Re: [sfc] New Version Notification for draft-vandevelde-sfc-nsh-length-overload-00.txt

Dear Ron,

   Unitl now, there proposed 3 use cases for SFC, including Data center, 
Mobility and Broadband use case. Different use case use different metadata 
allocation.
If there is no other use case, 2 bits may be enough to distinguish 3 use 
cases. Otherwise, 2 bits would be not adequate.

   After long discussion about the NSH draft, I think it may be much more 
difficult to grow the fixed 16 bytes, but it also proposes a new approach 
to admit this issue.
Unitl now, 5 approaches have been proposed:

   1. from Ron: grow the fixed 16 bytes
   2. from Gunter:  overload NSH length field
   3. from Dave:  using MD type field, such as value 3,4,5..
   4. from Med:  reckon to use MD Type=2
   5. from Linda: let original MD Type field make 2 bits room for this 
purpose

   If it is possible, maybe someone can request a slot to discussion this 
issue during the upcoming meeting to achieve a consensus? 

BRs,
Linda Wang

Ron Parker <Ron_Parker@affirmednetworks.com> 
2016/10/25 21:32

收件人
"wang.cui1@zte.com.cn" <wang.cui1@zte.com.cn>, "Joel M. Halpern" 
<jmh@joelhalpern.com>, "Van De Velde, Gunter (Nokia - BE)" 
<gunter.van_de_velde@nokia.com>, 
抄送
sfc <sfc-bounces@ietf.org>, "sfc@ietf.org" <sfc@ietf.org>, Dave Dolson 
<ddolson@sandvine.com>
主题
RE: [sfc] New Version Notification for 
draft-vandevelde-sfc-nsh-length-overload-00.txt

Linda,

If we do, indeed, set the MD-1 encoding schema ID into the NSH, itself, it 
doesn’t seem like 2 bits would be adequate.

Perhaps the fixed 16 bytes should grow to include a prepend byte(s) that 
identifies the encoding schema.

   Ron

From: sfc [mailto:sfc-bounces@ietf.org] On Behalf Of wang.cui1@zte.com.cn
Sent: Monday, October 24, 2016 10:37 PM
To: Joel M. Halpern <jmh@joelhalpern.com>; Van De Velde, Gunter (Nokia - 
BE) <gunter.van_de_velde@nokia.com>
Cc: sfc <sfc-bounces@ietf.org>; sfc@ietf.org; Ron Parker 
<Ron_Parker@affirmednetworks.com>; Dave Dolson <ddolson@sandvine.com>
Subject: Re: [sfc] New Version Notification for 
draft-vandevelde-sfc-nsh-length-overload-00.txt

Dear all, 

   In fact, there is also another solution to address this problem 
proposed in a previous draft 
https://tools.ietf.org/html/draft-wang-sfc-md-type-issues-02. 
It also proposed to add some bits in NSH, such as reserving 2 bits in the 
MD-Type field, to identify the exact meaning of the Mandatory Context 
Headers. 
This solution don't bother the length field as well as the MD-type=1/2. 
But is requires the original MD Type field to make 2 bits room for this 
purpose. 

   On the other hand, I do agree that, both 
draft-wang-sfc-md-type-issues-02 and draft-vandevelds-sfc-nsh-overload try 
to propose the issue, we may agree/disagree 
on the different approaches, but there should find a agreeable solution 
for how to understand the exact meaning in the Mandatory Context Headers 
fields in mixed scenarios. 

BRs, 
Linda Wang 

"sfc" <sfc-bounces@ietf.org> 写于 2016/10/18 10:10:35:

