Zhenqiang,
On 04/12/2020 05:26, [email protected] wrote:
Hello All,
I've read the draft and support its adoption. I have some comments as
follows.
1. I agree with Jeff that Flex Algo represents a sub- topology
consisting of the participating nodes, which we can also call a virtual
network. In this specific virtual network that the corresponding flex
algo calculation is applied.
2. For section three, why do we need one loopback address for
one Flex-Algorithm?
that's how you represent an algo specific path.
Can't we associate multiple Flex-Algorithms with one
loopback address, which means we want to reach the loopback address
through different paths?
no. You need some data-plane separation. In SR it's a SID, here, given
it's IP based, you need a separate IP prefix.
3. The second paragraph in section 3 does not describe Egress Node
Procedures. This paragraph should be put in a seperate section.
4. I want to know the path for a specific IP Flex-Algorithm is
calculated distributedly by each nodes paticipating this Flex-Algorithm
or calculated centralized by an controller?
it's a distributed calculation.
I wonder we can guarantee
the loop free path with IP Flex-Algorithm especially when the path is
calculated distributedly?
we MUST guarantee the consistency and it's done via FAD. Please look at
the original FA draft:
https://datatracker.ietf.org/doc/draft-ietf-lsr-flex-algo/
thanks,
Peter
Best Regards,
Zhenqiang Li
------------------------------------------------------------------------
[email protected]
*From:* Jeff Tantsura <mailto:[email protected]>
*Date:* 2020-12-04 09:18
*To:* Tony Li <mailto:[email protected]>; Robert Raszuk
<mailto:[email protected]>
*CC:* lsr <mailto:[email protected]>; Acee Lindem \(acee\)
<mailto:[email protected]>
*Subject:* Re: [Lsr] WG Adoption Call for "IGP Flexible Algorithms
(Flex-Algorithm) In IP Networks" - draft-bonica-lsr-ip-flexalgo-01
Anything else than IGP metric based SPT is considered TE. Looking
holistically - topology virtualization (or similar) could have been
a better name.
Cheers,
Jeff
On Dec 3, 2020, 4:25 PM -0800, Robert Raszuk <[email protected]>, wrote:
Hi Tony,
The moment I hit "Send" I knew that this response may be coming as
it really depends what is one's definition of TE.
If indeed IGP TE is anything more then SPF - then sure we can call
it a TE feature.
However, while a very useful and really cool proposal, my point is
to make sure this is not oversold - that's all.
Best,
R.
On Fri, Dec 4, 2020 at 1:13 AM Tony Li <[email protected]
<mailto:[email protected]>> wrote:
Hi Robert,
> However I really do not think that what Flexible Algorithm
offers can be compared or even called as Traffic Engineering
(MPLS or SR).
>
> Sure Flex Algo can accomplish in a very elegant way with
little cost multi topology routing but this is not full TE. It
can also direct traffic based on static or dynamic network
preferences (link colors, rtt drops etc ... ), but again it
is not taking into account load of the entire network and IMHO
has no way of accomplish TE level traffic distribution.
>
> Just to make sure the message here is proper.
It’s absolutely true that FlexAlgo (IP or SR) has limitations.
There’s no bandwidth reservation. There’s no dynamic load
balancing. No, it’s not a drop in replacement for RSVP. No, it
does not supplant SR-TE and a good controller. Etc., etc., etc….
However I don’t feel that it’s fair to say that FlexAlgo can’t
be called Traffic Engineering. After all TE is a very broad
topic. Everything that we’ve done that’s more sophisticated
than simple SPF falls in the area of Traffic Engineering.
Link coloring and SRLG alone clearly fall into that bucket.
I’ll grant you that it may not have the right TE features for
your application, but that doesn’t mean that it’s not
sufficient for some. Please don’t mislead people by saying
that it’s not Traffic Engineering.
Regards,
Tony
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