Re: [Detnet] draft-ietf-detnet-architecture-07

János Farkas <janos.farkas@ericsson.com> Fri, 03 August 2018 16:04 UTC

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To: DetNet WG <detnet@ietf.org>, "BRUNGARD, DEBORAH A" <db3546@att.com>, Lou Berger <lberger@labn.net>, "Black, David" <David.Black@dell.com>, Greg Mirsky <gregimirsky@gmail.com>, "Andrew G. Malis" <agmalis@gmail.com>
References: <99657d22-f9e4-8a1a-27de-6997900f727e@labn.net> <4900e61d-8399-8765-0ecb-181dc3c9ff5a@ericsson.com> <CE03DB3D7B45C245BCA0D24327794936301A79DE@MX307CL04.corp.emc.com> <ba0c0b74-8d2e-c332-18c6-02a2649cddf0@ericsson.com> <CE03DB3D7B45C245BCA0D24327794936301D75F4@MX307CL04.corp.emc.com> <61d00506-b546-6c80-044f-b5bdb243ae23@ericsson.com> <CE03DB3D7B45C245BCA0D24327794936301D84CF@MX307CL04.corp.emc.com> <VI1PR0702MB3567FE3D1186992F38378AE3F2530@VI1PR0702MB3567.eurprd07.prod.outlook.com> <CE03DB3D7B45C245BCA0D24327794936301E0973@MX307CL04.corp.emc.com> <VI1PR0702MB3567B1C356B53A956E0C35B4F2530@VI1PR0702MB3567.eurprd07.prod.outlook.com> <3DF0466E9510274382F5B74499ACD6F8D383DD@DFWPML704-CHM.exmail.huawei.com> <164af982488.282b.9b4188e636579690ba6c69f2c8a0f1fd@labn.net> <CE03DB3D7B45C245BCA0D24327794936301E1B68@MX307CL04.corp.emc.com> <CAH7SZV9-JU4W1pi56Ye8h6DHs-XwpX4LGrOTqfZangS8PhVBxw@mail.gmail.com> <d25c2a87-4d9f-7efb-3f34-f3ed0a225dd5@ericsson.com>
CC: "draft-ietf-detnet-architecture@ietf.org" <draft-ietf-detnet-architecture@ietf.org>
From: János Farkas <janos.farkas@ericsson.com>
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Date: Fri, 03 Aug 2018 18:03:47 +0200
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Archived-At: <https://mailarchive.ietf.org/arch/msg/detnet/KM4F3xyAD69ttBFc1HzAvm70pO0>
Subject: Re: [Detnet] draft-ietf-detnet-architecture-07
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I forgot to mention that the next step is gated by August vacations.

Best regards,
János

On 8/3/2018 5:39 PM, János Farkas wrote:
> Hi,
>
> We have updated the architecture draft to resolve the extended WGLC 
> comments. The current revision is v07: 
> https://tools.ietf.org/html/draft-ietf-detnet-architecture-07.
>
> All WGLC comments have been addressed; most of them can be found 
> below. Some further nits have been also resolved.
>
> The main changes:
>
> 1)
> Based on the last discussion item below, a new sentence has been added 
> to congestion protection in section 3.1, where it is first described:
> "Note that congestion
> protection provided via congestion detection and notification is
> explicitly excluded from consideration in DetNet, as it serves a
> different set of applications."
>
> (Note that throttling/throttled has been already part of the text, 
> there are three occurrences.)
>
> 2)
> Based on the discussion below, the following introductory text has 
> been added to section 4.1:
> "DetNet functionality (Section 3) is implemented in two adjacent
> layers in the protocol stack: the DetNet service layer and the DetNet
> transport layer. The DetNet service layer provides DetNet service,
> e.g., service protection, to higher layers in the protocol stack and
> applications. The DetNet transport layer supports DetNet service in
> the underlying network, e.g., by providing explicit routes and
> congestion protection to DetNet flows."
>
> Consequently, the definition of DetNet service layer has been updated to:
> "The layer at which A DetNet service, e.g., service protection
> is provided."
>
> 3)
> Based on 
> https://www.ietf.org/mail-archive/web/detnet/current/msg01577.html, 
> the following sentence has been added to the OAM paragraph in section 
> 4.1.1:
> "Active and hybrid OAM
> methods require additional bandwidth to perform fault management and
> performance monitoring of the DetNet domain. OAM may, for instance,
> generate special test probes or add OAM information into the data
> packet."
>
> 4)
> Based on the consensus reached at the DetNet session at IETF 102, 
> Controller Plane Entity (CPE) has been replaced with Controller Plane 
> Function (CPF).
>
> 5)
> In order to clarify, the last sentence of the introduction has been 
> updated to:
> "DetNet can
> accommodate various time synchronization techniques and profiles that
> are defined elsewhere to address the needs of different market
> segments."
>
> 6)
> In order to clarify, the packet loss bullet in section 3.1 has been 
> updated to:
> "Packet loss ratio, under various assumptions as to the operational
> states of the nodes and links."
>
> 7)
> DetNet t-aware has been updated to:
> "A DetNet transport-aware system. It knows about
> some TSN functions (e.g., reservation), but not about service
> protection."
>
> 8)
> DetNet s-aware has been updated to:
> "DetNet service-aware system. It supplies
> sequence numbers, but doesn’t know about zero congestion loss."
>
>
> Best regards,
> János
>
>
> On 7/19/2018 2:04 AM, Prof. Diego Dujovne wrote:
>> +1
>>
>> El mié., 18 de jul. de 2018 19:53, Black, David <David.Black@dell.com 
>> <mailto:David.Black@dell.com>> escribió:
>>
>>     +1, Thanks, --David
>>
>>     *From:*Lou Berger [mailto:lberger@labn.net
>>     <mailto:lberger@labn.net>]
>>     *Sent:* Wednesday, July 18, 2018 6:52 PM
>>     *To:* Norman Finn; Janos Farkas; Black, David
>>     *Cc:* DetNet WG
>>     *Subject:* Re: [Detnet] WG Last Call:
>>     draft-ietf-detnet-architecture-05
>>
>>     This sounds sensible to me...
