Subject: [ippm] some questions on draft-ietf-ippm-ioam-data-04

From: Tianran Zhou <[email-masked]>
Date: Tue, 4 Dec 2018 02:03:04 +0000

Hi Authors,

I am reading this draft and feel some queue related description is not clear to me.

1. queue depth:  4-octet unsigned integer field.  This field indicates
      the current length of the egress interface queue of the interface
      from where the packet is forwarded out.  The queue depth is
      expressed as the current number of memory buffers used by the
      queue (a packet may consume one or more memory buffers, depending
      on its size).

The size of memory buffer varies from different chips. Typical chips use 512 bytes for one memory buffer, but some other chip use 256, or so.
So for one packet, it may consume different number of memory buffers in different devices. I am afraid this will impact the analytics application, since it do not know what this number really means for the congestion/queue utilization.

To some extent, do you think the total queue length/occupancy ratio worth recording? So that the analytics application know the occupation rate. But this is also hard, because many chips use shared buffer, that means each queue does not have a fixed length.

2. buffer occupancy:  4-octet unsigned integer field.  This field
      indicates the current status of the buffer occupancy.  The buffer
      occupancy is expressed as the current number of memory buffers
      used by the set of queues that share a common buffer pool.

Could you explain how to use this data? What's the use case that make this data field valuable?

Thanks,
Tianran