Re: [sfc] I-D Action: draft-ietf-sfc-nsh-tlv-02.txt
Greg Mirsky <gregimirsky@gmail.com> Wed, 01 April 2020 23:55 UTC
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From: Greg Mirsky <gregimirsky@gmail.com>
Date: Wed, 01 Apr 2020 16:54:43 -0700
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To: "Carlos Pignataro (cpignata)" <cpignata=40cisco.com@dmarc.ietf.org>
Cc: Med Boucadair <mohamed.boucadair@orange.com>, "wei.yuehua@zte.com.cn" <wei.yuehua@zte.com.cn>, "draft-ietf-sfc-nsh-tlv@ietf.org" <draft-ietf-sfc-nsh-tlv@ietf.org>, "sfc@ietf.org" <sfc@ietf.org>
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Subject: Re: [sfc] I-D Action: draft-ietf-sfc-nsh-tlv-02.txt
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Hi Carlos and Med, thank you for the discussion. Please find my notes in-lined below under GIM>> tag. Regards, Greg On Tue, Mar 31, 2020 at 7:22 AM Carlos Pignataro (cpignata) <cpignata= 40cisco.com@dmarc.ietf.org> wrote: > Hi, Med, > > It is somewhat hard for me to follow the inlined comments. If there’s > something I miss, please let me know. I’ll preface with “[CMP]" > > 2020/03/31 午前10:07、mohamed.boucadair@orange.comのメール: > > Hi Carlos, > > Please see inline. > > Cheers, > Med > > *De :* Carlos Pignataro (cpignata) [mailto:cpignata@cisco.com > <cpignata@cisco.com>] > *Envoyé :* mardi 31 mars 2020 15:23 > *À :* BOUCADAIR Mohamed TGI/OLN > *Cc :* wei.yuehua@zte.com.cn; draft-ietf-sfc-nsh-tlv@ietf.org; > sfc@ietf.org > *Objet :* Re: [sfc] I-D Action: draft-ietf-sfc-nsh-tlv-02.txt > > Hi, Med, > > Really good comments! > > In general, I tend to agree with your second comment, which is a > meta-comment, about adding more descriptive text. That said, I’d cautious > that this document defines foundational data fields and not the usage and > use cases of them. > *[Med] Without being verbose, we need to explain why a TLV is useful/how > it can be used. For example, a reader may ask: how the flow TLV is > populated? Why it is needed if we can access to the inner packet? should > the flow TLV by updated on-path? What if there are address rewriting SFs?* > > > > [CMP] I believe this document should answer the questions on syntax and > definition/meaning, but not the use-case. Saying “Flow id is for marking > packets of the same flow, and it is a 32-bit number” is as far as I think > this should go. > > [CMP] What do others think? > GIM>> I agree with Med, the document should give at least one example of how a TLV can be used. At the same time, future documents may define another scenarios. > > *I may have answers to some of those questions but my point is that we > need to have some of the details in the document (especially, when this is > important for interoperability). * > > > Interoperability has many layers. Syntax and semantics need to be ensured > in this doc. > GIM>> I think that the document should define actionable aspect of a TLV. Just providing format seems insufficient. > > > Based on that, see below. > > > 2020/03/31 午前4:16、mohamed.boucadair@orange.comのメール: > > Hi all, > > Some easy to fix comments: > > · You may consider adding more description to the actual usage of > each TLVs. > > This document defines information elements rather than use cases for them. > As such, I hesitate in adding too much usage which can be containing. That > said, do you have specific thoughts on usage? > *[Med] I do have for some (content type, for example), but not sure about > the others. For example, who sets the tenant-ID? Is it by control or > extracted from the packets? Idem for the policy-ID. * > > > [CMP] To me specific usages are outside scope. Many specifications in the > IETF describe the fields while future companion documents define usage. > This, to me, is one of those. > GIM>> Yes, and there are examples when forward-looking definitions where