RE: [spring] 答复: CRH is back to the SPRING Use-Case - Re: Size of CR in CRH

Andrew Alston <> Fri, 22 May 2020 16:27 UTC

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From: Andrew Alston <>
To: Aijun Wang <>, "'Ketan Talaulikar (ketant)'" <>, "'Joel M. Halpern'" <>
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Hi Ajun,

I cannot speak for what the cloud providers want – and will not attempt to put words in their mouths.  But, let me attempt to address this from my perspective as the employee of an operator.

The way I see it – operators are seeing declining revenues in bandwidth sales – have been for 20 years.  Being just an ISP – no longer gives the edge it once did – and while in Africa in a developing market such as the one I operate in, we’ve probably had a slower curve in the pure bandwidth market – the fact is that operators need to be able to differentiate themselves.  What this means is, building services on top of the infrastructure they have.  Effectively, I view the operator of the future as almost an over the top player on top of the hardware and fiber and infrastructure that underpins those services.

Now – if said operator goes to the market and buys a fully completed solution – that same solution – is always available to their competition.  Where the true differentiation comes in – will happen at multiple levels, in the service and support and resilience of the network – in the customer service – and in innovative products and services.  I believe that the operator that can build those products and services from the base building blocks – gives themselves an advantage.  Being able to steer traffic in granular ways opens itself to a world of possibilities.  And be that through SR-MPLS – be that using the CRH – or be that via SRv6 – each has positives and negatives and advantages and disadvantages.  I would argue that while we are very heavy users of SR-MPLS – and SR-MPLS will certainly have a strong future in our network – that does not negate the place that something like CRH has is our minds and in fact we have built some very interesting things on top of CRH which we are testing – the details of which I am sadly not free to disclose.

Now – if I want to innovate like this – and have my ideas and thoughts heard, I need these building blocks – because as I build on top of them, be it in production or in a lab environment – that leaves me the freedom to take what I have built and either keep it internal, or – where applicable – take those ideas and that intellectual property, and open it up to the rest of the world and let the market decide if they want it.  That expands the innovation base beyond the ideas and thoughts of a limited few vendors.

I argue strongly that to build a strong and competitive future, particularly in a developing market – a market which up until this point has had very very little influence on the technologies they run – requires people to be able to think out of the box – and use the tools available.  Some will take advantage of this paradigm – some will continue to turn to the vendors for every line of config – I believe that those who can use the lower level building blocks – are the ones that will win out – because innovation drives sustainability and the future.

Is CRH the only brick I want?  No – there are many of them – and there are many ideas – this is one – and you cannot build a house with a single brick – but – it is a brick that I view at least for us, operating in 15 countries, as a brick that is critical to some of the plans we have.

So – is this a brick we want? Yes.  Do I want every use case – every architecture that I use this brick for dictated to me by a vendor? Certainly not.  And I will finish this rather long email with this thought – the vendor that is prepared to work with the customers to innovate and help create the building blocks – and then work the customer as the customer innovates – is always going to end up finishing ahead of the vendor that tries to shove their ideas – which are formulated in offices thousands of miles from the on the ground realities of certain parts of the world – down the operators throats.

Hence – yes – I like simple building blocks


From: spring <> On Behalf Of Aijun Wang
Sent: Friday, 22 May 2020 18:55
To: Andrew Alston <>om>; 'Ketan Talaulikar (ketant)' <>rg>; 'Joel M. Halpern' <>
Cc:;; '6man' <>
Subject: [spring] 答复: CRH is back to the SPRING Use-Case - Re: Size of CR in CRH

Hi, Andrew and all:

Is  using the “Routing Header” to maneuver the path of packet a good idea?
From the viewpoint of the service provider, if we depend on the central controller/PCE to assure the QoS of application, we should simplify the network design and the network device.
Currently, both SRH and CRH deployment requires the presence of SDN controller/PCE, but the network/device complexity is not decreased.  How operator can benefit from the adoption of these technologies?

You have also mentioned the cloud provider. What their requirements is the openness/standard API from the device, this can give the most flexibility for network programming.
Why we don’t  dive into this direction?  There are several NorthBound interfaces/protocols exist in IETF standard.

For CRH and SRH, I think there are some similarity between them. CRH does not conflict with the IPv6 address, but requires the map table exist. Many experts will dispute again the similar problem.

Is CRH the brick that cloud provider want?

Best Regards.

