Re: [mpls] [Detnet] [Pals] FW: New Version Notification for draft-jags-mpls-ps-mna-hdr-00.txt
Loa Andersson <loa@pi.nu> Thu, 27 April 2023 07:03 UTC
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Date: Thu, 27 Apr 2023 09:03:34 +0200
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To: Tony Li <tony.li@tony.li>, Greg Mirsky <gregimirsky@gmail.com>
Cc: mpls <mpls@ietf.org>, "Jaganbabu Rajamanickam (jrajaman)" <jrajaman=40cisco.com@dmarc.ietf.org>, DetNet Chairs <detnet-chairs@ietf.org>, mpls-chairs <mpls-chairs@ietf.org>, draft-jags-mpls-ps-mna-hdr@ietf.org, pals-chairs@ietf.org, pals@ietf.org, DetNet WG <detnet@ietf.org>
References: <MN2PR11MB4064AF61278C1AE671A11927D0BA9@MN2PR11MB4064.namprd11.prod.outlook.com> <570EEC5D-4167-4461-B4A1-96ABAFA949C7@gmail.com> <CAMZsk6cnOh5AHtSmR3=jVX7VsJwkAcbq0VPSCH=edjkXChnH8w@mail.gmail.com> <40b332dd-d33a-6dd8-574f-af0a0be49efb@pi.nu> <CAMZsk6fNZ7EpzRq_rVSwzKoe=z2S_ucxuYfVMAR6cS9ZwZ3G5w@mail.gmail.com> <a8bb80ab-199c-90dd-3c09-fb407f7663a5@pi.nu> <2D696DF1-3BD1-4C2C-AFCA-747B237B94C1@tony.li> <b5a00076-1dc6-ce95-273d-242a791791f7@pi.nu> <1154B6AF-B6FE-4449-B46C-88FFD2AB4C2D@tony.li> <CA+RyBmWWrV=z0eU306jF32LTu52bbm_6OLUXga9d1x2rDgEJkw@mail.gmail.com> <1F294BE2-6D8C-4187-970E-F19E75CB08D5@tony.li>
From: Loa Andersson <loa@pi.nu>
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Archived-At: <https://mailarchive.ietf.org/arch/msg/mpls/48qmvyEeLoxMSyw2TrH6lcp5x7k>
Subject: Re: [mpls] [Detnet] [Pals] FW: New Version Notification for draft-jags-mpls-ps-mna-hdr-00.txt
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Tony, Greg, IN line please. On 2023-04-25 21:33, Tony Li wrote: > > Hi Greg, > > Sorry for the delay. > > >> If a transit node needs to find PSD, it can scan the entire label >> stack for the bottom of stack bit. I can’t think of a good reason >> to ever do this, given that it’s a transit node and should be >> payload indifferent. >> >> GIM>> I got confused. I am too not seeing the case when an LSR starts >> looking for PSD unless it has found a proper NAS. > > > I’m told that some legacy transit nodes choose to look at the payload to > extract ECMP. A legacy implementation that does this and finds any MNA > PSD is going to be mightily confused and would never see MNA ISD. An > MNA specific nibble here would be helpful in ensuring that it realizes > that it’s about to make a mistake. > > >> > - we will only include the MNA first nibble if there is an MPLS >> Label in the packet. right? Existing (legacy) non-MMA capable >> implementations will not recognize the MNA first nibble as "MNA >> follows, only understand that this is something unrecognised. What >> does legacy implementations do with unrecognized first nibbles today? >> >> >> There is not much point in having an MNA first nibble unless there >> is also MNA PSD. And there is not much point in MNA PSD unless >> there is a label stack involved. Therefore, yes, there should be a >> label in the label stack. >> >> GIM>> More confusion in my head. Why it must be "an MNA first nibble" >> but not any non-IPv4 and non-IPv6? > > > Just for clear semantics. I am a very big fan of avoiding overloading. I agree with Tony that simple is good. However, Ethernet PWs without a control word made it "un-simple"! An Ethernet PW without a control word cab put any value in the first nibble. The consequence is e.g. MNA PSD can not rely on the first nibble only to identify MNA PSD. The P flag in the LSE following the MNA will uniquely identify MNA PSD. Now there are two possibilities 1. we assign a MNA PSD first nibble - if we do so an MNA PSD capable node cannot rely solely on that first nibble to positively identify MNA PSD - a node that are looking at the first nibble to decide if it can do load balancing does not need to understand the MNA label or the P flag, it can look at the first nibble to decide that it should not do load balancing, the first nibble will be other than 4 or 6. 