Re: [Pce] 答复: I-D Action: draft-ietf-pce-inter-layer-ext-07.txt

[Ramon Casellas <[e-mail]>]

On 07/13/2012 11:02 AM, Fatai Zhang wrote:
> Hi all,
>
> A new version has been submitted. Only one change:
>
> Introduce a new PCEP object (SERVER-INDICATION) to replace ERO subobject in Section 3.5, because one comment was raised that ERO subobject should defer to CCAMP extension (RSVP-TE extension).
>
> Please review this draft for details.
>
Hi Fatai, authors,

Thanks for updating the draft, just a couple of questions, quoting:

PCE MAY specify the server layer path information in the ERO. In this
case, the requested PCE replies a PCRep message that includes at least
two sets of ERO information in the path-list, one is for the client
layer path information, and another one is the server layer path
information. When SERVER-INDICATION is included in a PCRep message, it
indicates that the path in the ERO is the server layer path information.

Q1)
for clarification, I take it that it is still possible that the "SERVER
layer" part or segment can still be provided simply "embedded" in a
single ERO that includes both layers, right? i.e. a single strict ERO in
a MRN/MLN and that the corresponding region border node is responsible
for detecting the far end etc. In other words, the use case where a
single ERO includes both client and server layers (in a single path)
would be ok, and not against the quoted paragraph: The response includes
only 1 ERO A B C a b c d e D E F and, (optionally), a second path with
ERO C a b c d e D + SERVER_INDICATION. (Before the update, we used A B C
X a b c d e X D E F to "tag" region changes if needed). I take it the
new text means "A PCE MAY specify both the client and server layers
separately, in dedicated EROs. In this case..." is this right?


A --- B --- C ============= D --- E -- F
| |
a -- b -- c -- d -- e

Q2)
Also, assume A is the higher layer LSP (A --> F) ingress node and the
PCC, and a H-LSP / FA will be stablished when the high layer Path
reaches C. Assume A gets the PCEP response from the PCE. The issue I
have now is that how would RSVP-TE "forward" the server layer to C so it
is useful? would I need to merge the ERO?

In summary, in my implementation either:

a) I have a multi-layer ERO, without "tags" or "banners" so each node
needs to check if it is a region boundary node, and act accordingly-

b) I have a multi-layer ERO, tagged with the sub-object (until draft
-06) X. That subobject tells the ERO processing node that it is a
boundary node, and both layers are "embedded" in a single ERO.

c) I have e.g. two EROs, split on a per server basis : client and
server. How do I forward these to node C? what is the benefit of
splitting them?

Hopefully I have formulated my question clearly :)

Thanks and best regards
Ramon