Re: [Bier] proposed BIER charter

[<[e-mail]>]

Alia,

I have been engaged with BIER technology for the last year and a half from its inception. It come along way and it was not driven just based on excitement. This work is backed up by commitment from major vendors and multiple operators. I have discussed BIER on multiple occasions with other operators, they showed a great interest and strong support with overall consensus that BIER will build a right foundation for efficient multicast delivery for operators to standardize. I promoted BIER within Thomson Reuters on the Business and Technology sides and feedback was overwhelming, with huge interest from Thomson Reuters development community. Based on my involvement with BIER, I struggle to define it as Experimental as per included definition below and I completely agree with Stewart on his assessment of your proposed charter. Please don't take it as a criticism, I am very novice in terms of IETF protocols and procedures but as per my findings of IETF definitions:

"WG charters state the scope of work for group, and lay out goals and milestones that show how this work will be completed."

The proposed version in the way it was written more focusing on conditional statements and depicts some unwillingness of IETF to promote/proceed with BIER as a committed work.



Snapshot from IETF.org

“4.2.1 Experimental

The "Experimental" designation typically denotes a specification that is part of some research or development effort. Such a specification is published for the general information of the Internet technical community and as an archival record of the work, subject only to editorial considerations and to verification that there has been adequate coordination with the standards process (see below). An Experimental specification may be the output of an organized Internet research effort (e.g., a Research Group of the IRTF), an IETF Working Group, or it may be an individual contribution.”



I would like to continue to promote BIER and take an active part in developing of new multicast technologies for my company and industry benefits. There are plenty of challenges in this arena, but only via active participation these challenges can be resolved. We need to see commitment from IETF to move BIER development forward.



Regards,

Arkadiy


From: BIER [mailto:[e-mail]] On Behalf Of Alia Atlas
Sent: Thursday, February 12, 2015 10:14 AM
To: stbryant
Cc: Adrian Farrel; [e-mail]; [e-mail]; Alvaro Retana
Subject: Re: [Bier] proposed BIER charter

Stewart,

I certainly appreciate your taking the time to provide feedback.  I understand that you
are excited by this technology and have urged that innovation needs time and space
to be worked on before being evaluated by the harsh realities of the marketplace and
interest in deployments.

On Thu, Feb 12, 2015 at 8:44 AM, Stewart Bryant <[e-mail]<mailto:[e-mail]>> wrote:
Alia

I think that you are crossing far too many bridges before you get to them
in terms of you expectation of where BIER will be deployed and how
it will be implemented.

I did read the use-cases and understand the primary motivation is for MVPN
and EVPN which are deployed in the backbone of SP networks that operate at
high speeds.  Even in data-centers, use of 10G links is common.

The charter should not include such specific assumptions, particularly
given the fast moving changes that are happening in our industry
especially in the area of packet forwarding design.

What specifically are you objecting to?

I have not seen such assumptions in other charters and I don't think
that they have a place in this one.

What specific assumption are you objecting to and what reasoning do you have
beyond historical?

In terms of choice of document stream (experimental vs PS),
that is a decision that can be taken at the time of publication
when more information will be available in terms of potential
market take-up, expected/actual deployment scenarios,
breadth of implementation and implementation experience.

At this time, a sufficiently compelling case has not been made to convince that
PS is anywhere near appropriate for this change of adding a completely new forwarding
algorithm and a fourth  encapsulation to go with IPv4, IPv6, and MPLS to the Internet
architecture for the next 15+ years.

It is true that if that changes between now and when drafts are ready to progress, that can
be revisited.

There are WGs that have been chartered to do experimental work in the past.  I understand
that it is disappointing that there wasn't a strong case for more than experimental at this time.

I have been extremely clear since the last IETF that I was only considering Experimental for
the WG for the initial chartering.

Whilst this technology may be deployed in the Internet core,
it my also be deployed at the edge where a much lower threshold
is applicable.

The technology needs to work in both locations - given the use-cases.  What specifically are
you objecting to?

I fear that by introducing these caveats the IETF is entrenching the
perception that it slows technology down rather than embracing
and encouraging innovation.

By creating a WG for open collaboration and defining an ambitious new forwarding technology,
the IETF is not embracing and encouraging innovation?  I suppose it's all in the eye of the
beholder - but to me it feels like "give an inch and get pushed for a mile".

I would therefore suggest removing the text on implementation
styles and document stream constraints.

IF the encapsulations are specified in a way that two independent interoperable implementations
are not available, it both increases the risk that we might end up with two different versions - one
Experimental and another through bitter experience that is PS later - and is a poor indication of
the lack of industry support and interest in the technology and its use.

Regards,
Alia


- Stewart


On 11/02/2015 20:44, Alia Atlas wrote:
I have been working on getting a charter together for BIER with the intent of pushing for it to be chartered before the Dallas IETF.  This has not yet gone through IESG review and it may have some aspects updated.

Please send comments here.

The charter can be found at http://datatracker.ietf.org/doc/charter-ietf-bier/
and is included below as well.


