Re: Question regarding bi-directional connection set up - And Port-ID in Label object

[Yangguang Xu <xuyg@lucent.com>]

Eric, 

Please see my comments embedded:


>     I'm not sure that merging them is the right thing to do.
> They do not represent the same thing.  I believe the
> suggested label is the label the upstream would like the
> downstream to assign/recognize while the upstream label
> (I believe) is the label that the upstream _has_ assigned
> for the use of the downstream in a corresponding reverse
> LSP.
> 

I agree with your understanding. However, one of the key differences between
layer 1 transport network and IP network is data traffic direction is not
related to connection creation direction in transport network.

For example,  A----B----.....----F----G
(1) A uni-directional (user-traffic from A-->G) light path can be initiated
either by A or G
(2) So does a bi-directional light path

So, in layer 1 transport network, downstream/upstream is according to signaling
direction in control plane. It should have nothing to do with user plane
traffic.

Suggested label, upstream label ... are used to specify which trib to use for
light path. What we need to have is directionality attribute for label.

>     There are two problems with trying to force the two to
> be the same:
> 
> o    one is being assigned and the other is being requested
>       (assignment may not occur as requested), and

In layer 1 transport network, label is bound to certain physical resource.

Upstream label is only useful for a bi-directional LSP in a network where ports
are uni-directionally identified.

If all ports are uni-directional, this shouldn't happen. Label should
directionality attribute. 


> o    it is not always the case that the same label can be
>       assigned, in both directions, and associated with the
>       two halves of the same bi-directional LSP.
> 

Directionality should be one attribute for "bundling". Transmit ports, receive
ports and bi-directional ports can be assigned to different bundles, with unique
bundle ID.

Source node should choose the correct bundle ID for the connection it desires.

Regards,

Yangguang