Re: [Bier] proposed BIER charter

[Stewart Bryant <[e-mail]>]

On 12/02/2015 15:13, Alia Atlas wrote:
> 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 deployment.
I think my three key points were:

a) We should not prejudge the technology at this stage, but rather should
take a contingency approach, i.e. make a decision when we need to make
it and have more information, rather than make it now and risk either
creating a self fulfilling prophecy, or needing to revisit this decision
later with all the associated work.

b) Listen to what David Ward was saying in his talk in Hawaii about the
risk of the IETF becoming irrelevant in the face of the speed of open 
source.
In this case we seem to be putting up barriers to speed of execution
rather than breaking them down.

c) Do not pre-judge how a technology of this type will be implemented
given the re-balancing we are seeing between s/w and h/w, i.e. do not
express a view on implementation technology in a charter. In the version
of the charter I reviewed you explicitly called for a h/w implementation.


>
> 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.
At this time we have no evidence either way, so why make
a statement at all, why not gather the evidence as we do the
engineering?

In one of the cases (BEIR/MPLS) it is not clear that this is an extension
beyond the norm. Certainly it  seems nothing worse than VXLAN
which is headed to be a de-facto standard.

>
> 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?
The edge case will surely be operating in an environment where
s/w forwarding is in ascendency and thus may just be another
NFV function. My concern is that you were asserting a h/w forwarding
paradigm which is not the current industry trajectory for the edge.
>
>     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 object to that statement which seems to me to be contra to the IETF
ethos of community consensus.

>
>     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.
"IF the encapsulations are specified in a way that two independent 
interoperable implementations
are not available, " Does not parse.

The specification needs to be implementation agnostic and compatible 
with any
reasonable implementations platform: h/w, f/w, s/w. Now you could perhaps
assert that you need one of each style, but that was not what you 
proposed, you
proposed h/w.

- Stewart

> 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
>>
>>
>>     _______________________________________________
>>     BIER mailing list
>>     [e-mail]  <mailto:[e-mail]>
>>     https://www.ietf.org/mailman/listinfo/bier
>
>
>     -- 
>     For corporate legal information go to:
>
>     http://www.cisco.com/web/about/doing_business/legal/cri/index.html
>
>


-- 
For corporate legal information go to:

http://www.cisco.com/web/about/doing_business/legal/cri/index.html