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Liaison statement
Follow-on response to IETF liaison: ‘Potential RTGWG work related to the disaggregated BNG architecture’

Additional information about IETF liaison relationships is available on the IETF webpage and the Internet Architecture Board liaison webpage.
State Posted
Submitted Date 2019-03-07
From Contact Lincoln Lavoie
To Groups RTG, rtgwg
To Contacts Chris Bowers <>
Jeff Tantsura <>
Alvaro Retana <>
Deborah Brungard <>
Martin Vigoureux <>
Cc Deborah Brungard <>
Chris Bowers <>
Martin Vigoureux <>
Alvaro Retana <>
The IETF Chair <>
Routing Area Working Group Discussion List <>
Dave Sinicrope <>
Jeff Tantsura <>
Liaisons at Broadband Forum <>
Statements at IETF <>
Robin Mersh <>
April Nowicki <>
David Allan<>
George Dobrowski<>
Chris Croot <>
David Sinicrope <>
Purpose In response
Attachments LIAISE-281_v1
Liaisons referred by this one Response to IETF liaison: ‘Potential RTGWG work related to the disaggregated BNG architecture’
Potential RTGWG work related to the disaggregated BNG architecture
Liaisons referring to this one Response to IETF liaison: ‘Potential RTGWG work related to the disaggregated BNG architecture’
Follow-on to IETF liaison: ‘Potential RTGWG work related to the disaggregated BNG architecture’
IESG follow-up regarding 'Potential RTGWG work related to the disaggregated BNG architecture'
Dear colleagues,

In our initial response on December 17, 2018 to your 3 December 2018 liaison
‘Potential RTGWG work related to the disaggregated BNG architecture’ we
informed you that we intended to complete the review of the drafts and
communicate any comments to you by mid-February 2019. This response is the
result of the review of the following architecture drafts: •      

From our review of the architecture drafts, we believe the following points
would be relevant to further work by the IETF on the drafts: •       In the
scope of a protocol to address the separation of the control and user plane for
a multi-service BNG we would like to:

o       inform you that the primary nodal requirements for a multi-service BNG
is defined in BBF TR-178 and the known examples are described in TR-384 for the
disaggregated BNG functions. In addition to these requirements, the BNG can be
used in various multi-access deployments with additional capabilities,
including integration into the BNG. These additional capabilities with examples
of deployment options are specified in TR-348, TR-378, TR-291, TR-300, TR-321.

o       inform you of the deployment scenarios based on BBF's "V" reference
point encapsulation and relevant protocols (e.g., MPLS PW, L2oGRE, L2TPv3)
specified in the supporting Broadband Forum Technical Reports (e.g., TR-101,
TR-178 for Ethernet VLAN, MPLS PW).

o       note that the architecture drafts that reference TR-384 (section 5.2.5)
only addresses 1 of the 2 exemplary disaggregation options. Minimally both
options within TR-384 for disaggregation of a BNG should be addressed by the

o       inform you that the BBF has started work on control and user plane
separation for a disaggregated BNG that may include additional capabilities
addressing various deployment scenarios. (WT-459).

•       We also have noted several items that to consider in order to improve
the clarity of the work toward the audiences of the draft:

o       We would encourage the use of consistent terminology among drafts in
order to avoid confusion.

o       To help with alignment between the IETF / BBF, it would be helpful for
the IETF to clarify what the CUPS function and protocol is addressing (problem
or issue), or beneficially providing so that so we can better understand and
map the functionality to the different BBF BNG specifications. Without that
clarity it makes it difficult to determine the inter-dependencies and impacts
between the established BBF BNG specifications and any new function. For
example. if CUPS were to become a functional requirement in a BBF
specification, the specification would need to understand what problem the CUPS
function is addressing.

•       The Security Considerations sections in the drafts are inadequate and
should be improved to discuss the security of communications between the CP and

In addition, in our last response we noted that we were discussing our current
work Wireline and Wireless Convergence (WWC) as it relates to the need for
protocol requirements and specification for the separation of the control and
user plane for disaggregated BNGs for fixed network subscribers. Recently, as
part of our 5G Fixed Mobile Convergence (FMC) stream, we started a new working
text WT-458 on “CUPS for 5G FMC functions”. This working text does not include
CUPS for BNG. However, this is a work of interest, as one of the 5G convergence
models redistributes existing BNG functions across the 5G core network and an
Access Gateway Function (AGF). AGF is going through normative work at BBF and
WT-458 will specify how the AGF control and user planes can be separated. The
target completion date for WT-458 is Q3 2019. As highlighted in our previous
liaison, our preferred direction is to leverage 3GPP’s PFCP protocol for CUPS
on AGF. The feasibility of this is being verified as part of WT-458. Assuming a
positive result and subject to 3GPP agreement, extensions needed to PFCP for
AGF support will be done by BBF in direct consultation and cooperation with
3GPP.   We would be happy to keep RTGWG informed of our work status as it
progresses. As stated in our last liaison response we continue to welcome
further coordination as the work of both organizations progresses on this topic.


Lincoln Lavoie,
Broadband Forum Technical Committee Chair

Liaisons at Broadband Forum <>
Statements at IETF <>
Robin Mersh, Broadband Forum CEO  <>
April Nowicki, Broadband Forum Member Support Manager
<> David Allan, Broadband Forum WWC Work Area
Director <> George Dobrowski, Broadband Forum SDN/NFV
Work Area Director, <> Chris Croot, Broadband
Forum SDN/NFV Work Area Director, <> David Sinicrope, IETF
Liaison Manager to BBF <>

Broadband Forum Reference:

In Response to Incoming Liaison:
LIAISE-262; IETF ref:

Date of Upcoming Broadband Forum Meetings
A list of upcoming meetings can be found at