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

[Peter Psenak <[e-mail]>]

On 29/05/2020 12:12, Gyan Mishra wrote:
> 
> 
> On Fri, May 29, 2020 at 5:11 AM Peter Psenak 
> <ppsenak=[e-mail] <mailto:[e-mail]>> 
> wrote:
> 
>     Hi Ron,
> 
>     On 28/05/2020 18:55, Ron Bonica wrote:
>      > Weibin,
>      >
>      > Inline…..
>      >
>      >                       Ron
>      >
>      > Juniper Business Use Only
>      >
>      > *From:* Wang, Weibin (NSB - CN/Shanghai)
>     <[e-mail] <mailto:[e-mail]>>
>      > *Sent:* Thursday, May 28, 2020 10:35 AM
>      > *To:* Ketan Talaulikar (ketant) <[e-mail]
>     <mailto:[e-mail]>>; Ron Bonica
>      > <[e-mail] <mailto:[e-mail]>>; Joel M.
>     Halpern <[e-mail] <mailto:[e-mail]>>
>      > *Cc:* [e-mail] <mailto:[e-mail]>; [e-mail]
>     <mailto:[e-mail]>; 6man <[e-mail] <mailto:[e-mail]>>
>      > *Subject:* RE: [spring] CRH is back to the SPRING Use-Case - Re:
>     Size of
>      > CR in CRH
>      >
>      > *[External Email. Be cautious of content]*
>      >
>      > Hi Ron,
>      >
>      > After reading through many mails related to CRH in list, I found all
>      > CRH-SIDs (allocated to prefix-sid <loosely forwarding>and
>     Adj-sid<strict
>      > forwarding>) are of local significance in fact, its operation
>     actually
>      > is not same as MPLS Label nor SR-MPLS label (such as domain-wide
>     prefix
>      > SID/label), all CRH-SIDs are locally allocated by node itself
>     based on
>      > local FIB6, independent of other CRH-SID allocated by other nodes
>     in CRH
>      > domain; so every node (Maybe except  ingress PE of CRH domain)
>       has no
>      > useful to learn other SIDs allocated by other nodes by IGP-extension
>      > advertising. Its deployment must have controller (considering
>     dynamic
>      > mechanism), the controller learn all CRH-SIDs from each node to
>     program
>      > the source path under path calculation requirement from ingress PE.
>      >
>      > [RB] Absolutely correct !!
> 
>     if CRH-SIDs are of local significance how is the loose source routing
>     going to be supported?
> 
>     Or is CRH only supposed to be used for strict hop-by-hop source
>     routing?
>     If so, the use case would be quite limited.
> 
>     Honestly, strictly technically, I do not see much difference between
>     CRH
>     and RFC8663 & RFC4023 combo. Former uses an extra extension header, the
>     latter uses the next-header. Rest looks same.
> 
> 
>      Gyan> Peter - You mentioned a key point which is is a major 
> difference.
> 
> I thank you for pointing out this critical point for everyone in both 
>   Spring WG & 6MAN WG -now one big happy family🙏😀
> 
> With RFC 8663 SR-MPLS over
> IPV6 using RFC 4023 w/o GRE with IPv6 encap here is what the end result 
> of the packet looks like:
> 
>   SR-MPLS over IPv6 =  Next header encapsulation
> 
>     IPv6 |  SR-MPLS |. Customer payload
> 
> Operators wanting CRH don’t want the MPLS Layer 2 1/2 MPLS data plane 
> insertion into the packet mucking up the packet and want to stay clear 
> of MPLS since they want a clean and pure IPV6 packet that follows RFC 
> 8200 IPV6 specification.

you don't want MPLS, so you wrap the same data to a new extension header 
and give it a new name. And you suddenly like it. Hmm, does not sound 
like a solid technical argument to me.

thanks,
Peter


> 
> So the use case for RFC 8663 is very different as it is widely deployed 
> for interworking SR-MPLS with SRV6 - Outlined in Mirsky draft below:
> 
> https://datatracker.ietf.org/doc/html/draft-mirsky-6man-unified-id-sr-06
> 
> CRH is no different then using any other routing header proposal such as 
> 6lo for RPL.
> 
> https://tools.ietf.org/html/rfc8138
> 
> CRH Packet format:
> 
> IPV6  CRH | Customer payload
> 
> The additional encapsulation makes a big difference and it’s really 
> apples versus oranges and not the same at all.
