Re: [spring] [Pals] [EXTERNAL] Re: Martini Pseudowires and SR

[Alexander Vainshtein <[e-mail]>]

Jorge and all,
Here is a (admittedly incomplete) list of things that, AFAIK, today are not supported with EVPN VPWS:

  1.  All the non-Ethernet PW types (28 such types can be found in the IANA registry<https://www.iana.org/assignments/pwe3-parameters/pwe3-parameters.xhtml#pwe3-parameters-2>)
     *   Not sure if all these types are relevant for the industry today
     *   AFAIK, TDM and SONET over packet are still widely deployed
  2.  Differentiation between Raw and Tagged Ethernet PW types (not sure it is needed, but still)
  3.  All Interface Attributes listed in the IANA registry with the following exclusions:
     *   Interface MTU  (EVPN VPWS supports a standard way to ignore it which IMHO is one great advantage over LDP-based signaling)
     *   Flow Label (support is defined in 7432bis)
  4.  Full-blown PW status signaling
  5.  FCS retention – not sure it is used these days
  6.  PW fragmentation and reassembly - not sure it is used these days.

Regards,
Sasha

Office: [phone]
Cell:      [phone]
Email:   [e-mail]

From: Rabadan, Jorge (Nokia - US/Sunnyvale) <[e-mail]>
Sent: Monday, May 30, 2022 1:02 PM
To: Alexander Vainshtein <[e-mail]>; Stewart Bryant <[e-mail]>; Andrew Alston - IETF <andrew-ietf=[e-mail]>; mpls-chairs <[e-mail]>
Cc: SPRING WG <[e-mail]>; [e-mail]; [e-mail]
Subject: Re: [Pals] [EXTERNAL] Re: [spring] Martini Pseudowires and SR

I concur with Sasha.
We’ve been gone through a significant effort to unify the service signaling by using EVPN. If we are missing anything in EVPN VPWS compared to T-LDP based PWs, I would rather look at extending EVPN VPWS (if needed). If not an option, it would good to discuss at least why EVPN VPWS is not an option.

Thanks,
Jorge


From: Pals <[e-mail]<mailto:[e-mail]>> on behalf of Alexander Vainshtein <[e-mail]<mailto:[e-mail]>>
Date: Monday, May 30, 2022 at 10:58 AM
To: Stewart Bryant <[e-mail]<mailto:[e-mail]>>, Andrew Alston - IETF <andrew-ietf=[e-mail]<mailto:andrew-ietf=[e-mail]>>, mpls-chairs <[e-mail]<mailto:[e-mail]>>
Cc: SPRING WG <[e-mail]<mailto:[e-mail]>>, [e-mail]<mailto:[e-mail]> <[e-mail]<mailto:[e-mail]>>, [e-mail]<mailto:[e-mail]> <[e-mail]<mailto:[e-mail]>>
Subject: Re: [Pals] [EXTERNAL] Re: [spring] Martini Pseudowires and SR
Stewart, Andrew and all,
++ Bess WG.
I fully agree that using (targeted) LDP for setup of Martini PWs in an SR-based environment is quite problematic for the operators.

One alternative is transition to setup of PWs using MP BGP based on the EVPN-VPWS mechanisms (RFC 8214<https://clicktime.symantec.com/3Qviu2KUub4f1w6MeHVbgcu6H4?u=https%3A%2F%2Fdatatracker.ietf.org%2Fdoc%2Fhtml%2Frfc8214>)

These mechanisms probably require some extension to support PWs that carry non-Ethernet customer traffic as well as support of some features that can be signaled via LDP for Ethernet PWs but cannot be signaled today with EVPN-VPWS (e.g., FCS retention – RFC 4720<https://clicktime.symantec.com/32Jf7wnYMxKQPc3r3RR9Cy96H4?u=https%3A%2F%2Fdatatracker.ietf.org%2Fdoc%2Fhtml%2Frfc4720>)

My guess is that, once the basic EVPN-VPWS signaling is supported, migration of LDP-signaled PWs to EVPN-VPWS would be simple enough.

This work, if approved, would require intensive cooperation between PALS WG and BESS WG.

My 2c,
Sasha

Office: [phone]
Cell:      [phone]
Email:   [e-mail]<mailto:[e-mail]>

From: Pals <[e-mail]<mailto:[e-mail]>> On Behalf Of Stewart Bryant
Sent: Monday, May 30, 2022 11:10 AM
To: Andrew Alston - IETF <andrew-ietf=[e-mail]<mailto:andrew-ietf=[e-mail]>>; [e-mail]<mailto:[e-mail]>; mpls-chairs <[e-mail]<mailto:[e-mail]>>
Cc: SPRING WG <[e-mail]<mailto:[e-mail]>>
Subject: [EXTERNAL] Re: [Pals] [spring] Martini Pseudowires and SR

Including the PALS and MPLS WGs in the discussion.

In the case of PWs, LDP runs directly between the T-PEs to provide the control plane. If it is known that the only use of LDP is to support PW, then a lightweight profile of LDP might be implemented, ignoring unused parts, but this does not necessarily need a standard.

Before you can profile LDP, you have to also profile PWs to determine which subset of the PW system you need to support. The danger here is that you end up going through the PW development cycle again as old requirements re-emerge.

Stewart



Sent from my iPad


On 30 May 2022, at 07:22, Andrew Alston - IETF <andrew-ietf=[e-mail]<mailto:andrew-ietf=[e-mail]>> wrote:

Hi All,

Sending this email wearing only the hat of a working group participant.

One of the things that our network uses, and is used by so many networks out there, are martini based pseudowires (which for clarity are generally setup using what is described in RFC8077).  In an SR world however, this creates a problem, because typically you don’t want to run LDP in an SR context.  This means that standard martini pseudowires no longer function.  This gets even more complicated when you want to do martini based pseudowires over an IPv6 only network, particularly considering the lack of widespread support for LDP6.

This is also relevant in cases where networks wish to run SR-MPLS in the absence of SRv6 for whatever reason.

So, my question to the working group is this:

Is it worth looking at creating a form of LDP light – both compatible with IPv4 and IPv6 – that simply exists to setup and tear down the service labels for point to point services.  A form of targeted LDP without all the other complexities involved in LDP – that could potentially run at a lower preference than LDP itself (so if LDP is there, use it, if not use this)

Before I start drafting though, I would like to hear from the working group if there are others who feel that this is worth doing and, call this a call for expressions of interest in those who may be willing to work towards something like this.  Happy to take emails on list or off list and see if we can find a solution.

Looking forward to hearing from you all

Thanks

Andrew



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