Hi Bruno,
On 9/3/14 14:09 , [email protected] wrote:
Hi Peter,
From: Peter Psenak [mailto:[email protected]] > Sent: Wednesday, September 03,
2014 12:32 PM
Hi Bruno,
On 9/3/14 12:25 , [email protected] wrote:
Hi Peter, Rob,
+1 on Rob's comment regarding the use of admin tag for expressing
+operator policy (rather than spec/feature capability)
1 point in lined below
From: Peter Psenak > Sent: Wednesday, September 03, 2014 10:21 AM
Hi Rob,
On 9/3/14 10:16 , Rob Shakir wrote:
Hi Peter,
On 3 Sep 2014, at 09:13, Peter Psenak <[email protected]> wrote:
As per the above, I do not think that this mechanism replaces any
capability, it just gives an operator a means to be more granular
than the binary "supported"/"not supported" view that a flag
indicating capabilities does.
I understand. My point was that admin tags should not be used in
cases
where only a binary capability is signaled.
ACK, I completely agree. Perhaps we should add something into the
draft that the admin-tag should not be used for such a purpose.
I would certainly appreciate that.
I agree as a general rule. Yet IMHO we should not kill this possibility. In
particular for feature allowing incremental deployment & interaction with
non-compliant nodes.
One example would have been Remote LFA (RLFA):
- the PLR (FRR node) needs to be RLFA compliant. Therefore (potential)
communication between PLR regarding their capabilities can be done using
IANA/implemented code point.
- the PQ node (Merge Point) does not need to be RLFA compliant. And we
should keep this property to ease incremental deployment. Therefore
communication between PQ and PLR regarding PQ capabilities should/may
be done using node tag. RLFA spec could have defined an IANA registered
node tag to be used by PQ (configured by the network operator) to exclude
them as PQ candidate. e.g. for PQ node not accepting T-LDP session or nodes
which should not be used as PQ per policy.
why is "IANA registered node tag" any better then IANA registered capability
bit in the above case?
We need the value to be able to be set/cleared by configuration (by the network
operator) in order to allow for PQ node not compliant with RLFA to advertise it.
Node-admin tag clear matches this requirement.
I assumed that the capability bits were controlled by the software and not by
the network operator and hence could not be used. However, I realize that this
is an assumption that may be incorrect as I'm not familiar with OSPF
implementations (as we are mostly using ISIS). If all OSPF implementations
allow the network operator to control any bits (or at least the non
allocated/supported ones) I think I agree that such bit could equally be used.
However, after quickly reading the RFC, I'm not seeing that those bits
MUST/SHOULD be configurable by configuration. Hence we can't really guaranty
that any (future) implementation would allow this.
RFC4970 does not pose any restrictions on setting of a capability bits
in OSPF Router Informational Capabilities TLV. Some bits may be set
based on the software capabilities of the originator but others may be
set based on the configuration and willingness of the originator to
perform certain functionality. The flexibility is there.
thanks,
Peter
Thanks,
Bruno
thanks,
Peter
Thanks,
Bruno
thanks,
Peter
Cheers,
r.
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