Shraddha,
added ISIS WG alias, as this is not specific to OSPF.
Please see inline:
On 12/17/14 06:43 , Shraddha Hegde wrote:
Peter,
Please see inline:
-----Original Message-----
From: Peter Psenak [mailto:ppse...@cisco.com]
Sent: Tuesday, December 16, 2014 11:36 PM
To: Shraddha Hegde; rob.sha...@bt.com;
draft-ietf-ospf-segment-routing-extensi...@tools.ietf.org
Cc: ospf@ietf.org
Subject: Re: draft-ietf-ospf-segment-routing-extensions-03
Hi Shraddha,
please see inline:
On 12/16/14 18:31 , Shraddha Hegde wrote:
Rob,
Pls see inline..
-----Original Message-----
From: rob.sha...@bt.com [mailto:rob.sha...@bt.com]
Sent: Tuesday, December 16, 2014 10:11 PM
To: Shraddha Hegde; ppse...@cisco.com;
draft-ietf-ospf-segment-routing-extensi...@tools.ietf.org
Cc: ospf@ietf.org
Subject: Re: draft-ietf-ospf-segment-routing-extensions-03
Shraddha,
Is it really up to the neighbor to specify what was previously a bundle?
<Shraddha> The graceful restart in OSPF as per RFC 3623 works by learning
the LSAs from neighbor after the restating router comes up and builds the LSA
database based on the learnt LSAs.
The neighbor relays back the LSA generated by the restarting
router. The Extended link LSA contains the adj-sid Label TLV which
Has the "s bit" set indicating the label is a set
label. If there are multiple such set labels associated with a link, its difficult to
associate which label was allocated for which bundle.
If there is a some kind of identifier for the
bundle, the label can be easily associated.
I don't think adding additional info to be distributed by the protocol is the
right way to address the local data persistence across restart/switch over. If
you need to make sure that the LSA contains the same data prior and after GR,
you can checkpoint them and restore from checkpoint after GR.
<Shraddha>I think if the protocol extensions are flexible enough, no
checkpointing would be required and everything can be recovered from the information
learnt from neighbor.
It is not only about "graceful restart", I find the
information to associate set label to a bundle missing. Think of an application which has
to look up the LSA database and build
An explicitly routed label stack using bundled labels. If there
are multiple adj-sid with "s bit set"originated by a node, it's not easy to
make a choice which set label to use!
Since there is no information about which label
corresponds to which bundle.
Let's imagine you have 4 links (l1, l2, l3, l4) between R1 and R2. You
split these to two sets on R1:
S1(l1,l2)
S1(l3,l4)
On R1, for links in S1 you advertise Adj-SID 10 and for link in S2 you
advertise Adj-SID 20.
Any router looking at advertisement from R1 can clearly see the two
sets. Am I missing something?
thanks,
Peter
I find the adj-sid set a very interesting and very
useful feature but find the OSPF/ISIS protocol extensions not flexible enough
to accommodate all the different ways
An operator may want to deploy bundles.
It is surely the local configuration of the node that determines what the
bundle is in the first place, and this is persistent over a graceful-restart of
the session?
<Shraddha> Yes, IMO local configuration decides which links belong to the
bundle. This configuration is persistent over graceful restart.
You MAY want to bundle all the parallel links
between two nodes into a bundle, in which case the existing protocol operations
work fine.
But I think protocol should provide flexibility to
make multiple bundles, able to assign a link to multiple bundles (if so
desired) and recovering the label across restart.
sure. If you need to make sure that same label is used prior and post GR, you
do not need protocol help for that.
thanks,
Peter
Thanks,
r.
[16/12/2014 16:34, "Shraddha Hegde" <shrad...@juniper.net>]
Peter,
An extended link LSA can contain multiple adj-sid labels with "s bit" set.
During graceful restart , when self generated LSAs are learnt from
neighbors, A handle is required to associate the set label with the
bundle.
I think a group-id field along with set label would serve the purpose.
Rgds
Shraddha
-----Original Message-----
From: Peter Psenak [mailto:ppse...@cisco.com]
Sent: Sunday, December 14, 2014 4:08 PM
To: Shraddha Hegde;
draft-ietf-ospf-segment-routing-extensi...@tools.ietf.org
Cc: OSPF WG List
Subject: Re: draft-ietf-ospf-segment-routing-extensions-03
Shraddha,
the idea is that you can assign the same Adj-SID to multiple links.
That way you can create multiple sets as you need.
thanks,
Peter
On 12/13/14 19:19 , Shraddha Hegde wrote:
Authors,
When there are multiple parallel links between two nodes,
it is useful to
Group them into different bundles and use each bundle for load-balancing
for different traffic flows.
What we have in adjacency sid is just a flag to indicate that the
label is a "set label" by setting a flag
In adj-sid TLV. It serves the purpose when all the parallel links
are in one bundle but not sufficient when
There can be different bundles and different labels for each of them.
An identifier for the group, probably "group-id" is needed to
associate the label with the interface group.
Any thoughts on this?
Rgds
Shraddha
.
.
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