Re: [AVT] Comments on draft-ietf-avt-rtcp-xr-mib-00.txt

[Magnus Westerlund <magnus.westerlund at ericsson.com>]

Hi Dan,

I have a comment on the below.

Romascanu, Dan (Dan) wrote:
> 3. At the last IETF meeting we discussed about the relationship between 
> RTCP XR MIB and RAQMON, and decided to include a 'Relationship to 
> RAQMON' section, which is now only a place-holder. I suggested to the 
> editors the following text:
>
> */'The Real-time Application QoS monitoring (RAQMON) Framework 
> [RAQMON-FRAMEWORK - provide reference here to_ 
> <http://www.ietf.org/internet-drafts/draft-ietf-rmonmib-raqmon-framework-07.txt>_] 
> defines an architecture that extends the Remote Monitoring (RMON) family 
> of applications for monitoring of application QoS in real-time, and an 
> extensible data model with objects carried between RAQMON data sources 
> and RAQMON collectors. The RAQMON work is more generic, and 
> complementary in concept to RTCP-XR, covering a wider range of 
> applications running concurrently, while RTCP-XR focuses on QoS 
> monitoring of media traffic in VoIP./*//

Although one of the RTCP XR types has received substantially more 
interest, the RTCP XR is not limited to VoIP. It is a general framework 
which is currently populated with the following different reporting blocks:
       4.1.  Loss RLE Report Block. . . . . . . . . . . . . . . . . .  9
       4.2.  Duplicate RLE Report Block . . . . . . . . . . . . . . . 16
       4.3.  Packet Receipt Times Report Block. . . . . . . . . . . . 18
       4.4.  Receiver Reference Time Report Block . . . . . . . . . . 20
       4.5.  DLRR Report Block. . . . . . . . . . . . . . . . . . . . 21
       4.6.  Statistics Summary Report Block. . . . . . . . . . . . . 22
       4.7.  VoIP Metrics Report Block. . . . . . . . . . . . . . . . 25

Thus, I can also provide some more comments of the document:

MW1: The XR MIB needs to be defined in such a way that it can easily be 
extended if more report types are created.

MW2: THE XR MIB should define structures for all the currently defined 
XR report blocks.

MW3: The security consideration section also seems to be a bit strange, 
is it mostly copy and pasted from the RTP MIB?

MW4: rtcpXrVoipSessionIdentifier OBJECT-TYPE
    SYNTAX OCTET STRING
    STATUS optional
    DESCRIPTION
        "Unique identifier for this session.  Where a billing record
         correlation identifer is not available for a particular call,
         another identifier such as SSRC can be used."
    ::= { rtcpXrVoipEntry 3 }

How can the SSRC be a session identifier?

MW5: How is sessions with more than a single destination handled?

MW6: rtcpXrVoipVocoderType OBJECT-TYPE
    SYNTAX OCTET STRING
    STATUS current
    DESCRIPTION
        "Vocoder type used on this call."
    ::= { rtcpXrVoipEntry 10 }

rtcpXrVoipFrameSize OBJECT-TYPE
    SYNTAX INTEGER
    STATUS current
    DESCRIPTION
        "Companion information to vocoder type.  This represents the
         size of the frames within the RTP packets at the time the
         information is capture."
    ::= { rtcpXrVoipEntry 11 }

First, is multiple instances allowed? A session may consist of multiple 
media codecs and/or configurations of a codec. Also how is the vocoder 
type expressed. What is the string? The RTP payload MIME type with its 
parameters? Maybe one should consider to make this definition a bit more 
generic to fit any media encoding format? Thus it can potentially be 
re-used?

MW7: rtcpXrVoipSampleRate OBJECT-TYPE
    SYNTAX OCTET STRING
    STATUS current
    DESCRIPTION
        "Companion information to vocoder type.  This represents the
         rate at which the frames where sampled.
    ::= { rtcpXrVoipEntry 12 }

Which rate are you talking about here? The audio sample rate, or the 
rate with which frames are produced?

MW8: All references can not be normative, a lot of these must be 
informative ones.

MW9: Run a spellchecker over the description texts.

Cheers

Magnus Westerlund

Multimedia Technologies, Ericsson Research EAB/TVA/A
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