Re: [spring] draft-ietf-spring-srv6-network-programming: Section 4.16

["Pablo Camarillo (pcamaril)" <[e-mail]>]

Li,

   Node1's
   Tenant-100 IPv4 table is: T.Encaps with SRv6 Policy <B:3:C4::,
   B:8:D100::>.

   When 1 receives a packet P from CE-A destined to 20.20.20.20, P looks
   up its tenant-100 IPv4 table and finds an SR-VPN entry 20/8.  As a
   consequence, 1 pushes an outer header with SA=A:1::, DA=B:3:C4::,
   NH=SRH followed by SRH (B:8:D100::, B:3:C4::; SL=1; NH=4). 1 then
   forwards the resulting packet on the interface to 2.

   2 forwards to 3 along the path to B:3::/32.

   When 3 receives the packet, 3 matches the DA in its "My SID Table"
   and finds the bound function End.X to neighbor 4. 3 notes the PSP
   capability of the SID B:3:C4::. 3 sets the DA to the next SID
   B:8:D100::. As 3 is the penultimate segment hop, it performs PSP and
   pops the SRH. 3 forwards the resulting packet to 4.

   4, 6 and 7 forwards along the path to B:8::/32.

  When 8 receives the packet, 8 matches the DA in its "My SID Table"
   and finds the bound function End.DT(100).  As a result, 8 decaps the
   outer header, looks up the inner IPv4 DA (20.20.20.20) in tenant-100
   IPv4 table, and forward the (inner) IPv4 packet towards CE-B.

Node 3 receives the packet SA=A:1::, DA=B:3:C4::,NH=SRH followed by SRH (B:8:D100::, B:3:C4::; SL=1; NH=4)
The SID B:3:C4:: is associated with the End.X behavior with PSP support. Node 3 is going to decrement SL, copy the segment B:8:D100:: into the IPv6 DA and set the packet’s egress adjacency to J (adjacency associated with that SID instance). Additionally, (PSP) it will check what is the SL value in the SRH. If the SL=0 it will remove the SRH from the packet.

The segment B:3:C4:: is the penultimate SID in the segment list <B:3:C4::, B:8:D100::>. Note that the PSP behavior is not related to IP hops.

Cheers,
Pablo.

From: li zhenqiang <[e-mail]>
Date: Thursday, 17 October 2019 at 06:11
To: "Pablo Camarillo (pcamaril)" <[e-mail]>, Ron Bonica <rbonica=[e-mail]>, "[e-mail]" <[e-mail]>
Cc: draft-ietf-spring-srv6-network-programming <[e-mail]>
Subject: Re: Re: [spring] draft-ietf-spring-srv6-network-programming: Section 4.16

Hi Pablo,

I am still confused by the example in section 2.8.1. Node 3 is the destionation of SID B:3:C4::, why should it behave PSP for this SID? While for SID B:8:D100::, it is an END.DT4, the PSP behavior is not defined for this kind of SIDs. Node 3 should not behave PSP for SID B:8:D100::, neither.  Would you please explain node 3 is the penultimate segment hop of which node or which segment? Suppose the behavior is correct, may I know the benifit you gain in this example?

Many Thanks,
Zhenqiang Li
________________________________
[e-mail]

From: Pablo Camarillo (pcamaril)<mailto:[e-mail]>
Date: 2019-10-16 00:45
To: li zhenqiang<mailto:[e-mail]>; Ron Bonica<mailto:rbonica=[e-mail]>; [e-mail]<mailto:[e-mail]>
CC: draft-ietf-spring-srv6-network-programming<mailto:[e-mail]>
Subject: Re: [spring] draft-ietf-spring-srv6-network-programming: Section 4.16
Li,

I have replied the technical questions regarding PSP and USP in the email thread from one week ago.
You have not provided any technical concern.

> “Further, the example for PSP in the companion doc srv6-net-pgm-illustration is wrong. PSP is used for END.DT4 in the companion doc while flavors are only defined for END, END.X and END.T in srv6-network-programming.”

The illustration in section 2.8.1 is correct. Please re-read it. PSP is used at node 3 together with the End.X behavior.

Regards,
Pablo.

Replies from one week ago:
https://mailarchive.ietf.org/arch/msg/spring/V0ZpjVLSVZxHaBwecXFxqJjlg_c
https://mailarchive.ietf.org/arch/msg/spring/WrYzRZC0HKVgBYaYMCQVcTWrfak


From: li zhenqiang <[e-mail]>
Date: Tuesday, 15 October 2019 at 09:32
To: Ron Bonica <rbonica=[e-mail]>, "[e-mail]" <[e-mail]>
Cc: draft-ietf-spring-srv6-network-programming <[e-mail]>
Subject: Re: [spring] draft-ietf-spring-srv6-network-programming: Section 4.16
Resent from: <[e-mail]>
Resent to: <[e-mail]>, <[e-mail]>, <[e-mail]>, <[e-mail]>, <[e-mail]>, <[e-mail]>
Resent date: Tuesday, 15 October 2019 at 09:32

I suggest this section be removed from this version until the community reaches rough consensus.
Further, the example for PSP in the companion doc srv6-net-pgm-illustration is wrong. PSP is used for END.DT4 in the companion doc while flavors are only defined for END, END.X and END.T in srv6-network-programming.

Best Regards,
Zhenqiang Li
________________________________
[e-mail]

From: Ron Bonica<mailto:rbonica=[e-mail]>
Date: 2019-10-15 02:42
To: SPRING WG List<mailto:[e-mail]>
Subject: [spring] draft-ietf-spring-srv6-network-programming: Section 4.16
Authors,

Lacking the B.INSERT and T.INSERT functions, can you describe a use-case for the PSP and USP flavors of the END, END.X and END.T functions?

                                              Ron



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