Aijun Wang
China Telecom

发件人:<> [] 代表 Andrew Alston
发送时间: 2020年5月22日 17:25
收件人: Andrew Alston; Ketan Talaulikar (ketant); Joel M. Halpern
抄送:<>;<>; 6man
主题: Re: [spring] CRH is back to the SPRING Use-Case - Re: Size of CR in CRH

Just as a followup – which I think illustrates my point here.<>

If operators wanted fait accompli – why is it that Cisco – and other vendors – are starting to provide ASIC based API’s such that cloud providers and operators can do what they need on devices – rather than the dictates of vendors?  I think the very fact that the above article exists – illustrates the desire for simple building blocks.



From: spring <<>> On Behalf Of Andrew Alston
Sent: Friday, 22 May 2020 12:15
To: Ketan Talaulikar (ketant) <<>>; Joel M. Halpern <<>>
Cc:<>;<>; 6man <<>>
Subject: Re: [spring] CRH is back to the SPRING Use-Case - Re: Size of CR in CRH

Actually Ketan,

As an operator – I am looking for the tyre – I want the building block – because it allows me to both use what the vendors build on top of it – and to build my own stuff on top of it that is specific to my needs.

The tyre association is one such association – the brick is another – the brick was invented long before anyone created an architectural diagram to build a building.  CRH is a brick – that can be shaped to many purposes.

And as an operator – it is *exactly* what I want – without the dictates of what any vendor says I can do with it.

There are unique conditions in every operator environment – and if an operator is given the right bricks – and those bricks can be used to build something that is inter-operable across the vendors and within their specific domain – it is that building that gives the operator their competitive advantage.  If however, all operators are  handed a completed building – its much harder to build something that differentiates.

I must point out – in a world where we are seeing more and more white box technology – and where content providers are moving to building their own things pretty quickly – why do you think that is?  One reason I believe is because the requirements are not the same everywhere – and I have long believed that a standard should be such that an operator can take that standard – and use it within his specific domain to build on top of – and rather we have a standard brick such that the solutions that are built are portable – than every operator inventing their own bricks and nothing working together.

Again – the reason I support CRH – is because of the flexibility and simplicity it affords me as an operator – and because – we have specific use cases and things we wish to build on top of it – some of which – are pretty standard and happily in the public domain – other things – which are specific internally.  And I for one right now – am far more willing as an operator to pay for the bricks that let me build something that is competitive in the market than pay for fait accompli that is nothing more than the dictates for what vendors think I want.

And yes – I support the divorce of CRH for all things SPRING related – because the use cases beyond segment routing are multiple – and I have absolutely zero desire – plan – or anything else to use something like the PGM draft on my network and impose that level of overhead, complexity, overloading of the v6 address and what I view as a general corruption of the v6 architecture.  What I want – is a simple routing header – that I can build on – and that’s the end of the architecture that I want dictated to me.



From: ipv6 <<>> On Behalf Of Ketan Talaulikar (ketant)
Sent: Friday, 22 May 2020 08:24
To: Joel M. Halpern <<>>
Cc:<>;<>; 6man <<>>
Subject: RE: [spring] CRH is back to the SPRING Use-Case - Re: Size of CR in CRH

I am thinking that the operators would be looking for the car and not the tyre?


-----Original Message-----
From: Ketan Talaulikar (ketant)
Sent: 22 May 2020 10:55
To: 'Joel M. Halpern' <<>>
Cc:<>; 6man <<>>;<>
Subject: RE: [spring] CRH is back to the SPRING Use-Case - Re: Size of CR in CRH

Hi Joel,

I'll point you to RFC7855, RFC8355 and RFC8402 that cover both the data-planes for Spring. Then the RFC8354 which is focussed on SRv6. All this body of work along with a whole lot of discussion and brainstorming happening in the Spring WG provided the architecture, use-cases, applicability and requirements for SRH (RFC8754).

It may be so that many people in 6man focussed on only the IPv6 specific aspects as is their design expertise. But there were others (in 6man, Spring and other WGs) that were able to look at the solution in a holistic manner thanks to the body of work behind it.

Net-PGM builds on top of RFC8402 and RFC8754.

To give a real world analogy, let us understand what kind of a car we are trying to build (to carry goods/passengers or both and how much/many, what terrain it is meant for, what weather/environment conditions, how much speed/performance/fuel efficiency parameters required, etc.) before we start designing tyres for it.


-----Original Message-----
From: Joel M. Halpern <<>>
Sent: 22 May 2020 10:02
To: Ketan Talaulikar (ketant) <<>>
Cc:<>; 6man <<>>;<>
Subject: Re: [spring] CRH is back to the SPRING Use-Case - Re: Size of CR in CRH

Ketan, I am trying to figure out which documents you think were adopted and approved elsewhere to drive the 6man work on SRH.

I did find RFC 8354, which was a use case. It is not a problem statement. It is most definitely not an architecture. The only architecture documents I can find are general SR documents. Those did not justify a need for SRH. And I (at least) did not object to SRH on the basis of that gap.