taken from the document and moved into the document that explains how that object is used. > > > · The TLVs content should also be clarified. For example, “Akin, > but not identical to the usage described in [RFC6437]” does not say what is > the diff vs. 6437 nor why not reusing FL would be sufficient if an IPv6 > transport is used. > > Agreed. I would replace: > > Flow ID provides a representation of the flow. Akin, but not > identical to the usage described in [RFC6437]. > > > With at least > The Flow ID provides a field in the NSH MD Type 2 to label > packets belonging to the same flow. Absence of this field, or > a value of zero denotes that packets have not been labeled. > > > *[Med] That’s a good start. Thanks. The natural questions then are: what > is a label? What to do with a labeled a packet? do we allow to change the > label when progressing in an SFP? We need to think about this further. * > > > [CMP] I did not mean to add a “label” as a noun, but rather label as in > mark or tag. > > [CMP] Immutability is a great question! I tent to think that it could > change, but what do you think? > > > · Clarify whether conveying multiple instances of each TLV is > allowed. > > That is not for this document to say. > *[Med] RFC8300 says the following:* > > If multiple instances of the same metadata are included in an NSH > packet, but the definition of that Context Header does not allow for > ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ > it, the SFC-aware SF MUST process the first instance and ignore > ^^ > subsequent instances. The SFC-aware SF MAY log or increase a counter > for this event. > > Some use cases can restrict to one interface for example, others to > multiple. > > > [CMP] Fair enough. We could add requirements on multiplicity. > GIM>> I agree that the question of multiple occurence of a TLV should be specified for each TLV (or we can have a blanket statement with exceptions though that might add to some confusion). > > > > · What is a “a network-centric forwarding context”? > > Here’s my take on text proposal on various fields (this is full text, not > diff): > *[Med] Thank you for drafting this. I hope I can provide text as well.* > > > [CMP] Of course! That’s a back-of-napkin start only. > > > 4.1. Forwarding Context > > The forwarding context used for segregation and forwarding scope can > Take several forms depending on the network environment. For example, > VXLAN/VXLAN-GPE VNID, VRF identification, and VLAN. This context > header carries this network-based forwarding context. > > 4.2. Tenant Identifier > > Tenant identification is often used for segregation within a multi- > tenant environment. Orchestration system-generated tenant IDs are an > example of such data. This context header carries both the format and > value of the Tenant identifier. > > > 4.3. Content Type > // I believe this needs further thinking on the namespace fo Content > Types, could even be draft-penno-sfc-appid-05 > > 4.4. Ingress Network Information > > This data identifies the ingress network node, and, if required, > ingress interface. > > // this should be split into Node and Ingress Interface. > > 4.4. Ingress Network Node Information > > > This context header identifies the ingress network node. > > > 4.5. Ingress Network Interface Information > > > This context header identifies the ingress network interface. > > > > 4.6. Flow ID > The Flow ID provides a field in the NSH MD Type 2 to label > packets belonging to the same flow. Absence of this field, or > a value of zero denotes that packets have not been labeled. > > > ... > > > · Section 7: Please delete “IANA is requested to create a new > "Network Service Header (NSH) TLV” as we do already have a registry at: > https://www.iana.org/assignments/nsh/nsh.xhtml#optional-variable-length-metadata-types. > You