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

[Alexander Vainshtein <[e-mail]>]

Gyan,
I fully agree with your suggestions – with a couple of comments:

  *   Replication SID inherently requires usage of an external controller for setup and maintenance of P2MP SR Policies
  *   BIER inherently requires new forwarding HW.

As a consequence, BGP multicast looks as the only option for replacing mLDP without a serious overhaul of the existing networks while at the same time being forward-compatible with the external controller if/when such a controller is deployed.

My 2c,
Sasha

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

From: Gyan Mishra <[e-mail]>
Sent: Monday, May 30, 2022 5:15 PM
To: Rabadan, Jorge (Nokia - US/Sunnyvale) <[e-mail]>
Cc: Alexander Vainshtein <[e-mail]>; Andrew Alston - IETF <andrew-ietf=[e-mail]>; SPRING WG <[e-mail]>; Stewart Bryant <[e-mail]>; [e-mail]; mpls-chairs <[e-mail]>; [e-mail]
Subject: Re: [Pals] [EXTERNAL] Re: [spring] Martini Pseudowires and SR

Other options for operators migrating to SR for Multicast P-Tree which is still being developed by vendors is BIER which is stateless.

BGP Multicast Controller is a new solution which is being developed which uses TEA RFC 9012 for signaling encoding alternative to MVPN procedures defined in RFC 6513 and 6514  for P2P Tree PTA encoding.  This is based on BGP MCAST TREE SAFI defined in BGP Multicast draft. This draft provides a more general solution and as well supports both mLDP inband and out of band signaling as well as non mLDP based  SR use cases.

BIER RFC 8296 & RFC 8279

BGP Multicast

https://datatracker.ietf.org/doc/html/draft-ietf-bess-bgp-multicast-00<https://clicktime.symantec.com/3KqavuAgY9sQ8iqEFj1kVTg6H4?u=https%3A%2F%2Fdatatracker.ietf.org%2Fdoc%2Fhtml%2Fdraft-ietf-bess-bgp-multicast-00>


BGP Multicast Controller

https://datatracker.ietf.org/doc/html/draft-ietf-bess-bgp-multicast-controller-09#section-3.1.1<https://clicktime.symantec.com/346JXtL3UeNEA1Sepb1HyFn6H4?u=https%3A%2F%2Fdatatracker.ietf.org%2Fdoc%2Fhtml%2Fdraft-ietf-bess-bgp-multicast-controller-09%23section-3.1.1>



Kind Regards

Gyan

On Mon, May 30, 2022 at 9:56 AM Gyan Mishra <[e-mail]<mailto:[e-mail]>> wrote:
I agree with Saha and Jorge as I stated in my response that the directional choice for use cases VPLS  E-Line, E-LAN, E-Tree signaling is to transition off LDP to BGP based signaling processing using EVPN for any L2 VPN use cases when migrating to Segment Routing both SR-MPLS and SRv6.

As I mentioned in my initial response, part of the transition in the migration is to be able to use RFC 7473 Controlling State Advertisements of Non Negotiated LDP Applications, which provides a vendor knob to turn off LDP advertisements for unicast and selectively only allow on a per application basis for both L2 VPN  customers using T-DP for signaling and MVPN PTA application PTA mLDP P2MP and MP2MP.

This knob allows the ability to create a slimmed down profile of LDP so it’s no longer used for Unicast application flows once all unicast is migrated to Segment Routing and selectively allows the per application SAC capabilities know to keep the applications requiring LDP to continue to use until the application has migrated off LDP.

For multicast solutions operators have the option of TREE SID which uses the Replication SID in SR P2MP policy which has been implemented by most vendors.

RFC 7473 SAC knob
https://datatracker.ietf.org/doc/html/rfc7473<https://clicktime.symantec.com/3SByvV3XSequcdhEJiFaYm46H4?u=https%3A%2F%2Fdatatracker.ietf.org%2Fdoc%2Fhtml%2Frfc7473>


Once all applications are migrated off LDP, LDP can be safely removed from the network.

Thanks

Gyan

On Mon, May 30, 2022 at 6:02 AM Rabadan, Jorge (Nokia - US/Sunnyvale) <[e-mail]<mailto:[e-mail]>> wrote:
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:[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/3SC2m2cTmdrBX5PAp3TCeF96H4?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/35k42Q3qar4NAkAMjAchYvE6H4?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:[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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Gyan Mishra

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Gyan Mishra

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Notice: This e-mail together with any attachments may contain information of Ribbon Communications Inc. and its Affiliates that is confidential and/or proprietary for the sole use of the intended recipient. Any review, disclosure, reliance or distribution by others or forwarding without express permission is strictly prohibited. If you are not the intended recipient, please notify the sender immediately and then delete all copies, including any attachments.