[netconf] Issues with draft-ietf-netconf-udp-notif-04

[Andy Bierman <[e-mail]>]

Hi,

I am wondering if there implementations of this draft already.
IMO there are problems with in that prevent reasonable and
optimal implementations.

1) Use of UDP as the Application Message Framing
UDP is a transport protocol.  Tightly coupling one
NETCONF notification message to one UDP frame (+ fragments)
is not very optimal.

1A) wastes space in the UDP frame if the NETCONF notification
    happens to be short
1B) imposes an application-level max-message-size

2) Not Efficient for Streaming Servers (no Message Chunking)
The application framing in NETCONF and RESTCONF (HTTP) is not
coupled to any transport protocol. Instead, a sender may emit as
many message chunks as desired. This is how a streaming server works.
Content comes from many different sources and it is sent on-the-fly
in chunks, instead of constructing large replies.

    - Application framing allows multiple notifications in one UDP frame
    - Application framing does not need a max-message-size.
      Streaming servers often do not know the size of the data that will be
sent
      in a notification.

Q1) Should proprietary encoding be used to support application-layer framing
       or should the standard support it?

3) Protocol Message Encoding for CBOR
The NETCONF notification message is not modelled in YANG.
This is an open issue for YANG to CBOR encoding.
https://github.com/core-wg/yang-cbor/issues/96

The "notification" and "eventTime" elements do not have YANG definitions.
SID assignments for these elements will be needed.
This draft is the likely place for these SID assignment requests to
the IESG and IANA.

4) Subscription-ID Missing from Header
It is quite possible for one message generator to create
messages for multiple subscriptions.  The subscription-ID
will be needed to dispatch notifications to subscribers correctly.
The Observation-Domain-ID is not sufficient.

5) Private Encoding Option does not seem interoperable
The "Enc. Descr" field is completely opaque.
This field could be structured to provide the "ET number space owner"
e.g, urn [wsp description]


Andy