Yes, SRH normatively references 8402. But 8402 does not drive any need for SRH. In fact, the actual text references to SRH are fairly cursory.
(The most significant is some terminology.)

In fact, as far as I can tell, the ties are such that there is no evidence in the documents that SPRING had any say in SRH. (the reality is more complex, I grant you. But there was no formal approval or signoff.)

As far as I can tell, there was no formal approval of anything by SPRING that can be read as a request to 6man to work on SRH. (Do remember that the SRH document was adopted by 6man in December of 2015.) The network programming draft did not even appear at 00 until March of 2017, 15 months later.

How, given this history, can you claim that CRH needs something more.
We have operators asking for this.


On 5/21/2020 11:53 PM, Ketan Talaulikar (ketant) wrote:
> Hi Bob,
> Perhaps I will try to make my case to you (and everyone else here) …
> one last time.
> This is how I've seen RH work being done in 6man until now (in a
> matter that fits its charter).
> 1) There is a WG (not 6man) that defines the problem statement,
> use-cases and architecture that requires RH
> 2) The 6man being the experts on IPv6 design, either take up the
> document that specifies that RH (or even if it is done in another WG,
> reviews it).
> So 6man has always had work done in (1) to reference and lean upon
> when doing (2).
> My argument of the shortcut in the case of this specific adoption is
> that we don't have (1).
> It is not in 6man charter nor expertise to take up (1) because CRH is
> not purely IPv6 work. It is not meant for "Internet" but a specific
> "limited domain". The SIDs that it introduces is a new "mapping ID"
> concept. It is not an IPv6 address and neither it is MPLS. This is a
> *_Routing_* Header and part of a new Source *_Routing_* solution.
> Therefore, without (1) being made available to 6man, I believe that
> working on (2) in 6man is to me a shortcutting of the IETF technical
> review process (specifically of the *_Routing_* area in this case) for
> a solution and does not provide the necessary reference for 6man to work on.
> Why the rush?
> I close my arguments.
> Thanks,
> Ketan
> -----Original Message-----
> From: Bob Hinden <<>>
> Sent: 22 May 2020 09:03
> To: Ketan Talaulikar (ketant) <<>>
> Cc: Bob Hinden <<>>; Brian Carpenter
> <<>>; Ron Bonica <<>>;
> Chengli (Cheng Li) <<>>; Zafar Ali (zali)
> <<>>; Robert Raszuk <<>>;<>;
> 6man <<>>
> Subject: Re: [spring] CRH is back to the SPRING Use-Case - Re: Size of
> CR in CRH
> Ketan,
> > On May 21, 2020, at 8:12 PM, Ketan Talaulikar (ketant)
> <
<>> <>> wrote:
> >
> > Hi Brian,
> >
> > Please see my previous response to your comments.
> >
> > My argument is not legalistic. I am not as experience in IETF work
> as you and Bob are. But what I understand is that the reason why we
> have these "legal" process of charters and BoF is to enable a proper
> technical discussion with the right context and details of the
> proposal presented for review of the community.
> >
> > I do not see how shortcutting them helps anyone and I wonder why it
> is being done in this case?
> There is no short cutting here.  The adoption call is to determine if
> there is interest in the w.g. to take this work into 6man.   If it
> becomes a w.g. draft, then the w.g. is responsible to decide what
> happens next.
> It’s a first step, it is not a decision to publish it.
> Bob (w/ w.g. chair hat on)
> >
> > Thanks,
> > Ketan
> >
> > -----Original Message-----
> > From: Brian E Carpenter <
<>> <>>
> > Sent: 22 May 2020 04:18
> > To: Ketan Talaulikar (ketant) <
<>> <>>; Ron Bonica <
<>> <>>; Chengli (Cheng Li) <
<>> <>>; Zafar Ali (zali) <
<>> <>>; Robert Raszuk <
<>> <>>
> > Cc:<> <>; 6man <
<>> <>>
> > Subject: Re: CRH is back to the SPRING Use-Case - Re: Size of CR in
> >
> > On 22-May-20 05:26, Ketan Talaulikar (ketant) wrote:
> > ....> It is the 6man charter that precludes it from defining a new
> Source Routing solution..
> >> “It is not chartered to develop major changes or additions to the
> IPv6 specifications.”
> >
> > If this addition was major, that would be true. But adding a new RH
> type is well within the scope of maintenance, IMHO. We have already
> done it quite recently.
> >
> > In any case, legalistic arguments about WG charters are really not
> how we should take technical decisions.
> >
> > Regards
> >    Brian
> >
> >
> > _______________________________________________
> > spring mailing list
> ><> <>
> ><>
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