Re: [mpls] The first nibble issue associated with MPLS encapsulation
Greg Mirsky <gregimirsky@gmail.com> Fri, 08 April 2016 23:05 UTC
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Date: Fri, 08 Apr 2016 16:05:51 -0700
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From: Greg Mirsky <gregimirsky@gmail.com>
To: "Carlos Pignataro (cpignata)" <cpignata@cisco.com>
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Cc: "mpls@ietf.org" <mpls@ietf.org>, "bier@ietf.org" <bier@ietf.org>, sfc@ietf.org, "Dr. Tony Przygienda" <tonysietf@gmail.com>
Subject: Re: [mpls] The first nibble issue associated with MPLS encapsulation
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Hi Carlos, thank you for the clarification. Should we think about establishing the registry than? Regards, Greg On Apr 8, 2016 5:38 PM, "Carlos Pignataro (cpignata)" <cpignata@cisco.com> wrote: > Greg, > > My point, sorry if I was not clear, was that there is no such a thing as a > ‘first nibble registry’. > > Instead, RFC 4928, Section 5, at > https://tools.ietf.org/html/rfc4928#section-5, says: > > IANA has marked the value 0x1 in the IP protocol version number space > as "Reserved" and placed a reference to this document to both values > 0x0 and 0x1. > > And that is reflected as > http://www.iana.org/assignments/version-numbers/version-numbers.xhtml#version-numbers-1 > > > The IANA text in 4928 is additionally followed by a disclaimer: > > Note that this document does not in any way change the policies > regarding the allocation of version numbers, including the possible > use of the reserved numbers for some future purpose. > > Further, RFC 4385 does not specify the ‘first nibble’ as a field. Instead, > it depicts the actual binary values for the different CW formats. In other > words, it takes the values from the IP protocol version number and not as a > new CW Field. > > Thanks, > > — Carlos. > > PS: Sasha, quick typo, s/1119/1190/; > > From: Greg Mirsky <gregimirsky@gmail.com> > Date: Friday, April 8, 2016 at 7:28 PM > To: Alexander Vainshtein <Alexander.Vainshtein@ecitele.com> > Cc: "sfc@ietf.org" <sfc@ietf.org>, "bier@ietf.org" <bier@ietf.org>, "Dr. > Tony Przygienda" <tonysietf@gmail.com>, "mpls@ietf.org" <mpls@ietf.org>, > Xiaohu Xu <xuxiaohu@huawei.com>, Carlos Pignataro <cpignata@cisco.com> > Subject: Re: [mpls] The first nibble issue associated with MPLS > encapsulation > > Hi Sasha, > thank you for pointing to existing IANA allocation, though stale. I wonder > if there is the registry for the first nibble. We, Tony and I, had > discussed the way the first nibble space managed. If there already is the > registry, could you please point me to it. > Regards, Greg > On Apr 8, 2016 2:31 PM, "Alexander Vainshtein" < > Alexander.Vainshtein@ecitele.com> wrote: > >> Carlos and all, >> Just for the reference, IANA has defined version 5 (0101) has assigned to ST protocol and refers to RFC 1119. The latter has been obsoleted by RFC 1819, but the IANA >> assignment still holds. >> >> Is there, just in case, any relationship between BIER and ST? >> Thumb typed on my cellphone >> Regards, >> Sasha >> >> -------- Original Message -------- >> From: "Carlos Pignataro (cpignata)" <cpignata@cisco.com> >> Date: Fri, April 08, 2016 9:25 PM +0300 >> To: Xiaohu Xu <xuxiaohu@huawei.com> >> CC: mpls@ietf.org, bier@ietf.org, sfc@ietf.org, "Dr. Tony Przygienda" <tonysietf@gmail.com> >> Subject: Re: [mpls] The first nibble issue associated with MPLS encapsulation >> >> >> Xiaohu, Tony, >> >> Please see inline. >> >> On Apr 7, 2016, at 2:39 PM, Xuxiaohu <xuxiaohu@huawei.com> wrote: >> >> As for the first nibble issue, will it violate the layering principle of >> network protocol stacks if the first nibble of any new encapsulation header >> (which could be an MPLS payload) is used as the "MPLS payload type" field? >> >> >> Reading draft-wang-bier-ethernet-01, Section 3, the “first nibble” is >> _not_ used as an “MPLS payload type”. Instead, the text describes an >> anti-aliasing mechanism, much like RFC 4928. >> >> The relevant text is: >> First nibble: The first 4 bits of the header are set to 0101; this >> ensures that the BIER header will not be confused with an IP header >> or with the header of a pseudowire packet. >> >> Which says “… will not be confused with …" >> >> wouldn't it be more reasonable and sustainable to fix the problem (i.e., >> the lack of a protocol field in the MPLS header) by the MPLS header itself? >> >> >> >> >> Who says it is a *problem*? There’s no “fixing” needed. >> >> By the way, since it's claimed that the NSH is transport-independant, it >> means the NSH should be able to be transported over MPLS. However, it seems >> that the first nibble issue has not be considered in the current NSH draft. >> As a result, when encapsulating NSH over MPLS, the NSH may be >> mis-interpreted as IP header. >> >> >> >> >> There seems to be some massive confusion on this paragraph, on