>>
>>     Lou
>>
>>     ------------------------------------------------------------------------
>>
>>     On July 18, 2018 6:47:01 PM Norman Finn
>>     <norman.finn@mail01.huawei.com
>>     <mailto:norman.finn@mail01.huawei.com>> wrote:
>>
>>         "Congestion loss protection" is better than "congestion
>>         protection".  That's good.
>>
>>         It's a big change, and makes the document unnecessarily
>>         wordy.  That's bad.
>>
>>         I would use "congestion protection" but explain somewhere
>>         that we are not talking about source throttling.
>>
>>         And if adding that explanation is difficult or controversial,
>>         I would stick with "congestion protection".
>>
>>         -- Norm
>>
>>         ------------------------------------------------------------------------
>>
>>         *From:*detnet [detnet-bounces@ietf.org
>>         <mailto:detnet-bounces@ietf.org>] on behalf of Janos Farkas
>>         [Janos.Farkas@ericsson.com <mailto:Janos.Farkas@ericsson.com>]
>>         *Sent:* Wednesday, July 18, 2018 2:26 PM
>>         *To:* Black, David
>>         *Cc:* DetNet WG
>>         *Subject:* Re: [Detnet] WG Last Call:
>>         draft-ietf-detnet-architecture-05
>>
>>         Both “congestion protection” and “congestion loss protection”
>>         work for me.
>>
>>         Note that the architecture document is quite populated with
>>         the term “congestion protection”. I do not know the other
>>         documents by heart.
>>
>>         So it would be a bit of a change..
>>
>>         I’d like to have the group’s opinion before making such a
>>         change, e.g., any objections?
>>
>>         Thanks,
>>
>>         Janos
>>
>>         *From:*Black, David <David.Black@dell.com
>>         <mailto:David.Black@dell.com>>
>>         *Sent:* Wednesday, July 18, 2018 8:19 PM
>>         *To:* Janos Farkas <Janos.Farkas@ericsson.com
>>         <mailto:Janos.Farkas@ericsson.com>>
>>         *Cc:* DetNet WG <detnet@ietf.org <mailto:detnet@ietf.org>>
>>         *Subject:* RE: [Detnet] WG Last Call:
>>         draft-ietf-detnet-architecture-05
>>
>>         Hi Janos,
>>
>>         That text works nicely.  In briefly talking to Lou, a related
>>         suggestion surfaced: “congestion protection” -> “congestion
>>         loss protection” where possible (may need to be abbreviated
>>         in the Figure) .
>>
>>         This change would make it clearer that the primary focus is
>>         protection from losses caused by congestion as opposed to
>>         protection from all congestion.  DetNet should be able to
>>         tolerate some modest congestion (e.g., in nodes that don’t
>>         have reserved DetNet resources) as long as delivery is
>>         reliable and timely.
>>
>>         Thanks, --David
>>
>>         *From:*Janos Farkas [mailto:Janos.Farkas@ericsson.com]
>>         *Sent:* Wednesday, July 18, 2018 11:45 AM
>>         *To:* Black, David
>>         *Cc:* DetNet WG
>>         *Subject:* RE: [Detnet] WG Last Call:
>>         draft-ietf-detnet-architecture-05
>>
>>         Hi David,
>>
>>         This implies updating the definition of the DetNet service
>>         layer, e.g., to:
>>
>>         DetNet service layer
>>
>>         The layer at which A DetNet Service, e.g., service protection
>>         is provided.
>>
>>         The definition of the DetNet transport layer remains the same:
>>
>>         DetNet transport layer
>>
>>         The layer that optionally provides congestion protection for
>>
>>         DetNet flows over paths provided by the underlying network.
>>
>>         Regards,
>>
>>         Janos
>>
>>         *From:*Black, David <David.Black@dell.com
>>         <mailto:David.Black@dell.com>>
>>         *Sent:* Monday, July 16, 2018 3:21 PM
>>         *To:* Janos Farkas <Janos.Farkas@ericsson.com
>>         <mailto:Janos.Farkas@ericsson.com>>
>>         *Cc:* DetNet WG <detnet@ietf.org <mailto:detnet@ietf.org>>
>>         *Subject:* RE: [Detnet] WG Last Call:
>>         draft-ietf-detnet-architecture-05
>>
>>         Don’t use “congestion protection” in the definitions for both
>>         levels.
>>
>>         Thanks, --David
>>
>>         *From:*János Farkas [mailto:janos.farkas@ericsson.com]
>>         *Sent:* Sunday, July 15, 2018 10:43 PM
>>         *To:* Black, David
>>         *Cc:* DetNet WG
>>         *Subject:* Re: [Detnet] WG Last Call:
>>         draft-ietf-detnet-architecture-05
>>
>>         Thank you David!
>>
>>         I think we are set. :-)
>>
>>         You got a point, we should update
>>         "DetNet service layer is the layer at which A DetNet Service,
>>         such as congestion or service protection is provided."
>>         to
>>         "DetNet service layer is the layer at which A DetNet Service,
>>         such as congestion protection and/or service protection is
>>         provided."
>>         in the definitions as well to make it clear.
>>
>>         Thanks,
>>         Janos
>>
>>         On 7/16/2018 3:03 AM, Black, David wrote:
>>
>>             Moving the only two open items to the top …
>>
>>             -- Section 4
>>
>>             > We could add some introductory text to 4.1 or 4.1.1, for
>>             instance:
>>             > The functionality needed for DetNet (Section 3) are
>>             implemented in the DetNet layer which comprises the
>>             DetNet service layer and the DetNet transport layer.