may use this NEW wording: > > This document requests IANA to assign the following types from the > "NSH IETF- Assigned Optional Variable-Length Metadata Types" (0x0000 > IETF Base NSH MD Class) registry available at: > https://www.iana.org/assignments/nsh/nsh.xhtml#optional-variable- > <https://www.iana.org/assignments/nsh/nsh.xhtml#optional-variable-length-metadata-types> > length-metadata-types > <https://www.iana.org/assignments/nsh/nsh.xhtml#optional-variable-length-metadata-types> > . > > Indeed!!! > > And additionally should move the Types to TBAs. > > Thanks, > > Carlos. > > > > Thank you. > > > > [CMP] You are welcome! > > Carlos. > > Cheers, > Med > > *De :* sfc [mailto:sfc-bounces@ietf.org <sfc-bounces@ietf.org>] *De la > part de* wei.yuehua@zte.com.cn > *Envoyé :* lundi 30 mars 2020 09:29 > *À :* cpignata@cisco.com; sfc@ietf.org > *Cc :* draft-ietf-sfc-nsh-tlv@ietf.org; sfc@ietf.org > *Objet :* Re: [sfc] I-D Action: draft-ietf-sfc-nsh-tlv-02.txt > > Dear Carlos, > Thank you for reminding this kind of modifications to the mailing list so > that more people could notice and give comments. > https://tools.ietf.org/rfcdiff?url2=draft-ietf-sfc-nsh-tlv-02.txt > Your suggestion is reasonable. > > Does anyone aware of implementations? > or How do you think of TBAs? > > I appreciate your comments. > > *Best Regards,* > *魏月华 Corona Wei* > M: +86 13851460269 E: wei.yuehua@zte.com.cn > > 原始邮件 > *发件人:*CarlosPignataro(cpignata) <cpignata@cisco.com> > *收件人:*魏月华00019655; > *抄送人:*sfc@ietf.org <sfc@ietf.org>;draft-ietf-sfc-nsh-tlv@ietf.org < > draft-ietf-sfc-nsh-tlv@ietf.org>; > *日* *期* *:*2020年03月28日 21:49 > *主* *题* *:**Re: [sfc] I-D Action: draft-ietf-sfc-nsh-tlv-02.txt* > Dear Wei, > Thanks for the quick responses and accepting the suggestions. > > Only one follow-up on this, which I bring to the top: > > Wei>> Only editorial improvement. > The Types in previous version were: > 0x1, 0x4, 0x6, 0x7, 0x8, 0x9, 0xA, 0xB > The Types in current version are: > 0x01, 0x02, 0x03, 0x04,0x05,0x06,0x07,0x08 > > > I do not believe that changing a protocol value is an editorial change (or > editorial improvement) necessarily. > > Are there implementations following the previous allocations? Unused > values in between might look weird but it is to necessarily unoptimized, > unimproved, or wrong. > > If a goal is to have a gapless increasing list and there are no > implementations, then TBAs can be used and assignment at the end (e.g., if > we split the node/interface into two). > > On the other hand, I’d always prioritize implementations (the entropy of > reality will take care of disorganize the list :-) > > I’d leave them as they were, since there are enough numbers in the space, > or ask on the list for changing and wait. > > Thanks, > > Carlos. > > > > 2020/03/27 午後11:13、wei.yuehua@zte.com.cnのメール: > > Dear Carlos, > I appreciated your comments. > Please see my response in line with Wei>> tag > *Best Regards,* > *魏月华 Corona Wei* > M: +86 13851460269 E: wei.yuehua@zte.com.cn > > > > *发件人:*CarlosPignataro(cpignata) <cpignata=40cisco.com@dmarc.ietf.org> > *收件人:*sfc@ietf.org <sfc@ietf.org>; > *抄送人:*draft-ietf-sfc-nsh-tlv@ietf.org <draft-ietf-sfc-nsh-tlv@ietf.org>; > *日* *期* *:*2020年03月27日 02:36 > *主* *题* *:**Re: [sfc] I-D Action: draft-ietf-sfc-nsh-tlv-02.txt* > > _______________________________________________ > sfc mailing list > sfc@ietf.org > https://www.ietf.org/mailman/listinfo/sfc > Hi, SFC, > > Apologies, a late response to > https://mailarchive.ietf.org/arch/msg/sfc/pNT0kOnFHZeTBLXjuIH0hoKhJs4/ > > Looking at the document I’ve got a few comments, prefaced with “CMP”: > > > 2.1. Terminology > > > CMP: Instead of duplicating definition of terms, why not point to RFC 8300 > and RFC 7665 as needed, and only define new terms. > > Wei>> Will delete duplicated NSH, MD Type and SFC which