Hello,
Apologies for the delay in replying ...
comment #1 - You say "We need a new SID" - well please kindly confirm if
by this you really mean to say *"We need a new behaviour" *
question 1 - If this is what you are after it is not reflected in your
draft. Because currently in your draft you are actually defining a new
flavor and trying to stitch it to existing behaviours.
comment #2 - You are proposing 4 new behaviors effectively by adding new
flavor to combination of End.X behavior with existing flavors:
| TBA | TBA | End.X.PFC | [This ID] |
| TBA | TBA | End.X.PFC with PSP | [This ID] |
| TBA | TBA | End.X.PFC with USP | [This ID] |
| TBA | TBA | End.X.PFC with PSP & USP | [This ID |
question 2a - Why USD flavour is excluded ?
question 2b - Why End behaviour is excluded and you are only extending
End.X ?
comment #3 - You have defined upper-layer header processing ... well to the
best of my knowledge End.X behaviour does not process upper layer headers.
Quote from your draft which today defines flavours only for End.X:
S01. If (Upper-Layer header type == 143(Ethernet) ) {
S02. Remove the outer IPv6 header with all its extension headers
S03. If(Destination MAC==01-80-C2-00-00-01)
S04. Interface J will perform flow control actions based on the
content in the Priority - Flow Control (PFC) frames.
S05. } Else {
S06. Process as per Section 4.1.1 defined in [RFC8986]
S07. }
comment #4 - In pseudocode definition and in your text you are treating "J"
as interface ... well this is in RFC8986 a group of interfaces - subtle but
very important difference for scalability
comment #5 - In your example from section 3 you say:
"The segment list is {R1.End.X.PFC, R2.End, R3.End.X.PFC},"
question 3: Are you sure R2 should advertise End SID and not End.X SID ?
What happens if not all ingress interfaces on R3 (assuming more then one is
connected to R2) support PFC ?
To summarize if we keep adding flavors like proposed in your draft we will
very soon explode 32K of behaviours and flavors combinations.
So instead perhaps it makes sense to simply add a new SID behaviour say
End.PFC which would be used as adj-sid to meet your requirement of quote:
"Based on the original End.X SID, it incorporates additional meanings to
facilitate the identification of
interfaces in the network that possess the capability to handle
PFC packets."
What I was sort of questioning in my original note was however if you could
avoid all the hassle and simply put PFC indicator as Adj-SID function or
even function argument if hardware could handle it ?
Thx a lot,
Robert
On Fri, Jun 27, 2025 at 4:12 AM 阮征(联通集团本部) <[email protected]> wrote:
> Hi，
>
> Please see inline，
>
> Thanks，
>
> Zheng
> ------------------------------
> [email protected]
>
>
> *From:* Robert Raszuk <[email protected]>
> *Date:* 2025-06-26 18:18
> *To:* 阮征(联通集团本部) <[email protected]>
> *CC:* spring <[email protected]>; spring-chairs <[email protected]>
> *Subject:* [spring] Re: seek opinions on the draft
>
> 【本邮件为外部邮件，请注意核实发件人身份，并谨慎处理邮件内容中的链接及附件】
>
> Hi,
>
> (1) We need a new SID to advertise to the network or controller which
> interfaces in the current network have PFC processing capabilities (not all
> devices and interfaces support PFC),
>
> Why not use adj SID and add this as a part of the function ?
>
> ---In my view, this new SID is essentially an adjacency SID with special
> functionalities. Regarding your proposal to "add this as a part of the
> function", I haven't fully grasped your key point. Are you suggesting
> extending other fields of adj SID，such as Flavor? Could you elaborate on
> your suggestion in more detail?
>
> Thx,
> R.
>
>
> On Thu, Jun 26, 2025 at 3:45 AM 阮征(联通集团本部) <[email protected]> wrote:
>
>> Hi Robert，
>>
>> Thank you for your valuable comments，
>>
>> Please see inline,
>>
>> Thanks,
>>
>> Zheng
>>
>>
>> *From:* Robert Raszuk <[email protected]>
>> *Date:* 2025-06-24 18:45
>> *To:* 阮征(联通集团本部) <[email protected]>
>> *CC:* spring <[email protected]>; spring-chairs <[email protected]>
>> *Subject:* [spring] Re: seek opinions on the draft
>>
>> 【本邮件为外部邮件，请注意核实发件人身份，并谨慎处理邮件内容中的链接及附件】
>>
>> Hi,
>>
>> Pretty interesting idea however I have few basic questions:
>>
>> a) Why do you define a new SID type instead of using existing node or
>> adj SID and putting flow control as a SID function ? The entire idea of
>> network programming is not about adding more and more SID types ... it is
>> about inventing and adding network functions.
