Hi Jimmy,
On 13/10/2020 10:02, Dongjie (Jimmy) wrote:
Hi Peter,
Thanks for your reply. Please see further inline:
-----Original Message-----
From: Lsr [mailto:lsr-boun...@ietf.org] On Behalf Of Peter Psenak
Sent: Monday, October 12, 2020 4:39 PM
To: Dongjie (Jimmy) <jie.d...@huawei.com>; Ron Bonica
<rbon...@juniper.net>; Yingzhen Qu <yingzhen...@futurewei.com>; Gyan
Mishra <hayabusa...@gmail.com>
Cc: lsr@ietf.org; Jeff Tantsura <jefftant.i...@gmail.com>
Subject: Re: [Lsr] FW: New Version Notification for
draft-bonica-lsr-ip-flexalgo-00.txt
Hi Jimmy,
On 10/10/2020 05:05, Dongjie (Jimmy) wrote:
Hi Peter,
Thanks for your reply. It aligns with my understanding of FAD, which is just a
set of constraints for path computation. Thus one Flex-Algo ID could be used
with multiple different data planes. Is this understanding correct?
correct.
If so, my question is about the scenario below:
A group of nodes in a network support FA-128, a sub-group of them bind
FA-128 to SR SIDs, another sub-group of them bind FA-128 to IP address.
just to use the correct terminology, we should use "participate" instead of
"support".
Agree.
When one node compute an SR path to a destination, can it compute the path
to only pass the nodes which bind FA-128 to SR SIDs, and avoid the
nodes >which bind FA-128 to IP address? If so, how could this node know the
binding of FA to different data planes on other nodes?
again, it is the participation problem.
Nodes that participate in the SR Flex-algo 128 will advertise the participation
using the SR-Algorithm Sub-TLV. Only these nodes will be used during the SR
flex-algo computation for algo 128.
Nodes that participate in IP flex-algo 128 will advertise the participation
using
the IGP Algorithm Sub-TLV. Only these nodes will be used during the IP flex-algo
computation for algo 128.
Agree that if participation to Flex-Algo is advertised in a data plane specific
manner, then path computation with Flex-Algo constraints could be done only
using nodes which bind the Flex-Algo to the same data plane.
it's per app, not per data plane, but yes, that is what the base
flex-algo spec mandates.
As Robert asked and you confirmed, this implies each data plane needs to be
treated as an independent application of Flex-Algo. We have SR-Algorithm
sub-TLV and IP Algorithm sub-TLV, while there are actually more data planes to
be considered: SR-MPLS, SRv6, IPv4, IPv6, etc., does this mean that Flex-Algo
participation needs to be advertised for SR-MPLS, SRv6, IPv4, IPv6, etc.
separately?
yes, it needs to be advertised per app. We have SR specific algo
participation, we need one for IP as proposed in Ron's draft.
Regarding IPv4 vs IPv6, it's up to the authors whether they want to make
the participation for IP flex-algo topology specific or topology
independent, both could work.
Here's the text from the base flerx-algo draft:
10.2. Advertisement of Node Participation for Other Applications
This section describes considerations related to how other
applications can advertise their participation in a specific Flex-
Algorithm.
Application-specific Flex-Algorithm participation advertisements MAY
be topology specific or MAY be topology independent, depending on the
application itself.
Application-specific advertisement for Flex-Algorithm participation
MUST be defined for each application and is outside of the scope of
this document.
thanks,
Peter
Best regards,
Jie
thanks,
Peter
Best regards,
Jie
-----Original Message-----
From: Lsr [mailto:lsr-boun...@ietf.org] On Behalf Of Peter Psenak
Sent: Friday, October 9, 2020 11:58 PM
To: Dongjie (Jimmy) <jie.d...@huawei.com>; Ron Bonica
<rbonica=40juniper....@dmarc.ietf.org>; Yingzhen Qu
<yingzhen...@futurewei.com>; Gyan Mishra <hayabusa...@gmail.com>
Cc: lsr@ietf.org; Jeff Tantsura <jefftant.i...@gmail.com>
Subject: Re: [Lsr] FW: New Version Notification for
draft-bonica-lsr-ip-flexalgo-00.txt
Hi Jimmy,
On 09/10/2020 04:59, Dongjie (Jimmy) wrote:
Hi Ron,
Thanks for explaining the difference between IP Flex-Algo and SR
Flex-algo. As
you said, the major difference is the data plane.
If my understanding is correct, for one Flex-Algo to be used
correctly, the set
of nodes need to apply consistent constraints in computation, and
bind the FAD to the same data plane.
Is it possible that different nodes may use the same Flex-Algo with
different
data plane, e.g. some with SR-MPLS, some with SRv6, and some with
pure IP etc., or each Flex-Algo is always associated with only one
data plane? In the former case, should the flex-algo definition also
indicate the data plane(s) to be used with the flex-algo?
let me respond to this query, as this is not specific to Ron's draft.
