Re: [Bier] proposed BIER charter

[Stewart Bryant <[e-mail]>]

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.

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.

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

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.

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.

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

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

- 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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