WG Chairs:
  Greg Shepherd  <[e-mail]<mailto:[e-mail]>>
  Tony Przygienda <[e-mail]<mailto:[e-mail]>>


In conventional IP multicast forwarding, the packets of a given
multicast "flow" are forwarded along a tree that has been constructed
for the specific purpose of carrying that flow.  This requires transit
nodes to maintain state on a per-flow basis, and requires the transit
nodes to participate in multicast-specific tree building protocols.
The flow to which a packet belongs is determined by its IP source and
destination address fields.

BIER (Bit Index Explicit Replication) is an alternative method of
multicast forwarding.  It does not require any multicast-specific
trees, and hence does not require any multicast-specific tree building
protocols.  Within a given "BIER domain", an ingress node encapsulates
a multicast data packet in a "BIER header".  The BIER header
identifies the packet's egress nodes in that domain.  Each possible
egress node is represented by a a single bit within a bitstring; to
send a packet to a particular set of egress nodes, the ingress node
sets the bits for each of those egress nodes, and clears the other
bits in the bistring.  Each packet can then be forwarded along the
unicast shortest path tree from the ingress node to the egress nodes.
Thus there are no per-flow forwarding entries.

Due to the particular sensitivity of adding new significant
functionality into the data-plane at high link speeds, the BIER work
will progress as Experimental.  As described in item (9) below, the
work may become Standards Track once there is sufficient experience
with the benefits and downsides of the technology.

BIER is initially chartered to do experimental work on this new
multicast forwarding mechanism as follows:

   1) BIER architecture: The WG will publish an architecture, based
   upon draft-wijnands-bier-architecture-04.  It will include the
   normative algorithm for how BIER packet forwarding is done.  It
   will specify the information that is required by a BIER header to
   support BIER forwarding.

   2) BIER encapsulation: The working group should assume that the
   technology will need to be embedded in the data plane and operate
   at the highest packet line speeds.  The WG will publish a document
   defining an MPLS-based encapsulation based upon
   draft-wijnands-mpls-bier-encapsulation-02. Due to the critical need
   to have a high-quality and stable RFC for a new data-plane
   encapsulation, the MPLS-based encapsulation draft shall wait after
   WGLC and not progress to IETF Last Call until there are two
   independent interoperable implementations.

   As a secondary focus, the WG may also work on one non-MPLS
   data-plane encapsulation.  This draft also shall wait after WGLC
   and not progress to IETF Last Call until there are two independent
   interoperable implementations.  This draft must focus on and
   include the following details:

       a) What is the applicability of the encapsulation and for which
       use-cases is this encapsulation required?

       b) Does this proposed encapsulation imply any changes to the
       MPLS-based encapsulation?

       c) What design choices have been made for the encapsulation
       type and the included fields.

       d) The proposed encapsulation with considerations given to at
       least OAM, Class of Service, security, fragmentation, TTL.

   3) Transition Mechanisms: The WG will describe how BIER can be
   partially deployed and still provide useful functionality.  A
   minimum of the necessary mechanisms to support incremental
   deployment and/or managing different BIER mask-length compatibility
   may be defined.  Each such mechanism must include an applicability
   statement to differentiate its necessity from other proposed
   mechanisms.

   4) Applicability Statements: The WG will work on a document
   describing how BIER can be applied to multicast L3VPN and to EVPN.
   This draft will describe what mechanism is used to communicate the
   group membership between the ingress router and the egress routers,
   what scalability considerations may arise, and any deployment
   considerations.

   5) Use Case: The WG may produce one use-case document that clearly
   articulates the potential benefits of BIER for different use-cases.
   This would be based upon draft-kumar-bier-use-cases-01.

   6) OAM: The WG will describe how OAM will work in a BIER domain and
   what simplifications BIER offers for managing the multicast
   traffic.  A strong preference will be given to extensions to
   existing protocols.

   7) Management models: The WG may work on YANG models and, if needed,
   MIB modules to support common manageability.

   8) IGP extensions.  When a BIER domain falls within a "link state IGP""
   network, the information needed to set up the BIER forwarding tables
   (e.g., the mapping between a given bit position and a given egress
   router) may be carried in the link state advertisements of the IGP.  The
   link state advertisments may also carry other information related to
   forwarding (e.g., the IGP may support multiple topologies, in which case
   it may be necessary to advertise which topologies are to be used for BIER
   forwarding).  Any necessary extensions to the IGP will be specified by
   the WG, in cooperation with the ISIS and OSPF WGs.

   9) Deployment Experience: Once there is deployment experience, the
   WG will produce a document describing the benefits, problems, and
   trade-offs for using BIER instead of traditional multicast
   forwarding mechanisms.  Ideally, this should also contain an
   analysis of the impact and benefit of the new BIER data-plane to
   the overall Internet architecture.  This document is intended to be
   used to evaluate whether to recharter BIER to produce Standards
   Track RFCs.

The BIER working group will coordinate with several different working
groups and must include the relevant other working groups during
working group last call on the relevant drafts.  BIER will coordinate
with MPLS on the MPLS-based encapsulation and associated MPLS-based
OAM mechanisms.  BIER will coordinate with ISIS and OSPF on extensions
to flood BIER-related information.  BIER will coordinate with BESS and
IDR on the applicability of existing BGP-based mechanisms for
providing multicast group membership information.

Regards,
Alia


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