>>
>>             > The DetNet service layer functions rely on flow
>>             identification and sequencing. The DetNet transport layer
>>             function may rely on flow identification.
>>             >
>>             > What do you think?
>>
>>             I prefer functional (what it does) characterization to
>>             mechanistic (how it works) characterization in an
>>             overview, e.g., excerpting from what I originally wrote:
>>
>>             ·The DetNet Service layer provides timely reliable
>>             in-order DetNet flow delivery to applications that use
>>             DetNet.
>>
>>             ·The DetNet Transport layer insulates DetNet flows from
>>             interference by network mechanisms, primarily queuing and
>>             routing
>>
>>             I understand the principle.
>>
>>             What about just copying the two definitions here:
>>             DetNet service layer is the layer at which A DetNet
>>             Service, such as congestion or service protection is
>>             provided.
>>             DetNet transport layer optionally provides congestion
>>             protection for DetNet flows over paths provided by the
>>             underlying network.
>>
>>             David> Yes, that works, although I don’t think
>>             “congestion” was meant to be included in the first
>>             definition …
>>
>>                Many real-time networks rely on physical rings or
>>             chains of two-port
>>
>>                devices, with a relatively simple ring control protocol.
>>
>>             How does a “ring control protocol” control “chains”? 
>>             Suggest: “ring control protocol” -> “control protocol”
>>
>>             Also, are paired chains between common endpoints
>>             intended, or a more general notion of chains?
>>
>>             This text refers to typical factory deployment, which is
>>             chain or ring..
>>             It seems better to keep “ring control protocol” because
>>             they are often very different from generic control
>>             protocols applicable to mesh networks.
>>
>>             Would flipping chain and ring resolve your concern?
>>
>>                Many real-time networks rely on physical chains or
>>             rings of two-port
>>
>>                devices, with a relatively simple ring control protocol.
>>
>>             */[David>] /*It feels like “ring control protocol” is an
>>             important phrase to retain.   In the original text, would
>>             it be reasonable to add “(applies to both rings and
>>             chains)” to the end of the sentence?
>>
>>             Well, I guess the point is that there are many specific
>>             ring protocols, but we are looking for a generic solution.
>>             What about deleting "chains" from the sentence?
>>
>>             David> Yes, if the sentence is all about rings, it’s clear.
>>
>>             Thanks, --David
>>
>>             *From:*János Farkas [mailto:janos.farkas@ericsson.com]
>>             *Sent:* Sunday, July 15, 2018 7:25 PM
>>             *To:* Black, David
>>             *Cc:* DetNet WG
>>             *Subject:* Re: [Detnet] WG Last Call:
>>             draft-ietf-detnet-architecture-05
>>
>>             Hi David,
>>
>>             Please see in-line.
>>
>>             Thank you!
>>             Janos
>>
>>             On 7/6/2018 11:50 PM, Black, David wrote:
>>
>>                 -- Bridged path definition
>>
>>                 >  Or should we do something else?
>>
>>                 > There is only one occurrence of "bridged path" in
>>                 the text in brackets.
>>
>>                 That sounds like a better suggestion – change that
>>                 occurrence and remove the definition of “bridged
>>                 path” from the draft. That occurrence is in Section
>>                 4.1.1:
>>
>>                 Congestion protection
>>
>>                 The DetNet transport layer provides congestion
>>                 protection.
>>
>>                 See Section 4.5.  The actual queuing and shaping
>>                 mechanisms
>>
>>                 are typically provided by underlying subnet layers,
>>                 these can
>>
>>                 be closely associated with the means of providing
>>                 paths for
>>
>>                           DetNet flows (e.g., MPLS LSPs or bridged
>>                 paths), the path and
>>
>>                 the congestion protection are conflated in this figure.
>>
>>                 Perhaps: (e.g., MPLS LSPs or bridged paths) -> (MPLS
>>                 LSPs or other network paths)
>>
>>                 or just delete the entire parenthetical example.
>>
>>             OK. Let's just delete the entire parenthetical example.
>>
>>                 -- Section 4
>>
>>                 > We could add some introductory text to 4.1 or 4.1.1,
>>                 for instance:
>>                 > The functionality needed for DetNet (Section 3) are
>>                 implemented in the DetNet layer which comprises the
>>                 DetNet service layer and the DetNet transport layer.
>>
>>                 > The DetNet service layer functions rely on flow
>>                 identification and sequencing. The DetNet transport
>>                 layer function may rely on flow identification.
>>                 >
>>                 > What do you think?
>>
>>                 I prefer functional (what it does) characterization
>>                 to mechanistic (how it works) characterization in an
>>                 overview, e.g., excerpting from what I originally wrote:
>>
>>                   * The DetNet Service layer provides timely reliable
>>                     in-order DetNet flow delivery to applications
>>                     that use DetNet.
>>                   * The DetNet Transport layer insulates DetNet flows
>>                     from interference by network mechanisms,
>>                     primarily queuing and routing
>>
>>             I understand the principle.
>>
>>             What about just copying the two definitions here:
>>             DetNet service layer is the layer at which A DetNet
>>             Service, such as congestion or service protection is
>>             provided.
>>             DetNet transport layer optionally provides congestion
>>             protection for DetNet flows over paths provided by the
>>             underlying network.
>>
>>
>>                 > Should we also rearrange, e.g., indent the text
>>                 after Figure 2 such that
>>                 > Packet sequencing, Duplicate elimination, Flow
>>                 replication, Flow merging, Packet encoding, and
>>                 Packet decoding get under Service layer
>>                 > and
>>                 > Congestion protection and Explicit routes get under
>>                 Transport layer?
>>
>>                 No, I don’t think that’s necessary – Figure 2
>>                 provides sufficient structure.
>>
>>             OK.
