Re: [spring] Understanding the replication draft

Rishabh Parekh <rishabhp@gmail.com> Wed, 01 July 2020 19:40 UTC

Return-Path: <rishabhp@gmail.com>
X-Original-To: spring@ietfa.amsl.com
Delivered-To: spring@ietfa.amsl.com
Received: from localhost (localhost [127.0.0.1]) by ietfa.amsl.com (Postfix) with ESMTP id 8947D3A0C9D for <spring@ietfa.amsl.com>; Wed, 1 Jul 2020 12:40:03 -0700 (PDT)
X-Virus-Scanned: amavisd-new at amsl.com
X-Spam-Flag: NO
X-Spam-Score: -2.098
X-Spam-Level:
X-Spam-Status: No, score=-2.098 tagged_above=-999 required=5 tests=[BAYES_00=-1.9, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, FREEMAIL_FROM=0.001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001, URIBL_BLOCKED=0.001] autolearn=ham autolearn_force=no
Authentication-Results: ietfa.amsl.com (amavisd-new); dkim=pass (2048-bit key) header.d=gmail.com
Received: from mail.ietf.org ([4.31.198.44]) by localhost (ietfa.amsl.com [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id ZYFL0CV5446p for <spring@ietfa.amsl.com>; Wed, 1 Jul 2020 12:40:02 -0700 (PDT)
Received: from mail-wm1-x32a.google.com (mail-wm1-x32a.google.com [IPv6:2a00:1450:4864:20::32a]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by ietfa.amsl.com (Postfix) with ESMTPS id E76DD3A07C5 for <spring@ietf.org>; Wed, 1 Jul 2020 12:40:01 -0700 (PDT)
Received: by mail-wm1-x32a.google.com with SMTP id j18so23796329wmi.3 for <spring@ietf.org>; Wed, 01 Jul 2020 12:40:01 -0700 (PDT)
DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=RJXwXgZhRXob+vK0Jvlr4OGxVtgFcFNeY0SUMuwc7Xw=; b=gG8IBJvONbB505LaJdq89eGvWiVu0ymyWc+TiFsnriMvI9yqcM5KM7bUX+2/VYZ+sn HRxfG+5E3/8Ge8ua+lOCqzxgWm159kVMC7JZxqoQIO5mc8Zw1LyvMJ9I2hDCSLAiA14a haTDQrz/0TXlOwJUHpe+eJviMk2yJ6b8jUq+oVXTvT7WI8ChCvYXjUIsmMGSXLIT/bpY dSaZURFRJwTR9+EG6nceC77ACgndT4zVhGlaCXFN4caV6SYVQOv8gE/U6CUlFgWBHomI hkNDKNrDQyf2CMwQDT2yyUDnJWI3IqgbqthDdWz0l0XBJ7z07HDNLmHmSgU7MKmEcF/y pW7g==
X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=RJXwXgZhRXob+vK0Jvlr4OGxVtgFcFNeY0SUMuwc7Xw=; b=gd2ta0piDF7djmTBWKZxp4z3cAANiwsrTfdEy4CK4WNyCK+k0TTxqxXj8aIuXfNKpD eDRgY+b3u97mcNhal9kI0Jn+KQcwenLI2rjl3Tw69Kfd2M1CDsajcZvCr+e6vY+QwQ5g fNrAoEcIN2ASLVOukKBLo4wcBevs/n3loDVWa7ic5Ib1uUNl+609jzsPgJaXJhJWmqx1 PTplGpfhxdKnmM4/T/VhgURbaPIRZqqpSKEJ58SpKb8GNimSr3yqdPX7gGJg1cblqJ8n t/nWHGPLXTGkoDh67Pue1gagGZ+Eb1l7ZGyHD0xa+aKzSi/VHyBTdmz2mxk+DuBwUrq6 M11Q==
X-Gm-Message-State: AOAM531wMtnM0UcWYWJ8RwWFH+QoP2uVi/eAbmU75PiZTKYGFT3yC9NH ADLM52UyQG+byVzsQrCwg0KNRNYQZD5K5PmuSah4kODo4e4=
X-Google-Smtp-Source: ABdhPJz95Y/OgqJMAPocPHzTKOSSkjtEoJ+OTOzryNcqs9eUT+g+Bqc7z0dwV+THqF9TYwuC7dbgVXElY/9Zyexntxw=
X-Received: by 2002:a1c:dd09:: with SMTP id u9mr27000309wmg.70.1593632400285; Wed, 01 Jul 2020 12:40:00 -0700 (PDT)
MIME-Version: 1.0
References: <94415742-fc4e-1774-bf96-01eac3672bfb@joelhalpern.com> <CABjMoXYCsXb-iP55PsNWHBG187Lm7-2PXfgD3qRn_aD6ppDuMw@mail.gmail.com> <b3aaaa47-af61-6fc0-1086-bfd59efea061@joelhalpern.com> <CABjMoXY5S1Bx3rQM-0eyJfzh9iOgAZoGshs1wFqebnkVZ++G0w@mail.gmail.com> <CAOj+MMFsjRCgbY1V5idoKmqKR7W5gwM7ui7cp6W12GQm0XEHyQ@mail.gmail.com>
In-Reply-To: <CAOj+MMFsjRCgbY1V5idoKmqKR7W5gwM7ui7cp6W12GQm0XEHyQ@mail.gmail.com>
From: Rishabh Parekh <rishabhp@gmail.com>
Date: Wed, 1 Jul 2020 12:39:47 -0700
Message-ID: <CABjMoXbka+L3STNd4EPOfT5KA35ECZQt3jk=g0m=GU9VUj9csA@mail.gmail.com>
To: Robert Raszuk <robert@raszuk.net>
Cc: "spring@ietf.org" <spring@ietf.org>
Content-Type: text/plain; charset="UTF-8"
Archived-At: <https://mailarchive.ietf.org/arch/msg/spring/Hsyg6Et0vq170g1thVbBIaKh7tQ>
Subject: Re: [spring] Understanding the replication draft
X-BeenThere: spring@ietf.org
X-Mailman-Version: 2.1.29
Precedence: list
List-Id: "Source Packet Routing in NetworkinG \(SPRING\)" <spring.ietf.org>
List-Unsubscribe: <https://www.ietf.org/mailman/options/spring>, <mailto:spring-request@ietf.org?subject=unsubscribe>
List-Archive: <https://mailarchive.ietf.org/arch/browse/spring/>
List-Post: <mailto:spring@ietf.org>
List-Help: <mailto:spring-request@ietf.org?subject=help>
List-Subscribe: <https://www.ietf.org/mailman/listinfo/spring>, <mailto:spring-request@ietf.org?subject=subscribe>
X-List-Received-Date: Wed, 01 Jul 2020 19:40:04 -0000