>>
>> There are two reasons for defining a new SID function:
>>
>> (1) We need a new SID to advertise to the network or controller which
>> interfaces in the current network have PFC processing capabilities (not all
>> devices and interfaces support PFC), and use this SID to guide the
>> controller and remote devices to establish reverse tunnels for carrying PFC
>> backpressure frames. However,existing SIDs do not have this functionality.
>> (2) When a device receives a packet with this SID as the destination
>> IPv6 address, it needs to perform special actions that are fundamentally
>> different from the functions of existing SIDs.
>>
>> b) If this is for WAN how do you assure all nodes on the path between src
>> and dst support PFC ? I assume by WAN you mean number of transit ASNs with
>> different IGPs and no BGP-LS NNI running. Or do you mean that such WAN
>> would always be under the same administrative domain ?
>>
>> Not all nodes need to support PFC. It only requires deploying SRv6
>> tunnels between PFC-capable nodes to carry backpressure signals. I believe
>> the current scope of this technology should be within a single AS, and
>> perhaps MAN scenarios are more applicable than WAN scenarios. Cross-AS
>> scenarios are much more complex, which we can consider in the future,
>> subject to the community's support for this solution.
>>
>> c) I recommend you add some OAM enhancements to indicate with
>> ping/traceroute that such support is there. Moreover I also would like to
>> see reporting of the state of the buffers with any already defined inband
>> OAM SR mechanism.
>>
>> We will consider adding OAM functionality to indicate the reachability of
>> this SID. In my original concept, buffer status is monitored by the device
>> itself, and when the buffer exceeds a set threshold, a backpressure signal
>> is sent upstream. Your idea is to use in-band OAM to carry buffer status
>> information, allowing upstream routers to proactively take flow control
>> actions based on this information, right? This is a highly insightful
>> suggestion.
>>
>>
>> d) Your proposal requires a lot of queues and buffers to be available on
>> each transit node. That's pretty expensive and sometimes harmful for real
>> time data where microseconds or less matters. Have you done any comparison
>> or educated simulations how would it compare with end-to-end ECN say using
>> DCTCP ? Wouldn't end to end not be more efficient if we are talking about
>> few WAN nodes under same administration ?
>>
>> Latency-sensitive services can continue to adopt traditional deployment
>> schemes, while loss-sensitive services or elephant flows prone to causing
>> network congestion can deploy this solution. In my view, end-to-end ECN
>> and the technology I proposed are technologies of different dimensions, and
>> they are not in a competitive relationship. These two technologies can be
>> deployed simultaneously to achieve higher data transmission efficiency.
>>
>>
>> Thx a lot,
>> Robert
>>
>>
>>
>>
>>
>>
>>
>> On Tue, Jun 24, 2025 at 6:13 AM 阮征(联通集团本部) <[email protected]> wrote:
>>
>>> Hello everyone,
>>>
>>> We have just submitted a new draft titled "Priority-based Flow Control
>>> SID in SRv6". The concept of this draft originates from cross-DC
>>> communication scenarios, aiming to achieve end-to-end flow control through
>>> coordination between WAN and data center networks by enhancing flow control
>>> capabilities of selected WAN devices, thereby reducing network packet loss.
>>>
>>> This document proposes a new End.X.PFC SID to identify network
>>> interfaces with PFC capabilities, enabling backpressure frames to be
>>> transmitted across hops via SRv6 tunnels.
>>>
>>> This technology can be leveraged to mitigate congestion and packet loss
>>> caused by micro-burst traffic in the network, with enhanced effectiveness
>>> in specific scenarios such as RDMA over WAN and elephant flow environments.
>>>
>>> Please review the draft in the following link:
>>>
>>>
>>> https://datatracker.ietf.org/doc/draft-ruan-spring-priority-flow-control-sid/
>>>
>>> Welcome any feedback and comments.
>>>
>>> Best Regards
>>>
>>> Ruanzheng on behalf of co-authors
>>>
>>> _______________________________________________
>>> spring mailing list -- [email protected]
>>> To unsubscribe send an email to [email protected]
>>>
>> _______________________________________________
>> spring mailing list -- [email protected]
>> To unsubscribe send an email to [email protected]
>>
> _______________________________________________
> spring mailing list -- [email protected]
> To unsubscribe send an email to [email protected]
>
_______________________________________________
spring mailing list -- [email protected]
To unsubscribe send an email to [email protected]