>>
>>                 Plus a few more minor comments inline …
>>
>>                 Thanks, --David
>>
>>                 *From:*János Farkas [mailto:janos.farkas@ericsson.com]
>>                 *Sent:* Wednesday, July 4, 2018 2:15 PM
>>                 *To:* Black, David
>>                 *Cc:* DetNet WG
>>                 *Subject:* Re: [Detnet] WG Last Call:
>>                 draft-ietf-detnet-architecture-05
>>
>>                 Hi David,
>>
>>                 Thank you very much for your review and comments!
>>
>>                 Please see in-line.
>>
>>                 On 6/29/2018 4:10 PM, Black, David wrote:
>>
>>                     The -06 version of this draft is much improved
>>                     over the -05 version – lots of diligent work by
>>                     the authors is evident and appreciated.
>>
>>                     I have two minor content concerns and some
>>                     smaller editorial items.
>>
>>                     ** Content
>>
>>                     -- Section 2.2
>>
>>                     The definition of “bridged path” looks like a
>>                     definition of “bridged forwarding” – the
>>                     definition needs to encompass the notion of a
>>                     path that involves more than one bridge.
>>
>>                        bridged path
>>
>>                                A VLAN bridge uses the VLAN ID and the
>>                     destination MAC
>>
>>                                address to select the outbound port
>>                     hence the path for a
>>
>>                                frame.
>>
>>                 You are right, it looks like the emphasis is on
>>                 bridge forwarding rather than path.
>>                 However, the superposition of the outbound ports
>>                 provides a path, which was tried to be captured by
>>                 "hence the path".
>>                 The idea was to keep it simple not dive into the
>>                 details, which are not necessary in this document.
>>
>>                 Would it be good to update to:
>>
>>                    bridged path
>>
>>                            A VLAN bridge uses the VLAN ID and the
>>                 destination MAC
>>
>>                            address to select the outbound port. The
>>                 superposition
>>
>>                            of the outbound ports is the path for a frame.
>>
>>                 ?
>>
>>                 Or should we do something else?
>>                 There is only one occurrence of "bridged path" in the
>>                 text in brackets.
>>
>>                     -- Section 4
>>
>>                     Figure 2 in Section 4.1.1 introduces the Detnet
>>                     service and transport layers.   The associated
>>                     text quickly dives into explaining the
>>                     functionality in those layers, but it would be
>>                     helpful to start with an initial high level
>>                     description of each of those layers that helps
>>                     motivate their separation.  It appears that:
>>
>>                     - The DetNet Service layer provides timely
>>                     reliable in-order DetNet flow delivery to
>>                     applications that use DetNet.   A DetNet flow at
>>                     the top of the DetNet Service layer may or may
>>                     not be a compound flow at the bottom of that layer.
>>
>>                     - The DetNet Transport layer insulates DetNet
>>                     flows (at the bottom of the DetNet Service layer)
>>                     from interference by network mechanisms,
>>                     primarily queuing and routing, where congestion
>>                     is an indication of queueing interference.  A
>>                     DetNet flow at the top of the DetNet Transport
>>                     layer may or may not be a member flow that is
>>                     part of a compound flow, depending on what is
>>                     done in the DetNet Service layer.
>>
>>
>>                 You are right, section 4 jumps into the details
>>                 without much of an introduction. I guess we had a
>>                 kind of chicken and egg problem here. Figure 4
>>                 provides a higher level view than Figure 2. However,
>>                 Figure 4 captures different aspects, dives into the
>>                 details of data plane options. So, it seems better to
>>                 keep the order.
>>
>>                 We could add some introductory text to 4.1 or 4.1.1,
>>                 for instance:
>>                 The functionality needed for DetNet (Section 3) are
>>                 implemented in the DetNet layer which comprises the
>>                 DetNet service layer and the DetNet transport layer.
>>                 The DetNet service layer functions rely on flow
>>                 identification and sequencing. The DetNet transport
>>                 layer function may rely on flow identification.
>>
>>                 What do you think?
>>
>>                 Should we also rearrange, e.g., indent the text after
>>                 Figure 2 such that
>>                 Packet sequencing, Duplicate elimination, Flow
>>                 replication, Flow merging, Packet encoding, and
>>                 Packet decoding get under Service layer
>>                 and
>>                 Congestion protection and Explicit routes get under
>>                 Transport layer?
>>
>>                     There’s a related paragraph of text between
>>                     Figures 3 and 4 in Section 4.1.2, but it doesn’t
>>                     provide useful intuition about which
>>                     functionality belongs in which layer.
>>
>>                     ** Editorial
>>
>>                     -- Section 2.1
>>
>>                     “expected” seems off in the definition of
>>                     reservation:
>>
>>                     reservation
>>
>>                     The set of resources allocated between a source
>>                     and one or
>>
>>                     more destinations through transit nodes and subnets
>>
>>                     associated with a DetNet flow, to provide the
>>                     expected DetNet
>>
>>                     Service.
>>
>>                     Suggest either “to provide the provisioned DetNet
>>                     Service to that flow”
>>
>>                 I like this one, will update to this one.
>>
>>                     or “to provide the specified DetNet Service to
>>                     that flow.”
>>
>>                     -- Section 3.1
>>
>>                        o  An upper bound on out-of-order packet
>>                     delivery.  It is worth
>>
>>                           noting that some DetNet applications are
>>                     unable to tolerate any
>>
>>                           out-of-order delivery.
>>
>>                     Is that a sequence bound or a time bound or
>>                     both?   I suspect that a sequence bound (maximum
>>                     degree of reordering in a flow, independent of
>>                     flow rate) was intended. An analogous
>>                     clarification would be helpful in section 3.2.2.1 .
>>
>>                 It is intentionally kept high level in the
>>                 architecture draft. Details are to be provided by the
>>                 flow information model draft. Please see my previous
>>                 mail:
>>                 https://mailarchive.ietf.org/arch/msg/detnet/AWG2eemg_AWsvF2FwtREyd_xtC8.
>>
>>                 */[David>] /*OK.
