Re: [Srcomp] Section 3.1 (Analysis For SRv6 based)

["Darren Dukes (ddukes)" <[e-mail]>]

I believe there are some errors in this analysis, and propose the following corrections.

RFC8402: No
CRH does not use SRv6 architecture as specified in RFC8402
Some relevant sections of RFC8402:

  *   “SR can be applied to the IPv6 architecture with a new type of routing header called the SR Header (SRH) [IPv6-SRH<https://datatracker.ietf.org/doc/html/rfc8402#ref-IPv6-SRH>]  An instruction is associated with a segment and encoded as an IPv6 address.”
  *   “This document defines the IGP, BGP, and Binding segments for the SR-MPLS and SRv6 data planes.”
  *   “SRv6: the instantiation of SR on the IPv6 data plane.”
  *   “SRv6 SID: an IPv6 address explicitly associated with the segment.”
It does not use the SRv6 data plane nor the SRv6 control plane. It is a new data plane requiring a new control plane.
CRH SIDs are not SRv6 SIDs, CRH is not the SRv6 data plane.

U.PGM: No
As discussed in our meetings and documented in the analysis, there is no practical use of SRv6 SIDs encoded as CRH SIDs.

  *   Mapping CRH SIDs to SRv6 SIDs at the next segment endpoint has no practical use.
     *   For VPN SIDs the state explosion at P nodes makes the mapping entirely impractical

U.ALG: No
IP flexalgo is a new application, not SR.
As indicated draft-ietf-lsr-ip-flexalgo is used by CRH nodes as stated in the draft:

  “Using Flex-Algorithm for regular IPv4 and
   IPv6 prefixes represents a new Flex-Algorithm application (IP Flex-
   Algorithm), and as such the Flex-Algorithm participation for the IP
   Flex-Algorithm application MUST be signalled independently of any
   other Flex-Algorithm applications (e.g.  SR).”
CRH nodes cannot make use of draft-ietf-lsr-flex-algo and the SR application.  They cannot support the “way for a router to use IGPs to associate one or more SR Prefix-SIDs or SRv6 locators with a particular Flex-Algorithm.  Each such Prefix-SID or SRv6 locator then represents a path that is computed according to the identified Flex-Algorithm.” As specified in draft-ietf-lsr-flex-algo.


On 2021-06-01, 2:45 PM, "Srcomp" <[e-mail]> wrote:


Folks,

The following is an analysis of Section 3.1 (Analysis For SRv6 based) for the CRH:

   O U.RFC8402:  Yes
   o  U.RFC8754: No
   o  U.PGM:     Yes (It allows classic SIDs and supports all required SID types)

   o  U.IGP:     No  (draft-bonica-lsr-crh-isis-extensions)
   o  U.BGP:     No  (draft-sangli-bess-bpg-vpn-srm6
   o  U.POL:     No  (draft required)
   o  U.BLS:     No  (draft required)
   o  U.SVC:     N/A (covered in CRH draft)
   o  U.OAM:     N/A (covered in CRH draft)
   o  U.ALG:     Yes [I-D.ietf-lsr-ip-flexalgo uses much of I-D.ietf-lsr-flex-algo].

                                            Ron




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