[CC’ed IS-IS wg too]
Regarding the following discussions at last IETF and the corresponding modified text in
regarding the same I have the following question to authors -
- Targeted LDP Address
- Advertise in protocol. This is preferred. However,
some boxes don't advertise.
[Uma]: I think this was mentioned because it’s been said non-TE participating/legacy nodes won’t advertise this.
- Management configuration as a requirement.
- Pick an address arbitrarily.
Uma: What configuration is expected?
Stewart: Could be silent since it is a vendor
Hannes: Lowest IP address is useless. A node should
be able to advertise that it doesn't support
Rob Shakir - Draft should not remain silent on this
Stewart: Use Router-ID if not configured to do otherwise
like using a different address.
The text now says:
In the absence of a protocol to learn the preferred IP address for targeted LDP, an LSR should attempt a targeted LDP session with the Router ID [RFC2328] [RFC5305] [RFC5340], unless it is configured otherwise.
[Uma]: ..then the above text can be potentially conflicting to what is stated in Section 12 –
“To prevent their use as an attack vector the repair tunnel endpoints
SHOULD be assigned from a set of addresses that are not reachable
from outside the routing domain.”
If a new private IP address range is provisioned for T-LDP then it may not be possible to indicate the same as RID with multiple loopbacks.
I feel the text around this should not be rigid based on this and this is can still present a potential interoperability issue for RLFA..
This can be addressed by defining auxiliary RIDs TLV (or sub-TLV in TLV 242) specifying the purpose of the RID, in this case for RLFA T-LDP session.
With this –
a. One need not dip into all reachability prefixes 135/235/236/237 to find the prefix tags
b. Also need not get confused if the tag is present because of inter area leaking etc..
We had a small offline discussion on this and welcome others view on this too.