Re: [Lsr] New Version Notification for draft-bonica-lsr-ip-flexalgo-00.txt

["Dongjie (Jimmy)" <[e-mail]>]

Hi,

While it is possible to define algorithm-specific IP reachability TLVs to advertise IP Prefixes associated with different algorithms, this would introduce several new IS-IS top TLVs. One quick question is: can similar function be provided with extensions to existing IP reachability TLVs and MT IP reachability TLVs, instead of defining top TLVs for MT, Flex-Algo, and the combination of Flex-Algo and MT respectively?

And one nit in the encoding: the length of MT-ID in IS-IS should be 12 bits.

Best regards,
Jie

From: Lsr [mailto:[e-mail]] On Behalf Of Robert Raszuk
Sent: Wednesday, September 30, 2020 3:28 PM
To: Huzhibo <[e-mail]<mailto:[e-mail]>>
Cc: [e-mail]<mailto:[e-mail]>; Joel M. Halpern <[e-mail]<mailto:[e-mail]>>
Subject: Re: [Lsr] New Version Notification for draft-bonica-lsr-ip-flexalgo-00.txt

Hi,

> It uses the HBH option

Currently Ron's proposal seems to work well for both IPv4 and IPv6 addresses. I hope this discussion will not try to derail it to IPv6 only track.

I see no issue with loopback to flexible algorithm mapping in 1:1 fashion.

I do however see some issues in deploying such technology as it will only work well if *all* nodes in the network support this new functionality. In contrast in SR world or control plane based TE I proposed or any encapsulation based proposal only anchor nodes need to support the new functionality while rest of the network does not need to be even aware about it.

Many thx,
R.


On Wed, Sep 30, 2020 at 6:10 AM Huzhibo <[e-mail]<mailto:[e-mail]>> wrote:
Hi Joel:

    For details about the method defined in RFC 6550. It uses the HBH option to carry the RPLInstaceID. The RPLInstaceID and FlexAlgoID are similar.

Thanks

Zhibo

-----Original Message-----
From: Lsr [mailto:[e-mail]<mailto:[e-mail]>] On Behalf Of Joel M. Halpern
Sent: Wednesday, September 30, 2020 12:05 PM
Cc: [e-mail]<mailto:[e-mail]>
Subject: Re: [Lsr] New Version Notification for draft-bonica-lsr-ip-flexalgo-00.txt

I am missing something in this discussion of multiple algorithms.

My understanding of flex-algo whether for MPLS, SRv6, SRH, or IPv6, is that you need to associated a forwarding label (e.g. MPLS label or IPv6
address) with a specific algorithm so that you can compute the next hope for the forwarding label using the proper algorithm.  Then when a packet arrives, it is simply forwarded according to the forwarding table (e.g.
FIB, LIB, ..)

If that is so, then I do not understand how a given prefix can be safely associated with more than one algorithm.  I could imagine doing several calculations according to different algorithms.  But how do you decide which one applies to the packet?  As far as I know, flex-algo does not look at the QoS/CoS/ToS bits.

Yours,
Joel

PS: I will admit that it took until  an operator described some "interesting" constraints before I understood why one would even do this.

