Re: [Lsr] WG Adoption Call for "IGP Flexible Algorithms (Flex-Algorithm) In IP Networks" - draft-bonica-lsr-ip-flexalgo-01

Aijun Wang <wangaijun@tsinghua.org.cn> Thu, 03 December 2020 07:07 UTC

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From: "Aijun Wang" <wangaijun@tsinghua.org.cn>
To: "'Parag Kaneriya'" <pkaneria@juniper.net>, "'Acee Lindem \(acee\)'" <acee=40cisco.com@dmarc.ietf.org>, "'lsr'" <lsr@ietf.org>
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Subject: Re: [Lsr] WG Adoption Call for "IGP Flexible Algorithms (Flex-Algorithm) In IP Networks" - draft-bonica-lsr-ip-flexalgo-01
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Hello Parag:

 

From: Parag Kaneriya <pkaneria@juniper.net> 
Sent: Thursday, December 3, 2020 2:08 PM
To: Aijun Wang <wangaijun@tsinghua.org.cn>cn>; 'Acee Lindem (acee)'
<acee=40cisco.com@dmarc.ietf.org>rg>; 'lsr' <lsr@ietf.org>
Subject: RE: [Lsr] WG Adoption Call for "IGP Flexible Algorithms
(Flex-Algorithm) In IP Networks" - draft-bonica-lsr-ip-flexalgo-01

 

Hello Aijun,

 

Every router by default support algo 0.  When router support IP-FLEX algo
along with default algo, we need to be deterministic when there is conflict
of prefix advertise in both algo. This conflict might be due to mis config.
So when such condition arise, prefix belong to default algo should give
priority to be install in forwarding table. 

[WAJ] Why not prefer to the prefixes belong to the IP-FLEX?

And, let's consider its relation with BGP Prefixes. When the sub-topology
within the IP-FLEX is broken, because you don't support (BGP nexthop)
automatic fallback to the default algo,  traffic to these prefixes  that
advertised by the BGP will also be broken?

Is there any mechanism to support the automatic fallback from IP-FLEX to
default algo?   

 

Regards

Parag

 

Juniper Business Use Only

From: Lsr <lsr-bounces@ietf.org <mailto:lsr-bounces@ietf.org> > On Behalf Of
Aijun Wang
Sent: Thursday, December 3, 2020 7:02 AM
To: 'Acee Lindem (acee)' <acee=40cisco.com@dmarc.ietf.org
<mailto:acee=40cisco.com@dmarc.ietf.org> >; 'lsr' <lsr@ietf.org
<mailto:lsr@ietf.org> >
Subject: Re: [Lsr] WG Adoption Call for "IGP Flexible Algorithms
(Flex-Algorithm) In IP Networks" - draft-bonica-lsr-ip-flexalgo-01

 

[External Email. Be cautious of content]

 

Hi, authors:

 

Want to confirm one thing:

Does the mechanism described in this draft support the automatic fallback
from "flex algorithm" to the "traditional least-cost algorithm"?  

That is to say, can one prefix exists both in the "flex algorithm" table and
"traditional least-cost algorithm" table, the router prefer to forwarding
the packet based on the former table, and if not hit, then lookup the latter
table?

 

>From the context of the document, the answer seems not, or even on the
contrary?

In cases where a prefix advertisement is received in both a IPv4

   Prefix Reachability TLV and an IPv4 Algorithm Prefix Reachability

   TLV, the IPv4 Prefix Reachability advertisement MUST be preferred

   when installing entries in the forwarding plane.

 

If so, what the value to deploy such flexible algorithm within the network?
>From my POV, the reason that we want to deploy such mechanism is that we
want to differentiate the path(result of flex algorithm) of some traffic
from that(result of traditional least-cost algorithm) of most other normal
traffic.

 

Best Regards

 

Aijun Wang

China Telecom

 

From: lsr-bounces@ietf.org <mailto:lsr-bounces@ietf.org>
<lsr-bounces@ietf.org <mailto:lsr-bounces@ietf.org> > On Behalf Of Acee
Lindem (acee)
Sent: Wednesday, December 2, 2020 5:13 AM
To: lsr <lsr@ietf.org <mailto:lsr@ietf.org> >
Subject: [Lsr] WG Adoption Call for "IGP Flexible Algorithms
(Flex-Algorithm) In IP Networks" - draft-bonica-lsr-ip-flexalgo-01

 

This IP Flex Algorithm draft generated quite a bit of discussion on use
cases and deployment prior to IETF 109 and there was generally support for
WG adoption. This begins a two week WG adoption call. Please indicate your
support or objection to WG adoption on this list prior to 12:00 AM UTC on
December 16th, 2020. Also, review comments are certainly welcome.

Thanks,

Acee