On May 9, 2012, at 5:37 PM, Freek Dijkstra wrote:

On Labels:

What we have defined are "resource labels", eg.:
* Ethernet VLAN
* Ethernet I-SID
* Frequency on DWDM / Wavelength on CWDM
* ATM VPC
* ATM VPI
* SONET/SDH STS3c/STM/AUG-1 timeslot
* MPLS shim label
perhaps even:
* SSID on a wifi
* strand in a fiber bundle
* ...

This label is used for both:
* distinguishing between flows on a link (aka channels)
* routing and switching (eg. "switch X will forward data from port 1,
label 28 to port 4, label 42")

So far so good.
Now two issues.

1. On PortGroups:

I assume that each Port is associated with a particular label. This is
useful for monitoring, so we can distinguish between e.g. VLAN 120 and
VLAN 42.

For path finding, it seem useful to describe a all possible ports (e.g.
"all VLANs that can dynamically created". For this, I propose to
introduce a "PortGroup": which logically can be expanded to many
individual Ports.

The idea is still sketchy, but I like some input if this is a good
approach. If so, I'll make a proposal.

In the OSCARS world, we've done this, using the label terminology, as "the available labels on a port". Thus, a single port might have a variety of available labels that could be used on that port. That approach makes more sense to me than introducing a new grouping concept for ports that don't currently exist.

2. On Destination Labels

The "destination labels", such as destination IP address or destination
MAC address are also used for routing and switching, just like the
resource labels above.

Hence I presumed that destination labels could be described the same way
as resource labels.
I'm longer sure that this is a good idea.

Recall that each Port is associated with exactly one label.

For a host with one IP address 2001:0DB8:B4C6:6AAE::1 this means that is
has one ingress Port (for this IP address). On the other hand, it would
have 2^128-1 egress Ports (for all possible IP addresses that is can
send to).

This discrepancy between ingress Port and egress Ports seems odd to me,
and makes me doubt that destination labels are the same things as
resource labels.

As stated in my previous email, G.800 thinks it's a different beast: it
associates resource labels with the adaptation, while is associates
source- and destination labels with the termination.

That's all nice, but I'm still at loss how to describe source- and
destination labels in NML and how to deal with them. If you have any
idea (good or bad), please share it.

Freek
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