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 <[email protected]> Date: Thursday, 17 October 2019 at 06:11 To: "Pablo Camarillo (pcamaril)" <[email protected]>, Ron Bonica <[email protected]>, "[email protected]" <[email protected]> Cc: draft-ietf-spring-srv6-network-programming <[email protected]> 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 ________________________________ [email protected] From: Pablo Camarillo (pcamaril)<mailto:[email protected]> Date: 2019-10-16 00:45 To: li zhenqiang<mailto:[email protected]>; Ron Bonica<mailto:[email protected]>; [email protected]<mailto:[email protected]> CC: draft-ietf-spring-srv6-network-programming<mailto:[email protected]> 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 <[email protected]> Date: Tuesday, 15 October 2019 at 09:32 To: Ron Bonica <[email protected]>, "[email protected]" <[email protected]> Cc: draft-ietf-spring-srv6-network-programming <[email protected]> Subject: Re: [spring] draft-ietf-spring-srv6-network-programming: Section 4.16 Resent from: <[email protected]> Resent to: <[email protected]>, <[email protected]>, <[email protected]>, <[email protected]>, <[email protected]>, <[email protected]> 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 ________________________________ [email protected] From: Ron Bonica<mailto:[email protected]> Date: 2019-10-15 02:42 To: SPRING WG List<mailto:[email protected]> 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 Juniper Business Use Only
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