[RPRWG] A problem with fairness messages

[Anoop Ghanwani <anoop@xxxxxxxxxxxxxx>]

In the current version of the draft, we have:
- Type A fairness messages that are propagated 
  hop-by-hop; and
- Type B fairness messages that are broadcast.

However, fairness messages do not contain 
a destination address, and the only thing that 
identifies them as fairness messages is the 
2-bit "Packet Type" value in the ring control
field.  This doesn't tell us whether the message 
is Type A or Type B; that is done by the fairness 
control header which is interpreted in the FCU.

This means that both Type A and Type B messages
must essentially be "dropped" (i.e. stripped)
from the ring and passed to the fairness control 
unit (FCU).  The FCU then discovers that the frame 
is a Type B message and "adds" it back to the ring.
This is not broadcast behavior from the standpoint 
of the RPR MAC.

There are two possible solutions for this problem:
1 - Introduce a destination MAC address in fairness
    messages; or
2 - Use two separate "Packet Type" values --
    one to indicate a Type A fairness message and 
    one to indicate Type B fairness message.

I personally prefer #1 and was going to put in
a comment with respect to that, but I thought I'd
share this with the list to see what others feel.

-Anoop
--
Anoop Ghanwani - Lantern Communications - 408-521-6707