Re: [mpls-tp] [PWE3] Pseudo-wires: uni-directional o bi-directional?

Dear Stewart,
perhaps I'm applying section/segment terminology to PW without sufficient
explanation of my view. After reading comments by you and Sasha I've looked
at SS-PW as a bi-directional link or section. If such presentation of SS-PW
is valid then it's co-routedness, as you've noted, is obvious. I agree that
SS-PW can be referred as segment as well but then its co-routedness is not
self-evident. Interestingly, from the view of SS-PW as a bi-directional
link/section directly follows bi-directional co-routed essence of MS-PW.

Regards,
Greg

On Mon, Jun 28, 2010 at 12:26 PM, Stewart Bryant <stbryant@cisco.com> wrote:

>  Greg
>
> I do not understand your point.
>
> MS-PW S-PEs serve a purpose in breaking the PW into segments. If you do not
> need that decomposition in a network, there is nothing requiring their use.
> However we should not prohibit their use either, as there are scenarios
> whether this decomposition is of benefit.
>
> If you need an existence proof of this point, remember that we initially
> designed SS-PW and needed to create MS-PW to address requirements of network
> operators that has deployed SS-PW.
>
> Stewart
>
>
>
>
>
>
> On 28/06/2010 15:01, Greg Mirsky wrote:
>
> Dear Sasha,
> I too find Stewart's explanation very useful for overall MPLS-TP. And in
> this perspective perhaps the SS PW might be also referred as PW section.
>
> Regards,
> Greg
>
> On Mon, Jun 28, 2010 at 8:56 AM, Alexander Vainshtein <
> Alexander.Vainshtein@ecitele.com> wrote:
>
>>  Stewart,
>>
>> Lots of thanks for a prompt and unambiguous response..
>>
>> This issues looks like one more fine point of MPLS-TP-ese to me: Does
>> “co-routed” mean “co-routed in the immediate lower layer” or “co-routed in
>> all the underlying layers down to the duct”?
>>
>> FWIW, I tend to agree with your interpretation: “co-routed” means
>> “co-routed in the immediate lower layer”, and hence PWs (both single-segment
>> and multi-segment) are co-routed bi-directional LSPs.
>>
>>
>>
>> Regards,
>>
>>      Sasha
>>
>>
>>
>> *From:* pwe3-bounces@ietf.org [mailto:pwe3-bounces@ietf.org] *On Behalf
>> Of *Stewart Bryant
>> *Sent:* Monday, June 28, 2010 3:46 PM
>> *To:* pwe3@ietf.org
>>
>> *Subject:* Re: [PWE3] Pseudo-wires: uni-directional o bi-directional?
>>
>>
>>
>>
>>
>>    It seems to me that PWs are associated bi-directional LSPs...
>>
>>
>>
>> PWs are co-routed bi-directional since it is required that they go through
>> the same xPEs in each direction, and the xPEs knows about the association of
>> the two directional components.
>>
>> Whether they run over co-routed bi-directional, or associated
>> bi-directional LSP is a deployment/applicability issue.
>>
>> - Stewart
>>
>>
>>
>>
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>
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