> 
> 
>    Why would any operator use SR-MPLS over IP to for steering traffic if 
> they have an existing IPV6 data plane they want to utilize.
> 
> They would use SRv6 or CRH and would pick CRH to avoid MSD (maximum sid 
> depth) issues for long strict paths and not have to deal with extra 
> complexity of all the compression variants.
> 
> 
> Decision tree:
> If an operator wanted an MPLS data plane variant they would go with 
> SR-MPLS but if they want IPV6 data plane variant they obviously would 
> pick an option that uses IPv6 data plane and that would be the SRV6 or CRH.
> 
> In order to even remotely justify from my point of view that SR-MPLS 
> over IPv6 would used for anything other than the obvious “interworking” 
> between SR-MPLS and SRV6, you would really have to prove that an 
> operator is willing to add MPLS into the mix when they want IPV6.  Not 
> possible.
> 
> I can guarantee no operator would do that.
> 
> 
> 
>     thanks,
>     Peter
> 
> 
> 
>      >
>      > I suggested you should describe more detail about how to create
>     CRH-SID
>      > entry (in CRH-FIB) in this CRH draft, is it based on local FIB6,
>     if it
>      > is, how to do synchronization between CRH-FIB and FIB6?
>      >
>      > [RB] In some deployment scenarios, the IPv6 FIB and the CRH-FIB are
>      > populated by an IGP. Please review and comment on the IS-IS CRH
>     document
>      >
>     <https://datatracker.ietf.org/doc/draft-bonica-lsr-crh-isis-extensions/>.
>     I
>      > am excited to collaborate with you on that .
>      >
>      > [RB] In other deployment scenarios, the IPv6 FIB and / or the
>     CRH-FIB
>      > are populated by a controller. If you are interested in that
>     scenario,
>      > again, we would be excited to collaborate with you.
>      >
>      >                                                     Ron
>      >
>      > Above is my understanding, if not right,pls correct me.
>      >
>      > Wang Weibin
>      >
>      > *From:*ipv6 <[e-mail] <mailto:[e-mail]>
>     <mailto:[e-mail] <mailto:[e-mail]>>> *On
>      > Behalf Of *Ketan Talaulikar (ketant)
>      > *Sent:* 2020年5月28日19:46
>      > *To:* Ron Bonica <rbonica=[e-mail]
>     <mailto:[e-mail]>
>      > <mailto:rbonica <mailto:rbonica>=[e-mail]
>     <mailto:[e-mail]>>>; Joel M. Halpern
>      > <[e-mail] <mailto:[e-mail]>
>     <mailto:[e-mail] <mailto:[e-mail]>>>
>      > *Cc:* [e-mail] <mailto:[e-mail]>
>     <mailto:[e-mail] <mailto:[e-mail]>>; [e-mail]
>     <mailto:[e-mail]>
>      > <mailto:[e-mail] <mailto:[e-mail]>>; 6man
>     <[e-mail] <mailto:[e-mail]> <mailto:[e-mail]
>     <mailto:[e-mail]>>>
>      > *Subject:* RE: [spring] CRH is back to the SPRING Use-Case - Re:
>     Size of
>      > CR in CRH
>      >
>      > Hi Ron,
>      >
>      > Some of the operators may not care about the SR name, but it is
>     clear to
>      > me that the proposal in the CRH draft is a subset of Segment Routing
>      > (i.e. a reduced portion of Spring Architecture) that only supports
>      > prefix and adjacency SIDs as indicated by the two "forwarding
>     methods".
>      >
>      >
>     https://tools.ietf.org/html/draft-bonica-6man-comp-rtg-hdr-22#section-4
>      >
>     <https://urldefense.com/v3/__https:/tools.ietf.org/html/draft-bonica-6man-comp-rtg-hdr-22*section-4__;Iw!!NEt6yMaO-gk!VMgRZ_fS_8pBN886aeeU1sFZpteVAkwQNu6xqWRsR27VhEn_wpAuXmcCngHDrhN8$>
>      >
>      >     o  Forward the packet to the next-hop along the least-cost
>     path to
>      > *>>> Prefix SID*
>      >
>      >        the next segment endpoint.
>      >
>      >     o  Forward the packet through a specified interface to the
>     next *>>>
>      > Adjacency SID*
>      >
>      >        segment endpoint.
