Agree with Diego, Symmetric nature of SFC should be determined based on
type of  SF used in the chain.
SF types dpi, firewall , NAT, need to see both forward and reverse flows
hence SFC built using such SFs would need to be symmetric.
If any one SF in a SFC has symmetric path requirement, RSP should be
symmetric.

Regards,
Swati


On Thu, Nov 10, 2016 at 4:59 PM, Diego Jesus Granados Lopez <
[email protected]> wrote:

> Hi,
>
> Not really following your point on this. I think the contrary: SF having a
> symmetric flag makes all the sense, but it would be desirable that SFP
> don't have it. E.g. think of the header enrichment service function type:
> it would be great if any HE vendor could specify whether his HE SF is
> symmetric or not (e.g. Ericsson sells the "Ericsson HE"; it is a
> transparent HE SF that don't need symmetry, hence it is a not-symmetric
> SF"; another vendor sells the "OtherVendor HE", that is a proxy, and
> defines its SF as symmetric). From the SFC operator standpoint, he simply
> choses a HE SF among all the vendors building SFs belonging to the header
> enrichment type and defines the path, and it is SFC what determines whether
> the symmetric RSP is needed or not depending on the SFs part of it. This
> way, we simplify operation (i.e. the operator choses a HE based on business
> needs, but never needs to think about symmetry) and prevent configuration
> mistakes (e.g. the operator configuring a SFP
>  as not symmetric but including a SF which needed the symmetric path). I
> could think of the same reasoning being applicable for other SF types:
> dpi...
>
> Best regards,
> Diego
>
> -----Original Message-----
> From: [email protected] [mailto:
> [email protected]] On Behalf Of Yang, Yi Y
> Sent: jueves, 10 de noviembre de 2016 12:06
> To: Brady Allen Johnson <[email protected]>;
> [email protected]
> Subject: Re: [sfc-dev] Deprecating SFC, SFP, and RSP symmetric fields
>
> I think SFP can keep it, others can remove it, it doesn't make sense for a
> SF to have a symmetric flag.
>
> -----Original Message-----
> From: [email protected] [mailto:
> [email protected]] On Behalf Of Brady Allen Johnson
> Sent: Thursday, November 10, 2016 6:42 PM
> To: [email protected]
> Subject: [sfc-dev] Deprecating SFC, SFP, and RSP symmetric fields
>
>
> Currently there is a symmetric field in the SFC, SFP, and RSP data models.
> I will deprecate these fields now in Carbon.
>
> Instead of defining this in one of [SFC, SFP, RSP] a chain will be
> symmetric if it has an SF whose SF-type has the symmetry flag set to true.
> The SF-type symmetry field was also added in Beryllium.
>
> It was always confusing what it meant if there is some combination of
> symmetric values for the SFC, SFP, and RSP. That is, what if SFC:symmetric
> is true, SFP:symmetric is false, and RSP:symmetric is true? Or some similar
> combination?
>
> Currently, a reverse RSP is created if the SFP symmetric field is true.
> This will still be the case in Carbon, but we will also check the SF-types
> as explained above. In Nitrogen, we'll remove the SFP symmetric field check.
>
> I've already updated the SFC Carbon Release Plan to mention these
> deprecated fields.
>
> Regards,
>
> Brady
>
>
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