On 9/29/2020 11:50 PM, Huzhibo wrote:
> Hi.
>
> Associating multiple algorithms with a given prefix is an interesting topic, and I think this can simplify the complexity of FlexAlgo. I wonder if the author would consider using cases with multiple algorithms with a given prefix.
>
> Thanks
>
> ZHibo
>
> -----Original Message-----
> From: Lsr [mailto:[e-mail]<mailto:[e-mail]>] On Behalf Of [e-mail]<mailto:[e-mail]>
> Sent: Tuesday, September 29, 2020 10:05 PM
> To: Ron Bonica <rbonica=[e-mail]<mailto:[e-mail]>>
> Cc: [e-mail]<mailto:[e-mail]>
> Subject: Re: [Lsr] New Version Notification for
> draft-bonica-lsr-ip-flexalgo-00.txt
>
>
> Ron,
>
> This is nice. It makes it clear that constraint based path computation need not have MPLS overhead for those that don’t want it.
>
> One thing that you don’t talk about is how this gets used, tho that may be blindingly obvious: you’ll need all nodes placing their prefixes in the RIB/FIB, where it will need to be selected over other path computation for the same prefixes.  This somewhat precludes the possibility of a given prefix being useful in multiple flex-algos.
>
> More text on application would be most welcome, just to ensure that we’re on the same page.
>
> Tony
>
>
>> On Sep 29, 2020, at 6:37 AM, Ron Bonica <rbonica=[e-mail]<mailto:[e-mail]>> wrote:
>>
>>
>> Please review and comment
>>
>>                                        Ron
>>
>>
>>
>> Juniper Business Use Only
>>
>>> -----Original Message-----
>>> From: [e-mail]<mailto:[e-mail]> <[e-mail]<mailto:[e-mail]>>
>>> Sent: Tuesday, September 29, 2020 9:36 AM
>>> To: Parag Kaneriya <[e-mail]<mailto:[e-mail]>>; Shraddha Hegde
>>> <[e-mail]<mailto:[e-mail]>>; Ron Bonica <[e-mail]<mailto:[e-mail]>>; Rajesh M
>>> <[e-mail]<mailto:[e-mail]>>; William Britto A J <[e-mail]<mailto:[e-mail]>>
>>> Subject: New Version Notification for
>>> draft-bonica-lsr-ip-flexalgo-00.txt
>>>
>>> [External Email. Be cautious of content]
>>>
>>>
>>> A new version of I-D, draft-bonica-lsr-ip-flexalgo-00.txt
>>> has been successfully submitted by Ron Bonica and posted to the IETF
>>> repository.
>>>
>>> Name:           draft-bonica-lsr-ip-flexalgo
>>> Revision:       00
>>> Title:          IGP Flexible Algorithms (Flexalgo) In IP Networks
>>> Document date:  2020-09-29
>>> Group:          Individual Submission
>>> Pages:          14
>>> URL:            https://urldefense.com/v3/__https://www.ietf.org/id/draft-bonica-<https://urldefense.com/v3/__https:/www.ietf.org/id/draft-bonica->
>>> lsr-ip-flexalgo-00.txt__;!!NEt6yMaO-gk!X7PVDP-
>>> FnUA0oCcZMw3Qde6in0C72hu_9hOZ53kPspIarR8fNDyU9Vck80Zbjoij$
>>> Status:
>>> https://urldefense.com/v3/__https://datatracker.ietf.org/doc/draft-b<https://urldefense.com/v3/__https:/datatracker.ietf.org/doc/draft-b>
>>> o
>>> nica-lsr-
>>> ip-flexalgo/__;!!NEt6yMaO-gk!X7PVDP-
>>> FnUA0oCcZMw3Qde6in0C72hu_9hOZ53kPspIarR8fNDyU9Vck8x7e5ZqI$
>>> Htmlized:
>>> https://urldefense.com/v3/__https://datatracker.ietf.org/doc/html/dr<https://urldefense.com/v3/__https:/datatracker.ietf.org/doc/html/dr>
>>> a
>>> ft-
>>> bonica-lsr-ip-flexalgo__;!!NEt6yMaO-gk!X7PVDP-
>>> FnUA0oCcZMw3Qde6in0C72hu_9hOZ53kPspIarR8fNDyU9Vck82w_6CyU$
>>> Htmlized:       https://urldefense.com/v3/__https://tools.ietf.org/html/draft-<https://urldefense.com/v3/__https:/tools.ietf.org/html/draft->
>>> bonica-lsr-ip-flexalgo-00__;!!NEt6yMaO-gk!X7PVDP-
>>> FnUA0oCcZMw3Qde6in0C72hu_9hOZ53kPspIarR8fNDyU9Vck81_QrJ_p$
>>>
>>>
>>> Abstract:
>>>    An IGP Flexible Algorithm computes a constraint-based path and maps
>>>    that path to an identifier.  As currently defined, Flexalgo can only
>>>    map the paths that it computes to Segment Routing (SR) identifiers.
>>>    Therefore, Flexalgo cannot be deployed in the absence of SR.
>>>
>>>    This document extends Flexalgo, so that it can map the paths that it
>>>    computes to IP addresses.  This allows Flexalgo to be deployed in any
>>>    IP network, even in the absence of SR.
>>>
>>>
>>>
>>>
>>> Please note that it may take a couple of minutes from the time of
>>> submission until the htmlized version and diff are available at tools.ietf.org<http://tools.ietf.org>.
>>>
>>> The IETF Secretariat
>>>
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