[Bcause] interest and scope?

["Vigoureux, Martin (Nokia - FR/Paris-Saclay)" <[e-mail]>]

Hello,

as you might know, the RTGWG has hosted, for some time now, a set of 
documents that relate to the separation of the user plane and control 
plane of Broadband Network Gateways.
These documents can be found at 
https://datatracker.ietf.org/group/rtgwg/documents/ and start with 
draft-cuspdt-* or draft-wadhwa-*

Please read them if you haven't already.

Recently, a group of persons has worked together and produced few 
paragraphs in support of their willingness to see a working group on 
this topic formed.

Considering this, I am sharing this text with the IETF community in 
order to evaluate
* the wider interest in, and willingness to work on, this topic,
* the appropriateness of creating a focussed and short-lived working 
group (as opposed to continuing in rtgwg).
To that effect, please read and comment on the text further down, it is 
here for being debated.
As a matter of clarification: me sharing it, instead of the authors 
doing it, does not carry any special meaning.

Important note: this topic has its roots in BroadBand Forum (BBF) with 
which IETF has exchanged few liaisons on the topic recently. These are 
important reads:
https://datatracker.ietf.org/liaison/1619/
https://datatracker.ietf.org/liaison/1615/
https://datatracker.ietf.org/liaison/1600/
https://datatracker.ietf.org/liaison/1566/


---
Current Broadband Network Gateways (BNGs) that terminate residential 
broadband subscribers at the edge of service provider networks run as an 
integrated system where both the subscriber management control plane and 
traffic forwarding user plane are combined in a single system. In a 
large network, where the subscriber density is high, it is better to 
distribute and locate BNG systems closer to the subscribers, especially 
when the content caches are distributed to reduce backhaul costs and 
latency. In this scenario, as the BNG footprint grows, the subscriber 
management control points also proliferate, increasing operational 
complexity. This trend motivates the broadband network access industry 
to adopt new architectures that take advantage of the increasing ability 
to disaggregate and virtualize appropriate network access functions. 
Additional benefits can be realized by separating subscriber management 
control plane (CP) and traffic forwarding user plane (UP) for BNGs 
(referred to as Control and User Plane Separation (CUPS)). That 
simplifies operations, provides independent location, and scaling for CP 
and UP functions. A single CP function, running as a centralized VNF, 
can control and manage multiple UP instances, which may be distributed 
and separated from the CP via a multi-hop L2 or L3 network.  CUPS 
requires protocols for communication between CP and UP instances: from 
the CP to the UP to create and manage subscriber state instances and 
from the UP to the CP to handle relevant solicited or unsolicited events.

The proposed Working Group is a narrowly scoped WG tasked to specify 
communication protocol(s) between the CP and UP of a BNG, a network 
element whose functions are defined by BBF. A BNG can deliver broadband 
services to subscriber over wireline access or over multiple access 
types to accommodate different deployments. The goal of the WG is to 
define protocol(s) for CUPS that may support multiple deployment 
scenarios for the BNG.

The scope of the work covers protocol requirements, specification of the 
communications protocol, the information elements to be transferred with 
that protocol, and YANG data model(s) for Operations and Management as 
well as security, operational, and transport considerations.
---


Thank you
Martin