Hi Kim, When you are talking QOS labels, keep in mind layer 2 or layer 3. A layer 2 marking is only a 3 bit COS field when used on a trunk (802.1q or ISL) and a layer 3 (DSCP - 6 bit) remains intact from end to end. Once that 3 Bit COS field needs to be routed, the header is removed and COS is lost.
HTHs On May 26, 2010, at 2:18 PM, Kim Pedersen wrote: > Hi All, > > I was reading Joe's post on 3560 QoS and a question or two popped up. When > it comes to select an output queue, is it correctly understood, that you > depending on whether you used the trust CoS or trust DSCP, either the use the > output cos-map or dscp-map respectively? > > Also, in all cases, i assume that both a CoS (if applicable) and a DSCP > value, is generated from the QoS "label", which to me, seems to always be a > DSCP value? > > Trust CoS ingress: Look up in the CoS-To-DSCP map and generate the output > DSCP value from this, leave the CoS value untouched, base output-queue > assignment based on the cos-map. > > Trust DSCP ingress: Look up in the DSCP-DSCP mutation map and see if > anything needs changing, look up in the DSCP-to-CoS, to generate a CoS value, > and base the output queue on the DSCP value. > > Is this correct? > > Maybe, if incorect, you guys can sketch out a few examples on the flow from > ingress to egress. > > Thanks in advance! > > Sincerely, > Kim Pedersen > > // Freedom Matters > Follow my CCIE progress on: http://kpjungle.wordpress.com > > _______________________________________________ > For more information regarding industry leading CCIE Lab training, please > visit www.ipexpert.com _______________________________________________ For more information regarding industry leading CCIE Lab training, please visit www.ipexpert.com