a number >> of levels. First, NSH is not “claimed to be” transport-independent. It is >> by charter and by design. Second, the NSH draft does not even include the >> term “MPLS”, because it does not define transports. The SFC Encapsulation >> can be used in a transport-agnostic way. >> >> One more comment below. >> >> Best regards, >> Xiaohu >> >> >> ------------------------------ >> *发件人:* BIER [bier-bounces@ietf.org] 代表 Tony Przygienda [ >> tonysietf@gmail.com] >> *发送时间:* 2016年4月5日 22:36 >> *收件人:* bier@ietf.org >> *主题:* [Bier] comments on draft-wang-bier-ethernet-01 >> >> after reading >> >> a) first nibble: refer to MPLS encaps as "the same value" to keep in sync >> >> >> One comment regarding the “First nibble” text >> at draft-ietf-bier-mpls-encapsulation-03 >> >> Since the function of the first nibble is to prevent aliasing with an IP >> packet, in order for RFC 4928 to specify values of 0x0 and 0x1 for the >> First Nibble, it had to “Reserve” IP protocol versions of 0 and 1, >> referencing that RFC (see https://tools.ietf.org/html/rfc4928#section-5). >> >> Is the intent to re-assign IPv5 at >> http://www.iana.org/assignments/version-numbers/ ? >> >> Note that RFC 4928 says “REQUIRED” at: >> >> It is REQUIRED, however, that applications depend upon in-order >> packet delivery restrict the first nibble values to 0x0 and 0x1. >> >> Thanks, >> >> — Carlos. >> >> >> b) refer to all other possible fields to MPLS encaps to keep in sync when >> describing instead of repeating >> c) you need to describe which kind of ether MACs are allowed, especially >> on broadcast media, i.e. is it always p2p or can you take advantage of the >> broadcast ? >> d) Figure 4: use the architecture/MPLS encoding for the length, don't >> invent a new one >> e) who will obtain a new ether type from IEEE? As far I understand, not a >> trivial process albeit we have several liaisons with IEEE >> >> -- >> *We’ve heard that a million monkeys at a million keyboards could produce >> the complete works of Shakespeare; now, thanks to the Internet, we know >> that is not true.* >> —Robert Wilensky >> _______________________________________________ >> mpls mailing list >> mpls@ietf.org >> https://www.ietf.org/mailman/listinfo/mpls >> >> >> >> _______________________________________________ >> mpls mailing list >> mpls@ietf.org >> https://www.ietf.org/mailman/listinfo/mpls >> >>
- [mpls] The first nibble issue associated with MPL… Xuxiaohu
- Re: [mpls] The first nibble issue associated with… Carlos Pignataro (cpignata)
- Re: [mpls] The first nibble issue associated with… Alexander Vainshtein
- Re: [mpls] The first nibble issue associated with… Greg Mirsky
- Re: [mpls] The first nibble issue associated with… Carlos Pignataro (cpignata)
- Re: [mpls] The first nibble issue associated with… Greg Mirsky
- Re: [mpls] The first nibble issue associated with… Tony Przygienda
- Re: [mpls] The first nibble issue associated with… Alexander Vainshtein
- Re: [mpls] [sfc] The first nibble issue associate… Eric C Rosen
- Re: [mpls] [sfc] The first nibble issue associate… Carlos Pignataro (cpignata)
- Re: [mpls] The first nibble issue associated with… Xuxiaohu
- Re: [mpls] [sfc] The first nibble issue associate… t.petch
- Re: [mpls] [sfc] The first nibble issue associate… Loa Andersson
- Re: [mpls] [sfc] The first nibble issue associate… Alexander Vainshtein
- Re: [mpls] [sfc] The first nibble issue associate… Loa Andersson
- Re: [mpls] [bier] The first nibble issue associat… Eric C Rosen
- Re: [mpls] [sfc] The first nibble issue associate… t.petch
- Re: [mpls] [bier] The first nibble issue associat… Xuxiaohu
- Re: [mpls] [sfc] The first nibble issue associate… Stewart Bryant
- Re: [mpls] [sfc] The first nibble issue associate… Alexander Vainshtein
- Re: [mpls] [sfc] The first nibble issue associate… Loa Andersson
- Re: [mpls] [bier] The first nibble issue associat… Carlos Pignataro (cpignata)
- Re: [mpls] [bier] The first nibble issue associat… Eric C Rosen
- Re: [mpls] [bier] The first nibble issue associat… Alexander Vainshtein
- Re: [mpls] [bier] The first nibble issue associat… Nagendra Kumar Nainar (naikumar)
- Re: [mpls] [Bier] [bier] The first nibble issue a… Loa Andersson
- Re: [mpls] [sfc] The first nibble issue associate… Stewart Bryant
- Re: [mpls] [bier] The first nibble issue associat… Stewart Bryant
- Re: [mpls] [bier] The first nibble issue associat… Stewart Bryant
- Re: [mpls] [Bier] [bier] The first nibble issue a… Stewart Bryant
- Re: [mpls] [bier] The first nibble issue associat… Gregory Mirsky
- Re: [mpls] [bier] The first nibble issue associat… Eric C Rosen
- Re: [mpls] [Bier] [bier] The first nibble issue a… Gregory Mirsky
- Re: [mpls] [Bier] [bier] The first nibble issue a… Loa Andersson
- Re: [mpls] [Bier] [bier] The first nibble issue a… Loa Andersson
- Re: [mpls] [Bier] [bier] The first nibble issue a… Gregory Mirsky
- Re: [mpls] [Bier] [bier] The first nibble issue a… Loa Andersson