Subject: [Raw] Some comments/questions on RAW Architecture

From: Lou Berger <[email-masked]>
Date: Sun, 20 Mar 2022 21:25:28 -0400

Pascal, Georgios,

In looking to provide input on the framework document I realized I had 
some basic questions on the architecture document. While I also have 
more detailed comments/questions on the Architecture document, I'll 
stick to the high level comments/questions here. Also, my apologies for 
not getting them out sooner, but I figured it was still better to 
document here than just "at the mic" in tomorrow's session.

1) What does the term "RAW" refer to in the context of the architecture? 
Is it a new/standalone set of mechanisms or is it an addition or an 
extension, or a usage of IETF defined technologies?

I find that reading the architecture, I'm really  unsure.  The current 
working is a bit mixed, e.g.,

    Reliable and Available Wireless (RAW) provides for high reliability
    and availability for IP connectivity over a wireless medium.

this sounds like something new/independent

    It builds on the DetNet Architecture and
    discusses specific challenges and technology considerations needed to
    deliver DetNet service utilizing scheduled wireless segments and
    other media, e.g., frequency/time-sharing physical media resources
    with stochastic traffic.

this sounds evolutionary.

I was expecting the RAW WG to build on DetNet and other IETF Traffic 
Engineering (TE)  bodies of work. In other works something along the 
lines of:

     The RAW Architecture builds on the DetNet Architecture and
     standard IETF Traffic Engineering concepts and mechanisms to
    deliver service across any combination of wired and wireless
    network segments. ...

I think the document and the used terminology must be clear even we're 
(understandably) loose in the usage of the "RAW" term in our discussions.

2) Are RAW solutions limited to IPv6 and a limited set of wireless 
technologies?  I think the framework says/implies no, but the 
architecture is less inclusive. e.g.,
    RAW provides DetNet elements that are specialized for IPv6 flows
    [IPv6] over selected deterministic radios technologies [RAW-TECHNOS].

I would expect that at least at the Architecture level that there would 
be no exclusion of IETF networking technologies (including v4 and MPLS) 
and any SDO-defined wireless technology.  I certainly understand needing 
to focus and prioritize work on specific technologies, but that is 
practical choice not a limitation that should be codified in the 
architecture.

Somewhat related, but of less importance, it's probably worth mentioning 
that RAW forwards/switches at the IP, not link layer.

3) How do tracks differ from TE protection paths?

In reading the definition of the tracks, the term seems quite 
aligned/similar to TE protection paths and segments.  Keep in mind that 
DetNet PREOF is just one form of service restoration supported in IETF 
TE, i.e., the 1+1 form.  A track reads to me to be something that can be 
composed or combine 1:1, 1:N and even 1+N, and have interesting 
(uncoordinated) protection switching based on actual network/link 
(channel) state.  I suspect we can accomplish the same objectives as 
Tracks and stay consistent with existing DetNet and TE(AS) terminology.

4) Is RAW limited to PCE-based centralized solutions?

DetNet introduced the term Controller Plane to cover all types of 
control supported by the IETF TE architecture, i.e., fully centralized, 
fully distributed, or any hybrid combination of centralized/distributed 
control.  The Architecture reads as supporting only one combination of - 
PCE for paths, PSEs for tracks (aka protection segments) .   PSEs read 
as also doing the actual protection switching, but this is outside the 
scope of this comment.

Hereto, I see no reason for the architecture to limit the scope of the 
Controller Plan solutions that could be standardized as part of RAW.  
(Yes PCE-based approaches are likely the first to be standardized, but 
that's not an architecture level decision.)

Those are my top comments.  While substantive, I suspect addressing 
these comments will result in some refactoring and rewording -- but not 
a major change to the document.

Thank you, and speak to you soon. (Unfortunately, just virtually this 
meeting...)

Lou