Re: [mpls] [sfc] The first nibble issue associated with MPLS encapsulation
Stewart Bryant <stewart.bryant@gmail.com> Thu, 14 April 2016 18:06 UTC
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To: Loa Andersson <loa@pi.nu>, Alexander Vainshtein <Alexander.Vainshtein@ecitele.com>
References: <1FEE3F8F5CCDE64C9A8E8F4AD27C19EE0D53871C@NKGEML515-MBX.china.huawei.com> <B664DB14-0A8C-4437-83E3-F9DA6C0DDA61@cisco.com> <mc51yrrf9n0wxbjsrprt9amf.1460143890063@email.android.com> <CA+RyBmXpZ-Kt77TW-=_kPYmahdw_yUHB5xhy8YtYVq2OcRJxbA@mail.gmail.com> <D32DB725.3F57B%cpignata@cisco.com> <CA+RyBmW+qonpScnLOfsGorayCvsS0vrFcn+o5nPvOqCOv9Jc3g@mail.gmail.com> <AM3PR03MB0775C55E5AD3247F373007139D940@AM3PR03MB0775.eurprd03.prod.outlook.com> <570BB266.8090608@juniper.net> <570F6374.6030406@gmail.com> <DB3PR03MB0780B7CE7B96283FB484C2489D970@DB3PR03MB0780.eurprd03.prod.outlook.com> <570F79AB.9070107@pi.nu>
From: Stewart Bryant <stewart.bryant@gmail.com>
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Date: Thu, 14 Apr 2016 19:06:10 +0100
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Cc: "mpls@ietf.org" <mpls@ietf.org>, "bier@ietf.org" <bier@ietf.org>, "Dr. Tony Przygienda" <tonysietf@gmail.com>
Subject: Re: [mpls] [sfc] The first nibble issue associated with MPLS encapsulation
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On 14/04/2016 12:06, Loa Andersson wrote: > Sasha and Stewart, > > > On 2016-04-14 18:06, Alexander Vainshtein wrote: >> Stewart and all, >> I concur with Stewart that there is a strong case for 0 in the first >> nibble for all non-IP flows. > > While I can live with 0x0000, 0x0010 or 0x0101, RFC 4928 actually says: > > It is REQUIRED, however, that applications depend upon in-order > packet delivery restrict the first nibble values to 0x0 and 0x1. > > If that is what we want for bier, there is a case to use 0x0 or 0x1 for > bier- 0x1 is of course the OAM identifier, i.e. the GACH indicator, which BIER is also free to use with appropriate channel type. Stewart > > /Loa >> >> As for the need for sub-typing: >> AFAIK quite a few implementations (including some HW-based packet >> processors) treat 0 in the first nibble after the label stack as an >> indication of an Ethernet PW. >> >> Some of them go as far as to hash on the assumed L2 headers for ECMP. >> This causes serious problems, e.g., with the TDM PWs that could be >> reordered if handled by such packet processors in transit LSRs. >> >> This makes quite a case for sub-typing IMO regardless of BIER. >> At the same time, it seems that all the bits in CW structure are used >> - at least for some PW types in some cases. >> >> Regards, >> Sasha >> >> Office: +972-39266302 >> Cell: +972-549266302 >> Email: Alexander.Vainshtein@ecitele.com >> >> -----Original Message----- >> From: Stewart Bryant [mailto:stewart.bryant@gmail.com] >> Sent: Thursday, April 14, 2016 12:32 PM >> To: Eric C Rosen; Alexander Vainshtein; Greg Mirsky >> Cc: mpls@ietf.org; bier@ietf.org; Dr. Tony Przygienda >> Subject: Re: [mpls] [sfc] The first nibble issue associated with MPLS >> encapsulation >> >> I am not sure zero is PW so much as "type undefined - don't ECMP". >> That was certainly the definition that we were talking about at the >> time. >> >> The nibble value is recorded in the IP types registry and any wish >> to take another value really needs to be discussed with the INT area. >> >> Also the code space is so small that we really need to be super >> conservative in its allocation. Given it's true purpose, I suggest >> that we only have the unused deprecated values of 0 (taken), 1 >> (taken), 2, 3 and possibly 5 available for use (for ever). >> Seven and up really should be kept available to the IP protocol itself. >> >> Five of course was deployed. It was used for some form of streaming >> protocol, but it is probably safe to assume that it is no longer in >> the wild. >> >> Whilst Eric makes a case for 5, I think there is also a strong case >> for zero. >> >> If there is a need for subtyping zero for wireshark etc, we could >> take a look at what the use is made of the second nibble in PWs and >> see if there is a set of values never in practise used and thus >> available for subtyping. >> >> - Stewart >> >> >> On 11/04/2016 15:19, Eric C Rosen wrote: >>> (Removed sfc from the cc-list, this seems out of scope for that WG.) >>> >>> In designing the BIER header, the BIER WG is free to mandate any value >>> it chooses in the first nibble. These values do not come from a >>> "first nibble" registry. >>> >>> It seems prudent to put a value like 5 for the following reasons: >>> >>> - If a BIER packet is being parsed by an off-line tool, this is a good >>> hint (though just a hint) that the packet is actually a BIER packet; >>> >>> - If a BIER packet is traveling through an MPLS tunnel, and it >>> traverses a node that does its MPLS load splitting by guessing at the >>> type of the payload, then this is a good hint that the MPLS payload >>> is not IPv4, IPv6, or PW. >>> >>> This strategy does incur a risk. Suppose IPv5 gets designed, >>> implemented, and deployed, and folks start to deploy hardware that >>> does MPLS load balancing by inspecting the IPv5 headers of the MPLS >>> payloads. If a BIER packet is traversing an MPLS tunnel, >>> inappropriate load splitting may occur if the hardware thinks the >>> payload is IPv5 rather than BIER. >>> >>> This particular risk doesn't seem very significant to me. >>> >>> Thus I don't think there's anything here that needs fixing. >>> >>> >>> _______________________________________________ >>> 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