>>
>>                     -- Section 3.2.3
>>
>>                     I don’t understand “defined” in:
>>
>>                        Even the use of
>>
>>                        redundant paths through a network defined,
>>                     e.g., by [RFC6372] do not
>>
>>                        eliminate the chances of packet loss.
>>
>>                     Was “e.g., as defined by [RFC6372],” intended?
>>
>>                 Yes, this was the intention, will update to this one.
>>
>>                        Many real-time networks rely on physical rings
>>                     or chains of two-port
>>
>>                        devices, with a relatively simple ring control
>>                     protocol.
>>
>>                     How does a “ring control protocol” control
>>                     “chains”?  Suggest: “ring control protocol” ->
>>                     “control protocol”
>>
>>                     Also, are paired chains between common endpoints
>>                     intended, or a more general notion of chains?
>>
>>                 This text refers to typical factory deployment, which
>>                 is chain or ring.
>>                 It seems better to keep “ring control protocol”
>>                 because they are often very different from generic
>>                 control protocols applicable to mesh networks.
>>
>>                 Would flipping chain and ring resolve your concern?
>>
>>                    Many real-time networks rely on physical chains or
>>                 rings of two-port
>>
>>                    devices, with a relatively simple ring control
>>                 protocol.
>>
>>                     */[David>] /*It feels like “ring control
>>                     protocol” is an important phrase to retain.   In
>>                     the original text, would it be reasonable to add
>>                     “(applies to both rings and chains)” to the end
>>                     of the sentence?
>>
>>             Well, I guess the point is that there are many specific
>>             ring protocols, but we are looking for a generic solution.
>>             What about deleting "chains" from the sentence?
>>
>>                        Explicit routes can be established various ways,
>>
>>                     established various -> established in various
>>
>>                 OK.
>>
>>                        This is
>>
>>                        irrespective of the distribution method used,
>>                     also applies to service
>>
>>                        protection over explicit routes.
>>
>>                     used, also -> used, and also
>>
>>                 OK.
>>
>>                     -- Figure 5 (Section 4.1.3)
>>
>>                     The UNI acronym is introduced without expansion
>>                     or definition – please correct that, e.g., by
>>                     defining UNI in Section 2.1.
>>
>>                 DetNet-UNI is there among the definitions. It seems
>>                 enough to me.
>>
>>                 */[David>] /*That’s fine – I overlooked that
>>                 definition, sorry.
>>
>>                     -- Figure 9 (Section 4.7.2)
>>
>>                     I think I understand what’s going on, but the use
>>                     of “add/remove” in the figure should be explained
>>                     in associated text.
>>
>>                 What about updating the sentence above Figure 9 to:
>>                 A packet with corresponding Flow-IDs is illustrated
>>                 in Figure 9, which also indicates where Flow-ID can
>>                 be added or removed.
>>
>>                 */[David>] /*Sure, with one minor edit: “where
>>                 Flow-ID” -> “where each Flow-ID”
>>
>>             OK.
>>
>>                     Thanks, --David
>>
>>
>>                 Thank you!
>>                 Janos
>>
>>                     *From:*detnet [mailto:detnet-bounces@ietf.org]
>>                     *On Behalf Of *János Farkas
>>                     *Sent:* Thursday, June 28, 2018 9:09 PM
>>                     *To:* Lou Berger; Stewart Bryant; detnet@ietf.org
>>                     <mailto:detnet@ietf.org> >> DetNet WG
>>                     *Subject:* Re: [Detnet] WG Last Call:
>>                     draft-ietf-detnet-architecture-05
>>
>>                     Dear all,
>>
>>                     Off-line discussions among Lou, Stewart, and
>>                     authors followed the discussions to properly
>>                     address the WGLC comments, including the detailed
>>                     comments.
>>
>>                     A new revision of the draft has been uploaded:
>>                     draft-ietf-detnet-architecture-06.
>>
>>                     In addition to the changes already described in
>>                     this thread, the following bigger changes have
>>                     been made to the draft:
>>
>>
>>                     *Section 2.1 Terms used in this document*
>>
>>                     Some definitions refined as suggested by the
>>                     detailed comments
>>
>>                     New definitions have been added:
>>
>>                        "allocation
>>                                Resources are dedicated to support a
>>                     DetNet flow.  Depending
>>                                on an implementation, the resource may
>>                     be reused by non-
>>                                DetNet flows when it is not used by
>>                     the DetNet flow.
>>
>>
>>                        PEF     A Packet Elimination Function (PEF)
>>                     eliminates duplicate
>>                                copies of packets to prevent excess
>>                     packets flooding the
>>                                network or duplicate packets being
>>                     sent out of the DetNet
>>                                domain. PEF can be implemented by an
>>                     edge node, a relay
>>                                node, or an end system.
>>
>>                       PRF     A Packet Replication Function (PRF)
>>                     replicates DetNet flow
>>                                packets and forwards them to one or
>>                     more next hops in the
>>                                DetNet domain.  The number of packet
>>                     copies sent to each next
>>                                hop is a DetNet flow specific
>>                     parameter at the node doing the
>>                     replication.  PRF can be implemented by an edge
>>                     node, a relay
>>                                node, or an end system.
>>
>>                        PREOF   Collective name for Packet
>>                     Replication, Elimination, and
>>                                Ordering Functions.
>>
>>                        POF     A Packet Ordering Function (POF)
>>                     re-orders packets within a
>>                                DetNet flow that are received out of
>>                     order.  This function
>>                                can be implemented by an edge node, a
>>                     relay node, or an end
>>                                system.
>>
>>                       DetNet service proxy
>>                                Maps between App-flows and DetNet flows.
>>
>>                        bridged path
>>                                A VLAN bridge uses the VLAN ID and the
>>                     destination MAC
>>                                address to select the outbound port
>>                     hence the path for a
>>                                frame."
