Re: [CCAMP] WG Last Call comments on draft-ietf-ccamp-gmpls-signaling-g709v3-04

Lou Berger <lberger@labn.net> Tue, 22 January 2013 18:11 UTC

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Date: Tue, 22 Jan 2013 13:11:15 -0500
From: Lou Berger <lberger@labn.net>
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To: Fatai Zhang <zhangfatai@huawei.com>
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Cc: CCAMP <ccamp@ietf.org>, "draft-ietf-ccamp-gmpls-signaling-g709v3@tools.ietf.org" <draft-ietf-ccamp-gmpls-signaling-g709v3@tools.ietf.org>
Subject: Re: [CCAMP] WG Last Call comments on draft-ietf-ccamp-gmpls-signaling-g709v3-04
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Fatai,

On 1/20/2013 9:43 PM, Fatai Zhang wrote:
> Hi Lou,
> 
> You said:
>> but you're says encoded as (N*Nominal Rate) right? Wat's the value of this vs just carrying N?
> 
> [Fatai] The original way (in version 04&05) is putting (N* Nominal
> Rate) in "Bit_Rate" field for ODUflex(GFP), the value is that we can
> generalize to just use one single "Bit_Rate" field to carry IEEE
> float number for both cases, it seems that you don't agree on this
> value, :-)

I've seen differences in calculated floating point values from different
implementations, so I just want to ensure that such cases are avoided.
I'm open to specific solutions and certainly will deffer on the
specifics assuming there is no opportunity for misinterpretation/interop
issues. I don't think the original passed this threshold, i.e.,:

         N = Ceiling of

   ODUflex(CBR) nominal bit rate * (1 + ODUflex(CBR) bit rate tolerance)
   ---------------------------------------------------------------------
       ODTUk.ts nominal bit rate * (1 - HO OPUk bit rate tolerance)

> . Therefore, I (was) am saying that I am going to accept
> your suggestion to carry N for ODUflex(GFP). We are discussing where
> to put N for ODUflex(GFP).
> 

> You said:
>> bits in the control plane are generally cheap, IMO it's better to have simpler encoding than to optimize every bit (or 8 in this case).
> 
> [Fatai] OK, I will add a new field (to occupy the reserved bits) to carry N.

As you see fit.

Just to clarify my understanding, ODUflex and Virtual concatenation can
never be combined for the same signal type/level, right? (Although an
ODUflex client signal could be carried over a virtual concatenated
ODUk).  Is this correct or did I miss something in G709?

Thanks,
Lou

> 
> 
> 
> Best Regards
> 
> Fatai
> 
> -----Original Message-----
> From: Lou Berger [mailto:lberger@labn.net] 
> Sent: Friday, January 18, 2013 1:42 AM
> To: Fatai Zhang
> Cc: CCAMP; draft-ietf-ccamp-gmpls-signaling-g709v3@tools.ietf.org
> Subject: Re: [CCAMP] WG Last Call comments on draft-ietf-ccamp-gmpls-signaling-g709v3-04
> 
> 
> 
> On 1/15/2013 10:16 PM, Fatai Zhang wrote:
>> Hi Lou,
>>
>> To avoid misunderstanding, I would like to clarify more on the
>> following point.
>>
>>
>>>>>> It is better to have consistent format and the same meaning of one
> field for both ODUflex(CBR) and GFP. This is why we have section 5.1
> &5.2 to describe the complex stuff.
>>>>> I actually wasn't suggesting that N be carried in the bit rate field.
>>>>> The bit rate field can either be set as described or to zero (i.e.,
>>>>> ignored).  At the time, I was thinking about carrying N in the reserved
>>>>> field. But perhaps the right place is MT, if my understanding is right
>>>>> (would always be 1 otherwise). I'm open to either...
>>>>>
>>>> [Fatai] Why not just use "bit rate"field to carry "N"because "N"
>>>> implies bit rate?  I am OK if you like to use a new filed (like "TS
>>>> Number") to occupy the reserved field even though that I prefer the
>>>> original approach (ie., use "bit rate"field to carry "N").
>>>
>>> Are you proposing dropping carrying bit rates represented as an IEEE
>>> floating point and just carrying N for ODUflex? This seems workable to
>>> me, but we should ensure that there are no significant objections.
>>
>> [Fatai] There are two usages for " Bit_Rate " field as described in the
>> lines 287-310.
>>
>> (1)    For ODUflex(CBR), the Bit_Rate field indicates the nominal bit
>> rate of ODUflex(CBR) expressed in bytes per second, encoded as a 32-bit
>> IEEE single precision floating-point number. For this case, we MUST use
>> 32-bit IEEE floating point instead of "N"(Please see more in section 5.1).
> 
> I guess you really still need (to be based on) the client signal rate at
> the edges.
> 
>>
>> (2)    For ODUflex(GFP), we can change the text (the lines from 305 to
>> 310) based on your suggestion, ie., the Bit_Rate field is used to carry
>> "N"to indicate the nominal bit rate of the
>> ODUflex(GFP).
> 
> but you're says encoded as (N*Nominal Rate) right?  Wat's the value of
> this vs just carrying N?
> 
> 
>>
>> Therefore, I am proposing using one single filed ("Bit_Rate ") for these
>> two cases, in this way, we can leave the "Reserved" bits for future.
> 
> bits in the control plane are generally cheap, IMO it's better to have
> simpler encoding than to optimize every bit (or 8 in this case).
> 
> Lou
> 
>>
>> Hope we are now at the same page.
>>
>>
>> Best Regards
>>
>> Fatai
> 
> 
> 
>