>      >
>      > Given the use of mapping IDs and mapping FIB, the proposal is
>     comparable
>      > more to SR-MPLS than SRv6. It is better to do a holistic analysis
>     of any
>      > proposal such as CRH that is introducing an MPLS label like mapping
>      > construct into IPv6 architecture - doing so should be considered
>     as a
>      > significant change to IPv6.
>      >
>      > Thanks,
>      >
>      > Ketan
>      >
>      > -----Original Message-----
>      >
>      > From: Ron Bonica <rbonica=[e-mail]
>     <mailto:[e-mail]>
>      > <mailto:rbonica <mailto:rbonica>=[e-mail]
>     <mailto:[e-mail]>>>
>      >
>      > Sent: 25 May 2020 21:14
>      >
>      > To: Ketan Talaulikar (ketant) <[e-mail]
>     <mailto:[e-mail]>
>      > <mailto:[e-mail] <mailto:[e-mail]>>>; Joel M.
>     Halpern <[e-mail] <mailto:[e-mail]>
>      > <mailto:[e-mail] <mailto:[e-mail]>>>
>      >
>      > Cc: rtg-ads@ietf..org <mailto:[e-mail]>
>     <mailto:[e-mail] <mailto:[e-mail]>>; [e-mail]
>     <mailto:[e-mail]>
>      > <mailto:[e-mail] <mailto:[e-mail]>>; 6man
>     <[e-mail] <mailto:[e-mail]> <mailto:[e-mail]
>     <mailto:[e-mail]>>>
>      >
>      > Subject: RE: [spring] CRH is back to the SPRING Use-Case - Re:
>     Size of
>      > CR in CRH
>      >
>      > Ketan,
>      >
>      > It would not be fair to say that these operators  "wish to deploy a
>      > Traffic Engineering solution using a subset of Segment Routing".
>      >
>      > It would be fair to say that these operators  "wish to deploy IPv6
>      > Traffic Engineering".  Some of these operators don't care about
>     SR. Some
>      > are actively averse to SRv6. All they want is a Routing header.
>      >
>      >                                                                   Ron
>      >
>      > Juniper Business Use Only
>      >
>      > -----Original Message-----
>      >
>      > From: Ketan Talaulikar (ketant)
>     <ketant=[e-mail] <mailto:[e-mail]>
>      > <mailto:ketant <mailto:ketant>=[e-mail]
>     <mailto:[e-mail]>>>
>      >
>      > Sent: Monday, May 25, 2020 5:21 AM
>      >
>      > To: Ron Bonica <[e-mail] <mailto:[e-mail]>
>     <mailto:[e-mail] <mailto:[e-mail]>>>; Joel
>      > M. Halpern <[e-mail] <mailto:[e-mail]>
>     <mailto:[e-mail] <mailto:[e-mail]>>>
>      >
>      > Cc: rtg-ads@ietf..org <mailto:[e-mail]>
>     <mailto:[e-mail] <mailto:[e-mail]>>; [e-mail]
>     <mailto:[e-mail]>
>      > <mailto:[e-mail] <mailto:[e-mail]>>; 6man
>     <[e-mail] <mailto:[e-mail]> <mailto:[e-mail]
>     <mailto:[e-mail]>>>
>      >
>      > Subject: RE: [spring] CRH is back to the SPRING Use-Case - Re:
>     Size of
>      > CR in CRH
>      >
>      > [External Email. Be cautious of content]
>      >
>      > Hi Ron,
>      >
>      > Thanks for that clarification.
>      >
>      > I note that you are not anymore saying "Are not interested in SR"
>     like
>      > you had mentioned before the WG adoption call :
>      >
>     https://urldefense.com/v3/__https://mailarchive.ietf.org/arch/msg/ipv6/LheyFD_uwuHp7tiG8Y1CwKngDYI/__;!!NEt6yMaO-gk!X2qW2zTZEbZRfBSE6c_KM-k7aIvZTIT9bycp3jyFJ3sTbf8MtGo4E_uGX7zYZ7lk$
> 
>      >
>     <https://urldefense.com/v3/__https:/mailarchive.ietf.org/arch/msg/ipv6/LheyFD_uwuHp7tiG8Y1CwKngDYI/__;!!NEt6yMaO-gk!X2qW2zTZEbZRfBSE6c_KM-k7aIvZTIT9bycp3jyFJ3sTbf8MtGo4E_uGX7zYZ7lk$>
>      >
>      > So, would it be fair to say that the operator that you are
>     referring to
>      > below, wishes to deploy a Traffic Engineering solution using a
>     subset of
>      > Segment Routing (i.e. a reduced portion of Spring Architecture) that
>      > only supports prefix and adjacency SIDs as indicated by the two
>      > "forwarding methods" that are referred to in
>     draft-bonica-6man-comp-rtg-hdr?