FAD is data plane agnostic and is used by all of them.
thanks,
Peter
Best regards,
Jie
-----Original Message-----
From: Lsr [mailto:lsr-boun...@ietf.org] On Behalf Of Ron Bonica
Sent: Sunday, October 4, 2020 4:34 AM
To: Yingzhen Qu <yingzhen...@futurewei.com>; Peter Psenak
<ppse...@cisco.com>; Gyan Mishra <hayabusa...@gmail.com>
Cc: lsr@ietf.org; Jeff Tantsura <jefftant.i...@gmail.com>
Subject: Re: [Lsr] FW: New Version Notification for
draft-bonica-lsr-ip-flexalgo-00.txt
Hi Yingzhen,
IP Flexible Algorithms are like SR Flexible Algorithms in the
following
respects:
- Links have IGP metrics, TE metrics, delay metrics and
administrative colors
- FADs define Flexible Algorithms
More specifically, the FAD:
- Indicates which metric type the Flexible Algorithm uses
- Specifies constraints in terms of link colors that are included
or excluded from the Flexible Algorithm.
The significant difference between IP Flexible Algorithms and SR
Flexible Algorithms is:
- SR Flexible Algorithms bind FADs to prefix SIDs or SRv6 locators
- IP Flexible Algorithms bind FADs to IPv4 or IPv6 addresses.
So, IP Flexible Algorithms can be deployed in any IP network, even
in the absence of SR.
Ron
Juniper Business Use Only
-----Original Message-----
From: Yingzhen Qu <yingzhen...@futurewei.com>
Sent: Saturday, October 3, 2020 2:08 PM
To: Peter Psenak <ppse...@cisco.com>; Gyan Mishra
<hayabusa...@gmail.com>; Ron Bonica <rbon...@juniper.net>
Cc: lsr@ietf.org; Jeff Tantsura <jefftant.i...@gmail.com>
Subject: Re: [Lsr] FW: New Version Notification for
draft-bonica-lsr-ip-flexalgo-00.txt
[External Email. Be cautious of content]
Hi Peter,
Using flex-algo, a SRv6 locator can be associated with a single
algo, which means an IPv6 or IPv4 address can also be associated
with a single algo. So my understanding is Ron's proposal is making
the
configuration of flex-algo easier?
Instead of using the exclude or include list you can configure a
loopback address to a flex-algo directly?
Thanks,
Yingzhen
On 10/3/20, 2:47 AM, "Peter Psenak" <ppse...@cisco.com> wrote:
Hi Yingzhen,
On 02/10/2020 22:15, Yingzhen Qu wrote:
> Hi Peter,
>
> My understanding of flex-algo is that for traffic destined
to a prefix on a particular algo, it can only be routed on routers
belong to that algo, which also means only routers in that algo
calculates how to reach that prefix and install it into the routing
table. It seems to me that using flex-algo (section 12 of the
draft) it's possible to have a loopback address associated with
only one algo, please correct me if I'm missing or misunderstood
something.
you are right. That is exactly what is being done for flex-algo with
SRv6 - locator is associated with a single algo only. The proposal
uses
the same concept.
thanks,
Peter
>
> Thanks,
> Yingzhen
>
> On 10/2/20, 9:43 AM, "Lsr on behalf of Peter Psenak"
<lsr-boun...@ietf.org on behalf of
ppsenak=40cisco....@dmarc.ietf.org>
wrote:
>
> Gyan,
>
> On 02/10/2020 18:30, Gyan Mishra wrote:
> > All,
> >
> > With SRv6 and IP based flex algo a generic question as it
applies
to
> > both. Is it possible to have within a single IGP domain
different
sets
> > of nodes or segments of the network running different
algorithms.
>
> absolutely.
>
> > From
> > both drafts it sounds like all nodes have to agree on
same
algorithm
> > similar to concept of metric and reference bandwidth
all
have to
have
> > the same style metric and play to the same sheet of
music.
>
> all participating nodes need to agree on the definition of
the
flex-algo
> and advertise the participation. That's it.
>
> > If there was
> > a way to use multiple algorithms simultaneously based
on
SFC
or services
> > and instantiation of specific algorithm based on service
to
be
> > rendered. Doing so without causing a routing loop or
sub
optimal
> > routing.
>
> you can certainly use multiple algorithms simultaneously
and
use
algo
> specific paths to forward specific traffic over it. How that
is
done
> from the forwarding perspective depends in which
forwarding
plane you
> use. Flex-algo control plane is independent of the
forwarding
plane.
>
>
> >I thought with flex algo that there exists a feature that
on
> > each hop there is a way to specify which algo to use
hop by
hop
similar
> > to a hop by hop policy based routing.
>
> no, there is no hop-by-hop classification, that is
problematic
and
does
> not scale for high speeds. Classification is done at the
ingress only.
>
> thanks,
> Peter
>
> >
>
>
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