Hi Jimmy,
On 09/12/2020 13:52, Dongjie (Jimmy) wrote:
Hi Peter,
-----Original Message-----
From: Peter Psenak [mailto:[email protected]]
Sent: Wednesday, December 9, 2020 6:45 PM
To: Dongjie (Jimmy) <[email protected]>; Acee Lindem (acee)
<[email protected]>; lsr <[email protected]>
Subject: Re: [Lsr] WG Adoption Call for "IGP Flexible Algorithms
(Flex-Algorithm) In IP Networks" - draft-bonica-lsr-ip-flexalgo-01
Jimmy,
On 09/12/2020 11:10, Dongjie (Jimmy) wrote:
Hi authors,
Here is one comment following the previous discussion on the mail list
and the IETF meeting.
The IP Algorithm TLV is defined to advertise the IP Flex-Algorithm
participation information, there is no separate TLV for IPv4 or IPv6
Flex-Algo participation.
the draft clearly says:
"The IP Flex-Algorithm participation advertised in ISIS IP Algorithm
Sub-TLV is topology independent."
This does not answer my question.
Section 7 gives the rules of IP Flex-Algo Path calculation:
" IP Flex-Algorithm application only considers participating nodes during the
Flex-Algorithm calculation. When computing paths for a given Flex-Algorithm, all nodes
that do not advertise participation for IP Flex-Algorithm, as described in Section 5,
MUST be pruned from the topology."
From IP Algorithm TLV, one cannot tell whether a node participates in Flex-Algo
128 for IPv4, IPv6 or both. This would cause the problem described below: >
When one node uses IP Flex-Algo participation to compute a path for an IPv6
address advertised with Flex-Algo 128, it will not prune the nodes which
participate in Flex-Algo 128 for IPv4 only from the topology. Thus IPv6 packets
following that path may get dropped on nodes which participates in Flex-Algo
128 for IPv4 only.
FA calculation is done for every MT topology independently.
For IPv4 it will take all routers participating in MT0 and run the FA
calculation on top of MT0.
For IPv6 it will take all routers participating in MT2 and run the FA
calculation on top of MT2.
If some nodes participate in IPv4 Flex-Algo 128, and some of these
nodes participate in IPv6 Flex-Algo 128, how to ensure that the path
computed for IPv6 Flex-Algo will not use the nodes which only
participate in IPv4 Flex-Algo 128?
there is no such thing as "IPv4 Flex-Algo 128" or "IPv6 Flex-Algo 128".
There is only algo 128.
Agree that Flex-Algo 128 is application or data plane agnostic, and as we discussed the
same Flex-Algo can be used with both IPv4 and IPv6 (maybe also for SR-MPLS, SRv6). These
terms are used as shorthand of "Flex-Algo 128 used with IPv4 or IPv6"
You are mixing data plane support with algo participation.
I understand Flex-Algo definition is application agnostic, and Flex-Algo
participation is application specific, it is just not clear to me whether IPv4
and IPv6 can be treated as one application.
yes they can.
If you want an algo to only include nodes that supports specific data plane,
you would need to define a specific algo for it.
This IMO contradicts with the base concept: Flex-Algo definition is application
(or data plane) agnostic.
not really, see above.
thanks,
Peter
Best regards,
Jie
thanks,
Peter
Best regards,
Jie
*From:*Lsr [mailto:[email protected]] *On Behalf Of *Acee Lindem
(acee)
*Sent:* Wednesday, December 2, 2020 5:13 AM
*To:* lsr <[email protected]>
*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 16^th , 2020. Also, review comments are
certainly welcome.
Thanks,
Acee
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