>      >
>      > Thanks,
>      >
>      > Ketan
>      >
>      > -----Original Message-----
>      >
>      > From: Ron Bonica <rbonica=[e-mail]
>     <mailto:[e-mail]>
>      > <mailto:rbonica <mailto:rbonica>=[e-mail]
>     <mailto:[e-mail]>>>
>      >
>      > Sent: 25 May 2020 09:03
>      >
>      > To: Ketan Talaulikar (ketant) <[e-mail]
>     <mailto:[e-mail]>
>      > <mailto:[e-mail] <mailto:[e-mail]>>>; Joel M.
>     Halpern <[e-mail] <mailto:[e-mail]>
>      > <mailto:[e-mail] <mailto:[e-mail]>>>
>      >
>      > Cc: rtg-ads@ietf..org <mailto:[e-mail]>
>     <mailto:[e-mail] <mailto:[e-mail]>>; [e-mail]
>     <mailto:[e-mail]>
>      > <mailto:[e-mail] <mailto:[e-mail]>>; 6man
>     <[e-mail] <mailto:[e-mail]> <mailto:[e-mail]
>     <mailto:[e-mail]>>>
>      >
>      > Subject: RE: [spring] CRH is back to the SPRING Use-Case - Re:
>     Size of
>      > CR in CRH
>      >
>      > Ketan,
>      >
>      > Please consider an operator who:
>      >
>      > - Wants a way to steer IPv6 packets through a specified path that
>      > includes many nodes (>8)
>      >
>      > - Does not want any of the following:
>      >
>      >          - A new VPN encapsulation technique
>      >
>      >          - A new service function chaining technique
>      >
>      >          - Network programming
>      >
>      >          - MPLS and uSID
>      >
>      >          - To encoding instructions in IPv6 addresses.
>      >
>      > These operators want a compact routing header, nothing more.
>      >
>      > 
>                                                                                 Ron
>      >
>      > Juniper Business Use Only
>      >
>      > -----Original Message-----
>      >
>      > From: ipv6 <[e-mail] <mailto:[e-mail]>
>     <mailto:[e-mail] <mailto:[e-mail]>>> On
>      > Behalf Of Ketan Talaulikar (ketant)
>      >
>      > Sent: Sunday, May 24, 2020 1:42 AM
>      >
>      > To: Joel M. Halpern <[e-mail]
>     <mailto:[e-mail]> <mailto:[e-mail]
>     <mailto:[e-mail]>>>
>      >
>      > Cc: rtg-ads@ietf..org <mailto:[e-mail]>
>     <mailto:[e-mail] <mailto:[e-mail]>>; [e-mail]
>     <mailto:[e-mail]>
>      > <mailto:[e-mail] <mailto:[e-mail]>>; 6man
>     <[e-mail] <mailto:[e-mail]> <mailto:[e-mail]
>     <mailto:[e-mail]>>>
>      >
>      > Subject: RE: [spring] CRH is back to the SPRING Use-Case - Re:
>     Size of
>      > CR in CRH
>      >
>      > [SNIP]
>      >
>      > I am looking for explanation of the "other ways" that CRH can be
>     used
>      > (i.e. those outside the Spring architecture). I am trying to
>     understand
>      > from the authors what would be the applicability of that
>     solution, it's
>      > use-cases and it's requirements. That is what, I believe, will
>     help us
>      > evaluate the CRH proposal in the context of this working call.
>     That will
>      > help us answer these questions like the scope of the SID, 32-bit or
>      > 16-bit or something else and what the CRH-FIB is going to turn
>     out like.
>      >
>      > [SNIP]
>      >
>      > ------------------------------------------------------
>      >
> 
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> -- 
> 
> <http://www.verizon.com/>
> 
> *Gyan Mishra*
> 
> /Network Solutions A//rchitect /
> 
> /M 301 502-1347
> 13101 Columbia Pike
> /Silver Spring, MD
> 
>