> "Joel M. Halpern" <jmh@joelhalpern.com> 
> 发件人:  "sfc" <sfc-bounces@ietf.org>
> 
> 2016/10/18 10:10 
> 
> 收件人 
> 
> Dave Dolson <ddolson@sandvine.com>, Ron Parker 
> <Ron_Parker@affirmednetworks.com>, "Van De Velde, Gunter (Nokia - 
> BE)" <gunter.van_de_velde@nokia.com>, "sfc@ietf.org" <sfc@ietf.org>, 
> 
> 抄送 
> 
> 主题 
> 
> Re: [sfc] New Version Notification for draft-vandevelde-sfc-nsh-
> length-overload-00.txt 
> 
> I agree with Dave.  The length field should always mean length.
> One of the strong benefits of this is that if there is a need (for 
> logging, analysis, ...) to get to the data packet but not to understand 
> the metadata, the length field always just works.  This significantly 
> simplifies many code paths.
> 
> Yours,
> Joel
> 
> On 10/17/16 12:10 PM, Dave Dolson wrote:
> >
> > I would prefer to see the length field always mean length, so that
> implementations not requiring metadata can just skip the metadata 
> regardless of MD type.
> >
> > At the risk of stating the obvious, there already is an MD type 
> field that can be used to discriminate metadata allocations. Values 
> 3,4,5,... are available for different MD encodings.
> >
> > -Dave
> >
> > ________________________________________
> > From: sfc [sfc-bounces@ietf.org] on behalf of Ron Parker 
> [Ron_Parker@affirmednetworks.com]
> > Sent: Monday, October 17, 2016 10:50 AM
> > To: Van De Velde, Gunter (Nokia - BE); sfc@ietf.org
> > Subject: Re: [sfc] New Version Notification for draft-vandevelde-
> sfc-nsh-length-overload-00.txt
> >
> > Gunter,
> >
> > I strongly support this proposal.   It brings more specificity to 
> Type 1 which will undoubtedly improve interworking between different
> implementations and between different administrative domains.
> >
> >    Ron
> >
> >
> > -----Original Message-----
> > From: sfc [mailto:sfc-bounces@ietf.org] On Behalf Of Van De Velde,
> Gunter (Nokia - BE)
> > Sent: Monday, October 17, 2016 5:15 AM
> > To: sfc@ietf.org
> > Subject: [GRAYMAIL] [sfc] FW: New Version Notification for draft-
> vandevelde-sfc-nsh-length-overload-00.txt
> >
> > Short text about overloading NSH length field for NSH MD Type-1 as
> context allocation type, including proposal for backward compatibility.
> >
> > G/
> >
> > ------
> >
> > On 17/10/2016, 10:05, "internet-drafts@ietf.org" <internet-
> drafts@ietf.org> wrote:
> >
> >
> >     A new version of I-D, 
draft-vandevelde-sfc-nsh-length-overload-00.txt
> >     has been successfully submitted by Gunter Van de Velde and posted 
to the
> >     IETF repository.
> >
> >     Name:               draft-vandevelde-sfc-nsh-length-overload
> >     Revision:   00
> >     Title:              Network Services Header Context 
AllocationIdentifier
> >     Document date:      2016-10-17
> >     Group:              Individual Submission
> >     Pages:              5
> >     URL:            https://www.ietf.org/internet-drafts/draft-
> vandevelde-sfc-nsh-length-overload-00.txt
> >     Status:         https://datatracker.ietf.org/doc/draft-
> vandevelde-sfc-nsh-length-overload/
> >     Htmlized:       https://tools.ietf.org/html/draft-vandevelde-
> sfc-nsh-length-overload-00
> >
> >
> >     Abstract:
> >        The specification of the NSH MD Type 1 header 
[draft-ietf-sfc-nsh]
> >        mandates four Context Headers, 4-byte each, and they MUST be 
added
> >        immediately following the Service Path Header.  As direct
> >        consequence, an NSH MD Type 1 header is always Length 0x6 (six 
4-byte
> >        words).  As a result, the Length field of the NSH MD Type 1 
header
> >        provides an information which is known by simply looking at the 
"MD
> >        Type" field.  However, while [draft-ietf-sfc-nsh] does not 
specify
> >        the encoding of these Context Headers, other specifications 
have
> >        started to do so.  A need to distinguish types of Context 
Headers
> >        therefore arises.
> >
> >        This draft proposes to overload the Length field of an NSH MD 
Type 1
> >        as Meta-Data context allocation identifier and to create a IANA
> >        repository for NSH MD Type 1 allocation schemes.  The NSH MD 
Type 1
> >        Length field overload intends to allow universal understanding 
at any
> >        network location and by any network device of the context 
allocation
> >        structure.
> >
> >
> >
> >
> >
> >     Please note that it may take a couple of minutes from the time
> of submission
> >     until the htmlized version and diff are available at 
tools.ietf.org.
> >
> >     The IETF Secretariat
> >
> >
> >
> > _______________________________________________
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> > sfc@ietf.org
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> >
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> >
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> >
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