>>
>>
>>                     *Section 3.1 Primary goals defining the DetNet QoS*
>>
>>                     A new QoS aspect has been added:
>>                        "o  An upper bound on out-of-order packet
>>                     delivery.  It is worth
>>                           noting that some DetNet applications are
>>                     unable to tolerate any
>>                           out-of-order delivery."
>>
>>
>>                     The 3rd paragraph on loss on page 8 after the
>>                     bullet list has been extended to:
>>                        "After congestion, the most important
>>                     contributions to packet loss are
>>                        typically from random media errors and
>>                     equipment failures.  Service
>>                        protection is the name for the mechanisms used
>>                     by DetNet to address
>>                        these losses.  The mechanisms employed are
>>                     constrained by the
>>                        requirement to meet the users' latency
>>                     requirements.  Packet
>>                        replication and elimination (Section 3.2.2)
>>                     and packet encoding
>>                        (Section 3.2.2.3) are described in this
>>                     document to provide service
>>                        protection; others may be found.  For
>>                     instance, packet encoding can
>>                        be used to provide service protection against
>>                     random media errors,
>>                        packet replication and elimination can be used
>>                     to provide service
>>                        protection against equipment failures. This
>>                     mechanism distributes
>>                        the contents of DetNet flows over multiple
>>                     paths in time and/or
>>                        space, so that the loss of some of the paths
>>                     does need not cause the
>>                        loss of any packets."
>>
>>
>>                     *3.2.2.  Service Protection*
>>
>>                     Service protection is used as a more generic
>>                     term. Introductory text added:
>>                        "Service protection aims to mitigate or
>>                     eliminate packet loss due to
>>                        equipment failures, random media and/or memory
>>                     faults.  These types
>>                        of packet loss can be greatly reduced by
>>                     spreading the data over
>>                        multiple disjoint forwarding paths. Various
>>                     service protection
>>                        methods are described in [RFC6372], e.g., 1+1
>>                     linear protection.
>>                        This section describes the functional details
>>                     of an additional method
>>                        in Section 3.2.2.2, which can be implemented
>>                     as described in
>>                        Section 3.2.2.3 or as specified in
>>                     [I-D.ietf-detnet-dp-sol-mpls] in
>>                        order to provide 1+n hitless protection.  The
>>                     appropriate service
>>                        protection mechanism depends on the scenario
>>                     and the requirements."
>>
>>
>>                     New sub-section added:
>>
>>                     "3.2.2.1.  In-Order Delivery
>>
>>                        Out-of-order packet delivery can be a side
>>                     effect of service
>>                        protection. Packets delivered out-of-order
>>                     impact the amount of
>>                        buffering needed at the destination to
>>                     properly process the received
>>                        data.  Such packets also influence the jitter
>>                     of a flow.  The DetNet
>>                        service includes maximum allowed misordering
>>                     as a constraint.  Zero
>>                        misordering would be a valid service
>>                     constraint to reflect that the
>>                        end system(s) of the flow cannot tolerate any
>>                     out-of-order delivery.
>>                        Service protection may provide a mechanism to
>>                     support in-order
>>                        delivery."
>>
>>
>>                     *3.2.2.2. Packet Replication and Elimination*
>>
>>                     New bullet added as the last one:
>>                        "o  The Packet Ordering Function (POF) uses
>>                     the sequencing information
>>                           to re-order a DetNet flow's packets that
>>                     are received out of
>>                           order."
>>
>>                     New sentence added after the bullet list:
>>                     "The order in which a node applies the PEF and
>>                     the PRF to a DetNet
>>                     flow is implementation specific."
>>
>>                     2nd paragraph after the bullet list has been
>>                     updated to:
>>                     "Some service protection mechanisms rely on
>>                     switching from one flow to
>>                        another when a failure of a flow is detected. 
>>                     Contrarily, packet
>>                        replication and elimination combines the
>>                     DetNet member flows sent
>>                        along multiple different paths, and performs a
>>                     packet-by-packet
>>                        selection of which to discard, e.g., based on
>>                     sequencing information."
>>
>>
>>                     *3.2.3.  Explicit routes*
>>
>>                     Out-of-order aspect added to the first paragraph,
>>                     which is about distributed routing:
>>                     "Furthermore, out-of-order
>>                     packet delivery can be a side effect of route
>>                     changes."
>>
>>                     New sentence added to the 3rd paragraph:
>>                     "Explicit routes can be established various
>>                     ways, e.g., with RSVP-TE [RFC3209], with Segment
>>                     Routing (SR)
>>                     [I-D.ietf-spring-segment-routing], via a Software
>>                     Defined Networking
>>                     approach [RFC7426], with IS-IS [RFC7813], etc."
>>
>>                     New paragraph added:
>>                        "Out-of-order packet delivery can be a side
>>                     effect of distributing a
>>                        single flow over multiple paths especially
>>                     when there is a change
>>                        from one path to another when combining the
>>                     flow.  This is
>>                        irrespective of the distribution method used,
>>                     also applies to service
>>                        protection over explicit routes.  As described
>>                     in Section 3.2.2.1,
>>                        out-of-order packets influence the jitter of a
>>                     flow and impact the
>>                        amount of buffering needed to process the
>>                     data; therefore, DetNet
>>                        service includes maximum allowed misordering
>>                     as a constraint.  The
>>                        use of explicit routes helps to provide
>>                     in-order delivery because
>>                        there is no immediate route change with the
>>                     network topology, but the
>>                        changes are plannable as they are between the
>>                     different explicit
>>                        routes."
>>
>>                     *
>>                     4.1.1. Representative Protocol Stack Model*
>>
>>                     "Explicit routes" have been added to Figure 2
>>                     with the corresponding explanation:
>>                      "Explicit routes
>>                                The DetNet transport layer provides
>>                     mechanisms to ensure that
>>                                fixed paths are provided for DetNet
>>                     flows.  These explicit
>>                                paths avoid the impact of network
>>                     convergence."