2. we do not assign a a MNA PSD first nibble - if we do so an MNA PSD capable node will rely only on the P flag to identify MNA PSD, we can mandate that a node sending MNA PSD shall put a specific value (other than 4 or 6) in the first nibble (zero comes to mind). We can further mandate an MNA PSD capable node shall ignore the first nibble. - a node that are looking at the first nibble to decide if it can do load balancing does not need to understand the MNA label or the P flag, it can look at the first nibble to decide that it should not do load balancing, the first nibble will be other than 4 or 6. I think we need to decide which method we use. It should be described in detailed in the first nibble draft. Any solution that assign a first nibble or mandate that the first nibble is ignored, should reference that text in the first nibble draft. /Loa PS I'm a bit concerned using the option 1. since the first nibble values is a scarce resource. > > Tony > > > > _______________________________________________ > detnet mailing list > detnet@ietf.org > https://www.ietf.org/mailman/listinfo/detnet -- Loa Andersson email: loa@pi.nu Senior MPLS Expert loa.pi.nu@gmail.com Bronze Dragon Consulting phone: +46 739 81 21 64
- [mpls] FW: New Version Notification for draft-jag… Jaganbabu Rajamanickam (jrajaman)
- Re: [mpls] FW: New Version Notification for draft… Loa Andersson
- Re: [mpls] FW: New Version Notification for draft… Joel Halpern
- Re: [mpls] FW: New Version Notification for draft… Rakesh Gandhi (rgandhi)
- Re: [mpls] FW: New Version Notification for draft… Joel Halpern
- Re: [mpls] FW: New Version Notification for draft… Rakesh Gandhi
- Re: [mpls] FW: New Version Notification for draft… Greg Mirsky
- Re: [mpls] FW: New Version Notification for draft… Joel Halpern
- Re: [mpls] FW: New Version Notification for draft… Rakesh Gandhi
- Re: [mpls] FW: New Version Notification for draft… Rakesh Gandhi
- Re: [mpls] FW: New Version Notification for draft… Greg Mirsky
- Re: [mpls] FW: New Version Notification for draft… Rakesh Gandhi
- Re: [mpls] FW: New Version Notification for draft… Greg Mirsky
- Re: [mpls] FW: New Version Notification for draft… Rakesh Gandhi
- Re: [mpls] FW: New Version Notification for draft… Greg Mirsky
- Re: [mpls] FW: New Version Notification for draft… Rakesh Gandhi
- Re: [mpls] FW: New Version Notification for draft… Tianran Zhou
- Re: [mpls] [Detnet] FW: New Version Notification … Greg Mirsky
- Re: [mpls] FW: New Version Notification for draft… Greg Mirsky
- Re: [mpls] FW: New Version Notification for draft… Rakesh Gandhi
- Re: [mpls] [Pals] FW: New Version Notification fo… Loa Andersson
- Re: [mpls] [Pals] FW: New Version Notification fo… Rakesh Gandhi
- Re: [mpls] [Pals] FW: New Version Notification fo… Loa Andersson
- Re: [mpls] [Pals] FW: New Version Notification fo… Tony Li
- Re: [mpls] [Detnet] [Pals] FW: New Version Notifi… Greg Mirsky
- Re: [mpls] [Detnet] [Pals] FW: New Version Notifi… John E Drake
- Re: [mpls] [Detnet] [Pals] FW: New Version Notifi… Greg Mirsky
- Re: [mpls] [Detnet] [Pals] FW: New Version Notifi… John E Drake
- Re: [mpls] [Detnet] [Pals] FW: New Version Notifi… Greg Mirsky
- Re: [mpls] [Pals] FW: New Version Notification fo… Loa Andersson
- Re: [mpls] [Pals] FW: New Version Notification fo… Greg Mirsky
- Re: [mpls] [Pals] FW: New Version Notification fo… Loa Andersson
- Re: [mpls] [Pals] FW: New Version Notification fo… Tony Li
- Re: [mpls] [Pals] FW: New Version Notification fo… Greg Mirsky
- Re: [mpls] [Pals] FW: New Version Notification fo… Tony Li
- Re: [mpls] [Pals] FW: New Version Notification fo… Greg Mirsky
- Re: [mpls] [Pals] FW: New Version Notification fo… Tony Li
- Re: [mpls] [Detnet] [Pals] FW: New Version Notifi… Loa Andersson