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Hi Sasha, It is probably just a question of terminology, but the way I see it, you don’t really need bidirectional LSPs, but a pair of unidirectional
LSPs where the origination endpoint of one matches the termination endpoint of the other. Suppose we use the example of Figure 2. PW3 and PW4 have the same end-points (AG2 and PE1), and both share the same transport LSPs in both directions. In the PE’s egress
direction, both PWs use LSP1-to-AG2. In the ingress direction both PWs use LSP1-to-PE1. Those two LSPs use the same endpoints AG2 and PE1, and it is really what LSP1 represents in the figure.
That’s how the implementation with which I’m familiar works. Maybe this is partly implicit in the text and can be clarified. Hope it helps. Thanks. Jorge
From: Alexander Vainshtein <Alexander.Vainshtein@xxxxxxxx>
Jorge,
Lots of thanks for a prompt response.
AFAIK it is perfectly valid to advertise Implicit Null label for a FEC representing a local address in RSVP-TE.
And I am not sure what you mean by “single-hop LSPs in general”.
From my POV, LSP are, generally speaking, unidirectional while PWs and Ethernet Segments are inherently bi-directional.
In the case of Ethernet Segments:
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Their egress direction affects the results of DF election
-
Their ingress direction affects inclusion – or non-inclusion of ESI label in certain copies of flooded BUM traffic.
So I still think that if you want to treat an LSP as a virtual Ethernet Segment, you need a bi-directional LSP (Be it MPLS-TP or not).
The draft, in its current form, simply ignores these differences.
What, if anything, do I miss?
Regards,
Sasha
From: Jorge Rabadan (Nokia) <jorge.rabadan@xxxxxxxxx>
Hi Sasha,
There would be more cases where you can identify traffic coming
from a given LSP.
For instance RSVP-TE, or single-hop LSPs in general, etc – there is no need for bidirectional MPLS-TP.
The text itself implicitly refers to the cases where PWs can be aggregated into a common LSP, so not sure if anything else is needed.
Thanks.
Jorge
From: Alexander Vainshtein <Alexander.Vainshtein@xxxxxxxx>
Hi all,
I have doubts regarding the text in Section 1.2 of the draft that refers to LSPs (as opposed to PWs) as virtual Ethernet Segments.
The problematic (from my POV) text refers to Figure 2 and says (the problematic part is highlighted):
In such scenarios, a virtual ES (vES) is defined as a set of
individual PWs if they cannot be aggregated into a common LSP. If
the aggregation of PWs is possible, the vES can be associated to an
LSP in a given PE. In the example of Figure 2, EVC3 is connected to
a VPWS instance in AG2 that is connected to PE1 and PE2 via PW3 and
PW5 respectively. EVC4 is connected to a separate VPWS instance on
AG2 that gets connected to an EVI on PE1 and PE2 via PW4 and PW6,
respectively.
Since the PWs for the two VPWS instances can be
aggregated into the same LSPs going to the MPLS network, a common
virtual ES can be defined for LSP1 and LSP2.
This vES will be shared
by two separate EVIs in the EVPN network.
The problem with the highlighted text is that PE1 and PE2 always can identify the PW from which they receive this or that packet, but, in most cases, cannot identify the LSP in which this PW has been running.
(The only exception of which I am aware, is the case of static PWEs in bi-directional MPLS-TP LSPs).
If LSP1 and LSP2 were components of a common virtual MH ES, PE1, upon reception of a BUM packet from PW4, would not be able to identify this MH ES and to insert a suitable ESI label into the EVPN encapsulation of the copy it
would be sending to PE2.
IMHO and FWIW some clarification (e.g., restricting ability to use LSPs as virtual Ethernet Segments to just bi-directional MPLS-TP LSPs?) would be very much in place.
Hopefully these notes will be useful.
Regards,
Sasha
The IESG has received a request from the BGP Enabled ServiceS WG (bess) to consider the following document: - 'EVPN Virtual Ethernet Segment'
<draft-ietf-bess-evpn-virtual-eth-segment-08.txt> as Proposed Standard
The IESG plans to make a decision in the next few weeks, and solicits final comments on this action. Please send substantive comments to the
last-call@xxxxxxxx mailing lists by 2023-04-27. Exceptionally, comments may be sent to
iesg@xxxxxxxx instead. In either case, please retain the beginning of the Subject line to allow automated sorting.
Abstract
EVPN and PBB-EVPN introduce a family of solutions for multipoint
Ethernet services over MPLS/IP network with many advanced features
among which their multi-homing capabilities. These solutions
introduce Single-Active and All-Active for an Ethernet Segment (ES),
itself defined as a set of physical links between the multi-homed
device/network and a set of PE devices that they are connected to.
This document extends the Ethernet Segment concept so that an ES can
be associated to a set of EVCs (e.g., VLANs) or other objects such as
MPLS Label Switch Paths (LSPs) or Pseudowires (PWs), referred to as
Virtual Ethernet Segments (vES). This draft describes the
requirements and the extensions needed to support vES in EVPN and
PBB-EVPN.
The file can be obtained via
The following IPR Declarations may be related to this I-D:
Regards,
Sasha
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