[rbridge] Proposed replacement for a paragraph in section 2.3 of draft-ietf-trill-rbridge-protocol-07

[Claudio DeSanti]

Hi all,

as just presented, this is a proposed clarification for an existing 
paragraph in section 2.3 of the base protocol spec.
Thanks,

              Claudio.

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Existing paragraph:

   By default, RBridges tag IS-IS Hellos with VLAN 1. However, an
   RBridge MAY be configured to transmit Hellos on a set of VLANs, and
   if elected DRB, to designate to the other RBridges on the link which
   VLAN to tag Hellos with. Once the DRB, say RB1, is elected, and
   specifies the designated VLAN, say VLAN-x, on which to send Hellos,
   (1) all RBridges on the link, except the DRB, transmit Hellos tagged
   only with VLAN-x, (2) all RBridge-RBridge communication (including
   Hellos, forwarded data packets, and LSPs) are tagged with VLAN-x, and
   (3) the DRB only lists, in its Hello, and in the pseudonode LSP, the
   set of RBridges from which the DRB hears VLAN-V tagged packets.


Proposed replacement:


An RBridge maintains per each port the following parameters:
a) Announcing VLANs set: the set of VLANs where an RBridge port 
announces IS-IS Hellos on a link;
b) Designated VLAN: the VLAN used by an RBridge port to communicate with 
other RBridge ports on a link; and
c) Forwarding VLANs set: the set of VLANs for which an RBridge port is 
appointed VLAN forwarder on a link.

By default the Announcing VLANs set contains all the VLANs active on the 
port, however it may be configured to contain a subset of them.

When a port of an RBridge becomes operational, the RBridge MUST transmit 
IS-IS Hellos on each VLAN of the Announcing VLANs set of that port.

If the RBridge is elected DRB for the link to which that port is 
connected, the RBridge MUST:
a) continue to send IS-IS Hellos per each VLAN of the Announcing VLANs 
set of that port;
b) designate the Designated VLAN to be used to communicate with the 
other RBridges connected to that link; and
c) establish the Forwarding VLANs set per each RBridge connected to that 
link, including itself.

If the RBridge is not elected DRB for the link to which that port is 
connected and its Forwarding VLANs set is not empty, the RBridge MUST:
a) learn from the DRB the Designated VLAN on that link;
b) act as a VLAN forwarder for the VLANs included in its Forwarding 
VLANs set; and
c) transmit IS-IS Hellos messages only on the Designated VLAN and on the 
VLANs of its Forwarding VLANs set.

If the RBridge is not elected DRB for the link to which that port is 
connected and its Forwarding VLANS set is empty, the RBridge MUST:
a) learn from the DRB the Designated VLAN on that link; and
b) transmit IS-IS Hellos messages only on the Designated VLAN.