Robert,

>A) Firmly state that replication SID MUST be the last one on the stack
>B) Instead of real SID after the replication SID provide a binding SID which locally will be mapped to a different SID list imposed to each replicated flow.

We would be fine with A), but we don't want to exclude possibility of
something like what you describe in B.

-Rishabh

On Wed, Jul 1, 2020 at 12:27 PM Robert Raszuk <robert@raszuk.net> wrote:
>
> Hi Rishabh,
>
>  > Of course, care must be
> > taken to avoid the "explosion" as you describe it. G-SID-2 has to map
> > to a unique node; for example, it may be an Anycast-SID that takes
> > packet to distinct nodes from each of the downstream node, or the
> > downstream nodes can be border nodes connecting to other segment
> > routing domains where G-SID-2 resolves to distinct nodes in each
> > domain.
>
> I think you are stretching it too thin.
>
> See even if G-SID-2 is anycast SID you have zero assurance that physical nodes packets will land on would be at all diverse.
>
> Likewise crossing domains yet providing identical global SID now to be a different node in each such domain to me is not a realistic example.
>
> I think we have two options:
>
> A) Firmly state that replication SID MUST be the last one on the stack
>
> B) Instead of real SID after the replication SID provide a binding SID which locally will be mapped to a different SID list imposed to each replicated flow.
>
> What is currently in the draft seems to be very counterintuitive and IMHO will result in operational difficulties.
>
> Thx a lot,
> R.