Label_Set and Channel_Set in draft-ietf-ccamp-gmpls-dcsc-channel-ext-01.txt

[Remi Theillaud <remi.theillaud@marben-products.com>]

 One question about a Label_Set containing Channel_Set labels:

 Let's consider the following LABEL_SET object. Labels are assumed to 
be two bytes Generalized labels (type 2) - such as the EVPL Generalized 
Label format defined in draft-ietf-ccamp-gmpls-ether-svcs-03.txt.

  0                   1                   2                   3
  0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 |            Length             | Class-Num (36)|   C-Type (1)  |
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 |    Action(0)  |      Reserved     |        Label Type(4)      |
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 |    Action(2)  |Num Subchannels(2) |        Label Type(2)      |
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 |        Subchannel 1(100)      |        Subchannel 2(200)      |
 |-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 |    Action(2)  |Num Subchannels(2) |        Label Type(2)      |
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 |        Subchannel 1(300)      |        Subchannel 2(400)      |
 |-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

 I can see two different interpretation of this LABEL_SET:

1. This LABEL_SET specifies a single subchannel, which uses the format 
of a Channel_Set label.The Channel_Set label consists of two ranges: 
100..200 and 300..400.  The purpose of this LABEL_SET would be to force 
the downstream node to send back a LABEL object that consists of range 
100..200 AND range 300..400.

2. This LABEL_SET specifies two subchannels, both using the format of a 
Channel_Set label. The first channel is the range 100..200; the second 
one is the range 300..400. The purpose of this LABEL_SET would be to 
force the downstream node to send back a LABEL object that consists 
either of range 100..200 OR range 300..400

 Which interpretation is the correct one? am I misunderstanding something?

 One way to remove the ambiguity would be to consider that the 
LABEL_SET object can contain only one Channel_Set label (case 1 is then 
the correct interpretation). And it would be possible (if needed) to 
handle case 2 by using two LABEL_SET objects in a Path message.

 Rémi