS 
record structure up your sleeves already.)
     And shouldn't the list include the MIB, which has the right properties?

Minor: DA, section 5.1.  One line says that this parameter MUST be 
sent in all RAQMON PDUs.  The next lines say that since it will 
remain constant, RDSs should avoid sending this information too 
often.  Which is it?  Should it be in every report, or should it be 
sent in only some reports, in order to confirm that the state hasn't 
changed?  (The same oddity occurs with the RA.)

Minor: Some of the "fraction" reporting items in section 5 state that 
they are reported as a fixed point value with the binary point at the 
left edge of the field (5.21).  Most of the items do not state the 
representation.  I can understand deferring the representation to the 
protocol / MIB.  I can understand including it here.  But we ought to 
be consistent. Given that the MIB uses "percent", and the PDU 
document gives explicit encoding, probably this document should have 
no format definition.

Nit: The receiver of the report is not a source. Why does 5.2 insist 
on calling it the "Receiver Source"?

Nit: In section 2.1.3, when describing ways of getting configuration, 
the LDAP client method appears to be part of the DNS method, rather 
than a separate method of its own.

PDU
http://www.ietf.org/internet-drafts/draft-ietf-rmonmib-raqmon-pdu-12.txt
This document is ready for publication as a Proposed Standard.
The few minor items should be considered if there is a need to revise 
the document.

Minor: In describing the T bits, it says "A value of zero is 
considered to be valid..."  If I am reading this right, a value of 0 
would be common, since many times there is no application specific 
information to add to the basic information.  If it was intended that 
this count include the basic application information, then "that 
trail the BASIC Part" would need to become "including the BASIC 
part."  (And if it does not include the basic part, can we change 
"trail" to "follow"?)

Minor: The Packet Discard in Fraction field occurs in the packet 
before the Packet Loss in Fraction field.  But discard is bit 31 and 
loss is bit 30 in the bits.  And the field descriptions after the bit 
table are in yet a different order.  Is there a need for this variation?

Minor: The WG probably considered it obvious, but I think there ought 
to be a short section that says roughly ~to use TCP to transport 
RAQMON PDUs, it is sufficient to send the PDUs as the TCP data.  As 
each PDU carries its length, the receiver can determine the PDU boundaries."

Nit: "...both functional parts trail a field carrying ..."  I am sure 
that there is a better word than "trail".  Contain?

MIB
http://www.ietf.org/internet-drafts/draft-ietf-rmonmib-raqmon-mib-11.txt
This document is ready for publication as a Proposed Standard

Minor: The framework makes a point of distinguishing between 
discarded packets and lost packets.  The raqmonQos table does not 
make such a distinction.  Is there a reason for this?  Probably this 
would be dealt with by an extra sentence or two in section 4 
indicating the rationale for the particular selection of fields in the table.

Nit:  Was there no way to squeeze "priority" / "DSCP" (or at least 
"pri") in the names of the raqmonParticipantSrcLayer2 (DestLayer2, 
SrcLayer3, and DestLayer3) fields?  The bits definition and the 
description clause makes it clear what these are.  But the naming 
threw me for a bit.

At 05:26 PM 2/1/2006, Mary Barnes wrote:
>---------------------------
>Reviewer: Joel Halpern
>
>- 'Real-time Application Quality of Service Monitoring (RAQMON) MIB '
>    <draft-ietf-rmonmib-raqmon-mib-11.txt> as a Proposed Standard
>- 'Real-time Application Quality of Service Monitoring (RAQMON)
>Framework '
>    <draft-ietf-rmonmib-raqmon-framework-14.txt> as a Proposed Standard
>- 'Transport Mappings for Real-time Application Quality of Service
>Monitoring
>    (RAQMON) Protocol Data Unit (PDU) '
>    <draft-ietf-rmonmib-raqmon-pdu-12.txt> as a Proposed Standard
>
>    There is a potential overlap between the RAQMON protocol and
>    the IPFIX and/or RTCP-XR work, but there are enough differences
>    in applicability and complexity that this should not be
>    a significant issue.  RAQMON is an extensible, distributed,
>    SNMP-based monitoring system, integrated with the RMON
>    family of MIB modules.  As such, it is intended to be applicable
>    to many different types of protocols, that may run concurrently.
>    If a specialized protocol for VoIP monitoring is desired, then
>    RTCP-XR should probably be used instead.  If SNMP and/or
>    RMON integration are not desired, then IPFIX would be a
>    suitable choice.
>
>IETF LC ends on 2006-02-13.
>
>The files can be obtained via
>http://www.ietf.org/internet-drafts/draft-ietf-rmonmib-raqmon-mib-11.txt
>http://www.ietf.org/internet-drafts/draft-ietf-rmonmib-raqmon-framework-14.txt
>http://www.ietf.org/internet-drafts/draft-ietf-rmonmib-raqmon-pdu-12.txt

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