>>
>>
>>                     Section 4.11 Connected islands vs. networks of
>>                     v05 has been deleted because it was just a
>>                     leftover from early drafts on what DetNet WG
>>                     should do; which are covered by the charter anyways.
>>
>>
>>                     References have been cleaned up and brought
>>                     up-to-date.
>>
>>
>>                     Refinements have been implemented in the draft
>>                     according to Lou's detailed comments. They are
>>                     not listed here because they are minor changes.
>>
>>
>>                     Best regards,
>>                     Janos
>>
>>                     On 6/12/2018 2:48 PM, Lou Berger wrote:
>>
>>
>>                         Balázs,
>>
>>                         Thanks for the response -- please see below.
>>
>>                         ----------
>>                         On June 12, 2018 4:07:35 AM Balázs Varga A
>>                         <balazs.a.varga@ericsson.com>
>>                         <mailto:balazs.a.varga@ericsson.com> wrote:
>>
>>                             Hi Lou, Thanks for the comments. See
>>                             reactions inline. Document update in
>>                             progress. Cheers Bala'zs
>>
>>                             -----Original Message-----
>>                             From: detnet <detnet-bounces@ietf.org>
>>                             <mailto:detnet-bounces@ietf.org> On
>>                             Behalf Of Lou Berger
>>                             Sent: 2018. június 1. 22:42
>>                             To: DetNet WG <detnet@ietf.org>
>>                             <mailto:detnet@ietf.org>;
>>                             draft-ietf-detnet-architecture@ietf.org
>>                             <mailto:draft-ietf-detnet-architecture@ietf.org>
>>
>>                             Subject: [Detnet] Promised comments on
>>                             draft-ietf-detnet-architecture
>>
>>                             Hi,
>>
>>                                  I have a number of high level
>>                             comments on the document that I'd like to
>>                              raise below.  I also have a number of
>>                             more editorial/specific comments that
>>                              I'd like to review directly with the
>>                             authors and then have them report back
>>                              on changes -- if any turn out to be more
>>                             substantive discussions from the
>>                              author's perspective, I'll raise these
>>                             on the list separately.
>>
>>                         ...
>>
>>
>>                             - WRT Section 4.4.3, I think the
>>                             inclusion of a distributed control plane
>>                             in the "Network Plane" is inconsistent
>>                             with other functional definitions and
>>                             conflates where a function resides from
>>                             the actual function and that whether
>>                             control is implemented in a fully
>>                             centralized, fully distributed or some
>>                             hybrid form doesn't fundamentally change 
>>                             the control function's role -- therefore
>>                             I think the sections 4..4.2 and .3 should
>>                             be revised accordingly
>>                             [Balázs Varga A] Agree in principal.
>>                             Let's discuss the details.
>>
>>                         Okay - I'll work with you off line and we can
>>                         report back the results/proposed changes.
>>
>>                             - In several places it's not clear that
>>                             DetNet service is always a L3 service
>>                             which is controlled using L3 identifiers,
>>                             i.e., IP addresses -- this is true even
>>                             in the MPLS service case and the TSN over
>>                             MPLS case. I think this is an important
>>                             point to be clear on in the document.
>>                             [Balázs Varga A] I am not sure. DetNet
>>                             service is always provided over a L3
>>                             network (IP or MPLS), that is fine.
>>                             However the service itself can be L2 or
>>                             L3. In case of TSN Ethernet frames are
>>                             transported, so it is a L2 service. In
>>                             case of IP end systems IP packets are
>>                             transported so it is a L3 service.
>>
>>
>>                         Humm - While I agree that DetNet is providing
>>                         an (enhanced) L2VPN service, it is not itself
>>                         providing control or service of L2 devices --
>>                         this is TSN's job. The fact that DetNet is
>>                         all about behavior of L3 nodes (i.e., IP and
>>                         PW/MPLS) and not L2 nodes (i.e., TSN bridges)
>>                         is something the architecture should make
>>                         unambiguous.
>>
>>                         Thanks,
>>                         Lou
>>
>>                             Please let me know what you think.
>>
>>                             Cheers,
>>
>>                             Lou
>>
>>
>>                             _______________________________________________
>>
>>                             detnet mailing list
>>                             detnet@ietf.org <mailto:detnet@ietf.org>
>>                             https://www.ietf.org/mailman/listinfo/detnet
>>                             _______________________________________________
>>
>>                             detnet mailing list
>>                             detnet@ietf.org <mailto:detnet@ietf.org>
>>                             https://www.ietf.org/mailman/listinfo/detnet
>>
>>
>>
>>                     On 6/12/2018 6:27 PM, Stewart Bryant wrote:
>>
>>                         Dear Bala'zs
>>
>>                         Thank you your for your consideration of
>>                         these points. I will just pick up a few that
>>                         need some further thought:
>>
>>                             DetNet transit node
>>
>>                             A node operating at the DetNet transport
>>                             layer, that utilizes
>>
>>                             link layer and/or network layer switching
>>                             across multiple
>>
>>                             links and/or sub-networks to provide
>>                             paths for DetNet service
>>
>>                             layer functions. Optionally provides
>>                             congestion protection
>>
>>                             over those paths.  An MPLS LSR is an
>>                             example of a DetNet
>>
>>                             transit node.
>>
>>                             SB> In that example it would have to be a
>>                             DetNet enable/aware LSR. An
>>
>>                             SB> ordinary LSR would not know anything
>>                             about DetNet.
>>
>>                             [Balázs Varga A] No, A DetNet aware LSR
>>                             would be a relay node (S-PE).
>>
>>
>>                         I think the confusion is what "DetNet
>>                         Transport Layer" means. This
>>                         technology touches on Transport Layer in  the
>>                         L4 sense, and the
>>                         Transport Network Layer as in the packet
>>                         network that carries
>>                         L3 packets.