have been defined > in RFC 8300 and RFC 7665 > > 0 1 2 3 > > 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 > > +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ > > |Ver|O|C|R|R|R|R|R|R| Length | MD Type | Next Protocol | > > +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ > > > > Figure 1: NSH Base Header > > CMP: This is an old version, missing TTLL from RFC 88300 > Wei>> Will modify this figure to align with RFC8300 > > > where > > > > Metadata Class (MD Class): Defines the scope of the Type field to > > provide a hierarchical namespace. > > > > Type - Indicates the explicit type of metadata being carried. The > > value is one from the Network Service Header (NSH) TLV Type > > registry (Section 7). > > > > Unassigned bit: One unassigned bit is available for future use. > > This bit MUST NOT be set, and it MUST be ignored on receipt. > > > > Length: Indicates the length of the variable-length metadata, in > > bytes. In case the metadata length is not an integer number of > > 4-byte words, the sender MUST add pad bytes immediately following > > the last metadata byte to extend the metadata to an integer number > > of 4-byte words. The receiver MUST round the Length field up to > > the nearest 4-byte-word boundary, to locate and process the next > > field in the packet. The receiver MUST access only those bytes in > > the metadata indicated by the Length field (i.e., actual number of > > bytes) and MUST ignore the remaining bytes up to the nearest 4- > > byte-word boundary. The length may be 0 or greater. > > > > A value of 0 denotes a Context Header without a Variable-Length > > Metadata field. > > > CMP: Instead of copy/paste repeating this from RFC 8300, please add a > pointer. Copy/past text gets desynchronized easily. > Wei>> wil delete this part. > > > 4.2. Tenant Identifier > > > > Tenant identification is often used for segregation within a multi- > > tenant environment. Orchestration system-generated tenant IDs are an > > example of such data. > > > > 0 1 2 3 > > 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 > > +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ > > | Metadata Class = 0x0000 | Type = 0x02 |U| Length=12 | > > > CMP: Seems like this Type, as well as others, were changed from the > previous version. Why? > Wei>> Only editorial improvement. > The Types in previous version were: > 0x1, 0x4, 0x6, 0x7, 0x8, 0x9, 0xA, 0xB > The Types in current version are: > 0x01, 0x02, 0x03, 0x04,0x05,0x06,0x07,0x08 > > > 7. IANA Considerations > > > CMP: This needs registration: Metadata Class = 0x0000 > > CMP: Also, the Context Type (CT) needs registration. > > CMP: And these as well: > * Tenant Type (TT) > * Group Type (GT) > * URI Type > Wei>> Will follow your advice. > > Thanks! > > Carlos. > > > _______________________________________________ > sfc mailing list > sfc@ietf.org > https://www.ietf.org/mailman/listinfo/sfc > > > > _______________________________________________ > sfc mailing list > sfc@ietf.org > https://www.ietf.org/mailman/listinfo/sfc >
- [sfc] I-D Action: draft-ietf-sfc-nsh-tlv-02.txt internet-drafts
- Re: [sfc] I-D Action: draft-ietf-sfc-nsh-tlv-02.t… wei.yuehua
- Re: [sfc] I-D Action: draft-ietf-sfc-nsh-tlv-02.t… Carlos Pignataro (cpignata)
- Re: [sfc] I-D Action: draft-ietf-sfc-nsh-tlv-02.t… wei.yuehua
- Re: [sfc] I-D Action: draft-ietf-sfc-nsh-tlv-02.t… Carlos Pignataro (cpignata)
- Re: [sfc] I-D Action: draft-ietf-sfc-nsh-tlv-02.t… wei.yuehua
- Re: [sfc] I-D Action: draft-ietf-sfc-nsh-tlv-02.t… mohamed.boucadair
- Re: [sfc] I-D Action: draft-ietf-sfc-nsh-tlv-02.t… Carlos Pignataro (cpignata)
- Re: [sfc] I-D Action: draft-ietf-sfc-nsh-tlv-02.t… mohamed.boucadair
- Re: [sfc] I-D Action: draft-ietf-sfc-nsh-tlv-02.t… Carlos Pignataro (cpignata)
- Re: [sfc] I-D Action: draft-ietf-sfc-nsh-tlv-02.t… Greg Mirsky