Subject: Opsdir early review of draft-ietf-i2rs-rib-info-model-12

From: Mahesh Jethanandani <[email-masked]>
Date: Fri, 12 Jan 2018 07:30:55 -0800

Reviewer: Mahesh Jethanandani
Review result: Not Ready

I have reviewed this document as part of the Operational directorate’s ongoing
effort to review all IETF documents being processed by the IESG.
 These comments were written with the intent of improving the
operational aspects of the IETF drafts. Comments that are not addressed in last
call may be included in AD reviews during the IESG review.  Document editors
and WG chairs should treat these comments just like any other last
call comments.

Document reviewed:  draft-ietf-i2rs-rib-info-model-12

Summary:
This draft specifies a information model for the RIB to enable defining a
standardized data model.  Such a data model can be used to define an interface
to the RIB from an entity that may even be external to the network device. 
This interface can be used to support new use-cases being defined by the IETF
I2RS WG.

Document Status:
Not ready

Comments:

This document is a information model, and as such does not define a data model
that is directly used by a protocol. Therefore it has no operational or
management impact.

Having tried to read the document, I believe a lot can be done to improve its
readability. At times it appears that different people took a crack at
different sections of the document, without agreeing on the overall structure
of the document.

There is also something funny about how the section numbers have been given and
the diagrams placed within them.

Section 2.

Figure 2 shows the RIB model. By putting it where it is, I would have expected
that all the elements of the diagram would be explained in that section. One
has to read section 2.1 and 2.2 to figure the details.

Even then it is difficult to comprehend by reading all sections what the
diagram is trying to convey. First of all, it appears that there can be
multiple routing instances, but the diagram refers to one routing instance. If
the idea is to refer to one routing instance in the RIB model, then as the name
suggests, it is not the RIB model, but one routing instance of the RIB model.
Either change the name or show the diagram with multiple instances.

Also if each RIB consists of 0..N routes, that is not clear from the diagram.
It appears that each routing-instance has 1..N RIBs and 0..N routes with no
relationship to each other.

Section 2.3

Similarly for Figure 3, the diagram is in section 2.3, but if one has to
understand the diagram, one has to read section 2.4 to understand the diagram.

Figure 3 shows the route model. It specifies 6 match conditions, but shows only
5 in the diagram. What happened to IP multicast match?

Section 2.4

Figure 4 is titled Nexthop model. There is no explanation of the figure in
Section 2.4 and what the different pieces of the diagram mean. Instead, it
talks about how nexthop points to a BGP peer, a reference which is not clear by
looking at the diagram.

I would have expected at least an explanation of the rest of the diagram. The
next section gets into Nexthop types, with no apparent ties to the diagram.

Section 3 and 4.

There is a lot of common text between the two sections. I do not know if there
is a way to combine it.

There is no word like modify-able or even modifiable. s/are modify-able
objects/can be modified/

Section 6. RIB grammar

The section says the grammar is intended to help the reader better understand
the english text description. But it then goes on to say that if there is lack
of clarify in the grammar the english text will take precedence. So what gives
- english text or grammar?

Also where is the english text?

At this point I stopped and could not comprehend the rest of the document or
its organization.

---

From: Nitin Bahadur <[email-masked]>
Date: Sun, 14 Jan 2018 17:20:42 -0800

Hi Mahesh,

  Thanks for taking an initial stab at it. I’ll work on adding these clarifications and rev the draft. Improving readability is definitely important!

On 1/12/18, 7:30 AM, "i2rs on behalf of Mahesh Jethanandani" <[email-masked] on behalf of [email-masked]> wrote:

    
    
    Summary:
    
    Document Status:
    Not ready
    
    Comments:

    
    
    Section 2.

    
    
    Section 2.3

    
    Section 2.4

    
    Section 3 and 4.

    
    Section 6. RIB grammar

    
    
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