>>
>>                         So I think that we need to clarify whether a
>>                         DetNet transit node
>>                         is an S-PE (i.e. a a transit node in the
>>                         DetNet layer), or a P node
>>                         (i.e. a transit node that is carrying DetNet
>>                         packets but could be
>>                         carrying any sort of MPLS packet)
>>
>>                             ============
>>
>>                             These three techniques can be applied
>>                             independently, giving eight
>>
>>                             possible combinations, including none (no
>>                             DetNet), although some
>>
>>                             combinations are of wider utility than
>>                             others. This separation keeps
>>
>>                             the protocol stack coherent and maximizes
>>                             interoperability with
>>
>>                             existing and developing standards in this
>>                             (IETF) and other Standards
>>
>>                             Development Organizations. Some examples
>>                             of typical expected
>>
>>                             combinations:
>>
>>                             o  Explicit routes plus service
>>                             protection are exactly the techniques
>>
>>                             employed by [HSR-PRP]. Explicit routes
>>                             are achieved by limiting
>>
>>                             the physical topology of the network, and
>>                             the sequentialization,
>>
>>                             replication, and duplicate elimination
>>                             are facilitated by packet
>>
>>                             tags added at the front or the end of
>>                             Ethernet frames.
>>
>>                             SB> ER can be done virtually as well as
>>                             physically. RSVP is a type of
>>
>>                             SB> ER, as is Adj-SID based SR, and we
>>                             can design other types.
>>
>>                             [Balázs Varga A] Agree, but these are
>>                             examples. Statement is for HSR-PRP.
>>
>>                         So the question is whether we should expand
>>                         the set of examples, particularly
>>                         to more accessible ones.
>>
>>                         ============
>>
>>                             Packet replication and elimination
>>
>>                             > > > > > > > > > relay > > > > > > > >
>>
>>                             > /------------+ R node E +------------\ >
>>
>>                             > / v + ^ \ >
>>
>>                             end    R + v | ^ + E end
>>
>>                             system + v | ^ +   system
>>
>>                             > \ v + ^ / >
>>
>>                             > \------------+ R relay E +-----------/ >
>>
>>                             > > > > > > > > > node > > > > > > > >
>>
>>                             Figure 1
>>
>>                             Packet replication and elimination does
>>                             not react to and correct
>>
>>                             failures; it is entirely passive.  Thus,
>>                             intermittent failures,
>>
>>                             SB> I think it copes with intermittent
>>                             failures OK.
>>
>>                             [Balázs Varga A] Yes, PRF and PEF can
>>                             eliminate the effect of such failures.
>>                             But text
>>
>>                             intends to say that it is passive. It is
>>                             not reacting to such failures. No change
>>                             in text.
>>
>>
>>                         You say that PREF does not correct failures.
>>                         I would contend that is exactly
>>                         what it does. Sure it does not react but it
>>                         does correct, and it does
>>                         address intermittent failures.
>>
>>                             ===========
>>
>>                             transported between the peer end systems.
>>                             Therefore, the following
>>
>>                             possible types / formats of a DetNet flow
>>                             are distinguished in this
>>
>>                             document:
>>
>>                             o  App-flow: native format of a DetNet
>>                             flow. It does not contain any
>>
>>                             DetNet related attributes.
>>
>>                             o DetNet-t-flow: specific format of a
>>                             DetNet flow.  Only requires
>>
>>                             the congestion / latency features
>>                             provided by the Detnet transport
>>
>>                             layer.
>>
>>                             o DetNet-s-flow: specific format of a
>>                             DetNet flow.  Only requires
>>
>>                             the replication/elimination feature
>>                             ensured by the DetNet service
>>
>>                             layer.
>>
>>                             o DetNet-st-flow: specific format of a
>>                             DetNet flow.  It requires
>>
>>                             both DetNet service layer and DetNet
>>                             transport layer functions
>>
>>                             during forwarding.
>>
>>                             SB> I find the relisting of these types
>>                             confusing. Wheren't they defined
>>
>>                             SB> in the section above?
>>
>>                             [Balázs Varga A] This is inline with the
>>                             previous section " Grouping of end systems ".
>>
>>                         Surely if we have defined them we never need
>>                         to do anything but name them in
>>                         later sections. Redefinition is never a good
>>                         idea because it often leads to
>>                         conflicting definitions.
>>
>>                             ============
>>
>>                             [HSR-PRP]  IEC, "High availability
>>                             seamless redundancy (HSR) is a
>>
>>                             further development of the PRP approach,
>>                             although HSR
>>
>>                             functions primarily as a protocol for
>>                             creating media
>>
>>                             redundancy while PRP, as described in the
>>                             previous
>>
>>                             section, creates network redundancy.  PRP
>>                             and HSR are both
>>
>>                             described in the IEC 62439 3 standard.",
>>
>>                             <http://webstore.iec.ch/webstore/webstore.nsf/
>>
>>                             artnum/046615!opendocument>.
>>
>>                             SB> Not available at the time of this
>>                             review, but my recollection is
>>
>>                             SB> that this is not readily available
>>                             without paying a large fee.
>>
>>
>>                         If we decide that this is essential as a key
>>                         reference, there needs to be
>>                         some suitable text, as this will get raised a
>>                         number of times between
>>                         here an publication as first the directorates
>>                         and then the ADs run
>>                         into this.
>>
>>                             ===========
>>
>>                             [ISA95] ANSI/ISA, "Enterprise-Control
>>                             System Integration Part 1:
>>
>>                             Models and Terminology", 2000,
>>
>>                             <https://www.isa.org/isa95/>.
>>
>>                             SB> Should that be 2000, or 2010.
>>
>>                             SB> Note that this seems to be a very
>>                             expensive document to access.
>>
>>                         You did not comment on the correctness of the
>>                         reference.
>>
>>
>>                         Best Regards
>>
>>                         Stewart
>>
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