Reply to comment A on section 5.1.1 of draft-ietf-teas-yang-te-38

[italobusi]

5.1.1

It seems to me that the description of the route-object-include-exclude list is
complex. Are you sure you are not overloading the meaning? That is, the
interpretation of an empty list might be less convoluted if it was conveyed by
distinct objects.

There is also some confusion in my mind about the details.

A. The processing of the list is not clear to me. It doesn't seem to
model the objects in PCEP (Include Route in 5440, Exclude Route in
5521) nor the objects in RSVP-TE (Explicit Route in 3209, Exclude
Route in 4874).

I considered a simply topology...

A--B
\ |
|
C--D

Suppose the LSP is to be from A to D.
Suppose that the include-exclude list is {exclude C}
This, it would, seem would allow the path ABCD.
But if the include-exclude list was {include B, exclude C} then the
path must be ABD.

This, I think, means that the list is intended to describe the
formation of the path, not necessarily the "path computation" which
may use any algorithm.

It may be that a little more description is needed to clarify things.

• Prepare a reply text indicating that the interpretation is correct (assuming the route object are strict and not loose) and ask to provide some suggestion on how to improve the description

[italobusi]

• Reply that the interpretation is correct (assuming the route object are strict and not loose) and ask to provide some suggestion on how to improve the description

[italobusi]

I am wondering whether it is worthwhile clarifying that in case the route elements are loose:

• An include-exclude list {exclude C} is equivalent to {exclude-always C}
• In case of include-exclude list {include B, exclude C}, the ACBD path is also valid (C shall be excluded after B but not before B and the path from A to B is loose)

[tsaad-dev]

loose is not allowed in with exclude route as per rfc4874 section 3.1 "
The concept of loose or strict hops has no meaning in route
exclusion. "
To address in model (maybe when statement). Reference the RFC in the text.

[tsaad-dev]

The explicit-route-object is not allowed to be of hop type 'loose' when used in 'route-object-exclude-always' or when used in 'route-object-include-exclude' for an entry with the 'explicit-route-usage' is 'route-exclude-object'.