XPost: comp.dcom.lans.ethernet   
   From: mark_cruzNOTFORSPAM@hotmail.com   
      
   Hello,   
      
   I'm trying to understand the expected behavior of a L2 switch with enabled   
   QoS and 802.1p mapping, i.e. cos 0 is mapped to queue 0, cos 1 to queue 1   
   and so on.   
      
   Consider example:  1G ports, pump traffic from port1 to port3 and from port2   
   to port3 at a maximum rate, as a result port3 is unable to sustain it; in   
   such case enabling priority mapping will prioritize one type of traffic over   
   another, does this mean that I will see high priority frames leaving the   
   egress port first, and then only low-priority packets, i.e. I will observe   
   packets re-ordering at the egress side?   
      
   To backup my reasoning, here is the example --  L2 switch with 4 queues (0   
   has the highest priority), maps COS values in such way:   
      
   p1 has cos7  -> q3   
   p2 has cos5  -> q2   
   p3 has cos3  -> q1   
   p4 has cos0  -> q0   
      
   p1,p2,p3,p4 --->[L2 switch with 802.1p mapping] -----> p4,p3,p2,p1   
      
   I believe this is correct when strict priority queuing is enabled. Is my   
   understanding of the priority mapping and switch's behavior correct?   
      
   Thanks in advance for comments !   
      
   Mark   
      
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