[j-nsp] Setting CoS bits on ingress frames

[Victor Sudakov]

OK, there are some things I cannot grasp (below).

1. Any interface has a classifier (either a default or a user-defined
one) on ingress, which places a frame into a certain forwarding class. 

2. Any interface maps a forwarding class to an egress queue:

Physical interface: ge-0/0/23, Enabled, Physical link is Up
[dd]
  Egress queues: 8 supported, 4 in use
  Queue counters:       Queued packets  Transmitted packets
Dropped packets
    0 best-effort                    0            687779775 15
    1 assured-forw                   0              2038557 0
    5 expedited-fo                   0                    0 0
    7 network-cont                   0              1796789 0
  Queue number:         Mapped forwarding classes
    0                   best-effort
    1                   assured-forwarding
    5                   expedited-forwarding
    7                   network-control

3. On an ingress interface, I can classify e.g. Traffic_A as
expedited-forwarding and Traffic_B as best-effort.

4. On an egress interface, Traffic_A will leave the switch via 
Queue_5 and Traffic_B via Queue_0.

Is this correct so far? Then the questions are:

1. Is there an implicit rule that will mark Traffic_A with COS=011 and
Traffic_B with COS=000 because they are in different forwarding
classes ?  Or

2. Is an explicit rewrite rule always required for mapping forwarding
classes to code points on egress?

-- 
Victor Sudakov,  VAS4-RIPE, VAS47-RIPN
sip:sudakov at sibptus.tomsk.ru