On Dec 12, 2012, at 4:27 PM, Peter Psenak wrote:

> Hi Hannes,
> 
> please see inline:
> 
> On 12.12.2012 15:49, Hannes Gredler wrote:
> 
>> 
>> for the OSPF routing protocol:
>> 
>> A PLR router should connect to the address
>> 
>>  traffic-engineering deployments:
> 
> why do we need to distinguish between TE and non-TE deployments?

for OSPF things are less ambiguous than for IS-IS, agreed.

for IS-IS  the advantage of TE extensions is really that it serves as an 
explicit identifier of a node,
if this router-ID has got IP reachability as well then its usually the 
transport IP address;
for OSPF we have the router-ID in every type-1 LSA for IS-IS we don't.

> All we need in rLFA context is a reachable IPv4 address advertised by PQ 
> node. That should be independent of TE being deployed or not.

by ensuring a deterministic address selection you safe T-LDP sessions:
if any source address can connect to any destination address then you have
doubled the overall number of T-LDP by two. however if you ensure that all nodes
agree to use a single IP address then you only need one T-LDP for
a given source/destination router pair.

> 
>>   - reported in the Router Address TLV  (Type 10 LSA) and
>>   - router (Type 1 LSA) ) stub network  advertisement and
>>   - the address mask is 255.255.255.255
>> 
>>     or
>> 
>>  non-traffic-engineering deployments:
>>   - reported in the  router-id field of the Type-1 LSA)
>>   - the router (Type 1 LSA) stub network  advertisement and
>>   - the address mask is 255.255.255.255
> 
> can we say that the PQ node address used for targeted LDP session is selected 
> in following order of preference:
> 
> 1. PQ node OSPF router-id, if it is advertised as /32 prefix by the PQ node 
> itself
> 
> 2. Highest /32 address advertised by PQ node in it's Router LSA

in favor of explicit advertisement, i'd rather do 3 rules here :

1. PQ node OSPF router-id, if it is advertised as /32 prefix by the PQ node 
itself
2. PQ node TE adress, if it is advertised as /32 prefix by the PQ node itself
3.  Highest /32 address advertised by PQ node in it's Router LSA

>> 
>> </added-text>
>> 
>> tx,
>> 
>> /hannes
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>> 
>> 
> 
> 
> 


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