Subject: RSVP-TE: specifying links in EROs

From: David Charlap <[email-masked]>
Date: Tue, 29 Nov 2005 11:56:16 -0500

I've been reading through RFCs 3209, 3473, and 3477.

I can't seem to find any mechanism that an originating node can use to 
fully specify both the nodes and links of an ERO.  All the discussion 
deals with abstract nodes, and doesn't say a thing about how to select 
specific links between the nodes.

Clearly, the chosen link must satisfy the LSP's constraints (QoS, CoS, 
link colors, etc.), but when there are multiple compatible links, the 
RFCs appear to be silent.

If an originating node wishes to fully specify the path through the 
network, down to the granularity of individual links, is there an 
RFC-specifie behavior that will allow this?

One can obviously build RSVP-TE with rules to permit this (such as 
selecting interfaces that exactly match ERO subobjects when there is a 
compatible match), but I can't find anything in the RFCs that discuss 
this.  They all merely state that the subobjects define abstract nodes 
(which may be a single router), but with no more granularity than that.

Surely, given the requirements and design goals of GMPLS, there must be 
a mechanism that I've missed.  Can anyone help?

-- David

---

From: David Charlap <[email-masked]>
Date: Tue, 29 Nov 2005 15:40:30 -0500

This is what I thought.  I also thought that using ERO subobjects with 
/32 addresses matching interface addresses would work.  But I can't find 
anything in the RFCs that documents this behavior.

I also thought the IF-ID subobject (used for unnumbered links) would 
work, but the RFC says otherwise.  It says only that the subobject can 
be used to define an abstract node via router-ID and IF-ID, and says 
that the actual ERO processing does not change from what was previously 
documented.

-- David

Don Fedyk wrote:
> Hi David
> 
> It was my impression that if you use numbered links, the ERO could
> specify the links as well. 
> 
> Don 
> 
> 
> 
> 
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