Re: [tcpm] AccECN field order

["Scheffenegger, Richard" <[e-mail]>]

Actually, your suggestion is at odds with our current flexible length of the accecn option. 

We already allow one, two or all three counters to be present - thus the requirement of an demarcation between the ordering.

With Len==5, a single counter option can only present either EE1B or EE0B.

However, we could allow Len==6 with

Kind | Length==6 | 32-bit ECEB

For a full allowable AccECN option set of:

Kind | Length==5 | 1bit order==0 | 23bit EE1B
Kind | Length==5 | 1bit order==1 | 23bit EE0B
Kind | Length==6 | 32bit ECEB
Kind | Length==8 | 1bit order==0 | 23bit EE1B | 24bit ECEB
Kind | Length==8 | 1bit order==1 | 23bit EE0B | 24bit ECEB
Kind | Length==11 | 1bit order==0 | 23bit EE1B | 24bit ECEB | 24bit EE0B
Kind | Length==11 | 1bit order==1 | 23bit EE0B | 24bit ECEB | 24bit EE1B


Richard Scheffenegger

-----Ursprüngliche Nachricht-----
Von: Joseph Touch <[e-mail]> 
Gesendet: Mittwoch, 27. Jänner 2021 18:19
An: Scheffenegger, Richard <[e-mail]>
Cc: Vidhi Goel <vidhi_goel=[e-mail]>; Michael Tuexen <[e-mail]>; tcpm IETF list <[e-mail]>; Mirja Kuehlewind <[e-mail]>; [e-mail]
Betreff: Re: [tcpm] AccECN field order

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> On Jan 27, 2021, at 1:43 AM, Scheffenegger, Richard <[e-mail]> wrote:
>
> Just for clarity, the suggestion would be something like:
>
> Kind | Length | 1-bit ordering == 0 | 23-bit EE1B [ | 24-bit ECEB [ | 
> 24-bit EE0B ] ] And Kind | Length | 1-bit ordering == 1 | 23-bit EE0B 
> [ | 24-bit ECEB [ | 24-bit EE1B ] ]
>
> With the two trailing 3-octet fields being optional in both cases.
>
> An increment in the CE counter would require at least 1+1+3+3 = 8 byte TCP option space.

It would anyway unless we’re now talking about three TCP codepoints.

Strictly, if only the CE counter changed, that could be accomplished using only 5 bytes by adding another variant, determined by the length being 5:

Kind | Length | 24-bit ECEB

At some point, the flexibility in this option needs to be supported within the option itself.

Joe